Forecast Discussions mentioning any of
"HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 12/20/13
AREA FORECAST DISCUSSION
NWS PHOENIX AZ
905 PM MST THU DEC 19 2013
.SYNOPSIS...
A DEEP LOW PRESSURE SYSTEM APPROACHING THE DESERT SOUTHWEST WILL
BRING INCREASING CLOUDS AND GOOD CHANCES FOR RAIN ACROSS MUCH OF THE
REGION BY LATE THIS EVENING. PERIODS OF RAIN WILL PERSIST ACROSS
SOUTH-CENTRAL ARIZONA THROUGH FRIDAY MORNING BEFORE TAPERING OFF
FROM WEST TO EAST BY FRIDAY AFTERNOON. A LINGERING CHANCE OF SHOWERS
MAY CONTINUE OVER HIGHER TERRAIN LOCATIONS INTO SATURDAY AFTERNOON.
THE SYSTEM WILL ALSO BRING MUCH COOLER TEMPERATURES...GENERALLY
BELOW THE SEASONAL AVERAGE HEADING INTO THE WEEKEND. EXPECT DRY
CONDITIONS WITH A SLOW WARMING TREND DURING THE FIRST HALF OF NEXT
WEEK.
&&
.DISCUSSION...
THIS EVENING BROUGHT SCATTERED SHOWERS TO MUCH OF SOUTH-CENTRAL
ARIZONA...AND TO A MUCH LESSER EXTENT TO SOUTHEAST CA AND SOUTHWEST
AZ AS A PLUME OF DEEP MID-LEVEL MOISTURE SURGED NORTHWARD OVER THE
REGION AHEAD OF THE MAIN UPPER LOW CENTER THAT IS NOW JUST OFF THE
SOUTHERN CA COAST. RAINFALL ACCUMULATIONS SO FAR HAVE BEEN QUITE
SPOTTY...WITH PHOENIX SHY HARBOR RECEIVING 0.16 OF AN INCH...BUT
MANY PARTS OF THE EAST VALLEY...AND THE WESTSIDE NOT SEEING ANY RAIN
AT ALL. AS FAR AS SOUTHWEST AZ AND SOUTHEAST CA ARE CONCERNED...MOST
LOCATIONS HAVE STAYED COMPLETELY DRY SO FAR...WITH JUST A FEW
REPORTS OF TRACE AMOUNTS OF RAIN...SUCH AS IMPERIAL COUNTY AIRPORT.
THE LATEST HRRR HIGH RES MODEL IS INDICATING THAT A BREAK IN THE
RAINFALL...WHICH STARTED IN THE LAST HOUR OR SO...WILL CONTINUE
UNTIL AROUND MIDNIGHT...WITH SHOWERS REDEVELOPING AFTER MIDNIGHT AS
ANOTHER PLUME OF DEEPER MOISTURE/SHOWERS THAT IS NOW OVER NORTHERN
BAJA/EXTREME SOUTHWEST AZ MOVES NORTHEASTWARD INTO SOUTHCENTRAL AZ.
IT STILL APPEARS THE BEST CHANCES FOR SIGNIFICANT RAINFALL...AND
CHANCES FOR ISOLATED THUNDERSTORMS WILL OCCUR LATER TONIGHT AND
EARLY FRIDAY...WHEN THE BEST MOISTURE/DYNAMICS MOVE OVER
SOUTH-CENTRAL ARIZONA. GIVEN CURRENT TRENDS AND MODEL
FORECASTS...OUR SHORT-TERM PRODUCTS ARE STILL LOOKING GOOD...AND NO
UPDATES ARE PLANNED AT THIS TIME.
&&
.PREVIOUS DISCUSSION...
THE DEEP UPPER LOW TRACKING ALONG THE CALIFORNIA COAST HAS REACHED
POINT CONCEPTION AS OF EARLY THIS AFTERNOON WITH A PLUME OF MOISTURE
EVIDENT ON WATER VAPOR IMAGERY NOW STRETCHING INTO ARIZONA. SINCE
AROUND NOON...A FIELD OF ALTOCUMULUS CAN ALSO BE SEEN STRETCHING
SOUTH TO NORTH BETWEEN YUMA AND PHOENIX. WE COULD SEE A FEW LIGHT
SHOWERS DEVELOP OUT OF THIS AREA LATE THIS AFTERNOON BEFORE
BLOSSOMING ACROSS SOUTH-CENTRAL ARIZONA THIS EVENING. ALSO IN THE
NEAR-TERM...WINDY CONDITIONS WILL CONTINUE FOR A FEW MORE HOURS
ACROSS THE IMPERIAL VALLEY AND ACROSS OPEN DESERT AREAS SOUTH OF
PHOENIX. WIND GUSTS ACROSS PINAL AND SOUTHERN MARICOPA COUNTIES
SINCE 18Z HAVE REACHED 30 MPH WHICH HAS BEEN ENOUGH TO CAUSE SOME
LOCALIZED AREAS OF BLOWING DUST BETWEEN CASE GRANDE AND ELOY IN
CENTRAL PINAL. NOT EXPECTING WIDESPREAD BLOWING DUST THIS
AFTERNOON...BUT HAVE INCORPORATED SOME BLOWING DUST IN THE FORECAST
ACROSS NORTHWEST PINAL COUNTY.
NOW THAT THE MODELS FINALLY HAVE A BETTER IDEA ON THE MOISTURE
AVAILABILITY WITH THIS SYSTEM...EXPECTING THIS TO END UP BEING A
WIDESPREAD LIGHT TO MODERATE RAINFALL EVENT ACROSS SOUTHERN ARIZONA
WITH MORE SPARSE SHOWER COVERAGE ACROSS SOUTHEAST CALIFORNIA. AS THE
UPPER LOW TRACKS JUST TO OUR SOUTHWEST TONIGHT...STRONG SOUTHERLY
FLOW WILL CONTINUE TO TRANSPORT MOISTURE INTO SOUTH-CENTRAL
ARIZONA...INCREASING PWATS TO AROUND 0.75 INCHES. WITH THE OVERALL
MODEL CONSENSUS OF A WETTER SYSTEM...SHOULD EXPECT OFF AND ON BANDS
OF RAIN SHOWERS FROM JUST EAST OF THE CA/AZ STATE LINE EASTWARD
THROUGH THE PHOENIX METROPOLITAN AREA STARTING SHORTLY BEFORE
MIDNIGHT AND LASTING THROUGH AROUND NOON FRIDAY. QPF AMOUNTS HAVE
BEEN RAISED SLIGHTLY WITH A TOTAL RAINFALL FOR THE EVENT OF LESS
THAN A QUARTER OF AN INCH ACROSS SOUTHEAST CALIFORNIA AND EXTREME
SOUTHWEST ARIZONA TO A BIT OVER A HALF AN INCH ACROSS PHOENIX. AS
THE UPPER COLD CORE SLIDES OVERHEAD FROM 06Z TO AROUND 18Z
FRIDAY...SHOULD SEE A FEW ISOLATED THUNDERSTORMS AS MODEL MLCAPES OF
A COUPLE HUNDRED J/KG DEVELOP.
AT SOME POINT FRIDAY AFTERNOON THE PRECIP SHOULD BEGIN TO TAPER OFF
AS THE BEST MOISTURE CONVERGENCE AND ISENTROPIC ASCENT WILL BE
DISPLACED AWAY FROM THE FORECAST AREA...BUT STRONGLY BACKED WINDS
FROM 925-850MB COULD RESULT IN A QUASI-STATIONARY BAND OF PRECIP
SOMEWHERE IN/AROUND/TO THE NORTH OF THE PHOENIX AREA. THE LOW WILL
SLOWLY DEPART FRIDAY NIGHT INTO SATURDAY BUT MOIST NORTHWESTERLY
FLOW WILL CONTINUE INTO THE DAY ON SATURDAY. LOOKS LIKE A CONTINUED
CHANCE OF SHOWERS AND/OR SNOW IN THE MOUNTAINS EAST OF PHOENIX
THROUGH AT LEAST 18Z SATURDAY...BUT THE DESERTS SHOULD REMAIN DRY.
WITH SNOW LEVELS ONLY EXPECTED TO FALL TO AROUND 5000-5500
FT...NEARLY ALL OF THE HIGH IMPACT HIGHER ELEVATIONS WILL SEE PRECIP
REMAIN AS RAIN AS OPPOSED TO SNOW...BUT THE HIGHEST SPOTS COULD SEE
A QUICK INCH OR TWO OF SNOW BY THE TIME THINGS DRY OUT ENTIRELY ON
SUNDAY.
THE FORECAST FOR MONDAY THROUGH MID NEXT WEEK LOOKS DRY AS THE
NORTHWEST FLOW GRADUALLY FLATTENS OUT BY TUESDAY. LONG RANGE MODELS
INDICATE SOME SORT OF DISTURBANCE WILL MOVE THROUGH THE WESTERN U.S.
LATE TUESDAY THROUGH THURSDAY...BUT THE OVERWHELMING MAJORITY NOW
HAVE THIS STAYING TO OUR NORTH. THIS SOLUTION WILL KEEP US IN THE
DRY PATTERN WITH TEMPERATURES REACHING SEASONAL NORMALS BY MONDAY
AND PRETTY MUCH FLATLINING THEREAFTER.
&&
.AVIATION...
SOUTH-CENTRAL ARIZONA...INCLUDING KPHX...KIWA...AND KSDL...
LOW PRESSURE MOVING IN FROM THE WEST TO BRING GRADUALLY INCREASING
CLOUDINESS AND SHOWER ACTIVITY TO THE PHOENIX AREA THIS EVENING. THE
BEST CHANCE FOR SHOWER ACTIVITY APPEARS IT WILL BE BETWEEN MIDNIGHT
TONIGHT AND MIDMORNING ON FRIDAY...WITH CIGS DURING THIS PERIOD
LOWERING TO AROUND 3000FT...OR EVEN A LITTLE LOWER. CURRENT WESTERLY
BREEZES ARE EXPECTED TO DIMINISH OVER THE NEXT COUPLE OF
HOURS...THEN BECOME SOUTHEASTERLY LATER TONIGHT AS SFC LOW PRESSURE
APPROACHES FROM THE WEST. SHOWERS ARE EXPECTED TO DIMINISH/MOVE OFF
TO THE EAST AFTER 18Z FRIDAY...BUT MOIST UPSLOPE SOUTHWESTERLY FLOW
NEAR THE SFC WILL LIKELY KEEP LOWERED CIGS AROUND WELL INTO THE
AFTERNOON HOURS ON FRIDAY.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA...INCLUDING KIPL AND KBLH...
LOW PRESSURE ALOFT THAT WILL BE SWINGING OFF TO THE SOUTH AND EAST
OVER EXTREME NORTHWEST MEXICO WILL PUSH MID-LEVEL CIGS OVER BOTH
KIPL AND KBLH THROUGH THE REST OF TONIGHT...AND INTO EARLY FRIDAY.
THERE IS EVEN AN OUTSIDE CHANCE THE SHOWERS COULD IMPACT EITHER
TERMINAL...BUT CONFIDENCE IS TOO LOW TO INCLUDE ANYTHING MORE THAN
VCSH IN THE TAFS AT THIS TIME. CLEARING IS EXPECTED TO BEGIN AFTER
MID-MORNING ON FRIDAY. CURRENT WESTERLY TO SOUTHWESTERLY WINDS TO
BECOME NORTHWESTERLY BY LATE MORNING ON FRIDAY AS THE UPPER LOW
MOVES WELL OFF TO THE EAST.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
MOSTLY SUNNY SKIES WILL PREVAIL...AND A GRADUAL WARMING TREND WILL
TAKE PLACE THROUGH THE WEEKEND. HIGH TEMPERATURES WILL STAY BELOW
SEASONAL NORMALS...ESPECIALLY OVER SOUTH CENTRAL ARIZONA WHERE MAX
READINGS ARE EXPECTED TO BE THE UPPER 50S TO AROUND 60 DEGREES.
NORTHWEST WINDS WILL REMAIN BREEZY ACROSS SOUTHWEST ARIZONA AND
SOUTHEAST CALIFORNIA SATURDAY...WITH A LIGHTER WIND REGIME EXPECTED
AREA-WIDE SUNDAY THROUGH TUESDAY. MINIMUM HUMIDITIES WILL REMAIN
ELEVATED AND MOSTLY GREATER THAN 20 PERCENT THROUGH THE PERIOD.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&
$$
VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX
DISCUSSION...PERCHA/KUHLMAN/LEINS
AVIATION...PERCHA
FIRE WEATHER...MEYERS
AREA FORECAST DISCUSSION
NWS TUCSON AZ
535 AM MST WED DEC 18 2013
.SYNOPSIS...EXPECT UNSEASONABLY WARM TEMPERATURES AGAIN TODAY UNDER
A BLANKET OF HIGH LEVEL CLOUDS. A LOW PRESSURE SYSTEM WILL THEN
BRING GUSTY WINDS THURSDAY AFTERNOON FOLLOWED BY A GOOD CHANCE OF
VALLEY RAIN AND MOUNTAIN SNOW LATE THURSDAY NIGHT INTO EARLY
SATURDAY. COLDER TEMPERATURES WILL ALSO OCCUR FRIDAY THROUGH THE
WEEKEND. CLEARING FROM THE WEST SUNDAY WITH DRIER CONDITIONS AND A
SLOW WARMING TREND EARLY NEXT WEEK.
&&
.UPDATE...12Z TUCSON SOUNDING IS IN AND IT LOOKS FAIRLY SIMILAR TO
TUESDAY WITH A SUGGEST HIGH IN TUCSON OF 85 DEGREES. THAT WOULD TIE
THE ALL-TIME DECEMBER HIGH TEMPERATURE. CURRENT CIRRUS OVER THE AREA
RATHER THIN BUT THERE IS A THICKER DECK OVER NORTHERN BAJA WHICH
WILL MOVE OVER THE AREA LATER THIS MORNING. THIS SHOULD KEEP
TEMPERATURES FROM REACHING ITS POTENTIAL...HOWEVER SINCE MOST OF THE
AREA IS STARTING OFF WARMER THAN TUESDAY...BELIEVE MY CURRENT
FORECAST HIGHS FOR THE AREA ARE NOT WARM ENOUGH. LATEST RUNS OF THE
HRRR AND RAP SHOWS HOURLY TEMPERATURES IN TUCSON THIS AFTERNOON OF
81 AND 82 RESPECTIVELY. WITH THAT IN MIND...WILL MAKE A QUICK UPDATE
AND RAISE HIGHS UP TO 2 DEGREES. DAYSHIFT WILL CONTINUE TO MONITOR
IN CASE ANOTHER UPDATE IS NEEDED.
&&
.DISCUSSION...CONSIDERABLE HIGH CLOUDS ACROSS THE AREA THIS MORNING
PROVIDING A MILD DECEMBER NIGHT. SW FLOW ALOFT WILL KEEP THESE
CLOUDS AROUND FOR MOST OF THE DAYLIGHT HOURS AND THUS LIMITING
HEATING. AFTER A VERY WARM TUESDAY WHERE SOME SPOTS SET/TIED RECORD
HIGHS FOR THE 17TH...HIGHS TODAY WILL GENERALLY BE 2-8 DEGREES
COOLER. THERE IS A BACK EDGE TO THESE CLOUDS SO EXPECT CLEARING
SKIES FROM SW TO NE. WITH LESS CLOUD COVER...OVERNIGHT LOWS WILL BE
COOLER THAN THIS MORNING.
OUR NEXT WEATHER MAKER WILL BE IMPACTING THE PACIFIC NW TODAY. AS
THIS SYSTEM DROPS SOUTH AND DEEPENS OVER THE NEXT 24-36 HOURS...THE
PRESSURE GRADIENT WILL BE TIGHTENING UP FOR BREEZY TO LOCALLY WINDY
CONDITIONS ON THURSDAY. MODELS PRETTY SIMILAR IN SHOWING A CLOSED
540DM LOW NEAR LOS ANGELES BY LATE THURSDAY AFTERNOON. ADDITIONALLY
OVER THE NEXT 24-36 HOURS...THE HIGH PRECIPITABLE WATER VALUES THAT
ARE OVER SOUTHERN BAJA AND TO ITS SOUTH...WILL START TO WORKS ITS
WAY NORTH ACROSS SONORA MEXICO. MOISTURE ASSOCIATED WITH THE UPPER
LOW WILL ALSO INCREASE ACROSS NORTHERN BAJA CALIFORNIA.
CLOSED LOW IS FORECAST TO BE OVER NORTHERN BAJA THURSDAY NIGHT WITH
SHOWERS DEVELOPING OVER OUR WESTERN AREAS. HAVE INCREASED POPS WEST
OF TUCSON INTO THE 20-40% RANGE. THIS CLOSED LOW WILL CONTINUE TO
MOVE EAST ACROSS NORTHERN SONORA ON FRIDAY WITH MOISTURE INCREASING
OUT AHEAD OF LOW. HAVE INCREASED POPS...ESPECIALLY SOUTH OF TUCSON.
ALSO ADDED SLIGHT CHANCE OF THUNDER ALONG THE BORDER WHERE -24C 500
MB AIR WILL RESIDE. ALSO UPPER QPF VALUES AND SNOW AMOUNTS FOR AREAS
NEAR THE BORDER. SNOW LEVELS WILL BE LOWERING INTO THE 5500` TO
6500` LEVEL WITH 2-8 INCHES OF SNOW ABOVE 6000 FEET WITH HIGHEST
TOTALS ACROSS THE SOUTHERN MOUNTAIN RANGES. WE MAY EVENTUALLY NEED A
WINTER WEATHER ADVISORY FOR THESE RANGES ON FRIDAY. IT WILL BE MUCH
COOLER WITH HIGHS MOSTLY IN THE 50S FOR THE LOWER ELEVATIONS.
STORM TOTAL QPF WILL RANGE FROM 0.20" TO 0.80" WITH HIGHEST VALUES
ACROSS SOUTHERN TOHONO OODHAM NATION EAST ACROSS SANTA CRUZ COUNTY
AND THE SOUTHERN HALF OF COCHISE COUNTY.
SYSTEM EJECT EAST INTO WEST TEXAS ON SATURDAY WITH LINGERING SHOWERS
CONTINUING EASTERN AREAS A FAST MOVING SYSTEM DIVES IN FROM THE
NORTH OF BACK SIDE OF LOW. HIGHS ON SATURDAY WILL REMAIN RATHER
COOL.
WARMER AND DRY ON SUNDAY WITH WARMING TREND CONTINUING INTO THE
FIRST HALF OF NEXT WEEK.
&&
.AVIATION...BKN-OVC CLOUDS MAINLY ABOVE 20K FT AGL THRU 19/04Z...
THEN CLEARING SKIES FROM WEST TO EAST. ELY/SELY SURFACE WIND AT
10-15 KTS IN SOME AREAS THIS MORNING...PERSISTING THRU 18/18Z
INCLUDING KTUS...OTHERWISE SURFACE WIND LESS THAN 10 KTS. NORMAL
DIURNAL SURFACE WIND TRENDS ARE EXPECTED THIS AFTERNOON AND EVENING
WITH SURFACE WIND SPEEDS LESS THAN 10 KTS. STRONG AND GUSTY SURFACE
WINDS WILL DEVELOP THURSDAY MORNING...AND CONTINUE THROUGH THURSDAY
NIGHT AS A STORM SYSTEM MOVES INTO THE REGION. AVIATION DISCUSSION
NOT UPDATED FOR TAF AMENDMENTS.
&&
.FIRE WEATHER...DRY CONDITIONS WILL PREVAIL THROUGH THURSDAY. EXPECT
BREEZY CONDITIONS THURSDAY AFTERNOON AHEAD OF A LOW PRESSURE SYSTEM
MOVING INTO THE REGION. A FEW LOCALES IN COCHISE COUNTY MAY BRIEFLY
EXPERIENCE RED FLAG CONDITIONS THURSDAY AFTERNOON. THE LOW PRESSURE
SYSTEM WILL BRING A CHANCE OF SHOWERS MAINLY WEST OF TUCSON THURSDAY
NIGHT. VALLEY RAIN AND MOUNTAIN SNOW ARE THEN LIKELY ON FRIDAY AND
FRIDAY NIGHT FOR MUCH OF SOUTHEAST ARIZONA. EXPECT A FEW LINGERING
SHOWERS MOSTLY EAST OF TUCSON ON SATURDAY...THEN DRY CONDITIONS WILL
RETURN SUNDAY THROUGH NEXT TUESDAY.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON
AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
824 PM MST THU DEC 19 2013
.UPDATE...
&&
.SHORT TERM...STRATUS DECK HAS ENVELOPED MUCH OF NORTHEAST
COLORADO THIS EVENING WITH AREAS OF FOG ON THE PLAINS AND A FEW
SPOTS OF LIGHT FLURRIES AND EVEN FREEZING DRIZZLE. GIVEN THE
TEMPERATURE PROFILE AND SHALLOW MOISTURE THE CONDITIONS ARE OK FOR
THIS DRIZZLE TYPE. 88D IS SHOWING SOME VERY LIGHT ECHOES
DEVELOPING OVER EAST DENVER SO INDEED SOME VERY LIGHT SNOW CAN BE
EXPECTED TONIGHT. MOST MODEL AND ENSEMBLE DATA SHOWING VERY LOW
AMOUNTS...GENERALLY UNDER A 1/2 INCH OR LESS. WILL TWEAK THE
POP/WEATHER GRIDS TO ACCOUNT FOR CURRENT TRENDS. AS FOR THE
MOUNTAINS...NO SNOW HAS DEVELOPED SO FAR THIS EVENING BUT SHOULD
SEE MORE OROGRAPHIC INDUCED SNOWFALL LATER TONIGHT.
.AVIATION...LOW CEILINGS BELOW 1000FT AGL HAVE DEVELOPED AT LOCAL
TERMINALS THIS EVENING. ALSO EXPECT SOME REDUCED VISIBILITIES IN
FOG AND LIGHT SNOW AS WELL. SNOW AREAL COVERAGE WILL BE SPOTTY SO
NOT EXPECTING MUCH ACCUM...GENERALLY UNDER A HALF INCH OR LESS.
WILL WILL CONTINUE WINDS FROM THE NORTHEAST AT 10-20 MPH BEFORE
SHIFTING A BIT MORE EASTERLY AND WEAKENING THRU THE NIGHT.
&&
.PREV DISCUSSION... /ISSUED 352 PM MST THU DEC 19 2013/
SHORT TERM...SOUTHWEST FLOW ALOFT CURRENTLY ACROSS COLORADO. MID
LEVEL MOISTURE SPREADING BACK INTO THE MOUNTAINS AND FROM WEB CAMS
IT APPEARS THERE IS SOME LIGHT SNOW OVER THE HIGHER MOUNTAINS.
SNOW COVERAGE WILL GRADUALLY INCREASE THIS EVENING AS MOISTURE AND
OROGRAPHICS INCREASE...WITH THE FLOW FAVORING THE NORTHERN
MOUNTAINS. BUT THE SNOW WILL BE LIGHT DUE TO LACK OF ANY MID LEVEL
ASCENT... WITH ACCUMULATIONS LESS THAN 3 INCHES. AFTER
MIDNIGHT...THE SNOW WILL DECREASE AGAIN AS THE FLOW ALOFT WEAKENS
ALONG WITH WEAKENING OROGRAPHICS. ALONG FOOTHILLS AND ACROSS
PLAINS...COLD FRONT CURRENTLY PUSHING INTO NORTHERN COLORADO WITH
SOME GUSTS TO AROUND 25 KTS. FRONT WILL CONTINUE TO MOVE SOUTH
THROUGH THE EVENING WITH UPSLOPE DEVELOPING AND LOW LEVEL MOISTURE
INCREASING. CROSS SECTIONS SHOW UPSLOPE TO BE AROUND 700 MB NEAR
THE FOOTHILLS. THERE STILL LOOKS TO BE WINDOW BETWEEN 02Z AND 07Z
FOR SOME LIGHT SNOW TO DEVELOP...MAINLY IN AND NEAR THE FOOTHILLS.
LATEST RAP ALSO SHOWS SOME CHANCE ALONG THE PALMER. STILL THE BEST
CHANCE FOR SNOW WILL BE ACROSS ZONE 35 WHERE LOW LEVEL UPSLOPE
WILL BE AIDED WITH THE SOUTHWEST FLOW ALOFT AND WILL CONTINUE
LIKELY POPS THERE WITH SNOW AMOUNTS AROUND AN INCH. WILL KEEP A
CHANCE OF LIGHT SNOW ALONG THE URBAN CORRIDOR AND SOUTHERN
FOOTHILLS WITH LOWER POPS FURTHER EAST. AFTER 07Z THE UPSLOPE
WEAKENS AND THE AIRMASS BEGINS TO DRY OUT...LOWER POPS STILL LOOK
REASONABLE. AIRMASS FAIRLY COLD OVER WYOMING AND NEBRASKA...AND
THIS AIR SHOULD STAY TO THE NORTH AND EAST OF COLORADO.
STILL...OVERNIGHT TEMPERATURES TO DROP INTO THE TEENS ACROSS THE
PLAINS...WITH SINGLE DIGIT READINGS NEAR THE WYOMING AND NEBRASKA
PANHANDLE. ON FRIDAY...FLOW ALOFT BECOMES WESTERLY...A BIT
NORTHWEST AT MOUNTAIN TOP DURING THE AFTERNOON. THERE IS ALSO SOME
INCREASE IN MID LEVEL ASCENT. THIS WILL RESULT IN SOME INCREASE IN
LIGHT SNOW BY THE AFTERNOON. STILL ACCUMULATIONS WILL REMAIN
LIGHT. ACROSS PLAINS...A DRIER BUT COLD AIRMASS WILL BE OVER THE
AREA. THERE MAY BE SOME LINGERING FLURRIES DURING THE
MORNING...OTHERWISE NO SNOW IS EXPECTED. TEMPERATURES WILL SLOWLY
WARM INTO THE 30S ACROSS THE PLAINS...EXCEPT UPPER 20S FAR
NORTHEAST CORNER.
LONG TERM...DRYING AND SUBSIDENCE THROUGH TOMORROW EVENING SHOULD
BRING A DECREASE OF SNOW SHOWERS IN THE MOUNTAINS. HOWEVER...THE
NEXT SHORT WAVE IS QUICK ON ITS HEELS WHICH WILL BRING A RETURN OF
HIGH COUNTRY SNOWFALL BY EARLY SATURDAY MORNING. MOISTURE IS
DEEPER BUT STABILITY PROFILE IS ONLY MARGINAL WITH A STABLE LAYER
NEAR MOUNTAIN TOP BUT OK 5-6C/KM LAPS RATES FARTHER UP. THE END
RESULT SHOULD BE A LIGHT SNOW EVENT FOR MOUNTAINS STANDARDS WITH
ANOTHER 1-4 INCHES SATURDAY.
BY LATE SATURDAY AFTERNOON AND EVENING...THERE IS SOME LOW LEVEL
ANTICYCLONIC TURNING WHICH COULD ALLOW A LITTLE SNOW TO SPILL OUT
ONTO THE PLAINS IN SHALLOW UPSLOPE. AT THIS TIME...THIS ONLY
LOOKS LIKE A LIGHT DUSTING IF ANYTHING SO WILL CONTINUE THE LOW
POPS FOR SATURDAY EVENING.
BY LATE SUNDAY...ANOTHER FAST MOVING SHORT WAVE MAY APPROACH FROM
THE NORTHWEST BRINGING MORE MOUNTAIN SNOW SHOWERS. AGAIN..THERE
MAY BE A LOW CHANCE ON THE PLAINS WITH A WEAK FRONTAL SURGE AND
LIFT ASSOCIATED WITH LEFT EXIT REGION OF UPPER JET. HAVE THROWN IN
SOME POPS FOR THE NORTHEAST CORNER OF THE STATE...BUT EVENTUALLY MAY
HAVE TO INCLUDE THE FRONT RANGE URBAN CORRIDOR CONSIDERING THIS IS
A NORTHWEST FLOW EVENT WITH A STRONG UPPER JET. TEMPERATURES WILL
AVERAGE A FEW DEGREES BELOW NORMAL FOR THE SATURDAY-SUNDAY PERIOD.
MAINLY DRY AND WARMER WEATHER IS EXPECTED MONDAY INTO TUESDAY.
THEN...ANOTHER SHORT WAVE IS ADVERTISED BY MOST MEDIUM RANGE
MODELS TO DROP ACROSS THE STATE CHRISTMAS EVE INTO CHRISTMAS
MORNING. TIMING IS BECOMING INCREASINGLY DIFFICULT IN THIS FAST
NORTHWEST FLOW PATTERN...SO EXTENDED PERIODS OF LOW POPS IS
WARRANTED FOR NOW. THAT PARTICULAR WAVE WILL BE THE PLAINS BEST
CHANCE OF A WHITE CHRISTMAS.
AVIATION...FRONT MOVING INTO NORTHERN WELD COUNTY...SHOULD REACH
THE AREA AIRPORTS BY 00Z. NORTHERLY WINDS WILL GUST TO AROUND 25
KTS WITH THE FRONT PASSAGE. CLOUDS WILL CONTINUE TO INCREASE WITH
CEILINGS LOWERING TO IFR BY 01Z WITH DECREASING WINDS. THERE IS
STILL A CHANCE FOR LIGHT SNOW BETWEEN 02Z AND 08Z...THOUGH THIS
CHANCE IS DECREASING AS THE MOISTURE IS BECOMING MORE SHALLOW.
WILL CONTINUE THE VCSH FOR NOW. CONDITIONS TO IMPROVE AFTER 08Z
WITH WINDS SHIFTING TO THE SOUTHEAST. AFTER 13Z SHOULD SEE
CEILINGS IMPROVE TO VFR.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...ENTREKIN
LONG TERM....BARJENBRUCH
AVIATION...ENTREKIN
AREA FORECAST DISCUSSION
NWS GRAND JUNCTION CO
1213 PM MST WED DEC 18 2013
.UPDATE...
ISSUED AT 1210 PM MST WED DEC 18 2013
DENSE FOG ADVISORY FOR THE LOWER PORTIONS OF THE COLORADO RIVER
VALLEY WAS CANCELLED BY 1030.
ATTENTION TURNS TO POTENTIAL FOR FREEZING RAIN IN THE VALLEYS
TONIGHT. INVERSIONS ARE BEING MODIFIED SOMEWHAT TODAY WITH GUSTY
WINDS AT 700MB CREATING SOME TURBULENCE MIXING AT THE TOPS OF THE
INVERSION. THE UINTAH AND GUNNISON BASINS WILL LIKELY STAY TRAPPED
WHILE THE OTHER VALLEYS WILL SEE SOME EROSION ALONG THE EDGES.
TONIGHT...MOISTURE INCREASES IN MILD WARM ADVECTION. MODEL TIMING
IS CONSISTENT WITH THE RAP 17Z SUPPORTING THE 12Z NAM FOR QPF
SPREADING INTO NE UT AROUND 03Z AND INTO WESTERN CO AROUND 06Z.
THE BEST CHANCE FOR VALLEY PRECIP IS 09-15Z EARLY THURSDAY MORNING
FOR THE NORTHERN AND CENTRAL VALLEYS. THE NAM IS THE WET OUTLIER
OVERNIGHT. FORECAST PROFILES SHOW AN ABOVE FREEZING LAYER TO 8KFT
ABOVE THE GRAND VALLEY BUT WITH SURFACE TEMPERATURES FORECASTED TO
STAY IN THE UPPER 20S OVERNIGHT. THE POTENTIAL FOR FREEZING RAIN
IS STILL IN PLACE TONIGHT FOR THE NORTHERN AND CENTRAL VALLEYS SO
WE ARE CONSIDERING AN ADVISORY.
OTHERWISE COLD ADVECTION BEGINS EARLY THURSDAY MORNING WITH SNOW
LEVELS AROUND 7500FT NORTH THROUGH THE DAY. THE ASSOCIATED COOL
FRONT WITH THE ELONGATED TROUGH NOW IS PROGGED TO STAY NORTH OF THE
FORECAST AREA THROUGH THURSDAY THEN PUSH INTO NE UT-NW CO THURSDAY
NIGHT. SNOW AMOUNTS ARE EXPECTED TO BE LIGHT...BELOW ADVISORY
AMOUNTS IN THE NORTHERN MTNS.
&&
.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 329 AM MST WED DEC 18 2013
HIGH LEVEL CLOUDS HAVE SPREAD ACROSS THE FORECAST AREA AHEAD OF A
PACIFIC UPPER LOW APPROACHING THE CA COAST EARLY THIS MORNING. THIS
LOW IS GETTING ENTRAINED IN THE NORTHERN STREAM AND WILL BE EJECTED
INLAND AS AN OPEN WAVE TODAY AND TRACK ACROSS ERN UT/WRN CO LATE
TONIGHT AS A COLDER SHORTWAVE TROUGH DROPS DOWN THE BRITISH COLUMBIA
AND THEN PACIFIC NW COAST. PARTLY SUNNY SKIES ARE EXPECTED TODAY
WITH TEMPS SIMILAR OR A FEW DEGREES WARMER THAN YESTERDAY IN SW FLOW
ALOFT. CLOUDS THICKEN AND LOWER TONIGHT WITH SOME SNOW DEVELOPING
ACROSS MAINLY THE CENTRAL AND NORTHERN MTNS AS MODELS SHOW A DECENT
AMOUNT OF MOISTURE CONTENT FOR THIS TIME OF YEAR. THE SAN JUANS
SHOULD SEE SOME LIGHT ACCUMULATIONS TOWARD THU MORNING AS THE
EJECTING CA LOW/TROUGH PASSES.
THE POTENTIAL FOR SOME FREEZING RAIN PERSISTS FROM ROUGHLY MIDNIGHT
TONIGHT TO SUNRISE THURSDAY...WHEN THAT CA LOW/TROUGH IS EXPECTED TO
MOVE PAST. NOT SURE THE MODEL FORECAST SOUNDINGS ARE HANDLING THE
VERY SHALLOW COLD AIR TRAPPED IN MANY VALLEYS. MAIN AREA OF CONCERN
IS THE WEST-CENTRAL VALLEYS OF WRN CO AND THE EAST-CENTRAL VALLEYS
OF ERN UTAH AND POSSIBLY AS FAR SOUTH AS BLANDING AND CORTEZ. WITH
LITTLE MIXING EXPECTED TODAY...THE STAGNANT COLD AIR WILL REMAIN
OVER THESE SNOW COVERED AREAS. WITH THE WARMER AND MOIST AIR
ASSOCIATED WITH THE PACIFIC DISTURBANCE MOVING OVERHEAD...THIS
COMBINATION COULD LEAD TO SOME LIGHT FREEZING RAIN IN PLACES. THE
TUESDAY FORECAST TEAM ISSUED A SPECIAL WEATHER STATEMENT FOR THIS
POSSIBILITY...AND THAT STATEMENT WILL BE CONTINUED.
THE COLDER TROUGH DROPPING DOWN THE WEST COAST OF NORTH AMERICA
TODAY IS EXPECTED TO SPLIT WITH THE SOUTHERN SECTION FORMING A
CLOSED LOW IN THE VICINITY OF LOS ANGELES BY LATE THU AFTERNOON.
THIS WILL KEEP SW FLOW ACROSS OUR AREA THU WHILE THE NRN SECTION
MOVES ACROSS THE NRN ROCKIES. 700 MB FRONT AND LOW LEVEL CONVERGENCE
SET UP NEAR THE CO-WY BORDER AND SHOULD BE THE MAIN FOCUS FOR
PRECIPITATION. WILL KEEP HIGHEST POPS ACROSS THE NORTH ON THU.
DESPITE SW FLOW ALOFT...THU TEMPS WILL BE COOLER IN MOST PLACES AS
COLDER AIR OOZES IN BEHIND THE WED NIGHT DISTURBANCE.
.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 329 AM MST WED DEC 18 2013
THURSDAY NIGHT AND FRIDAY...THE WARM FRONT WHICH BROUGHT THE MIXED
PRECIPITATION TO THE AREA WILL WAVE NORTH THU EVENING WITH MOST
PCPN ENDING ACROSS CENTRAL AND SOUTHERN AREAS. THE DEFORMATION
ZONE WILL REMAIN STATIONARY OVER THE NORTHERN HALF OF THE
AREA...AND PRODUCE ISOLD TO SCATTERED SNOWFALL OVERNIGHT...MAINLY
IN THE NORTHERN AND CENTRAL MOUNTAINS. ALL MODELS AGREE ON THIS
SCENARIO...BUT THE NAM IS BY FAR THE DRIEST. HAVE STAYED CLOSER TO
THE WETTER SOLUTIONS. FOR MOST OF FRIDAY THE DEFORMATION ZONE WILL
REMAIN ALONG THE CO/WY BORDER...THEN BEGIN MOVING EAST AND SOUTH
AS THE SPLIT TROUGH MOVES EAST AND SOUTH AS WELL. FRIDAY NIGHT THE
FLOW ALOFT TURNS NORTHWESTERLY IN THE GFS AND ECMWF AND A SERIES
OF VORT MAXES EMBEDDED IN THE NW FLOW WILL MOVE OVER THE AREA...
CAUSING CLOUDS AND PCPN TO INCREASE FROM NW TO SE.
SATURDAY AND SUNDAY...AS THE EMBEDDED TROUGHS MOVE OVERHEAD...
MOISTURE AND PRECIPITATION INCREASE ACROSS THE AREA. THE PERIOD OF
HEAVIEST AND MOST WIDESPREAD PCPN APPEARS TO BE SATURDAY THRU
SATURDAY EVENING. LATE SAT NIGHT THROUGH SUN SHOULD SEE A RIDGE
BUILDING OVER THE WESTERN U.S. WHICH PUSHED THE PCPN BAND EAST.
THE FLOW ALOFT SHOULD REMAIN NORTHWESTERLY WITH ENOUGH MOISTURE
FOR OROGRAPHIC SNOW SHOWERS TO CONTINUE OVER THE NORTHERN AND
CENTRAL CO MOUNTAINS.
MONDAY AND TUESDAY SHOULD SEE A CONTINUE DRYING TREND UNDER
NORTHWEST FLOW ALOFT.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY MORNING)
ISSUED AT 1210 PM MST WED DEC 18 2013
VFR CONDITIONS WILL DOMINATE THROUGH THE AFTERNOON AND EARLY
EVENING. CLOUDS AND PRECIPITATION WILL INCREASE OVER EASTERN UT
THIS EVENING AND SPREAD EAST ACROSS WESTERN CO OVERNIGHT. MVFR
CIGS AND VSBYS AREA POSSIBLE ACROSS THE AREA BY ABOUT 07Z WITH
SNOW IN THE MOUNTAINS...MIXED RAIN AND SNOW AND EVEN SOME FREEZING
RAIN POSSIBLE...IN MOST VALLEYS. MOUNTAIN TOPS WILL BECOME
OBSCURED 07Z-15Z...THEN LIMITED TO THE MTNS EAST OF A LINE FROM
KCAG TO KGUC AFT 15Z.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&
$$
UPDATE...JOE
SHORT TERM...JAD
LONG TERM...CC
AVIATION...JOE/CC
AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
1007 AM MST WED DEC 18 2013
.UPDATE...
&&
.SHORT TERM...OVERALL...CURRENT FORECASTS LOOK REASONABLE...SOME
MINOR ADJUSTMENTS FOR CLOUD COVER AND WIND. FAIRLY EXTENSIVE
CLOUD COVER ACROSS MUCH OF THE AREA...LESS OVER THE HIGHER
TERRAIN. MOUNTAIN WAVE CLOUDS SITUATED EAST OF THE FOOTHILLS AND
URBAN CORRIDOR. MODELS DO INDICATE SOME BREAKUP OF THE WAVE CLOUD
DURING THE AFTERNOON...WITH SOME VARIATION. APPEARS THERE WILL BE
ENOUGH CLOUD TO SLOW THE EXPECTED WARMUP...EVEN WITH THE WARM
BEGINNING. ENOUGH MIXING WILL SHOULD BRING TEMPERATURES INTO THE
MIDDLE 60S ACROSS MUCH OF THE PLAINS. IT IS VERY POSSIBLE THE
RECORD OF 66 FOR DENVER WILL BE SURPASSED GIVEN THE WARMER AIRMASS
AND EXPECTED MIXING. WINDS HAVE BEEN A BIT GUSTY IN AND NEAR
FOOTHILLS...SHOULD CONTINUE FOR MUCH OF THE DAY BEFORE DECREASING
AS SURFACE GRADIENT WEAKENS. APPEARS TEMPERATURES WILL GO BELOW
THE MORNING LOW OF 43 DEGREES AT DENVER DUE TO WEAK EASTERLY WINDS
BRINGING COOLER AIR INTO THE AREA...NOT EXPECTING A RECORD LOW MIN
FOR THE DAY. FLOW ALOFT GOES FROM WESTERLY TO SOUTHWEST THIS
EVENING WITH MORE MID LEVEL MOISTURE STREAMING TOWARD THE AREA.
SHOULD SEE SOME OROGRAPHIC SNOW DEVELOPING IN THE PARK AND GORE
RANGES SOMETIME AFTER MIDNIGHT. THERE MAY ALSO BE SOME LIGHT SNOW
OVER THE FRONT RANGE MOUNTAINS LATE...WITH THE POTENTIAL FOR SOME
BANDED PRECIPITATION.
.AVIATION...SOUTHWEST WINDS SPREADING ACROSS THE AREA AIRPORTS
WITH HELP OF MIXING. SOME GUSTS TO 30 KTS AT KBJC. SHOULD SEE A
CONTINUATION OF THE SOUTHWESTERLY WINDS THROUGH THE AFTERNOON...
MAY BE MORE WESTERLY AT KDEN BY 20Z. LATEST RAP AND HRRR
SUGGESTING WINDS SHIFTING TO THE NORTHWEST BETWEEN 22Z AND 23Z AS
GRADIENT BEGINS TO WEAKEN AND WINDS TRY TO GO CLOCKWISE. FOR NOW
WILL CONTINUE WITH THE CURRENT TAF TRENDS...WITH THE IDEA OF
ENOUGH MIXING WILL KEEP THE WINDS FROM SHIFTING TO THE NORTHWEST.
VFR WILL CONTINUE THROUGH THURSDAY AFTERNOON...WITH MID LEVEL
MOISTURE INCREASING AFTER MIDNIGHT. COLD FRONT EXPECTED TO MOVE
ACROSS THE AREA AIRPORTS AROUND 19 OR 20Z WITH A NORTHERLY WIND
SHIFT. SOME LOWERING OF THE CEILING DURING THE AFTERNOON. THERE
MAY BE A CEILING OF AROUND 6000 FEET AT KDEN BY 00Z FRIDAY...
CHANCES ARE LOW AT THIS TIME.
&&
.PREV DISCUSSION... /ISSUED 449 AM MST WED DEC 18 2013/
SHORT TERM...MAIN QUESTION TODAY IS THE AMOUNT OF CLOUD COVER AND
ITS EFFECT ON TEMPERATURES. PLENTY OF MOISTURE UPSTREAM THOUGH
THERE IS SOME VARIABILITY. WITH NOT MUCH CHANGE IN THE WIND
PATTERN...EXPECT THE WAVE CLOUD COVERING THE PLAINS TO CHANGE
LITTLE TODAY WHILE THERE MAY BE SOME DECREASE IN THE HIGH CLOUDS
OVER THE MOUNTAINS. CIRA SIMULATED SATELLITE IMAGERY SHOWS A
PRETTY SOLID WAVE CLOUD PERSISTING DOWNSTREAM OF THE FRONT RANGE
THROUGH TONIGHT WITH POOR AGREEMENT ON THE TIMING OF ANY CLEARING
ELSEWHERE. SHOULD BE ENOUGH CLOUDS TO LIMIT TEMPERATURES...BUT THE
AIRMASS HAS ALSO WARMED A LITTLE SINCE YESTERDAY. WE WILL BE OFF
TO A WARM START...ALREADY IN THE 50S IN THE LOWER FOOTHILLS. UNDER
CLEAR SKIES IT WOULD PROBABLY BE 70 IN DENVER TODAY...SO THE
CURRENT MID 60S FORECAST IS PROBABLY STILL ALRIGHT. I DID LOWER
THE HIGHS A LITTLE IN THE MOUNTAIN VALLEYS ESPECIALLY GRAND
COUNTY. THESE AREAS DID NOT WARM AS MUCH YESTERDAY AND COOLED
FURTHER OVERNIGHT.
CLOUDS THICKEN UP TONIGHT WITH MID LEVEL MOISTURE MOVING INTO THE
MOUNTAINS. EXPECT LIGHT OROGRAPHIC SNOW IN THE PARK RANGE...AND
POSSIBLY STARTING IN THE FRONT RANGE MOUNTAINS LATE TONIGHT.
PREFRONTAL WIND SHIFT TO SOME KIND OF EASTERLY SHOULD BRING COLDER
LOWS ON THE PLAINS...THOUGH THIS MAY NOT GET INTO PLACES LIKE
BOULDER. LOW SINCE MIDNIGHT OF 43 WOULD BREAK THE RECORD HIGH
MIN...WE COULD GET BELOW THAT IF THE WESTERLIES STOP AT DIA BEFORE
MIDNIGHT. ALSO FORECASTING A HIGH THERE OF 66 WHICH WOULD TIE THE
RECORD FOR THE DATE.
LONG TERM...ON THURSDAY...A STRONG SOUTHWESTERLY FLOW ALOFT WILL
BE OVER COLORADO AHEAD OF AN UPPER TROUGH THAT WILL STRETCH FM WRN
MONTANA INTO NRN CA. THE TROUGH WILL REMAIN TO THE WEST OF
COLORADO WITH THE NRN BRANCH MOVING EASTWARD WHILE THE SRN BRANCH
SLIDES INTO SRN CALIFORNIA. IN THE MOUNTAINS...SPATIAL
CROSS-SECTIONS INDICATE A WSWLY RIDGETOP WINDS AROUND 30 KTS ON
THURSDAY. MOISTURE DEEP ENOUGH TO PRODUCE SOME OROGRAPHIC
SNOWFALL WHICH WOULD MOST FAVOR ZONES 31 AND 33. WEAK COLD AIR
ADVECTION PRESENT SO SUSPECT GENERALLY LIGHT SNOW ALONG AND NORTH
OF THE INTERSTATE 70 CORRIDOR. ANY ACCUMULATIONS WILL OCCUR ALONG
WEST FACING ASPECTS (2-4 INCHES). FROM THE FRONT RANGE FOOTHILLS
EASTWARD...A COLD FRONT WILL MAKE ITS WAY SOUTHWARD BY THE
AFTERNOON...WITH NELY UPSLOPE WINDS INCREASING TO AROUND 700 MB BY
THURSDAY EVENING. THE CHANCE OF SNOW WILL DECREASE IN THE
MOUNTAINS WEST OF THE DIVIDE BUT INCREASE FM NORTH TO SOUTH IN AND
NEAR THE FRONT RANGE THURSDAY EVENING. THE BEST CHC OF SNOW WILL
BE IN ZONES 35 AND 38...WHERE ACCUMULATIONS OF AN INCH OR TWO MAY
BE POSSIBLE...WITH LESSER AMOUNTS IN ZONE 36. THE UPSLOPE WILL BE
FAIRLY SHALLOW AND BRIEF WITH CONDITIONS IMPROVING AFTER 09Z
THURSDAY NIGHT AS THE LOW LEVEL WINDS BECOME NWLY. AFTER 12Z
FRIDAY...THE AIRMASS WILL BE COOLER WITH SHALLOW LOW LEVEL
MOISTURE LINGERING UNTIL 15Z...THEN THE AIRMASS WILL BE DRY FROM
THE FRONT RANGE FOOTHILLS EASTWARD. THE CHANCE OF SNOW WILL
CONTINUE IN THE MOUNTAINS WEST OF THE CONTINENTAL DIVIDE FOR
FRIDAY THROUGH SUNDAY. OVERALL THE SNOW AMOUNTS WILL BE LIGHT (UP
TO 3 INCHES IN EA 12 HR PERIOD). IT WILL REMAIN COOL IN DENVER ON
SATURDAY WITH ANOTHER WEAK BOUT OF UPSLOPE EXPECTED SATURDAY
EVENING. NOT MUCH IN THE WAY OF UPPER LEVEL SUPPORT AS A VERY
ELONGATED UPPER TROUGH AXIS EVENTUALLY SLIDES ACROSS EASTERN
COLORADO LATE SATURDAY. OVERALL QG ASCENT WILL BE NEARLY NEUTRAL
SATURDAY NIGHT. THE FLOW ALOFT WILL BE NORTHWESTERLY ON SUNDAY
WITH INCREASING SUBSIDENCE EXPECTED. WILL KEEP A CHANCE OF SNOW
GOING IN THE MOUNTAINS BUT DRY ELSEWHERE. A GENERALLY DRY
NORTHWESTERLY FLOW WILL CONTINUE INTO EARLY NEXT WEEK. THE NEXT
STORM SYSTEM IS PROGGED TO DROP OUT OF THE NORTHWEST AND POSSIBLY
IMPACT NORTHEAST COLORADO ON CHRISTMAS EVE...WITH A CHANCE OF SNOW
FOR THE CWFA ON CHRISTMAS...AT LEAST FOR NOW.
AVIATION...VFR THROUGH TONIGHT. WIND WILL BECOME WESTERLY AT
KDEN/KAPA WITH GUSTS TO AROUND 20 KNOTS BY MIDDAY...WHILE WEST
WINDS GUSTING IN THE 20 TO 30 KNOT RANGE WILL BE COMMON AT KBJC
TODAY. WINDS WILL DIMINISH IN THE LATE AFTERNOON OR EARLY EVENING.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...D-L
LONG TERM....COOPER
AVIATION...D-L
AREA FORECAST DISCUSSION
NWS TAUNTON MA
1020 PM EST THU DEC 19 2013
.SYNOPSIS...
DRY WEATHER WILL CONTINUE TONIGHT AND INTO TOMORROW...ISOLATED
SHOWERS ARE POSSIBLE NORTH OF ROUTE 2. A COLD FRONT WILL STALL TO
OUR NORTH TOMORROW. THIS STALLED FRONT WILL RESULT IN PERIODS OF
UNSETTLED WEATHER FRI NIGHT THROUGH EARLY MON. DRIER AND COOLER
WEATHER ARRIVES EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
10 PM UPDATE...
FORECAST REMAINS ON TRACK WITH WINDS CONTINUING TO LIGHTEN AND
A BROKEN CIRRUS CLOUD DECK MOVING THROUGH THE AREA. LATEST SATELLITE
IMAGERY INDICATES THAT CLOUDS WILL CONTINUE TO CROSS OVER
SOUTHERN NEW ENGLAND OVERNIGHT. MADE MINOR TWEAKS TO TEMPERATURESTO
REFLECT LATEST OBSERVED TRENDS.
PREVIOUS DISCUSSION...
STATIONARY BOUNDARY WILL SET UP ACROSS NORTHERN NEW ENGLAND
TONIGHT AS A RESULT OF AN APPROACHING LOW PRESSURE SYSTEM FROM THE
GREAT LAKES. THIS FRONT WILL ALLOW FOR PRECIP TO DEVELOP ALONG IT
OVERNIGHT AND INTO TOMORROW MORNING. LATEST GUIDANCE KEEPS THIS
FRONT FARTHER NORTH OF THE REGION. HI-RES GUIDANCE AND HRRR KEEP
ALL THE PRECIP NORTH OF THE REGION AS WELL. HOWEVER DID KEEP SOME
LINGERING POPS FOR THE EARLY MORNING HOURS. THIS MAY ALLOW FOR
SOME LIGHT FREEZING RAIN IN THE FAR NORTHERN PORTION OF
FRANKLIN...HILLSBOROUGH AND CHESHIRE COUNTIES. BUT BECAUSE OF THE
LOW CONFIDENCE AND THE FACT THAT HI-RES GUIDANCE KEEPS THIS
PORTION MAINLY DRY DID NOT ISSUE ANY HEADLINES AT THIS TIME.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
FRIDAY INTO FRIDAY NIGHT...ABOVE AVERAGE TEMPERATURES WILL
CONTINUE INTO FRIDAY HOWEVER BY JUST A FEW DEGREES. INITIALLY
THOUGHT THAT TEMPS TOMORROW WILL BE WELL INTO THE 50S AS WE HIT
THE MID 40S TODAY. YET LOOKING AT SOUNDING DATA APPEARS THAT AN
INVERSION WILL BE SET UP OVER THE REGION. SO WHILE 925 MB TEMPS
WILL BE BETWEEN 7C TO 9C...WE MAY BE IN THE LOW TO UPPER 40S
ACROSS THE AREA AT THE SURFACE. THE MAX T GRID FOR TOMORROW MAY BE
TO OPTIMISTIC. A STRAY SHOWER OR TWO MAY MOVE ACROSS THE REGION
TOMORROW AS THE BOUNDARY BEGINS TO SLIDE SOUTHWARD...BUT OVERALL
FEEL MAINLY DRY WEATHER FOR TOMORROW ESPECIALLY SOUTH OF ROUTE 2.
THAT FRONT WILL SLIDE FARTHER SOUTH AND CLOSER TO THE NW COUNTIES ON
FRIDAY NIGHT INCREASING THE POTENTIAL FOR SOME PRECIP AS A LOW
PRESSURE MOVES ALONG THE BOUNDARY. SURFACE TEMPS WILL BE NEAR OR
ABOVE FREEZING FOR THIS TIMEFRAME SO THE POTENTIAL FOR ICING IS
LESS. THE HIGHEST LOCATION FOR PRECIP TO OCCURS WILL BE REGIONS
NORTH OF ROUTE 2 WITH AN ISOLATED CHANCE NORTH OF THE MASS PIKE.
TEMPERATURES OVERNIGHT WILL ONLY DROP SLIGHTLY AS OVERCAST SKIES AND
WEAK WAA WILL LIMIT RADIATIONAL COOLING.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
* UNSETTLED WEATHER OVER THE WEEKEND
* DRIER...COOLER WEATHER EXPECTED EARLY NEXT WEEK
SATURDAY...COLD FRONT IS NEARLY STATIONARY ACROSS
NORTHERN/CENTRAL NEW ENGLAND EARLY IN THE DAY...WITH MODELS
INDICATING THIS FRONT WILL SLOWLY PUSH SOUTHWARD DURING THE DAY.
LIGHT RAIN SHOWERS POSSIBLE OVER SOUTHERN NH/NORTHERN MA IN THE
MORNING...WITH INCREASING CHANCES FOR RAIN SHOWERS TO THE SOUTH IN
THE AFTERNOON. QPF AMOUNTS EXPECTED TO BE LIGHT.
SATURDAY NIGHT...AGREEMENT BETWEEN THE GFS AND ECMWF THAT FRONT WILL
BECOME DRAPED IN THE VICINITY OF SOUTHERN NH/NORTHERN MA DURING THIS
TIMEFRAME. THERE IS STILL UNCERTAINTY REGARDING THE TEMPERATURE
PROFILE SATURDAY NIGHT AND SUNDAY...BUT THE TREND CONTINUES TO BE
KEEPING MOST OF THE CWA OUT OF THE MUCH COLDER TEMPERATURES AND
FREEZING RAIN. THE MAIN CONCERN AT THIS POINT IS SURFACE
TEMPERATURES IN THE FAR NORTHERN TIER OF THE FORECAST AREA...IN
PARTICULAR SOUTHERN NEW HAMPSHIRE. THERE IS A RISK FOR A PERIOD OF
FREEZING RAIN IN CHESHIRE AND HILLSBOROUGH COUNTIES LATE SATURDAY
NIGHT INTO SUNDAY MORNING...WITH A VERY LOW CHANCE OF FREEZING RAIN
DURING THIS TIMEFRAME OVER EXTREME NORTHERN MA.
SUNDAY...FRONT BEGINS TO PUSH NORTHWARD AS A WARM FRONT DURING THE
DAY...ANY FREEZING PRECIPITATION SHOULD CHANGE OVER TO RAIN SHOWERS
AS THE MORNING PROGRESSES. QPF TOTALS FOR SUNDAY ARE UNCERTAIN FOR
SOUTHERN NEW ENGLAND...EARLY INDICATIONS ARE 0.25 INCH TO AN
INCH...BUT IN ADDITION TO THIS RAIN THERE WILL BE SNOWMELT. ACROSS
MOST OF MASSACHUSETTS...AS WELL AS N CT AND RI...SURFACE DEWPOINTS
ARE EXPECTED TO CLIMB INTO THE 50S. HIGH TEMPERATURES MAY REACH MID
50S TO AROUND 60. THIS WITH A 10 TO 15 MPH SOUTHERLY SURFACE WIND
WILL PROMPT CONSIDERABLE SNOWMELT. THE SNOWMELT ALONG WITH
MODERATE QPF COULD CAUSE FLOODING IN LOW LYING AND POOR DRAINAGE
AREAS. ANY DRAINS THAT ARE SNOW CLOGGED COULD POSE A FLOOD RISK.
SUNDAY NIGHT THRU MONDAY...CONTINUED CHANCE FOR RAIN SHOWERS UNTIL
ARCTIC FRONT MOVES SOUTHEAST OF SOUTHERN NEW ENGLAND MONDAY. PRECIP
COULD END AS A BRIEF PERIOD OF SNOW SHOWERS.
MONDAY THROUGH CHRISTMAS DAY...WITH THE ARCTIC FRONT FINALLY MOVES
SOUTHEAST OF SOUTHERN NEW ENGLAND...MODELS CONTINUE TO INDICATE COLD
HIGH PRESSURE BUILDING IN BEHIND THE FRONT WITH SUBSTANTIALLY
COLDER TEMPERATURES FOR CHRISTMAS EVE AND DAY.
THURSDAY...MODELS ARE INDICATING POTENTIAL FOR APPROACH OF A COLD
FRONT FROM THE WEST...WITH SOMEWHAT MILDER AIR MOVING IN AHEAD OF
THE FRONT. WILL HAVE A CHANCE OF RAIN/SNOW SHOWERS LATE THURSDAY
AND THURSDAY NIGHT.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
FORECASTER CONFIDENCE LEVELS...
LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.
NEAR TERM /THROUGH FRIDAY NIGHT/...
HIGH CONFIDENCE VFR TONIGHT...WITH A LOW POTENTIAL FOR SOME MVFR
CONDITIONS IN SHOWERS AND POSSIBLE ICING ACROSS S NH.
FRIDAY AND FRIDAY NIGHT...
HIGH CONFIDENCE IN VFR TOMORROW WITH SOME SHOWERS APPROACHING THE
NW PORTION OF THE REGION BY LATE FRIDAY NIGHT. COULD BE SOME MVFR
MIXED IN WITH THE SHOWERS ESP ACROSS NORTHERN SITES.
KBOS TAF...HIGH CONFIDENCE IN TAF.
KBDL TAF...HIGH CONFIDENCE IN TAF.
OUTLOOK...SATURDAY THROUGH TUESDAY...
SATURDAY...MODERATE CONFIDENCE. MAINLY VFR.
SATURDAY NIGHT THROUGH MONDAY MORNING...LOW CONFIDENCE. MVFR/IFR
CONDITIONS DEVELOP IN MAINLY RAIN SHOWERS. FREEZING RAIN IS
POSSIBLE SATURDAY NIGHT AND SUNDAY MORNING OVER SOUTHERN NEW
HAMPSHIRE.
MONDAY AFTERNOON/EVENING/NIGHT...HIGH CONFIDENCE. IMPROVEMENT TO
VFR BEHIND ARCTIC FRONT. WINDS SHIFT FROM SW TO NW.
TUESDAY...HIGH CONFIDENCE VFR.
&&
.MARINE...
FORECASTER CONFIDENCE LEVELS...
LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.
NEAR TERM /THROUGH FRIDAY NIGHT/...HIGH CONFIDENCE
SW WINDS ARE WEAKENING THIS EVENING AND INTO THE OVERNIGHT. SEAS
WILL ALSO BEGIN TO RELAX AS WELL. ADJUSTED TIMING OF SMALL CRAFT
ADVISORIES TO ACCOUNT FOR CURRENT TRENDS.
LIGHT SW FLOW WILL CONTINUE INTO TOMORROW BUT BEGIN TO PULSE UP BY
TOMORROW NIGHT. SEAS WILL LINGER AROUND 5 FT ESP ACROSS THE
SOUTHERN OUTER WATERS TOMORROW AND INTO TOMORROW NIGHT...
THEREFORE HAVE EXTENDED THE SCA FOR SOME ZONES. DID UNDERCUT SEAS
FOR FRIDAY NIGHT AS THEY SEEMED VERY ROBUST IN A SW FLOW REGIME.
WILL LIKELY NEED TO ISSUE NEW SMALL CRAFT ADVISORIES FOR SOME
ZONES LATER FRIDAY.
OUTLOOK...SATURDAY THROUGH TUESDAY...
SOUTHWESTERLY WINDS WITH PERIODS OF GUSTS 25 TO 30 KTS PERSIST
THROUGH MUCH OF THE LONG TERM. WINDS SHIFT TO THE NORTHWEST AS AN
ARCTIC FRONT MOVES ACROSS THE WATERS MONDAY. WAVES BUILD AND
DIMINISH AS WAVES OF LOW PRESSURE MOVE ALONG AN ARCTIC FRONT THROUGH
NORTHERN NEW ENGLAND BUT GENERALLY REMAIN ABOVE 5 FEET ON THE OUTER
WATERS AT LEAST. SEAS MAY BUILD TO 7 TO 10 FEET ON THE OUTER WATERS
DURING SUN AND SUN NIGHT. MUCH OF THIS TIME WILL LIKELY NEED SMALL
CRAFT ADVISORIES UP FOR AT LEAST THE OUTER WATERS...BUT OVERALL
CONFIDENCE IS LOW ON TIMING.
&&
.CLIMATE...
RECORD HIGHS FOR DECEMBER 22ND...
HARTFORD /BDL/ 59 DEGREES...1990
WORCESTER /ORH/ 63 DEGREES...1923
BOSTON /BOS/ 62 DEGREES...1990
PROVIDENCE /PVD/ 61 DEGREES...1990
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EST SATURDAY FOR ANZ254>256.
SMALL CRAFT ADVISORY UNTIL 2 AM EST FRIDAY FOR ANZ235-237.
&&
$$
SYNOPSIS...DUNTEN
NEAR TERM...BELK/DUNTEN/NMB
SHORT TERM...DUNTEN/NMB
LONG TERM...NMB
AVIATION...DUNTEN/NMB
MARINE...BELK/DUNTEN/NMB
CLIMATE...STAFF
AREA FORECAST DISCUSSION
NWS TAUNTON MA
653 PM EST THU DEC 19 2013
.SYNOPSIS...
DRY WEATHER WILL CONTINUE TONIGHT AND INTO TOMORROW...ISOLATED
SHOWERS ARE POSSIBLE NORTH OF ROUTE 2. A COLD FRONT WILL STALL TO
OUR NORTH TOMORROW. THIS STALLED FRONT WILL RESULT IN PERIODS OF
UNSETTLED WEATHER FRI NIGHT THROUGH EARLY MON. DRIER AND COOLER
WEATHER ARRIVES EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
7 PM UPDATE...
FORECAST REMAINS ON TRACK WITH WINDS CONTINUING TO LIGHTEN AND
A BROKEN CIRRUS CLOUD DECK MOVING THROUGH THE AREA. LATEST SATELLITE
IMAGERY INDICATES THAT CLOUDS WILL CONTINUE TO CROSS OVER
SOUTHERN NEW ENGLAND THIS EVENING.
TONIGHT...
STATIONARY BOUNDARY WILL SET UP ACROSS NORTHERN NEW ENGLAND
TONIGHT AS A RESULT OF AN APPROACHING LOW PRESSURE SYSTEM FROM THE
GREAT LAKES. THIS FRONT WILL ALLOW FOR PRECIP TO DEVELOP ALONG IT
OVERNIGHT AND INTO TOMORROW MORNING. LATEST GUIDANCE KEEPS THIS
FRONT FARTHER NORTH OF THE REGION. HI-RES GUIDANCE AND HRRR KEEP
ALL THE PRECIP NORTH OF THE REGION AS WELL. HOWEVER DID KEEP SOME
LINGERING POPS FOR THE EARLY MORNING HOURS. THIS MAY ALLOW FOR
SOME LIGHT FREEZING RAIN IN THE FAR NORTHERN PORTION OF
FRANKLIN...HILLSBOROUGH AND CHESHIRE COUNTIES. BUT BECAUSE OF THE
LOW CONFIDENCE AND THE FACT THAT HI-RES GUIDANCE KEEPS THIS
PORTION MAINLY DRY DID NOT ISSUE ANY HEADLINES AT THIS TIME.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
FRIDAY INTO FRIDAY NIGHT...
ABOVE AVERAGE TEMPERATURES WILL CONTINUE INTO FRIDAY HOWEVER BY
JUST A FEW DEGREES. INITIALLY THOUGHT THAT TEMPS TOMORROW WILL BE
WELL INTO THE 50S AS WE HIT THE MID 40S TODAY. YET LOOKING AT
SOUNDING DATA APPEARS THAT AN INVERSION WILL BE SET UP OVER THE
REGION. SO WHILE 925 MB TEMPS WILL BE BETWEEN 7C TO 9C...WE MAY BE
IN THE LOW TO UPPER 40S ACROSS THE AREA AT THE SURFACE. THE MAX T
GRID FOR TOMORROW MAY BE TO OPTIMISTIC. A STRAY SHOWER OR TWO MAY
MOVE ACROSS THE REGION TOMORROW AS THE BOUNDARY BEGINS TO SLIDE
SOUTHWARD...BUT OVERALL FEEL MAINLY DRY WEATHER FOR TOMORROW
ESPECIALLY SOUTH OF ROUTE 2.
THAT FRONT WILL SLIDE FARTHER SOUTH AND CLOSER TO THE NW COUNTIES ON
FRIDAY NIGHT INCREASING THE POTENTIAL FOR SOME PRECIP AS A LOW
PRESSURE MOVES ALONG THE BOUNDARY. SURFACE TEMPS WILL BE NEAR OR
ABOVE FREEZING FOR THIS TIMEFRAME SO THE POTENTIAL FOR ICING IS
LESS. THE HIGHEST LOCATION FOR PRECIP TO OCCURS WILL BE REGIONS
NORTH OF ROUTE 2 WITH AN ISOLATED CHANCE NORTH OF THE MASS PIKE.
TEMPERATURES OVERNIGHT WILL ONLY DROP SLIGHTLY AS OVERCAST SKIES AND
WEAK WAA WILL LIMIT RADIATIONAL COOLING.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
* UNSETTLED WEATHER OVER THE WEEKEND
* DRIER...COOLER WEATHER EXPECTED EARLY NEXT WEEK
SATURDAY...COLD FRONT IS NEARLY STATIONARY ACROSS
NORTHERN/CENTRAL NEW ENGLAND EARLY IN THE DAY...WITH MODELS
INDICATING THIS FRONT WILL SLOWLY PUSH SOUTHWARD DURING THE DAY.
LIGHT RAIN SHOWERS POSSIBLE OVER SOUTHERN NH/NORTHERN MA IN THE
MORNING...WITH INCREASING CHANCES FOR RAIN SHOWERS TO THE SOUTH IN
THE AFTERNOON. QPF AMOUNTS EXPECTED TO BE LIGHT.
SATURDAY NIGHT...AGREEMENT BETWEEN THE GFS AND ECMWF THAT FRONT WILL
BECOME DRAPED IN THE VICINITY OF SOUTHERN NH/NORTHERN MA DURING THIS
TIMEFRAME. THERE IS STILL UNCERTAINTY REGARDING THE TEMPERATURE
PROFILE SATURDAY NIGHT AND SUNDAY...BUT THE TREND CONTINUES TO BE
KEEPING MOST OF THE CWA OUT OF THE MUCH COLDER TEMPERATURES AND
FREEZING RAIN. THE MAIN CONCERN AT THIS POINT IS SURFACE
TEMPERATURES IN THE FAR NORTHERN TIER OF THE FORECAST AREA...IN
PARTICULAR SOUTHERN NEW HAMPSHIRE. THERE IS A RISK FOR A PERIOD OF
FREEZING RAIN IN CHESHIRE AND HILLSBOROUGH COUNTIES LATE SATURDAY
NIGHT INTO SUNDAY MORNING...WITH A VERY LOW CHANCE OF FREEZING RAIN
DURING THIS TIMEFRAME OVER EXTREME NORTHERN MA.
SUNDAY...FRONT BEGINS TO PUSH NORTHWARD AS A WARM FRONT DURING THE
DAY...ANY FREEZING PRECIPITATION SHOULD CHANGE OVER TO RAIN SHOWERS
AS THE MORNING PROGRESSES. QPF TOTALS FOR SUNDAY ARE UNCERTAIN FOR
SOUTHERN NEW ENGLAND...EARLY INDICATIONS ARE 0.25 INCH TO AN
INCH...BUT IN ADDITION TO THIS RAIN THERE WILL BE SNOWMELT. ACROSS
MOST OF MASSACHUSETTS...AS WELL AS N CT AND RI...SURFACE DEWPOINTS
ARE EXPECTED TO CLIMB INTO THE 50S. HIGH TEMPERATURES MAY REACH MID
50S TO AROUND 60. THIS WITH A 10 TO 15 MPH SOUTHERLY SURFACE WIND
WILL PROMPT CONSIDERABLE SNOWMELT. THE SNOWMELT ALONG WITH
MODERATE QPF COULD CAUSE FLOODING IN LOW LYING AND POOR DRAINAGE
AREAS. ANY DRAINS THAT ARE SNOW CLOGGED COULD POSE A FLOOD RISK.
SUNDAY NIGHT THRU MONDAY...CONTINUED CHANCE FOR RAIN SHOWERS UNTIL
ARCTIC FRONT MOVES SOUTHEAST OF SOUTHERN NEW ENGLAND MONDAY. PRECIP
COULD END AS A BRIEF PERIOD OF SNOW SHOWERS.
MONDAY THROUGH CHRISTMAS DAY...WITH THE ARCTIC FRONT FINALLY MOVES
SOUTHEAST OF SOUTHERN NEW ENGLAND...MODELS CONTINUE TO INDICATE COLD
HIGH PRESSURE BUILDING IN BEHIND THE FRONT WITH SUBSTANTIALLY
COLDER TEMPERATURES FOR CHRISTMAS EVE AND DAY.
THURSDAY...MODELS ARE INDICATING POTENTIAL FOR APPROACH OF A COLD
FRONT FROM THE WEST...WITH SOMEWHAT MILDER AIR MOVING IN AHEAD OF
THE FRONT. WILL HAVE A CHANCE OF RAIN/SNOW SHOWERS LATE THURSDAY
AND THURSDAY NIGHT.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
FORECASTER CONFIDENCE LEVELS...
LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.
NEAR TERM /THROUGH FRIDAY NIGHT/...
HIGH CONFIDENCE VFR TONIGHT...WITH A LOW POTENTIAL FOR SOME MVFR
CONDITIONS IN SHOWERS AND POSSIBLE ICING ACROSS S NH.
FRIDAY AND FRIDAY NIGHT...
HIGH CONFIDENCE IN VFR TOMORROW WITH SOME SHOWERS APPROACHING THE
NW PORTION OF THE REGION BY LATE FRIDAY NIGHT. COULD BE SOME MVFR
MIXED IN WITH THE SHOWERS ESP ACROSS NORTHERN SITES.
KBOS TAF...HIGH CONFIDENCE IN TAF.
KBDL TAF...HIGH CONFIDENCE IN TAF.
OUTLOOK...SATURDAY THROUGH TUESDAY...
SATURDAY...MODERATE CONFIDENCE. MAINLY VFR.
SATURDAY NIGHT THROUGH MONDAY MORNING...LOW CONFIDENCE. MVFR/IFR
CONDITIONS DEVELOP IN MAINLY RAIN SHOWERS. FREEZING RAIN IS
POSSIBLE SATURDAY NIGHT AND SUNDAY MORNING OVER SOUTHERN NEW
HAMPSHIRE.
MONDAY AFTERNOON/EVENING/NIGHT...HIGH CONFIDENCE. IMPROVEMENT TO
VFR BEHIND ARCTIC FRONT. WINDS SHIFT FROM SW TO NW.
TUESDAY...HIGH CONFIDENCE VFR.
&&
.MARINE...
FORECASTER CONFIDENCE LEVELS...
LOW...LESS THAN 30 PERCENT.
MODERATE...30 TO 60 PERCENT.
HIGH...GREATER THAN 60 PERCENT.
NEAR TERM /THROUGH FRIDAY NIGHT/...HIGH CONFIDENCE
SW WINDS ARE WEAKENING THIS EVENING AND INTO THE OVERNIGHT. SEAS
WILL ALSO BEGIN TO RELAX AS WELL.
LIGHT SW FLOW WILL CONTINUE INTO TOMORROW BUT BEGIN TO PULSE UP BY
TOMORROW NIGHT. SEAS WILL LINGER AROUND 5 FT ESP ACROSS THE
SOUTHERN OUTER WATERS TOMORROW AND INTO TOMORROW
NIGHT...THEREFORE HAVE EXTENDED THE SCA. DID UNDERCUT SEAS FOR
FRIDAY NIGHT AS THEY SEEMED VERY ROBUST IN A SW FLOW REGIME.
OUTLOOK...SATURDAY THROUGH TUESDAY...
SOUTHWESTERLY WINDS WITH PERIODS OF GUSTS 25 TO 30 KTS PERSIST
THROUGH MUCH OF THE LONG TERM. WINDS SHIFT TO THE NORTHWEST AS AN
ARCTIC FRONT MOVES ACROSS THE WATERS MONDAY. WAVES BUILD AND
DIMINISH AS WAVES OF LOW PRESSURE MOVE ALONG AN ARCTIC FRONT THROUGH
NORTHERN NEW ENGLAND BUT GENERALLY REMAIN ABOVE 5 FEET ON THE OUTER
WATERS AT LEAST. SEAS MAY BUILD TO 7 TO 10 FEET ON THE OUTER WATERS
DURING SUN AND SUN NIGHT. MUCH OF THIS TIME WILL LIKELY NEED SMALL
CRAFT ADVISORIES UP FOR AT LEAST THE OUTER WATERS...BUT OVERALL
CONFIDENCE IS LOW ON TIMING.
&&
.CLIMATE...
RECORD HIGHS FOR DECEMBER 22ND...
HARTFORD /BDL/ 59 DEGREES...1990
WORCESTER /ORH/ 63 DEGREES...1923
BOSTON /BOS/ 62 DEGREES...1990
PROVIDENCE /PVD/ 61 DEGREES...1990
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
MA...NONE.
NH...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EST THIS EVENING FOR
ANZ231>234-251.
SMALL CRAFT ADVISORY UNTIL 6 AM EST FRIDAY FOR ANZ235-237.
SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR ANZ250.
SMALL CRAFT ADVISORY UNTIL 7 AM EST SATURDAY FOR ANZ254>256.
&&
$$
SYNOPSIS...DUNTEN
NEAR TERM...DUNTEN/NMB
SHORT TERM...DUNTEN/NMB
LONG TERM...NMB
AVIATION...DUNTEN/NMB
MARINE...DUNTEN/NMB
CLIMATE...STAFF
AREA FORECAST DISCUSSION
NWS ALBANY NY
100 PM EST WED DEC 18 2013
.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE CROSSING THE REGION WILL
BRING SCATTERED SNOW SHOWERS AND FLURRIES INTO THE EARLY AFTERNOON.
LAKE EFFECT SNOW SHOWERS OR SNOW SQUALLS WILL IMPACT PORTIONS OF THE
WESTERN ADIRONDACKS THIS AFTERNOON AND TONIGHT. HIGH PRESSURE WILL
BUILD IN FROM THE SOUTHWEST FOR THURSDAY...BRINGING MILDER
TEMPERATURES...AND DRY CONDITIONS. A FRONTAL SYSTEM APPROACHING FROM
THE WEST AND NORTH WILL BRING CLOUDS...ALONG WITH SOME SNOW AND RAIN
SHOWERS FOR THURSDAY NIGHT INTO FRIDAY. A MORE SIGNIFICANT STORM
SYSTEM MAY BRING WIDESPREAD PRECIPITATION FOR A PORTION OF THE
UPCOMING WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 1230 PM EST...DECIDED TO BEGIN THE LAKE EFFECT ADVISORY EARLY
AS THE LAKE BAND OFF ONTARIO HAS RAMPED IN THE PAST HOUR. OTHERWISE
NO REAL OTHER CHANGES.
TEMPERATURES STILL QUITE COLD IN VALLEY AREAS AS MIXING HAS NOT BEEN
REALIZED. FEEL PRUDENT TO LOWER MANY VALLEY LOCATIONS ABOUT A
CATEGORY BUT KEPT HIGHER ELEVATIONS ABOUT THE SAME.
CLOUDS WILL MIX WITH SUNSHINE...MORE SUNSHINE TO THE SOUTH OF THE
CAPITAL DISTRICT.
LOOK FOR HIGHS GENERALLY 25 TO 30 TO ALBANY SOUTHWARD...20 TO 25
NORTHWARD. LOOK FOR WIDELY SCATTERED SNOW SHOWERS ACROSS MUCH OF THE
REGION...WITH LITTLE OR NO ACCUMULATIONS...OUTSIDE OF THE ADIRONDACK
PARK WHERE SOME IS LIKELY LATER THIS AFTERNOON AS THE LAKE MACHINE
RAMPS UP.
THE WIND WILL BECOME WESTERLY 5 TO 15 MPH ACROSS THE REGION.
THE LATEST RUC CONTINUED TO SHOW THE H500 TROUGH AXIS...AND ITS
ASSOCIATED MID LEVEL SHORT-WAVE MOVING ACROSS WRN NEW ENGLAND. SOME
SCT SNOW SHOWER AND FLURRIES HAVE OCCURRED FROM THE CAPITAL REGION
NORTH AND WEST...AND ESPECIALLY ALONG THE SPINE OF THE SRN
GREENS...N-CNTRL TACONICS...AND BERKSHIRES. SOME SLIGHT AND LOW CHC
POPS HAVE BEEN KEPT IN THE FORECAST INTO THE EARLY PM. MOSTLY CLOUDY
CONDITIONS PERSIST NORTH OF THE MID HUDSON VALLEY AND NW CT. FURTHER
UPSTREAM...DIFFUSE LAKE EFFECT ACTIVITY IS SETTING UP JUST DOWN
STREAM OF LAKE ONTARIO. THIS ACTIVITY SHOULD ORGANIZE BETTER IN THE
EARLY PM...AND THE LAKE EFFECT SNOW ADVISORY BEGINS FOR NRN HERKIMER
AND HAMILTON COUNTIES AT 3 PM. CURRENT FORECAST TRENDS LOOK SIMILAR
FOR 3 TO 6 INCHES OF HIGH RATIO SNOWFALL. THE FORECAST TREND LOOKS
SIMILAR FOR THE LAKE POTENTIAL BELOW.
THE LAKE RESPONSE WILL DEVELOP IN THE PM...AS COOLING WITHIN THE
850-700 MB LAYER COMBINES WITH AN INCREASING LOW LEVEL FLOW OVER
WATER TRAJECTORY ACROSS LAKE ONTARIO...WITH SOME ADDITIONAL
MOISTENING FROM LAKE HURON. IT APPEARS THAT THE LAKE EFFECT
POTENTIAL FOR SINGLE SNOWBANDS WILL BE FOR A SOMEWHAT SHORT
DURATION...MAINLY AFTER NOON TODAY...THROUGH AT LEAST 6 PM EST.
EXPECT SEVERAL INCHES OF SNOW ACROSS PORTIONS OF NORTHERN HERKIMER
CO...AND POSSIBLY EXTENDING INTO PORTIONS OF WEST CENTRAL AND
NORTHWEST HAMILTON CO...MAINLY THIS AFTERNOON. SOME EXTENSION OF A
SNOWBAND MAY ALSO IMPACT PORTIONS OF THE MOHAWK VALLEY/WRN CAPITAL
REGION EARLY THIS THIS AFTERNOON...WITH MINOR ACCUMS POSSIBLE.
ENHANCED UPSLOPE ACROSS PORTIONS OF SOUTHERN VT COULD ALSO LEAD TO
A COUPLE INCHES OF SNOWFALL ACROSS EASTERN PORTIONS OF BENNINGTON
CO AND WEST CENTRAL WINDHAM CO THIS AFTERNOON.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
TONIGHT...THE AFOREMENTIONED SNOWBAND WILL LIKELY BE ONGOING THIS
EVENING ACROSS THE ADVISORY AREA...AND LIFTING
NORTHWARD...IMPACTING AREAS NEAR AND NORTH OF ROUTE 28. LATER
TONIGHT...IT APPEARS THAT THE BAND SHOULD WEAKEN AS THE INVERSION
LEVEL DROPS RAPIDLY...AND LOW LEVEL DIRECTIONAL SHEAR INCREASES
AND DISRUPTS SINGLE BAND POTENTIAL. ELSEWHERE...EXPECT PARTLY
CLOUDY SKIES...ALTHOUGH SOME PERIODS OF MOSTLY CLEAR SKIES WILL BE
POSSIBLE. GIVEN OUR DEEP...FRESH SNOWPACK...ANY BREAKS IN THE
CLOUDS WILL ALLOW TEMPS TO QUICKLY DROP. HAVE THEREFORE WENT BELOW
THE COLDEST GUIDANCE...WITH MAINLY SINGLE DIGITS AND TEENS
EXPECTED. SHOULD BREAKS IN THE CLOUDS BE MORE WIDESPREAD AND/OR
LONGER IN DURATION...EVEN COLDER MIN TEMPS WOULD BE POSSIBLE.
THU...LOW AND MID LEVEL WARM ADVECTION DEVELOPS AND STRENGTHENS.
AS MILDER AND INCREASINGLY MOIST AIR MOVES OVER THE VERY COLD
GROUND AND DEEP SNOW COVER...IT APPEARS THAT A LOW LEVEL INVERSION
WILL DEVELOP...LEADING TO MOSTLY CLOUDY SKIES FOR AT LEAST THE
NORTHERN THIRD OF THE REGION...WITH OCCASIONAL CLOUDS TO THE
SOUTH. FOR MAX TEMPS...HAVE SIDED WITH THE COOLER OF THE MAV/MET
MOS...WITH GENERALLY 30S EXPECTED FOR VALLEY AREAS...AND 20S TO
AROUND 30 FOR HIGHER ELEVATIONS.
THU NT-FRI NT...A FRONTAL BOUNDARY WILL GRADUALLY APPROACH FROM
THE N AND W...AS WAVES OF LOW PRESSURE TRAVEL ALONG IT. SEVERAL
SURGES OF ISENTROPIC LIFT WILL IMPACT THE REGION...ESP NORTHERN
AND CENTRAL AREAS. IT APPEARS THAT THE BEST CHC FOR PRECIP WILL BE
LATE THU NT INTO FRI EVENING. WARMING ALOFT COULD ALLOW FOR SOME
MIXED PRECIP TO OCCUR ACROSS NORTHERN AREAS THU NT...AND AGAIN FRI
NT...AND WILL HAVE TO WATCH MODEL TRENDS AND LOW LEVEL THERMAL
PROFILES. QPF LOOKS LIGHT AT THIS TIME...BUT CAN NOT RULE OUT SOME
AREAS OF LIGHT ICING...ESP FRI NT ACROSS PORTIONS OF THE SOUTHERN
ADIRONDACKS AND WESTERN MOHAWK VALLEY. HAVE SIDED WITH...OR WENT
BELOW THE COOLER MAV/MET...WITH NIGHTTIME MINS FALLING INTO THE
20S IN MOST AREAS...AND MAX TEMPS RANGING FROM THE UPPER 20S TO
MID 30S ACROSS NORTHERN AREAS...AND MID 30S TO MID 40S ACROSS
SOUTHERN AREAS.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
STILL DECENT AGREEMENT IN GUIDANCE AND ENSEMBLES FOR A STRONG WARM
ADVECTION EVENT THAT SHOULD RESULT IN MORE RAIN THAN WINTRY
PRECIPITATION. ONE SYSTEM WILL BE EXITING THROUGH SATURDAY MORNING
WITH JUST SCATTERED RAIN AND SNOW SHOWERS ENDING. THE NEXT
SYSTEM...WITH SOUTHERN STREAM ORIGINS...SPREADS MOSTLY RAIN OVER
MUCH OF THE REGION SATURDAY AFTERNOON...STARTING AS A MIX IN THE
SOUTHERN ADIRONDACKS. THERE COULD BE MINOR TO MODERATE ACCUMULATIONS
OF MIXED PRECIPITATION...INCLUDING POSSIBLY FREEZING RAIN...IN THE
SOUTHERN ADIRONDACKS THROUGH SATURDAY NIGHT BEFORE PRECIPITATION
TURNS TO RAIN SUNDAY MORNING.
THIS COULD BE A PROLONGED EVENT...WITH A VERY STRONG WEST
SOUTHWESTERLY BOUNDARY LAYER JET AND DEEP MOISTURE...ALONG WITH
STRONG ISENTROPIC LIFT WITHIN THE WARM ADVECTION...AND STRONG
FRONTOGENESIS ALONG THE COLD FRONT. THERE COULD BE ENOUGH RAIN FOR
SOME POTENTIAL RUN OFF PROBLEMS WHEN COMBINED WITH SNOW MELT. THE
AXIS OF HEAVIEST RAIN LOOKS TO BE ALONG AND NORTH OF THE SCHOHARIE
VALLEY...SOUTHERN ADIRONDACKS...HELDERBERGS TO THE LAKE GEORGE
SARATOGA REGION...SOUTHERN GREEN MOUNTAINS AND BERKSHIRES. SOME
INDICATIONS ARE THAT THE HEAVIEST RAIN COULD BE MOSTLY THE EXTREME
NORTHERN SECTIONS OF THE FORECAST AREA...SO THERE IS CONSIDERABLE
UNCERTAINTY ON WHERE THE HEAVIEST RAIN COULD FALL. THE POTENTIAL FOR
HEAVY RAIN...SNOW MELT AND RUN OFF WILL BE ADDRESSED IN THE HWO.
HIGHS SATURDAY IN THE 40S...MID TO UPPER 30S SOUTHERN ADIRONDACKS
AND SOUTHERN GREEN MOUNTAINS. HIGHS SUNDAY IN THE LOWER TO MID
50S...WITH 40S IN HIGHER ELEVATIONS...AROUND 40 SOUTHERN
ADIRONDACKS. THE FRONT TRACKS THROUGH SUNDAY NIGHT AND EARLY MONDAY
WITH DEEP COLD ADVECTION SPREADING ACROSS OUR REGION. HIGHS MONDAY
IN THE LOWER TO MID 30S...WITH UPPER 20S IN THE SOUTHERN ADIRONDACKS
AND SOUTHERN GREEN MOUNTAINS. COLD ADVECTION CONTINUES TUESDAY WITH
HIGHS IN THE 20S...UPPER TEENS IN THE SOUTHERN ADIRONDACKS. THERE
COULD BE LAKE EFFECT SNOW BANDS MONDAY INTO TUESDAY BUT THE INLAND
EXTENT IS IN QUESTION.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
A WEAK WARM FRONT WILL MOVE NORTH OF THE REGION THIS AFTERNOON. HIGH
PRESSURE WILL RIDGE IN FROM THE MID ATLANTIC REGION TONIGHT INTO
EARLY TOMORROW AFTERNOON.
IN THE MOIST CYCLONIC FLOW ALOFT OCCASIONAL CLOUDS CONTINUE TO
IMPACT THE TERMINALS FROM KALB AND KPSF NORTHWARD TO KGFL. ALSO A
WEAK WARM FRONT IS LIFTING THROUGH THESE AREAS. SOME OF THE CLOUDS
HAVE BEEN IN THE HIGH MVFR RANGE AT THESE SITES. THESE MVFR CLOUDS
WILL BE POSSIBLE UNTIL THE LATE AFTERNOON/EARLY EVENING ESPECIALLY
AT KGFL. FURTHER SOUTH...ONLY HIGH CLOUDS HAVE BEEN PERSISTING NEAR
KPOU. VFR CONDITIONS ARE EXPECTED TO RETURN TO ALL THE TAF SITES
THIS EVENING WITH LINGERING STRATOCUMULUS...TRANSITIONING TO MID AND
HIGH CLOUDS WITH THE WARM ADVECTION OCCURRING ALOFT...AS THE SFC
RIDGE ATTEMPTS TO BUILD IN. EXPECT WIDESPREAD MID LEVEL AND HIGH
CLOUDS IN THE LATE MORNING FOR KGFL/KALB/KPOU/KPSF.
THE WINDS WILL BE LIGHT FROM THE SOUTH TO SOUTHWEST AT LESS THAN 7
KTS INITIALLY...AND THEN WILL VEER TO THE WEST AT AROUND 10 KTS WITH
SOME GUSTS CLOSER 20 KTS AT KALB IN THE LATE PM. THE WINDS WILL
THEN BACK TO THE SOUTH TO SOUTHWEST EARLY THIS EVENING AT 5 TO 10
KTS. EXPECT THE SOUTH TO SOUTHWEST WINDS TO CONTINUE AT AROUND 10
KTS WITH GUSTS CLOSER TO 20 KTS AT KALB.
OUTLOOK...
THURSDAY PM...NO OPERATIONAL IMPACT. NO SIG WX.
THURSDAY NIGHT: LOW OPERATIONAL IMPACT. SLIGHT CHANCE OF SHSN.
FRIDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...SHSN.
FRIDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...SHSN.
SATURDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...RA.
SATURDAY NIGHT: HIGH OPERATIONAL IMPACT. LIKELY RA.
SUNDAY: HIGH OPERATIONAL IMPACT. LIKELY RA.
SUNDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF RA.
MONDAY: MODERATE OPERATIONAL IMPACT. SCATTERED SHRA...SHSN.
&&
.HYDROLOGY...
LAKE EFFECT SNOWBANDS...AND SCATTERED SNOW SHOWERS WILL BE
POSSIBLE TODAY AND TONIGHT...WITH MAXIMUM TOTAL LIQUID EQUIVALENT
GENERALLY REMAINING UNDER ONE QUARTER OF AN INCH...WHICH WOULD BE
ACROSS THE WESTERN ADIRONDACKS.
OTHERWISE...THROUGH TONIGHT...TEMPS WILL CONTINUE TO BE BELOW
NORMAL AND ICE WILL CONTINUE TO FORM AND THICKEN ON AREA
RIVERS...STREAMS AND PARTICULARLY LAKES.
A MODERATING TREND IN TEMPS IS LIKELY THU INTO FRI...WITH A
FRONTAL BOUNDARY BRINGING SOME SHOWERS TO CLOSE THE WORK WEEK.
SOME SNOW MELT IS LIKELY THIS WEEKEND. ALSO...A STORM SYSTEM
MOVING ALONG A FRONTAL BOUNDARY MAY BRING SIGNIFICANT PCPN TO THE
FORECAST AREA SAT NIGHT INTO SUNDAY WITH EVEN MILDER TEMPS. THIS
WILL CONTINUE TO BE MONITORED FOR THE UPCOMING WEEKEND FOR THE
POSSIBILITY OF SOME HYDRO ISSUES.
FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED
AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...LAKE EFFECT SNOW ADVISORY UNTIL 6 AM EST THURSDAY FOR NYZ032-
033.
MA...NONE.
VT...NONE.
&&
$$
SYNOPSIS...KL/WASULA
NEAR TERM...HWJIV/KL/WASULA
SHORT TERM...KL
LONG TERM...NAS
AVIATION...WASULA
HYDROLOGY...KL/WASULA
AREA FORECAST DISCUSSION
NWS ALBANY NY
1230 PM EST WED DEC 18 2013
.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE CROSSING THE REGION WILL
BRING SCATTERED SNOW SHOWERS AND FLURRIES INTO THE EARLY AFTERNOON.
LAKE EFFECT SNOW SHOWERS OR SNOW SQUALLS WILL IMPACT PORTIONS OF THE
WESTERN ADIRONDACKS THIS AFTERNOON AND TONIGHT. HIGH PRESSURE WILL
BUILD IN FROM THE SOUTHWEST FOR THURSDAY...BRINGING MILDER
TEMPERATURES...AND DRY CONDITIONS. A FRONTAL SYSTEM APPROACHING FROM
THE WEST AND NORTH WILL BRING CLOUDS...ALONG WITH SOME SNOW AND RAIN
SHOWERS FOR THURSDAY NIGHT INTO FRIDAY. A MORE SIGNIFICANT STORM
SYSTEM MAY BRING WIDESPREAD PRECIPITATION FOR A PORTION OF THE
UPCOMING WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 1230 PM EST...DECIDED TO BEGIN THE LAKE EFFECT ADVISORY EARLY
AS THE LAKE BAND OFF ONTARIO HAS RAMPED IN THE PAST HOUR. OTHERWISE
NO REAL OTHER CHANGES.
TEMPERATURES STILL QUITE COLD IN VALLEY AREAS AS MIXING HAS NOT BEEN
REALIZED. FEEL PRUDENT TO LOWER MANY VALLEY LOCATIONS ABOUT A
CATEGORY BUT KEPT HIGHER ELEVATIONS ABOUT THE SAME.
CLOUDS WILL MIX WITH SUNSHINE...MORE SUNSHINE TO THE SOUTH OF THE
CAPITAL DISTRICT.
LOOK FOR HIGHS GENERALLY 25 TO 30 TO ALBANY SOUTHWARD...20 TO 25
NORTHWARD. LOOK FOR WIDELY SCATTERED SNOW SHOWERS ACROSS MUCH OF THE
REGION...WITH LITTLE OR NO ACCUMULATIONS...OUTSIDE OF THE ADIRONDACK
PARK WHERE SOME IS LIKELY LATER THIS AFTERNOON AS THE LAKE MACHINE
RAMPS UP.
THE WIND WILL BECOME WESTERLY 5 TO 15 MPH ACROSS THE REGION.
THE LATEST RUC CONTINUED TO SHOW THE H500 TROUGH AXIS...AND ITS
ASSOCIATED MID LEVEL SHORT-WAVE MOVING ACROSS WRN NEW ENGLAND. SOME
SCT SNOW SHOWER AND FLURRIES HAVE OCCURRED FROM THE CAPITAL REGION
NORTH AND WEST...AND ESPECIALLY ALONG THE SPINE OF THE SRN
GREENS...N-CNTRL TACONICS...AND BERKSHIRES. SOME SLIGHT AND LOW CHC
POPS HAVE BEEN KEPT IN THE FORECAST INTO THE EARLY PM. MOSTLY CLOUDY
CONDITIONS PERSIST NORTH OF THE MID HUDSON VALLEY AND NW CT. FURTHER
UPSTREAM...DIFFUSE LAKE EFFECT ACTIVITY IS SETTING UP JUST DOWN
STREAM OF LAKE ONTARIO. THIS ACTIVITY SHOULD ORGANIZE BETTER IN THE
EARLY PM...AND THE LAKE EFFECT SNOW ADVISORY BEGINS FOR NRN HERKIMER
AND HAMILTON COUNTIES AT 3 PM. CURRENT FORECAST TRENDS LOOK SIMILAR
FOR 3 TO 6 INCHES OF HIGH RATIO SNOWFALL. THE FORECAST TREND LOOKS
SIMILAR FOR THE LAKE POTENTIAL BELOW.
THE LAKE RESPONSE WILL DEVELOP IN THE PM...AS COOLING WITHIN THE
850-700 MB LAYER COMBINES WITH AN INCREASING LOW LEVEL FLOW OVER
WATER TRAJECTORY ACROSS LAKE ONTARIO...WITH SOME ADDITIONAL
MOISTENING FROM LAKE HURON. IT APPEARS THAT THE LAKE EFFECT
POTENTIAL FOR SINGLE SNOWBANDS WILL BE FOR A SOMEWHAT SHORT
DURATION...MAINLY AFTER NOON TODAY...THROUGH AT LEAST 6 PM EST.
EXPECT SEVERAL INCHES OF SNOW ACROSS PORTIONS OF NORTHERN HERKIMER
CO...AND POSSIBLY EXTENDING INTO PORTIONS OF WEST CENTRAL AND
NORTHWEST HAMILTON CO...MAINLY THIS AFTERNOON. SOME EXTENSION OF A
SNOWBAND MAY ALSO IMPACT PORTIONS OF THE MOHAWK VALLEY/WRN CAPITAL
REGION EARLY THIS THIS AFTERNOON...WITH MINOR ACCUMS POSSIBLE.
ENHANCED UPSLOPE ACROSS PORTIONS OF SOUTHERN VT COULD ALSO LEAD TO
A COUPLE INCHES OF SNOWFALL ACROSS EASTERN PORTIONS OF BENNINGTON
CO AND WEST CENTRAL WINDHAM CO THIS AFTERNOON.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
TONIGHT...THE AFOREMENTIONED SNOWBAND WILL LIKELY BE ONGOING THIS
EVENING ACROSS THE ADVISORY AREA...AND LIFTING
NORTHWARD...IMPACTING AREAS NEAR AND NORTH OF ROUTE 28. LATER
TONIGHT...IT APPEARS THAT THE BAND SHOULD WEAKEN AS THE INVERSION
LEVEL DROPS RAPIDLY...AND LOW LEVEL DIRECTIONAL SHEAR INCREASES
AND DISRUPTS SINGLE BAND POTENTIAL. ELSEWHERE...EXPECT PARTLY
CLOUDY SKIES...ALTHOUGH SOME PERIODS OF MOSTLY CLEAR SKIES WILL BE
POSSIBLE. GIVEN OUR DEEP...FRESH SNOWPACK...ANY BREAKS IN THE
CLOUDS WILL ALLOW TEMPS TO QUICKLY DROP. HAVE THEREFORE WENT BELOW
THE COLDEST GUIDANCE...WITH MAINLY SINGLE DIGITS AND TEENS
EXPECTED. SHOULD BREAKS IN THE CLOUDS BE MORE WIDESPREAD AND/OR
LONGER IN DURATION...EVEN COLDER MIN TEMPS WOULD BE POSSIBLE.
THU...LOW AND MID LEVEL WARM ADVECTION DEVELOPS AND STRENGTHENS.
AS MILDER AND INCREASINGLY MOIST AIR MOVES OVER THE VERY COLD
GROUND AND DEEP SNOW COVER...IT APPEARS THAT A LOW LEVEL INVERSION
WILL DEVELOP...LEADING TO MOSTLY CLOUDY SKIES FOR AT LEAST THE
NORTHERN THIRD OF THE REGION...WITH OCCASIONAL CLOUDS TO THE
SOUTH. FOR MAX TEMPS...HAVE SIDED WITH THE COOLER OF THE MAV/MET
MOS...WITH GENERALLY 30S EXPECTED FOR VALLEY AREAS...AND 20S TO
AROUND 30 FOR HIGHER ELEVATIONS.
THU NT-FRI NT...A FRONTAL BOUNDARY WILL GRADUALLY APPROACH FROM
THE N AND W...AS WAVES OF LOW PRESSURE TRAVEL ALONG IT. SEVERAL
SURGES OF ISENTROPIC LIFT WILL IMPACT THE REGION...ESP NORTHERN
AND CENTRAL AREAS. IT APPEARS THAT THE BEST CHC FOR PRECIP WILL BE
LATE THU NT INTO FRI EVENING. WARMING ALOFT COULD ALLOW FOR SOME
MIXED PRECIP TO OCCUR ACROSS NORTHERN AREAS THU NT...AND AGAIN FRI
NT...AND WILL HAVE TO WATCH MODEL TRENDS AND LOW LEVEL THERMAL
PROFILES. QPF LOOKS LIGHT AT THIS TIME...BUT CAN NOT RULE OUT SOME
AREAS OF LIGHT ICING...ESP FRI NT ACROSS PORTIONS OF THE SOUTHERN
ADIRONDACKS AND WESTERN MOHAWK VALLEY. HAVE SIDED WITH...OR WENT
BELOW THE COOLER MAV/MET...WITH NIGHTTIME MINS FALLING INTO THE
20S IN MOST AREAS...AND MAX TEMPS RANGING FROM THE UPPER 20S TO
MID 30S ACROSS NORTHERN AREAS...AND MID 30S TO MID 40S ACROSS
SOUTHERN AREAS.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
STILL DECENT AGREEMENT IN GUIDANCE AND ENSEMBLES FOR A STRONG WARM
ADVECTION EVENT THAT SHOULD RESULT IN MORE RAIN THAN WINTRY
PRECIPITATION. ONE SYSTEM WILL BE EXITING THROUGH SATURDAY MORNING
WITH JUST SCATTERED RAIN AND SNOW SHOWERS ENDING. THE NEXT
SYSTEM...WITH SOUTHERN STREAM ORIGINS...SPREADS MOSTLY RAIN OVER
MUCH OF THE REGION SATURDAY AFTERNOON...STARTING AS A MIX IN THE
SOUTHERN ADIRONDACKS. THERE COULD BE MINOR TO MODERATE ACCUMULATIONS
OF MIXED PRECIPITATION...INCLUDING POSSIBLY FREEZING RAIN...IN THE
SOUTHERN ADIRONDACKS THROUGH SATURDAY NIGHT BEFORE PRECIPITATION
TURNS TO RAIN SUNDAY MORNING.
THIS COULD BE A PROLONGED EVENT...WITH A VERY STRONG WEST
SOUTHWESTERLY BOUNDARY LAYER JET AND DEEP MOISTURE...ALONG WITH
STRONG ISENTROPIC LIFT WITHIN THE WARM ADVECTION...AND STRONG
FRONTOGENESIS ALONG THE COLD FRONT. THERE COULD BE ENOUGH RAIN FOR
SOME POTENTIAL RUN OFF PROBLEMS WHEN COMBINED WITH SNOW MELT. THE
AXIS OF HEAVIEST RAIN LOOKS TO BE ALONG AND NORTH OF THE SCHOHARIE
VALLEY...SOUTHERN ADIRONDACKS...HELDERBERGS TO THE LAKE GEORGE
SARATOGA REGION...SOUTHERN GREEN MOUNTAINS AND BERKSHIRES. SOME
INDICATIONS ARE THAT THE HEAVIEST RAIN COULD BE MOSTLY THE EXTREME
NORTHERN SECTIONS OF THE FORECAST AREA...SO THERE IS CONSIDERABLE
UNCERTAINTY ON WHERE THE HEAVIEST RAIN COULD FALL. THE POTENTIAL FOR
HEAVY RAIN...SNOW MELT AND RUN OFF WILL BE ADDRESSED IN THE HWO.
HIGHS SATURDAY IN THE 40S...MID TO UPPER 30S SOUTHERN ADIRONDACKS
AND SOUTHERN GREEN MOUNTAINS. HIGHS SUNDAY IN THE LOWER TO MID
50S...WITH 40S IN HIGHER ELEVATIONS...AROUND 40 SOUTHERN
ADIRONDACKS. THE FRONT TRACKS THROUGH SUNDAY NIGHT AND EARLY MONDAY
WITH DEEP COLD ADVECTION SPREADING ACROSS OUR REGION. HIGHS MONDAY
IN THE LOWER TO MID 30S...WITH UPPER 20S IN THE SOUTHERN ADIRONDACKS
AND SOUTHERN GREEN MOUNTAINS. COLD ADVECTION CONTINUES TUESDAY WITH
HIGHS IN THE 20S...UPPER TEENS IN THE SOUTHERN ADIRONDACKS. THERE
COULD BE LAKE EFFECT SNOW BANDS MONDAY INTO TUESDAY BUT THE INLAND
EXTENT IS IN QUESTION.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
MAINLY VFR CONDITIONS THIS AFTERNOON AT THE TAF SITES...BUT
OCCASIONAL MVFR THIS AFTERNOON AT KPSF.
AN UPPER LEVEL DISTURBANCE TRACKING THROUGH THE REGION WILL BRING
PERIODS OF BROKEN CEILINGS ABOVE 3000 FEET THROUGH THE DAY. THERE
COULD BE SOME FLURRIES THIS MORNING SO WILL PUT VCSH FOR A FEW HOURS
AT KALB...KPSF...AND KGFL. AT THE SURFACE...HIGH PRESSURE WILL
BUILD IN. SCATTERED VARIABLE BROKEN CEILINGS ABOVE 3000 FEET SHOULD
CONTINUE THROUGH TONIGHT MAINLY AT KALB...KPSF AND KGFL BUT JUST
SCATTERED AT KPOU.
WINDS WILL BE LIGHT TO CALM THROUGH THE EARLY MORNING HOURS BECOMING
WESTERLY DURING THE LATE MORNING AND INCREASING TO 6 TO 10 KNOTS.
SOME GUSTS INTO THE TEENS ARE EXPECTED AT KALB AND KPSF FROM LATE
MORNING THROUGH THE MID AFTERNOON...AND SHOULD CONTINUE INTO THE
EVENING. WINDS SHOULD DECREASE TO 5 KT OR LESS LATER THIS EVENING
AND CONTINUE THROUGH THE NIGHT.
OUTLOOK...
THURSDAY NIGHT: LOW OPERATIONAL IMPACT. SLIGHT CHANCE OF SHSN.
FRIDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...SHSN.
FRIDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...SHSN.
SATURDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...RA.
SATURDAY NIGHT: HIGH OPERATIONAL IMPACT. LIKELY RA.
SUNDAY: HIGH OPERATIONAL IMPACT. LIKELY RA.
&&
.HYDROLOGY...
LAKE EFFECT SNOWBANDS...AND SCATTERED SNOW SHOWERS WILL BE
POSSIBLE TODAY AND TONIGHT...WITH MAXIMUM TOTAL LIQUID EQUIVALENT
GENERALLY REMAINING UNDER ONE QUARTER OF AN INCH...WHICH WOULD BE
ACROSS THE WESTERN ADIRONDACKS.
OTHERWISE...THROUGH TONIGHT...TEMPS WILL CONTINUE TO BE BELOW
NORMAL AND ICE WILL CONTINUE TO FORM AND THICKEN ON AREA
RIVERS...STREAMS AND PARTICULARLY LAKES.
A MODERATING TREND IN TEMPS IS LIKELY THU INTO FRI...WITH A
FRONTAL BOUNDARY BRINGING SOME SHOWERS TO CLOSE THE WORK WEEK.
SOME SNOW MELT IS LIKELY THIS WEEKEND. ALSO...A STORM SYSTEM
MOVING ALONG A FRONTAL BOUNDARY MAY BRING SIGNIFICANT PCPN TO THE
FORECAST AREA SAT NIGHT INTO SUNDAY WITH EVEN MILDER TEMPS. THIS
WILL CONTINUE TO BE MONITORED FOR THE UPCOMING WEEKEND FOR THE
POSSIBILITY OF SOME HYDRO ISSUES.
FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED
AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...LAKE EFFECT SNOW ADVISORY UNTIL 6 AM EST THURSDAY FOR NYZ032-
033.
MA...NONE.
VT...NONE.
&&
$$
SYNOPSIS...KL/WASULA
NEAR TERM...HWJIV/KL/WASULA
SHORT TERM...KL
LONG TERM...NAS
AVIATION...HWJIV/NAS
HYDROLOGY...KL/WASULA
AREA FORECAST DISCUSSION
NWS ALBANY NY
1145 AM EST WED DEC 18 2013
.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE CROSSING THE REGION WILL
BRING SCATTERED SNOW SHOWERS AND FLURRIES INTO THE EARLY AFTERNOON.
LAKE EFFECT SNOW SHOWERS OR SNOW SQUALLS WILL IMPACT PORTIONS OF THE
WESTERN ADIRONDACKS THIS AFTERNOON AND TONIGHT. HIGH PRESSURE WILL
BUILD IN FROM THE SOUTHWEST FOR THURSDAY...BRINGING MILDER
TEMPERATURES...AND DRY CONDITIONS. A FRONTAL SYSTEM APPROACHING FROM
THE WEST AND NORTH WILL BRING CLOUDS...ALONG WITH SOME SNOW AND RAIN
SHOWERS FOR THURSDAY NIGHT INTO FRIDAY. A MORE SIGNIFICANT STORM
SYSTEM MAY BRING WIDESPREAD PRECIPITATION FOR A PORTION OF THE
UPCOMING WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 1145 AM EST...NO REAL CHANGES TO THE ONGOING FORECAST.
HOWEVER...TEMPERATURES STILL QUITE COLD IN VALLEY AREAS AS MIXING
HAS NOT BEEN REALIZED. FEEL PRUDENT TO LOWER MANY VALLEY LOCATIONS
ABOUT A CATEGORY BUT KEPT HIGHER ELEVATIONS ABOUT THE SAME.
CLOUDS WILL MIX WITH SUNSHINE...MORE SUNSHINE TO THE SOUTH OF THE
CAPITAL DISTRICT.
LOOK FOR HIGHS GENERALLY 25 TO 30 TO ALBANY SOUTHWARD...20 TO 25
NORTHWARD. LOOK FOR WIDELY SCATTERED SNOW SHOWERS ACROSS MUCH OF THE
REGION...WITH LITTLE OR NO ACCUMULATIONS...OUTSIDE OF THE ADIRONDACK
PARK WHERE SOME IS LIKELY LATER THIS AFTERNOON AS THE LAKE MACHINE
RAMPS UP.
THE WIND WILL BECOME WESTERLY 5 TO 15 MPH ACROSS THE REGION.
THE LATEST RUC CONTINUED TO SHOW THE H500 TROUGH AXIS...AND ITS
ASSOCIATED MID LEVEL SHORT-WAVE MOVING ACROSS WRN NEW ENGLAND. SOME
SCT SNOW SHOWER AND FLURRIES HAVE OCCURRED FROM THE CAPITAL REGION
NORTH AND WEST...AND ESPECIALLY ALONG THE SPINE OF THE SRN
GREENS...N-CNTRL TACONICS...AND BERKSHIRES. SOME SLIGHT AND LOW CHC
POPS HAVE BEEN KEPT IN THE FORECAST INTO THE EARLY PM. MOSTLY CLOUDY
CONDITIONS PERSIST NORTH OF THE MID HUDSON VALLEY AND NW CT. FURTHER
UPSTREAM...DIFFUSE LAKE EFFECT ACTIVITY IS SETTING UP JUST DOWN
STREAM OF LAKE ONTARIO. THIS ACTIVITY SHOULD ORGANIZE BETTER IN THE
EARLY PM...AND THE LAKE EFFECT SNOW ADVISORY BEGINS FOR NRN HERKIMER
AND HAMILTON COUNTIES AT 3 PM. CURRENT FORECAST TRENDS LOOK SIMILAR
FOR 3 TO 6 INCHES OF HIGH RATIO SNOWFALL. THE FORECAST TREND LOOKS
SIMILAR FOR THE LAKE POTENTIAL BELOW.
THE LAKE RESPONSE WILL DEVELOP IN THE PM...AS COOLING WITHIN THE
850-700 MB LAYER COMBINES WITH AN INCREASING LOW LEVEL FLOW OVER
WATER TRAJECTORY ACROSS LAKE ONTARIO...WITH SOME ADDITIONAL
MOISTENING FROM LAKE HURON. IT APPEARS THAT THE LAKE EFFECT
POTENTIAL FOR SINGLE SNOWBANDS WILL BE FOR A SOMEWHAT SHORT
DURATION...MAINLY AFTER NOON TODAY...THROUGH AT LEAST 6 PM EST.
EXPECT SEVERAL INCHES OF SNOW ACROSS PORTIONS OF NORTHERN HERKIMER
CO...AND POSSIBLY EXTENDING INTO PORTIONS OF WEST CENTRAL AND
NORTHWEST HAMILTON CO...MAINLY THIS AFTERNOON. SOME EXTENSION OF A
SNOWBAND MAY ALSO IMPACT PORTIONS OF THE MOHAWK VALLEY/WRN CAPITAL
REGION EARLY THIS THIS AFTERNOON...WITH MINOR ACCUMS POSSIBLE.
ENHANCED UPSLOPE ACROSS PORTIONS OF SOUTHERN VT COULD ALSO LEAD TO
A COUPLE INCHES OF SNOWFALL ACROSS EASTERN PORTIONS OF BENNINGTON
CO AND WEST CENTRAL WINDHAM CO THIS AFTERNOON.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
TONIGHT...THE AFOREMENTIONED SNOWBAND WILL LIKELY BE ONGOING THIS
EVENING ACROSS THE ADVISORY AREA...AND LIFTING
NORTHWARD...IMPACTING AREAS NEAR AND NORTH OF ROUTE 28. LATER
TONIGHT...IT APPEARS THAT THE BAND SHOULD WEAKEN AS THE INVERSION
LEVEL DROPS RAPIDLY...AND LOW LEVEL DIRECTIONAL SHEAR INCREASES
AND DISRUPTS SINGLE BAND POTENTIAL. ELSEWHERE...EXPECT PARTLY
CLOUDY SKIES...ALTHOUGH SOME PERIODS OF MOSTLY CLEAR SKIES WILL BE
POSSIBLE. GIVEN OUR DEEP...FRESH SNOWPACK...ANY BREAKS IN THE
CLOUDS WILL ALLOW TEMPS TO QUICKLY DROP. HAVE THEREFORE WENT BELOW
THE COLDEST GUIDANCE...WITH MAINLY SINGLE DIGITS AND TEENS
EXPECTED. SHOULD BREAKS IN THE CLOUDS BE MORE WIDESPREAD AND/OR
LONGER IN DURATION...EVEN COLDER MIN TEMPS WOULD BE POSSIBLE.
THU...LOW AND MID LEVEL WARM ADVECTION DEVELOPS AND STRENGTHENS.
AS MILDER AND INCREASINGLY MOIST AIR MOVES OVER THE VERY COLD
GROUND AND DEEP SNOW COVER...IT APPEARS THAT A LOW LEVEL INVERSION
WILL DEVELOP...LEADING TO MOSTLY CLOUDY SKIES FOR AT LEAST THE
NORTHERN THIRD OF THE REGION...WITH OCCASIONAL CLOUDS TO THE
SOUTH. FOR MAX TEMPS...HAVE SIDED WITH THE COOLER OF THE MAV/MET
MOS...WITH GENERALLY 30S EXPECTED FOR VALLEY AREAS...AND 20S TO
AROUND 30 FOR HIGHER ELEVATIONS.
THU NT-FRI NT...A FRONTAL BOUNDARY WILL GRADUALLY APPROACH FROM
THE N AND W...AS WAVES OF LOW PRESSURE TRAVEL ALONG IT. SEVERAL
SURGES OF ISENTROPIC LIFT WILL IMPACT THE REGION...ESP NORTHERN
AND CENTRAL AREAS. IT APPEARS THAT THE BEST CHC FOR PRECIP WILL BE
LATE THU NT INTO FRI EVENING. WARMING ALOFT COULD ALLOW FOR SOME
MIXED PRECIP TO OCCUR ACROSS NORTHERN AREAS THU NT...AND AGAIN FRI
NT...AND WILL HAVE TO WATCH MODEL TRENDS AND LOW LEVEL THERMAL
PROFILES. QPF LOOKS LIGHT AT THIS TIME...BUT CAN NOT RULE OUT SOME
AREAS OF LIGHT ICING...ESP FRI NT ACROSS PORTIONS OF THE SOUTHERN
ADIRONDACKS AND WESTERN MOHAWK VALLEY. HAVE SIDED WITH...OR WENT
BELOW THE COOLER MAV/MET...WITH NIGHTTIME MINS FALLING INTO THE
20S IN MOST AREAS...AND MAX TEMPS RANGING FROM THE UPPER 20S TO
MID 30S ACROSS NORTHERN AREAS...AND MID 30S TO MID 40S ACROSS
SOUTHERN AREAS.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
STILL DECENT AGREEMENT IN GUIDANCE AND ENSEMBLES FOR A STRONG WARM
ADVECTION EVENT THAT SHOULD RESULT IN MORE RAIN THAN WINTRY
PRECIPITATION. ONE SYSTEM WILL BE EXITING THROUGH SATURDAY MORNING
WITH JUST SCATTERED RAIN AND SNOW SHOWERS ENDING. THE NEXT
SYSTEM...WITH SOUTHERN STREAM ORIGINS...SPREADS MOSTLY RAIN OVER
MUCH OF THE REGION SATURDAY AFTERNOON...STARTING AS A MIX IN THE
SOUTHERN ADIRONDACKS. THERE COULD BE MINOR TO MODERATE ACCUMULATIONS
OF MIXED PRECIPITATION...INCLUDING POSSIBLY FREEZING RAIN...IN THE
SOUTHERN ADIRONDACKS THROUGH SATURDAY NIGHT BEFORE PRECIPITATION
TURNS TO RAIN SUNDAY MORNING.
THIS COULD BE A PROLONGED EVENT...WITH A VERY STRONG WEST
SOUTHWESTERLY BOUNDARY LAYER JET AND DEEP MOISTURE...ALONG WITH
STRONG ISENTROPIC LIFT WITHIN THE WARM ADVECTION...AND STRONG
FRONTOGENESIS ALONG THE COLD FRONT. THERE COULD BE ENOUGH RAIN FOR
SOME POTENTIAL RUN OFF PROBLEMS WHEN COMBINED WITH SNOW MELT. THE
AXIS OF HEAVIEST RAIN LOOKS TO BE ALONG AND NORTH OF THE SCHOHARIE
VALLEY...SOUTHERN ADIRONDACKS...HELDERBERGS TO THE LAKE GEORGE
SARATOGA REGION...SOUTHERN GREEN MOUNTAINS AND BERKSHIRES. SOME
INDICATIONS ARE THAT THE HEAVIEST RAIN COULD BE MOSTLY THE EXTREME
NORTHERN SECTIONS OF THE FORECAST AREA...SO THERE IS CONSIDERABLE
UNCERTAINTY ON WHERE THE HEAVIEST RAIN COULD FALL. THE POTENTIAL FOR
HEAVY RAIN...SNOW MELT AND RUN OFF WILL BE ADDRESSED IN THE HWO.
HIGHS SATURDAY IN THE 40S...MID TO UPPER 30S SOUTHERN ADIRONDACKS
AND SOUTHERN GREEN MOUNTAINS. HIGHS SUNDAY IN THE LOWER TO MID
50S...WITH 40S IN HIGHER ELEVATIONS...AROUND 40 SOUTHERN
ADIRONDACKS. THE FRONT TRACKS THROUGH SUNDAY NIGHT AND EARLY MONDAY
WITH DEEP COLD ADVECTION SPREADING ACROSS OUR REGION. HIGHS MONDAY
IN THE LOWER TO MID 30S...WITH UPPER 20S IN THE SOUTHERN ADIRONDACKS
AND SOUTHERN GREEN MOUNTAINS. COLD ADVECTION CONTINUES TUESDAY WITH
HIGHS IN THE 20S...UPPER TEENS IN THE SOUTHERN ADIRONDACKS. THERE
COULD BE LAKE EFFECT SNOW BANDS MONDAY INTO TUESDAY BUT THE INLAND
EXTENT IS IN QUESTION.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
MAINLY VFR CONDITIONS THIS AFTERNOON AT THE TAF SITES...BUT
OCCASIONAL MVFR THIS AFTERNOON AT KPSF.
AN UPPER LEVEL DISTURBANCE TRACKING THROUGH THE REGION WILL BRING
PERIODS OF BROKEN CEILINGS ABOVE 3000 FEET THROUGH THE DAY. THERE
COULD BE SOME FLURRIES THIS MORNING SO WILL PUT VCSH FOR A FEW HOURS
AT KALB...KPSF...AND KGFL. AT THE SURFACE...HIGH PRESSURE WILL
BUILD IN. SCATTERED VARIABLE BROKEN CEILINGS ABOVE 3000 FEET SHOULD
CONTINUE THROUGH TONIGHT MAINLY AT KALB...KPSF AND KGFL BUT JUST
SCATTERED AT KPOU.
WINDS WILL BE LIGHT TO CALM THROUGH THE EARLY MORNING HOURS BECOMING
WESTERLY DURING THE LATE MORNING AND INCREASING TO 6 TO 10 KNOTS.
SOME GUSTS INTO THE TEENS ARE EXPECTED AT KALB AND KPSF FROM LATE
MORNING THROUGH THE MID AFTERNOON...AND SHOULD CONTINUE INTO THE
EVENING. WINDS SHOULD DECREASE TO 5 KT OR LESS LATER THIS EVENING
AND CONTINUE THROUGH THE NIGHT.
OUTLOOK...
THURSDAY NIGHT: LOW OPERATIONAL IMPACT. SLIGHT CHANCE OF SHSN.
FRIDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...SHSN.
FRIDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...SHSN.
SATURDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...RA.
SATURDAY NIGHT: HIGH OPERATIONAL IMPACT. LIKELY RA.
SUNDAY: HIGH OPERATIONAL IMPACT. LIKELY RA.
&&
.HYDROLOGY...
LAKE EFFECT SNOWBANDS...AND SCATTERED SNOW SHOWERS WILL BE
POSSIBLE TODAY AND TONIGHT...WITH MAXIMUM TOTAL LIQUID EQUIVALENT
GENERALLY REMAINING UNDER ONE QUARTER OF AN INCH...WHICH WOULD BE
ACROSS THE WESTERN ADIRONDACKS.
OTHERWISE...THROUGH TONIGHT...TEMPS WILL CONTINUE TO BE BELOW
NORMAL AND ICE WILL CONTINUE TO FORM AND THICKEN ON AREA
RIVERS...STREAMS AND PARTICULARLY LAKES.
A MODERATING TREND IN TEMPS IS LIKELY THU INTO FRI...WITH A
FRONTAL BOUNDARY BRINGING SOME SHOWERS TO CLOSE THE WORK WEEK.
SOME SNOW MELT IS LIKELY THIS WEEKEND. ALSO...A STORM SYSTEM
MOVING ALONG A FRONTAL BOUNDARY MAY BRING SIGNIFICANT PCPN TO THE
FORECAST AREA SAT NIGHT INTO SUNDAY WITH EVEN MILDER TEMPS. THIS
WILL CONTINUE TO BE MONITORED FOR THE UPCOMING WEEKEND FOR THE
POSSIBILITY OF SOME HYDRO ISSUES.
FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED
AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...LAKE EFFECT SNOW ADVISORY FROM 3 PM THIS AFTERNOON TO 6 AM EST
THURSDAY FOR NYZ032-033.
MA...NONE.
VT...NONE.
&&
$$
SYNOPSIS...KL/WASULA
NEAR TERM...HWJIV/KL/WASULA
SHORT TERM...KL
LONG TERM...NAS
AVIATION...HWJIV/NAS
HYDROLOGY...KL/WASULA
AREA FORECAST DISCUSSION
NWS ALBANY NY
944 AM EST WED DEC 18 2013
.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE CROSSING THE REGION WILL
BRING SCATTERED SNOW SHOWERS AND FLURRIES INTO THE EARLY AFTERNOON.
LAKE EFFECT SNOW SHOWERS OR SNOW SQUALLS WILL IMPACT PORTIONS OF THE
WESTERN ADIRONDACKS THIS AFTERNOON AND TONIGHT. HIGH PRESSURE WILL
BUILD IN FROM THE SOUTHWEST FOR THURSDAY...BRINGING MILDER
TEMPERATURES...AND DRY CONDITIONS. A FRONTAL SYSTEM APPROACHING FROM
THE WEST AND NORTH WILL BRING CLOUDS...ALONG WITH SOME SNOW AND RAIN
SHOWERS FOR THURSDAY NIGHT INTO FRIDAY. A MORE SIGNIFICANT STORM
SYSTEM MAY BRING WIDESPREAD PRECIPITATION FOR A PORTION OF THE
UPCOMING WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 943 AM EST...THE LATEST RUC SHOWS THE H500 TROUGH AXIS...AND
ITS ASSOCIATED MID LEVEL SHORT-WAVE MOVING ACROSS WRN NEW ENGLAND.
SOME SCT SNOW SHOWER AND FLURRIES HAVE OCCURRED FROM THE CAPITAL
REGION NORTH AND WEST...AND ESPECIALLY ALONG THE SPINE OF THE SRN
GREENS...N-CNTRL TACONICS...AND BERKSHIRES. SOME SLIGHT AND LOW
CHC POPS HAVE BEEN KEPT IN THE FORECAST INTO THE EARLY PM. MOSTLY
CLOUDY CONDITIONS PERSIST NORTH OF THE MID HUDSON VALLEY AND NW CT.
FURTHER UPSTREAM...DIFFUSE LAKE EFFECT ACTIVITY IS SETTING UP JUST
DOWN STREAM OF LAKE ONTARIO. THIS ACTIVITY SHOULD ORGANIZE BETTER
IN THE EARLY PM...AND THE LAKE EFFECT SNOW ADVISORY BEGINS FOR NRN
HERKIMER AND HAMILTON COUNTIES AT 3 PM. CURRENT FORECAST TRENDS
LOOK SIMILAR FOR 3 TO 6 INCHES OF HIGH RATIO SNOWFALL. THE
FORECAST TREND LOOKS SIMILAR FOR THE LAKE POTENTIAL BELOW.
THE LAKE RESPONSE WILL DEVELOP IN THE PM...AS COOLING WITHIN THE
850-700 MB LAYER COMBINES WITH AN INCREASING LOW LEVEL FLOW OVER
WATER TRAJECTORY ACROSS LAKE ONTARIO...WITH SOME ADDITIONAL
MOISTENING FROM LAKE HURON. IT APPEARS THAT THE LAKE EFFECT
POTENTIAL FOR SINGLE SNOWBANDS WILL BE FOR A SOMEWHAT SHORT
DURATION...MAINLY AFTER NOON TODAY...THROUGH AT LEAST 6 PM EST.
EXPECT SEVERAL INCHES OF SNOW ACROSS PORTIONS OF NORTHERN HERKIMER
CO...AND POSSIBLY EXTENDING INTO PORTIONS OF WEST CENTRAL AND
NORTHWEST HAMILTON CO...MAINLY THIS AFTERNOON. SOME EXTENSION OF A
SNOWBAND MAY ALSO IMPACT PORTIONS OF THE MOHAWK VALLEY/WRN CAPITAL
REGION EARLY THIS THIS AFTERNOON...WITH MINOR ACCUMS POSSIBLE.
ENHANCED UPSLOPE ACROSS PORTIONS OF SOUTHERN VT COULD ALSO LEAD TO
A COUPLE INCHES OF SNOWFALL ACROSS EASTERN PORTIONS OF BENNINGTON
CO AND WEST CENTRAL WINDHAM CO THIS AFTERNOON.
AS FOR TEMPS...HAVE SIDED A BIT BELOW A MAV/MET MOS BLEND...WITH
UPPER 20S TO LOWER 30S EXPECTED IN MOST VALLEY AREAS...AND MAINLY
20S FOR HIGHER ELEVATIONS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
TONIGHT...THE AFOREMENTIONED SNOWBAND WILL LIKELY BE ONGOING THIS
EVENING ACROSS THE ADVISORY AREA...AND LIFTING
NORTHWARD...IMPACTING AREAS NEAR AND NORTH OF ROUTE 28. LATER
TONIGHT...IT APPEARS THAT THE BAND SHOULD WEAKEN AS THE INVERSION
LEVEL DROPS RAPIDLY...AND LOW LEVEL DIRECTIONAL SHEAR INCREASES
AND DISRUPTS SINGLE BAND POTENTIAL. ELSEWHERE...EXPECT PARTLY
CLOUDY SKIES...ALTHOUGH SOME PERIODS OF MOSTLY CLEAR SKIES WILL BE
POSSIBLE. GIVEN OUR DEEP...FRESH SNOWPACK...ANY BREAKS IN THE
CLOUDS WILL ALLOW TEMPS TO QUICKLY DROP. HAVE THEREFORE WENT BELOW
THE COLDEST GUIDANCE...WITH MAINLY SINGLE DIGITS AND TEENS
EXPECTED. SHOULD BREAKS IN THE CLOUDS BE MORE WIDESPREAD AND/OR
LONGER IN DURATION...EVEN COLDER MIN TEMPS WOULD BE POSSIBLE.
THU...LOW AND MID LEVEL WARM ADVECTION DEVELOPS AND STRENGTHENS.
AS MILDER AND INCREASINGLY MOIST AIR MOVES OVER THE VERY COLD
GROUND AND DEEP SNOW COVER...IT APPEARS THAT A LOW LEVEL INVERSION
WILL DEVELOP...LEADING TO MOSTLY CLOUDY SKIES FOR AT LEAST THE
NORTHERN THIRD OF THE REGION...WITH OCCASIONAL CLOUDS TO THE
SOUTH. FOR MAX TEMPS...HAVE SIDED WITH THE COOLER OF THE MAV/MET
MOS...WITH GENERALLY 30S EXPECTED FOR VALLEY AREAS...AND 20S TO
AROUND 30 FOR HIGHER ELEVATIONS.
THU NT-FRI NT...A FRONTAL BOUNDARY WILL GRADUALLY APPROACH FROM
THE N AND W...AS WAVES OF LOW PRESSURE TRAVEL ALONG IT. SEVERAL
SURGES OF ISENTROPIC LIFT WILL IMPACT THE REGION...ESP NORTHERN
AND CENTRAL AREAS. IT APPEARS THAT THE BEST CHC FOR PRECIP WILL BE
LATE THU NT INTO FRI EVENING. WARMING ALOFT COULD ALLOW FOR SOME
MIXED PRECIP TO OCCUR ACROSS NORTHERN AREAS THU NT...AND AGAIN FRI
NT...AND WILL HAVE TO WATCH MODEL TRENDS AND LOW LEVEL THERMAL
PROFILES. QPF LOOKS LIGHT AT THIS TIME...BUT CAN NOT RULE OUT SOME
AREAS OF LIGHT ICING...ESP FRI NT ACROSS PORTIONS OF THE SOUTHERN
ADIRONDACKS AND WESTERN MOHAWK VALLEY. HAVE SIDED WITH...OR WENT
BELOW THE COOLER MAV/MET...WITH NIGHTTIME MINS FALLING INTO THE
20S IN MOST AREAS...AND MAX TEMPS RANGING FROM THE UPPER 20S TO
MID 30S ACROSS NORTHERN AREAS...AND MID 30S TO MID 40S ACROSS
SOUTHERN AREAS.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
STILL DECENT AGREEMENT IN GUIDANCE AND ENSEMBLES FOR A STRONG WARM
ADVECTION EVENT THAT SHOULD RESULT IN MORE RAIN THAN WINTRY
PRECIPITATION. ONE SYSTEM WILL BE EXITING THROUGH SATURDAY MORNING
WITH JUST SCATTERED RAIN AND SNOW SHOWERS ENDING. THE NEXT
SYSTEM...WITH SOUTHERN STREAM ORIGINS...SPREADS MOSTLY RAIN OVER
MUCH OF THE REGION SATURDAY AFTERNOON...STARTING AS A MIX IN THE
SOUTHERN ADIRONDACKS. THERE COULD BE MINOR TO MODERATE ACCUMULATIONS
OF MIXED PRECIPITATION...INCLUDING POSSIBLY FREEZING RAIN...IN THE
SOUTHERN ADIRONDACKS THROUGH SATURDAY NIGHT BEFORE PRECIPITATION
TURNS TO RAIN SUNDAY MORNING.
THIS COULD BE A PROLONGED EVENT...WITH A VERY STRONG WEST
SOUTHWESTERLY BOUNDARY LAYER JET AND DEEP MOISTURE...ALONG WITH
STRONG ISENTROPIC LIFT WITHIN THE WARM ADVECTION...AND STRONG
FRONTOGENESIS ALONG THE COLD FRONT. THERE COULD BE ENOUGH RAIN FOR
SOME POTENTIAL RUN OFF PROBLEMS WHEN COMBINED WITH SNOW MELT. THE
AXIS OF HEAVIEST RAIN LOOKS TO BE ALONG AND NORTH OF THE SCHOHARIE
VALLEY...SOUTHERN ADIRONDACKS...HELDERBERGS TO THE LAKE GEORGE
SARATOGA REGION...SOUTHERN GREEN MOUNTAINS AND BERKSHIRES. SOME
INDICATIONS ARE THAT THE HEAVIEST RAIN COULD BE MOSTLY THE EXTREME
NORTHERN SECTIONS OF THE FORECAST AREA...SO THERE IS CONSIDERABLE
UNCERTAINTY ON WHERE THE HEAVIEST RAIN COULD FALL. THE POTENTIAL FOR
HEAVY RAIN...SNOW MELT AND RUN OFF WILL BE ADDRESSED IN THE HWO.
HIGHS SATURDAY IN THE 40S...MID TO UPPER 30S SOUTHERN ADIRONDACKS
AND SOUTHERN GREEN MOUNTAINS. HIGHS SUNDAY IN THE LOWER TO MID
50S...WITH 40S IN HIGHER ELEVATIONS...AROUND 40 SOUTHERN
ADIRONDACKS. THE FRONT TRACKS THROUGH SUNDAY NIGHT AND EARLY MONDAY
WITH DEEP COLD ADVECTION SPREADING ACROSS OUR REGION. HIGHS MONDAY
IN THE LOWER TO MID 30S...WITH UPPER 20S IN THE SOUTHERN ADIRONDACKS
AND SOUTHERN GREEN MOUNTAINS. COLD ADVECTION CONTINUES TUESDAY WITH
HIGHS IN THE 20S...UPPER TEENS IN THE SOUTHERN ADIRONDACKS. THERE
COULD BE LAKE EFFECT SNOW BANDS MONDAY INTO TUESDAY BUT THE INLAND
EXTENT IS IN QUESTION.
&&
.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
AN UPPER LEVEL DISTURBANCE TRACKING THROUGH THE REGION WILL BRING
PERIODS OF BROKEN CEILINGS ABOVE 3000 FEET THROUGH THE DAY. THERE
COULD BE SOME FLURRIES THIS MORNING SO WILL PUT VCSH FOR A FEW HOURS
AT KALB...KPSF...AND KGFL. AT THE SURFACE...HIGH PRESSURE WILL
BUILD IN. SCATTERED VARIABLE BROKEN CEILINGS ABOVE 3000 FEET SHOULD
CONTINUE THROUGH TONIGHT MAINLY AT KALB...KPSF AND KGFL BUT JUST
SCATTERED AT KPOU.
WINDS WILL BE LIGHT TO CALM THROUGH THE EARLY MORNING HOURS BECOMING
WESTERLY DURING THE LATE MORNING AND INCREASING TO 6 TO 10 KNOTS.
SOME GUSTS INTO THE TEENS ARE EXPECTED AT KALB AND KPSF FROM LATE
MORNING THROUGH THE MID AFTERNOON...AND SHOULD CONTINUE INTO THE
EVENING. WINDS SHOULD DECREASE TO 5 KT OR LESS LATER THIS EVENING
AND CONTINUE THROUGH THE NIGHT.
OUTLOOK...
THURSDAY NIGHT: LOW OPERATIONAL IMPACT. SLIGHT CHANCE OF SHSN.
FRIDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...SHSN.
FRIDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...SHSN.
SATURDAY: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA...RA.
SATURDAY NIGHT: HIGH OPERATIONAL IMPACT. LIKELY RA.
SUNDAY: HIGH OPERATIONAL IMPACT. LIKELY RA.
&&
.HYDROLOGY...
LAKE EFFECT SNOWBANDS...AND SCATTERED SNOW SHOWERS WILL BE
POSSIBLE TODAY AND TONIGHT...WITH MAXIMUM TOTAL LIQUID EQUIVALENT
GENERALLY REMAINING UNDER ONE QUARTER OF AN INCH...WHICH WOULD BE
ACROSS THE WESTERN ADIRONDACKS.
OTHERWISE...THROUGH TONIGHT...TEMPS WILL CONTINUE TO BE BELOW
NORMAL AND ICE WILL CONTINUE TO FORM AND THICKEN ON AREA
RIVERS...STREAMS AND PARTICULARLY LAKES.
A MODERATING TREND IN TEMPS IS LIKELY THU INTO FRI...WITH A
FRONTAL BOUNDARY BRINGING SOME SHOWERS TO CLOSE THE WORK WEEK.
SOME SNOW MELT IS LIKELY THIS WEEKEND. ALSO...A STORM SYSTEM
MOVING ALONG A FRONTAL BOUNDARY MAY BRING SIGNIFICANT PCPN TO THE
FORECAST AREA SAT NIGHT INTO SUNDAY WITH EVEN MILDER TEMPS. THIS
WILL CONTINUE TO BE MONITORED FOR THE UPCOMING WEEKEND FOR THE
POSSIBILITY OF SOME HYDRO ISSUES.
FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED
AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...LAKE EFFECT SNOW ADVISORY FROM 3 PM THIS AFTERNOON TO 6 AM EST
THURSDAY FOR NYZ032-033.
MA...NONE.
VT...NONE.
&&
$$
SYNOPSIS...KL/WASULA
NEAR TERM...KL/WASULA
SHORT TERM...KL
LONG TERM...NAS
AVIATION...NAS
HYDROLOGY...KL/WASULA
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
941 PM CST THU DEC 19 2013
.DISCUSSION...
813 PM CST
FOR EVENING UPDATE...
MOVED UP START AND EXPANDED SLIGHTLY FREEZING RAIN ADVISORY FOR
FAR NORTH AND NORTH CENTRAL IL TONIGHT-FRIDAY. HAVE ALSO MADE SOME
ADJUSTMENTS TO WEEKEND STORM SYSTEM AS OUTLINED BELOW.
TONIGHT/FRIDAY...
HAVE SLIGHTLY EXPANDED AND STARTED THE FREEZING RAIN ADVISORY
EARLIER TONIGHT AS TEMPERATURES HOVER RIGHT AROUND 32F ACROSS
NORTH CENTRAL AND FAR NORTHEAST ILLINOIS...AND A REPORT OF A LIGHT
GLAZE HAS ALREADY BEEN RECEIVED FROM THE NORTHWEST SIDE OF ROCKFORD.
EVENING GOES WATER VAPOR LOOP DEPICTS A SHORT WAVE CENTER NEARING
THE OZARKS IN THE BROAD MOIST WSW FLOW OVER THE AREA. THIS FEATURE
HAS LED TO AN EXPANSION IN LOW CLOUDS AS WELL AS LIGHT RAIN/DRIZZLE
ACROSS NORTHEAST MO...EASTERN IA...SOUTHERN WI...AND NORTHWEST AND
NORTH CENTRAL IL. THE 00Z DVN SOUNDING SHOWED 25-35KT OF
SOUTHWESTERLY FLOW WITHIN A SATURATED LAYER FROM 750MB TO THE
SURFACE. THE MIN TEMP OBSERVED IN THAT LAYER OF ONLY -1C...SO
CERTAINLY NO ICE CRYSTALS INVOLVED. THE RAP APPEARS TO ANALYZE THIS
WELL AT 285K-290K WITH SATURATED ISENTROPIC ASCENT ACROSS NORTHERN
IL INTO OVERNIGHT...AND THE CONVERGENCE OF THE LOW-LEVEL BOUNDARY
DRAPED ACROSS THE AREA HELPING TO POOL MOISTURE/SATURATION.
THE SURFACE STATIONARY BOUNDARY IS ARCED FROM SOUTH OF PERU TO THE
SOUTH SIDE OF CHICAGO. FOR TEMPERATURES...BELIEVE THAT NORTH OF THE
BOUNDARY WILL BASICALLY HOLD STEADY OR EASE DOWNWARD...WHILE SOUTH
OF THERE MAY EVEN KEEP INCHING UP. FOR POINTS NORTH...THIS CREATES
AN EARLIER AND PROBABLY BETTER POTENTIAL FOR LIGHT ICING THAN
ORIGINALLY FORECAST...AS TEMPS ACROSS NORTH CENTRAL IL ARE ALREADY
32-33F. SO HAVE EXPANDED FREEZING RAIN DEPICTION IN THE GRIDS AND
AGAIN STARTED THE ADVISORY EARLIER.
SATURDAY/SUNDAY...
HAVE MADE ADJUSTMENTS TO THE FORECAST GRIDS FOR SATURDAY INTO SUNDAY
BASED ON MODEL THERMAL PROFILES AND SOUNDINGS...PARTICULARLY THE
1000-850 MB CRITICAL THICKNESS (1300 DM) WHICH IS A KEY INDICATOR
FOR SNOW VERSUS RAIN/ZR/SLEET. THE GFS RUNS TODAY WERE THE COLDEST
WITH THE NAM/ECMWF SHOWING A MUCH MORE DISTINCT WARM NOSE AT 850
MB...BUT EVEN THE GFS WOULD ONLY FAVOR THE FAR NORTHERN CWA FOR A
WINTRY MIX TRANSITIONING TO SNOW/SLEET AND THEN ALL SNOW ON SATURDAY
NIGHT WHERE THERE IS THE BEST OVERLAP WITH FORCING AND LIFT THROUGH
THE DGZ. IN BETWEEN THE FAVORED AREA FOR MORE SIGNIFICANT SNOW/SLEET
ACCUMS AND MAINLY RAIN OVER THE SOUTHEAST HALF OF THE CWA...HAVE
INDICATED A TRANSITION ZONE WHERE A MIXED BAG INCLUDING FREEZING
RAIN IS POSSIBLE. AM CONCERNED THAT IF P-TYPE IS MAINLY ZR FOR A
TIME...THERE COULD BE DECENT ICE ACCRETION...AND THIS WOULD
INCLUDE PARTS OF THE WEST AND NORTHWEST CHICAGO METRO.
FINALLY...SUNDAY MORNING IT APPEARS THAT ALL BUT THE SOUTHEAST
THIRD OF THE CWA WILL TRANSITION OVER TO ALL SNOW AS COLDER AIR
PUSHES IN ALOFT.
THE TWEAKS TO QPF AND WEATHER TYPES AND SNOW AMOUNT GRIDS RESULTED
IN A MUCH TIGHTER SNOWFALL GRADIENT...WITH POTENTIAL FOR AMOUNTS IN
EXCESS OF 6 INCHES IN NORTH CENTRAL/NW AND EXTREME NORTHEASTERN
ILLINOIS...QUICKLY TAPERING TO THE SOUTHEAST. LITTLE OR NO SNOW
ACCUMULATION IS ANTICIPATED IN THE SOUTHEAST THIRD OF THE CWA.
NEEDLESS TO SAY...THIS IS STILL A FLUID SITUATION AND SMALL CHANGES
IN THE TRACK OF THE LOW PRESSURE SYSTEM AND THERMAL PROFILES WILL
HAVE LARGE IMPLICATIONS IN PRECIPITATION TYPE AND AMOUNTS. HAVE MADE
NO CHANGES TO THE WINTER STORM WATCH AND FLOOD WATCH IN EFFECT.
MTF/RC/RATZER
//PREV DISCUSSION...
UPDATED...415 PM CST FOR THIS WEEKEND PORTION
TONIGHT THROUGH FRIDAY NIGHT
UPDATED...1224 PM CST
FRONTAL BOUNDARY IS DRAPED FROM THE CHICAGO METRO AREA WSW TO NEAR
THE QUAD CITIES THIS AFTERNOON. ASCENT IS FORECAST TO INCREASE THIS
EVENING AND TONIGHT ON TOP OF THE BOUNDARY WHICH WILL MEANDER SOME
AS THE SURFACE WAVE LIFTS ACROSS THE REGION. WARM ADVECTION ALOFT
LEAVES LITTLE DOUBT THAT PRECIP WILL MELT ALOFT WITH 3-4C SATURATED
WARM LAYER TEMPS AS FAR NORTH AS THE WI STATE LINE. THE BIG CONCERN
WILL BE SURFACE/GROUND TEMPERATURE TRENDS. TEMPERATURES ARE
EXPECTED TO MOSTLY HOLD STEADY INTO THE LATE EVENING...THEN COLDER
//BELOW FREEZING// SURFACE TEMPS WILL START TO TRICKLE SOUTHEAST
INTO FAR NORTHERN IL AS THE LOW STARTS TO PASS TO OUR SOUTH.
CURRENTLY IT APPEARS THAT ONLY THE FAR REACHES OF THE CWA...
INCLUDING PORTIONS OF OGLE...WINNEBAGO...BOONE...AND MCHENRY
COUNTIES...WILL SEE SURFACE TEMPERATURES FALLING BELOW FREEZING
OVERNIGHT AND WHERE THE CONCERN FOR LIGHT FREEZING RAIN AND LIGHT
ICE ACCUMULATIONS WILL BE. A FREEZING RAIN ADVISORY HAS BEEN ISSUED
FOR THESE COUNTIES...AND EXPECT A GLAZE UP TO A TENTH OF AN INCH OF
ICE FOR THESE AREAS.
BY MID MORNING FRIDAY...TEMPERATURES ARE EXPECTED TO CONTINUE TO
SLOWLY FALL WITH THE LOW DEPARTING EAST. FORCING QUICKLY TAPERS BUT
PERSISTENT LOW LEVEL MOISTURE AND WEAK OMEGA RAISES THE CONCERN FOR
FREEZING DRIZZLE TO SPREAD SOUTH OF THE CURRENT ADVISORY
AREA...PERHAPS AS FAR SOUTH AS THE I-80 CORRIDOR. MID/HIGH LEVEL
MOISTURE WILL BE PRESENT...HOWEVER MID LEVEL DRY LAYER IS EXPECTED
TO INHIBIT SEEDER/FEEDER FROM INTRODUCING ICE INTO THE LOW LEVEL
MOISTURE LAYER...WHICH ONLY HAS TEMPERATURES AS COOL AS -5C.
SURFACE TEMPERATURES WILL BE RIGHT AROUND THE FREEZING MARK. FOR
NOW PLAN ON HIGHLIGHTING AREA WITH AN SPS...AND CANNOT RULE OUT
EXPANSION OF ADVISORY FARTHER SOUTH LATER INTO THE DAY FRIDAY IF
IT APPEARS TEMPERATURES WILL BE COOLER OR IF PRECIP MORE ROBUST.
DEUBELBEISS
FOR THE WEEKEND...
UPDATED...415 PM CST...
A VERY ACTIVE WEATHER PATTERN IS SETTING UP...WITH A FLOOD WATCH
ISSUED FOR THE SOUTHEASTERN PORTIONS OF THE CWA AND A WINTER STORM
WATCH ISSUED FOR THE NORTHERN AND NORTHWESTERN PORTIONS OF THE
CWA.
THE FIRST AREA OF CONCERN WILL BE THE POTENTIAL FOR HEAVY RAINFALL
OVER AT LEAST PORTIONS OF THE AREA. HAVE BEEN MONITORING THE
DEVELOPMENT OF A SOUTHERN STREAM SYSTEM OVER THE SOUTH HIGH PLAINS.
AS OF THURSDAY AFTERNOON...THE SYSTEM IS MOVING ONSHORE INTO
SOUTHERN CALIFORNIA AND WILL FINALLY BE SAMPLED BY THE UPPER AIR
DATA NETWORK. WHILE THE MODELS HAVE PROVIDED A MYRIAD OF SOLUTIONS
FOR THE TRACK OF THIS SYSTEM...MUCH OF THE VIABLE GUIDANCE LOOKED AT
TODAY IS CONVERGING ON THE "WARMER" SOLUTION FOR THE LOCAL
AREA...WITH THE EXCEPTION OF THE GFS WHICH IS THE OUTLIER...PUSHING
THE SYSTEM TO FAR EAST...TOO FAST. THE CONVERGED SOLUTION WILL
TRACK A SERIES OF WAVES ALONG A WARM FRONT DEVELOPING FROM THE SOUTH
HIGH PLAINS INTO NORTHERN ILLINOIS. WARM AIR...MOIST AIR...WITH
TEMPS IN THE UPPER 30S AND DEW POINTS IN THE LOWER TO MIDDLE 30S HAS
ALREADY OVERSPREAD MUCH OF THE AREA. THE WARM FRONT WILL MEANDER
OVER THE AREA AS THE MAIN SFC LOW DEEPENS AND TRACKS ALONG THE
BOUNDARY...CROSSING THE MIDDLE MISSISSIPPI VALLEY BY FRIDAY
MORNING. BY FRIDAY MORNING...THE WARM FRONT SHOULD LAY RIGHT
THROUGH THE MIDDLE OF THE CWA...WITH TEMPS IN THE LOWER 30S ALONG
THE WISCONSIN BORDER...WITH LOWER 40S OVER LOCATIONS SOUTH OF THE
ILLINOIS AND KANKAKEE RIVERS. AS THE SFC LOW TRACKS NEWD ALONG THE
PATH OF THE FRONTAL TROUGH...HIGH PRESSURE WILL BE MOVING OFF THE
SERN COAST. THIS WILL SET UP A WIDE OPEN GULF OF MEXICO...WITH
COPIOUS AMOUNTS OF MOISTURE STREAMING NWD. PWATS ARE FORECAST TO
RISE TO 1.0 TO 1.5 INCHES OVER THE SERN PORTIONS OF THE CWA RIDING
ON A STRONG LOW LEVEL JET...WITH MAX 850MB WINDS OVER 60-70KT.
WHILE THE STRONGEST OF THE LOW LEVEL JET WILL BE TO THE
SOUTH...MOSTLY OVER THE OHIO VALLEY...THERE WILL BE AMPLE ISENTROPIC
LIFT AND MOISTURE TRANSPORT TO SUPPORT AREAS OF HEAVY RAINFALL. AT
THIS POINT...IT LOOKS LIKE THE HEAVIEST RAIN WILL BE OVER THE SERN
PORTIONS OF THE CWA...OUTLINED IN THE FLOOD WATCH ISSUED THIS
AFTERNOON. HOWEVER...THE HEAVY RAIN WILL NOT BE THE ONLY PROBLEM.
WITH COOLER AIR REMAINING AT THE SFC NORTH OF THE WARM FRONT...THE
STRONG ISENTROPIC LIFT ALONG AND NORTH OF THE BOUNDARY WILL FORCE
THE WARMER AIR OVER THE COOLER AIR AT THE SFC...SETTING UP A PERIOD
OF MIXED FREEZING AND FROZEN PCPN. THE EXACT LOCATION OF THE WINTRY
MIX OF PCPN STILL REMAINS A LITTLE TOUGH TO NARROW DOWN...BUT MOST
OF THE AREA NORTH OF THE KANKAKEE AND ILLINOIS RIVERS WILL SEE A
LEAST SOME PERIODS OF THE WINTRY MIX PCPN...WITH THE ROCKFORD AREA
LIKELY NOT SEEING ANY LIQUID WHILE THE CHICAGO METRO SHOULD SEE SOME
AND AND SOME OF THE WINTRY MIX.
AS THE HEAVY RAIN SITUATION IS WINDING DOWN SATURDAY NIGHT OR EARLY
SUNDAY MORNING...THE MAIN FORECAST CONCERN WILL SHIFT TO THE
POTENTIAL FOR HEAVY SNOWFALL. THE SRN STREAM SYSTEM NOT ONLY WILL
BE RESPONSIBLE FOR DRAWING MOISTURE NORTHWARD...THERE SHOULD BE SOME
PHASING WITH A NORTHERN STREAM SHORTWAVE DROPPING OUT OF THE NRN
PLAINS. THIS SHOULD LEAD TO THE DEVELOPMENT OF A WEAK SECONDARY
CIRCULATION OVER NRN IL BY SUNDAY MORNING...ENHANCING THE DRAW OF
COOLER AIR FROM THE NORTH. THE STRONGER COLD ADVECTION AND A STRONG
DEFORMATION ZONE ARE ADVERTISED TO SET UP OVER NRN IL/SRN WI WHICH
WILL BE THE PRIMARY FOCUSING ELEMENTS FOR A BAND OF HEAVY SNOW. AT
THIS POINT...BASED ON THE GOOD CONSENSUS OF THE NAM AND
ECMWF...WHICH WOULD WOULD INDICATE AN AXIS OF HEAVIER SNOW GENERALLY
FROM ERN IOWA TO SERN WISCONSIN. ALL THINGS CONSIDERED...CONFIDENCE
IS BECOMING HIGH ENOUGH FOR IN EXCESS OF 6 INCHES OF SNOW OVER THE
NRN AND NWRN PORTIONS OF THE CWA...AS OUTLINED IN THE WINTER STORM
WATCH ISSUED THIS AFTERNOON. CURRENTLY ANTICIPATE THAT THE ENTIRE
CWA WILL SEE AT LEAST SOME SNOW...WITH 2 TO 4 INCHES ALONG A LINE
FROM CHICAGO TO PONTIAC AND 1 TO 2 INCHES FROM VALPARAISO TO
PONTIAC...TAPERING OFF TO AN INCH OR LESS OVER THE FAR SERN PORTIONS
OF THE CWA.
AK
LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...
UPDATED 316 PM CST
SUNDAY NIGHT...
GUIDANCE CONTINUES TO BE CONSISTENT IN DELIVERING A SHOT OF ARCTIC
AIR IN THE WAKE OF THE SIGNIFICANT WEEKEND STORM. A NORTHERN STREAM
TROUGH CURRENTLY NEAR THE NORTH POLE WILL DIG IN OVER THE NORTH
CENTRAL CONUS COUPLED WITH A ~1040 MB HIGH DROPPING SOUTH FROM THE
NORTHERN PLAINS. ALL OF THE SYSTEM SNOWS SHOULD BE OFF TO THE EAST
SUNDAY NIGHT...BUT POSITIVE VORTICITY ADVECTION FROM SHORT WAVES
ROTATING AROUND DEEP UPPER TROUGH COULD SQUEEZE OUT SOME LIGHT SNOW
OR FLURRIES IN THE ARCTIC AIR MASS. THE ECMWF CONTINUES TO BE MOST
BULLISH IN SQUEEZING OUT LIGHT QPF OVER THE AREA. THERE ALSO COULD
BE A BRIEF PERIOD OF FAVORABLE LAKE EFFECT CONDITIONS FOR PORTIONS
OF NW INDIANA DEPENDING ON IF WINDS CAN REMAIN CLOSER TO DUE NORTH
BEFORE BACKING WEST NORTHWEST. TEMPERATURES WILL PLUMMET IN STRONG
COLD ADVECTION BUT PERSISTENT NW WINDS AND CLOUD COVER COULD LIMIT
HOW FAR THEY FALL. WITH THE RAPIDLY FALLING TEMPERATURES SUNDAY
NIGHT...THERE COULD VERY WELL BE A FLASH FREEZE OF ANY REMAINING
MOISTURE ON THE GROUND.
MONDAY...
MAINTAINED A SLIGHT CHANCE OF FLURRIES ON MONDAY MORNING AS THE DEEP
UPPER TROUGH WILL BE OVERHEAD AND IT MAY NOT BE HARD TO SQUEEZE OUT
DENDRITES DESPITE THE COLD DRY AIR MASS. ALSO GUIDANCE INDICATES A
FAIRLY STOUT WAVE FOCUSED INTO THE NORTHEAST CWA AND WISCONSIN...SO
FELT COMFORTABLE WITH THE SLIGHT CHANCE POP FROM GUIDANCE BLEND
INITIALIZATION FOR NORTHEAST IL AND EXTREME NW INDIANA. HIGH
TEMPERATURES MONDAY AND LOWS MONDAY NIGHT WILL BE COLD
EVERYWHERE...BUT HOW COLD WILL DEPEND ON WHICH AREAS MAINTAIN
SUBSTANTIAL SNOW PACK AFTER THE WEEKEND SYSTEM. AT THIS TIME...IT
APPEARS THAT THE NORTHERN CWA WOULD HAVE THE BEST CHANCE. WITH
SURFACE HIGH BEING NEAR OR OVER THE AREA AND NO MORE THAN PARTLY
CLOUDY SKIES EXPECTED...DROPPED LOW TEMPERATURES MONDAY NIGHT FROM
PREVIOUS FORECAST TO 5 TO 10 BELOW WEST OF THE FOX VALLEY. STAYED
MORE CONSERVATIVE IN THE SOUTHERN CWA WHERE LITTLE OR NO SNOW COVER
SHOULD BE LEFT. TO NOTE...THE ECMWF AND GFS WHICH HAVE CLEAR SKIES
HAVE LOWS IN THE COLDEST SPOTS 10 DEGREES COLDER THAN IN FORECAST
GRIDS...WHILE CANADIAN MODEL KEEPS CLOUD COVER AND IS A GOOD DEAL
WARMER.
TUESDAY NIGHT THROUGH THURSDAY...
AFTER A BITTERLY COLD START TO CHRISTMAS EVE DAY...SOUTHWEST WARM
ADVECTION BEHIND TROUGH DEPARTING TO THE EAST WILL ENABLE A DECENT
AFTERNOON TEMPERATURE RECOVERY...BUT STILL WELL BELOW CLIMO. COULD
SEE TEMPERATURES BEING A BIT WARMER THAN CURRENTLY FORECAST IN AREAS
WITHOUT SNOW COVER. WILL HAVE TO WATCH FOR A NORTHERN STREAM WAVE
BEING A BIT FARTHER SOUTH THAN MODEL CONSENSUS ON CHRISTMAS EVE
NIGHT...BUT WITH ECMWF TRENDING SOUTH...INDICATED A SLIGHT CHANCE OF
LIGHT SNOW NEAR THE WISCONSIN BORDER. THIS FEATURE COULD THEN GO ON
TO RESULT IN AT LEAST SOME LIGHT SNOW OR FLURRIES IN THE AIR FOR THE
ENTIRE AREA ON CHRISTMAS DAY. THIS WOULD BE A CONSOLATION PRIZE FOR
AREAS THAT LOSE THEIR SNOW COVER THIS WEEKEND...BUT FOR AREAS THAT
KEEP AT LEAST 1 INCH OF SNOW ON THE GROUND...A WHITE CHRISTMAS IS
HIGHLY LIKELY. TEMPERATURES WILL MODERATE TO NEAR NORMAL ON
CHRISTMAS DAY...WITH ANOTHER SHOT OF ARCTIC AIR POSSIBLE ON THURSDAY
BEHIND THE CHRISTMAS DAY SYSTEM.
CONFIDENCE IN A WHITE CHRISTMAS FOR AREAS THAT MAINTAIN AT LEAST 1
INCH OF SNOW COVER THIS WEEKEND...HIGH.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 03Z...
* IFR CONDITIONS PERSISTING THROUGH THE REST OF TONIGHT AND FRIDAY.
* IF/WHEN THERE WILL BE ANY BREAKS IN THE LIGHT RAIN/DRIZZLE
THROUGH FRI.
* TIMING THE ENDING OF THE PRECIPITATION THREAT.
* SLIGHT CHANCE SURFACE TEMPERATURE FALLING TO FREEZING POINT LATE
FRI AFTERNOON.
TRS
//DISCUSSION...UPDATED 00Z...
DEEPENING LOWER LEVEL MOISTURE AND INCREASING LIFT THROUGH THE
MOIST LAYER WILL CONTINUE TONIGHT AS A SHORT WAVE OVER KS WORKS
ITS WAY NE TO THE MID MO VALLEY BY 12Z FRI THIS DISTURBANCE THEN
MOVES ACROSS THE MID MS VALLEY DURING THE DAY. ACCOMPANYING
SURFACE LOW IN FAR NW MO IS TO RIDE ALONG THE STATIONARY BOUNDARY
TO CENTRAL IL BY LATE FRI MORNING...AND TO FAR S CENTRAL MI BY
00Z SAT.
WEAK BUT INCREASING RADAR RETURNS HAVE RECENTLY APPEARED WITH
DRIZZLE STARTING TO BREAK OUT. UPSTREAM IN SE IA SOME LIGHT RAIN
SHOWING UP IN METARS IN SE IA WHERE MORE STRONGER...AND SOMEWHAT
WEAKLY CONVECTIVE LOOKING...RADAR ECHOES ARE. THIS IS EXPECTED TO
EXPAND ENE ACROSS NORTHERN IL DURING THE EVENING. ALONG WITH THE
DRIZZLE AND EVENTUALLY LIGHT RAIN...INCREASING LOW LEVEL MOISTURE
ADVECTION THROUGH THE NIGHT ESPECIALLY OVER THE SNOW PACK...SHOULD
RESULT IN A DETERIORATION OF CONDITIONS FROMM MVFR TO IFR BY LATE
THIS EVENING AND PERSISTING THROUGH THE OVERNIGHT AND FRI.
BY LATE FRI MORNING-EARLY FRI AFTERNOON THE 850HPA LOW IS TO MOVE
INTO NW IN RESULTING IN A DECREASE..AND EVENTUAL CESSATION BY 00Z
SAT...OF THE LOWER LEVEL CONVERGENCE AND ISENTROPIC LIFT. EXPECT
RAIN TO END DURING THE AFTERNOON BUT WITH SOME RESIDUAL DRIZZLE
FROM THE STILL SATURATED LOW LEVELS. IF IT IS STILL OCCURRING
DURING LATER FRI AFTERNOON THERE WOULD BE A CHANCE OF A PERIOD OF
FREEZING PRECIP AS SURFACE TEMPERATURES FALL OFF TO THE FREEZING
POINT.
IFR CEILINGS ARE ANTICIPATED TO PERSIST THROUGH THE DAY FRI AS
THE STRONG INVERSION KEEPS THE LOW LEVELS SATURATED.
LIGHT NE TO ENE SURFACE WINDS GRADUALLY BACK TO OUT OF THE NNE
AND N WITH THE SURFACE LOW TO TRACK JUST S OF ORD AND MDW.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 03Z...
* HIGH IN CONDITIONS REMAINING REMAINING LOW END IFR AT BEST THE
REST OF TONIGHT AND INTO FRI MORNING.
* HIGH CONFIDENCE IN DRIZZLE BECOMING RAIN LATE EVENING...AND IN
RAIN CONTINUING INTO PRE-DAWN HOURS.
* HIGH CONFIDENCE THAT ANY PRECIP WILL REMAIN IN THE LIQUID FORM
AT MDW THROUGH FRI
* MODERATE CONFIDENCE IN PRECIPITATION ENDING BEFORE SURFACE
TEMPERATURE REACHES FREEZING AT ORD MID AFTERNOON FRI.
TRS
//OUTLOOK FOR ORD/MDW FOR 12Z SAT-12Z THU...UPDATED 00Z...
SAT...WINTRY MIX OF PRECIP FROM MIDDAY ON...WITH A CHANCE OF A
PERIOD OF FREEZING RAIN DURING THE NIGHT. MVFR TO IFR.
SUN...SNOW. MVFR TO IFR.
MON...MVFR CIGS. CHANCE OF SNOW SHOWERS WITH IFR.
TUE...VFR.
WED...VFR BECOMING MVFR CIGS.
THU...MVFR CIGS IMPROVING TO VFR.
TRS
&&
.MARINE...
308 PM CST
THERE ARE TWO LOWS SET TO MOVE FROM THE SOUTHERN PLAINS TO THE
LOWER/EASTERN GREAT LAKES REGION THROUGH SUNDAY. THE SECOND ONE WILL
HAVE A LARGER INFLUENCE ON THE WINDS ACROSS THE LAKE...NAMELY
SATURDAY NIGHT THROUGH EARLY MONDAY. AS WINDS TURN
NORTHERLY BEHIND THIS LOW...SPEEDS WILL INCREASE BUT ARE LIKELY TO
REMAIN BELOW GALES ON SUNDAY...ALTHOUGH COULD BE CLOSE ESPECIALLY
IF THE SYSTEM IS DEEPER THAN FORECAST.
IN THE IMMEDIATE NEAR TERM...A FRONT WILL REMAIN DRAPED ACROSS THE
SOUTHERN TWO TO FOUR OPEN WATER ZONES OF LAKE MICHIGAN...WHERE
WINDS WILL BE SOMEWHAT VARIABLE IN SPEED. THIS FRONT WILL INCH
SOUTHWARD FRIDAY MORNING IN THE WAKE OF THE FIRST LOW.
A WINTRY MIX IS EXPECTED ACROSS THE SOUTHERN TWO-THIRDS OF THE
LAKE WITH BOTH SYSTEMS...TONIGHT AND FRIDAY AND AGAIN SATURDAY
NIGHT WHICH SHOULD CHANGE TO ALL SNOW SUNDAY.
IN THE WAKE OF THESE SYSTEMS...STRONG HIGH PRESSURE WILL PASS TO
THE SOUTH OF THE REGION BEFORE LIKELY STRONG SOUTHERLY WINDS TAKE
EFFECT ACROSS THE ENTIRE LAKE SOMETIME CHRISTMAS EVE NIGHT INTO
CHRISTMAS.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011 UNTIL NOON FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
FLOOD WATCH...ILZ033-ILZ039...9 AM SATURDAY TO 6 AM SUNDAY.
IN...FLOOD WATCH...INZ010-INZ011-INZ019...9 AM SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...LMZ740...9 AM FRIDAY TO 9 PM FRIDAY.
&&
$$
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AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
819 PM CST THU DEC 19 2013
.DISCUSSION...
813 PM CST
FOR EVENING UPDATE...
MOVED UP START AND EXPANDED SLIGHTLY FREEZING RAIN ADVISORY FOR
FAR NORTH AND NORTH CENTRAL IL TONIGHT-FRIDAY. HAVE ALSO MADE SOME
ADJUSTMENTS TO WEEKEND STORM SYSTEM AS OUTLINED BELOW.
TONIGHT/FRIDAY...
HAVE SLIGHTLY EXPANDED AND STARTED THE FREEZING RAIN ADVISORY
EARLIER TONIGHT AS TEMPERATURES HOVER RIGHT AROUND 32F ACROSS
NORTH CENTRAL AND FAR NORTHEAST ILLINOIS...AND A REPORT OF A LIGHT
GLAZE HAS ALREADY BEEN RECEIVED FROM THE NORTHWEST SIDE OF ROCKFORD.
EVENING GOES WATER VAPOR LOOP DEPICTS A SHORT WAVE CENTER NEARING
THE OZARKS IN THE BROAD MOIST WSW FLOW OVER THE AREA. THIS FEATURE
HAS LED TO AN EXPANSION IN LOW CLOUDS AS WELL AS LIGHT RAIN/DRIZZLE
ACROSS NORTHEAST MO...EASTERN IA...SOUTHERN WI...AND NORTHWEST AND
NORTH CENTRAL IL. THE 00Z DVN SOUNDING SHOWED 25-35KT OF
SOUTHWESTERLY FLOW WITHIN A SATURATED LAYER FROM 750MB TO THE
SURFACE. THE MIN TEMP OBSERVED IN THAT LAYER OF ONLY -1C...SO
CERTAINLY NO ICE CRYSTALS INVOLVED. THE RAP APPEARS TO ANALYZE THIS
WELL AT 285K-290K WITH SATURATED ISENTROPIC ASCENT ACROSS NORTHERN
IL INTO OVERNIGHT...AND THE CONVERGENCE OF THE LOW-LEVEL BOUNDARY
DRAPED ACROSS THE AREA HELPING TO POOL MOISTURE/SATURATION.
THE SURFACE STATIONARY BOUNDARY IS ARCED FROM SOUTH OF PERU TO THE
SOUTH SIDE OF CHICAGO. FOR TEMPERATURES...BELIEVE THAT NORTH OF THE
BOUNDARY WILL BASICALLY HOLD STEADY OR EASE DOWNWARD...WHILE SOUTH
OF THERE MAY EVEN KEEP INCHING UP. FOR POINTS NORTH...THIS CREATES
AN EARLIER AND PROBABLY BETTER POTENTIAL FOR LIGHT ICING THAN
ORIGINALLY FORECAST...AS TEMPS ACROSS NORTH CENTRAL IL ARE ALREADY
32-33F. SO HAVE EXPANDED FREEZING RAIN DEPICTION IN THE GRIDS AND
AGAIN STARTED THE ADVISORY EARLIER.
SATURDAY/SUNDAY...
HAVE MADE ADJUSTMENTS TO THE FORECAST GRIDS FOR SATURDAY INTO SUNDAY
BASED ON MODEL THERMAL PROFILES AND SOUNDINGS...PARTICULARLY THE
1000-850 MB CRITICAL THICKNESS (1300 DM) WHICH IS A KEY INDICATOR
FOR SNOW VERSUS RAIN/ZR/SLEET. THE GFS RUNS TODAY WERE THE COLDEST
WITH THE NAM/ECMWF SHOWING A MUCH MORE DISTINCT WARM NOSE AT 850
MB...BUT EVEN THE GFS WOULD ONLY FAVOR THE FAR NORTHERN CWA FOR A
WINTRY MIX TRANSITIONING TO SNOW/SLEET AND THEN ALL SNOW ON SATURDAY
NIGHT WHERE THERE IS THE BEST OVERLAP WITH FORCING AND LIFT THROUGH
THE DGZ. IN BETWEEN THE FAVORED AREA FOR MORE SIGNIFICANT SNOW/SLEET
ACCUMS AND MAINLY RAIN OVER THE SOUTHEAST HALF OF THE CWA...HAVE
INDICATED A TRANSITION ZONE WHERE A MIXED BAG INCLUDING FREEZING
RAIN IS POSSIBLE. AM CONCERNED THAT IF P-TYPE IS MAINLY ZR FOR A
TIME...THERE COULD BE DECENT ICE ACCRETION...AND THIS WOULD
INCLUDE PARTS OF THE WEST AND NORTHWEST CHICAGO METRO.
FINALLY...SUNDAY MORNING IT APPEARS THAT ALL BUT THE SOUTHEAST
THIRD OF THE CWA WILL TRANSITION OVER TO ALL SNOW AS COLDER AIR
PUSHES IN ALOFT.
THE TWEAKS TO QPF AND WEATHER TYPES AND SNOW AMOUNT GRIDS RESULTED
IN A MUCH TIGHTER SNOWFALL GRADIENT...WITH POTENTIAL FOR AMOUNTS IN
EXCESS OF 6 INCHES IN NORTH CENTRAL/NW AND EXTREME NORTHEASTERN
ILLINOIS...QUICKLY TAPERING TO THE SOUTHEAST. LITTLE OR NO SNOW
ACCUMULATION IS ANTICIPATED IN THE SOUTHEAST THIRD OF THE CWA.
NEEDLESS TO SAY...THIS IS STILL A FLUID SITUATION AND SMALL CHANGES
IN THE TRACK OF THE LOW PRESSURE SYSTEM AND THERMAL PROFILES WILL
HAVE LARGE IMPLICATIONS IN PRECIPITATION TYPE AND AMOUNTS. HAVE MADE
NO CHANGES TO THE WINTER STORM WATCH AND FLOOD WATCH IN EFFECT.
MTF/RC/RATZER
&&
.PREV DISCUSSION...
UPDATED...415 PM CST FOR THIS WEEKEND PORTION
TONIGHT THROUGH FRIDAY NIGHT
UPDATED...1224 PM CST
FRONTAL BOUNDARY IS DRAPED FROM THE CHICAGO METRO AREA WSW TO NEAR
THE QUAD CITIES THIS AFTERNOON. ASCENT IS FORECAST TO INCREASE THIS
EVENING AND TONIGHT ON TOP OF THE BOUNDARY WHICH WILL MEANDER SOME
AS THE SURFACE WAVE LIFTS ACROSS THE REGION. WARM ADVECTION ALOFT
LEAVES LITTLE DOUBT THAT PRECIP WILL MELT ALOFT WITH 3-4C SATURATED
WARM LAYER TEMPS AS FAR NORTH AS THE WI STATE LINE. THE BIG CONCERN
WILL BE SURFACE/GROUND TEMPERATURE TRENDS. TEMPERATURES ARE
EXPECTED TO MOSTLY HOLD STEADY INTO THE LATE EVENING...THEN COLDER
//BELOW FREEZING// SURFACE TEMPS WILL START TO TRICKLE SOUTHEAST
INTO FAR NORTHERN IL AS THE LOW STARTS TO PASS TO OUR SOUTH.
CURRENTLY IT APPEARS THAT ONLY THE FAR REACHES OF THE CWA...
INCLUDING PORTIONS OF OGLE...WINNEBAGO...BOONE...AND MCHENRY
COUNTIES...WILL SEE SURFACE TEMPERATURES FALLING BELOW FREEZING
OVERNIGHT AND WHERE THE CONCERN FOR LIGHT FREEZING RAIN AND LIGHT
ICE ACCUMULATIONS WILL BE. A FREEZING RAIN ADVISORY HAS BEEN ISSUED
FOR THESE COUNTIES...AND EXPECT A GLAZE UP TO A TENTH OF AN INCH OF
ICE FOR THESE AREAS.
BY MID MORNING FRIDAY...TEMPERATURES ARE EXPECTED TO CONTINUE TO
SLOWLY FALL WITH THE LOW DEPARTING EAST. FORCING QUICKLY TAPERS BUT
PERSISTENT LOW LEVEL MOISTURE AND WEAK OMEGA RAISES THE CONCERN FOR
FREEZING DRIZZLE TO SPREAD SOUTH OF THE CURRENT ADVISORY
AREA...PERHAPS AS FAR SOUTH AS THE I-80 CORRIDOR. MID/HIGH LEVEL
MOISTURE WILL BE PRESENT...HOWEVER MID LEVEL DRY LAYER IS EXPECTED
TO INHIBIT SEEDER/FEEDER FROM INTRODUCING ICE INTO THE LOW LEVEL
MOISTURE LAYER...WHICH ONLY HAS TEMPERATURES AS COOL AS -5C.
SURFACE TEMPERATURES WILL BE RIGHT AROUND THE FREEZING MARK. FOR
NOW PLAN ON HIGHLIGHTING AREA WITH AN SPS...AND CANNOT RULE OUT
EXPANSION OF ADVISORY FARTHER SOUTH LATER INTO THE DAY FRIDAY IF
IT APPEARS TEMPERATURES WILL BE COOLER OR IF PRECIP MORE ROBUST.
DEUBELBEISS
FOR THE WEEKEND...
UPDATED...415 PM CST...
A VERY ACTIVE WEATHER PATTERN IS SETTING UP...WITH A FLOOD WATCH
ISSUED FOR THE SOUTHEASTERN PORTIONS OF THE CWA AND A WINTER STORM
WATCH ISSUED FOR THE NORTHERN AND NORTHWESTERN PORTIONS OF THE
CWA.
THE FIRST AREA OF CONCERN WILL BE THE POTENTIAL FOR HEAVY RAINFALL
OVER AT LEAST PORTIONS OF THE AREA. HAVE BEEN MONITORING THE
DEVELOPMENT OF A SOUTHERN STREAM SYSTEM OVER THE SOUTH HIGH PLAINS.
AS OF THURSDAY AFTERNOON...THE SYSTEM IS MOVING ONSHORE INTO
SOUTHERN CALIFORNIA AND WILL FINALLY BE SAMPLED BY THE UPPER AIR
DATA NETWORK. WHILE THE MODELS HAVE PROVIDED A MYRIAD OF SOLUTIONS
FOR THE TRACK OF THIS SYSTEM...MUCH OF THE VIABLE GUIDANCE LOOKED AT
TODAY IS CONVERGING ON THE "WARMER" SOLUTION FOR THE LOCAL
AREA...WITH THE EXCEPTION OF THE GFS WHICH IS THE OUTLIER...PUSHING
THE SYSTEM TO FAR EAST...TOO FAST. THE CONVERGED SOLUTION WILL
TRACK A SERIES OF WAVES ALONG A WARM FRONT DEVELOPING FROM THE SOUTH
HIGH PLAINS INTO NORTHERN ILLINOIS. WARM AIR...MOIST AIR...WITH
TEMPS IN THE UPPER 30S AND DEW POINTS IN THE LOWER TO MIDDLE 30S HAS
ALREADY OVERSPREAD MUCH OF THE AREA. THE WARM FRONT WILL MEANDER
OVER THE AREA AS THE MAIN SFC LOW DEEPENS AND TRACKS ALONG THE
BOUNDARY...CROSSING THE MIDDLE MISSISSIPPI VALLEY BY FRIDAY
MORNING. BY FRIDAY MORNING...THE WARM FRONT SHOULD LAY RIGHT
THROUGH THE MIDDLE OF THE CWA...WITH TEMPS IN THE LOWER 30S ALONG
THE WISCONSIN BORDER...WITH LOWER 40S OVER LOCATIONS SOUTH OF THE
ILLINOIS AND KANKAKEE RIVERS. AS THE SFC LOW TRACKS NEWD ALONG THE
PATH OF THE FRONTAL TROUGH...HIGH PRESSURE WILL BE MOVING OFF THE
SERN COAST. THIS WILL SET UP A WIDE OPEN GULF OF MEXICO...WITH
COPIOUS AMOUNTS OF MOISTURE STREAMING NWD. PWATS ARE FORECAST TO
RISE TO 1.0 TO 1.5 INCHES OVER THE SERN PORTIONS OF THE CWA RIDING
ON A STRONG LOW LEVEL JET...WITH MAX 850MB WINDS OVER 60-70KT.
WHILE THE STRONGEST OF THE LOW LEVEL JET WILL BE TO THE
SOUTH...MOSTLY OVER THE OHIO VALLEY...THERE WILL BE AMPLE ISENTROPIC
LIFT AND MOISTURE TRANSPORT TO SUPPORT AREAS OF HEAVY RAINFALL. AT
THIS POINT...IT LOOKS LIKE THE HEAVIEST RAIN WILL BE OVER THE SERN
PORTIONS OF THE CWA...OUTLINED IN THE FLOOD WATCH ISSUED THIS
AFTERNOON. HOWEVER...THE HEAVY RAIN WILL NOT BE THE ONLY PROBLEM.
WITH COOLER AIR REMAINING AT THE SFC NORTH OF THE WARM FRONT...THE
STRONG ISENTROPIC LIFT ALONG AND NORTH OF THE BOUNDARY WILL FORCE
THE WARMER AIR OVER THE COOLER AIR AT THE SFC...SETTING UP A PERIOD
OF MIXED FREEZING AND FROZEN PCPN. THE EXACT LOCATION OF THE WINTRY
MIX OF PCPN STILL REMAINS A LITTLE TOUGH TO NARROW DOWN...BUT MOST
OF THE AREA NORTH OF THE KANKAKEE AND ILLINOIS RIVERS WILL SEE A
LEAST SOME PERIODS OF THE WINTRY MIX PCPN...WITH THE ROCKFORD AREA
LIKELY NOT SEEING ANY LIQUID WHILE THE CHICAGO METRO SHOULD SEE SOME
AND AND SOME OF THE WINTRY MIX.
AS THE HEAVY RAIN SITUATION IS WINDING DOWN SATURDAY NIGHT OR EARLY
SUNDAY MORNING...THE MAIN FORECAST CONCERN WILL SHIFT TO THE
POTENTIAL FOR HEAVY SNOWFALL. THE SRN STREAM SYSTEM NOT ONLY WILL
BE RESPONSIBLE FOR DRAWING MOISTURE NORTHWARD...THERE SHOULD BE SOME
PHASING WITH A NORTHERN STREAM SHORTWAVE DROPPING OUT OF THE NRN
PLAINS. THIS SHOULD LEAD TO THE DEVELOPMENT OF A WEAK SECONDARY
CIRCULATION OVER NRN IL BY SUNDAY MORNING...ENHANCING THE DRAW OF
COOLER AIR FROM THE NORTH. THE STRONGER COLD ADVECTION AND A STRONG
DEFORMATION ZONE ARE ADVERTISED TO SET UP OVER NRN IL/SRN WI WHICH
WILL BE THE PRIMARY FOCUSING ELEMENTS FOR A BAND OF HEAVY SNOW. AT
THIS POINT...BASED ON THE GOOD CONSENSUS OF THE NAM AND
ECMWF...WHICH WOULD WOULD INDICATE AN AXIS OF HEAVIER SNOW GENERALLY
FROM ERN IOWA TO SERN WISCONSIN. ALL THINGS CONSIDERED...CONFIDENCE
IS BECOMING HIGH ENOUGH FOR IN EXCESS OF 6 INCHES OF SNOW OVER THE
NRN AND NWRN PORTIONS OF THE CWA...AS OUTLINED IN THE WINTER STORM
WATCH ISSUED THIS AFTERNOON. CURRENTLY ANTICIPATE THAT THE ENTIRE
CWA WILL SEE AT LEAST SOME SNOW...WITH 2 TO 4 INCHES ALONG A LINE
FROM CHICAGO TO PONTIAC AND 1 TO 2 INCHES FROM VALPARAISO TO
PONTIAC...TAPERING OFF TO AN INCH OR LESS OVER THE FAR SERN PORTIONS
OF THE CWA.
AK
LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...
UPDATED 316 PM CST
SUNDAY NIGHT...
GUIDANCE CONTINUES TO BE CONSISTENT IN DELIVERING A SHOT OF ARCTIC
AIR IN THE WAKE OF THE SIGNIFICANT WEEKEND STORM. A NORTHERN STREAM
TROUGH CURRENTLY NEAR THE NORTH POLE WILL DIG IN OVER THE NORTH
CENTRAL CONUS COUPLED WITH A ~1040 MB HIGH DROPPING SOUTH FROM THE
NORTHERN PLAINS. ALL OF THE SYSTEM SNOWS SHOULD BE OFF TO THE EAST
SUNDAY NIGHT...BUT POSITIVE VORTICITY ADVECTION FROM SHORT WAVES
ROTATING AROUND DEEP UPPER TROUGH COULD SQUEEZE OUT SOME LIGHT SNOW
OR FLURRIES IN THE ARCTIC AIR MASS. THE ECMWF CONTINUES TO BE MOST
BULLISH IN SQUEEZING OUT LIGHT QPF OVER THE AREA. THERE ALSO COULD
BE A BRIEF PERIOD OF FAVORABLE LAKE EFFECT CONDITIONS FOR PORTIONS
OF NW INDIANA DEPENDING ON IF WINDS CAN REMAIN CLOSER TO DUE NORTH
BEFORE BACKING WEST NORTHWEST. TEMPERATURES WILL PLUMMET IN STRONG
COLD ADVECTION BUT PERSISTENT NW WINDS AND CLOUD COVER COULD LIMIT
HOW FAR THEY FALL. WITH THE RAPIDLY FALLING TEMPERATURES SUNDAY
NIGHT...THERE COULD VERY WELL BE A FLASH FREEZE OF ANY REMAINING
MOISTURE ON THE GROUND.
MONDAY...
MAINTAINED A SLIGHT CHANCE OF FLURRIES ON MONDAY MORNING AS THE DEEP
UPPER TROUGH WILL BE OVERHEAD AND IT MAY NOT BE HARD TO SQUEEZE OUT
DENDRITES DESPITE THE COLD DRY AIR MASS. ALSO GUIDANCE INDICATES A
FAIRLY STOUT WAVE FOCUSED INTO THE NORTHEAST CWA AND WISCONSIN...SO
FELT COMFORTABLE WITH THE SLIGHT CHANCE POP FROM GUIDANCE BLEND
INITIALIZATION FOR NORTHEAST IL AND EXTREME NW INDIANA. HIGH
TEMPERATURES MONDAY AND LOWS MONDAY NIGHT WILL BE COLD
EVERYWHERE...BUT HOW COLD WILL DEPEND ON WHICH AREAS MAINTAIN
SUBSTANTIAL SNOW PACK AFTER THE WEEKEND SYSTEM. AT THIS TIME...IT
APPEARS THAT THE NORTHERN CWA WOULD HAVE THE BEST CHANCE. WITH
SURFACE HIGH BEING NEAR OR OVER THE AREA AND NO MORE THAN PARTLY
CLOUDY SKIES EXPECTED...DROPPED LOW TEMPERATURES MONDAY NIGHT FROM
PREVIOUS FORECAST TO 5 TO 10 BELOW WEST OF THE FOX VALLEY. STAYED
MORE CONSERVATIVE IN THE SOUTHERN CWA WHERE LITTLE OR NO SNOW COVER
SHOULD BE LEFT. TO NOTE...THE ECMWF AND GFS WHICH HAVE CLEAR SKIES
HAVE LOWS IN THE COLDEST SPOTS 10 DEGREES COLDER THAN IN FORECAST
GRIDS...WHILE CANADIAN MODEL KEEPS CLOUD COVER AND IS A GOOD DEAL
WARMER.
TUESDAY NIGHT THROUGH THURSDAY...
AFTER A BITTERLY COLD START TO CHRISTMAS EVE DAY...SOUTHWEST WARM
ADVECTION BEHIND TROUGH DEPARTING TO THE EAST WILL ENABLE A DECENT
AFTERNOON TEMPERATURE RECOVERY...BUT STILL WELL BELOW CLIMO. COULD
SEE TEMPERATURES BEING A BIT WARMER THAN CURRENTLY FORECAST IN AREAS
WITHOUT SNOW COVER. WILL HAVE TO WATCH FOR A NORTHERN STREAM WAVE
BEING A BIT FARTHER SOUTH THAN MODEL CONSENSUS ON CHRISTMAS EVE
NIGHT...BUT WITH ECMWF TRENDING SOUTH...INDICATED A SLIGHT CHANCE OF
LIGHT SNOW NEAR THE WISCONSIN BORDER. THIS FEATURE COULD THEN GO ON
TO RESULT IN AT LEAST SOME LIGHT SNOW OR FLURRIES IN THE AIR FOR THE
ENTIRE AREA ON CHRISTMAS DAY. THIS WOULD BE A CONSOLATION PRIZE FOR
AREAS THAT LOSE THEIR SNOW COVER THIS WEEKEND...BUT FOR AREAS THAT
KEEP AT LEAST 1 INCH OF SNOW ON THE GROUND...A WHITE CHRISTMAS IS
HIGHLY LIKELY. TEMPERATURES WILL MODERATE TO NEAR NORMAL ON
CHRISTMAS DAY...WITH ANOTHER SHOT OF ARCTIC AIR POSSIBLE ON THURSDAY
BEHIND THE CHRISTMAS DAY SYSTEM.
CONFIDENCE IN A WHITE CHRISTMAS FOR AREAS THAT MAINTAIN AT LEAST 1
INCH OF SNOW COVER THIS WEEKEND...HIGH.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 00Z...
* MVFR CONDITIONS DETERIORATING TO IFR THIS EVENING.
* TIME THAT DRIZZLE INTENSIFIES TO LIGHT RAIN TONIGHT.
* HOW LONG RAIN CONTINUES INTO FRI.
* SLIGHT CHANCE SURFACE TEMPERATURE FALLING TO FREEZING POINT
LATER FRI AFTERNOON.
TRS
//DISCUSSION...UPDATED 00Z...
DEEPENING LOWER LEVEL MOISTURE AND INCREASING LIFT THROUGH THE
MOIST LAYER WILL CONTINUE TONIGHT AS A SHORT WAVE OVER KS WORKS
ITS WAY NE TO THE MID MO VALLEY BY 12Z FRI THIS DISTURBANCE THEN
MOVES ACROSS THE MID MS VALLEY DURING THE DAY. ACCOMPANYING
SURFACE LOW IN FAR NW MO IS TO RIDE ALONG THE STATIONARY BOUNDARY
TO CENTRAL IL BY LATE FRI MORNING...AND TO FAR S CENTRAL MI BY
00Z SAT.
WEAK BUT INCREASING RADAR RETURNS HAVE RECENTLY APPEARED WITH
DRIZZLE STARTING TO BREAK OUT. UPSTREAM IN SE IA SOME LIGHT RAIN
SHOWING UP IN METARS IN SE IA WHERE MORE STRONGER...AND SOMEWHAT
WEAKLY CONVECTIVE LOOKING...RADER ECHOES ARE. THIS IS EXPECTED TO
EXPAND ENE ACROSS NORTHERN IL DURING THE EVENING. ALONG WITH THE
DRIZZLE AND EVENTUALLY LIGHT RAIN...INCREASING LOW LEVEL MOISTURE
ADVECTION THROUGH THE NIGHT ESPECIALLY OVER THE SNOW PACK...SHOULD
RESULT IN A DETERIORATION OF CONDITIONS FROMM MVFR TO IFR BY LATE
THIS EVENING AND PERSISTING THROUGH THE OVERNIGHT AND FRI.
BY LATE FRI MORNING-EARLY FRI AFTERNOON THE 850HPA LOW IS TO MOVE
INTO NW IN RESULTING IN A DECREASE..AND EVENTUAL CESSATION BY 00Z
SAT...OF THE LOWER LEVEL CONVERGENCE AND ISENTROPIC LIFT. EXPECT
RAIN TO END DURING THE AFTERNOON BUT WITH SOME RESIDUAL DRIZZLE
FROM THE STILL SATURATED LOW LEVELS. IF IT IS STILL OCCURRING
DURING LATER FRI AFTERNOON THERE WOULD BE A CHANCE OF A PERIOD OF
FREEZING PRECIP AS SURFACE TEMPERATURES FALL OFF TO THE FREEZING
POINT.
IFR CEILINGS ARE ANTICIPATED TO PERSIST THROUGH THE DAY FRI AS
THE STRONG INVERSION KEEPS THE LOW LEVELS SATURATED.
LIGHT NE TO ENE SURFACE WINDS GRADUALLY BACK TO OUT OF THE NNE
AND N WITH THE SURFACE LOW TO TRACK JUST S OF ORD AND MDW.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* HIGH IN CONDITIONS REMAINING REMAINING LOW END IFR AT BEST THE
REST OF TONIGHT AND INTO FRI MORNING.
* HIGH CONFIDENCE DRIZZLE BECOMING RAIN LATE EVENING...AND IN
RAIN CONTINUING INTO PRE-DAWN HOURS.
* HIGH CONFIDENCE IN LOWERING CIG/VSBY TRENDS TONIGHT AND
TOMORROW.
* HIGH CONFIDENCE THAT ANY PRECIP WILL REMAIN IN THE LIQUID FORM
AT ORD & MDW UNTIL AT LEAST MID AFTERNOON FRI.
TRS
//OUTLOOK FOR ORD/MDW FOR 00Z SATURDAY-12Z THURSDAY...UPDATED 12Z...
FRIDAY NIGHT...CHC RAIN OR SNOW. MVFR TO IFR CIGS.
SATURDAY...A WINTRY MIX OF PRECIP IS EXPECTED DURING THE DAY WITH
RAIN OR FREEZING RAIN OVERNIGHT. MVFR TO IFR CIGS.
SUNDAY...SNOW. MVFR TO IFR CIGS.
MONDAY...FLURRIES IN THE MORNING. VFR.
TUESDAY...VFR.
WEDNESDAY...SCHC OF SNOW DURING THE DAY. MVFR IMPROVING TO VFR.
JEE
&&
.MARINE...
308 PM CST
THERE ARE TWO LOWS SET TO MOVE FROM THE SOUTHERN PLAINS TO THE
LOWER/EASTERN GREAT LAKES REGION THROUGH SUNDAY. THE SECOND ONE WILL
HAVE A LARGER INFLUENCE ON THE WINDS ACROSS THE LAKE...NAMELY
SATURDAY NIGHT THROUGH EARLY MONDAY. AS WINDS TURN
NORTHERLY BEHIND THIS LOW...SPEEDS WILL INCREASE BUT ARE LIKELY TO
REMAIN BELOW GALES ON SUNDAY...ALTHOUGH COULD BE CLOSE ESPECIALLY
IF THE SYSTEM IS DEEPER THAN FORECAST.
IN THE IMMEDIATE NEAR TERM...A FRONT WILL REMAIN DRAPED ACROSS THE
SOUTHERN TWO TO FOUR OPEN WATER ZONES OF LAKE MICHIGAN...WHERE
WINDS WILL BE SOMEWHAT VARIABLE IN SPEED. THIS FRONT WILL INCH
SOUTHWARD FRIDAY MORNING IN THE WAKE OF THE FIRST LOW.
A WINTRY MIX IS EXPECTED ACROSS THE SOUTHERN TWO-THIRDS OF THE
LAKE WITH BOTH SYSTEMS...TONIGHT AND FRIDAY AND AGAIN SATURDAY
NIGHT WHICH SHOULD CHANGE TO ALL SNOW SUNDAY.
IN THE WAKE OF THESE SYSTEMS...STRONG HIGH PRESSURE WILL PASS TO
THE SOUTH OF THE REGION BEFORE LIKELY STRONG SOUTHERLY WINDS TAKE
EFFECT ACROSS THE ENTIRE LAKE SOMETIME CHRISTMAS EVE NIGHT INTO
CHRISTMAS.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011 UNTIL NOON FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
FLOOD WATCH...ILZ033-ILZ039...9 AM SATURDAY TO 6 AM SUNDAY.
IN...FLOOD WATCH...INZ010-INZ011-INZ019...9 AM SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...LMZ740...9 AM FRIDAY TO 9 PM FRIDAY.
&&
$$
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WWW.YOUTUBE.COM/NWSCHICAGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1157 PM CST TUE DEC 17 2013
.DISCUSSION...
845 PM CST
FOR EVENING UPDATE...
MINOR TWEAKS TO NEAR TERM GOING FORECAST THIS EVENING...MAINLY TO
RAISE MIN TEMPS A LITTLE OVERNIGHT AND TO TWEAK SKY COVER THIS
EVENING BASED ON SATELLITE TRENDS.
HIGHLY SHEARED MID-LEVEL SHORT WAVE NOTED IN FAST NORTHWEST FLOW
ALOFT PER RAOB/GOES VAPOR IMAGERY ACROSS THE AREA EARLY THIS
EVENING...WITH 85-95 KT H5 SPEED MAX NOTED IN MPX-DVN-ILX RAOBS.
REGIONAL RADAR MOSAIC HAS BEEN DEPICTING AN AREA OF VERY LIGHT SNOW
AND FLURRIES ACROSS SOUTHERN WI AND FAR NORTHEAST IL THIS EVENING IN
ASSOCIATION WITH THIS FEATURE...WITH AN AREA OF BKN-OVC CLOUD COVER
AS FAR SOUTH AS THE STREATOR-KANKAKEE-REMINGTON AREAS. MODEL
GUIDANCE PICKS UP ON THIS SHEARED WAVE...MOVING IT QUICKLY EAST OF
THE AREA BY/AFTER 06Z. THIS SHOULD ALLOW CLEARING FROM THE WEST
DURING THE LATE EVENING/OVERNIGHT HOURS...WITH BACK EDGE OF LOWER
CLOUDS NOW ROUGHLY MONROE WI-PERU IL. SOME PATCHY CIRRUS WILL
CONTINUE TO SPILL IN FROM THE NORTHWEST IN ASSOCIATION WITH UPPER
JET. BRISK WEST-NORTHWEST WINDS WILL DECREASE AFTER MIDNIGHT... AS
SURFACE RIDGE AXIS NOW OVER IA-MN BUILDS EAST IN RESPONSE TO RISING
HEIGHTS ALOFT IN WAKE OF DEPARTING UPPER TROUGH.
DESPITE LIGHTER WINDS...CLEARING SKIES AND SNOW COVER...WARM
ADVECTION IS ALREADY DEVELOPING ALOFT WEST OF THE MISSISSIPPI RIVER
AS WINDS BACK TO THE WEST-SOUTHWEST WITH APPROACHING WARM FRONT.
SURFACE DEW POINTS HOLDING IN THE LOW-MID TEENS ACROSS THE REGION
AND THOUGH THEY WILL LIKELY DROP A LITTLE BIT...HAVE BUMPED UP
FORECAST MINS 1-2 DEG ACROSS THE CWA TO NEAR 10 (WITH ARR/RPJ STILL
IN UPPER SINGLE DIGITS) ACROSS NORTH CENTRAL IL...AND TEENS MAINLY
ELSEWHERE.
OTHERWISE...ONLY CHANGE WAS TO INCREASE CLOUD COVER PERCENTAGE IN
SKY GRIDS A BIT WITH THE AFOREMENTIONED PATCH OF BKN-OVC CLOUDS
CURRENTLY OVER THE CWA. REMAINDER OF FORECAST APPEARS IN GOOD SHAPE
THROUGH TOMORROW.
RATZER
//PREV DISCUSSION...
327 PM CST
A VERY ACTIVE WEATHER PATTERN IS EXPECTED THROUGH THE WEEKEND WITH A
PLETHORA OF CONCERNS...INCLUDING PRECIP TIMING...TYPES AND
AMOUNTS...ESPECIALLY WITH THE WEEKEND SYSTEM.
AFTER ANOTHER CHILLY NIGHT TONIGHT UNDER PARTLY CLOUDY
SKIES...SOUTHWESTERLY WINDS WILL PICK UP...PRODUCING A WARMER DAY
ACROSS THE REGION FOR WEDNESDAY. IT APPEARS THAT TEMPERATURES WILL
CLIMB AT LEAST A COUPLE OF DEGREES ABOVE FREEZE ACROSS THE WHOLE
AREA. UNFORTUNATELY...THE EXTENSIVE SNOW PACK WILL KEEP TEMPERATURES
FOR WARMING MORE...AT LEAST UNTIL THURSDAY.
THE GUIDANCE IS HAVING TROUBLE WITH AGREEING ON THE PLACEMENT OF A
FRONTAL ZONE ON THURSDAY. THE NCEP MODELS...NAMELY THE GFS AND NAM
SUGGEST THAT THIS BOUNDARY WILL SAG SOUTHWARD TO NEAR THE I-80
CORRIDOR DURING THE DAY ON THURSDAY. THIS SOLUTION WOULD FAVOR
COOLER TEMPERATURES NEAR FREEZING ACROSS FAR NORTHERN ILLINOIS ON
THURSDAYS. HOWEVER...THE ECMWF SUGGESTS THAT THIS FRONT WILL REMAIN
ACROSS FAR SOUTHERN WISCONSIN...WITH SOUTHERLY FLOW AND WARMER
CONDITIONS CONTINUING. I HAVE CHOSEN TO FOLLOW CLOSER TO THE ECMWF
AS IT APPEARS THAT THE SURFACE LOW...WHICH THE FRONTAL ZONE EMANATES
FROM...ACROSS THE UPPER GREAT LAKES REGION IS BEING OVERDONE A BIT
BY THE NCEP MODELS...AND AS A CONSEQUENCE THEY DRIVE THE FRONT A BIT
FARTHER SOUTH ACROSS NORTHERN ILLINOIS. OVERALL...THE ECMWF WOULD
SUGGEST MUCH LESS OF A THREAT OF FREEZING DZ/RAIN AND LIKELY KEEP
IT LIQUID WITH SURFACE TEMPS ABOVE FREEZING. THE ONLY EXCEPTION TO
THIS MAY BE ACROSS FAR NORTHERN ILLINOIS.
OVERALL...THE INCREASE IN LOW LEVEL MOISTURE TO THE SOUTH OF THE
FRONTAL ZONE WILL LIKELY LEAD TO LOW CLOUDS AND EVEN FOG ACROSS MUCH
OF THE AREA LATER THURSDAY INTO THURSDAY NIGHT. A SURFACE WAVE IS
FORECAST TO MOVE ALONG THE FRONTAL ZONE THURSDAY NIGHT INTO
FRIDAY...AND THIS FINALLY ALLOW THE FRONT TO SHIFT SOUTHWARD ACROSS
THE AREA BY FRIDAY. IT APPEARS ISENTROPIC ASCENT WILL PRODUCE SOME
LIGHT PRECIP IN ASSOCIATION WITH THIS SURFACE WAVE THURSDAY NIGHT
INTO FRIDAY. AS THE COLD AIR BEGINS TO FILTER SOUTHWARD IT APPEARS
THE PRECIP COULD EITHER CHANGE OVER TO A PERIOD OF LIGHT SNOW...OR
FREEZING DRIZZLE. SOME OF THE FORECAST SOUNDINGS INDICATE THAT THE
DENDRITIC GROWTH ZONE WILL BE VOID OF DECENT MOISTURE...WHICH WOULD
FAVOR FREEZING DRIZZLE OVER LIGHT SNOW. I HAVE MENTIONED A SNOW OR
LIGHT FREEZING DRIZZLE CHANCE OVER NORTHERN ILLINOIS LATE THURSDAY
NIGHT INTO FRIDAY MORNING TO COVER THIS POTENTIAL.
OTHERWISE ATTENTION TURNS TO THE SYSTEM EXPECTED TO DIG ACROSS THE
SOUTHWEST..NEAR BAJA CALIFORNIA BY FRIDAY NIGHT. THIS DIGGING SYSTEM
IS EXPECTED TO TRANSITION A QUASI-ZONAL FLOW PATTERN ACROSS THE
CONUS INTO A SOUTHWESTERLY FLOW PATTERN ALOFT...AS DOWNSTREAM HEIGHT
RISES LEAD TO POSITIVE HEIGHT ANOMALIES AND RIDGING ACROSS THE
EASTERN CONUS. THIS PATTERN IS VERY CONDUCIVE TO PRODUCING A
SIGNIFICANT PRECIP EVENT ACROSS PORTIONS OF THE CENTRAL CONUS. A
STRONG AND IMPRESSIVE SOUTHERLY 60+ KT LOW LEVEL JET IS PROGGED TO
DEVELOP BY SATURDAY IN RESPONSE TO THE PATTERN SHIFT...WITH LOW
PRESSURE DEVELOPING ACROSS TEXAS. THIS LOW LEVEL JET WILL TRANSPORT
COPIOUS AMOUNTS OF MOISTURE NORTHWARD ACROSS THE MISSISSIPPI AND OHIO
VALLEYS.
OVERALL...THIS CONTINUES TO BE A VERY COMPLEX FORECAST AS
THE SYSTEM APPEARS THAT IT WILL...AT LEAST TEMPORALLY...SEPARATE
ITSELF FROM THE MAIN SOUTHERN STREAM FLOW. MUCH OF THE GUIDANCE IS
IN FAIR AGREEMENT WITH TAKING THIS SYSTEM EAST-NORTHEASTWARD ACROSS
THE TEXAS PANHANDLE LATE SATURDAY AND THEN MERGING BACK INTO THE
MAIN TROUGH BY SUNDAY AS IT MOVES ACROSS MISSOURI. OVERALL...IN THE
LOWER LEVELS...THIS LOOKS TO SET UP A FRONTAL BOUNDARY RIGHT ACROSS
THE CENTRAL STATES...WITH AN ELONGATED AREA OF SURFACE LOW PRESSURE
LIKELY TO TRANSITION ALONG THE BOUNDARY THROUGH THE WEEKEND. STRONG
MOISTURE CONVERGENCE AND FRONTOGENESIS IS LIKELY IN THE VICINITY OF THE
SOUTHWEST TO NORTHEAST ORIENTED BOUNDARY...ALONG THE NOSE OF THE LOW
LEVEL JET. THIS WILL LIKELY RESULT IN HEAVY PRECIPITATION ACROSS AT
LEAST PORTIONS OF THE AREA LATE SATURDAY INTO SUNDAY. THE MAIN
QUESTIONS AT THIS POINT CONTINUE TO BE...WHAT FORM WILL THE PRECIP
BE? I CONTINUE TO FOLLOWER CLOSER TO THE ECMWF SOLUTION FOR THE
SYSTEM AS IT HAS BEEN VERY GOOD LATELY.
THE MAIN CONCERNS I HAVE IS THE THERMAL PROFILE WITH THIS SYSTEM. IT
IS POSSIBLE THAT THE PRECIP BEGINS AS A WINTER MIX OF RAIN FREEZING
RAIN SLEET AND SNOW...ESPECIALLY ACROSS THE NORTH. MY SOUTHERN
COUNTIES MAY BECOME WARM ENOUGH TO RESULT IN MAINLY RAIN...AT LEAST
THROUGH SATURDAY NIGHT. THERE ARE DEFINITELY SIGNS THAT THIS
SYSTEM COULD TRANSITION OVER TO FREEZING RAIN AND THEN SNOW
SATURDAY NIGHT ACROSS NORTHERN ILLINOIS AS THE SYSTEM TRYS TO PULL
IN COLDER AIR IN THE LOWER LEVELS FOR THE NORTH. SIGNIFICANT
ACCUMULATIONS ARE CERTAINLY POSSIBLE ACROSS PORTIONS OF NORTHERN
ILLINOIS. HOWEVER...THE THERM PROFILE...AND HENCE WHERE SNOW VERSE
RAIN WILL FALL COULD EASILY CHANGE IN FUTURE FORECASTS. SO...IN
SPITE OF THE FACT CONFIDENCE IS INCREASING THAT WE WILL SEE A
DECENT PRECIP EVENT ACROSS THE AREA. CONFIDENCE ON PRECIP
TYPE...AND WHERE THE RAIN/VERSES HEAVY SNOW LINE SETS UP REMAINS
LOW AT THIS TIME. FOR THESE REASONS...IT IS TOO EARLY TO START
MENTIONING AMOUNTS OF SNOW OR ICE FOR ANY GIVEN AREAS.
THE AMOUNT OF PRECIP WITH THIS SYSTEM COULD CAUSE HYDRO
ISSUES...WITH PRECIP AMOUNTS POSSIBLY EXCEEDING AN INCH OR TWO
ACROSS PORTIONS OF THE AREA. THIS WILL HAVE TO BE
WATCHED...ESPECIALLY IF THE PRECIP FALLS AS RAIN ON TOP OF ANY
REMAINING SNOW PACK.
ANOTHER SHOT OF COLDER AIR WILL OVERSPREAD THE AREA EARLY NEXT WEEK
IN THE WAKE OF THIS SYSTEM...WITH HIGH PRESSURE BUILDING IN ACROSS
THE REGION.
KJB
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* GUSTY SOUTH WINDS DEVELOP THIS AFTN WITH MAX GUSTS BTWN 20 AND
25 KT.
* MVFR TO PSBL IFR CIGS AND MVFR FOG DEVELOP THIS EVENING.
* COULD SEE -DZ OR -FZDZ EARLY THURSDAY MORNING.
JEE
//DISCUSSION...UPDATED 06Z...
A RIDGE OF HIGH PRESSURE IS APPROACHING FROM THE WEST WITH VFR
CIGS THINNING OUT OVER THE NEXT HOUR OR SO. WINDS WILL SLOWLY
BECOME SOUTH BY THIS AFTERNOON AND BEGIN GUSTING TO 20 TO 25 KT. A
TROUGH OF LOW PRESSURE THEN MOVES IN FROM THE WEST TOMORROW
EVENING. THE UPPER LEVEL PRESSURE GRADIENT REMAINS STRONG SO OCNL
GUSTS TO ARND 20 KT ARE POSSIBLE OVERNIGHT. WINDS WILL ALSO BECOME
MORE SSW OVERNIGHT.
WARM AIR AND MOISTURE WILL BE ADVECTED INTO THE REGION RESULTING
IN CIGS LOWERING AND FOG DEVELOPMENT. FIRST...THE WARM AIR WILL
INTERACT WITH THE SNOW PACK CREATING FOG. NOT SURE HOW DENSE THE
FOG WILL BE AT THIS POINT...SO KEPT MVFR VSBYS GOING. THINKING ORD
AND MDW WILL REMAIN OUT OF THE DENSER FOG AS THE TYPICALLY
DO...BUT THE REMAINING TERMINALS WILL LIKELY SEE DENSER FOG THEN
FORECAST. NOT SURE HOW DENSE AT THIS TIME. NOW FOR CIGS...GUIDANCE
INDICATES MVFR IF NOT IFR CIGS ARE LIKELY TOMORROW EVENING AND
OVERNIGHT. WILL REFINE THE CIG HEIGHTS AS CONFIDENCE GROWS.
SOUNDINGS ALSO TRY TO SUGGEST THE ADDED MOISTURE MAY PRODUCE
DRIZZLE OR FREEZING DRIZZLE...BUT NOT SURE HOW MUCH OF THAT
MOISTURE WILL BE FOG VS. PRECIP. THEREFORE LEFT THE TAFS DRY FOR
NOW. ALSO NOTE DRIZZLE VS. FREEZING DRIZZLE WILL DEPEND ON
TEMPS...AND RIGHT NOW TEMPS LOOK LIKE THEY WILL BE RIGHT AROUND
FREEZING.
JEE
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN TAFS THROUGH 00Z.
* MEDIUM CONFIDENCE IN GUSTS PERSISTING OVERNIGHT...GUSTS MAY BE
LESS FREQUENT THAN FORECAST.
* HIGH CONFIDENCE IN AT LEAST MVFR CIGS THIS EVENING...LOW
CONFIDENCE IN HOW LOW CIGS WILL FALL. IFR OR LOWER IS PSBL.
* HIGH CONFIDENCE IN FOG THIS EVENING...LOW CONFIDENCE IN HOW
THICK FOG WILL BE AND TIMING.
* LOW CONFIDENCE IN -DZ OR -FZDZ OCCURRING AND TIMING EARLY
THURSDAY MORNING.
JEE
//OUTLOOK FOR ORD/MDW FOR 12Z THURSDAY-12Z TUESDAY...UPDATED 00Z...
THURSDAY...IFR/LIFR LIKELY. CHANCE OF -RA/DZ WITH AREAS OF FOG.
FRIDAY...IFR LIKELY. CHANCE OF -RA/-SN.
SATURDAY...IFR POSSIBLE. CHANCE OF WINTRY MIX DURING THE
DAY...THEN SNOW AT NIGHT.
SUNDAY...IFR POSSIBLE. SNOW LIKELY.
MONDAY...MVFR CEILINGS POSSIBLE.
RODRIGUEZ
&&
.MARINE...
315 PM CST
WILL LEAVE HEADLINES AS IS THIS EVENING FOR MARGINAL WESTERLY GALES
ON SOUTHERN PART OF THE LAKE...BUT ALLOW EVENING SHIFT TO ASSESS AND
POSSIBLY CANCEL EARLY. SMALL CRAFT ADVISORY FROM WINTHROP HARBOR TO
GARY IS IN GOOD SHAPE. THEN CONCERN SHIFTS TO LIKELY SOUTH-SOUTHWEST
GALES ON WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT COURTESY OF STRONG
PRESSURE FALLS AND A TIGHT PRESSURE GRADIENT WITH LOW PRESSURE
APPROACHING FROM THE WEST AND HIGH PRESSURE OVER THE OH VALLEY. HAVE
HIGHEST CONFIDENCE IN GALES DEVELOPING ON THE SOUTH HALF WITH
SOMEWHAT LESSER CONFIDENCE ON THE NORTH IN TERMS OF DURATION AND
SEEING PREVAILING GALES...BUT FELT IT WAS PRUDENT TO ISSUE A GALE
WATCH FOR THE ENTIRE OPEN LAKE FROM 21Z WEDS TO 10Z THURS. WILL
LIKELY NEED A SCA FOR THE NEAR SHORE ZONES DURING THIS TIME. AFTER
GALE IS DROPPED FOR GARY TO MI CITY NSH ZONE THIS EVENING...ITS
POSSIBLE THAT THE SCA MAY JUST BE EXTENDED THROUGH TOMORROW NIGHT
FOR THIS ZONE.
A COLD FRONT WILL THEN SHIFT SOUTH DOWN THE LAKE THURSDAY THROUGH
THURSDAY NIGHT..WITH LARGE VARIANCE AMONGST FORECAST GUIDANCE IN
THE TIMING OF THIS FRONT. HAVE FAVORED A SLOWER MOVEMENT OF THE
FRONT DOWN THE SOUTHERN PORTION OF THE LAKE WITH THIS FORECAST
ISSUANCE. THERE IS SOME POTENTIAL FOR FAIRLY STRONG BUT LIKELY
SUB-GALE NORTHERLY WINDS BEHIND THE FRONT. WEAK HIGH PRESSURE WILL
THEN RESULT IN LIGHTER WINDS FRIDAY NIGHT INTO SATURDAY.
HOWEVER...ANOTHER STRONGER SYSTEM THEN LOOKS TO MOVE FROM THE OHIO
VALLEY TOWARD THE CENTRAL LAKES LATE SATURDAY INTO SUNDAY. THE
POTENTIAL CERTAINLY EXISTS FOR NORTHEAST TO NORTH GALES IN
ASSOCIATION WITH THIS SYSTEM DEPENDING ON ITS ULTIMATE TRACK AND
STRENGTH...BUT FOR NOW HAVE INCREASED WINDS TO 30 KT.
RC
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 10 AM WEDNESDAY.
SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO GARY IN UNTIL
MIDNIGHT WEDNESDAY.
GALE WATCH...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...3 PM WEDNESDAY TO 4 AM
THURSDAY.
&&
$$
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Area Forecast Discussion
National Weather Service Lincoln IL
1111 PM CST Tue Dec 17 2013
.DISCUSSION...
ISSUED 815 PM CST Tue Dec 17 2013
Surface high pressure over eastern Kansas and western Missouri
early this evening will track to our south tonight. A very dry
air mass was advecting southeast into central Illinois this
evening with mid to upper teens common over the northern half of
the forecast area. The dry air combined with just enough wind
overnight should keep any significant fog problems at bay. Last
few runs of the HRRR model have backed off with the low vsbys in
parts of our area but with the ridge axis expected to be right
over our area by 12z, not that confident to remove the current
patchy fog wording in the grids late tonight.
As the surface high shifts off to our southeast tomorrow, we can
expect an increasing southerly wind across the entire area which
should help push temperatures into the upper 30s north to the
middle 40s southwest. Have made some minor adjustments to the
evening dew points and temperatures, as well as backing off the
fog wording until the 4am to 8am time frame. Updated zones should
be out soon.
&&
.AVIATION...
ISSUED 1110 PM CST Tue Dec 17 2013
Except for the potential for a brief period of fog in the 10z-14z
time frame...VFR conditions are expected to prevail. Another issue
to address will be the threat for low level wind shear tomorrow
night as the surface winds decouple while winds around 1500 feet
remain out of the southwest at 40-50 kts. Surface winds tonight
will continue from a westerly direction but continue to slowly
decrease as the night wears on with the surface ridge axis passing
thru central IL around dawn. Then, winds will back into a southwest
to south direction Wednesday morning and increase to between 12 and
17 kts by early afternoon, with a few gusts up to 22 kts thru the
mid afternoon hours before diminishing to around 12 kts after
dark. With surface temperatures expected above freezing in all areas
tomorrow, there should be quite a bit of melting of the snow, which
in turn may bring about an increasing chance for the development
of fog and low clouds late Wednesday night. However, it appears
southerly winds will hold up enough to keep it out of the forecast
thru 06z Thu.
Smith
&&
.PREV DISCUSSION...
ISSUED 300 PM CST Tue Dec 17 2013
The short term will be highlighted by a warming trend through mid
week. Fog may become an issue as the snow melts over the next few
days. A cold front is still slated for Friday morning, with a
major winter storm taking aim on the area for the weekend. Precip
type issues remain the biggest challenge with that storm. The 12z
guidance has generally trended warmer on Sat and Sat night, which
means rain longer and farther north, with a band of freezing rain
in our northern area. Snow chances may hold off until very late
Sat night and possibly until Sunday as the colder air finally
flows into central IL. Snow amounts on the NW side of this system
could be very high, with the latest trends putting that band just
to our northwest. Any shift in the placement of the stationary
front and track of the low up along the front will be critical to
precip type distribution and amounts of snow and ice.
SHORT TERM...Tonight through Friday night.
The quick clipper snows from today should be out of our southeast
counties by evening. We will not mention any snow in the worded
zones as a result.
Fog potential tonight does not appear as high as previous model
runs, although the models have not been handling the ground level
moisture very well at all. We kept a mention of patchy fog in our
grids for tonight, but do not expect any widespread dense fog
despite very light winds and clear skies.
Wednesday will see high pressure sliding east of IL and southerly
winds increasing. Warm advection flows will intensify in the
afternoon, helping to push temperatures into the 40s in many
areas. Snow cover will reduce the effective heating of the sun,
with energy going to melting the snow. That may keep highs in the
upper 30s over areas with deeper snow. The additional ground level
moisture should help fog develop Wed night, despite some steadier
south winds overnight.
Fog should linger Thursday morning as mid and upper level moisture
increases ahead of the approaching cold front. Rain showers should
hold off until afternoon when isentropic lift intensifies due to
45kts of flow up the 295k surface. Rain should generally remain
north of Lincoln in proximity to the developing mid-level warm
front and nose of the theta-e ridge.
There remains some concern as to the extent of freezing rain later
Thursday night into Friday morning as surface temps northwest of
Peoria dip below freezing behind the cold front. We kept a mention
of FZRA in that area, with a thin layer of icing possible.
Precipitation chances should become confined mainly to the
southeast half of our area Friday afternoon and Friday night as
the cold front and shortwave shift east. Once again, any rain
falling into the night could transition to freezing rain along
and north of I-72.
The cold front is projected to stall out just to the southeast of
Illinois, in prep for a return push northward when the weekend
storm approaches.
LONG TERM...Saturday through Tuesday.
A surge of warm air and moisture in the mid levels will strengthen
on Saturday, pushing the front back north as a warm front. Rain
will re-develop or advance northward during the day, with freezing
rain possible in the morning north of I-72 before surface temps
climb above freezing. All or our forecast area except maybe around
Galesburg should climb above freezing during the afternoon,
keeping all precipitation as rain. The timing and speed of the low
riding up the front will dictate how soon that colder air will be
drawn into the northern edges of the storm and change the rain to
freezing rain and eventually snow. Saturday night could see an
extended period of freezing rain in a band from SW to NE across
our counties, including areas from Rushville/Jacksonville/
Springfield north to Canton/Peoria and east to Bloomington and
Champaign. Ice amounts could reach over a quarter inch in some
areas, depending on how soon the cold air arrives at low levels.
Snow is expected to develop on the NW fringes of our area as soon
as Saturday evening, but more likely after midnight into Sunday. A
couple of inches of snow could accumulate on Sunday in areas west
of I-57, with lesser amounts toward I-57 and east. A band of
deformation snows could increase those amounts in bands west of
I-55.
There remains a great deal of uncertainty with the weekend storm
system, but the trends have been for a warmer solution in our
counties, even from the previously colder ECMWF.
Dry and colder conditions will follow the storm, and should set up
better travel conditions for Christmas Eve day through Christmas,
and possibly longer.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS INDIANAPOLIS IN
928 PM EST THU DEC 19 2013
.UPDATE...
THE NEAR TERM AND AVIATION SECTIONS HAVE BEEN UPDATED BELOW.
&&
.SYNOPSIS...
ISSUED AT 300 PM EST THU DEC 19 2013
A LOW PRESSURE TROUGH FROM TEXAS TO THE GREAT LAKES WILL WILL SETTLE
INTO THE OHIO VALLEY THIS WEEKEND. A COUPLE OF SHORT WAVES EMBEDDED
WITHIN THE TROUGH WILL PRODUCE SEVERAL SURGES OF RAINFALL WITH THE
INITIAL RAIN BEING LIGHT THROUGH FRIDAY EVENING. THE SECOND WAVE
WILL BRING SUBSTANTIAL RAIN SATURDAY BEFORE IT DEPARTS THE REGION
SUNDAY. COLD HIGH PRESSURE WILL BUILD INTO THE REGION TO START THE
WEEK. A WEAK LOW PRESSURE TROUGH WILL MOVE INTO THE GREAT LAKES AND
OHIO VALLEY NEXT THURSDAY AND MAY PRODUCE SOME LIGHT SNOW.
ABOVE NORMAL TEMPERATURES WILL PREVAIL INTO FRIDAY THEN RETURN TO
NORMAL AND THEN BELOW NORMAL BY SUNDAY NIGHT AND REMAIN BELOW NORMAL
MOST OF NEXT WEEK.
&&
.NEAR TERM /REST OF TONIGHT/...
ISSUED AT 928 PM EST THU DEC 19 2013
DECENT LIFT ONGOING ACROSS THE AREA THIS EVENING ALONG A 35-40 KT
LOW LEVEL JET...HOWEVER DEEPER MOISTURE FOR PRECIPITATION IS STILL
LACKING A BIT BASED ON THIS EVENING/S UPPER AIR. STILL APPEARS SOME
PRECIPITATION WILL DEVELOP LATER TONIGHT UNDER SUSTAINED WARM/MOIST
ADVECTION...BUT IT MAY HOLD OFF UNTIL THE EARLY MORNING HOURS ON
FRIDAY.
TEMPERATURES HAVE HELD NEARLY STEADY THIS EVENING...AND WITH WARM
ADVECTION CONTINUING TONIGHT...THINK IT WILL BE TOUGH FOR
TEMPERATURES TO REACH THE CURRENT FORECAST LOWS...ESPECIALLY OVER
THE SOUTH. WILL ALLOW FOR A SLIGHT FALL TO THE TEMPERATURES FOR THE
REST OF THE NIGHT.
PREVIOUS DISCUSSION FOLLOWS.
MODELS SIMILAR AND WILL USE A BLEND. FIRST UPPER WAVE AND ASSOCIATED
SURFACE LOW WILL LIFT NORTHEAST TO NEAR QUINCY BY FRIDAY MORNING.
INCREASING LIFT WILL CONTINUE MOISTENING ATMOSPHERE COLUMN AND BY
MIDNIGHT SHOULD BEGIN TO SPREAD VERY LIGHT RAIN ACROSS CENTRAL
INDIANA. MILD SOUTHWEST FLOW CONTINUING WILL RESULT IN MINIMUM
TEMPERATURES AT OR NEAR LAST NIGHTS VALUES OR IN THE UPPER 30S TO
LOWER 40S.
&&
.SHORT TERM /FRIDAY THROUGH SUNDAY/...
ISSUED AT 300 PM EST THU DEC 19 2013
ISSUE FOR THIS PERIOD IS WHERE THE HEAVY RAIN AXIS WILL END UP.
MODELS STILL VARY A BIT WITH DIFFERENCES IN SURFACE LOW TRACK
WHICH TIES TO HEAVY RAIN AXIS. WILL CONTINUE TO USE A BLEND OF
MODELS TO AVERAGE RAIN AMOUNTS ACROSS THE FORECAST AREA AND
INCLUDE HPC EXCESSIVE RAINFALL GUIDANCE AS WELL AS RIVER FORECAST
CENTER QUANTITATIVE PRECIPITATION FORECASTS AS PART OF BLEND.
FRIDAY AND FRIDAY NIGHT...
DURING THIS TIME FRAME ALL MODELS LIFT THE INITIAL SURFACE LOW FROM
THE MID MISSISSIPPI VALLEY FRIDAY MORNING TO THE NEW ENGLAND
SATURDAY MORNING. THIS WAVE WILL PRODUCE PERIODS OF LIGHT RAIN AND
WILL SETTLE A COLD FRONT SURFACE BOUNDARY TO A POSITION NEAR THE
OHIO RIVER. ON SOUTHWEST WINDS...TEMPERATURES SURGE INTO THE 50S FOR
MOST AREAS FRIDAY THEN SETTLE BACK INTO THE MID 30S NORTH TO MID 40S
SOUTH BY DAYBREAK SATURDAY.
SATURDAY INTO SUNDAY MORNING...
MODELS DIFFER SOME ON TRACK OF THE MAIN WAVE AND SURFACE LOW LIFTING
INTO THE REGION SO WILL AGAIN CONTINUE A BLEND BUT LEAN TOWARDS A
TRACK UP INTO AND ACROSS OUR SOUTHERN COUNTIES.
ALL MODELS SHOW A STRONG THERMAL BOUNDARY AND STRONG JET DYNAMICS
YIELDING SUBSTANTIAL LIFT OF UNUSUALLY MOIST AIR ORIGINATING IN LOW
LATITUDES BASED ON WATER VAPOR IMAGES...RESULTING IN SUBSTANTIAL AND
PROLONGED RAINS FROM SATURDAY MORNING INTO SUNDAY MORNING. AXIS OF
HEAVIEST PRECIPITATION WILL BE PLACED NEAR BUT JUST SOUTH HPC
PRECIPITATION GUIDANCE IN LINE WITH RIVER FORECAST CENTER. RAIN
AMOUNTS FROM 2 INCHES NORTH TO 4 INCHES SOUTH STILL APPEAR LIKELY
DURING THIS 24 HOUR PERIOD. AGAIN MODEL DIFFERENCES SUGGEST A TRACK
FURTHER NORTH THAN THIS PUSHES HEAVY RAIN AXIS ALONG AND NORTH OF
I-70 AND ALSO BRINGS MILDER TEMPERATURES SATURDAY NIGHT AND SUNDAY
CLOSER TO I-70. DRY SLOT WRAPS IN AFTER MIDNIGHT SATURDAY NIGHT WILL
BRING AND END TO HEAVIEST RAIN.
SUNDAY...
DRY SLOT STILL IN PLAY SUNDAY AS COLD FRONT SWEEPS COLDER AIR IN
BEGINNING SUNDAY MORNING. WRAP AROUND CLOUD SHIELD WILL MOVE INTO
CENTRAL INDIANA SUNDAY AFTERNOON AND BRING A MIX OF LIGHTER RAIN
SHOWERS AND SNOW SHOWERS THAT TRANSITION INTO ALL SNOW SHOWERS
BEFORE NIGHTFALL. NO SNOW ACCUMULATION IS EXPECTED.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
ISSUED AT 205 PM EST THU DEC 19 2013
LONG TERM PERIOD WILL GENERALLY BE A QUIET ONE WITH STRONG HIGH
PRESSURE TRAVERSING THE REGION IN BETWEEN THE VERY TAIL END OF OUR
WEEKEND FRONTAL SYSTEM SUNDAY NIGHT...AND THE NEXT FRONTAL SYSTEM
WHICH LOOKS TO HOLD OFF UNTIL WEDNESDAY NIGHT INTO THURSDAY.
THUS...A DRY FORECAST WILL HOLD THROUGH MUCH OF THE PERIOD.
VERY LOW POPS EARLY IN THE PERIOD REASONABLE...AND ANY REMAINING
PRECIP SHOULD BE ALL SNOW BY THEN. ADDITIONALLY...LATE WEEK SYSTEM
SHOULD BE COLD ENOUGH TO BE ALL SNOW AS WELL. NOTHING SIGNIFICANT
APPEARING ON THE HORIZON JUST YET.
TEMPERATURES WERE INITIALIZED REASONABLY...WITH A BIT OF A ROLLER
COASTER RIDE THROUGH THE HOLIDAY WEEK. SEE LITTLE OPPORTUNITY FOR
IMPROVEMENT OVER A BLEND.
&&
.AVIATION /DISCUSSION FOR THE 200300Z KIND TAF UPDATE/...
ISSUED AT 928 PM EST THU DEC 19 2013
NO SIGNIFICANT CHANGES MADE AT THIS TIME. PREVIOUS DISCUSSION
FOLLOWS.
STEADILY DETERIORATING CONDITIONS FOR AVIATORS INTO THE
OVERNIGHT...WITH LIFR CONDITIONS FOR MUCH OF FRIDAY.
FRONTAL BOUNDARY EXTENDING FROM SOUTHERN LOWER MICHIGAN W/SW INTO
NORTHERN MISSOURI EARLY THIS EVENING. RAPID MOISTURE ADVECTION
CONTINUES INTO THE OHIO VALLEY COURTESY OF A BROAD LOW LEVEL JET
EXTENDING ALL THE WAY BACK INTO THE WESTERN GULF. CEILINGS HAVE
GRADUALLY LOWERED THROUGH THE AFTERNOON...AND ARE NOW BEGINNING TO
SEE MVFR STRATUS DEVELOP EARLY THIS EVENING. EXPECT THIS TREND TO
CONTINUE WITH STRATUS BECOMING WIDESPREAD AND LOWERING FURTHER
OVERNIGHT AS LOWER LEVELS BECOME SATURATED.
HAVE TRENDED WITH THE RAP FOR THE FIRST 9-12 HOURS OF THE
FORECAST AS IT APPEARS TO HAVE A BETTER HANDLE ON LOW LEVEL WINDS
AND MOISTURE. HAVE SPED UP ARRIVAL OF IFR AND LOWER CONDITIONS BY
SEVERAL HOURS FROM PREVIOUS FORECAST AT ALL TERMINALS AS RAIN
SHOWERS GRADUALLY BECOME WIDESPREAD LATE TONIGHT. ANTICIPATE LIFR
CEILINGS TO BECOME PREVALENT TOWARDS DAYBREAK AND PERSIST ALL DAY
FRIDAY AS THE LOW LEVEL INVERSION STRENGTHENS. RAIN WILL CONTINUE ON
FRIDAY AS WELL AS A SURFACE WAVE TRAVERSES THE NEARLY STATIONARY
BOUNDARY JUST TO THE NORTHWEST OF THE TERMINALS. ALL IN ALL...VERY
POOR FLYING CONDITIONS OVER CENTRAL INDIANA ON FRIDAY.
LAST ISSUE FOCUSES ON LOW LEVEL WIND SHEAR WHICH WILL BECOME A
FACTOR ONCE AGAIN THIS EVENING WITH THE ARRIVAL OF THE LOW LEVEL
JET. RAP INDICATING POTENTIAL FOR SOUTHWEST WINDS TO APPROACH
60KTS OVERNIGHT IN THE 2-3KFT LAYER. LLWS WILL BE A CONCERN FOR
AVIATORS WELL INTO FRIDAY AS THE LOW LEVEL JET DOES NOT WEAKEN
UNTIL THE PASSAGE OF THE SURFACE WAVE DURING THE AFTERNOON.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH FROM LATE FRIDAY NIGHT THROUGH SUNDAY MORNING FOR
INZ021-028>031-035>049-051>057-060>065-067>072.
&&
$$
SYNOPSIS...TUCEK
NEAR TERM...TUCEK/JAS
SHORT TERM...TUCEK
LONG TERM...NIELD
AVIATION...RYAN
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AREA FORECAST DISCUSSION
NWS INDIANAPOLIS IN
617 PM EST THU DEC 19 2013
.UPDATE...
THE AVIATION SECTION HAS BEEN UPDATED BELOW.
&&
.SYNOPSIS...
ISSUED AT 300 PM EST THU DEC 19 2013
A LOW PRESSURE TROUGH FROM TEXAS TO THE GREAT LAKES WILL WILL SETTLE
INTO THE OHIO VALLEY THIS WEEKEND. A COUPLE OF SHORT WAVES EMBEDDED
WITHIN THE TROUGH WILL PRODUCE SEVERAL SURGES OF RAINFALL WITH THE
INITIAL RAIN BEING LIGHT THROUGH FRIDAY EVENING. THE SECOND WAVE
WILL BRING SUBSTANTIAL RAIN SATURDAY BEFORE IT DEPARTS THE REGION
SUNDAY. COLD HIGH PRESSURE WILL BUILD INTO THE REGION TO START THE
WEEK. A WEAK LOW PRESSURE TROUGH WILL MOVE INTO THE GREAT LAKES AND
OHIO VALLEY NEXT THURSDAY AND MAY PRODUCE SOME LIGHT SNOW.
ABOVE NORMAL TEMPERATURES WILL PREVAIL INTO FRIDAY THEN RETURN TO
NORMAL AND THEN BELOW NORMAL BY SUNDAY NIGHT AND REMAIN BELOW NORMAL
MOST OF NEXT WEEK.
&&
.NEAR TERM /TONIGHT/...
ISSUED AT 300 PM EST THU DEC 19 2013
MODELS SIMILAR AND WILL USE A BLEND. FIRST UPPER WAVE AND ASSOCIATED
SURFACE LOW WILL LIFT NORTHEAST TO NEAR QUINCY BY FRIDAY MORNING.
INCREASING LIFT WILL CONTINUE MOISTENING ATMOSPHERE COLUMN AND BY
MIDNIGHT SHOULD BEGIN TO SPREAD VERY LIGHT RAIN ACROSS CENTRAL
INDIANA. MILD SOUTHWEST FLOW CONTINUING WILL RESULT IN MINIMUM
TEMPERATURES AT OR NEAR LAST NIGHTS VALUES OR IN THE UPPER 30S TO
LOWER 40S.
&&
.SHORT TERM /FRIDAY THROUGH SUNDAY/...
ISSUED AT 300 PM EST THU DEC 19 2013
ISSUE FOR THIS PERIOD IS WHERE THE HEAVY RAIN AXIS WILL END UP.
MODELS STILL VARY A BIT WITH DIFFERENCES IN SURFACE LOW TRACK
WHICH TIES TO HEAVY RAIN AXIS. WILL CONTINUE TO USE A BLEND OF
MODELS TO AVERAGE RAIN AMOUNTS ACROSS THE FORECAST AREA AND
INCLUDE HPC EXCESSIVE RAINFALL GUIDANCE AS WELL AS RIVER FORECAST
CENTER QUANTITATIVE PRECIPITATION FORECASTS AS PART OF BLEND.
FRIDAY AND FRIDAY NIGHT...
DURING THIS TIME FRAME ALL MODELS LIFT THE INITIAL SURFACE LOW FROM
THE MID MISSISSIPPI VALLEY FRIDAY MORNING TO THE NEW ENGLAND
SATURDAY MORNING. THIS WAVE WILL PRODUCE PERIODS OF LIGHT RAIN AND
WILL SETTLE A COLD FRONT SURFACE BOUNDARY TO A POSITION NEAR THE
OHIO RIVER. ON SOUTHWEST WINDS...TEMPERATURES SURGE INTO THE 50S FOR
MOST AREAS FRIDAY THEN SETTLE BACK INTO THE MID 30S NORTH TO MID 40S
SOUTH BY DAYBREAK SATURDAY.
SATURDAY INTO SUNDAY MORNING...
MODELS DIFFER SOME ON TRACK OF THE MAIN WAVE AND SURFACE LOW LIFTING
INTO THE REGION SO WILL AGAIN CONTINUE A BLEND BUT LEAN TOWARDS A
TRACK UP INTO AND ACROSS OUR SOUTHERN COUNTIES.
ALL MODELS SHOW A STRONG THERMAL BOUNDARY AND STRONG JET DYNAMICS
YIELDING SUBSTANTIAL LIFT OF UNUSUALLY MOIST AIR ORIGINATING IN LOW
LATITUDES BASED ON WATER VAPOR IMAGES...RESULTING IN SUBSTANTIAL AND
PROLONGED RAINS FROM SATURDAY MORNING INTO SUNDAY MORNING. AXIS OF
HEAVIEST PRECIPITATION WILL BE PLACED NEAR BUT JUST SOUTH HPC
PRECIPITATION GUIDANCE IN LINE WITH RIVER FORECAST CENTER. RAIN
AMOUNTS FROM 2 INCHES NORTH TO 4 INCHES SOUTH STILL APPEAR LIKELY
DURING THIS 24 HOUR PERIOD. AGAIN MODEL DIFFERENCES SUGGEST A TRACK
FURTHER NORTH THAN THIS PUSHES HEAVY RAIN AXIS ALONG AND NORTH OF
I-70 AND ALSO BRINGS MILDER TEMPERATURES SATURDAY NIGHT AND SUNDAY
CLOSER TO I-70. DRY SLOT WRAPS IN AFTER MIDNIGHT SATURDAY NIGHT WILL
BRING AND END TO HEAVIEST RAIN.
SUNDAY...
DRY SLOT STILL IN PLAY SUNDAY AS COLD FRONT SWEEPS COLDER AIR IN
BEGINNING SUNDAY MORNING. WRAP AROUND CLOUD SHIELD WILL MOVE INTO
CENTRAL INDIANA SUNDAY AFTERNOON AND BRING A MIX OF LIGHTER RAIN
SHOWERS AND SNOW SHOWERS THAT TRANSITION INTO ALL SNOW SHOWERS
BEFORE NIGHTFALL. NO SNOW ACCUMULATION IS EXPECTED.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
ISSUED AT 205 PM EST THU DEC 19 2013
LONG TERM PERIOD WILL GENERALLY BE A QUIET ONE WITH STRONG HIGH
PRESSURE TRAVERSING THE REGION IN BETWEEN THE VERY TAIL END OF OUR
WEEKEND FRONTAL SYSTEM SUNDAY NIGHT...AND THE NEXT FRONTAL SYSTEM
WHICH LOOKS TO HOLD OFF UNTIL WEDNESDAY NIGHT INTO THURSDAY.
THUS...A DRY FORECAST WILL HOLD THROUGH MUCH OF THE PERIOD.
VERY LOW POPS EARLY IN THE PERIOD REASONABLE...AND ANY REMAINING
PRECIP SHOULD BE ALL SNOW BY THEN. ADDITIONALLY...LATE WEEK SYSTEM
SHOULD BE COLD ENOUGH TO BE ALL SNOW AS WELL. NOTHING SIGNIFICANT
APPEARING ON THE HORIZON JUST YET.
TEMPERATURES WERE INITIALIZED REASONABLY...WITH A BIT OF A ROLLER
COASTER RIDE THROUGH THE HOLIDAY WEEK. SEE LITTLE OPPORTUNITY FOR
IMPROVEMENT OVER A BLEND.
&&
.AVIATION /DISCUSSION FOR 200000Z TAF ISSUANCE/...
ISSUED AT 617 PM EST THU DEC 19 2013
STEADILY DETERIORATING CONDITIONS FOR AVIATORS INTO THE
OVERNIGHT...WITH LIFR CONDITIONS FOR MUCH OF FRIDAY.
FRONTAL BOUNDARY EXTENDING FROM SOUTHERN LOWER MICHIGAN W/SW INTO
NORTHERN MISSOURI EARLY THIS EVENING. RAPID MOISTURE ADVECTION
CONTINUES INTO THE OHIO VALLEY COURTESY OF A BROAD LOW LEVEL JET
EXTENDING ALL THE WAY BACK INTO THE WESTERN GULF. CEILINGS HAVE
GRADUALLY LOWERED THROUGH THE AFTERNOON...AND ARE NOW BEGINNING TO
SEE MVFR STRATUS DEVELOP EARLY THIS EVENING. EXPECT THIS TREND TO
CONTINUE WITH STRATUS BECOMING WIDESPREAD AND LOWERING FURTHER
OVERNIGHT AS LOWER LEVELS BECOME SATURATED.
HAVE TRENDED WITH THE RAP FOR THE FIRST 9-12 HOURS OF THE
FORECAST AS IT APPEARS TO HAVE A BETTER HANDLE ON LOW LEVEL WINDS
AND MOISTURE. HAVE SPED UP ARRIVAL OF IFR AND LOWER CONDITIONS BY
SEVERAL HOURS FROM PREVIOUS FORECAST AT ALL TERMINALS AS RAIN
SHOWERS GRADUALLY BECOME WIDESPREAD LATE TONIGHT. ANTICIPATE LIFR
CEILINGS TO BECOME PREVALENT TOWARDS DAYBREAK AND PERSIST ALL DAY
FRIDAY AS THE LOW LEVEL INVERSION STRENGTHENS. RAIN WILL CONTINUE ON
FRIDAY AS WELL AS A SURFACE WAVE TRAVERSES THE NEARLY STATIONARY
BOUNDARY JUST TO THE NORTHWEST OF THE TERMINALS. ALL IN ALL...VERY
POOR FLYING CONDITIONS OVER CENTRAL INDIANA ON FRIDAY.
LAST ISSUE FOCUSES ON LOW LEVEL WIND SHEAR WHICH WILL BECOME A
FACTOR ONCE AGAIN THIS EVENING WITH THE ARRIVAL OF THE LOW LEVEL
JET. RAP INDICATING POTENTIAL FOR SOUTHWEST WINDS TO APPROACH
60KTS OVERNIGHT IN THE 2-3KFT LAYER. LLWS WILL BE A CONCERN FOR
AVIATORS WELL INTO FRIDAY AS THE LOW LEVEL JET DOES NOT WEAKEN
UNTIL THE PASSAGE OF THE SURFACE WAVE DURING THE AFTERNOON.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH FROM LATE FRIDAY NIGHT THROUGH SUNDAY MORNING FOR
INZ021-028>031-035>049-051>057-060>065-067>072.
&&
$$
SYNOPSIS...TUCEK
NEAR TERM...TUCEK
SHORT TERM...TUCEK
LONG TERM...NIELD
AVIATION...RYAN
VISIT US AT HTTP://WWW.WEATHER.GOV/IND
FOLLOW US ON TWITTER AND YOUTUBE AT:
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AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
802 PM CST THU DEC 19 2013
.UPDATE...
ISSUED AT 802 PM CST THU DEC 19 2013
BASED ON CURRENT TRENDS...HAVE MOVED UP THE ONSET OF THE FREEZING
RAIN ADVISORY FOR THE EASTERN SEGMENT THAT WAS PREVIOUSLY SET TO
BEGIN AT MIDNIGHT...TO 10 PM. ALSO...ADDED FAR NORTHWEST ILLINOIS
COUNTIES TO THE CURRENT ADVISORY AREA.
AT 745 PM...KDVN RADAR SHOWED WIDESPREAD LIGHT RAIN ACROSS THE CENTRAL
AND NORTHERN PORTIONS OF THE FORECAST AREA WITH WIDESPREAD
DRIZZLE THE ENTIRE AREA NORTH OF HIGHWAY 34. THE FREEZING LINE AT
THE SURFACE WAS ROUGHLY ALONG A LINE FROM WESTERN STEPHENSON COUNTY
IL...TO CEDAR RAPIDS AND SOUTHWEST TO NEAR PELLA. SURFACE
OBSERVATIONS WERE INDEED REPORTING FREEZING RAIN NW OF THIS LINE.
USED RAP MODEL TRENDS TO TRANSITION THE 32 DEGREE LINE AND
FREEZING PRECIP AREA SOUTHEAST THIS EVENING AND OVERNIGHT.
THE PRECIPITATION SHOULD CONTINUE UNTIL THE WAVE OF LOW PRESSURE
STILL OUT OVER THE OK PANHANDLE PASSES TO OUR SOUTHEAST THROUGH
CENTRAL IL FRIDAY AFTERNOON. WITH THIS TIMING...THE PRECIPITATION
SHOULD CONTINUE THROUGH MOST OF FRIDAY MORNING...WHEN LOW LEVEL
COLD ADVECTION SHOULD CHANGE THE PRECIPITATION OVER TO LIGHT SNOW
AND POSSIBLY SLEET ACROSS THE NORTHWEST.
&&
.SYNOPSIS...
ISSUED AT 330 PM CST THU DEC 19 2013
A FRONTAL BOUNDARY REMAINS DRAPED ACROSS THE AREA THIS AFTERNOON...
ROUGHLY ALONG INTERSTATE 80. MOISTURE IS POOLING ALONG AND SOUTH
OF THE FRONT...EVIDENT BY DEW POINTS THAT HAVE CLIMBED INTO THE
30S AND EVEN LOWER 40S. TO THE NORTH...DEW POINTS ARE IN THE MID
AND UPPER 20S. FOG NEVER DID FORM TODAY...WITH VISIBILITIES GENERALLY
REMAINING OVER 6 MILES...WITH ONLY A FEW SITES DROPPING TO 4-6SM
FOR ONLY AN HOUR OR TWO. HIGH LEVEL CLOUDS BLANKET THE AREA...WITH
SOME LOW LEVEL STRATUS JUST NOW OVER THE PAST HOUR/TWO FORMING
OVER AREAS SOUTH OF I 80. AS OF 3 PM...TEMPERATURES RANGE FROM THE
LOWER 30S ALONG HIGHWAY 20...TO THE UPPER 40S AND LOWER 50S IN
NORTHEAST MO.
&&
.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 330 PM CST THU DEC 19 2013
GENERAL SHORT TERM FORECAST HAS NOT CHANGED MUCH...OTHER THAN
WITH ABOUT A 6 HOUR DELAY. STILL EXPECT LIGHT RAIN AND FREEZING
RAIN TO DEVELOP ACROSS THE AREA THIS EVENING AND ESPECIALLY
OVERNIGHT. NO CHANGE TO GOING FREEZING RAIN ADVISORY AREAL
COVERAGE...HOWEVER WE HAVE EXTENDED IT UNTIL MID MORNING FRIDAY.
DO NOT EXPECT THAT MUCH RAINFALL WITH THIS EVENT...WITH MOST AREAS
SEEING A FEW HUNDREDTHS OF AN INCH TO UNDER A TENTH. MINOR ICE
ACCUMULATIONS OR A LIGHT GLAZE WILL STILL BE POSSIBLE ON UNTREATED
SURFACES LATE TONIGHT THROUGH THE MORNING COMMUTE FRIDAY FOR AREAS
IN THE ADVISORY. SEE THE LATEST WINTER WEATHER MESSAGE FOR MORE
INFORMATION. LOWS TONIGHT WILL RANGE FROM AROUND 20 IN THE NW
CWFA...TO THE MID 30S IN PARTS OF WEST CENTRAL IL.
ONLY A SLIGHT RISE IN TEMPS IS EXPECTED FRIDAY...AS THE WINTRY
MIX OF -RA/-FZRA/-SN SLOWLY EXITS TO THE EAST AND NORTH WINDS
USHER COLD AIR INTO THE AREA. THE NW 1/3 OF THE AREA MAY SEE THE
PCPN CHANGE TO ALL SNOW BEFORE ENDING DURING THE DAY FRIDAY WITH
ONLY A DUSTING OF ACCUMULATION POSSIBLE.
.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 330 PM CST THU DEC 19 2013
A WINTER STORM WILL IMPACT THE CWA SATURDAY NIGHT AND SUNDAY. FOR
THIS POTENTIAL...WHICH IS COMPLICATED IN MANY WAYS...A WINTER
STORM WATCH HAS BEEN ISSUED FOR ALL COUNTIES FROM 00Z SUN TO 00Z
MONDAY.
UPPER AIR OBSERVATIONS CONFIRM A STRONG UPPER LOW IS DIGGING
SOUTHEAST THROUGH CALIFORNIA TODAY...AND WILL BE KICKED OUT OF THE
BASE OF THE TROF BY A STRONG 150KT JET STREAK OBSERVED AT 300MB.
THIS WILL SET THE STAGE FOR CYCLOGENESIS ALONG THE FRONTAL BOUNDARY
WHICH WILL BE STALLED TO OUR SOUTH FRIDAY NIGHT. GUIDANCE IS IN
FAIRLY GOOD AGREEMENT THAT THE SURFACE LOW WILL PASS FROM NEAR
SOUTHWEST MO SATURDAY AFTERNOON...TO NORTHERN INDIANA BY SUNDAY
MORNING. THE UPPER LOW SHOULD EJECT NORTHEAST...WITH MODELS AGREEING
A TRACK THROUGH THE CWA AS A PARTIALLY CLOSED OFF 500MB LOW OCCURRING
ABOUT 12Z SUNDAY. THIS SYNOPTICALLY SETS THE STAGE FOR A SIGNIFICANT
WINTER STORM FOR OUR CWA AND MUCH OF THE MIDWEST. HEAVY RAINS WILL
TAKE PLACE A BIT FARTHER SOUTHEAST...FROM FRIDAY THROUGH SUNDAY.
THERMALLY...MODELS ARE A BIT COLDER THAN LAST NIGHTS RUNS...AND I
HAVE ADJUSTED THE SLEET/ZR TRANSITION TO SNOW A BIT FARTHER EAST.
HOWEVER...IT MAY BE SEEN THAT A SIGNIFICANT AMOUNT OF QPF FOR THIS
EVENT FALLS AS SLEET AND POSSIBLE RA/ZR IN THE SOUTHEAST AND FAR
EAST. WEST OF A LINE FROM BURLINGTON TO STERLING ILLINOIS...THIS
EVENT SHOULD BE DOMINATED BY SNOW SATURDAY NIGHT AND SUNDAY.
THUS...AMOUNTS WILL SEE A STEEP GRADIENT FROM 6-8 INCHES WIDESPREAD
IN THE IOWA AND FAR WESTERN IL COUNTIES...TO UNDER 4 INCHES IN THE
EAST. THOUGH AMOUNTS SHOULD BE UNDER 6 INCHES IN THE EAST AND
SOUTHEAST...IT DOES APPEAR THAT SLEET AND FREEZING RAIN MAY BE
ENOUGH OF A THREAT TO WARRANT A WATCH INCLUSION. BLOWING SNOW IN
OPEN AREAS...AND WIDESPREAD SIGNIFICANT DRIFTING SHOULD CONTINUE
THROUGH SUNDAY AFTERNOON...AND THE WATCH WILL BE CONTINUED THROUGH
6PM FOR THIS REASON.
BEYOND THIS...TEMPERATURES CONTINUE TO BE COOLED IN THIS GUIDANCE
BLEND FORECAST OF THE EXTENDED. WE WILL CERTAINLY KEEP WHAT SNOW
COVER IS ON THE GROUND SUNDAY AFTERNOON THROUGH DECEMBER 25. YOU
GUESSED IT...ITS GOING TO BE A WHITE CHRISTMAS IN MUCH OF THE UPPER
MIDWEST.
ERVIN
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 538 PM CST THU DEC 19 2013
VFR CONDITIONS WILL DETERIORATE TO IFR AND POSSIBLY LIFR AS A CIGS
LOWER AND DRIZZLE DEVELOPS OVER THE AREA TONIGHT. THIS DRIZZLE IS
EXPECTED TO GRADUALLY CHANGE OVER TO LIGHT FREEZING DRIZZLE AS
TEMPERATURES DROP BELOW FREEZING. THIS MAY RESULT IN A LIGHT
GLAZING ON RUNWAY SURFACES...MAINLY AT CID...MLI AND DBQ. LOW
CLOUDS...FOG AND PATCHY FREEZING DRIZZLE WILL LINGER INTO FRIDAY
MORNING WITH PREVAILING IFR CONDITIONS. THE PRECIPITATION WILL
LIKELY CHANGE OVER TO SNOW BEFORE ENDING LATE FRIDAY AFTERNOON.
WHILE SOME IMPROVEMENT IS EXPECTED BY LATE FRIDAY AFTERNOON...THE
FINAL 6 HOUR PERIOD OF THE TAFS ARE TRENDED ON THE PESSIMISTIC
SIDE FOR PRODUCT BREVITY.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR BENTON-BUCHANAN-
DELAWARE-DUBUQUE-IOWA-JACKSON-JOHNSON-JONES-KEOKUK-LINN.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-DES
MOINES-DUBUQUE-HENRY IA-IOWA-JACKSON-JEFFERSON-JOHNSON-
JONES-KEOKUK-LEE-LINN-LOUISA-MUSCATINE-SCOTT-VAN BUREN-
WASHINGTON.
FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR CEDAR-CLINTON-
DES MOINES-HENRY IA-JEFFERSON-LOUISA-MUSCATINE-SCOTT-VAN
BUREN-WASHINGTON.
IL...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR CARROLL-JO
DAVIESS-STEPHENSON.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR BUREAU-CARROLL-HANCOCK-HENDERSON-HENRY IL-JO
DAVIESS-MCDONOUGH-MERCER-PUTNAM-ROCK ISLAND-STEPHENSON-
WARREN-WHITESIDE.
FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR MERCER-ROCK
ISLAND-WHITESIDE.
MO...WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR CLARK-SCOTLAND.
FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR SCOTLAND.
&&
$$
UPDATE...SHEETS
SYNOPSIS...14
SHORT TERM...14
LONG TERM...ERVIN
AVIATION...SHEETS
AREA FORECAST DISCUSSION
NWS GOODLAND KS
236 PM MST WED DEC 18 2013
.SHORT TERM...(THIS AFTERNOON THROUGH THURSDAY)
ISSUED AT 100 PM MST WED DEC 18 2013
LATEST WV IMAGERY AND RAP H5 ANALYSIS INDICATES WESTERLY ZONAL FLOW
IN PLACE ACROSS THE UNITED STATES...WITH TWO SHORTWAVE TROUGHS
UPSTREAM OFF THE WEST COAST. THE FIRST TROUGH IS CENTERED OVER
BRITISH COLUMBIA...WITH THE SECOND JUST WEST OF THE BAJA PENINSULA.
AT THE SURFACE A TROUGH OF LOW PRESSURE EXTENDS FROM EASTERN
COLORADO AND ACROSS SOUTH WEST NEBRASKA. A COLD FRONT IS IN PLACE
ACROSS CENTRAL MONTANA AND NORTH DAKOTA WITH AN ARCTIC HIGH PRESSURE
SYSTEM LURKING TO THE NORTH OF THE FEATURE READY TO MAKE A TREK
SOUTH INTO THE PLAINS.
WITH WESTERLY CROSS MOUNTAIN FLOW AND EMBEDDED UPPER LEVEL ENERGY
CONTINUE TO MOVE EAST I WOULD EXPECT CLOUD COVER TO BEGIN TO
INCREASE ONCE AGAIN TONIGHT...ESPECIALLY AFTER MIDNIGHT AS A TROUGH
BEGINS TO MOVE FROM THE PAC NW AND DEEPEN ACROSS THE GREAT BASIN.
CLOUD COVER COULD HAVE A NEGATIVE IMPACT ON RADIATIONAL COOLING...AND
I WAS NOT CONFIDENT IN HOW LOW WE WILL ACTUALLY DROP BEFORE WINDS
POSSIBLY INCREASE TOWARDS DAYBREAK THURSDAY. I HAVE TRENDED TEMPS UP
A LITTLE.
TEMPERATURE FORECAST THURSDAY IS COMPLICATED BY TIMING OF ARCTIC
FRONT ARRIVAL. NAM/GFS CONTINUE TO SHOW FROPA IN THE 12-18Z TIME
PERIOD...WITH THE LATEST RUNS OF THE ECMWF/GEM SEEM TO FAVOR AN
AFTERNOON FRONTAL PASSAGE. CONTINUITY AND PERSONAL EXPERIENCE WOULD
FAVOR THE QUICKER PASSAGE...HOWEVER WITH ABOUT 6HR OF SPREAD IN
SOLUTIONS THIS COULD HAVE A LARGE IMPACT ON HIGH TEMPS. GOING BY THE
COLDER END OF GUIDANCE NORTHERN HALF OF THE CWA LIKELY WOULDNT MAKE
IT ABOVE FREEZING AND TEMPS WOULD BE FALLING TO THE 20S BY MID
AFTERNOON. WARMER END OF GUIDANCE ALLOWS ENOUGH OF A WINDOW FOR
TEMPS TO RISE TO AT LEAST THE UPPER 40S IF NOT THE LOW 50S ACROSS
THE SOUTH. I NUDGED THE FORECAST TOWARDS THE FASTER
GUIDANCE...HOWEVER CONFIDENCE IS NOT PARTICULARLY HIGH ON HOW THIS
WILL TIME OUT. WE COULD END UP SEEING HIGHS IN THE NORTH OCCURRING
IN THE EARLY MORNING NEAR SUNRISE.
GUIDANCE CONTINUES TO SHOW INCREASING MID LEVEL MOISTURE AND WEAK
FORCING FROM THE NORTHWEST...SO I COULDNT RULE OUT A FEW FLURRIES
BY LATE THURSDAY AFTERNOON. I LEFT MENTION IN PLACE OVER YUMA
COUNTY IN LINE WITH PREVIOUS FORECAST.
.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 234 PM MST WED DEC 18 2013
WESTERLY FLOW WILL CONTINUE THROUGH FRIDAY AHEAD OF A TROUGH MOVING
SOUTHEAST FROM SOUTHERN CALIFORNIA. THE TROUGH WILL MOVE EAST INTO
EASTERN NEW MEXICO SATURDAY. SURFACE HIGH PRESSURE WILL MOVE INTO
THE CENTRAL PLAINS THURSDAY NIGHT AND FRIDAY. A SURFACE TROUGH WILL
MOVE INTO EASTERN COLORADO FRIDAY NIGHT. THIS TROUGH WILL MOVE SOUTH
INTO TEXAS SATURDAY WITH A COLD FRONT FOLLOWING.
THERE WILL BE SOME FLURRIES POSSIBLE THURSDAY NIGHT AS COLDER AIR
FILTERS INTO THE REGION BEHIND THE COLD FRONT. PLAN TO CONTINUE THIS
AREA OF FLURRIES OVER THE NORTHWEST FA WHERE H8-7 LAYER MEAN
MOISTURE IS BEST. OTHERWISE POPS WILL BE NIL THROUGH FRIDAY NIGHT
DUE TO SUBSIDENCE. THE UPPER TROUGH OVER EASTERN NEW MEXICO WILL
BRING A SLIGHT CHANCE OF LIGHT SNOW TO THE FAR SOUTHEAST ZONES
SATURDAY AS DYNAMICS MOVE ACROSS SOUTHWEST AND SOUTHCENTRAL KANSAS.
MIN TEMPERATURES THURSDAY NIGHT WILL FALL INTO THE LOWER TEENS AND
COULD BE COLDER IF SKIES CLEAR. THE COLDEST AIR MOVES AWAY SO THAT
LOW TEMPERATURES FRIDAY NIGHT WILL BE IN THE UPPER TEENS. MAX
TEMPERATURES WILL RANGE FROM 30 TO AROUND 35 FRIDAY AND 35 TO AROUND
40 SATURDAY.
IN THE EXTENDED...(SATURDAY NIGHT THROUGH WEDNESDAY)...
SOME LIGHT SNOW WILL BE POSSIBLE SATURDAY NIGHT AS THE ABOVE
MENTIONED TROUGH MOVES EAST ACROSS THE CENTRAL/SOUTHERN PLAINS.
SLIGHT CHANCE POPS WILL BE OVER THE EXTREME SOUTHEAST FA WHERE
MOISTURE IS BEST. UPPER FLOW WILL BECOME NORTHWEST SUNDAY AND CONTINUE
THROUGH WEDNESDAY. SUBSIDENCE DURING THIS TIME WILL BRING DRY
CONDITIONS.
MIN TEMPERATURES WILL RANGE FROM THE TEENS SATURDAY THROUGH SUNDAY
NIGHTS WARMING TO THE LOWER 20S MONDAY THROUGH WEDNESDAY NIGHTS.
MAX TEMPERATURES SUNDAY WILL BE IN THE LOWER 30S. SOME WARMING INTO
THE 40S WILL OCCUR MONDAY THROUGH WEDNESDAY.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1022 AM MST WED DEC 18 2013
VFR CONDITIONS WILL PREVAIL AT BOTH KGLD AND KMCK TERMINALS. WEST
WINDS GENERALLY BELOW 12KTS WILL BECOME LIGHT AND VARIABLE AROUND
00Z AS DAYTIME HEATING ENDS AND A SURFACE TROUGH SHIFTS EAST.
WINDS WILL THEN SHIFT TO THE NORTH AND INCREASE TO 10-12KT RANGE
LATE TONIGHT AS A FRONT APPROACHES THE REGION.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...DR
LONG TERM...FS
AVIATION...DR
AREA FORECAST DISCUSSION
NWS GOODLAND KS
102 PM MST WED DEC 18 2013
.SHORT TERM...(THIS AFTERNOON THROUGH THURSDAY)
ISSUED AT 100 PM MST WED DEC 18 2013
LATEST WV IMAGERY AND RAP H5 ANALYSIS INDICATES WESTERLY ZONAL FLOW
IN PLACE ACROSS THE UNITED STATES...WITH TWO SHORTWAVE TROUGHS
UPSTREAM OFF THE WEST COAST. THE FIRST TROUGH IS CENTERED OVER
BRITISH COLUMBIA...WITH THE SECOND JUST WEST OF THE BAJA PENINSULA.
AT THE SURFACE A TROUGH OF LOW PRESSURE EXTENDS FROM EASTERN
COLORADO AND ACROSS SOUTH WEST NEBRASKA. A COLD FRONT IS IN PLACE
ACROSS CENTRAL MONTANA AND NORTH DAKOTA WITH AN ARCTIC HIGH PRESSURE
SYSTEM LURKING TO THE NORTH OF THE FEATURE READY TO MAKE A TREK
SOUTH INTO THE PLAINS.
WITH WESTERLY CROSS MOUNTAIN FLOW AND EMBEDDED UPPER LEVEL ENERGY
CONTINUE TO MOVE EAST I WOULD EXPECT CLOUD COVER TO BEGIN TO
INCREASE ONCE AGAIN TONIGHT...ESPECIALLY AFTER MIDNIGHT AS A TROUGH
BEGINS TO MOVE FROM THE PAC NW AND DEEPEN ACROSS THE GREAT BASIN.
CLOUD COVER COULD HAVE A NEGATIVE IMPACT ON RADIATIONAL COOLING...AND
I WAS NOT CONFIDENT IN HOW LOW WE WILL ACTUALLY DROP BEFORE WINDS
POSSIBLY INCREASE TOWARDS DAYBREAK THURSDAY. I HAVE TRENDED TEMPS UP
A LITTLE.
TEMPERATURE FORECAST THURSDAY IS COMPLICATED BY TIMING OF ARCTIC
FRONT ARRIVAL. NAM/GFS CONTINUE TO SHOW FROPA IN THE 12-18Z TIME
PERIOD...WITH THE LATEST RUNS OF THE ECMWF/GEM SEEM TO FAVOR AN
AFTERNOON FRONTAL PASSAGE. CONTINUITY AND PERSONAL EXPERIENCE WOULD
FAVOR THE QUICKER PASSAGE...HOWEVER WITH ABOUT 6HR OF SPREAD IN
SOLUTIONS THIS COULD HAVE A LARGE IMPACT ON HIGH TEMPS. GOING BY THE
COLDER END OF GUIDANCE NORTHERN HALF OF THE CWA LIKELY WOULDNT MAKE
IT ABOVE FREEZING AND TEMPS WOULD BE FALLING TO THE 20S BY MID
AFTERNOON. WARMER END OF GUIDANCE ALLOWS ENOUGH OF A WINDOW FOR
TEMPS TO RISE TO AT LEAST THE UPPER 40S IF NOT THE LOW 50S ACROSS
THE SOUTH. I NUDGED THE FORECAST TOWARDS THE FASTER
GUIDANCE...HOWEVER CONFIDENCE IS NOT PARTICULARLY HIGH ON HOW THIS
WILL TIME OUT. WE COULD END UP SEEING HIGHS IN THE NORTH OCCURRING
IN THE EARLY MORNING NEAR SUNRISE.
GUIDANCE CONTINUES TO SHOW INCREASING MID LEVEL MOISTURE AND WEAK
FORCING FROM THE NORTHWEST...SO I COULDNT RULE OUT A FEW FLURRIES
BY LATE THURSDAY AFTERNOON. I LEFT MENTION IN PLACE OVER YUMA
COUNTY IN LINE WITH PREVIOUS FORECAST.
.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 1208 AM MST WED DEC 18 2013
SHORTWAVE TROUGH AXIS WILL BE MOVING THROUGH THE PLAINS ON SATURDAY.
BEST DYNAMICS WILL BE IN THE SOUTHERN PLAINS BUT THERE WILL BE LOW
CHANCES FOR LIGHT SNOW ACROSS THE SOUTHEASTERN FORECAST AREA.
SHORTWAVE RIDGING WILL FOLLOW FOR SUNDAY AND MONDAY WITH DRY
CONDITIONS AND BELOW NORMAL TEMPERATURES ON SUNDAY REBOUNDING
QUICKLY TO ABOVE NORMAL ON MONDAY. NEXT SYSTEM WILL BE MOVING OUT
OF THE NORTHERN ROCKIES MIDWEEK...BRINGING ANOTHER SHOT OF
SLIGHTLY COLDER AIR ON WEDNESDAY. ALTHOUGH MODELS ARE IN POOR
AGREEMENT ON EVOLUTION OF THIS SYSTEM AS IT DIGS INTO THE
PLAINS...PRECIPITATION CHANCES APPEAR SLIM TO NONE.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1022 AM MST WED DEC 18 2013
VFR CONDITIONS WILL PREVAIL AT BOTH KGLD AND KMCK TERMINALS. WEST
WINDS GENERALLY BELOW 12KTS WILL BECOME LIGHT AND VARIABLE AROUND
00Z AS DAYTIME HEATING ENDS AND A SURFACE TROUGH SHIFTS EAST.
WINDS WILL THEN SHIFT TO THE NORTH AND INCREASE TO 10-12KT RANGE
LATE TONIGHT AS A FRONT APPROACHES THE REGION.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...DR
LONG TERM...024
AVIATION...DR
AREA FORECAST DISCUSSION...UPDATED
NWS JACKSON KY
144 AM EST WED DEC 18 2013
.UPDATE...
ISSUED AT 135 AM EST WED DEC 18 2013
HOURLY GRIDS WERE FRESHENED UP FOR RECENT TRENDS IN HOURLY
TEMPS...DEWPOINTS AND WINDS. BREAKS WORKING ACROSS THE AREA FROM THE
WEST AND HOLES IN THE LOW CLOUDS WILL LEAD TO VALLEY TEMPS...EVEN IN
THE EAST THAT HAVE LEVELED OFF DROPPING AGAIN TOWARD DAWN.
UPDATE ISSUED AT 1025 PM EST TUE DEC 17 2013
DID A QUICK UPDATE TO ADD SOME LOW CLOUDS INTO THE NORTHERN PARTS OF
THE CWA AS THAT LAST WAVE PASSES BY TO THE NORTHEAST OVERNIGHT. DID
ALSO UPDATE THE AVIATION GRIDS TO REFLECT THESE MVFR CIGS. FINE TUNED
OVERNIGHT LOWS IN LIGHT OF THE COLD TO NEUTRAL ADVECTION OVERNIGHT
AND NORTHERN CLOUDS. THESE UPDATES HAVE BEEN SENT TO THE NDFD AND WEB
SERVERS.
UPDATE ISSUED AT 650 PM EST TUE DEC 17 2013
23Z SFC ANALYSIS SHOWS A DEPARTING AREA OF LOW PRESSURE...WITH A
TIGHT AND COMPACT PRESSURE GRADIENT...EXITING KENTUCKY. THIS IS
TAKING A BATCH OF LIGHT RAIN...AND SNOW ON THE NORTHERN FRINGE...
EAST AND OUT OF THE AREA...AS WELL. THE LATEST HIGH RESOLUTION MODELS
SUPPORT THIS TREND WITH THE HRRR AND RUC13 ESSENTIALLY DRY THROUGH
THE REST OF THE NIGHT. HIGH PRESSURE BUILDING INTO EAST KENTUCKY WILL
CLEAR MOST OF THE CLOUDS OUT OF THE SKY LEAVING BEHIND JUST A
SMATTERING OF MID LEVELS ONES THAT COULD PRODUCE A FEW FLURRIES
THROUGH THE REST OF THE EVENING. OTHERWISE...IT WILL BE DRIER AND
COLDER OVERNIGHT WITH TEMPERATURES FALLING INTO THE MID 20S BY EARLY
WEDNESDAY MORNING. HAVE UPDATED THE GRIDS TO REFLECT THIS MAKING
CHANGES PRIMARILY TO THE POPS AND WX ONES AND T/TD TO A LESSER
EXTENT. THESE HAVE BEEN SENT TO THE NDFD AND WEB SERVERS. UPDATES TO
THE ZFP AND HWO WILL BE ISSUED SHORTLY...ONCE THE MEASURABLE PCPN
CLEARS THE CWA WITHIN THE HOUR.
&&
.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 331 PM EST TUE DEC 17 2013
MODELS HAVE BEEN CHANGING THROUGHOUT THE LAST 24 HOURS...MAKING IT
HARD TO PINPOINT AN EXACT FORECAST UNTIL LOOKING AT ONGOING
CONDITIONS. SO FAR TODAY...THE HRRR SEEMS TO BE INITIALIZING THE
BEST WITH ONGOING CONDITIONS...AND THE OTHER HIRES MODELS HAVE
FOLLOWED SUIT THROUGHOUT THE DAY. BASED ON CURRENT TRENDS...AND
LATEST HIRES MODEL DATA...FAVOR A LESS IMPACTFUL EVENING WITH MAINLY
LIGHT RAIN...ENDING BEFORE MIDNIGHT IN MOST AREAS.
WITH TEMPERATURES WELL ABOVE FREEZING IN MOST LOCATIONS RIGHT
NOW...AND ROAD TEMPS SITTING ABOVE FREEZING AS WELL...DO NOT EXPECT
ANY IMPACTS OTHER THAN SOME LIGHT RAIN...MAINLY NORTH OF THE
MOUNTAIN PARKWAY. CLOUD COVER CURRENTLY EXTENDS SOUTHWARD ACROSS
MUCH OF THE CWA. AS PRECIPITATION QUICKLY MOVES OFF TO THE
EAST...TEMPERATURES WILL COOL WITH LOSS OF DAYTIME HEATING...BUT
LATEST DATA SUPPORTS THE IDEA THAT TEMPS WILL STILL BE ABOVE
FREEZING THROUGH MOST OF THE EVENING. ANY SNOW THAT DOES FALL WILL
BE LATE IN THE EVENING ACROSS THE FAR EASTERN CWA /PIKE COUNTY/...AS
WELL AS ACROSS SOME OF THE HIGHEST TERRAIN NEAR THE VIRGINIA BORDER.
DROPPED SNOW TOTALS SUBSTANTIALLY...WITH ONLY A COUPLE TENTHS
EXPECTED IN THE HIGHEST TERRAIN. NEIGHBORING OFFICES SEEM TO HAVE
FOLLOWED SUIT WITH THIS LOWER IMPACT SOLUTION AS WELL.
THE PRECIPITATION SHOULD CLEAR EARLY IN THE NIGHT...WITH DRY AND
COLDER AIR FILTERING IN BEHIND...EFFECTIVELY CUTTING OFF THE CLOUD
COVER FROM WEST TO EAST. AS THIS COLDER AIRMASS TAKES HOLD...AND
CLOUDS CLEAR...EXPECT TEMPS TO MIX OUT OVERNIGHT INTO THE MID 20S
ACROSS MUCH OF THE REGION. SUNNY SKIES WILL FINALLY MAKE AN
APPEARANCE DURING THE DAY TOMORROW AS HIGH PRESSURE REMAINS IN
CONTROL. TEMPERATURES WILL BE ON THE COOLER SIDE COMPARED TO
TODAY...BUT WILL STILL BE ABLE TO WARM UP TO ABOUT THE 40 DEGREE
MARK. NAM12 FORECAST SOUNDINGS SHOW THE ATMOSPHERE BECOMING QUITE
DRY...WITH DEW POINTS DROPPING SUBSTANTIALLY. THIS WILL ESPECIALLY
BE THE CASE IN THE HIGHER TERRAIN WEDNESDAY NIGHT...WHERE DEW POINTS
COULD DROP AS LOW AS 9 DEGREES. OVERNIGHT LOW TEMPS WILL DROP TO
AROUND FREEZING OR SLIGHTLY BELOW...WITH A GOOD SET UP FOR A RIDGE
VALLEY SPLIT TO OCCUR.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 341 PM EST TUE DEC 17 2013
THE EXTENDED FORECAST PERIOD BEGINS ON THURSDAY WITH A MAINLY
ZONAL PATTERN OVER THE CONUS WITH AN UPPER LEVEL LOW OVER THE
SOUTHWEST. THE BIG QUESTION BECOMES THE TIMING OF THE UPPER LOW AS
IT MOVES TO THE EAST AND WHERE THE FRONT SETS UP OVER THE OHIO
VALLEY. THE CURRENT TREND IN THE MODELS IS FOR A STRONGER LOW TO
FORM ON THE FRONT TO THE WEST OF THE AREA. THIS SOLUTION WILL
CREATE A SHARP WAVE ON THE FRONT AND PUSH A WARM FRONT TO THE NORTH
OF THE AREA. THIS SOLUTION WOULD PRODUCE MUCH LESS RAINFALL BECAUSE
THE STATIONARY FRONT WOULD STAY TO THE WEST AND NORTH OF EASTERN
KENTUCKY. THE JURY IS REALLY STILL OUT ON THIS SOLUTION AND WOULD
NOT BE TOO SURPRISED TO SEE A COUPLE DIFFERENT SOLUTIONS BEFORE THE
WEEKEND GETS HERE. AS SUCH...TIMING OF THE SYSTEM AND THE AMOUNT OF
RAINFALL IS FAIRLY LOW CONFIDENCE. IN ADDITION...HAVE SEEN THE
MODELS STRUGGLE TIME AND TIME AGAIN WITH TRYING TO NAIL DOWN
TRANSITIONS IN THE PATTERN LIKE THE ONE WE ARE SEEING. DID TREND THE
FORECAST TO THE NEWER MODEL BLEND. ALSO WITH THIS SOLUTION...THERE
WILL NOT BE MUCH TIME TO GET ANY COLD AIR INTO THE AREA AS THE FRONT
MOVES THROUGH. THIS WILL DECREASE THE CHANCES FOR WINTRY
PRECIPITATION ON THE BACK END OF THE FRONT.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY)
ISSUED AT 139 AM EST WED DEC 18 2013
THE SOLID BAND OF STRATOCU AND ASSOCIATED MVFR CIGS IS QUICKLY
WORKING EAST ACROSS THE AREA WITH ANOTHER NARROW BAND OF MVFR
STRATOCU BEHIND IT. CONDITIONS SHOULD BECOME VFR IN ALL AREAS THROUGH
9Z OR 10Z AND REMAIN VFR THROUGH THE END OF THE PERIOD AS SFC AND
UPPER LEVEL HIGH PRESSURE BUILD IN. THE PRESSURE GRADIENT WILL ALSO
RELAX OVER THE NEXT SEVERAL HOURS...WITH VALLEY LOCATIONS GRADUALLY
BECOMING LIGHT AND VARIABLE AND MORE OPEN TERRAIN LOCATIONS AND
RIDGES TAPERING TO AROUND 5 KT...AND LOSING RECENT GUSTINESS.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JP
SHORT TERM...JMW
LONG TERM...JJ
AVIATION...GREIF
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1234 AM EST WED DEC 18 2013
.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 343 PM EST TUE DEC 17 2013
NOTE THAT TEMPS AT CMX REMAIN QUESTIONABLE DUE TO FAULTY FAN ON
OBSERVATION EQUIPMENT. TECHNICIANS WL BE WORKING ON THIS PROBLEM
TMRW.
12Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW PERSISTENT NW FLOW
ALF BTWN DEEP UPR TROF CENTERED OVER ONTARIO AND UPR RDG OVER WRN
NAMERICA. H5 TEMPS WITHIN THE TROF EXTENDING INTO THE GREAT LKS ARE
AS LO AS -40C...SO THE AREA REMAINS IN THE GRIP OF WINTER CHILL. ONE
SHRTWV EMBEDDED WITHIN THE UPR TROF BROUGHT SOME -SN TO THE SCNTRL
CWA THIS MRNG...BUT THIS DISTURBANCE/DEEPER MSTR SHOWN ON THE 12Z
GRB RAOB HAVE SHIFTED TO THE E. ANOTHER SHRTWV IS PRESENT OVER MN...
BUT THIS DISTURBANCE WL BE PASSING TOO FAR TO THE S TO HAVE AN
IMPACT ON UPR MI. YET ANOTHER SHRTWV IS OVER NW ONTARIO AND DROPPING
SEWD. ATTENDANT SFC-H85 COLD FNT MOVED INTO WRN UPR MI THIS AFTN.
12Z INL/YPL RAOBS SHOW HI RELATIVE RH TO H6-5 AND 12Z H85 TEMPS
RANGING FM -13C AT INL RIGHT BEHIND THE COLD FNT TO -24C AT YPL...
WHICH WAS DEEPER INTO THE COLD AIRMASS. SO THERE ARE POCKETS OF SHSN
EXTENDING UPWIND OF LK SUP IN NRN MN/ADJOINING ONTARIO. FARTHER TO
THE W...THERE ARE SIGNS THE FLOW IS BECOMING A BIT MORE
PROGRESSIVE...AT LEAST FOR A SHORT TIME. 00Z-12Z H3 HGT RISES UP TO
150M WERE REPORTED AT SEVERAL UPR AIR SITES FM THE NRN PLAINS INTO
SCNTRL CANADA AS THE WRN RDG SHIFTS TO THE E.
MAIN FCST CONCERNS IN THE SHORT TERM FOCUS ON LES POPS/AMOUNTS WITH
ARRIVAL OF MORE ARCTIC AIR BEHIND EARLY AFTN/EARLY EVNG COLD FROPA.
TNGT...SHRTWV IN NW ONTARIO IS FCST TO SHIFT SEWD ACRS NRN LK SUP...
ACCOMPANIED BY AREA OF WEAK H85-5 QVECTOR CNVGC/SOME DEEPER MSTR AND
ATTENDANT COLD FROPA. EXPECT SHSN INTENSITY/COVERAGE TO INCRS LATE
THIS AFTN/EVNG W-E...ESPECIALLY IN AREAS NEAR LK SUP FAVORED BY THE
WNW FLOW IN THE WAKE OF THE COLD FROPA...WHICH WL BE FOLLOWED BY
AXIS OF H85 TEMPS AS LO AS -20C. ALTHOUGH NOT OUT OF THE QUESTION
THERE COULD BE SOME HEAVIER SHSN IN THE FAVORED SN BELTS...ADVY SN
SEEMS UNLIKELY. THE FIRST LIMITING FACTOR WL BE RELATIVELY SHORT
DURATION OF THE HEAVIER LES. HGT RISES NOTED IN THE NRN PLAINS/
SCENTRAL CANADA ARE PROGGED TO FOLLOW QUICKLY THE DEPARTING SHRTWV
LATER IN THE EVNG WITH VIGOUROUS DNVA/DEEP LYR QVECTOR DVGC LOWERING
SUBSIDENCE INVRN TO NEAR 3K FT OVER THE KEWEENAW BY 12Z. APRCH OF
SFC RDG AXIS AND SHIFTING LLVL WINDS OVER THE W UNDER THESE NEGATIVE
DYNAMICS...WITH RDG AXIS ARRIVING THERE BY 12Z...WL ALSO ACT TO
SUPPRESS THE SN AMOUNTS. IN FACT...SUITE OF HIER RES MODEL OUTPUT IS
QUITE VARIABLE ON QPF...WITH FCSTS INCONSISTENT ON MAGNITUDE/HGT/
TIMING OF SHARPER UVV AND RELATIVE TO THE DGZ. IN THE NW WIND SN
BELTS TO THE E OF MQT...SHSN WL ARRIVE DURING THE EVNG AND PERSIST
THRU 12Z. LONGER FETCH OVER THE OPEN WATER WL PLAY AN ENHANCEMENT
ROLE IN INTENSIFYING THE SHSN STREAMING INTO THIS AREA...BUT
SHIFTING WINDS MAY LIMIT THE RESIDENCE TIME OF THE HEAVIER SHSN HERE
AS WELL. THE MOST FAVORABLE FACTOR FOR HEAVIER SN OVER THE ERN CWA
NEAR LK SUP WL BE THE POTENTIAL FOR LAND BREEZE CNVGC OVER FAR
EASTERN ALGER/NRN LUCE COUNTIES. BUT FCST SDNGS SHOW SUBSIDENCE
INVRN SINKING FAIRLY STEADY HERE AS WELL LATER AT NGT WHEN THE
POTENTIAL FOR THE SHARPER LLVL CNVGC WOULD BE GREATER. AS IS
TYPICAL...AREAS OVER THE SCENTRAL WL SEE NOTHING MORE THAN ISOLD
-SHSN WITH DOWNSLOPE FLOW. EXPECT THE LOWEST MIN TEMPS OVER THE
INTERIOR W...WHERE THERE WL BE SOME CLRG/LIGHT WINDS WITH ARRIVAL OF
SFC RDG AXIS.
WED...AS THE UPR FLOW TENDS TO SHIFT MORE ZONAL...A SHRTWV IS FCST
TO SHIFT E THRU SCENTRAL CANADA...WITH ASSOCIATED SFC LO PRES FCST
TO MOVE INTO NRN MN BY 00Z THU. GENERAL WAD/ISENTROPIC LIFT BTWN
THIS SHRTWV/SFC LO AND SFC HI SHIFTING INTO THE SE CONUS WL IMPACT
THE UPR GRT LKS. AS THE FLOW BACKS TO THE SW...LINGERING LES OVER
THE KEWEENAW AND FAR E CWA NEAR LK SUP WL SHIFT OUT INTO THE OPEN
LK. THE BULK OF THE MODELS SHOW LGT SN ASSOCIATED WITH THE SHARPER
ISENTROPIC ASCENT FALLING OVER LK SUP. THE CNDN MODEL IS THE ONE
EXCEPTION...AS THIS MODEL SHOWS THE SFC LO A BIT FARTHER S IN MN AND
STRIPE OF LGT -SN IMPACTING APPROXIMATELY THE NE HALF OF THE CWA.
GIVEN PERSISTENCE OF TROF IN ERN CANADA AND CHILL...SUSPECT THIS
MODEL IS ON THE RIGHT TRACK. SO WL SHIFT THE AXIS OF CHC POPS A BIT
TO THE SW INTO THE NRN LAND CWA. FEED OF RELATIVELY DRY LLVL AIR WL
LIMIT ANY POTENTIAL SN ACCUM EVEN IF THE MORE PESSIMISTIC CNDN MODEL
DOES VERIFY. ALSO LOWERED FCST MAX TEMPS A BIT TO REFLECT THE
POTENTIAL FOR MORE TENACIOUS COLD LLVL AIR.
.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 457 PM EST TUE DEC 17 2013
MUCH OF THIS FCST PERIOD IS IN THE MODERATE TO LOWER CONFIDENCE
RANGE.
AT 00Z THURSDAY MUCH OF THE CONTINENTAL U.S. WILL BE UNDER A BROAD
WEAK RIDGE TO ZONAL FLOW AT 500MB...WITH THE DOMINANT LOW SPINNING
ACROSS N CANADA WITH LONGWAVE TROUGHS EXTENDING ACROSS BOTH THE WEST
AND EAST COASTS.
AN INITIAL BROAD SFC LOW/TROUGH WILL EXTEND NE INTO CENTRAL LAKE
SUPERIOR AT 00Z. WHILE THE GFS PUSHES THE LOW E OF LAKE SUPERIOR BY
06Z THURSDAY...THE ECMWF KEEPS IT AS PART OF THE MAIN SYSTEM TO OUR
S. THE RESULT IS A COMPLETELY DIFFERENT FCST FOR WEDNESDAY
NIGHT...WITH LES OFF THE GFS ON STRONGER NW WINDS...WHILE THE ECMWF
SOLUTION KEEPS A WAA SCHEME OVER THE AREA A BIT LONGER. THEY BOTH DO
AGREE WITH SOME SORT OF LAKE ENHANCEMENT N OR NW FLOW BY THURSDAY
AFTERNOON...ALTHOUGH THE GFS IS APPROX 2C COOLER NEAR THE SFC.
LOOK FOR THE CANADIAN AND W COAST SYSTEMS TO DEEPEN AS THEY SINK SSE
THURSDAY AND FRIDAY. AT 18Z THURSDAY THE MAIN TROUGH WILL EXTEND
FROM THE S LOW OVER S CA UP THROUGH MT INTO S CANADA.
A QUICK BURST OF SNOW THURSDAY NIGHT LOOKS TO BE ABOUT IT...EXCEPT
FOR SOME LAKE EFFECT/LAKE ENHANCEMENT ON W TO NW WINDS OVER THE
KEWEENAW PENINSULA...AND AROUND AND E OF MUNISING THROUGH ABOUT MID
MORNING FRIDAY. TOTAL SNOWFALL OF 1-2IN STILL LOOK GOOD. CONFIDENCE
REMAINS LOW WITH THIS SYSTEM. THE 12Z NAM DID NOT REALLY BRING ANY
OF THE SYNOPTIC MOISTURE INTO UPPER MI...ALTHOUGH THE 18Z VERSION
BROUGHT SNOW BACK NW SIMILARLY TO THE GFS. WILL STILL HIGHLIGHT THE
POTENTIAL FOR A FEW INCHES OF SNOW LATE THURSDAY AFTERNOON INTO
FRIDAY MORNING...MAINLY OVER THE HIGHER TERRAIN NEAR LAKE SUPERIOR.
THE NEXT LOW OVER THE ROCKIES SATURDAY WILL EJECT NE SUNDAY...WITH
UPPER MI AGAIN ON THE BACK SIDE OF THE LOW. GIVEN THE STRENGTH OF
THE SYSTEM...AND SIGNIFICANT HIGH DROPPING IN FROM THE NW SUNDAY
THROUGH MONDAY...MUCH COLDER AIR WILL BE ABLE TO SLIDE IN. 850MB
TEMPS OF -20 TO -22C WILL BE POSSIBLE. THERE ARE SOME TIMING
DIFFERENCES BETWEEN THE GFS AND ECMWF AT THIS PERIOD...BUT THEY ARE
CONSISTENT WITH THE COLD AIR.
FARTHER OUT...EXPECT STRONG WAA TUESDAY BEHIND THE COLD AIRMASS.
WHILE TIMING IS STILL IN QUESTION...SW 40-55KT 850MB WINDS WITH SFC
WINDS OF 15-25KTS LOOK LIKELY FOR A 6HR WINDOW BETWEEN 09Z TUESDAY
TO 00Z WEDNESDAY. WILL NEED TO MONITOR MODEL TRENDS TO ADD MORE
SPECIFICITY AS THE TIME NEARS.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1233 AM EST WED DEC 18 2013
ALL SITES SHOULD SEE GENERAL IMPROVEMENT THROUGH WED MORNING AS
CONDITIONS BECOME LESS FAVORABLE FOR LAKE EFFECT CONDITIONS DUE TO
HIGH PRESSURE MOVING INTO THE REGION. A WEAK LOW PRESSURE SYSTEM
WILL MOVE THROUGH THE AREA TOWARD THE END OF THE TAF PERIOD...SO
INTRODUCED WORSENING CONDITIONS AS LOW LEVEL MOISTURE INCREASES.
&&
.MARINE...(FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)
ISSUED AT 343 PM EST TUE DEC 17 2013
EXPECT NW WINDS TO 25-30 KTS THIS EVENING BEHIND A COLD FRONTAL
PASSAGE TO DIMINISH AND BACK TO THE SW WITH APPROACH OF A HI PRES
RIDGE LATER TONIGHT INTO WED. A VERY CHANGEABLE WEATHER PATTERN WILL
THEN DOMINATE THE UPPER GREAT LAKES THE REST OF THE WEEK...WITH HARD
TO TIME DISTURBANCES IMPACTING LAKE SUPERIOR. CONFIDENCE IS LOW IN
TIMING THESE DISTURBANCES AND ACCOMPANYING WIND SHIFTS...BUT GALES
APPEAR UNLIKELY THRU THE FORECAST PERIOD.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
&&
$$
SHORT TERM...KC
LONG TERM...KF
AVIATION...TITUS
MARINE...KC
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1203 PM CST WED DEC 18 2013
.UPDATED FOR 18Z AVIATION DISCUSSION...
ISSUED AT 1131 AM CST WED DEC 18 2013
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CST WED DEC 18 2013
AT THIS TIME YESTERDAY MORNING...THE FORECAST AREA WAS 15-30 DEGREES
WARMER THAN WE ARE CURRENTLY. THE THERMOMETER WILL GET A WORKOUT
TODAY AND EVEN AFTER A CHILLY START...WE SHOULD REBOUND QUITE WELL
BY THE AFTERNOON. THE SURFACE RIDGE WILL BE OUT OVER LAKE MICHIGAN
BY 15Z AND THE APPROACHING CLIPPER SHOULD BE NEARING THE WESTERN MN
BORDER AROUND THE SAME TIME. THE WARM AIR ADVECTION OUT AHEAD OF THE
SURFACE LOW THIS MORNING IS IMPRESSIVE AND IT`S THE REASON WE`RE
FORECASTING THE WARMEST TEMPERATURES WE`VE SEEN IN OVER TWO WEEKS.
THE 18.07Z RAP HAS NEARLY THE ENTIRE FORECAST AREA ABOVE 0C AT 925MB
BY 00Z THIS EVENING /6-10C ACROSS MUCH OF WESTERN MN/ AND YOU`RE NOT
SEEING THINGS...THAT IS INDEED THE 0C ISOTHERM NEAR THE MN/IA BORDER
AT 700 MB. THIS SAME BUBBLE OF WARM AIR WAS OVER WESTERN NE AND SD
YESTERDAY AND BROUGHT HIGHS BETWEEN 40-60. NOW THE WARMEST TEMPS WERE
IN SNOW FREE AREAS...BUT LOWER 40S WERE OBSERVED EVEN WHERE THERE
WAS SNOW ON THE GROUND. WE WILL CERTAINLY BE COOLER THAN WHAT THE
PLAINS OBSERVED YESTERDAY...BUT THE DOWNSLOPE AREAS OF THE BUFFALO
RIDGE COULD EASILY SEE SOME LOWER 40S...ESPECIALLY IF WE ESTABLISH A
SOUTHWEST COMPONENT TO THE WIND BEFORE THE NOON HOUR. THE MIXING
WILL NOT BE GREAT TODAY...ESPECIALLY WITH THE MORNING INVERSION AND
SNOW COVER. WE SHOULDN`T MIX AS HIGH AS 925MB AND THIS WILL KEEP
HIGHS FROM GETTING TOO WARM. WE HOPE THIS LACK OF MIXING DOESN`T
MEAN WE`RE MUCH TOO WARM WITH THE TEMPS TODAY - VERIFICATION HAS
SHOWN A WARM BIAS LATELY - THOUGH THAT HAS BEEN WITH 15 TO 30 DEGREE
DEPARTURES FROM NORMAL. WE LIKE THE 18.00Z NAM MOS IN THAT IT KEPT
THE WESTERN FORECAST AREA WARM AND COOLED THE EAST. THERE SHOULD BE
A LARGE WEST-EAST TEMPERATURE GRADIENT TODAY /LOWER 40S FAR WEST -
MID TO UPPER 20S FAR EAST/. THE TWIN CITIES METRO IS RIGHT IN THE
MIDDLE OF THIS GRADIENT. THERE IS VIRTUALLY NO CHANCE FOR PRECIP IN
THE SHORT TERM...BUT PATCHY BLOWING SNOW CAN NOT BE COMPLETELY RULED
OUT LATE TONIGHT WHEN A PRONOUNCED AREA OF MSLP PRESSURE RISES
SLIDES ACROSS MN BEHIND THE CLIPPER SYSTEM. WE SAW BLOWING SNOW
YESTERDAY IN WESTERN MN...BUT THAT WAS WITH BL WINDS THAT WERE 5-7
KTS STRONGER. IN ADDITION...THE WARMER TEMPS TODAY SHOULD PROBABLY
ACT TO SETTLE THE CURRENT SNOW PACK A BIT.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 400 AM CST WED DEC 18 2013
ARCTIC AIR WILL OOZE IN ON THURSDAY AS A 1035MB HIGH BUILDS
SOUTHWARD INTO THE WESTERN HIGH PLAINS. WHILE THIS IS OCCURRING...
A SHORT WAVE WILL MOVE EAST FROM THE NORTHERN ROCKIES DURING THE
DAY BRINGING A SURGE OF MID LEVEL MOISTURE TO THE REGION. AMPLE
UPGLIDE... SATURATION AND ADIABATIC OMEGA ON THE NAM/GFS 290K
THETA SURFACES SPREAD INTO WEST CENTRAL MN BY NOON ON THURSDAY AND
ACROSS THE CWA BY EVENING. MIXING RATIOS RISE TO BETWEEN 2 AND 3
G/KG. HOWEVER...THE BEST ADIABATIC OMEGA ONLY LASTS FOR ABOUT 6
HOURS. CONTINUED THE TREND OF RAISING POPS WITH LIKELY FOR
THURSDAY AFTERNOON IN WEST CENTRAL MN WITH CATEGORICAL IN PLACE
FROM SOUTHWEST MN THROUGH THE TWIN CITIES AND ACROSS MUCH OF WEST
CENTRAL WI FOR THURSDAY EVENING. THE SNOW THEN TAPERS OFF
GRADUALLY OVERNIGHT FROM WEST TO EAST WITH SOME LINGERING LIGHT SNOW
FOR SOUTH CENTRAL MN THROUGH WEST CENTRAL WI ON FRIDAY. SNOW
AMOUNTS OF 1.5 TO 2 INCHES ARE LIKELY BY DAYBREAK FRIDAY...
ESPECIALLY ON AN EAST-WEST AXIS THAT RUNS THROUGH THE SOUTH
METRO...WITH A FEW MORE TENTHS OF AN INCH ON FRIDAY TO THE EAST
AND SOUTH OF THE METRO.
THE HIGH TO OUR WEST WILL BUILD IN FOR SATURDAY WITH A DRY BUT
COLD DAY. DIFFERENCES THEN EVOLVE BETWEEN THE ECMWF...GFS AND GEM
ON THE LATTER HALF OF THE WEEKEND AS A STORM SYSTEM EXITS THE
SOUTH PLAINS. THE ECMWF REMAINS DRY WITH THE NORTHWEST EDGE OF THE
PRECIPITATION FROM THIS SOUTHERN SYSTEM STAYING TO OUR SOUTHEAST.
THE GEM GOES HOG WILD DEVELOPING A CLOSED H7 LOW OVER US BY
SATURDAY NIGHT WITH 3 TO 5 INCHES OF SNOW FOR SATURDAY NIGHT AND
SUNDAY. THE GFS IS IN BETWEEN...HAVING TROUBLE SEPARATING THE
NORTHERN AND SOUTHERN STREAM ENERGY. COLLABORATION WAS TO FOLLOW
MORE OF THE DRY ECMWF SOLUTION AND REDUCE POPS FROM THE CR EXTEND.
A SECOND ARCTIC HIGH WILL BUILD IN FROM SUNDAY INTO MONDAY WITH
SOME VERY COLD AIR. DROPPED LOWS TO NEAR 15 BELOW FOR PORTIONS OF
CENTRAL MN FOR MONDAY MORNING WITH AROUND 5 BELOW IN THE TWIN
CITIES AND ZERO IN EAU CLAIRE. THIS MAY NOT BE COLD ENOUGH IF THE
ECMWF IS CORRECT WITH IT/S GUIDANCE SUGGESTING LOWERING LOWS
ANOTHER 5 TO 10 DEGREES.
SOME MODERATION IS EXPECTED BY CHRISTMAS EVE DAY AS THE FLOW
ALOFT BECOMES MORE WESTERLY AND THE HIGH DEPARTS TO OUR SOUTHEAST.
HOWEVER...ANOTHER SHORT WAVE AND LOW PRESSURE SYSTEM ARE RIDING
THE ARCTIC FRONT WITH SOME MORE SNOW POSSIBLE CHRISTMAS EVE AND
CHRISTMAS DAY.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1131 AM CST WED DEC 18 2013
VFR CONDITIONS SHOULD TODAY AHEAD OF AN APPROACHING COLD FRONT
FROM THE NORTH. ONCE THE FRONT PASSES THROUGH WINDS WILL INCREASE
OUT OF THE NORTH...WITH GUSTS NEAR 20KTS AT TIMES. THERE IS
INDICATION THAT MVFR CLOUDS WILL DEVELOP BEHIND THE FRONT AS
WELL FOR WEDNESDAY MORNING. LOOKING AHEAD...SNOW WILL DEVELOP
DURING THE AFTERNOON.
KMSP...
FRONTAL PASSAGE SHOULD BE AROUND 06Z...WITH NORTHERLY WINDS
THEREAFTER. MVFR CLOUDS CLOUD DEVELOP POST FRONTAL...SO HAVE
BROKEN DECK AFTER MIDNIGHT.
/OUTLOOK FOR KMSP/
WED EVENING...MVFR/IFR AND -SN. WINDS N AT 10KTS.
THU...LINGERING MVFR/IFR AND -SN. WINDS NW AT 10G20KTS.
FRI...VFR. WINDS SW AT 05KTS.
SAT...VFR. WINDS NW AT 10KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
SHORT TERM...CLF
LONG TERM...RAH
AVIATION...JRB
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
607 AM CST WED DEC 18 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CST WED DEC 18 2013
AT THIS TIME YESTERDAY MORNING...THE FORECAST AREA WAS 15-30 DEGREES
WARMER THAN WE ARE CURRENTLY. THE THERMOMETER WILL GET A WORKOUT
TODAY AND EVEN AFTER A CHILLY START...WE SHOULD REBOUND QUITE WELL
BY THE AFTERNOON. THE SURFACE RIDGE WILL BE OUT OVER LAKE MICHIGAN
BY 15Z AND THE APPROACHING CLIPPER SHOULD BE NEARING THE WESTERN MN
BORDER AROUND THE SAME TIME. THE WARM AIR ADVECTION OUT AHEAD OF THE
SURFACE LOW THIS MORNING IS IMPRESSIVE AND IT`S THE REASON WE`RE
FORECASTING THE WARMEST TEMPERATURES WE`VE SEEN IN OVER TWO WEEKS.
THE 18.07Z RAP HAS NEARLY THE ENTIRE FORECAST AREA ABOVE 0C AT 925MB
BY 00Z THIS EVENING /6-10C ACROSS MUCH OF WESTERN MN/ AND YOU`RE NOT
SEEING THINGS...THAT IS INDEED THE 0C ISOTHERM NEAR THE MN/IA BORDER
AT 700 MB. THIS SAME BUBBLE OF WARM AIR WAS OVER WESTERN NE AND SD
YESTERDAY AND BROUGHT HIGHS BETWEEN 40-60. NOW THE WARMEST TEMPS WERE
IN SNOW FREE AREAS...BUT LOWER 40S WERE OBSERVED EVEN WHERE THERE
WAS SNOW ON THE GROUND. WE WILL CERTAINLY BE COOLER THAN WHAT THE
PLAINS OBSERVED YESTERDAY...BUT THE DOWNSLOPE AREAS OF THE BUFFALO
RIDGE COULD EASILY SEE SOME LOWER 40S...ESPECIALLY IF WE ESTABLISH A
SOUTHWEST COMPONENT TO THE WIND BEFORE THE NOON HOUR. THE MIXING
WILL NOT BE GREAT TODAY...ESPECIALLY WITH THE MORNING INVERSION AND
SNOW COVER. WE SHOULDN`T MIX AS HIGH AS 925MB AND THIS WILL KEEP
HIGHS FROM GETTING TOO WARM. WE HOPE THIS LACK OF MIXING DOESN`T
MEAN WE`RE MUCH TOO WARM WITH THE TEMPS TODAY - VERIFICATION HAS
SHOWN A WARM BIAS LATELY - THOUGH THAT HAS BEEN WITH 15 TO 30 DEGREE
DEPARTURES FROM NORMAL. WE LIKE THE 18.00Z NAM MOS IN THAT IT KEPT
THE WESTERN FORECAST AREA WARM AND COOLED THE EAST. THERE SHOULD BE
A LARGE WEST-EAST TEMPERATURE GRADIENT TODAY /LOWER 40S FAR WEST -
MID TO UPPER 20S FAR EAST/. THE TWIN CITIES METRO IS RIGHT IN THE
MIDDLE OF THIS GRADIENT. THERE IS VIRTUALLY NO CHANCE FOR PRECIP IN
THE SHORT TERM...BUT PATCHY BLOWING SNOW CAN NOT BE COMPLETELY RULED
OUT LATE TONIGHT WHEN A PRONOUNCED AREA OF MSLP PRESSURE RISES
SLIDES ACROSS MN BEHIND THE CLIPPER SYSTEM. WE SAW BLOWING SNOW
YESTERDAY IN WESTERN MN...BUT THAT WAS WITH BL WINDS THAT WERE 5-7
KTS STRONGER. IN ADDITION...THE WARMER TEMPS TODAY SHOULD PROBABLY
ACT TO SETTLE THE CURRENT SNOW PACK A BIT.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 400 AM CST WED DEC 18 2013
ARCTIC AIR WILL OOZE IN ON THURSDAY AS A 1035MB HIGH BUILDS
SOUTHWARD INTO THE WESTERN HIGH PLAINS. WHILE THIS IS OCCURRING...
A SHORT WAVE WILL MOVE EAST FROM THE NORTHERN ROCKIES DURING THE
DAY BRINGING A SURGE OF MID LEVEL MOISTURE TO THE REGION. AMPLE
UPGLIDE... SATURATION AND ADIABATIC OMEGA ON THE NAM/GFS 290K
THETA SURFACES SPREAD INTO WEST CENTRAL MN BY NOON ON THURSDAY AND
ACROSS THE CWA BY EVENING. MIXING RATIOS RISE TO BETWEEN 2 AND 3
G/KG. HOWEVER...THE BEST ADIABATIC OMEGA ONLY LASTS FOR ABOUT 6
HOURS. CONTINUED THE TREND OF RAISING POPS WITH LIKELY FOR
THURSDAY AFTERNOON IN WEST CENTRAL MN WITH CATEGORICAL IN PLACE
FROM SOUTHWEST MN THROUGH THE TWIN CITIES AND ACROSS MUCH OF WEST
CENTRAL WI FOR THURSDAY EVENING. THE SNOW THEN TAPERS OFF
GRADUALLY OVERNIGHT FROM WEST TO EAST WITH SOME LINGERING LIGHT SNOW
FOR SOUTH CENTRAL MN THROUGH WEST CENTRAL WI ON FRIDAY. SNOW
AMOUNTS OF 1.5 TO 2 INCHES ARE LIKELY BY DAYBREAK FRIDAY...
ESPECIALLY ON AN EAST-WEST AXIS THAT RUNS THROUGH THE SOUTH
METRO...WITH A FEW MORE TENTHS OF AN INCH ON FRIDAY TO THE EAST
AND SOUTH OF THE METRO.
THE HIGH TO OUR WEST WILL BUILD IN FOR SATURDAY WITH A DRY BUT
COLD DAY. DIFFERENCES THEN EVOLVE BETWEEN THE ECMWF...GFS AND GEM
ON THE LATTER HALF OF THE WEEKEND AS A STORM SYSTEM EXITS THE
SOUTH PLAINS. THE ECMWF REMAINS DRY WITH THE NORTHWEST EDGE OF THE
PRECIPITATION FROM THIS SOUTHERN SYSTEM STAYING TO OUR SOUTHEAST.
THE GEM GOES HOG WILD DEVELOPING A CLOSED H7 LOW OVER US BY
SATURDAY NIGHT WITH 3 TO 5 INCHES OF SNOW FOR SATURDAY NIGHT AND
SUNDAY. THE GFS IS IN BETWEEN...HAVING TROUBLE SEPARATING THE
NORTHERN AND SOUTHERN STREAM ENERGY. COLLABORATION WAS TO FOLLOW
MORE OF THE DRY ECMWF SOLUTION AND REDUCE POPS FROM THE CR EXTEND.
A SECOND ARCTIC HIGH WILL BUILD IN FROM SUNDAY INTO MONDAY WITH
SOME VERY COLD AIR. DROPPED LOWS TO NEAR 15 BELOW FOR PORTIONS OF
CENTRAL MN FOR MONDAY MORNING WITH AROUND 5 BELOW IN THE TWIN
CITIES AND ZERO IN EAU CLAIRE. THIS MAY NOT BE COLD ENOUGH IF THE
ECMWF IS CORRECT WITH IT/S GUIDANCE SUGGESTING LOWERING LOWS
ANOTHER 5 TO 10 DEGREES.
SOME MODERATION IS EXPECTED BY CHRISTMAS EVE DAY AS THE FLOW
ALOFT BECOMES MORE WESTERLY AND THE HIGH DEPARTS TO OUR SOUTHEAST.
HOWEVER...ANOTHER SHORT WAVE AND LOW PRESSURE SYSTEM ARE RIDING
THE ARCTIC FRONT WITH SOME MORE SNOW POSSIBLE CHRISTMAS EVE AND
CHRISTMAS DAY.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 541 AM CST WED DEC 18 2013
NO SIGNIFICANT AVIATION WEATHER CONCERNS TODAY OR TONIGHT. THERE
IS A SYSTEM APPROACHING...SO THE WINDS WILL VEER AROUND 180
DEGREES FROM THE SOUTHEAST WINDS OUT THERE THIS MORNING. SPEEDS
WILL REMAIN PRETTY CONSISTENT BETWEEN 8-12 KTS...WITH A BETTER
CHANCE FOR GUSTS UP NEAR 20-25 KTS WHEN THE COLD FRONT COMES
THROUGH TONIGHT AND THE WINDS ARE CLOSER TO 310 DEGREES.
KMSP...
TIMING THE VEERING WINDS IS THE BIGGEST CHALLENGE TODAY WITH NO
VIS/CIG RESTRICTIONS. GOOD CONFIDENCE IN THE WIND DIRECTIONAL
SHIFT IN THE TAF WITHIN 1-2 HOURS AND 10-30 DEGREES. OTHERWISE NO
ISSUES WITH SNOW HOLDING OFF UNTIL THURSDAY EVENING.
/OUTLOOK FOR KMSP/
THU NIGHT...MVFR CIGS WITH IFR VIS WITH -SN. LIFR VIS POSSIBLE. WINDS
N 10-15 KT.
FRI...MVFR CIGS WITH LINGERING IFR/-SN POSSIBLE EARLY. WINDS N
10-15 KT.
SAT...MAINLY VFR. WINDS S 5 KT BCMG NW.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
SHORT TERM...CLF
LONG TERM...RAH
AVIATION...CLF
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
401 AM CST WED DEC 18 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CST WED DEC 18 2013
AT THIS TIME YESTERDAY MORNING...THE FORECAST AREA WAS 15-30 DEGREES
WARMER THAN WE ARE CURRENTLY. THE THERMOMETER WILL GET A WORKOUT
TODAY AND EVEN AFTER A CHILLY START...WE SHOULD REBOUND QUITE WELL
BY THE AFTERNOON. THE SURFACE RIDGE WILL BE OUT OVER LAKE MICHIGAN
BY 15Z AND THE APPROACHING CLIPPER SHOULD BE NEARING THE WESTERN MN
BORDER AROUND THE SAME TIME. THE WARM AIR ADVECTION OUT AHEAD OF THE
SURFACE LOW THIS MORNING IS IMPRESSIVE AND IT`S THE REASON WE`RE
FORECASTING THE WARMEST TEMPERATURES WE`VE SEEN IN OVER TWO WEEKS.
THE 18.07Z RAP HAS NEARLY THE ENTIRE FORECAST AREA ABOVE 0C AT 925MB
BY 00Z THIS EVENING /6-10C ACROSS MUCH OF WESTERN MN/ AND YOU`RE NOT
SEEING THINGS...THAT IS INDEED THE 0C ISOTHERM NEAR THE MN/IA BORDER
AT 700 MB. THIS SAME BUBBLE OF WARM AIR WAS OVER WESTERN NE AND SD
YESTERDAY AND BROUGHT HIGHS BETWEEN 40-60. NOW THE WARMEST TEMPS WERE
IN SNOW FREE AREAS...BUT LOWER 40S WERE OBSERVED EVEN WHERE THERE
WAS SNOW ON THE GROUND. WE WILL CERTAINLY BE COOLER THAN WHAT THE
PLAINS OBSERVED YESTERDAY...BUT THE DOWNSLOPE AREAS OF THE BUFFALO
RIDGE COULD EASILY SEE SOME LOWER 40S...ESPECIALLY IF WE ESTABLISH A
SOUTHWEST COMPONENT TO THE WIND BEFORE THE NOON HOUR. THE MIXING
WILL NOT BE GREAT TODAY...ESPECIALLY WITH THE MORNING INVERSION AND
SNOW COVER. WE SHOULDN`T MIX AS HIGH AS 925MB AND THIS WILL KEEP
HIGHS FROM GETTING TOO WARM. WE HOPE THIS LACK OF MIXING DOESN`T
MEAN WE`RE MUCH TOO WARM WITH THE TEMPS TODAY - VERIFICATION HAS
SHOWN A WARM BIAS LATELY - THOUGH THAT HAS BEEN WITH 15 TO 30 DEGREE
DEPARTURES FROM NORMAL. WE LIKE THE 18.00Z NAM MOS IN THAT IT KEPT
THE WESTERN FORECAST AREA WARM AND COOLED THE EAST. THERE SHOULD BE
A LARGE WEST-EAST TEMPERATURE GRADIENT TODAY /LOWER 40S FAR WEST -
MID TO UPPER 20S FAR EAST/. THE TWIN CITIES METRO IS RIGHT IN THE
MIDDLE OF THIS GRADIENT. THERE IS VIRTUALLY NO CHANCE FOR PRECIP IN
THE SHORT TERM...BUT PATCHY BLOWING SNOW CAN NOT BE COMPLETELY RULED
OUT LATE TONIGHT WHEN A PRONOUNCED AREA OF MSLP PRESSURE RISES
SLIDES ACROSS MN BEHIND THE CLIPPER SYSTEM. WE SAW BLOWING SNOW
YESTERDAY IN WESTERN MN...BUT THAT WAS WITH BL WINDS THAT WERE 5-7
KTS STRONGER. IN ADDITION...THE WARMER TEMPS TODAY SHOULD PROBABLY
ACT TO SETTLE THE CURRENT SNOW PACK A BIT.
.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 400 AM CST WED DEC 18 2013
ARCTIC AIR WILL OOZE IN ON THURSDAY AS A 1035MB HIGH BUILDS
SOUTHWARD INTO THE WESTERN HIGH PLAINS. WHILE THIS IS OCCURRING...
A SHORT WAVE WILL MOVE EAST FROM THE NORTHERN ROCKIES DURING THE
DAY BRINGING A SURGE OF MID LEVEL MOISTURE TO THE REGION. AMPLE
UPGLIDE... SATURATION AND ADIABATIC OMEGA ON THE NAM/GFS 290K
THETA SURFACES SPREAD INTO WEST CENTRAL MN BY NOON ON THURSDAY AND
ACROSS THE CWA BY EVENING. MIXING RATIOS RISE TO BETWEEN 2 AND 3
G/KG. HOWEVER...THE BEST ADIABATIC OMEGA ONLY LASTS FOR ABOUT 6
HOURS. CONTINUED THE TREND OF RAISING POPS WITH LIKELY FOR
THURSDAY AFTERNOON IN WEST CENTRAL MN WITH CATEGORICAL IN PLACE
FROM SOUTHWEST MN THROUGH THE TWIN CITIES AND ACROSS MUCH OF WEST
CENTRAL WI FOR THURSDAY EVENING. THE SNOW THEN TAPERS OFF
GRADUALLY OVERNIGHT FROM WEST TO EAST WITH SOME LINGERING LIGHT SNOW
FOR SOUTH CENTRAL MN THROUGH WEST CENTRAL WI ON FRIDAY. SNOW
AMOUNTS OF 1.5 TO 2 INCHES ARE LIKELY BY DAYBREAK FRIDAY...
ESPECIALLY ON AN EAST-WEST AXIS THAT RUNS THROUGH THE SOUTH
METRO...WITH A FEW MORE TENTHS OF AN INCH ON FRIDAY TO THE EAST
AND SOUTH OF THE METRO.
THE HIGH TO OUR WEST WILL BUILD IN FOR SATURDAY WITH A DRY BUT
COLD DAY. DIFFERENCES THEN EVOLVE BETWEEN THE ECMWF...GFS AND GEM
ON THE LATTER HALF OF THE WEEKEND AS A STORM SYSTEM EXITS THE
SOUTH PLAINS. THE ECMWF REMAINS DRY WITH THE NORTHWEST EDGE OF THE
PRECIPITATION FROM THIS SOUTHERN SYSTEM STAYING TO OUR SOUTHEAST.
THE GEM GOES HOG WILD DEVELOPING A CLOSED H7 LOW OVER US BY
SATURDAY NIGHT WITH 3 TO 5 INCHES OF SNOW FOR SATURDAY NIGHT AND
SUNDAY. THE GFS IS IN BETWEEN...HAVING TROUBLE SEPARATING THE
NORTHERN AND SOUTHERN STREAM ENERGY. COLLABORATION WAS TO FOLLOW
MORE OF THE DRY ECMWF SOLUTION AND REDUCE POPS FROM THE CR EXTEND.
A SECOND ARCTIC HIGH WILL BUILD IN FROM SUNDAY INTO MONDAY WITH
SOME VERY COLD AIR. DROPPED LOWS TO NEAR 15 BELOW FOR PORTIONS OF
CENTRAL MN FOR MONDAY MORNING WITH AROUND 5 BELOW IN THE TWIN
CITIES AND ZERO IN EAU CLAIRE. THIS MAY NOT BE COLD ENOUGH IF THE
ECMWF IS CORRECT WITH IT/S GUIDANCE SUGGESTING LOWERING LOWS
ANOTHER 5 TO 10 DEGREES.
SOME MODERATION IS EXPECTED BY CHRISTMAS EVE DAY AS THE FLOW
ALOFT BECOMES MORE WESTERLY AND THE HIGH DEPARTS TO OUR SOUTHEAST.
HOWEVER...ANOTHER SHORT WAVE AND LOW PRESSURE SYSTEM ARE RIDING
THE ARCTIC FRONT WITH SOME MORE SNOW POSSIBLE CHRISTMAS EVE AND
CHRISTMAS DAY.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1008 PM CST TUE DEC 17 2013
VFR CONDITIONS THROUGHOUT PERIOD. SOME MID/HIGH LEVEL CLOUDS OUT
AHEAD OF NEXT COLD FRONT WHICH WILL MOVE INTO CENTRAL MN AFTER
00Z.19. SURFACE WINDS BECOMING SOUTH/SOUTHEAST INTO THE MORNING
AND THEN SOUTHWEST TO WEST AHEAD OF COLD FRONT. INITIAL FROPA
WILL YIELD NW WINDS BUT GENERALLY LESS THAN 10 KNOTS. WINDS WILL
LIKELY INCREASE AS ARCTIC FRONT SAGS INTO THE AREA AFTER 06Z.19.
KMSP...VFR CONDITIONS. SURFACE WINDS BECOMING SOUTHEAST/SOUTH
OVERNIGHT AND INTO WEDNESDAY...BEFORE BECOMING SOUTHWEST LATE
AFTERNOON AND NORTHWEST AFTER 03Z.19.
/OUTLOOK FOR KMSP/
THU...MVFR CIGS WITH IFR/-SN POSSIBLE. WINDS N 10-15 KT.
FRI...MVFR CIGS WITH LINGERING IFR/-SN POSSIBLE. WINDS N 10-15 KT.
SAT...MAINLY VFR. MVFR CIGS POSSIBLE. WINDS S 5 KT BCMG NW.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
SHORT TERM...CLF
LONG TERM...RAH
AVIATION...DWE
AREA FORECAST DISCUSSION
NWS ELKO NV
1131 AM PST WED DEC 18 2013
.SYNOPSIS...A LOW PRESSURE SYSTEM WILL BRING SNOW TO THE GREAT
BASIN TONIGHT AND THURSDAY. SNOW SHOWERS ARE EXPECTED AGAIN OVER
THE WEEKEND. ALTHOUGH THERE MAY BE SOME SNOW SHOWERS AROUND...AT
THIS TIME NO TRAVEL CONCERNS ARE ANTICIPATED FOR THE WEEK OF
CHRISTMAS.
&&
.UPDATE...IN THE NEXT COUPLE OF HOURS...ISOLATED RAIN SHOWERS ARE
EXPECTED TO MOVE INTO PORTIONS OF NORTHER LANDER AND EXTREME
SOUTHEAST HUMBOLDT COUNTY. WITH THE STRONG INVERSION IN
PLACE...VALLEY TEMPERATURES REMAIN BELOW FREEZING. THIS WILL
CREATE ISOLATED AREAS OF LIGHT FREEZING RAIN THROUGH THE
AFTERNOON. SOME SLICK SPOTS ARE POSSIBLE ON I80 AND STATE ROUTE
305. ALSO RAISED POPS ACROSS CENTRAL NEVADA AND LOWERED TEMPS
ACROSS ENTIRE CWA.
&&
.PREV DISCUSSION... /ISSUED AT 259 AM /
SYNOPSIS...A LOW PRESSURE SYSTEM WILL BRING SNOW TO THE GREAT
BASIN TONIGHT AND THURSDAY. SNOW SHOWERS ARE EXPECTED AGAIN OVER
THE WEEKEND. ALTHOUGH THERE MAY BE SOME SNOW SHOWERS AROUND...AT
THIS TIME NO TRAVEL CONCERNS ARE ANTICIPATED FOR THE WEEK OF
CHRISTMAS.
SHORT TERM...TODAY THROUGH FRIDAY. HIGH PRESSURE TO OUR SOUTH IS
BATTLING AN INCOMING SHORTWAVE THIS MORNING. IR IMAGERY SHOWS A
LOT OF MID TO HIGH CLOUDINESS SPREADING ACROSS THE SIERRA
MOUNTAIN RANGE AND INTO THE GREAT BASIN AS PACIFIC MOISTURE ALOFT
ASSOCIATED WITH THE TROUGH TO BE BEGINS STREAMING INTO OREGON AND
WASHINGTON STATE. WATER VAPOR IMAGERY REVEALS FEWER CLOUDS ACROSS
NORTHWEST NEVADA AT THIS TIME...BETWIXT THE TWO UPPER LEVEL
FEATURES. OTHERWISE...PRETTY QUIET THIS MORNING. TEMPERATURES ARE
WARMER THAN RECENT NIGHTS AND DEW POINTS ARE 10 DEGREES OR MORE ALL
ACROSS THE BOARD. THE MODELS SEEM TO BE IN VERY GOOD AGREEMENT FOR
THE SHORT TERM.
WEDNESDAY MORNING. THIS WILL BE A DRY PERIOD. THERE MAY STILL BE SOME
POCKETS OF FOG AHEAD OF ANTICIPATED TROUGH DEVELOPMENT...MORE
LIKELY IN THE AREA OF WINNEMUCCA WHERE CLOUDINESS IS LESS EVIDENT.
WEDNESDAY AFTERNOON THROUGH EARLY WEDNESDAY EVENING. A TROUGH
WILL BEGIN TO DEVELOP OVER CANADA AND DROP DOWN. THE TROUGH AXIS
WILL ALIGN THROUGH OR/WA/CA BY LATE EVENING. THE RR QUAD REGIONS
OF A TWIN JET CORE IS SHOWN TO BEGIN INFILTRATING NORTHERN NEVADA
BY THIS EVENING. LIGHT SNOW SHOWERS ARE EXPECTED TO BEGIN OVER
CENTRAL NEVADA THIS AFTERNOON AND THEN DEVELOP ACROSS MOST AREAS
BY THIS EVENING. HIGH TEMPERATURES WILL RANGE FROM THE MID 30S
NORTH TO THE MID 50S SOUTH OF HIGHWAY 50.
LATE WEDNESDAY EVENING THROUGH THURSDAY NIGHT. A WINTER STORM
WATCH IS IN EFFECT FOR NORTHERN NYE AND WHITE PINE COUNTIES. A
TROUGH AXIS WILL TRAVERSE THE GREAT BASIN AS CENTRAL LOW PRESSURE
DEEPENS WHILE IT RELOCATES TO THE NORTHERN BAJA REGION. A STRONG
AREA OF LOW LEVEL CONVERGENCE WILL CENTER OVER WHITE PINE COUNTY
AND MODEL QPF IS SIGNIFICANT OVER NYE COUNTY AND WHITE PINE
COUNTY. AT THIS TIME APPEARS THIS SYSTEM COULD PRODUCE 3 TO 5
INCHES OF SNOWFALL TO THE VALLEYS OF CENTRAL NEVADA WITH
ELEVATIONS ABOVE 6500 FEET RECEIVING A FOOT OF SNOW. VALLEY
AMOUNTS MAY CHANGE SO THE WINTER STORM WATCH WAS NOT ISSUED FOR A
SPECIFIC ELEVATION. AN INCH OR TWO OF SNOW IS EXPECTED ELSEWHERE
INCLUDING THE ELKO AND SPRING CREEK AREAS. WINDS WILL BE BREEZY
ACROSS HUMBOLDT COUNTY AS MEAN LOW PRESSURE DROPS BEHIND THE
SIERRAS IN THE AFTERNOON. SHOWERS SHOULD RAPIDLY TAPER OFF AROUND
MIDNIGHT. LEFT SOME LOW POPS IN FOR WHITE PINE COUNTY AFTER
MIDNIGHT THURSDAY. HIGH TEMPERATURES WILL RANGE FROM THE MID 20S
NORTH TO AROUND 40 SOUTH OF HIGHWAY 50. LOW TEMPERATURES WILL BE
IN THE 20S WEDNESDAY NIGHT AND IN THE SINGLE DIGITS THURSDAY
NIGHT.
FRIDAY. A SHORT WAVE RIDGE WILL BEGIN TO RAPIDLY PUSH ACROSS THE
GREAT BASIN. A NORTHWEST FLOW ALOFT INDICATES THIS SHALLOW RIDGE WILL
BE DIRTY. SO INTRODUCED LOW POPS ACROSS NORTHERN NEVADA. HIGH
TEMPERATURES WILL BE IN THE 20S TO AROUND 30 DEGREES.
LONG TERM...FRIDAY NIGHT THROUGH NEXT TUESDAY. THE PERIOD COMMENCES
WITH COASTAL RIDGING FROM BRITISH COLUMBIA TO SOUTHERN CALIFORNIA
WITH THE TROF AXIS OVER THE ROCKIES...AND THE JET CORE OVER THE
SILVER STATE. THE JET PLACEMENT...ALONG WITH THE SPIKE IN PWS
SUGGEST SNOW ACCUMULATIONS IN EASTERN HUMBOLDT COUNTY AND PORTIONS
OF ELKO COUNTY...WITH THE BEST ACCUMULATIONS IN OROGRAPHICALLY
FAVORED NORTH FACING SLOPES. THE VALLEYS OF ELKO AND EASTERN HUMBOLDT COUNTY
WILL LIKELY RECEIVE LESS THAN 2 INCHES OF SNOW FRIDAY NIGHT INTO
SATURDAY. AS TIME ELAPSES...SHOWERS TAPER OFF ACROSS NORTHEASTERN
NEVADA INTO SUNDAY...WITH SOME LINGERING ISOLATED SHOWERS POSSIBLE
ACROSS MOUNTAINS. THE NAEFS AND THE GFS ARE BOTH SHOWING NEAR
NORMAL TEMPERATURES TO SLIGHTLY ABOVE NORMAL TEMPERATURES BY DAY 7.
THE ONLY CONCERN HERE IS THAT THE MODELS MAY BE WARMING IT UP A
SKOSH TOO FAST IN THE GREAT BASIN...AS OFTEN...SNOW EVENTS FOLLOWED
BY NORTHERLY FLOW RESULT IN COLD TEMPS. INTERESTINGLY...THE RMOP OF
THE ENSEMBLE MEAN FORECAST...SHOWS STRONG/HIGH RMOP OVER THE LKN CWA
LATE IN THE PERIOD BUT STRUGGLES EARLIER IN THE PERIOD WITH THE
NORTHERLY FLOW.
AVIATION...VFR CONDITIONS ARE EXPECTED AT ALL TAF SITES.
&&
.LKN WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM 10 PM PST THIS EVENING THROUGH THURSDAY
EVENING FOR NORTHEASTERN NYE COUNTY...NORTHWESTERN NYE COUNTY...
WHITE PINE COUNTY.
&&
$$
94/99
AREA FORECAST DISCUSSION
NWS ELKO NV
259 AM PST WED DEC 18 2013
.SYNOPSIS...A LOW PRESSURE SYSTEM WILL BRING SNOW TO THE GREAT
BASIN TONIGHT AND THURSDAY. SNOW SHOWERS ARE EXPECTED AGAIN OVER
THE WEEKEND. ALTHOUGH THERE MAY BE SOME SNOW SHOWERS AROUND...AT
THIS TIME NO TRAVEL CONCERNS ARE ANTICIPATED FOR THE WEEK OF
CHRISTMAS.
&&
.SHORT TERM...TODAY THROUGH FRIDAY. HIGH PRESSURE TO OUR SOUTH IS
BATTLING AN INCOMING SHORTWAVE THIS MORNING. IR IMAGERY SHOWS A
LOT OF MID TO HIGH CLOUDINESS SPREADING ACROSS THE SIERRA
MOUNTAIN RANGE AND INTO THE GREAT BASIN AS PACIFIC MOISTURE ALOFT
ASSOCIATED WITH THE TROUGH TO BE BEGINS STREAMING INTO OREGON AND
WASHINGTON STATE. WATER VAPOR IMAGERY REVEALS FEWER CLOUDS ACROSS
NORTHWEST NEVADA AT THIS TIME...BETWIXT THE TWO UPPER LEVEL
FEATURES. OTHERWISE...PRETTY QUIET THIS MORNING. TEMPERATURES ARE
WARMER THAN RECENT NIGHTS AND DEWPOINTS ARE 10 DEGREES OR MORE ALL
ACROSS THE BOARD. THE MODELS SEEM TO BE IN VERY GOOD AGREEMENT FOR
THE SHORT TERM.
WEDNESDAY MORNING. THIS WILL BE A DRY PERIOD. THERE MAY STILL BE SOME
POCKETS OF FOG AHEAD OF ANTICIPATED TROUGH DEVELOPMENT...MORE
LIKELY IN THE AREA OF WINNEMUCCA WHERE CLOUDINESS IS LESS EVIDENT.
WEDNESDAY AFTERNOON THROUGH EARLY WEDNESDAY EVENING. A TROUGH
WILL BEGIN TO DEVELOP OVER CANADA AND DROP DOWN. THE TROUGH AXIS
WILL ALIGN THROUGH OR/WA/CA BY LATE EVENING. THE RR QUAD REGIONS
OF A TWIN JET CORE IS SHOWN TO BEGIN INFILTRATING NORTHERN NEVADA
BY THIS EVENING. LIGHT SNOW SHOWERS ARE EXPECTED TO BEGIN OVER
CENTRAL NEVADA THIS AFTERNOON AND THEN DEVELOP ACROSS MOST AREAS
BY THIS EVENING. HIGH TEMPERATURES WILL RANGE FROM THE MID 30S
NORTH TO THE MID 50S SOUTH OF HIGHWAY 50.
LATE WEDNESDAY EVENING THROUGH THURSDAY NIGHT. A WINTER STORM
WATCH IS IN EFFECT FOR NORTHERN NYE AND WHITE PINE COUNTIES. A
TROUGH AXIS WILL TRAVERSE THE GREAT BASIN AS CENTRAL LOW PRESSURE
DEEPENS WHILE IT RELOCATES TO THE NORTHERN BAJA REGION. A STRONG
AREA OF LOW LEVEL CONVERGENCE WILL CENTER OVER WHITE PINE COUNTY
AND MODEL QPF IS SIGNIFICANT OVER NYE COUNTY AND WHITE PINE
COUNTY. AT THIS TIME APPEARS THIS SYSTEM COULD PRODUCE 3 TO 5
INCHES OF SNOWFALL TO THE VALLEYS OF CENTRAL NEVADA WITH
ELEVATIONS ABOVE 6500 FEET RECEIVING A FOOT OF SNOW. VALLEY
AMOUNTS MAY CHANGE SO THE WINTER STORM WATCH WAS NOT ISSUED FOR A
SPECIFIC ELEVATION. AN INCH OR TWO OF SNOW IS EXPECTED ELSEWHERE
INCLUDING THE ELKO AND SPRING CREEK AREAS. WINDS WILL BE BREEZY
ACROSS HUMBOLDT COUNTY AS MEAN LOW PRESSURE DROPS BEHIND THE
SIERRAS IN THE AFTERNOON. SHOWERS SHOULD RAPIDLY TAPER OFF AROUND
MIDNIGHT. LEFT SOME LOW POPS IN FOR WHITE PINE COUNTY AFTER
MIDNIGHT THURSDAY. HIGH TEMPERATURES WILL RANGE FROM THE MID 20S
NORTH TO AROUND 40 SOUTH OF HIGHWAY 50. LOW TEMPERATURES WILL BE
IN THE 20S WEDNESDAY NIGHT AND IN THE SINGLE DIGITS THURSDAY
NIGHT.
FRIDAY. A SHORT WAVE RIDGE WILL BEGIN TO RAPIDLY PUSH ACROSS THE
GREAT BASIN. A NORTHWEST FLOW ALOFT INDICATES THIS SHALLOW RIDGE WILL
BE DIRTY. SO INTRODUCED LOW POPS ACROSS NORTHERN NEVADA. HIGH
TEMPERATURES WILL BE IN THE 20S TO AROUND 30 DEGREES.
.LONG TERM...FRIDAY NIGHT THROUGH NEXT TUESDAY. THE PERIOD COMMENCES
WITH COASTAL RIDGING FROM BRITISH COLUMBIA TO SOUTHERN CALIFORNIA
WITH THE TROF AXIS OVER THE ROCKIES...AND THE JET CORE OVER THE
SILVER STATE. THE JET PLACEMENT...ALONG WITH THE SPIKE IN PWS
SUGGEST SNOW ACCUMULATIONS IN EASTERN HUMBOLDT COUNTY AND PORTIONS
OF ELKO COUNTY...WITH THE BEST ACCUMULATIONS IN OROGRAPHICALLY
FAVORED NORTH FACING SLOPES. THE VALLEYS OF ELKO AND EASTERN HUMBOLDT COUNTY
WILL LIKELY RECEIVE LESS THAN 2 INCHES OF SNOW FRIDAY NIGHT INTO
SATURDAY. AS TIME ELAPSES...SHOWERS TAPER OFF ACROSS NORTHEASTERN
NEVADA INTO SUNDAY...WITH SOME LINGERING ISOLATED SHOWERS POSSIBLE
ACROSS MOUNTAINS. THE NAEFS AND THE GFS ARE BOTH SHOWING NEAR
NORMAL TEMPERATURES TO SLIGHTLY ABOVE NORMAL TEMPERATURES BY DAY 7.
THE ONLY CONCERN HERE IS THAT THE MODELS MAY BE WARMING IT UP A
SKOSH TOO FAST IN THE GREAT BASIN...AS OFTEN...SNOW EVENTS FOLLOWED
BY NORTHERLY FLOW RESULT IN COLD TEMPS. INTERESTINGLY...THE RMOP OF
THE ENSEMBLE MEAN FORECAST...SHOWS STRONG/HIGH RMOP OVER THE LKN CWA
LATE IN THE PERIOD BUT STRUGGLES EARLIER IN THE PERIOD WITH THE
NORTHERLY FLOW.
&&
.AVIATION...VFR CONDITIONS ARE EXPECTED AT ALL TAF SITES.
&&
.LKN WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY EVENING
FOR NORTHEASTERN NYE COUNTY...NORTHWESTERN NYE COUNTY...WHITE
PINE COUNTY.
&&
$$
92/97/97
AREA FORECAST DISCUSSION
NWS BINGHAMTON NY
1017 PM EST THU DEC 19 2013
.SYNOPSIS...
LIGHT RAIN AND DRIZZLE WILL BE POSSIBLE ACROSS PORTIONS OF CENTRAL
NEW YORK OVERNIGHT AS A WARM FRONT LIFTS NORTH TOWARDS THE
AREA...WHILE NORTHEAST PENNSYLVANIA STAYS DRY. UNSEASONABLY MILD
AIR WILL RETURN TO THE REGION FRIDAY ONWARD AS SOUTHERLY FLOW
INCREASES AND A FRONTAL BOUNDARY STALLS JUST NORTH OF OUR AREA.
RAIN CHANCES WILL BE ON THE INCREASE HEADING INTO THE WEEKEND AS A
SERIES OF LOW PRESSURE SYSTEMS TRACK NORTH ALONG THE STALLED
FRONT. COLDER AIR RETURNS EARLY NEXT WEEK FOLLOWING A STRONG COLD
FRONT SUNDAY NIGHT.
&&
.NEAR TERM /THROUGH FRIDAY/...
1015 PM UPDATE...
BASED ON LATEST MODEL TRENDS AND UPSTREAM OBSERVATION...I WAS
ABLE TO FURTHER DELAY AND PARE BACK AMOUNT OF PATCHY
DRIZZLE/CHANCES OF LIGHT RAIN INTO LATER TONIGHT THROUGH FRIDAY
MORNING TO MAINLY JUST FINGER LAKES THROUGH MOHAWK VALLEY REGIONS
WITH BEST CHANCES NORTH OF NY THRUWAY. TEMPERATURE GUIDANCE AND
SOUNDINGS ALSO SUGGEST THAT FREEZING DRIZZLE/SPOTTY LIGHT FREEZING
RAIN POSSIBILITY WILL BE LIMITED TO HIGHER ELEVATIONS OF NORTHERN
ONEIDA COUNTY...AND EVEN THAT IS BRIEF AND IFFY BECAUSE OF STEADY
TO SLOWLY RISING TREND IN TEMPERATURES AFTER MIDNIGHT ACROSS MOST
OF CENTRAL NEW YORK. FORECAST DETAILS ADJUSTED ACCORDINGLY.
PREVIOUS DISCUSSION...
MAIN CONCERN HEADING INTO THE OVERNIGHT PERIOD REMAINS FOCUSED ON
THE AFOREMENTIONED FRONTAL BOUNDARY AND THE POSSIBILITY FOR
DEVELOPING LIGHT RAIN/DRIZZLE AND EVEN SOME SPOTTY FREEZING
DRIZZLE ACROSS PORTIONS OF CENTRAL NEW YORK AND NORTHEAST PA AFTER
MIDNIGHT.
FROM THIS VANTAGE POINT...BEST ISENTROPIC ASCENT ALONG THE 285
AND 290K THETA-E SURFACES REMAINS WELL NORTH AND WEST OF THE FCST
REGION AS STRONGEST SOUTHERLY FLOW REMAINS ACROSS THE OHIO VLY.
IN ADDITION TO THIS...WARM AIR ADVECTION TO CONTINUE THROUGH THE
OVERNIGHT WHICH COMBINED WITH INCREASING CLOUD COVER SHOULD KEEP
TEMPS FROM FALLING TOO MUCH WITH LOSS OF DAYTIME HEATING. AS A
RESULT...HAVE ELECTED TO FURTHER TRIM BACK ON INHERITED FZRA/FZDZ
MENTION WITH MAIN AREAS NOW HIGHLIGHT ACROSS THE SOUTHERN TUG
HILL...WESTERN CATSKILLS...AND THE CENTRAL SOUTHERN TIER WHERE
ENOUGH COOLING MAY OCCUR IN THE VALLEY LOCATIONS TO ALLOW TEMPS
TO APPROACH FREEZING FOR A SHORT TIME. DESPITE THIS...OVERALL
FZRA/FZDZ THREAT APPEARS FAIRLY LIMITED BASED ON PROJECTED TEMP
TRENDS AND WILL HOLD-OFF ON ANY HEADLINES AS ACTIVITY SHOULD
REMAIN FAIRLY ISOLATED.
AS STATED ABOVE...EXPECT TEMPS TO SLOWLY DECREASE AFTER SUNSET
BEFORE HOLDING STEADY AND MAYBE RISING TOWARDS MORNING AS WARM AIR
ADVECTION INCREASES. OVERNIGHT LOWS WILL LIKELY BOTTOM OUT IN THE
MIDDLE TO UPPER 30S...HOWEVER LOWER 30S (NEAR FREEZING?) WILL BE
POSSIBLE ACROSS THE ABOVE MENTIONED LOCATIONS.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AN ACTIVE SHORT TERM PERIOD CONTINUES TO TAKE SHAPE THIS AFTERNOON
AS MAIN PACIFIC UPPER TROUGH OF INTEREST CONTINUES TO DIVE SOUTH
ALONG THE CALIFORNIA COAST THIS AFTERNOON. FCST MODELS REMAIN IN
EXCELLENT AGREEMENT IN CLOSING THIS FEATURE OFF TONIGHT BEFORE
SLOWLY TRACKING IT EAST THROUGH THE DESERT SOUTHWEST...NORTHERN
MEXICO...AND EVENTUALLY THE SOUTHERN PLAINS. AS MAIN FEATURE WORKS
EAST...CYCLOGENESIS WILL OCCUR ACROSS SOUTHERN TEXAS EARLY
SATURDAY...WITH THIS FEATURE THEN EXPECTED TO RAPIDLY LIFT
NORTHEAST ALONG A STALLED FRONTAL BOUNDARY DRAPED FROM THE MID-
MISSISSIPPI VLY NORTH THROUGH THE NORTHEAST TO INCLUDE OUR FCST
AREA.
IN TERMS OF SENSIBLE WX...EXPECT INCREASING CHANCES FOR RAIN BY
FRIDAY AFTERNOON/EVENING AS AN INITIAL AREA AREA OF LOW PRESSURE
APPROACHES FROM THE SOUTHWEST. WITH MAIN FRONTAL BOUNDARY EXPECTED
TO SLOWLY LIFT NORTH OF OUR FCST REGION DURING THIS PERIOD...BEST
CHANCES FOR PRECIP WILL REMAIN FROM THE FINGER LAKES NORTHEAST
THROUGH THE SOUTHERN TUG HILL. WITH BEST FRONTOGENESIS REMAINING
WELL NORTH...COMBINED WITH THE FACT THAT NO SIGNIFICANT SHORTWAVES
ARE APPARENT IN ANY MODEL GUIDANCE...FIND IT HARD PRESSED AT THIS
POINT TO MENTION ANYTHING HIGHER THAN MID/HIGH-CHC POPS. BY FRIDAY
NIGHT...HAVE INCREASED POPS INTO THE LOW LIKELY CATEGORY ACROSS
THE NORTH AS THE INITIAL SFC LOW PASSES. TEMPS DURING THE
OVERNIGHT WILL SURELY REMAIN ABOVE FREEZING THUS NO MIXED PRECIP
IMPACTS EXPECTED AT THIS TIME.
BIG CONCERNS BECOME READILY APPARENT BY SATURDAY AS MAIN SFC LOW
ASSOCIATED WITH THE AFOREMENTIONED PACIFIC UPPER LOW BEGINS LIFTING
NORTH THROUGH THE MISSISSIPPI AND OHIO RVR VLYS. OUT AHEAD OF THIS
FEATURE...EXPECT PLENTY OF MOISTURE ADVECTION NORTH FROM THE GULF
OF MEXICO AS 850-HPA WINDS INCREASE TO NEAR 80S KTS (3-4 STANDARD
DEVIATIONS ABOVE NORMAL) AND PWAT VALUES RAPIDLY INCREASE TO
ALMOST 1.50" (ALSO 3-4 STANDARD DEVIATIONS ABOVE NORMAL). STRONG
SOUTHERLY FLOW WILL ALLOW LINGERING FRONTAL BOUNDARY TO LIFT WELL
NORTH OF OUR FCST REGION AS MAIN SFC LOW LIFTS FROM THE CENTRAL
GREAT LAKES NORTHEAST TO WESTERN QUEBEC BY 00Z MONDAY. THIS SHOULD
ALLOW TEMPERATURES TO WARM WELL INTO THE 50S ACROSS MOST LOCATIONS
WHICH WILL RESULT IN A SUBSTANTIAL MELTING OF THE EXISTING
SNOWPACK. THIS FACT COMBINED WITH WHAT MAY BE A PRETTY DECENT SHOT
OF RAIN SATURDAY NIGHT/EARLY SUNDAY WILL LIKELY LEAD TO RISES ON
AREA RIVERS AND STREAMS. 48-HR QPF FCSTS FROM SEVERAL MODELS NOW
TRENDING FURTHER AND FURTHER NORTHWEST WITH MAX RAINFALL (I.E. FAR
WESTERN NY WEST THROUGH SOUTH-CENTRAL CANADA). THE GFS REMAINS THE
OUTLIER WITH THE MAX (2-3") FURTHER EAST ACROSS PORTIONS OF OUR
AREA. CONSIDERING THE CURRENT DISAGREEMENT IN OPERATIONAL MODEL
SOLUTIONS...WILL NOT GET TOO EXCITED WITH RESPECT TO FLOOD
POTENTIAL BUT WILL CONTINUE TO HIGHLIGHT CONCERNS IN THE HWO BASED
ON LIMITED CONFIDENCE OF MAX RAINFALL OCCURRING ACROSS OUR AREA.
MODERATE RAIN POTENTIAL TO COME TO AN END LATE IN THE DAY ON
SUNDAY AS FIRST COLD FRONT PASSES THROUGH THE AREA. EVEN COOLER
AIR WILL MOVE INTO THE AREA SUNDAY NIGHT AS SECONDARY FRONT PASSES
OVERNIGHT MARKING THE BEGINNINGS OF A RETURN TO REALTY JUST IN
TIME FOR THE HOLIDAYS.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
PD BEGINS WITH A NLY FLOW OF CAA AT THE SFC WITH STILL A SW FLOW
ALOFT. THIS VERY SHEARED PTRN AND SHRT FETCH OFF THE LAKES SHD
LIMIT THE LE DESPITE H8 TEMPS DROPPING TO -12C LATE IN THE DAY MON.
TROF BOTTOMS OUT OVER THE FCST AREA TUES INCRSG THE CHANCE QPF LE
SNOW SHWRS AND CONTG TO LWR THE TEMPS. SFC HI SLIDES EAST ON WED
AND RETURNS SOME WAA. ANY OVERRUNNING PCPN SHD STAY WELL NORTH AND
WEST OF THE AREA THRU THE END OF THE PD WITH THE UPR LOW AND
DEEPER MOISTURE MVG THRU THE WRN LAKES AND INTO CANADA EARLY THU.
GNRLY FLWD HPC GUID FOR TEMPS THRU THE PD...BUT ADJUSTED POPS
UPWARDS FOR LGT LE GIVEN THE INSTABILITY AND UPR TROF.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
HAVE OPTED TO PULL BACK ON THE MVFR OVERNIGHT. THE RAP AND LOCAL
WRF ARE INSISTENT THAT WE WILL GET A DRY AIR INTRUSION THROUGH THE
LOWER ATMOSPHERE, BREAKING UP THE POTENTIAL LOW CLOUDS ESPECIALLY
OVER THE SOUTHERN TERMINALS. TEMPO MVFR CONDITIONS ARE FORECAST
FOR SHORT WINDOWS AT BGM, ITH, AND SYR.
THE BEST CHANCE FOR LOW MVFR WILL BE AT RME. WE ARE FORECASTING
THEIR CEILING TO DEGRADE QUICKLY BETWEEN 1Z AND 4Z, AND SETTLE
AROUND 1500 FEET FOR THE OVERNIGHT HOURS. THERE IS ALSO THE
POSSIBILITY FOR SOME FREEZING DRIZZLE AT RME LATE OVERNIGHT, AS A
SATURATED ISOTHERMAL SOUNDING IN A WEAK LIFT ENVIRONMENT IS
FORECAST WITH A SURFACE TEMPERATURE AROUND 30.
OUTLOOK...
FRI NGT THROUGH SUN...RESTRICTIONS POSSIBLE IN RAIN SHOWERS.
PERHAPS INITIALLY A LIGHT WINTRY MIX EARLY FRI MRNG IN NORTH CENTRAL
NY.
SUN NGT-MON...RESTRICTIONS POSSIBLE FROM RAIN AND/OR SNOW.
TUE...VFR WITH ISLTD MVFR IN SNOW SHWRS EARLY.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NY...NONE.
&&
$$
SYNOPSIS...CMG/MDP
NEAR TERM...CMG/MDP
SHORT TERM...CMG
LONG TERM...DGM
AVIATION...DJP
AREA FORECAST DISCUSSION
NWS BINGHAMTON NY
634 PM EST THU DEC 19 2013
.SYNOPSIS...
LIGHT RAIN AND DRIZZLE WILL BE POSSIBLE ACROSS PORTIONS OF CENTRAL
NEW YORK TONIGHT AS A WARM FRONT LIFTS NORTH TOWARDS THE
AREA...WHILE NORTHEAST PENNSYLVANIA STAYS DRY OVERNIGHT.
FOLLOWING THIS...UNSEASONABLY MILD AIR WILL RETURN TO THE REGION
AS SOUTHERLY FLOW INCREASES AND A FRONTAL BOUNDARY STALLS JUST
NORTH OF OUR AREA. RAIN CHANCES WILL BE ON THE INCREASE HEADING
INTO THE WEEKEND AS A SERIES OF LOW PRESSURE SYSTEMS TRACK NORTH
ALONG THE STALLED FRONT. COOLER AIR IS THEN EXPECTED EARLY NEXT
WEEK FOLLOWING THE PASSAGE OF A STRONG COLD FRONT SUNDAY NIGHT.
&&
.NEAR TERM /THROUGH FRIDAY/...
630 PM UPDATE...
BASED ON LATEST MODEL TRENDS WAS ABLE TO DELAY AND PARE BACK
AMOUNT OF PATCHY DRIZZLE/CHANCES OF LIGHT RAIN INTO LATER
TONIGHT-FRIDAY MORNING AND MAINLY JUST FINGER LAKES THROUGH MOHAWK
VALLEY REGIONS WITH BEST CHANCES NORTH OF NY THRUWAY. TEMPERATURE
GUIDANCE AND SOUNDINGS ALSO SUGGEST THAT FREEZING DRIZZLE/SPOTTY
LIGHT FREEZING RAIN POSSIBILITY WILL PROBABLY BE LIMITED TO HIGHER
ELEVATIONS OF NORTHERN ONEIDA COUNTY...AND EVEN THAT IS IFFY
BECAUSE OF STEADY TO SLOWLY RISING TREND IN TEMPERATURES AFTER
MIDNIGHT ACROSS MOST OF CENTRAL NEW YORK. FORECAST DETAILS
ADJUSTED ACCORDINGLY.
PREVIOUS DISCUSSION...
AFTERNOON VISIBLE SATELLITE IMAGERY SHOWING PARTLY CLOUDY SKIES
ACROSS MUCH OF OUR REGION...WITH MORE PRONOUNCED CLOUD COVER NOTED
OFF TO OUR WEST IN ADVANCE OF A WARM FRONT LIFTING NORTH THROUGH
THE LWR OHIO VLY. AS A RESULT OF THE SOLAR INSULATION
TODAY...TEMPERATURES HAVE WARMED NICELY ACROSS THE REGION WITH
MOST AREAS REPORTING VALUES IN THE UPPER 30S TO LWR 40S. MAIN
CONCERN HEADING INTO THE OVERNIGHT PERIOD REMAINS FOCUSED ON THE
AFOREMENTIONED FRONTAL BOUNDARY AND THE POSSIBILITY FOR DEVELOPING
LIGHT RAIN/DRIZZLE AND EVEN SOME SPOTTY FREEZING DRIZZLE ACROSS
PORTIONS OF CENTRAL NEW YORK AND NORTHEAST PA AFTER MIDNIGHT.
FROM THIS VANTAGE POINT...BEST ISENTROPIC ASCENT ALONG THE 285
AND 290K THETA-E SURFACES REMAINS WELL NORTH AND WEST OF THE FCST
REGION AS STRONGEST SOUTHERLY FLOW REMAINS ACROSS THE OHIO VLY.
IN ADDITION TO THIS...WARM AIR ADVECTION TO CONTINUE THROUGH THE
OVERNIGHT WHICH COMBINED WITH INCREASING CLOUD COVER SHOULD KEEP
TEMPS FROM FALLING TOO MUCH WITH LOSS OF DAYTIME HEATING. AS A
RESULT...HAVE ELECTED TO FURTHER TRIM BACK ON INHERITED FZRA/FZDZ
MENTION WITH MAIN AREAS NOW HIGHLIGHT ACROSS THE SOUTHERN TUG
HILL...WESTERN CATSKILLS...AND THE CENTRAL SOUTHERN TIER WHERE
ENOUGH COOLING MAY OCCUR IN THE VALLEY LOCATIONS TO ALLOW TEMPS
TO APPROACH FREEZING FOR A SHORT TIME. DESPITE THIS...OVERALL
FZRA/FZDZ THREAT APPEARS FAIRLY LIMITED BASED ON PROJECTED TEMP
TRENDS AND WILL HOLD-OFF ON ANY HEADLINES AS ACTIVITY SHOULD
REMAIN FAIRLY ISOLATED.
AS STATED ABOVE...EXPECT TEMPS TO SLOWLY DECREASE AFTER SUNSET
BEFORE HOLDING STEADY AND MAYBE RISING TOWARDS MORNING AS WARM AIR
ADVECTION INCREASES. OVERNIGHT LOWS WILL LIKELY BOTTOM OUT IN THE
MIDDLE TO UPPER 30S...HOWEVER LOWER 30S (NEAR FREEZING?) WILL BE
POSSIBLE ACROSS THE ABOVE MENTIONED LOCATIONS.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AN ACTIVE SHORT TERM PERIOD CONTINUES TO TAKE SHAPE THIS AFTERNOON
AS MAIN PACIFIC UPPER TROUGH OF INTEREST CONTINUES TO DIVE SOUTH
ALONG THE CALIFORNIA COAST THIS AFTERNOON. FCST MODELS REMAIN IN
EXCELLENT AGREEMENT IN CLOSING THIS FEATURE OFF TONIGHT BEFORE
SLOWLY TRACKING IT EAST THROUGH THE DESERT SOUTHWEST...NORTHERN
MEXICO...AND EVENTUALLY THE SOUTHERN PLAINS. AS MAIN FEATURE WORKS
EAST...CYCLOGENESIS WILL OCCUR ACROSS SOUTHERN TEXAS EARLY
SATURDAY...WITH THIS FEATURE THEN EXPECTED TO RAPIDLY LIFT
NORTHEAST ALONG A STALLED FRONTAL BOUNDARY DRAPED FROM THE MID-
MISSISSIPPI VLY NORTH THROUGH THE NORTHEAST TO INCLUDE OUR FCST
AREA.
IN TERMS OF SENSIBLE WX...EXPECT INCREASING CHANCES FOR RAIN BY
FRIDAY AFTERNOON/EVENING AS AN INITIAL AREA AREA OF LOW PRESSURE
APPROACHES FROM THE SOUTHWEST. WITH MAIN FRONTAL BOUNDARY EXPECTED
TO SLOWLY LIFT NORTH OF OUR FCST REGION DURING THIS PERIOD...BEST
CHANCES FOR PRECIP WILL REMAIN FROM THE FINGER LAKES NORTHEAST
THROUGH THE SOUTHERN TUG HILL. WITH BEST FRONTOGENESIS REMAINING
WELL NORTH...COMBINED WITH THE FACT THAT NO SIGNIFICANT SHORTWAVES
ARE APPARENT IN ANY MODEL GUIDANCE...FIND IT HARD PRESSED AT THIS
POINT TO MENTION ANYTHING HIGHER THAN MID/HIGH-CHC POPS. BY FRIDAY
NIGHT...HAVE INCREASED POPS INTO THE LOW LIKELY CATEGORY ACROSS
THE NORTH AS THE INITIAL SFC LOW PASSES. TEMPS DURING THE
OVERNIGHT WILL SURELY REMAIN ABOVE FREEZING THUS NO MIXED PRECIP
IMPACTS EXPECTED AT THIS TIME.
BIG CONCERNS BECOME READILY APPARENT BY SATURDAY AS MAIN SFC LOW
ASSOCIATED WITH THE AFOREMENTIONED PACIFIC UPPER LOW BEGINS LIFTING
NORTH THROUGH THE MISSISSIPPI AND OHIO RVR VLYS. OUT AHEAD OF THIS
FEATURE...EXPECT PLENTY OF MOISTURE ADVECTION NORTH FROM THE GULF
OF MEXICO AS 850-HPA WINDS INCREASE TO NEAR 80S KTS (3-4 STANDARD
DEVIATIONS ABOVE NORMAL) AND PWAT VALUES RAPIDLY INCREASE TO
ALMOST 1.50" (ALSO 3-4 STANDARD DEVIATIONS ABOVE NORMAL). STRONG
SOUTHERLY FLOW WILL ALLOW LINGERING FRONTAL BOUNDARY TO LIFT WELL
NORTH OF OUR FCST REGION AS MAIN SFC LOW LIFTS FROM THE CENTRAL
GREAT LAKES NORTHEAST TO WESTERN QUEBEC BY 00Z MONDAY. THIS SHOULD
ALLOW TEMPERATURES TO WARM WELL INTO THE 50S ACROSS MOST LOCATIONS
WHICH WILL RESULT IN A SUBSTANTIAL MELTING OF THE EXISTING
SNOWPACK. THIS FACT COMBINED WITH WHAT MAY BE A PRETTY DECENT SHOT
OF RAIN SATURDAY NIGHT/EARLY SUNDAY WILL LIKELY LEAD TO RISES ON
AREA RIVERS AND STREAMS. 48-HR QPF FCSTS FROM SEVERAL MODELS NOW
TRENDING FURTHER AND FURTHER NORTHWEST WITH MAX RAINFALL (I.E. FAR
WESTERN NY WEST THROUGH SOUTH-CENTRAL CANADA). THE GFS REMAINS THE
OUTLIER WITH THE MAX (2-3") FURTHER EAST ACROSS PORTIONS OF OUR
AREA. CONSIDERING THE CURRENT DISAGREEMENT IN OPERATIONAL MODEL
SOLUTIONS...WILL NOT GET TOO EXCITED WITH RESPECT TO FLOOD
POTENTIAL BUT WILL CONTINUE TO HIGHLIGHT CONCERNS IN THE HWO BASED
ON LIMITED CONFIDENCE OF MAX RAINFALL OCCURRING ACROSS OUR AREA.
MODERATE RAIN POTENTIAL TO COME TO AN END LATE IN THE DAY ON
SUNDAY AS FIRST COLD FRONT PASSES THROUGH THE AREA. EVEN COOLER
AIR WILL MOVE INTO THE AREA SUNDAY NIGHT AS SECONDARY FRONT PASSES
OVERNIGHT MARKING THE BEGINNINGS OF A RETURN TO REALTY JUST IN
TIME FOR THE HOLIDAYS.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
PD BEGINS WITH A NLY FLOW OF CAA AT THE SFC WITH STILL A SW FLOW
ALOFT. THIS VERY SHEARED PTRN AND SHRT FETCH OFF THE LAKES SHD
LIMIT THE LE DESPITE H8 TEMPS DROPPING TO -12C LATE IN THE DAY MON.
TROF BOTTOMS OUT OVER THE FCST AREA TUES INCRSG THE CHANCE QPF LE
SNOW SHWRS AND CONTG TO LWR THE TEMPS. SFC HI SLIDES EAST ON WED
AND RETURNS SOME WAA. ANY OVERRUNNING PCPN SHD STAY WELL NORTH AND
WEST OF THE AREA THRU THE END OF THE PD WITH THE UPR LOW AND
DEEPER MOISTURE MVG THRU THE WRN LAKES AND INTO CANADA EARLY THU.
GNRLY FLWD HPC GUID FOR TEMPS THRU THE PD...BUT ADJUSTED POPS
UPWARDS FOR LGT LE GIVEN THE INSTABILITY AND UPR TROF.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
HAVE OPTED TO PULL BACK ON THE MVFR OVERNIGHT. THE RAP AND LOCAL
WRF ARE INSISTENT THAT WE WILL GET A DRY AIR INTRUSION THROUGH THE
LOWER ATMOSPHERE, BREAKING UP THE POTENTIAL LOW CLOUDS ESPECIALLY
OVER THE SOUTHERN TERMINALS. TEMPO MVFR CONDITIONS ARE FORECAST
FOR SHORT WINDOWS AT BGM, ITH, AND SYR.
THE BEST CHANCE FOR LOW MVFR WILL BE AT RME. WE ARE FORECASTING
THEIR CEILING TO DEGRADE QUICKLY BETWEEN 1Z AND 4Z, AND SETTLE
AROUND 1500 FEET FOR THE OVERNIGHT HOURS. THERE IS ALSO THE
POSSIBILITY FOR SOME FREEZING DRIZZLE AT RME LATE OVERNIGHT, AS A
SATURATED ISOTHERMAL SOUNDING IN A WEAK LIFT ENVIRONMENT IS
FORECAST WITH A SURFACE TEMPERATURE AROUND 30.
OUTLOOK...
FRI NGT THROUGH SUN...RESTRICTIONS POSSIBLE IN RAIN SHOWERS.
PERHAPS INITIALLY A LIGHT WINTRY MIX EARLY FRI MRNG IN NORTH CENTRAL
NY.
SUN NGT-MON...RESTRICTIONS POSSIBLE FROM RAIN AND/OR SNOW.
TUE...VFR WITH ISLTD MVFR IN SNOW SHWRS EARLY.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NY...NONE.
&&
$$
SYNOPSIS...CMG
NEAR TERM...CMG/MDP
SHORT TERM...CMG
LONG TERM...DGM
AVIATION...DJP
AREA FORECAST DISCUSSION
NWS BINGHAMTON NY
609 PM EST THU DEC 19 2013
.SYNOPSIS...
LIGHT RAIN AND DRIZZLE WILL BE POSSIBLE ACROSS PORTIONS OF CENTRAL
NEW YORK AND THE NORTHERN TIER OF PENNSYLVANIA TONIGHT AS A WARM
FRONT LIFTS NORTH TOWARDS THE AREA. FOLLOWING THIS...UNSEASONABLY
MILD AIR WILL RETURN TO THE REGION AS SOUTHERLY FLOW INCREASES AND A
FRONTAL BOUNDARY STALLS JUST NORTH OF OUR AREA. RAIN CHANCES WILL
BE ON THE INCREASE HEADING INTO THE WEEKEND AS A SERIES OF LOW
PRESSURE SYSTEMS TRACK NORTH ALONG THE STALLED FRONT. COOLER AIR
IS THEN EXPECTED EARLY NEXT WEEK FOLLOWING THE PASSAGE OF A
STRONG COLD FRONT SUNDAY NIGHT.
&&
.NEAR TERM /THROUGH FRIDAY/...
AFTERNOON VISIBLE SATELLITE IMAGERY SHOWING PARTLY CLOUDY SKIES
ACROSS MUCH OF OUR REGION...WITH MORE PRONOUNCED CLOUD COVER NOTED
OFF TO OUR WEST IN ADVANCE OF A WARM FRONT LIFTING NORTH THROUGH
THE LWR OHIO VLY. AS A RESULT OF THE SOLAR INSULATION
TODAY...TEMPERATURES HAVE WARMED NICELY ACROSS THE REGION WITH
MOST AREAS REPORTING VALUES IN THE UPPER 30S TO LWR 40S. MAIN
CONCERN HEADING INTO THE OVERNIGHT PERIOD REMAINS FOCUSED ON THE
AFOREMENTIONED FRONTAL BOUNDARY AND THE POSSIBILITY FOR DEVELOPING
LIGHT RAIN/DRIZZLE AND EVEN SOME SPOTTY FREEZING DRIZZLE ACROSS
PORTIONS OF CENTRAL NEW YORK AND NORTHEAST PA AFTER MIDNIGHT.
FROM THIS VANTAGE POINT...BEST ISENTROPIC ASCENT ALONG THE 285
AND 290K THETA-E SURFACES REMAINS WELL NORTH AND WEST OF THE FCST
REGION AS STRONGEST SOUTHERLY FLOW REMAINS ACROSS THE OHIO VLY.
IN ADDITION TO THIS...WARM AIR ADVECTION TO CONTINUE THROUGH THE
OVERNIGHT WHICH COMBINED WITH INCREASING CLOUD COVER SHOULD KEEP
TEMPS FROM FALLING TOO MUCH WITH LOSS OF DAYTIME HEATING. AS A
RESULT...HAVE ELECTED TO FURTHER TRIM BACK ON INHERITED FZRA/FZDZ
MENTION WITH MAIN AREAS NOW HIGHLIGHT ACROSS THE SOUTHERN TUG
HILL...WESTERN CATSKILLS...AND THE CENTRAL SOUTHERN TIER WHERE
ENOUGH COOLING MAY OCCUR IN THE VALLEY LOCATIONS TO ALLOW TEMPS
TO APPROACH FREEZING FOR A SHORT TIME. DESPITE THIS...OVERALL
FZRA/FZDZ THREAT APPEARS FAIRLY LIMITED BASED ON PROJECTED TEMP
TRENDS AND WILL HOLD-OFF ON ANY HEADLINES AS ACTIVITY SHOULD
REMAIN FAIRLY ISOLATED.
AS STATED ABOVE...EXPECT TEMPS TO SLOWLY DECREASE AFTER SUNSET
BEFORE HOLDING STEADY AND MAYBE RISING TOWARDS MORNING AS WARM AIR
ADVECTION INCREASES. OVERNIGHT LOWS WILL LIKELY BOTTOM OUT IN THE
MIDDLE TO UPPER 30S...HOWEVER LOWER 30S (NEAR FREEZING?) WILL BE
POSSIBLE ACROSS THE ABOVE MENTIONED LOCATIONS.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AN ACTIVE SHORT TERM PERIOD CONTINUES TO TAKE SHAPE THIS AFTERNOON
AS MAIN PACIFIC UPPER TROUGH OF INTEREST CONTINUES TO DIVE SOUTH
ALONG THE CALIFORNIA COAST THIS AFTERNOON. FCST MODELS REMAIN IN
EXCELLENT AGREEMENT IN CLOSING THIS FEATURE OFF TONIGHT BEFORE
SLOWLY TRACKING IT EAST THROUGH THE DESERT SOUTHWEST...NORTHERN
MEXICO...AND EVENTUALLY THE SOUTHERN PLAINS. AS MAIN FEATURE WORKS
EAST...CYCLOGENESIS WILL OCCUR ACROSS SOUTHERN TEXAS EARLY
SATURDAY...WITH THIS FEATURE THEN EXPECTED TO RAPIDLY LIFT
NORTHEAST ALONG A STALLED FRONTAL BOUNDARY DRAPED FROM THE MID-
MISSISSIPPI VLY NORTH THROUGH THE NORTHEAST TO INCLUDE OUR FCST
AREA.
IN TERMS OF SENSIBLE WX...EXPECT INCREASING CHANCES FOR RAIN BY
FRIDAY AFTERNOON/EVENING AS AN INITIAL AREA AREA OF LOW PRESSURE
APPROACHES FROM THE SOUTHWEST. WITH MAIN FRONTAL BOUNDARY EXPECTED
TO SLOWLY LIFT NORTH OF OUR FCST REGION DURING THIS PERIOD...BEST
CHANCES FOR PRECIP WILL REMAIN FROM THE FINGER LAKES NORTHEAST
THROUGH THE SOUTHERN TUG HILL. WITH BEST FRONTOGENESIS REMAINING
WELL NORTH...COMBINED WITH THE FACT THAT NO SIGNIFICANT SHORTWAVES
ARE APPARENT IN ANY MODEL GUIDANCE...FIND IT HARD PRESSED AT THIS
POINT TO MENTION ANYTHING HIGHER THAN MID/HIGH-CHC POPS. BY FRIDAY
NIGHT...HAVE INCREASED POPS INTO THE LOW LIKELY CATEGORY ACROSS
THE NORTH AS THE INITIAL SFC LOW PASSES. TEMPS DURING THE
OVERNIGHT WILL SURELY REMAIN ABOVE FREEZING THUS NO MIXED PRECIP
IMPACTS EXPECTED AT THIS TIME.
BIG CONCERNS BECOME READILY APPARENT BY SATURDAY AS MAIN SFC LOW
ASSOCIATED WITH THE AFOREMENTIONED PACIFIC UPPER LOW BEGINS LIFTING
NORTH THROUGH THE MISSISSIPPI AND OHIO RVR VLYS. OUT AHEAD OF THIS
FEATURE...EXPECT PLENTY OF MOISTURE ADVECTION NORTH FROM THE GULF
OF MEXICO AS 850-HPA WINDS INCREASE TO NEAR 80S KTS (3-4 STANDARD
DEVIATIONS ABOVE NORMAL) AND PWAT VALUES RAPIDLY INCREASE TO
ALMOST 1.50" (ALSO 3-4 STANDARD DEVIATIONS ABOVE NORMAL). STRONG
SOUTHERLY FLOW WILL ALLOW LINGERING FRONTAL BOUNDARY TO LIFT WELL
NORTH OF OUR FCST REGION AS MAIN SFC LOW LIFTS FROM THE CENTRAL
GREAT LAKES NORTHEAST TO WESTERN QUEBEC BY 00Z MONDAY. THIS SHOULD
ALLOW TEMPERATURES TO WARM WELL INTO THE 50S ACROSS MOST LOCATIONS
WHICH WILL RESULT IN A SUBSTANTIAL MELTING OF THE EXISTING
SNOWPACK. THIS FACT COMBINED WITH WHAT MAY BE A PRETTY DECENT SHOT
OF RAIN SATURDAY NIGHT/EARLY SUNDAY WILL LIKELY LEAD TO RISES ON
AREA RIVERS AND STREAMS. 48-HR QPF FCSTS FROM SEVERAL MODELS NOW
TRENDING FURTHER AND FURTHER NORTHWEST WITH MAX RAINFALL (I.E. FAR
WESTERN NY WEST THROUGH SOUTH-CENTRAL CANADA). THE GFS REMAINS THE
OUTLIER WITH THE MAX (2-3") FURTHER EAST ACROSS PORTIONS OF OUR
AREA. CONSIDERING THE CURRENT DISAGREEMENT IN OPERATIONAL MODEL
SOLUTIONS...WILL NOT GET TOO EXCITED WITH RESPECT TO FLOOD
POTENTIAL BUT WILL CONTINUE TO HIGHLIGHT CONCERNS IN THE HWO BASED
ON LIMITED CONFIDENCE OF MAX RAINFALL OCCURRING ACROSS OUR AREA.
MODERATE RAIN POTENTIAL TO COME TO AN END LATE IN THE DAY ON
SUNDAY AS FIRST COLD FRONT PASSES THROUGH THE AREA. EVEN COOLER
AIR WILL MOVE INTO THE AREA SUNDAY NIGHT AS SECONDARY FRONT PASSES
OVERNIGHT MARKING THE BEGINNINGS OF A RETURN TO REALTY JUST IN
TIME FOR THE HOLIDAYS.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
PD BEGINS WITH A NLY FLOW OF CAA AT THE SFC WITH STILL A SW FLOW
ALOFT. THIS VERY SHEARED PTRN AND SHRT FETCH OFF THE LAKES SHD
LIMIT THE LE DESPITE H8 TEMPS DROPPING TO -12C LATE IN THE DAY MON.
TROF BOTTOMS OUT OVER THE FCST AREA TUES INCRSG THE CHANCE QPF LE
SNOW SHWRS AND CONTG TO LWR THE TEMPS. SFC HI SLIDES EAST ON WED
AND RETURNS SOME WAA. ANY OVERRUNNING PCPN SHD STAY WELL NORTH AND
WEST OF THE AREA THRU THE END OF THE PD WITH THE UPR LOW AND
DEEPER MOISTURE MVG THRU THE WRN LAKES AND INTO CANADA EARLY THU.
GNRLY FLWD HPC GUID FOR TEMPS THRU THE PD...BUT ADJUSTED POPS
UPWARDS FOR LGT LE GIVEN THE INSTABILITY AND UPR TROF.
&&
.AVIATION /23Z THURSDAY THROUGH TUESDAY/...
HAVE OPTED TO PULL BACK ON THE MVFR OVERNIGHT. THE RAP AND LOCAL
WRF ARE INSISTENT THAT WE WILL GET A DRY AIR INTRUSION THROUGH THE
LOWER ATMOSPHERE, BREAKING UP THE POTENTIAL LOW CLOUDS ESPECIALLY
OVER THE SOUTHERN TERMINALS. TEMPO MVFR CONDITIONS ARE FORECAST
FOR SHORT WINDOWS AT BGM, ITH, AND SYR.
THE BEST CHANCE FOR LOW MVFR WILL BE AT RME. WE ARE FORECASTING
THEIR CEILING TO DEGRADE QUICKLY BETWEEN 1Z AND 4Z, AND SETTLE
AROUND 1500 FEET FOR THE OVERNIGHT HOURS. THERE IS ALSO THE
POSSIBILITY FOR SOME FREEZING DRIZZLE AT RME LATE OVERNIGHT, AS A
SATURATED ISOTHERMAL SOUNDING IN A WEAK LIFT ENVIRONMENT IS
FORECAST WITH A SURFACE TEMPERATURE AROUND 30.
OUTLOOK...
FRI NGT THROUGH SUN...RESTRICTIONS POSSIBLE IN RAIN SHOWERS.
PERHAPS INITIALLY A LIGHT WINTRY MIX EARLY FRI MRNG IN NORTH CENTRAL
NY.
SUN NGT-MON...RESTRICTIONS POSSIBLE FROM RAIN AND/OR SNOW.
TUE...VFR WITH ISLTD MVFR IN SNOW SHWRS EARLY.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NY...NONE.
&&
$$
SYNOPSIS...CMG
NEAR TERM...CMG
SHORT TERM...CMG
LONG TERM...DGM
AVIATION...DJP
AREA FORECAST DISCUSSION
NWS RALEIGH NC
940 PM EST THU DEC 19 2013
.SYNOPSIS...SOUTH SOUTHWEST FLOW AROUND BERMUDA HIGH PRESSURE WILL
RESULT IN WARMING CONDITIONS THROUGH SUNDAY...FOLLOWED BY THE
PASSAGE OF A COLD FRONT SUNDAY NIGHT AND MONDAY.
&&
.NEAR TERM /TONIGHT/...
AS OF 940 PM THURSDAY...
THE SURFACE HIGH IS NOW WELL OFF OF THE NC COAST THIS EVENING...WITH
A LIGHT SOUTH-SOUTHWESTERLY WIND AT MOST OBSERVING SITES.
ALOFT...CIRRUS CONTINUES TO SPREAD EAST ACROSS THE REGION...THOUGH
THERE IS CURRENTLY A PATCH OF CLEARING ACROSS THE SOUTHERN PIEDMONT.
THE CIRRUS IS MAKING THE LOW TEMP FORECAST A LITTLE TRICKY..WITH
HIGHLY VARIABLE OBSERVED TEMPS RANGING FROM THE UPPER 30S TO LOWER
50S. WITH MORE CIRRUS IMMEDIATELY UPSTREAM OVER THE TN
VALLEY...TEMPS SHOULD BE VERY SLOW TO FALL FOR THE REMAINDER OF THE
NIGHT. MOST GUIDANCE SEEMS TOO LOW OVERALL BASED ON CURRENT
TRENDS...SO HAVE MADE SOME ADJUSTMENTS TO TRY TO CAPTURE WARMER
READINGS NORTH AND WEST WHERE CIRRUS SHOULD MOST PREVALENT. THE
CIRRUS MAY ALSO LIMIT STRATUS DEVELOPMENT IN THE WEAK RETURN FLOW
THAT HAS DEVELOPED. THE RAP IS MOST AGGRESSIVE WITH THE STRATUS BUT
APPEARS TO HAVE TRENDED LATER AND MORE PATCHY....FOCUSED MOSTLY
ACROSS THE SOUTHERN COASTAL PLAIN. LOWS 37-44.
&&
.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
AS OF 225 PM THURSDAY...
THE MAIN WEATHER PLAYERS FOR FRIDAY WILL BE THE LONG WAVE TROUGH
MOVING ACROSS THE ROCKIES AND SW STATES...AND A LENGTHY DRAWN-OUT
SFC FRONTAL SYSTEM THAT IS EXPECTED TO EXTEND FROM THE NEW ENGLAND
STATES...SOUTHWEST ACROSS THE MIDWEST...AND SOUTH ACROSS TEXAS.
ACROSS OUR AREA HOWEVER...HIGH PRESSURE CENTERED OVER THE WRN
ATLANTIC WILL CONTINUE TO INFLUENCE OUR WEATHER...PROVIDING FAIR
WEATHER AND WARMER TEMPERATURES AS LOW LEVEL SW FLOW CONTINUES TO
ADVECT WARMER AIR AND ADDITIONAL MOISTURE INTO OUR AREA. AS SUCH...
LOOK FOR PARTIAL SUNSHINE THROUGH A VEIL OF HIGH CLOUDS (AFTER ANY
MORNING LOW CLOUDS AND FOG BURN OFF)...BUT THE MAIN WEATHER STORY
WILL BE THE WARMER TEMPS...AS INCREASING LOW LEVEL THICKNESS VALUES
AND BL WARMING PER LATEST FORECAST SOUNDINGS SUGGEST EARLY-
SPRING-LIKE HIGHS IN THE MID-UPPER 60S.
WITH LITTLE CHANGE IN THE PATTERN FRIDAY NIGHT...LOOK FOR ADDITIONAL
PATCHY LOW CLOUDS AND FOG TO FORM TOWARD SUNRISE SATURDAY...AND LOW
TEMPS 15+ DEGREES ABOVE NORMAL...UPR 40S TO AROUND 50.
STRONG WARM AIR AND MOISTURE ADVECTION WILL CONTINUE AHEAD OF AN
APPROACHING COLD FRONT ON SATURDAY. HIGH CLOUDINESS WILL BE
WIDESPREAD...BUT EVEN MILKY SUN WILL ALLOW HIGHS TO SOAR INTO THE
UPPER 60S TO MID 70S WHICH SHOULD ECLIPSE RECORD HIGHS FOR THE 21ST
FOR RDU AND GSO...LISTED BELOW. AS THE FRONT CREEPS UP TO THE
WESTERN SLOPES...SCATTERED SHOWERS ARE EXPECTED IN THE WESTERN
PIEDMONT LATER SATURDAY NIGHT. ONGOING WARM FLOW AND CLOUD COVERAGE
WILL PRODUCE A VERY MILD NIGHT...WITH LOWS IN THE UPPER 50S TO
PERHAPS EVEN LOW 60S...WHICH ARE HIGHER THAN CLIMATOLOGICAL MAX
TEMPS FOR THE DATE.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 255 PM THURSDAY...
UPPER SHORT WAVE IS WELL OFF TO THE NORTHWEST OVER THE UPPER MID
WEST AND THE FRONT WILL BE STRETCHED/SHEARED MORE PARALLEL TO THE
MID AND UPPER FLOW...SO THERE IS NOT INITIALLY STRONG DRIVING FORCES
TO PROPEL THE FRONT EAST. THE LATEST GFS HAS NONETHELESS SPED UP
EASTWARD PROGRESSION ACROSS THE AREA LATE SUNDAY. WILL MAINTAIN A
SLOWER ECMWF TIMING...WITH LIKELY POPS IN THE FAR WESTERN PIEDMONT
LATE IN THE DAY...AND ONLY SMALL CHANCES IN THE EAST. THERE WILL BE
A STRONG LOW LEVEL JET (EXCEEDING 50KT AT H92-H85) WITH DIFFLUENT
FLOW ALOFT...SO ISOLATED THUNDER WILL BE MAINTAINED DESPITE WEAK
INSTABILITY. HIGHS WILL AGAIN APPROACH OR EXCEED RECORDS...WITH MOST
AREAS REACHING MID AND UPPER 70S.
LIKELY POPS EXPECTED SUNDAY NIGHT IN THE WEST...TRANSITIONING TO THE
EAST ON MONDAY AS THE FRONT SLOWS AND MODELS COME MORE IN ALIGNMENT
WITH A POSITION OVER THE COASTAL PLAIN BY MONDAY EVENING.
AGAIN...STRONG LOW LEVEL FORCING AND UPPER DYNAMICS SHOULD PRODUCE
ENOUGH LIFT FOR ISOLATED THUNDER. HIGHS MONDAY WILL BE LEVELING OFF
BY AFTERNOON IN THE WEST AFTER MAXING OUT IN THE UPPER 50S...
MEANWHILE...THE EAST WILL REACH THE MID AND UPPER 60S BEFORE THE
COLD AIR ADVECTION KICKS IN BEHIND THE FRONT. PRECIP WILL TAPER OFF
BY MIDNIGHT IN THE EAST...WITH DRIER AND COOLER AIR SURGING INTO THE
AREA MONDAY NIGHT...LOWS WILL BE IN THE 30S...WITH THE NORTHWEST
FALLING BELOW FREEZING.
HIGH PRESSURE WILL DOMINATE TUESDAY THROUGH THURSDAY...PROVIDING US
WITH COOL...BUT SEASONABLE TEMPERATURES THROUGH THE CHRISTMAS
HOLIDAY. TUESDAYS HIGHS WILL BE IN THE 40S...WITH 45 TO 50 DEGREES
EXPECTED ON CHRISTMAS DAY AFTER A MORNING LOW IN THE MID TO UPPER
20S. COOL AIR WILL BE LOOSENING ITS GRIP IN THE LATE WEEK...WITH AN
INVERTED TROF SETTING UP ALONG THE COAST TO PROVIDE INCREASED
CLOUDINESSS IN THE SOUTH AND EAST. HIGHS THURSDAY ARE LOW CONFIDENCE
AT THIS POINT...50 TO 55 LOOKS REASONABLE AT THIS POINT.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
AS OF 740 PM THURSDAY...
HIGH PRESSURE WILL CONTINUE TO SHIFT EASTWARD TONIGHT ALLOWING FOR
INCREASING LOW LEVEL MOISTURE. THIS MAY LEAD TO SOME LOW STRATUS
(LOW TO MEDIUM CONFIDENCE) GENERALLY IN THE LOW END MVFR/IFR RANGE
BY AROUND DAYBREAK AT KGSO/KINT AND POSSIBLY KFAY (MAYBE MORE VISBY
RESTRICTIONS AT FIRST AT KFAY). CANT RULE OUT SOME BRIEF SUB VFR
CONDITIONS AT KRDU AND KRWI AS WELL. EXPECT ANY LOW STRATUS AND/OR
FOG WILL MIX OUT BY 16/17Z AT THE LATEST. VFR CONDITIONS ARE THEN
EXPECTED TO CONTINUE FOR THE REMAINDER OF THE TAF PERIOD. HOWEVER...
WE WILL LIKELY SEE SUSTAINED WINDS DURING FRIDAY AFTERNOON IN THE 10
TO 15 MPH RANGE... WITH GUSTS POSSIBLE IN THE 20 TO 25 MPH RANGE.
LOOKING AHEAD: WARM/MOIST SOUTHERLY RETURN FLOW WILL INCREASE
ACROSS THE CAROLINAS THROUGH SUNDAY INTO MONDAY. LOW STATUS WILL BE
POSSIBLE MAINLY EACH MORNING...FOLLOWED BY NUMEROUS SHOWERS WITH THE
PASSAGE OF A COLD FRONT SUNDAY NIGHT AND MONDAY.
&&
.CLIMATE...
AS OF 230 PM WEDNESDAY...
DAILY RECORDS FOR SATURDAY/SUNDAY DECEMBER 21/22 ARE AS FOLLOWS:
RALEIGH/DURHAM...
HIGHHI MIN
DECEMBER 21... 71 DEGREES...SET IN 196759 DEGREES...SET IN 1923
DECEMBER 22... 75 DEGREES...SET IN 196761 DEGREES...SET IN 2011
--------------------------------------------------------------------
GREENSBORO...
HIGHHI MIN
DECEMBER 21... 66 DEGREES...SET IN 192355 DEGREES...SET IN 1984
DECEMBER 22... 71 DEGREES...SET IN 192360 DEGREES...SET IN 2011
--------------------------------------------------------------------
FAYETTEVILLE...
HIGHHI MIN
DECEMBER 21... 77 DEGREES...SET IN 193160 DEGREES...SET IN 1923
DECEMBER 22... 75 DEGREES...SET IN 201160 DEGREES...SET IN 2011
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE
&&
$$
SYNOPSIS...MWS
NEAR TERM...NP/SMITH
SHORT TERM...NP
LONG TERM...MLM
AVIATION...NP/MWS
CLIMATE...PWB/KC
AREA FORECAST DISCUSSION
NWS PORTLAND OR
928 AM PST WED DEC 18 2013
.SYNOPSIS...A COLD UPPER LEVEL TROUGH WILL BRING INCREASING SHOWERS
LATER THIS MORNING AND AFTERNOON FOR SW WASHINGTON AND NW
OREGON...AND LATE THIS AFTERNOON AND EVENING FOR THE CENTRAL/SOUTH
WILLAMETTE VALLEY AND THE CASCADES. SNOW LEVELS WILL DRAMATICALLY
DROP TODAY...WITH SNOW ACCUMULATIONS LIKELY FOR THE CASCADE FOOTHILLS
AND CASCADES. DO NOT EXPECT MORE THAN A FEW SNOW FLURRIES FOR THE LOW
LANDS. THERE WILL BE A BREAK IN PRECIPITATION THURSDAY BEFORE A
WARMER SYSTEM BRINGS RAIN AND MOUNTAIN SNOW ON FRI. WILL NEED TO
MONITOR THE POTENTIAL FOR A WINTRY MIX AT SOME LOW ELEVATION
LOCATIONS FRI MORNING. AN UPPER LEVEL RIDGE WILL SET UP OVER THE NE
PAC LATE IN THE WEEK...WITH SEVERAL SYSTEMS PUSHING OVER THE TOP OF
THE RIDGE THROUGH EARLY NEXT WEEK.
&&
...MORNING UPDATE...
A VERY WEAK FRONTAL BOUNDARY MOVED THROUGH THE REGION EARLY THIS
MORNING...WITH LITTLE IMPACT OTHER THAN SOME AREAS OF DRIZZLE. THE
DRIZZLE DID MANAGE TO ACCUMULATE TO A FEW HUNDREDTHS OF AN INCH IN A
FEW LOCATIONS. THIS INITIAL FRONT HAS NOW PUSHED SOUTH OF OUR FCST
AREA FOR THE MOST PART...ALTHOUGH SOME DRIZZLE MAY BE CONTINUING OVER
THE LANE COUNTY CASCADES OVER THE NEXT HOUR OR SO. ANOTHER ROUND OF
PRECIPITATION WILL BE MAKING ITS WAY INTO THE NORTHERN TIER OF OUR
CWA LATER THIS MORNING...THEN PUSHING SOUTH THROUGH THE REGION THIS
AFTERNOON AND THIS EVENING. THE PREVIOUS FCST APPEARS TO BE RUNNING
PRETTY MUCH ON TRACK. DID NUDGE QPF VALUES FOR THE 18Z TO 00Z TIME
FRAME DOWN A BIT. THE PAST FEW RUNS OF THE GFS HAVE BEEN INDICATING
BETTER MOISTURE AND STRONGER LIFT THAN SOME OF THE OTHER MODELS...BUT
THE 12Z RUN SOMEWHAT BACKED OFF OF THE STRONGER SOLUTION. PYLE
.SHORT TERM...
TODAY THROUGH FRIDAY NIGHT...A WEAK FRONT WILL CONTINUE
LIGHT RAIN/DRIZZLE ACROSS THE REGION THIS MORNING...WITH
ACCUMULATIONS GENERALLY LESS THAN A TENTH OF AN INCH. THERE WILL BE A
BRIEF BREAK IN PRECIPITATION LATE THIS MORNING BEFORE A MORE DYNAMIC
DISTURBANCE BRINGS ADDITIONAL RAIN AND MOUNTAIN SNOW THIS AFTERNOON
AND EVENING.
THIS SECOND BOUT OF PRECIPITATION IS ASSOCIATED WITH A COLD UPPER
LEVEL TROUGH THAT IS DROPPING SOUTHWARD FROM THE GULF OF ALASKA.
WATER VAPOR IMAGERY SHOWS THIS TROUGH JUST OFFSHORE VICTORIA B.C.
EARLY THIS MORNING. THE TROUGH HAS TRACKED SLIGHTLY MORE OVER THE
OCEAN THAN THE PREVIOUS MODEL RUNS FORECASTED ALLOWING MORE MOISTURE
TO BECOME AVAILABLE THAN PREVIOUSLY THOUGHT. A COLD POOL WITH 500MB
TEMPERATURES NEAR -28 CELSIUS WILL MOVE OVER THE AREA THIS EVENING
RESULTING IN ENOUGH INSTABILITY AND LIFT TO TAP INTO THIS MOISTURE.
THEREFORE HAVE GREATER FORECAST CONFIDENCE IN SHOWERS FOR TONIGHT AND
HAVE RAISED POPS. THIS TROUGH WILL MOVE FAIRLY QUICKLY THROUGH THE
AREA FROM NW TO SE WITH PRECIPITATION LIMITED TO THE CASCADES AND
LANE COUNTY BY MIDNIGHT TONIGHT.
SNOW LEVELS IS THE GREATEST FORECAST CHALLENGE WITH THIS SYSTEM AS
THEY WILL DROP DRAMATICALLY THROUGHOUT THE DAY. SNOW LEVELS NEAR 6000
FEET EARLY THIS MORNING WILL LOWER TO LESS THAN A 1000 FEET THIS
EVENING. THE SHOWERS SHOULD LEAD THE COLDER AIR AND EXPECT ONLY SNOW
ACCUMULATIONS FOR THE CASCADES AND CASCADE FOOTHILLS.
THE HRRR MODEL WHICH HISTORICALLY HAS HANDLED THESE TYPE OF SHOWERS
VERY WELL SHOWS THESE SHOWERS REACHING THE SW WA COAST AROUND 17Z (11
AM) AND THE PORTLAND METRO AREA AROUND 22Z (2 PM)...AND OVER THE
CENTRAL WILLAMETTE VALLEY AROUND 4 PM. THE QUICK MOVING NATURE OF THE
TROUGH WILL LIMIT RAIN/SNOW ACCUMULATIONS AND EXPECT LESS THAN 0.25
INCH OF RAIN FOR THE NORTHERN LOW LAND AREAS AND LESS THAN 0.15 INCH
FOR THE SOUTHERN LOW LAND AREAS. THE CASCADES WILL LIKELY HAVE 1 TO 3
INCHES OF SNOW WITH THE CASCADE FOOTHILLS POSSIBLY MEASURING UP TO 2
INCHES.
HIGH PRESSURE WILL BUILD BEHIND THE TROUGH EARLY THURSDAY MORNING.
LINGERING SURFACE MOISTURE FROM THE EVENING SHOWERS COMBINED WITH
LIGHT WINDS AND CLEARING SKIES SHOULD RESULT IN WIDESPREAD RADIATION
FOG EARLY THURSDAY MORNING. TEMPERATURES WILL BE BELOW FREEZING WITH
FREEZING FOG POSSIBLY RESULTING IN SLICK DRIVING CONDITIONS FOR THE
MORNING COMMUTE. WEAK OFFSHORE WINDS SHOULD DEVELOP THU AFTERNOON AND
HELP DISSIPATE THE FOG. THURSDAY WILL BE DRY AND COLD WITH INCREASING
CLOUDS AHEAD OF THE NEXT FRONT.
THE NEXT MORE ORGANIZED FRONT WILL APPROACH THURSDAY NIGHT. THIS
FRONT HAS A LOT MORE MOISTURE WITH IT AS GFS IS FORECASTING MODELED
TROPICAL PRECIPITABLE WATER VALUES NEAR AN INCH. THE DIFFERENT
FORECAST MODELS VARY ON THE TIMING...AND QPF WITH THIS FRONT WITH THE
NAM MODEL BEING THE MOST AGGRESSIVE. HAVE LEANED TOWARDS A BLEND OF
THE GFS AND NAM FOR TIMING AND AMOUNT OF PRECIPITATION. THE AVAILABLE
MOISTURE...LIFT AND APPARENT SLOW MOVING NATURE OF THIS FRONT
PROVIDES GREAT POTENTIAL FOR A DECENT RAINFALL EVENT FRIDAY. SNOW
LEVELS SHOULD RAPIDLY WARM AHEAD OF THIS FRONT BUT THERE IS STILL THE
POSSIBILITY THAT SOME OF THE PRECIPITATION WILL OVER RUN THE WARMING
LEADING TO A BRIEF PERIOD OF LOW ELEVATION SNOW.
HOWEVER...SIGNIFICANT IMPACTS APPEAR UNLIKELY...AS THERE WILL LIKELY
NOT BE MUCH OF A COLD POOL ON THE EAST SIDE OF THE CASCADES.
WILL HAVE A BETTER IDEA OF THE DEPTH OF THE COLD AIR AND WHAT IT WILL
TAKE TO ERODE THE COLD AIR AFTER THE WEDNESDAY EVENT PLAYS OUT.
HARTLEY
.LONG TERM...SATURDAY THROUGH TUESDAY...MADE NO CHANGES AND PREVIOUS
DISCUSSION FOLLOWS...AT THIS TIME...THE EXTENDED PORTION OF THE FCST
APPEARS TO ON THE MILD AND MOIST SIDE. AN UPPER LEVEL RIDGE OVER THE
NE PAC IS MODELED TO STEER SEVERAL BATCHES OF MOISTURE SOUTH INTO THE
PAC NW OVER THE WEEKEND AND EARLY NEXT WEEK. THIS WILL LIKELY LEAD TO
PERIODS OF LIGHT RAINFALL. CONFIDENCE ON THE TIMING OF THESE SYSTEMS
IS NOT HIGH AT THIS TIME. DO NOT CURRENTLY EXPECT ANY SIGNIFICANT
WEATHER IMPACTS TO HOLIDAY TRAVEL AHEAD OF CHRISTMAS. PYLE
&&
.AVIATION...WIDESPREAD IFR STRATUS AND FOG ACROSS THE REGION...
WITH AREAS OF DRIZZLE. CONDITIONS NOT CHANGING MUCH THROUGH 19Z.
BUT AS UPPER LEVEL SYSTEM MOVES ACROSS REGION LATER THIS AM AND
EARLY AFTERNOON...CONDITIONS WILL IMPROVE TO MVFR...AND EVENTUALLY
VFR TOWARDS 00Z. HIGHER TERRAIN REMAINS OBSCURED IN CLOUDS THROUGH
04Z...BUT LIKELY LONGER AGAINST THE CASCADES AND POINTS TO E AND
S OF KEUG. AIR MASS WILL DRY TONIGHT...BUT STILL EXPECT WITH
POCKETS OF FOG/LOW STRATUS REFORMING IN VALLEYS/BAYS AFTER 10Z.
KPDX AND APPROACHES...IFR STRATUS CONTINUES THIS AM...BUT WILL SEE
CLOUDS BREAK AND LIFT TO MVFR AFTER 19Z...WITH VFR EXPECTED BY
00Z OR 01Z. SHOULD REMAIN VFR THROUGH 08Z...THEN IFR STRATUS AND
FOG REFORMING.ROCKEY
&&
.MARINE...AT 9 AM...COLD FRONT WAS 125 MILES NNW OF ASTORIA AND
MOVING TO THE SE. THIS FRONT WILL MOVE ACROSS THE COASTAL WATERS
THIS AM. N TO NW WIND WILL INCREASE BEHIND THE FRONT WITH WINDS
GUSTING 25 KT. CURRENT ADVISORIES LOOK ON TRACK SO NO CHANGES.
SEAS CURRENTLY 6 TO 7 FT...BUT WILL BUILD AGAIN TODAY AS WINDS
INCREASE. STILL EXPECTING SEAS OF 9 TO 11 FT LATER TODAY AND
TONIGHT WITH HIGHEST OVER THE OUTER WATERS.
SEAS AND WINDS EASE BACK ON THU AND THU NIGHT. BUT ANOTHER FRONT
WILL BRING GUSTY WINDS...POSSIBLY GALE FORCE...AND HIGHER SEAS
FOR FRI AND SAT. ROCKEY.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS AND HAZARDOUS SEAS FOR
THIS AFTERNOON THROUGH THU AM ON ALL COASTAL WATERS.
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA BAR CONDITIONS
FROM 3 PM TO 7 PM TODAY.
&&
$$
MORE WEATHER INFORMATION ONLINE AT..
HTTP://WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV
WWW.TWITTER.COM/NWSPORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
AREA FORECAST DISCUSSION
NWS PORTLAND OR
327 AM PST WED DEC 18 2013
.SYNOPSIS...A WEAK FRONT WILL CONTINUE LIGHT RAIN AND DRIZZLE THIS
MORNING. A COLD TROUGH WILL BRING A SHOT OF SHOWERS LATER THIS
MORNING AND AFTERNOON FOR SW WASHINGTON AND NW OREGON...AND LATE THIS
AFTERNOON AND EVENING FOR THE CENTRAL/SOUTH WILLAMETTE VALLEY AND THE
CASCADES. SNOW LEVELS WILL DRAMATICALLY DROP TODAY...WITH SNOW
ACCUMULATIONS LIKELY FOR THE CASCADE FOOTHILLS AND CASCADES. DO NOT
EXPECT MORE THAN A FEW SNOW FLURRIES FOR THE LOW LANDS. THERE WILL BE
A BREAK IN PRECIPITATION THURSDAY BEFORE A WARMER SYSTEM BRINGS RAIN
AND MOUNTAIN SNOW ON FRI. WILL NEED TO MONITOR THE POTENTIAL FOR A
WINTRY MIX AT SOME LOW ELEVATION LOCATIONS FRI MORNING. AN UPPER
LEVEL RIDGE WILL SET UP OVER THE NE PAC LATE IN THE WEEK...WITH
SEVERAL SYSTEMS PUSHING OVER THE TOP OF THE RIDGE
THROUGH EARLY NEXT WEEK.
&&
.SHORT TERM...TODAY THROUGH FRIDAY NIGHT...A WEAK FRONT WILL CONTINUE
LIGHT RAIN/DRIZZLE ACROSS THE REGION THIS MORNING...WITH
ACCUMULATIONS GENERALLY LESS THAN A TENTH OF AN INCH. THERE WILL BE A
BRIEF BREAK IN PRECIPITATION LATE THIS MORNING BEFORE A MORE DYNAMIC
DISTURBANCE BRINGS ADDITIONAL RAIN AND MOUNTAIN SNOW THIS AFTERNOON
AND EVENING.
THIS SECOND BOUT OF PRECIPITATION IS ASSOCIATED WITH A COLD UPPER
LEVEL TROUGH THAT IS DROPPING SOUTHWARD FROM THE GULF OF ALASKA.
WATER VAPOR IMAGERY SHOWS THIS TROUGH JUST OFFSHORE VICTORIA B.C.
EARLY THIS MORNING. THE TROUGH HAS TRACKED SLIGHTLY MORE OVER THE
OCEAN THAN THE PREVIOUS MODEL RUNS FORECASTED ALLOWING MORE MOISTURE
TO BECOME AVAILABLE THAN PREVIOUSLY THOUGHT. A COLD POOL WITH 500MB
TEMPERATURES NEAR -28 CELSIUS WILL MOVE OVER THE AREA THIS EVENING
RESULTING IN ENOUGH INSTABILITY AND LIFT TO TAP INTO THIS MOISTURE.
THEREFORE HAVE GREATER FORECAST CONFIDENCE IN SHOWERS FOR TONIGHT AND
HAVE RAISED POPS. THIS TROUGH WILL MOVE FAIRLY QUICKLY THROUGH THE
AREA FROM NW TO SE WITH PRECIPITATION LIMITED TO THE CASCADES AND
LANE COUNTY BY MIDNIGHT TONIGHT.
SNOW LEVELS IS THE GREATEST FORECAST CHALLENGE WITH THIS SYSTEM AS
THEY WILL DROP DRAMATICALLY THROUGHOUT THE DAY. SNOW LEVELS NEAR 6000
FEET EARLY THIS MORNING WILL LOWER TO LESS THAN A 1000 FEET THIS
EVENING. THE SHOWERS SHOULD LEAD THE COLDER AIR AND EXPECT ONLY SNOW
ACCUMULATIONS FOR THE CASCADES AND CASCADE FOOTHILLS.
THE HRRR MODEL WHICH HISTORICALLY HAS HANDLED THESE TYPE OF SHOWERS
VERY WELL SHOWS THESE SHOWERS REACHING THE SW WA COAST AROUND 17Z (11
AM) AND THE PORTLAND METRO AREA AROUND 22Z (2 PM)...AND OVER THE
CENTRAL WILLAMETTE VALLEY AROUND 4 PM. THE QUICK MOVING NATURE OF THE
TROUGH WILL LIMIT RAIN/SNOW ACCUMULATIONS AND EXPECT LESS THAN 0.25
INCH OF RAIN FOR THE NORTHERN LOW LAND AREAS AND LESS THAN 0.15 INCH
FOR THE SOUTHERN LOW LAND AREAS. THE CASCADES WILL LIKELY HAVE 1 TO 3
INCHES OF SNOW WITH THE CASCADE FOOTHILLS POSSIBLY MEASURING UP TO 2
INCHES.
HIGH PRESSURE WILL BUILD BEHIND THE TROUGH EARLY THURSDAY MORNING.
LINGERING SURFACE MOISTURE FROM THE EVENING SHOWERS COMBINED WITH
LIGHT WINDS AND CLEARING SKIES SHOULD RESULT IN WIDESPREAD RADIATION
FOG EARLY THURSDAY MORNING. TEMPERATURES WILL BE BELOW FREEZING WITH
FREEZING FOG POSSIBLY RESULTING IN SLICK DRIVING CONDITIONS FOR THE
MORNING COMMUTE. WEAK OFFSHORE WINDS SHOULD DEVELOP THU AFTERNOON AND
HELP DISSIPATE THE FOG. THURSDAY WILL BE DRY AND COLD WITH INCREASING
CLOUDS AHEAD OF THE NEXT FRONT.
THE NEXT MORE ORGANIZED FRONT WILL APPROACH THURSDAY NIGHT. THIS
FRONT HAS A LOT MORE MOISTURE WITH IT AS GFS IS FORECASTING MODELED
TROPICAL PRECIPITABLE WATER VALUES NEAR AN INCH. THE DIFFERENT
FORECAST MODELS VARY ON THE TIMING...AND QPF WITH THIS FRONT WITH THE
NAM MODEL BEING THE MOST AGGRESSIVE. HAVE LEANED TOWARDS A BLEND OF
THE GFS AND NAM FOR TIMING AND AMOUNT OF PRECIPITATION. THE AVAILABLE
MOISTURE...LIFT AND APPARENT SLOW MOVING NATURE OF THIS FRONT
PROVIDES GREAT POTENTIAL FOR A DECENT RAINFALL EVENT FRIDAY. SNOW
LEVELS SHOULD RAPIDLY WARM AHEAD OF THIS FRONT BUT THERE IS STILL THE
POSSIBILITY THAT SOME OF THE PRECIPITATION WILL OVER RUN THE WARMING
LEADING TO A BRIEF PERIOD OF LOW ELEVATION SNOW.
HOWEVER...SIGNIFICANT IMPACTS APPEAR UNLIKELY...AS THERE WILL LIKELY
NOT BE MUCH OF A COLD POOL ON THE EAST SIDE OF THE CASCADES.
WILL HAVE A BETTER IDEA OF THE DEPTH OF THE COLD AIR AND WHAT IT WILL
TAKE TO ERODE THE COLD AIR AFTER THE WEDNESDAY EVENT PLAYS OUT.
HARTLEY
.LONG TERM...SATURDAY THROUGH TUESDAY...MADE NO CHANGES AND PREVIOUS
DISCUSSION FOLLOWS...AT THIS TIME...THE EXTENDED PORTION OF THE FCST
APPEARS TO ON THE MILD AND MOIST SIDE. AN UPPER LEVEL RIDGE OVER THE
NE PAC IS MODELED TO STEER SEVERAL BATCHES OF MOISTURE SOUTH INTO THE
PAC NW OVER THE WEEKEND AND EARLY NEXT WEEK. THIS WILL LIKELY LEAD TO
PERIODS OF LIGHT RAINFALL. CONFIDENCE ON THE TIMING OF THESE SYSTEMS
IS NOT HIGH AT THIS TIME. DO NOT CURRENTLY EXPECT ANY SIGNIFICANT
WEATHER IMPACTS TO HOLIDAY TRAVEL AHEAD OF CHRISTMAS. PYLE
&&
.AVIATION...IFR AND LIFR CIGS AND OCCASIONAL VIS CONTINUE THIS
MORNING THROUGH ABOUT 18Z-20Z. EXPECT MVFR CIGS AROUND 2500-3500
FT WITH DRIZZLE/LIGHT RAIN WHEN THE PRIMARY FRONT MOVES THROUGH
LATER THIS AFTERNOON. CIGS LIFT TO LOW END MVFR TONIGHT...WITH A
THREAT FOR LIFR FOG EARLY THURSDAY MORNING.
KPDX AND APPROACHES...IFR CIGS BUT WITH VFR VIS WILL CONTINUE
THROUGH ABOUT 18Z THIS MORNING WHEN THE NEXT FRONT APPROACHES.
CIGS LIFT TO MVFR/LOW END VFR BEHIND THE FRONT...BUT IFR/LIFR FOG
MAY REDEVELOP AROUND 12Z THURSDAY. /27
&&
.MARINE...AN APPROACHING COLD FRONT WILL BRING GUSTY NW POST
FRONTAL WINDS UP TO 25 KT AND SEAS ABOVE 10 FT ACROSS THE WATERS
THIS AFTERNOON. THE SMALL CRAFT ADVISORY FOR BOTH WINDS AND SEAS
REMAINS IN EFFECT THROUGH EARLY THURSDAY MORNING.
SEAS REMAIN AROUND 7 OR 8 FT THIS MORNING BEFORE RISING TO 10 TO
11 FT AS WINDS PICK UP LATER TODAY. SEAS AND WINDS EASE BACK ON
THU AND THU NIGHT. BUT ANOTHER FRONT WILL BRING ANOTHER ROUND OF
GUSTY WINDS AND SEAS FOR LATER FRI AND SAT. ROCKEY.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM NOON TODAY TO NOON PST
THURSDAY FOR COASTAL WATERS FROM CAPE SHOALWATER TO
FLORENCE OUT 60 NM.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM NOON TODAY TO NOON
PST THURSDAY FOR COASTAL WATERS FROM CAPE SHOALWATER TO
FLORENCE OUT 60 NM.
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 3 PM
THIS AFTERNOON TO 7 PM PST THIS EVENING.
&&
$$
MORE WEATHER INFORMATION ONLINE AT..
HTTP://WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV
WWW.TWITTER.COM/NWSPORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
634 AM EST WED DEC 18 2013
.SYNOPSIS...
UPPER LVL TROUGH OVER THE NORTHEAST CONUS THIS MORNING WILL LIFT
OUT...GIVING WAY TO A BUILDING RIDGE OFF OF THE E COAST FOR THE
REST OF THE WEEK. AT THE SFC...A QUASI-STATIONARY FRONT WILL REMAIN
DRAPED ACROSS THE EASTERN GRT LKS LATE THIS WEEK AND THROUGH THE
WEEKEND. THIS BOUNDARY WILL FINALLY PUSH SOUTHEAST THRU PA LATE
SUNDAY OR EARLY MONDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WATER VAPOR LOOP SHOWS UPPER TROUGH AXIS PASSING EAST OF PA AT
11Z. IN IT/S WAKE...A COLD WESTERLY FLOW CROSSING LK ERIE SHOULD
SUPPORT A SINGLE LE SNOW BAND JUST NORTH OF THE PA BORDER
TODAY...AS INDICATED BY LATEST NAM AND RAP OUTPUT. ELSEWHERE...LOW
LVL MOISTURE TRAPPED BENEATH SUBSIDENCE INVERSION AND FORCED TO
ASCEND THE ALLEGHENIES WILL PRODUCE FLURRIES/SCT -SHSN ACROSS THE
W MTNS. ACCUMULATIONS SHOULD BE MAINLY JUST A DUSTING.
HOWEVER...PERHAPS UP TO AN INCH OVR NW WARREN CO...DUE TO FRINGE
EFFECTS OF LE BAND.
TIGHTENING PRESSURE GRADIENT BTWN HIGH PRES OVR THE SERN STATES AND
THE RAPIDLY INTENSIFYING LOW E OF NEW ENG WILL CREATE A BRISK WEST
WIND TODAY ACROSS ALL OF CENTRAL PA WITH GUSTS BTWN 15-25KTS PER
LATEST BUFKIT SOUNDINGS /HIGHEST ACROSS THE LAURELS AND SC MTNS/.
MIXING TO THE ENS MEAN 925MB TEMPS SUPPORTS HIGH TEMPS SEVERAL DEG BLW
NORMAL...RANGING FROM THE M20S W MTNS...TO THE M30S ACROSS THE
LOWER SUSQ VALLEY WHERE DOWNSLOPING NW FLOW SHOULD YIELD PTSUNNY
SKIES.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
FALLING INVERSION HGTS WITH ARRIVAL OF SFC RIDGE SHOULD BRING AN
END TO ANY LINGERING FLURRIES ACROSS THE NW MTNS BY THIS EVENING.
LIGHT WINDS AND A MCLEAR SKY SHOULD ALLOW TEMPS FALL FAIRLY
QUICKLY INTO THE UTEENS/L20S THIS EVENING. HOWEVER...INCREASING
CIRRUS AND DEVELOPING SWRLY BREEZE AS SFC RIDGE PASSES EAST OF THE
AREA SHOULD CAUSE TEMPS TO LEVEL OFF OR EVEN RISE A BIT LATE
TONIGHT.
DEEP SW FLOW INDICATED BY THURSDAY...AS RIDGE BUILDS OFF THE EAST
COAST AND TROUGH DIGS OVR THE WESTERN CONUS. THIS SW FLOW WILL
ADVECT MUCH MILDER AIR INTO PA WITH READINGS LIKELY APPROACHING
40F IN THE NORTH AND SURGING WELL INTO THE 40S ACROSS THE SOUTHERN
COUNTIES. LL JET AND ASSOC PLUME OF HIGH PWATS AT INTERFACE OF
EASTERN RIDGE/WESTERN TROUGH WILL BE FOCUSED ACROSS THE EASTERN
GRT LKS BUT WILL LIKELY PRODUCE MCLDY SKIES ACROSS NORTHERN PA ON
THURSDAY...WHILE MSUNNY LIKELY IN THE SOUTH.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
LITTLE SPREAD AMONGST MED RANGE MDLS THRU THE UPCOMING
WEEKEND...ALL OF WHICH SHOW AN ANOMALOUS TROUGH CENTERED OVR THE W
PLAINS AND ANOMALOUS RIDGE OFF OF THE SE COAST. AT INTERFACE OF
THESE SYSTEMS...A DEEP SOUTHERLY FLOW AND ASSOC PLUME OF HIGH
PWATS WILL EXTEND ALONG QUASI-STATIONARY FRONT DRAPED FROM THE
WESTERN GULF OF MEX TO THE E GRT LKS.
WAVES OF LOW PRESSURE RIDING WEST OF PA WILL BRING THE CHC OF
RAIN TO MAINLY THE NW COUNTIES AND KEEP THE ENTIRE CWA ON THE WARM
SIDE OF THE BNDRY. BY SUNDAY...THE STRONGEST OF THE WAVES IS
PROGGED TO TRACK ACROSS NW PA. GEFS PWATS ON THE ORDER OF 3-4SD
ABV NORMAL WILL ACCOMPANY THE ASSOC LL JET AND WILL LIKELY PRODUCE
HVY RAIN JUST WEST OF LOW TRACK. LATEST MDL BLEND INDICATES THIS
HVY RAIN THREAT WILL BE JUST WEST OF OUR AREA. IN THE WARM
SECTOR...NEAR RECORD HIGH TEMPS ARE POSSIBLE SUNDAY...AS GEFS MEAN
925/850 TEMPS SURGE TO NR 2SD ABV NORMAL. 00Z ECMWF MOS NUMBERS
ALREADY INDICATING NR RECORD TEMPS IN THE L/M60S ACROSS THE
EASTERN HALF OF THE STATE.
TRAILING COLD FRONT SHOULD BRING A RETURN TO MORE DECEMBER-LIKE
TEMPS BY EARLY NEXT WEEK.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
WIDESPREAD FOG WITH MVFR VSBYS AND CIGS...AND A FEW LIGHT SNOW
SHOWERS WILL CONTINUE THROUGH THE MID MORNING HOURS. CONDITIONS
SHOULD IMPROVE LATER THIS MORNING...AFTER 14-15Z AS HIGH PRESSURE
BUILDS INTO REGION AND WINDS INCREASE AND PROVIDE SOME MIXING OF
THE LOWER LEVELS.
WNW WINDS WILL BECOME BRISK LATER THIS MORNING...AS THE PRESSURE
GRADIENT TIGHTENS BETWEEN DEEPENING LOW PRES OVER THE CANADIAN
MARITIMES AND HIGH PRES OVER THE SERN US. EASTERN TAF SITES SHOULD
QUICKLY IMPROVE TO VFR CONDS IN DOWNSLOPING FLOW. JST AND BFD
WILL TAKE A BIT LONGER...BUT WILL EVENTUALLY IMPROVE TO VFR AS WELL.
AFTER A QUIET WEATHER ON THURS...A DEVELOPING MOIST SOUTHERLY FLOW
WILL TURN THINGS UNSETTLED FRI INTO THIS WEEKEND.
OUTLOOK...
THU...GENERALLY VFR.
FRI-SUN...REDUCED CONDS LKLY AS ABUNDANT MOISTURE AND MILDER AIR
STREAMS NEWD AHEAD OF A SLOW-MOVING FRONTAL SYSTEM.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...FITZGERALD
NEAR TERM...FITZGERALD
SHORT TERM...FITZGERALD
LONG TERM...FITZGERALD
AVIATION...GARTNER/EVANEGO
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
617 AM EST WED DEC 18 2013
.SYNOPSIS...
UPPER LVL TROUGH OVER THE NORTHEAST CONUS THIS MORNING WILL LIFT
OUT...GIVING WAY TO A BUILDING RIDGE OFF OF THE E COAST FOR THE
REST OF THE WEEK. AT THE SFC...A QUASI-STATIONARY FRONT WILL REMAIN
DRAPED ACROSS THE EASTERN GRT LKS LATE THIS WEEK AND THROUGH THE
WEEKEND. THIS BOUNDARY WILL FINALLY PUSH SOUTHEAST THRU PA LATE
SUNDAY OR EARLY MONDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WATER VAPOR LOOP SHOWS UPPER TROUGH AXIS PASSING EAST OF PA AT
10Z. IN IT/S WAKE...A COLD WESTERLY FLOW CROSSING LK ERIE SHOULD
SUPPORT A SINGLE LE SNOW BAND JUST NORTH OF THE PA BORDER
TODAY...AS INDICATED BY LATEST NAM AND RAP OUTPUT. ELSEWHERE...LOW
LVL MOISTURE TRAPPED BENEATH SUBSIDENCE INVERSION AND FORCED TO
ASCEND THE ALLEGHENIES WILL PRODUCE FLURRIES/SCT -SHSN ACROSS THE
W MTNS. ACCUMULATIONS SHOULD BE MAINLY JUST A DUSTING.
HOWEVER...PERHAPS UP TO AN INCH OVR NW WARREN CO...DUE TO FRINGE
EFFECTS OF LE BAND.
TIGHTENING PRESSURE GRADIENT BTWN HIGH PRES OVR THE SERN STATES AND
THE RAPIDLY INTENSIFYING LOW E OF NEW ENG WILL CREATE A BRISK WEST
WIND TODAY ACROSS ALL OF CENTRAL PA WITH GUSTS BTWN 15-25KTS PER
LATEST BUFKIT SOUNDINGS /HIGHEST ACROSS THE LAURELS AND SC MTNS/.
MIXING TO THE ENS MEAN 925MB TEMPS SUPPORTS HIGH TEMPS SEVERAL DEG BLW
NORMAL...RANGING FROM THE M20S W MTNS...TO THE M30S ACROSS THE
LOWER SUSQ VALLEY WHERE DOWNSLOPING NW FLOW SHOULD YIELD PTSUNNY
SKIES.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
FALLING INVERSION HGTS WITH ARRIVAL OF SFC RIDGE SHOULD BRING AN
END TO ANY LINGERING FLURRIES ACROSS THE NW MTNS BY THIS EVENING.
LIGHT WINDS AND A MCLEAR SKY SHOULD ALLOW TEMPS FALL FAIRLY
QUICKLY INTO THE UTEENS/L20S THIS EVENING. HOWEVER...INCREASING
CIRRUS AND DEVELOPING SWRLY BREEZE AS SFC RIDGE PASSES EAST OF THE
AREA SHOULD CAUSE TEMPS TO LEVEL OFF OR EVEN RISE A BIT LATE
TONIGHT.
DEEP SW FLOW INDICATED BY THURSDAY...AS RIDGE BUILDS OFF THE EAST
COAST AND TROUGH DIGS OVR THE WESTERN CONUS. THIS SW FLOW WILL
ADVECT MUCH MILDER AIR INTO PA WITH READINGS LIKELY APPROACHING
40F IN THE NORTH AND SURGING WELL INTO THE 40S ACROSS THE SOUTHERN
COUNTIES. LL JET AND ASSOC PLUME OF HIGH PWATS AT INTERFACE OF
EASTERN RIDGE/WESTERN TROUGH WILL BE FOCUSED ACROSS THE EASTERN
GRT LKS BUT WILL LIKELY PRODUCE MCLDY SKIES ACROSS NORTHERN PA ON
THURSDAY...WHILE MSUNNY LIKELY IN THE SOUTH.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
LITTLE SPREAD AMONGST MED RANGE MDLS THRU THE UPCOMING
WEEKEND...ALL OF WHICH SHOW AN ANOMALOUS TROUGH CENTERED OVR THE W
PLAINS AND ANOMALOUS RIDGE OFF OF THE SE COAST. AT INTERFACE OF
THESE SYSTEMS...A DEEP SOUTHERLY FLOW AND ASSOC PLUME OF HIGH
PWATS WILL EXTEND ALONG QUASI-STATIONARY FRONT DRAPED FROM THE
WESTERN GULF OF MEX TO THE E GRT LKS.
WAVES OF LOW PRESSURE RIDING WEST OF PA WILL BRING THE CHC OF
RAIN TO MAINLY THE NW COUNTIES AND KEEP THE ENTIRE CWA ON THE WARM
SIDE OF THE BNDRY. BY SUNDAY...THE STRONGEST OF THE WAVES IS
PROGGED TO TRACK ACROSS NW PA. GEFS PWATS ON THE ORDER OF 3-4SD
ABV NORMAL WILL ACCOMPANY THE ASSOC LL JET AND WILL LIKELY PRODUCE
HVY RAIN JUST WEST OF LOW TRACK. LATEST MDL BLEND INDICATES THIS
HVY RAIN THREAT WILL BE JUST WEST OF OUR AREA. IN THE WARM
SECTOR...NEAR RECORD HIGH TEMPS ARE POSSIBLE SUNDAY...AS GEFS MEAN
925/850 TEMPS SURGE TO NR 2SD ABV NORMAL. 00Z ECMWF MOS NUMBERS
ALREADY INDICATING NR RECORD TEMPS IN THE L/M60S ACROSS THE
EASTERN HALF OF THE STATE.
TRAILING COLD FRONT SHOULD BRING A RETURN TO MORE DECEMBER-LIKE
TEMPS BY EARLY NEXT WEEK.
&&
.AVIATION /11Z WEDNESDAY THROUGH SUNDAY/...
WIDESPREAD FOG WITH MVFR VSBYS AND CIGS...AND A FEW LIGHT SNOW
SHOWERS WILL CONTINUE THROUGH THE MID MORNING HOURS. CONDITIONS
SHOULD IMPROVE LATER THIS MORNING...AFTER 14-15Z AS HIGH PRESSURE
BUILDS INTO REGION AND WINDS INCREASE AND PROVIDE SOME MIXING OF
THE LOWER LEVELS.
WNW WINDS WILL BECOME BRISK LATER THIS MORNING...AS THE PRESSURE
GRADIENT TIGHTENS BETWEEN DEEPENING LOW PRES OVER THE CANADIAN
MARITIMES AND HIGH PRES OVER THE SERN US. EASTERN TAF SITES SHOULD
QUICKLY IMPROVE TO VFR CONDS IN DOWNSLOPING FLOW. JST AND BFD
WILL TAKE A BIT LONGER...BUT WILL EVENTUALLY IMPROVE TO VFR AS WELL.
AFTER A QUIET WEATHER ON THURS...A DEVELOPING MOIST SOUTHERLY FLOW
WILL TURN THINGS UNSETTLED FRI INTO THIS WEEKEND.
OUTLOOK...
THU...GENERALLY VFR.
FRI-SUN...REDUCED CONDS LKLY AS ABUNDANT MOISTURE AND MILDER AIR
STREAMS NEWD AHEAD OF A SLOW-MOVING FRONTAL SYSTEM.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...FITZGERALD
NEAR TERM...FITZGERALD
SHORT TERM...FITZGERALD
LONG TERM...FITZGERALD
AVIATION...GARTNER/EVANEGO
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
547 AM EST WED DEC 18 2013
.SYNOPSIS...
UPPER LVL TROUGH OVER THE NORTHEAST CONUS THIS MORNING WILL LIFT
OUT...GIVING WAY TO A BUILDING RIDGE OFF OF THE E COAST FOR THE
REST OF THE WEEK. AT THE SFC...A QUASI-STATIONARY FRONT WILL REMAIN
DRAPED ACROSS THE EASTERN GRT LKS LATE THIS WEEK AND THROUGH THE
WEEKEND. THIS BOUNDARY WILL FINALLY PUSH SOUTHEAST THRU PA LATE
SUNDAY OR EARLY MONDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WATER VAPOR LOOP SHOWS UPPER TROUGH AXIS PASSING EAST OF PA AT
10Z. IN IT/S WAKE...A COLD WESTERLY FLOW CROSSING LK ERIE SHOULD
SUPPORT A SINGLE LE SNOW BAND JUST NORTH OF THE PA BORDER
TODAY...AS INDICATED BY LATEST NAM AND RAP OUTPUT. ELSEWHERE...LOW
LVL MOISTURE TRAPPED BENEATH SUBSIDENCE INVERSION AND FORCED TO
ASCEND THE ALLEGHENIES WILL PRODUCE FLURRIES/SCT -SHSN ACROSS THE
W MTNS. ACCUMULATIONS SHOULD BE MAINLY JUST A DUSTING.
HOWEVER...PERHAPS UP TO AN INCH OVR NW WARREN CO...DUE TO FRINGE
EFFECTS OF LE BAND.
TIGHTENING PRESSURE GRADIENT BTWN HIGH PRES OVR THE SERN STATES AND
THE RAPIDLY INTENSIFYING LOW E OF NEW ENG WILL CREATE A BRISK WEST
WIND TODAY ACROSS ALL OF CENTRAL PA WITH GUSTS BTWN 15-25KTS PER
LATEST BUFKIT SOUNDINGS /HIGHEST ACROSS THE LAURELS AND SC MTNS/.
MIXING TO THE ENS MEAN 925MB TEMPS SUPPORTS HIGH TEMPS SEVERAL DEG BLW
NORMAL...RANGING FROM THE M20S W MTNS...TO THE M30S ACROSS THE
LOWER SUSQ VALLEY WHERE DOWNSLOPING NW FLOW SHOULD YIELD PTSUNNY
SKIES.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
FALLING INVERSION HGTS WITH ARRIVAL OF SFC RIDGE SHOULD BRING AN
END TO ANY LINGERING FLURRIES ACROSS THE NW MTNS BY THIS EVENING.
LIGHT WINDS AND A MCLEAR SKY SHOULD ALLOW TEMPS FALL FAIRLY
QUICKLY INTO THE UTEENS/L20S THIS EVENING. HOWEVER...INCREASING
CIRRUS AND DEVELOPING SWRLY BREEZE AS SFC RIDGE PASSES EAST OF THE
AREA SHOULD CAUSE TEMPS TO LEVEL OFF OR EVEN RISE A BIT LATE
TONIGHT.
DEEP SW FLOW INDICATED BY THURSDAY...AS RIDGE BUILDS OFF THE EAST
COAST AND TROUGH DIGS OVR THE WESTERN CONUS. THIS SW FLOW WILL
ADVECT MUCH MILDER AIR INTO PA WITH READINGS LIKELY APPROACHING
40F IN THE NORTH AND SURGING WELL INTO THE 40S ACROSS THE SOUTHERN
COUNTIES. LL JET AND ASSOC PLUME OF HIGH PWATS AT INTERFACE OF
EASTERN RIDGE/WESTERN TROUGH WILL BE FOCUSED ACROSS THE EASTERN
GRT LKS BUT WILL LIKELY PRODUCE MCLDY SKIES ACROSS NORTHERN PA ON
THURSDAY...WHILE MSUNNY LIKELY IN THE SOUTH.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
LITTLE SPREAD AMONGST MED RANGE MDLS THRU THE UPCOMING
WEEKEND...ALL OF WHICH SHOW AN ANOMALOUS TROUGH CENTERED OVR THE W
PLAINS AND ANOMALOUS RIDGE OFF OF THE SE COAST. AT INTERFACE OF
THESE SYSTEMS...A DEEP SOUTHERLY FLOW AND ASSOC PLUME OF HIGH
PWATS WILL EXTEND ALONG QUASI-STATIONARY FRONT DRAPED FROM THE
WESTERN GULF OF MEX TO THE E GRT LKS.
WAVES OF LOW PRESSURE RIDING WEST OF PA WILL BRING THE CHC OF
RAIN TO MAINLY THE NW COUNTIES AND KEEP THE ENTIRE CWA ON THE WARM
SIDE OF THE BNDRY. BY SUNDAY...THE STRONGEST OF THE WAVES IS
PROGGED TO TRACK ACROSS NW PA. GEFS PWATS ON THE ORDER OF 3-4SD
ABV NORMAL WILL ACCOMPANY THE ASSOC LL JET AND WILL LIKELY PRODUCE
HVY RAIN JUST WEST OF LOW TRACK. LATEST MDL BLEND INDICATES THIS
HVY RAIN THREAT WILL BE JUST WEST OF OUR AREA. IN THE WARM
SECTOR...NEAR RECORD HIGH TEMPS ARE POSSIBLE SUNDAY...AS GEFS MEAN
925/850 TEMPS SURGE TO NR 2SD ABV NORMAL. 00Z ECMWF MOS NUMBERS
ALREADY INDICATING NR RECORD TEMPS IN THE L/M60S ACROSS THE
EASTERN HALF OF THE STATE.
TRAILING COLD FRONT SHOULD BRING A RETURN TO MORE DECEMBER-LIKE
TEMPS BY EARLY NEXT WEEK.
&&
.AVIATION /10Z WEDNESDAY THROUGH SUNDAY/...
A WEAK PRESSURE GRADIENT ACROSS CENTRAL AND EASTERN PENN WILL
MAINTAIN LIGHT WINDS AND MVFR VSBYS IN FOG/HAZE INTO THE
OVERNIGHT...BEFORE A LIGHT WESTERLY WIND AND SOME DRIER AIR
SHOULD ALLOW FOR SOME IMPROVEMENT LATE. IPT AND LNS HAVE BEEN
FLIRTING WITH IFR VSBYS...WHICH MAY CONTINUE FOR THE NEXT FEW
HOURS.
ACROSS THE WESTERN TAF SITES /JST AND BFD/...ANOTHER DISTURBANCE
WILL BRING SCT SHSN INTO THE AREA OVERNIGHT. AN UPSLOPING WNW
FLOW WILL DEVELOP AS WELL...KNOCKING CIGS/VSBYS DOWN WITH
CONTINUED SHSN ACTIVITY.
WNW WINDS WILL BECOME BRISK ON WEDNESDAY...AS THE PRESSURE
GRADIENT TIGHTENS BETWEEN DEEPENING LOW PRES OVER THE CANADIAN
MARITIMES AND HIGH PRES OVER THE SERN US. EASTERN TAF SITES
SHOULD IMPROVE TO GENERALLY VFR CONDS ON WED...IN THE DOWNSLOPING
WNW FLOW. EVEN JST AND BFD WILL EVENTUALLY SEE SOME IMPROVEMENT
/TO AT LEAST MVFR/ AS THE DAY PROGRESSES.
AFTER A QUIET THURS...A DEVELOPING MOIST SOUTHERLY FLOW WILL TURN
THINGS UNSETTLED FRI INTO THIS WEEKEND.
OUTLOOK...
WED...SHSN AND REDUCED CIGS/VSBYS EARLY ACROSS THE WESTERN MTNS
/BFD AND JST/...WITH GRADUAL IMPROVEMENT. BECOMING VFR ELSEWHERE.
THU...GENERALLY VFR.
FRI-SUN...REDUCED CONDS LKLY AS ABUNDANT MOISTURE AND MILDER AIR
STREAMS NEWD AHEAD OF A SLOW-MOVING FRONTAL SYSTEM.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...FITZGERALD
NEAR TERM...FITZGERALD
SHORT TERM...FITZGERALD
LONG TERM...FITZGERALD
AVIATION...EVANEGO
AREA FORECAST DISCUSSION...UPDATED
NWS ABERDEEN SD
1120 AM CST WED DEC 18 2013
.UPDATE...
SEE UPDATED AVIATIION DISCUSSION BELOW.
THE CURRENT FORECAST LOOKS GOOD OVERALL. NO MAJOR CHANGES PLANNED
AT THIS TIME. BASED ON A FEW HI-RES MODELS...LOOKS LIKE
ACCUMULATING SNOWFALL WILL NOT OCCUR UNTIL CLOSER TO 12Z OUT WEST.
VERY DRY AIR IN THE LOWER LEVELS IN THE EASTERN CWA SHOULD KEEP
THIS AREA SNOW FREE UNTIL CLOSER TO 18Z THURSDAY.
&&
.PREVIOUS DISCUSSION...
.SHORT TERM...TODAY THROUGH FRIDAY
VERY GOOD AGREEMENT AMONGST THE MODELS WITH THE UPPER LEVEL AND
SURFACE FEATURES TO AFFECT OUR REGION THROUGH FRIDAY. FOR
TODAY...A SURFACE LOW PRESSURE AREA IN CANADA THIS MORNING WILL
DESCEND SOUTHEAST ALONG A STRONG NORTHWEST TO SOUTHEAST FRONTAL
ZONE BISECTING THE UPPER MIDWEST. TEMPERATURES THROUGH THIS
FRONTAL ZONE EARLY THIS MORNING RANGED FROM THE TEENS BELOW ZERO
IN NORTHEAST MINNESOTA TO 45 TO 50 DEGREES IN SOUTHWEST SOUTH
DAKOTA. THE MUCH COLDER AIR THAT WILL AFFECT OUR REGION IS
SITUATED BEHIND THIS SURFACE LOW PRESSURE AREA IN CANADA EARLY
THIS MORNING. UNTIL THIS MOVES IN TONIGHT...THE CWA WILL
EXPERIENCE ANOTHER ABOVE NORMAL TEMPERATURE/MILD DAY AS THE WARM
FRONT OUT WEST PUSHES EAST IN ADVANCE OF THE SURFACE LOW. SOUTH TO
SOUTHEAST WINDS THIS MORNING WILL TURN WEST AND NORTHWEST THROUGH
THE DAY. THE ISSUE TODAY WILL BE HOW MUCH OF THE WARMER AIR ALOFT
WILL BE REALIZED AT THE SURFACE AS THERE WILL BE A STRONG
INVERSION ACROSS THE CWA. DUE TO THIS INVERSION...THE STRONGER
WEST TO NORTHWEST WINDS OFF THE SURFACE WILL HAVE A HARD TIME
MIXING DOWN. THE SNOW COVER HAS ALSO DIMINISHED SOME ACROSS THE
CWA OVER THE LAST FEW DAYS RANGING GENERALLY FROM 1 TO 4 INCHES.
HIGH RH ON TSCTS AND CLOUDS ON SATELLITE SHOWS THAT THE AREA
SHOULD BE COVERED BY AN EXPANSIVE DECK OF MID AND HIGH LEVEL
CLOUDS THROUGH THE DAY...INHIBITING SURFACE HEATING. TEMPERATURES
EARLY THIS MORNING ACROSS THE CWA WERE ALREADY IN THE UPPER TEENS
TO MID 20S WITH 50S OFF THE SURFACE ACROSS THE CWA. THUS...DO
EXPECT THE REGION TO WARM INTO THE MID 30S TO THE MID 40S WITH
SOME UPPER 40S FAR SOUTHWEST IN THE CWA BY LATE THIS AFTERNOON
MELTING MORE SNOW...ESPECIALLY SOUTHWEST IN THE CWA.
AS THE SURFACE LOW PRESSURE AREA PASSES BY...A STRONG ARCTIC FRONT
WILL DROP ACROSS THE REGION TONIGHT. THIS WILL BRING BLUSTERY
NORTH TO NORTHEAST WINDS ALONG WITH A BIG FALL IN TEMPERATURES
TONIGHT. EXPECT LOWS TONIGHT IN THE SINGLE DIGITS AND LOWER TEENS
ACROSS THE CWA. THURSDAY WILL REMAIN VERY COLD WITH LITTLE IF ANY
RISE IN TEMPERATURES THROUGH THE DAY. THE OTHER ISSUE FOR LATER
TONIGHT THROUGH THURSDAY EVENING WILL BE THE LIGHT SNOW
DEVELOPING. SHORT WAVE ENERGY DROPPING IN FROM THE NORTHWEST ALONG
WITH THE WARM AIR RIDING OVER THE ARCTIC AIR AND RR UPPER LEVEL JET
SUPPORT WILL BRING LIGHT SNOW INTO THE NORTHWEST CWA LATER
TONIGHT. THIS LIGHT SNOW WILL DEVELOP SOUTH AND THEN EAST INTO
THURSDAY. THE BEST CHANCES OF LIGHT SNOW AND DECENT ACCUMULATIONS
WILL REMAIN FROM MOBRIDGE TO PIERRE AND THEN EAST OVER TO MILLER
AND TO WATERTOWN WITH 1 TO 3 INCHES POSSIBLE. WITH DRIER ARCTIC
AIR PUSHING IN ALONG WITH LESS LIFT...THE SNOW AND ACCUMULATIONS
ARE EXPECTED TO BE LIGHTER FROM ABERDEEN TO SISSETON TO WHEATON
MAYBE AN INCH OR LESS. THE OTHER ISSUE WILL BE THE BLUSTERY NORTH
TO NORTHEAST WINDS DEVELOPING WITH THE STRONG CAA AND A TIGHTENING
SURFACE PRESSURE GRADIENT. COULD SEE WINDS OF 20 TO 30 MPH
DEVELOPING WHICH WILL BRING SOME BLOWING SNOW AND FALLING WIND CHILLS.
THE LIGHT SNOW WILL MOVE OUT...WINDS WILL FALL OFF QUICKLY AND
SKIES WILL CLEAR THURSDAY NIGHT AS SURFACE HIGH PRESSURE SETTLES
OVER THE REGION. WITH THE NEW SNOW COVER...LIGHT WINDS AND CLEAR
SKIES...TEMPERATURES WILL FALL TO BELOW ZERO ACROSS ALL OF THE CWA
WITH MAYBE SOME TEENS BELOW ZERO IF CONDITIONS ARE RIGHT. WITH
WINDS TURNING SOUTH BEHIND THE EXITING SURFACE HIGH PRESSURE AREA
ON FRIDAY...TEMPERATURES WILL HAVE A LONG WAY TO GO WITH WEAK
SURFACE WAA. WITH THE NEW SNOW COVER AND MOSTLY SUNNY
SKIES...TEMPERATURES WILL STRUGGLE TO MAKE IT TO 10 DEGREES IN THE
EASTERN CWA WITH 15 TO AROUND 20 DEGREES OUT WEST.
.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
THE PERIOD OPENS WITH AN UPPER TROUGH SITTING OVER THE REGION.
THE UPPER FLOW FLATTENS SLIGHTLY ON MONDAY BEFORE ANOTHER TROF
SHIFTS IN ON TUESDAY. MONDAY NIGHT/TUESDAY MORNING A COLD FRONT
MOVES THROUGH THE PLAINS. EARLY TUESDAY THERE MAY BE ENOUGH MIXING
AHEAD OF THE FRONT TO POP THE TEMPERATURES UP INTO THE 20S...BUT
IF THE GFS TIMING IS CORRECT TEMPS WILL THEN FALL THROUGH THE DAY.
THE ECMWF IS A LITTLE SLOWER AND WOULD GIVE SD A SLIGHTLY LONGER
REPRIEVE FROM THE ANTICIPATED WELL BELOW NORMAL TEMPS FORECAST FOR
THE EXTENDED.
THERE ARE NO WELL DEFINED CHANCES OF PRECIP DURING THE EXTENDED.
SOME CAA SHORTWAVE SNOW SHOWERS ARE POSSIBLE AT VARIOUS TIMES BUT
FORECASTER CONFIDENCE WOULD BE VERY LOW IN TRYING TO PIN DOWN ANY
EXACT TIMING OR LOCATION. THEREFORE STUCK WITH ALLBLEND AND ITS
MOSTLY DRY CONSENSUS.
&&
.AVIATION...
18Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS
VFR CONDITIONS ARE EXPECTED TO PERSIST THROUGH THE REST OF THE
DAYLIGHT HOURS. HOWEVER AN APPROACHING ARCTIC FRONT SHOULD BRING A
MIX OF MVFR/IFR CIGS WITH IT FROM NORTH TO SOUTH OVER THE REGION
TNT.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
UPDATE...SD
SHORT TERM...MOHR
LONG TERM...WISE
AVIATION...TDK
WEATHER.GOV/ABERDEEN
AREA FORECAST DISCUSSION...UPDATED
NWS ABERDEEN SD
530 AM CST WED DEC 18 2013
.UPDATE...
SEE UPDATED AVIATIION DISCUSSION BELOW.
&&
.PREVIOUS DISCUSSION...
.SHORT TERM...TODAY THROUGH FRIDAY
VERY GOOD AGREEMENT AMONGST THE MODELS WITH THE UPPER LEVEL AND
SURFACE FEATURES TO AFFECT OUR REGION THROUGH FRIDAY. FOR
TODAY...A SURFACE LOW PRESSURE AREA IN CANADA THIS MORNING WILL
DESCEND SOUTHEAST ALONG A STRONG NORTHWEST TO SOUTHEAST FRONTAL
ZONE BISECTING THE UPPER MIDWEST. TEMPERATURES THROUGH THIS
FRONTAL ZONE EARLY THIS MORNING RANGED FROM THE TEENS BELOW ZERO
IN NORTHEAST MINNESOTA TO 45 TO 50 DEGREES IN SOUTHWEST SOUTH
DAKOTA. THE MUCH COLDER AIR THAT WILL AFFECT OUR REGION IS
SITUATED BEHIND THIS SURFACE LOW PRESSURE AREA IN CANADA EARLY
THIS MORNING. UNTIL THIS MOVES IN TONIGHT...THE CWA WILL
EXPERIENCE ANOTHER ABOVE NORMAL TEMPERATURE/MILD DAY AS THE WARM
FRONT OUT WEST PUSHES EAST IN ADVANCE OF THE SURFACE LOW. SOUTH TO
SOUTHEAST WINDS THIS MORNING WILL TURN WEST AND NORTHWEST THROUGH
THE DAY. THE ISSUE TODAY WILL BE HOW MUCH OF THE WARMER AIR ALOFT
WILL BE REALIZED AT THE SURFACE AS THERE WILL BE A STRONG
INVERSION ACROSS THE CWA. DUE TO THIS INVERSION...THE STRONGER
WEST TO NORTHWEST WINDS OFF THE SURFACE WILL HAVE A HARD TIME
MIXING DOWN. THE SNOW COVER HAS ALSO DIMINISHED SOME ACROSS THE
CWA OVER THE LAST FEW DAYS RANGING GENERALLY FROM 1 TO 4 INCHES.
HIGH RH ON TSCTS AND CLOUDS ON SATELLITE SHOWS THAT THE AREA
SHOULD BE COVERED BY AN EXPANSIVE DECK OF MID AND HIGH LEVEL
CLOUDS THROUGH THE DAY...INHIBITING SURFACE HEATING. TEMPERATURES
EARLY THIS MORNING ACROSS THE CWA WERE ALREADY IN THE UPPER TEENS
TO MID 20S WITH 50S OFF THE SURFACE ACROSS THE CWA. THUS...DO
EXPECT THE REGION TO WARM INTO THE MID 30S TO THE MID 40S WITH
SOME UPPER 40S FAR SOUTHWEST IN THE CWA BY LATE THIS AFTERNOON
MELTING MORE SNOW...ESPECIALLY SOUTHWEST IN THE CWA.
AS THE SURFACE LOW PRESSURE AREA PASSES BY...A STRONG ARCTIC FRONT
WILL DROP ACROSS THE REGION TONIGHT. THIS WILL BRING BLUSTERY
NORTH TO NORTHEAST WINDS ALONG WITH A BIG FALL IN TEMPERATURES
TONIGHT. EXPECT LOWS TONIGHT IN THE SINGLE DIGITS AND LOWER TEENS
ACROSS THE CWA. THURSDAY WILL REMAIN VERY COLD WITH LITTLE IF ANY
RISE IN TEMPERATURES THROUGH THE DAY. THE OTHER ISSUE FOR LATER
TONIGHT THROUGH THURSDAY EVENING WILL BE THE LIGHT SNOW
DEVELOPING. SHORT WAVE ENERGY DROPPING IN FROM THE NORTHWEST ALONG
WITH THE WARM AIR RIDING OVER THE ARCTIC AIR AND RR UPPER LEVEL JET
SUPPORT WILL BRING LIGHT SNOW INTO THE NORTHWEST CWA LATER
TONIGHT. THIS LIGHT SNOW WILL DEVELOP SOUTH AND THEN EAST INTO
THURSDAY. THE BEST CHANCES OF LIGHT SNOW AND DECENT ACCUMULATIONS
WILL REMAIN FROM MOBRIDGE TO PIERRE AND THEN EAST OVER TO MILLER
AND TO WATERTOWN WITH 1 TO 3 INCHES POSSIBLE. WITH DRIER ARCTIC
AIR PUSHING IN ALONG WITH LESS LIFT...THE SNOW AND ACCUMULATIONS
ARE EXPECTED TO BE LIGHTER FROM ABERDEEN TO SISSETON TO WHEATON
MAYBE AN INCH OR LESS. THE OTHER ISSUE WILL BE THE BLUSTERY NORTH
TO NORTHEAST WINDS DEVELOPING WITH THE STRONG CAA AND A TIGHTENING
SURFACE PRESSURE GRADIENT. COULD SEE WINDS OF 20 TO 30 MPH
DEVELOPING WHICH WILL BRING SOME BLOWING SNOW AND FALLING WIND CHILLS.
THE LIGHT SNOW WILL MOVE OUT...WINDS WILL FALL OFF QUICKLY AND
SKIES WILL CLEAR THURSDAY NIGHT AS SURFACE HIGH PRESSURE SETTLES
OVER THE REGION. WITH THE NEW SNOW COVER...LIGHT WINDS AND CLEAR
SKIES...TEMPERATURES WILL FALL TO BELOW ZERO ACROSS ALL OF THE CWA
WITH MAYBE SOME TEENS BELOW ZERO IF CONDITIONS ARE RIGHT. WITH
WINDS TURNING SOUTH BEHIND THE EXITING SURFACE HIGH PRESSURE AREA
ON FRIDAY...TEMPERATURES WILL HAVE A LONG WAY TO GO WITH WEAK
SURFACE WAA. WITH THE NEW SNOW COVER AND MOSTLY SUNNY
SKIES...TEMPERATURES WILL STRUGGLE TO MAKE IT TO 10 DEGREES IN THE
EASTERN CWA WITH 15 TO AROUND 20 DEGREES OUT WEST.
.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
THE PERIOD OPENS WITH AN UPPER TROUGH SITTING OVER THE REGION.
THE UPPER FLOW FLATTENS SLIGHTLY ON MONDAY BEFORE ANOTHER TROF
SHIFTS IN ON TUESDAY. MONDAY NIGHT/TUESDAY MORNING A COLD FRONT
MOVES THROUGH THE PLAINS. EARLY TUESDAY THERE MAY BE ENOUGH MIXING
AHEAD OF THE FRONT TO POP THE TEMPERATURES UP INTO THE 20S...BUT
IF THE GFS TIMING IS CORRECT TEMPS WILL THEN FALL THROUGH THE DAY.
THE ECMWF IS A LITTLE SLOWER AND WOULD GIVE SD A SLIGHTLY LONGER
REPRIEVE FROM THE ANTICIPATED WELL BELOW NORMAL TEMPS FORECAST FOR
THE EXTENDED.
THERE ARE NO WELL DEFINED CHANCES OF PRECIP DURING THE EXTENDED.
SOME CAA SHORTWAVE SNOW SHOWERS ARE POSSIBLE AT VARIOUS TIMES BUT
FORECASTER CONFIDENCE WOULD BE VERY LOW IN TRYING TO PIN DOWN ANY
EXACT TIMING OR LOCATION. THEREFORE STUCK WITH ALLBLEND AND ITS
MOSTLY DRY CONSENSUS.
&&
.AVIATION...
12Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS
VFR CONDITIONS WILL PREVAIL ACROSS THE AREA THROUGH THIS EVENING.
AN ARCTIC FRONT WILL BEGIN TO PUSH INTO THE REGION THIS EVENING.
WINDS WILL SHIFT TO THE NORTH AND INCREASE TO 15 TO 25 KTS. AROUND
MIDNIGHT CIGS WILL BEGIN TO LOWER TO MVFR.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
UPDATE...WISE
SHORT TERM...MOHR
LONG TERM...WISE
AVIATION...WISE
WEATHER.GOV/ABERDEEN
AREA FORECAST DISCUSSION
NWS ABERDEEN SD
333 AM CST WED DEC 18 2013
.SHORT TERM...TODAY THROUGH FRIDAY
VERY GOOD AGREEMENT AMONGST THE MODELS WITH THE UPPER LEVEL AND
SURFACE FEATURES TO AFFECT OUR REGION THROUGH FRIDAY. FOR
TODAY...A SURFACE LOW PRESSURE AREA IN CANADA THIS MORNING WILL
DESCEND SOUTHEAST ALONG A STRONG NORTHWEST TO SOUTHEAST FRONTAL
ZONE BISECTING THE UPPER MIDWEST. TEMPERATURES THROUGH THIS
FRONTAL ZONE EARLY THIS MORNING RANGED FROM THE TEENS BELOW ZERO
IN NORTHEAST MINNESOTA TO 45 TO 50 DEGREES IN SOUTHWEST SOUTH
DAKOTA. THE MUCH COLDER AIR THAT WILL AFFECT OUR REGION IS
SITUATED BEHIND THIS SURFACE LOW PRESSURE AREA IN CANADA EARLY
THIS MORNING. UNTIL THIS MOVES IN TONIGHT...THE CWA WILL
EXPERIENCE ANOTHER ABOVE NORMAL TEMPERATURE/MILD DAY AS THE WARM
FRONT OUT WEST PUSHES EAST IN ADVANCE OF THE SURFACE LOW. SOUTH TO
SOUTHEAST WINDS THIS MORNING WILL TURN WEST AND NORTHWEST THROUGH
THE DAY. THE ISSUE TODAY WILL BE HOW MUCH OF THE WARMER AIR ALOFT
WILL BE REALIZED AT THE SURFACE AS THERE WILL BE A STRONG
INVERSION ACROSS THE CWA. DUE TO THIS INVERSION...THE STRONGER
WEST TO NORTHWEST WINDS OFF THE SURFACE WILL HAVE A HARD TIME
MIXING DOWN. THE SNOW COVER HAS ALSO DIMINISHED SOME ACROSS THE
CWA OVER THE LAST FEW DAYS RANGING GENERALLY FROM 1 TO 4 INCHES.
HIGH RH ON TSCTS AND CLOUDS ON SATELLITE SHOWS THAT THE AREA
SHOULD BE COVERED BY AN EXPANSIVE DECK OF MID AND HIGH LEVEL
CLOUDS THROUGH THE DAY...INHIBITING SURFACE HEATING. TEMPERATURES
EARLY THIS MORNING ACROSS THE CWA WERE ALREADY IN THE UPPER TEENS
TO MID 20S WITH 50S OFF THE SURFACE ACROSS THE CWA. THUS...DO
EXPECT THE REGION TO WARM INTO THE MID 30S TO THE MID 40S WITH
SOME UPPER 40S FAR SOUTHWEST IN THE CWA BY LATE THIS AFTERNOON
MELTING MORE SNOW...ESPECIALLY SOUTHWEST IN THE CWA.
AS THE SURFACE LOW PRESSURE AREA PASSES BY...A STRONG ARCTIC FRONT
WILL DROP ACROSS THE REGION TONIGHT. THIS WILL BRING BLUSTERY
NORTH TO NORTHEAST WINDS ALONG WITH A BIG FALL IN TEMPERATURES
TONIGHT. EXPECT LOWS TONIGHT IN THE SINGLE DIGITS AND LOWER TEENS
ACROSS THE CWA. THURSDAY WILL REMAIN VERY COLD WITH LITTLE IF ANY
RISE IN TEMPERATURES THROUGH THE DAY. THE OTHER ISSUE FOR LATER
TONIGHT THROUGH THURSDAY EVENING WILL BE THE LIGHT SNOW
DEVELOPING. SHORT WAVE ENERGY DROPPING IN FROM THE NORTHWEST ALONG
WITH THE WARM AIR RIDING OVER THE ARCTIC AIR AND RR UPPER LEVEL JET
SUPPORT WILL BRING LIGHT SNOW INTO THE NORTHWEST CWA LATER
TONIGHT. THIS LIGHT SNOW WILL DEVELOP SOUTH AND THEN EAST INTO
THURSDAY. THE BEST CHANCES OF LIGHT SNOW AND DECENT ACCUMULATIONS
WILL REMAIN FROM MOBRIDGE TO PIERRE AND THEN EAST OVER TO MILLER
AND TO WATERTOWN WITH 1 TO 3 INCHES POSSIBLE. WITH DRIER ARCTIC
AIR PUSHING IN ALONG WITH LESS LIFT...THE SNOW AND ACCUMULATIONS
ARE EXPECTED TO BE LIGHTER FROM ABERDEEN TO SISSETON TO WHEATON
MAYBE AN INCH OR LESS. THE OTHER ISSUE WILL BE THE BLUSTERY NORTH
TO NORTHEAST WINDS DEVELOPING WITH THE STRONG CAA AND A TIGHTENING
SURFACE PRESSURE GRADIENT. COULD SEE WINDS OF 20 TO 30 MPH
DEVELOPING WHICH WILL BRING SOME BLOWING SNOW AND FALLING WIND CHILLS.
THE LIGHT SNOW WILL MOVE OUT...WINDS WILL FALL OFF QUICKLY AND
SKIES WILL CLEAR THURSDAY NIGHT AS SURFACE HIGH PRESSURE SETTLES
OVER THE REGION. WITH THE NEW SNOW COVER...LIGHT WINDS AND CLEAR
SKIES...TEMPERATURES WILL FALL TO BELOW ZERO ACROSS ALL OF THE CWA
WITH MAYBE SOME TEENS BELOW ZERO IF CONDITIONS ARE RIGHT. WITH
WINDS TURNING SOUTH BEHIND THE EXITING SURFACE HIGH PRESSURE AREA
ON FRIDAY...TEMPERATURES WILL HAVE A LONG WAY TO GO WITH WEAK
SURFACE WAA. WITH THE NEW SNOW COVER AND MOSTLY SUNNY
SKIES...TEMPERATURES WILL STRUGGLE TO MAKE IT TO 10 DEGREES IN THE
EASTERN CWA WITH 15 TO AROUND 20 DEGREES OUT WEST.
.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
THE PERIOD OPENS WITH AN UPPER TROUGH SITTING OVER THE REGION.
THE UPPER FLOW FLATTENS SLIGHTLY ON MONDAY BEFORE ANOTHER TROF
SHIFTS IN ON TUESDAY. MONDAY NIGHT/TUESDAY MORNING A COLD FRONT
MOVES THROUGH THE PLAINS. EARLY TUESDAY THERE MAY BE ENOUGH MIXING
AHEAD OF THE FRONT TO POP THE TEMPERATURES UP INTO THE 20S...BUT
IF THE GFS TIMING IS CORRECT TEMPS WILL THEN FALL THROUGH THE DAY.
THE ECMWF IS A LITTLE SLOWER AND WOULD GIVE SD A SLIGHTLY LONGER
REPRIEVE FROM THE ANTICIPATED WELL BELOW NORMAL TEMPS FORECAST FOR
THE EXTENDED.
THERE ARE NO WELL DEFINED CHANCES OF PRECIP DURING THE EXTENDED.
SOME CAA SHORTWAVE SNOW SHOWERS ARE POSSIBLE AT VARIOUS TIMES BUT
FORECASTER CONFIDENCE WOULD BE VERY LOW IN TRYING TO PIN DOWN ANY
EXACT TIMING OR LOCATION. THEREFORE STUCK WITH ALLBLEND AND ITS
MOSTLY DRY CONSENSUS.
&&
.AVIATION...
06Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS
VFR CONDITIONS WILL PREVAIL ACROSS THE AREA OVERNIGHT AND THROUGH
THE DAY WEDNESDAY.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
SHORT TERM...MOHR
LONG TERM...WISE
AVIATION...PARKIN
WEATHER.GOV/ABERDEEN
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
926 PM CST THU DEC 19 2013
.UPDATE...
ISSUED AT 926 PM CST THU DEC 19 2013
RADAR/OBSERVATION TRENDS CONTINUE TO SHOW THE BAND OF FREEZING
DRIZZLE SURGING NORTHWARD ACROSS SOUTHEAST MINNESOTA AND WESTERN
WISCONSIN. WILL BE ADDING SOME COUNTIES TO THE FREEZING RAIN
ADVISORY...LIKELY THE REST OF THE FORECAST AREA EXCEPT
CLARK/TAYLOR COUNTIES WHERE ICE APPEARS TO BE IN FOR THE FULL
SATURATED COLUMN. ROADS HAVE ICED UP ACROSS SOUTHWEST WISCONSIN
AND NORTHEAST IOWA WHERE THE FREEZING DRIZZLE/RAIN HAS PERSISTED.
UPDATE COMING SHORTLY.
&&
.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 307 PM CST THU DEC 19 2013
AS OF MID AFTERNOON THURSDAY...AREA OF LOW PRESSURE SITUATED IN
NORTHEAST KANSAS WITH WARM FRONT EXTENDING NORTHEAST INTO SOUTHERN
IOWA AND NORTHERN ILLINOIS. INCREASING ISENTROPIC LIFT LATER THIS
EVENING AND MOISTURE TRANSPORT OVERRUNNING THE WARM FRONT WILL
SATURATE THE LOW LEVELS...ESPECIALLY AFTER 00Z. FORECAST SOUNDINGS
STILL SHOW A COMPLICATED TOP DOWN PRECIPITATION TYPE SCENARIO WITH
BOTH A WARM NOSE AND A LOSS OF ICE IN THE UPPER LEVELS. FIRST...THE
PROBABILITY OF NO ICE PRESENT SHIFTED SLIGHTLY NORTH FROM
PREVIOUS FORECAST. 19.12Z NAM AND RAP NOW SHOW THIS EXTENDING NORTH
TO JUST SHY OF THE I-90 CORRIDOR IN WISCONSIN. IT IS NOT UNTIL VERY
EARLY FRIDAY MORNING THAT ICE GETS REINTRODUCED...AND A CHANGEOVER
TO LIGHT SNOW WOULD THEN OCCUR FOR PLACES SUCH AS VIROQUA OVER TO
JUNEAU/ADAMS COUNTIES. AT THE SAME TIME...RAP SOUNDINGS FOR DBQ
SHOW MAX WARM NOSE OF +4 DEGREES...AROUND +1 FOR BLR...AND THEN
BELOW ZERO FOR AREAS TO THE NORTH. SO...TIGHT GRADIENT FOR
FREEZING RAIN AND SNOW LINE. AS FAR AS ICE ACCUMULATIONS...UP TO
1/10 OF AN INCH STILL EXPECTED ON EXPOSED SURFACES...WHICH WILL
MAKE FOR SLICK TRAVEL OVERNIGHT INTO THE MORNING HOURS FRIDAY.
GIVEN THIS NORTHWARD JOG IN THE LOSS OF ICE / WARM NOSE...HAVE
EXPANDED THE FREEZING RAIN ADVISORY TO INCLUDE VERNON...JUNEAU AND
ADAMS COUNTIES IN WISCONSIN.
THE NORTHERN SIDE OF THIS WEATHER SYSTEM STILL EXPECTED TO PRODUCE A
BAND OF ACCUMULATING SNOW ALONG AND NORTH OF I-90...MAINLY AFTER
MIDNIGHT INTO FRIDAY MORNING. NO BIG CHANGES FROM
PREVIOUS FORECAST...WITH 1 TO 2 INCHES FOR MOST LOCATIONS AND
LOCALLY 3 INCH AMOUNTS POSSIBLE MAINLY FOR CENTRAL WISCONSIN. THIS
TOO COULD MAKE FOR SLICK ROADWAYS FOR THE FRIDAY MORNING
COMMUTE...AND CONSIDERED A HEADLINE FOR THIS BUT WILL HOLD OFF NOW
GIVEN COLLABORATION. IF LATER FORECASTS SHOW AN UPTICK IN
AMOUNTS...OR A DELAY MORE TOWARD THE MORNING COMMUTE...THEN AN
WINTER WEATHER ADVISORY MAY BE NEEDED FOR A FEW COUNTIES.
.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 307 PM CST THU DEC 19 2013
FOCUS OF THIS PERIOD IS SQUARELY ON THE WEEKEND AND THE POTENTIAL
FOR A WINTER STORM TO IMPACT PARTS OF THE FORECAST AREA. STILL
SOME DIFFERENCES BETWEEN THE MODELS BUT THE 19.12Z GFS AND ECMWF
ARE IN BETTER AGREEMENT WITH THE OVERALL PATTERN WITH THE 19.12Z
NAM APPEARING AT THIS TIME TO BE THE ODD MODEL OUT. THE UPPER
LEVEL LOW CURRENTLY ALONG THE CALIFORNIA COAST WILL MOVE OUT OF
THE DESERT SOUTHWEST AND TRACK NORTHEAST ACROSS THE CENTRAL
PORTION OF THE COUNTRY OVER THE WEEKEND. AS IT MOVES TOWARD THE
AREA...A NORTHERN STREAM SHORT WAVE WILL START TO MOVE TOWARD THE
UPPER MIDWEST FROM SOUTHWEST CANADA. THE DIFFERENCES IN THE MODEL
SOLUTIONS REVOLVE AROUND WHETHER THESE TWO SYSTEMS GET PHASED OR
WHETHER THEY STAY SEPARATE. THE NAM WOULD SUGGEST THEY GET PHASED
WHICH PUSHES THE SURFACE LOW AND ASSOCIATED QPF FARTHER SOUTHEAST.
THE GFS AND ECMWF DO NOT PHASE THE TWO SYSTEMS WHICH BRINGS THE
SURFACE LOW AND QPF BACK MORE TO THE NORTHWEST.
THE FORCING FROM THE SHORT WAVE TROUGH WILL START TO MOVE IN
SATURDAY NIGHT. MODERATE TO STRONG PV ADVECTION IN THE 500-300 MB
LAYER SHOULD OCCUR LATE SATURDAY NIGHT JUST AHEAD OF THE WAVES
PASSAGE. MODERATE TO STRONG QG CONVERGENCE WILL BE PRODUCED BY THE
WAVE AND CENTERED OVER THE SOUTHEAST PART OF THE FORECAST AREA AT
12Z SUNDAY. WEAK TO MODERATE FRONTOGENESIS IS SHOWN BY THE GFS IN
THE 600-500 MB LAYER BETWEEN 06Z AND 18Z SUNDAY...ALSO OVER THE
SOUTHEAST PORTIONS OF THE FORECAST AREA. THERE MAY ALSO BE SOME
JET DYNAMICS THAT COME INTO PLAY AS WELL. THE GFS IS SUGGESTING A
SPLIT JET WITH THE AREA UNDER THE RIGHT ENTRANCE REGION OF THE
NORTHERN STREAM JET CORE TO ADD SOME AGEOSTROPHIC LIFT TO THE MIX.
THE GFS BUFKIT SOUNDING FOR BLUE RIVER SUGGEST THE DENDRITIC
GROWTH ZONE SHOULD BE ABOUT 100 MB DEEP WITH GOOD VERTICAL MOTIONS
THROUGH IT. THIS SHOULD LEAD TO SNOW RATIOS IN THE 14-16 TO 1
RANGE LEADING TO SNOW ACCUMULATIONS OF 4 TO 7 INCHES FROM ABOUT
FAYETTE COUNTY IOWA NORTHEAST INTO ADAMS/JUNEAU COUNTIES IN
CENTRAL WISCONSIN. THE POTENTIAL FOR THE HIGHER AMOUNTS IS THE
GREATEST IN PRIMARILY GRANT COUNTY WISCONSIN. THE NORTHWEST WINDS
WILL COME UP SUNDAY ON THE BACK SIDE OF THE SYSTEM WHICH WILL
LIKELY LEAD TO SOME DRIFTING SNOW AND POSSIBLY A LITTLE BLOWING
SNOW OVER THE MORE OPEN AREAS OF NORTHEAST IOWA. IN COORDINATION
WITH SURROUNDING OFFICES...WILL ISSUE A WINTER STORM WATCH FOR
SATURDAY NIGHT AND SUNDAY FOR THE ACCUMULATING SNOW AND ANY
POSSIBLE IMPACT ON THE BACK SIDE OF THE SYSTEM.
WITH THE FOCUS ON THE WEEKEND SYSTEM...HAVE NOT LOOKED EXTENSIVELY
AT THE FORECAST FOR NEXT WEEK. HAVE LET THE MODEL CONSENSUS GRIDS
RIDE WHICH GIVES A SMALL CHANCE FOR SOME SNOW TUESDAY AND TUESDAY
NIGHT ACROSS THE NORTH AS ANOTHER NORTHERN STREAM SHORT WAVE
TROUGH MOVES ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION. THE
COLDEST TEMPERATURES IN THE FORECAST LOOK TO BE BEHIND THE WEEKEND
SYSTEM WITH LOWS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO SUNDAY
NIGHT...HIGHS ONLY IN THE SINGLE DIGITS ABOVE ZERO MONDAY WITH
SINGLE DIGITS BELOW ZERO FOR THE ENTIRE AREA MONDAY NIGHT.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 552 PM CST THU DEC 19 2013
MVFR CEILINGS ARE ALREADY IN PLACE THROUGHOUT THE REGION WITH
FLIGHT CONDITIONS ONLY EXPECTED TO WORSEN THROUGH THE NIGHT.
DRIZZLE IS BECOMING MORE WIDESPREAD AND DEVELOPING NORTHWARD
ACROSS IOWA. THE QUESTION IS WITH WHETHER THIS DRIZZLE MAKES IT
INTO LSE/RST OR IF THE LOW LEVELS WILL BE COLD ENOUGH TO CAUSE IT
TO BE SNOW. TEMPERATURES AT THE GROUND WILL BE BELOW FREEZING...SO
ANY DRIZZLE THAT DOES OCCUR WILL BE FREEZING ON CONTACT WITH IT.
CEILINGS ARE EXPECTED TO GO IFR OVERNIGHT WITH VISIBILITY POSSIBLY
GOING DOWN WITH IT AS WELL. PRECIPITATION IS EXPECTED TO CHANGE
OVER TO SNOW FOR AT LEAST A PERIOD ON THE TAIL END OF THE SYSTEM
GOING INTO TOMORROW MORNING. CEILINGS ARE EXPECTED TO STAY AT
LEAST MVFR THROUGH MUCH OF TOMORROW WITH THE RIDGE OF HIGH
PRESSURE NOT MAKING IT IN UNTIL LATER FRIDAY NIGHT.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR WIZ041>044-
053>055-061.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ043-044-053>055-061.
MN...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR MNZ095-096.
IA...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR IAZ009>011-018-
019-029-030.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR IAZ011-029-030.
&&
$$
UPDATE...HALBACH
SHORT TERM...ZT
LONG TERM...04
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
818 PM CST THU DEC 19 2013
.UPDATE...
ISSUED AT 818 PM CST THU DEC 19 2013
FREEZING RAIN AND DRIZZLE HAS DEVELOPED ACROSS NORTHEAST IOWA AND
SOUTHWEST WISCONSIN AND IS PUSHING NORTHWARD. AS OF
8PM...REFLECTIVITY AND CORRELATION COEFFICIENT OFF OF KARX
SUGGESTS THAT THE LEADING EDGE OF THE DRIZZLE RUNS FROM SOUTHEAST
MONROE COUNTY TOWARD VIROQUA WISCONSIN SOUTHWEST TOWARD DECORAH
AND NEW HAMPTON IOWA. WITH 19.23Z RAP SOUNDINGS CONTINUING TO SHOW
FREEZING DRIZZLE/RAIN AS THE MAIN PRECIPITATION TYPE WITH THE DRY
LAYER BETWEEN 800-600MB BEING TOO DEEP FOR SEEDER-FEEDER TO WORK
AND PRODUCE SNOW AT THE GROUND. BECAUSE OF THIS...HAVE EXTENDED
THE ADVISORY TO THE NORTH A TIER OF COUNTIES AND ALSO EXTENDED THE
END TIME UNTIL 9 AM TOMORROW MORNING SINCE THE LOSS OF ICE SEEMS
TO CONTINUE THROUGH MUCH OF THE MORNING. THE PERIOD OF MAIN
CONCERN IS FROM NOW THROUGH ABOUT 3 OR 4 AM WHEN IT APPEARS THAT
THE MOST ICING WILL OCCUR.
FURTHER NORTHWEST...THERE HAS NOT BEEN MUCH IN THE WAY OF SNOW
BEING REPORTED UNTIL YOU GET TO ST. CLOUD MINNESOTA AND TRENDS
CONTINUE TO SUPPORT THAT THE MAIN BAND OF SNOW WILL LIKELY STAY IN
NORTHWEST WISCONSIN AND ALSO DIMINISH IN INTENSITY THROUGH THE
OVERNIGHT HOURS. BECAUSE OF THIS AND THE POSSIBILITY OF MORE
FREEZING RAIN/DRIZZLE OCCURRING...HAVE KNOCKED BACK SNOW TOTALS TO
GENERALLY BEING AROUND AN INCH WITH LESSER AMOUNTS AS YOU GO
TOWARD IOWA/CENTRAL WISCONSIN.
&&
.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 307 PM CST THU DEC 19 2013
AS OF MID AFTERNOON THURSDAY...AREA OF LOW PRESSURE SITUATED IN
NORTHEAST KANSAS WITH WARM FRONT EXTENDING NORTHEAST INTO SOUTHERN
IOWA AND NORTHERN ILLINOIS. INCREASING ISENTROPIC LIFT LATER THIS
EVENING AND MOISTURE TRANSPORT OVERRUNNING THE WARM FRONT WILL
SATURATE THE LOW LEVELS...ESPECIALLY AFTER 00Z. FORECAST SOUNDINGS
STILL SHOW A COMPLICATED TOP DOWN PRECIPITATION TYPE SCENARIO WITH
BOTH A WARM NOSE AND A LOSS OF ICE IN THE UPPER LEVELS. FIRST...THE
PROBABILITY OF NO ICE PRESENT SHIFTED SLIGHTLY NORTH FROM
PREVIOUS FORECAST. 19.12Z NAM AND RAP NOW SHOW THIS EXTENDING NORTH
TO JUST SHY OF THE I-90 CORRIDOR IN WISCONSIN. IT IS NOT UNTIL VERY
EARLY FRIDAY MORNING THAT ICE GETS REINTRODUCED...AND A CHANGEOVER
TO LIGHT SNOW WOULD THEN OCCUR FOR PLACES SUCH AS VIROQUA OVER TO
JUNEAU/ADAMS COUNTIES. AT THE SAME TIME...RAP SOUNDINGS FOR DBQ
SHOW MAX WARM NOSE OF +4 DEGREES...AROUND +1 FOR BLR...AND THEN
BELOW ZERO FOR AREAS TO THE NORTH. SO...TIGHT GRADIENT FOR
FREEZING RAIN AND SNOW LINE. AS FAR AS ICE ACCUMULATIONS...UP TO
1/10 OF AN INCH STILL EXPECTED ON EXPOSED SURFACES...WHICH WILL
MAKE FOR SLICK TRAVEL OVERNIGHT INTO THE MORNING HOURS FRIDAY.
GIVEN THIS NORTHWARD JOG IN THE LOSS OF ICE / WARM NOSE...HAVE
EXPANDED THE FREEZING RAIN ADVISORY TO INCLUDE VERNON...JUNEAU AND
ADAMS COUNTIES IN WISCONSIN.
THE NORTHERN SIDE OF THIS WEATHER SYSTEM STILL EXPECTED TO PRODUCE A
BAND OF ACCUMULATING SNOW ALONG AND NORTH OF I-90...MAINLY AFTER
MIDNIGHT INTO FRIDAY MORNING. NO BIG CHANGES FROM
PREVIOUS FORECAST...WITH 1 TO 2 INCHES FOR MOST LOCATIONS AND
LOCALLY 3 INCH AMOUNTS POSSIBLE MAINLY FOR CENTRAL WISCONSIN. THIS
TOO COULD MAKE FOR SLICK ROADWAYS FOR THE FRIDAY MORNING
COMMUTE...AND CONSIDERED A HEADLINE FOR THIS BUT WILL HOLD OFF NOW
GIVEN COLLABORATION. IF LATER FORECASTS SHOW AN UPTICK IN
AMOUNTS...OR A DELAY MORE TOWARD THE MORNING COMMUTE...THEN AN
WINTER WEATHER ADVISORY MAY BE NEEDED FOR A FEW COUNTIES.
.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 307 PM CST THU DEC 19 2013
FOCUS OF THIS PERIOD IS SQUARELY ON THE WEEKEND AND THE POTENTIAL
FOR A WINTER STORM TO IMPACT PARTS OF THE FORECAST AREA. STILL
SOME DIFFERENCES BETWEEN THE MODELS BUT THE 19.12Z GFS AND ECMWF
ARE IN BETTER AGREEMENT WITH THE OVERALL PATTERN WITH THE 19.12Z
NAM APPEARING AT THIS TIME TO BE THE ODD MODEL OUT. THE UPPER
LEVEL LOW CURRENTLY ALONG THE CALIFORNIA COAST WILL MOVE OUT OF
THE DESERT SOUTHWEST AND TRACK NORTHEAST ACROSS THE CENTRAL
PORTION OF THE COUNTRY OVER THE WEEKEND. AS IT MOVES TOWARD THE
AREA...A NORTHERN STREAM SHORT WAVE WILL START TO MOVE TOWARD THE
UPPER MIDWEST FROM SOUTHWEST CANADA. THE DIFFERENCES IN THE MODEL
SOLUTIONS REVOLVE AROUND WHETHER THESE TWO SYSTEMS GET PHASED OR
WHETHER THEY STAY SEPARATE. THE NAM WOULD SUGGEST THEY GET PHASED
WHICH PUSHES THE SURFACE LOW AND ASSOCIATED QPF FARTHER SOUTHEAST.
THE GFS AND ECMWF DO NOT PHASE THE TWO SYSTEMS WHICH BRINGS THE
SURFACE LOW AND QPF BACK MORE TO THE NORTHWEST.
THE FORCING FROM THE SHORT WAVE TROUGH WILL START TO MOVE IN
SATURDAY NIGHT. MODERATE TO STRONG PV ADVECTION IN THE 500-300 MB
LAYER SHOULD OCCUR LATE SATURDAY NIGHT JUST AHEAD OF THE WAVES
PASSAGE. MODERATE TO STRONG QG CONVERGENCE WILL BE PRODUCED BY THE
WAVE AND CENTERED OVER THE SOUTHEAST PART OF THE FORECAST AREA AT
12Z SUNDAY. WEAK TO MODERATE FRONTOGENESIS IS SHOWN BY THE GFS IN
THE 600-500 MB LAYER BETWEEN 06Z AND 18Z SUNDAY...ALSO OVER THE
SOUTHEAST PORTIONS OF THE FORECAST AREA. THERE MAY ALSO BE SOME
JET DYNAMICS THAT COME INTO PLAY AS WELL. THE GFS IS SUGGESTING A
SPLIT JET WITH THE AREA UNDER THE RIGHT ENTRANCE REGION OF THE
NORTHERN STREAM JET CORE TO ADD SOME AGEOSTROPHIC LIFT TO THE MIX.
THE GFS BUFKIT SOUNDING FOR BLUE RIVER SUGGEST THE DENDRITIC
GROWTH ZONE SHOULD BE ABOUT 100 MB DEEP WITH GOOD VERTICAL MOTIONS
THROUGH IT. THIS SHOULD LEAD TO SNOW RATIOS IN THE 14-16 TO 1
RANGE LEADING TO SNOW ACCUMULATIONS OF 4 TO 7 INCHES FROM ABOUT
FAYETTE COUNTY IOWA NORTHEAST INTO ADAMS/JUNEAU COUNTIES IN
CENTRAL WISCONSIN. THE POTENTIAL FOR THE HIGHER AMOUNTS IS THE
GREATEST IN PRIMARILY GRANT COUNTY WISCONSIN. THE NORTHWEST WINDS
WILL COME UP SUNDAY ON THE BACK SIDE OF THE SYSTEM WHICH WILL
LIKELY LEAD TO SOME DRIFTING SNOW AND POSSIBLY A LITTLE BLOWING
SNOW OVER THE MORE OPEN AREAS OF NORTHEAST IOWA. IN COORDINATION
WITH SURROUNDING OFFICES...WILL ISSUE A WINTER STORM WATCH FOR
SATURDAY NIGHT AND SUNDAY FOR THE ACCUMULATING SNOW AND ANY
POSSIBLE IMPACT ON THE BACK SIDE OF THE SYSTEM.
WITH THE FOCUS ON THE WEEKEND SYSTEM...HAVE NOT LOOKED EXTENSIVELY
AT THE FORECAST FOR NEXT WEEK. HAVE LET THE MODEL CONSENSUS GRIDS
RIDE WHICH GIVES A SMALL CHANCE FOR SOME SNOW TUESDAY AND TUESDAY
NIGHT ACROSS THE NORTH AS ANOTHER NORTHERN STREAM SHORT WAVE
TROUGH MOVES ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION. THE
COLDEST TEMPERATURES IN THE FORECAST LOOK TO BE BEHIND THE WEEKEND
SYSTEM WITH LOWS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO SUNDAY
NIGHT...HIGHS ONLY IN THE SINGLE DIGITS ABOVE ZERO MONDAY WITH
SINGLE DIGITS BELOW ZERO FOR THE ENTIRE AREA MONDAY NIGHT.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 552 PM CST THU DEC 19 2013
MVFR CEILINGS ARE ALREADY IN PLACE THROUGHOUT THE REGION WITH
FLIGHT CONDITIONS ONLY EXPECTED TO WORSEN THROUGH THE NIGHT.
DRIZZLE IS BECOMING MORE WIDESPREAD AND DEVELOPING NORTHWARD
ACROSS IOWA. THE QUESTION IS WITH WHETHER THIS DRIZZLE MAKES IT
INTO LSE/RST OR IF THE LOW LEVELS WILL BE COLD ENOUGH TO CAUSE IT
TO BE SNOW. TEMPERATURES AT THE GROUND WILL BE BELOW FREEZING...SO
ANY DRIZZLE THAT DOES OCCUR WILL BE FREEZING ON CONTACT WITH IT.
CEILINGS ARE EXPECTED TO GO IFR OVERNIGHT WITH VISIBILITY POSSIBLY
GOING DOWN WITH IT AS WELL. PRECIPITATION IS EXPECTED TO CHANGE
OVER TO SNOW FOR AT LEAST A PERIOD ON THE TAIL END OF THE SYSTEM
GOING INTO TOMORROW MORNING. CEILINGS ARE EXPECTED TO STAY AT
LEAST MVFR THROUGH MUCH OF TOMORROW WITH THE RIDGE OF HIGH
PRESSURE NOT MAKING IT IN UNTIL LATER FRIDAY NIGHT.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR WIZ041>044-
053>055-061.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ043-044-053>055-061.
MN...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR MNZ095-096.
IA...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR IAZ009>011-018-
019-029-030.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR IAZ011-029-030.
&&
$$
UPDATE...HALBACH
SHORT TERM...ZT
LONG TERM...04
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
552 PM CST THU DEC 19 2013
.UPDATE...
ISSUED AT 552 PM CST THU DEC 19 2013
WITH LOW LEVEL MOISTURE TRANSPORT INCREASING ACROSS IOWA...SOME
DRIZZLE HAS BECOME MORE WIDESPREAD PER OBSERVATIONS/RADAR ACROSS
THE SOUTHERN HALF OF IOWA. THE NORTHERN EDGE OF THIS DRIZZLE IS ON
THE DOORSTEP TO NORTHEAST IOWA AND WILL CONTINUE TO ADVANCE
NORTHWARD THROUGH THE EVENING.
CONFIDENCE IS STILL HIGH THAT THE AREAS CURRENTLY IN THE FREEZING
RAIN ADVISORY WILL SEE THE FREEZING RAIN/DRIZZLE. THE QUESTION IS
WHETHER AREAS TO THE NORTHWEST WILL NEED TO BE ADDED THIS EVENING.
19.22Z RAP SOUNDINGS FROM LSE TO RST SHOW THE LOW LEVELS
SATURATING OUT OVER THE NEXT FEW HOURS WITH TEMPERATURES IN THAT
LAYER AROUND -5 TO -10C WITH AREAS FURTHER TO THE NORTHWEST CLOSER
TO -10C. THAT AREA COULD BE COLD ENOUGH THAT ICE WILL BE
INTRODUCED AND THE PRECIPITATION FALLS AS SNOW...BUT IT REALLY IS
BORDERLINE. THE 19.21Z HRRR REFLECTIVITY GRAPHIC DOES HINT THAT IT
IS MAINLY DRIZZLE/RAIN IN NORTHEAST IOWA/SOUTHWEST WISCONSIN WITH
SNOW DEVELOPING ALONG THE NORTHWEST SIDE OF THIS PRECIPITATION
SHIELD. WILL BE MONITORING TRENDS OVER THE NEXT FEW HOURS WITH
THE FOCUS ON WHETHER THE ADVISORY NEEDS TO GO NORTHWEST OR IF WE
ARE OKAY WITH WHERE WE ARE AT..
ALSO...THE MAIN SNOW BAND ASSOCIATED WITH THE TROUGH IN THE
DAKOTAS APPEARS TO BE TRACKING NORTHWEST OF THE AREA AND IF THE
MAIN P-TYPE IS MORE FREEZING DRIZZLE THAN SNOW...THEN THE 1 TO 3
INCHES IS PROBABLY OVER DONE. MAY BE MAKING ADJUSTMENTS TO THAT
FORECAST AS WELL THIS EVENING.
&&
.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 307 PM CST THU DEC 19 2013
AS OF MID AFTERNOON THURSDAY...AREA OF LOW PRESSURE SITUATED IN
NORTHEAST KANSAS WITH WARM FRONT EXTENDING NORTHEAST INTO SOUTHERN
IOWA AND NORTHERN ILLINOIS. INCREASING ISENTROPIC LIFT LATER THIS
EVENING AND MOISTURE TRANSPORT OVERRUNNING THE WARM FRONT WILL
SATURATE THE LOW LEVELS...ESPECIALLY AFTER 00Z. FORECAST SOUNDINGS
STILL SHOW A COMPLICATED TOP DOWN PRECIPITATION TYPE SCENARIO WITH
BOTH A WARM NOSE AND A LOSS OF ICE IN THE UPPER LEVELS. FIRST...THE
PROBABILITY OF NO ICE PRESENT SHIFTED SLIGHTLY NORTH FROM
PREVIOUS FORECAST. 19.12Z NAM AND RAP NOW SHOW THIS EXTENDING NORTH
TO JUST SHY OF THE I-90 CORRIDOR IN WISCONSIN. IT IS NOT UNTIL VERY
EARLY FRIDAY MORNING THAT ICE GETS REINTRODUCED...AND A CHANGEOVER
TO LIGHT SNOW WOULD THEN OCCUR FOR PLACES SUCH AS VIROQUA OVER TO
JUNEAU/ADAMS COUNTIES. AT THE SAME TIME...RAP SOUNDINGS FOR DBQ
SHOW MAX WARM NOSE OF +4 DEGREES...AROUND +1 FOR BLR...AND THEN
BELOW ZERO FOR AREAS TO THE NORTH. SO...TIGHT GRADIENT FOR
FREEZING RAIN AND SNOW LINE. AS FAR AS ICE ACCUMULATIONS...UP TO
1/10 OF AN INCH STILL EXPECTED ON EXPOSED SURFACES...WHICH WILL
MAKE FOR SLICK TRAVEL OVERNIGHT INTO THE MORNING HOURS FRIDAY.
GIVEN THIS NORTHWARD JOG IN THE LOSS OF ICE / WARM NOSE...HAVE
EXPANDED THE FREEZING RAIN ADVISORY TO INCLUDE VERNON...JUNEAU AND
ADAMS COUNTIES IN WISCONSIN.
THE NORTHERN SIDE OF THIS WEATHER SYSTEM STILL EXPECTED TO PRODUCE A
BAND OF ACCUMULATING SNOW ALONG AND NORTH OF I-90...MAINLY AFTER
MIDNIGHT INTO FRIDAY MORNING. NO BIG CHANGES FROM
PREVIOUS FORECAST...WITH 1 TO 2 INCHES FOR MOST LOCATIONS AND
LOCALLY 3 INCH AMOUNTS POSSIBLE MAINLY FOR CENTRAL WISCONSIN. THIS
TOO COULD MAKE FOR SLICK ROADWAYS FOR THE FRIDAY MORNING
COMMUTE...AND CONSIDERED A HEADLINE FOR THIS BUT WILL HOLD OFF NOW
GIVEN COLLABORATION. IF LATER FORECASTS SHOW AN UPTICK IN
AMOUNTS...OR A DELAY MORE TOWARD THE MORNING COMMUTE...THEN AN
WINTER WEATHER ADVISORY MAY BE NEEDED FOR A FEW COUNTIES.
.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 307 PM CST THU DEC 19 2013
FOCUS OF THIS PERIOD IS SQUARELY ON THE WEEKEND AND THE POTENTIAL
FOR A WINTER STORM TO IMPACT PARTS OF THE FORECAST AREA. STILL
SOME DIFFERENCES BETWEEN THE MODELS BUT THE 19.12Z GFS AND ECMWF
ARE IN BETTER AGREEMENT WITH THE OVERALL PATTERN WITH THE 19.12Z
NAM APPEARING AT THIS TIME TO BE THE ODD MODEL OUT. THE UPPER
LEVEL LOW CURRENTLY ALONG THE CALIFORNIA COAST WILL MOVE OUT OF
THE DESERT SOUTHWEST AND TRACK NORTHEAST ACROSS THE CENTRAL
PORTION OF THE COUNTRY OVER THE WEEKEND. AS IT MOVES TOWARD THE
AREA...A NORTHERN STREAM SHORT WAVE WILL START TO MOVE TOWARD THE
UPPER MIDWEST FROM SOUTHWEST CANADA. THE DIFFERENCES IN THE MODEL
SOLUTIONS REVOLVE AROUND WHETHER THESE TWO SYSTEMS GET PHASED OR
WHETHER THEY STAY SEPARATE. THE NAM WOULD SUGGEST THEY GET PHASED
WHICH PUSHES THE SURFACE LOW AND ASSOCIATED QPF FARTHER SOUTHEAST.
THE GFS AND ECMWF DO NOT PHASE THE TWO SYSTEMS WHICH BRINGS THE
SURFACE LOW AND QPF BACK MORE TO THE NORTHWEST.
THE FORCING FROM THE SHORT WAVE TROUGH WILL START TO MOVE IN
SATURDAY NIGHT. MODERATE TO STRONG PV ADVECTION IN THE 500-300 MB
LAYER SHOULD OCCUR LATE SATURDAY NIGHT JUST AHEAD OF THE WAVES
PASSAGE. MODERATE TO STRONG QG CONVERGENCE WILL BE PRODUCED BY THE
WAVE AND CENTERED OVER THE SOUTHEAST PART OF THE FORECAST AREA AT
12Z SUNDAY. WEAK TO MODERATE FRONTOGENESIS IS SHOWN BY THE GFS IN
THE 600-500 MB LAYER BETWEEN 06Z AND 18Z SUNDAY...ALSO OVER THE
SOUTHEAST PORTIONS OF THE FORECAST AREA. THERE MAY ALSO BE SOME
JET DYNAMICS THAT COME INTO PLAY AS WELL. THE GFS IS SUGGESTING A
SPLIT JET WITH THE AREA UNDER THE RIGHT ENTRANCE REGION OF THE
NORTHERN STREAM JET CORE TO ADD SOME AGEOSTROPHIC LIFT TO THE MIX.
THE GFS BUFKIT SOUNDING FOR BLUE RIVER SUGGEST THE DENDRITIC
GROWTH ZONE SHOULD BE ABOUT 100 MB DEEP WITH GOOD VERTICAL MOTIONS
THROUGH IT. THIS SHOULD LEAD TO SNOW RATIOS IN THE 14-16 TO 1
RANGE LEADING TO SNOW ACCUMULATIONS OF 4 TO 7 INCHES FROM ABOUT
FAYETTE COUNTY IOWA NORTHEAST INTO ADAMS/JUNEAU COUNTIES IN
CENTRAL WISCONSIN. THE POTENTIAL FOR THE HIGHER AMOUNTS IS THE
GREATEST IN PRIMARILY GRANT COUNTY WISCONSIN. THE NORTHWEST WINDS
WILL COME UP SUNDAY ON THE BACK SIDE OF THE SYSTEM WHICH WILL
LIKELY LEAD TO SOME DRIFTING SNOW AND POSSIBLY A LITTLE BLOWING
SNOW OVER THE MORE OPEN AREAS OF NORTHEAST IOWA. IN COORDINATION
WITH SURROUNDING OFFICES...WILL ISSUE A WINTER STORM WATCH FOR
SATURDAY NIGHT AND SUNDAY FOR THE ACCUMULATING SNOW AND ANY
POSSIBLE IMPACT ON THE BACK SIDE OF THE SYSTEM.
WITH THE FOCUS ON THE WEEKEND SYSTEM...HAVE NOT LOOKED EXTENSIVELY
AT THE FORECAST FOR NEXT WEEK. HAVE LET THE MODEL CONSENSUS GRIDS
RIDE WHICH GIVES A SMALL CHANCE FOR SOME SNOW TUESDAY AND TUESDAY
NIGHT ACROSS THE NORTH AS ANOTHER NORTHERN STREAM SHORT WAVE
TROUGH MOVES ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION. THE
COLDEST TEMPERATURES IN THE FORECAST LOOK TO BE BEHIND THE WEEKEND
SYSTEM WITH LOWS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO SUNDAY
NIGHT...HIGHS ONLY IN THE SINGLE DIGITS ABOVE ZERO MONDAY WITH
SINGLE DIGITS BELOW ZERO FOR THE ENTIRE AREA MONDAY NIGHT.
&&
.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 552 PM CST THU DEC 19 2013
MVFR CEILINGS ARE ALREADY IN PLACE THROUGHOUT THE REGION WITH
FLIGHT CONDITIONS ONLY EXPECTED TO WORSEN THROUGH THE NIGHT.
DRIZZLE IS BECOMING MORE WIDESPREAD AND DEVELOPING NORTHWARD
ACROSS IOWA. THE QUESTION IS WITH WHETHER THIS DRIZZLE MAKES IT
INTO LSE/RST OR IF THE LOW LEVELS WILL BE COLD ENOUGH TO CAUSE IT
TO BE SNOW. TEMPERATURES AT THE GROUND WILL BE BELOW FREEZING...SO
ANY DRIZZLE THAT DOES OCCUR WILL BE FREEZING ON CONTACT WITH IT.
CEILINGS ARE EXPECTED TO GO IFR OVERNIGHT WITH VISIBILITY POSSIBLY
GOING DOWN WITH IT AS WELL. PRECIPITATION IS EXPECTED TO CHANGE
OVER TO SNOW FOR AT LEAST A PERIOD ON THE TAIL END OF THE SYSTEM
GOING INTO TOMORROW MORNING. CEILINGS ARE EXPECTED TO STAY AT
LEAST MVFR THROUGH MUCH OF TOMORROW WITH THE RIDGE OF HIGH
PRESSURE NOT MAKING IT IN UNTIL LATER FRIDAY NIGHT.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 6 AM CST FRIDAY FOR WIZ043-044-
053>055-061.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ043-044-053>055-061.
MN...NONE.
IA...FREEZING RAIN ADVISORY UNTIL 6 AM CST FRIDAY FOR IAZ010-011-019-
029-030.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR IAZ011-029-030.
&&
$$
UPDATE...HALBACH
SHORT TERM...ZT
LONG TERM...04
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS PUEBLO CO
258 AM MST FRI DEC 20 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 250 AM MST FRI DEC 20 2013
...MUCH COOLER TODAY...
...SNOW CHANCES NOT LOOKING TOO GREAT...
CURRENTLY...SOME LIGHT SHSN OVER THE WRN PORTION OF THE
STATE...MAINLY INVOF KGJT. SOME LIGHT PRECIP ALSO LIKELY MOVING INTO
THE SAWATCH RANGE AND CONTDVD THRU THE MORNING HOURS. TEMPS MAINLY
IN THE 20S...WITH SOME SINGLE DIGITS FOR THE HIGH VALLEYS. EXTENSIVE
LOW CLOUD DECK NOW COVERING THE ERN PLAINS...BUT FAIRLY SHALLOW AND
THE ERN MTS ARE ACTUALLY RELATIVELY CLEAR THIS MORN.
MAIN QUESTION TODAY IS HOW LONG THE LOW CLOUDS WILL TAKE TO BREAK UP
OVER THE PLAINS. THIS WILL DETERMINE POTENTIAL HIGH TEMPS TODAY.
CURRENT MODEL SOUNDINGS ARE NOT VERY HELPFUL...WITH THE NAM BREAKING
THINGS OUT PRETTY EARLY AND THE RAP HOLDING ON TO A LOW CLOUD DECK
THROUGH THE EARLY AFTERNOON. GIVEN THE PRETTY STOUT LLVL INVERSION
AS ALREADY HINTED OUT IN THE 00Z DEN SOUNDING...AND THE GENERALLY
LIGHT UPSLOPE WINDS EXPECTED OVER THE PLAINS...WILL LEAN TOWARDS A
LATER TIME FOR THE LOW CIGS TO DISSIPATE. THIS WILL KEEP AFTERNOON
HIGHS FROM REACHING THE POTENTIAL SUGGESTED BY H7 TEMPS ONLY A FEW
DEGREES BELOW ZERO. HAVE CUT BACK TEMPS A FEW DEGREES FROM CURRENT
FORECAST...BUT SOME GUIDANCE SUGGESTS THEY MAY EVEN END UP LOWER
THAN FORECAST. BOTTOM LINE...IT WILL BE A GOOD 20 DEGREES COOLER
THAN YESTERDAY...AND FINALLY FEEL LIKE DECEMBER FOR SERN CO.
SNOW POTENTIAL IS NOT LOOKING TOO GREAT TODAY. A NUMBER OF MODEL
SOUNDINGS SUGGEST SOME LIGHT PRECIP OVER THE PLAINS THIS MORN...BUT
GIVEN THE RELATIVELY SHALLOW CLOUD LAYER DO NOT EXPECT ANYTHING THAT
FALLS TO ACCUMULATE OR EVEN MEASURE. SO...HAVE KEPT POPS LOW FOR THE
PLAINS THROUGH TONIGHT. PERSISTENT LIGHT SHSN WILL BE ONGOING OVER
THE CONTDVD AND WILL PICK UP GRADUALLY AS WE GO THROUGH THE
AFTERNOON BEFORE TAPERING OFF THIS EVENING. BUT ACCUMS NOT LOOKING
TOO IMPRESSIVE WITH AT BEST A FEW INCHES OVER THE DVD BY SUN MORNING.
WITH SOME PARTIAL CLEARING TONIGHT AND LIGHT WINDS...TEMPS WILL BE
ON THE COLD SIDE...WITH SOME TEENS POSSIBLE FOR THE PLAINS AND
CONTINUED SINGLE DIGITS AND NEGATIVE READINGS FOR THE MTS AND HIGH
VALLEYS. ROSE
.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 250 AM MST FRI DEC 20 2013
SATURDAY INTO SUNDAY APPEARS TO BE THE MOST ACTIVE WX PD DURING THIS
FORECAST SEGMENT. THE SOUTHERN STORM TRACKING OVER NM MAY CLIP THE
FAR SE CORNER OF COLORADO...WHILE THE NORTHERN SYSTEM WILL LIKELY
BRING SNOW TO THE MOUNTAINS AND POSSIBLY PARTS OF THE I-25 CORRIDOR.
FOR THE FAR SE PLAINS...IT APPEARS THE BEST CHANCE OF BACA COUNTY
SEEING ANY PRECIP WILL BE SAT AFTERNOON AND EVENING. BOTH GFS AND EC
HAVE AN IMPRESSIVE BAND OF PRECIP DEVELOPING OVER THE N TX PHDL INTO
THE OK PHDL...WITH THE N PARTS OF THIS BAND ENTERING INTO SE BACA
COUNTY. ON THE OTHER HAND THE NAM (00Z AND 06Z RUNS) KEEP THE PRECIP
DOWN INTO TX. I HAVE LEANED TOWARDS THE GFS AND EC BUT HAVE
DECREASED POPS A BIT OVER THE BACA COUNTY REGION TO ACCOUNT FOR THE
TRENDS IN THE NAM GUIDANCE.
THE N TIER SYSTEM WILL DROP INTO CO DURING SAT MORNING AND MOVE
ACROSS THE REGION SAT NITE. SNOW IN THE C MTNS IS LIKELY...WITH A
GOOD CHANCE OF SNOW OVER MOST OF THE OTHER MTNS DURING THE LATTER
AFTERNOON AND EVENING HOURS. IT DOES NOT APPEAR THAT ANY SIGNIF
ACCUMS WILL OCCUR...BUT 2-3" IS NOT OUT OF THE QUESTION...ESPECIALLY
ON THE NW SLOPES. SOME SNOW SHOWERS MAY MAKE IT OUT ONTO THE I-25
CORRIDOR...ESPECIALLY SAT EVE/NITE.
DRY AND COOL WX WILL BE LIKELY LATER SUNDAY INTO EARLY TUESDAY.
TUESDAY..XMAS EVE..MAY BE RATHER QUITE NICE GIVEN THE LEE TROUGH AND
DOWNSLOPE. TEMPS ON THE PLAINS WILL LIKELY BE IN THE 50S WITH A 60
OR TWO POSSIBLE.
BY LATE TUESDAY/TUE NITE ANOTHER COLD FRONT WILL MOVE ACROSS THE
REGION. HOWEVER...THIS SYSTEM LOOKS WEAKER ON BOTH THE EC AND GFS
AND THE CHANCE OF SNOW IS DECREASING FOR XMAS EVE INTO XMAS FOR THE
ENTIRE REGION. I HAVE NOT REMOVED POPS COMPLETELY...BUT THE TREND IN THE
GUIDANCE IS SHOWING THE SNOW CHANCES FOR THE LOWER ELEVATIONS
DECREASING. I WOULD NOT BE TOO SURPRISED IF LATER SHIFTS REMOVE THE
POPS COMPLETELY FOR THE LOWER ELEVATIONS XMAS EVE INTO XMAS. TEMPS
XMAS DAY WILL BE A GOOD 10-20F COOLER THAN XMAS EVE.
ANOTHER DISTURBANCE WILL MOVE DOWN ACROSS THE REGION ON FRIDAY
BRINGING ANOTHER COOL FRONT TO THE REGION. /HODANISH
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 250 AM MST FRI DEC 20 2013
MAIN QUESTION IS HOW QUICKLY IFR-MVFR CIGS WILL CLEAR FROM THE
PLAINS TODAY. WITH GENERALLY LIGHT UPSLOPE WINDS AND STRONG
TEMPERATURE INVERSIONS...EXPECT CIGS TO STAY LOW FOR A GOOD PORTION
OF THIS MORNING AND POSSIBLY THROUGH THE AFTERNOON...FOR KPUB FROM
17-18Z...AND AT KCOS 18-19Z. NO ACCUMULATING PRECIP IS EXPECTED BUT
SOME LIGHT PRECIP WILL BE POSSIBLE WITHIN THE LOW CLOUD DECK...WITH
TOPS BREAKING OUT ONLY 1000 FT OR SO AGL. VFR CONDITIONS WILL THEN
PERSIST THROUGH SUN MORNING. LIGHT SHSN WILL CONTINUE THROUGH THIS
EVE OVER THE CONTDVD...WITH MT TOPS OBSCURED DURING THIS PERIOD.
AT KALS...SOME LOCAL PC FG OR BR POSSIBLE THROUGH 15-16Z...AND AGAIN
LATE TONIGHT...BUT WILL STICK WITH A PERSISTENCE FORECAST FOR NOW IN
THE TAFS AND LEAVE CONDITIONS VFR. ROSE
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...ROSE
LONG TERM...HODANISH
AVIATION...ROSE
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
356 AM CST FRI DEC 20 2013
.DISCUSSION...
355 AM CST
SEVERAL ISSUES ONGOING THIS MORNING AS WELL THROUGH THE
WEEKEND...WITH DENSE FOG AND FREEZING RAIN ISSUES THIS MORNING
WITH THE FREEZING RAIN NOW LINGERING INTO THE AFTERNOON AND
POSSIBLY TONIGHT...CONTINUED FLOODING CONCERNS...AND LASTLY
POTENTIAL SNOWFALL WHICH THE AXIS OF HEAVIEST SNOW STILL APPEARS
TO BE ACROSS THE NORTH AND NORTHWEST AREAS OF THE CWA.
ADDRESSING THE MORE IMPORTANT ISSUES IN THE NEAR TERM...LIGHT
FREEZING RAIN OR FREEZING DRIZZLE CONTINUES ACROSS THE ADVISORY
AREA THIS MORNING...WITH LIGHT RAIN OR DRIZZLE ONGOING FOR THE
REMAINDER OF THE CWA. BROAD SOUTHWESTERLY FLOW ALOFT CONTINUES TO
USHER SEVERAL WAVES OF ENERGY...WITH ELONGATED TROUGH OF LOW
PRESSURE EXTENDING FROM THE CENTRAL PLAINS UP THROUGH SOUTHERN
GREAT LAKES. AS THESE WAVES OF ENERGY/SPEED MAXES LIFT NORTHEAST
ACROSS THE REGION THIS MORNING...EXPECT THIS TROUGH OF LOW
PRESSURE TO LIFT EAST NORTHEAST TO CENTRAL ILLINOIS AND NORTHWEST
INDIANA THROUGH THE EARLY AFTERNOON. PRESENT LOW/MID LEVEL
CONVERGENCE WILL CONTINUE TO BE A PERSISTENT THROUGH THIS
PERIOD...WITH CURRENT UPSTREAM WAVE TO AID IN TIGHTENING LOW/MID
LEVEL BAROCLINIC ZONE. THIS WILL ENHANCE FRONTOGENTIC FORCING
ACROSS THE ADVISORY AREA...ALL AIDING IN CONTINUED PRECIP
DEVELOPMENT AT LEAST THROUGH EARLY AFTERNOON FOR THE ENTIRE CWA.
HAVE INCREASED POPS THIS MORNING AND EARLY AFTERNOON...BUT WONDER
IF AFTERNOON POPS WILL NEED TO BE RAISED EVEN FURTHER WITH SHORT
TERM GUIDANCE HINTING AT CONTINUED TO DEVELOPMENT EVEN INTO THE
LATE AFTERNOON. ALTHOUGH CURRENT ASSOCIATED BOUNDARY DRAPED ACROSS
EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA DID MAKE SOME
NORTHWARD PROGRESSION EARLY THIS MORNING...FEEL THAT THIS
NORTHWARD MOVEMENT HAS ENDED AND WILL REMAIN SITUATED UNTIL
DROPPING SOUTH/SOUTHEAST OF THE CWA THIS AFTERNOON. GUIDANCE
HINTING AT SOME WEAK CAA TO BEGIN OCCURRING OVER THE NEXT SEVERAL
HOURS AND WITH LATEST RAP ANALYSIS ALREADY INDICATING THIS ACROSS
WESTERN ILLINOIS...FEEL PRETTY CONFIDENT WITH THIS TREND. THIS
WILL HELP TEMPS IN THE ADVISORY AREA TO HOVER JUST BELOW OR AT THE
FREEZING MARK THROUGH MOST OF TODAY. WITH THIS CONTINUED PRECIP
AND TEMP TRENDS...HAVE DECIDED TO EXTEND THE FREEZING RAIN
ADVISORY THROUGH THE AFTERNOON AND HAVE ALSO INCLUDED KANE COUNTY
IN THE ADVISORY AS WELL. WILL NEED TO ALSO MONITOR THE AFTERNOON
PERIOD FOR THE REMAINING CWA...AS COLD ADVECTION SHOULD HELP TEMPS
LOWER AROUND FREEZING INTO THE LATE AFTERNOON PERIOD. WITH PRECIP
POSSIBLY LINGERING...COULD SEE SOME POSSIBLE LIGHT ICING IN AREAS
OUTSIDE OF THE ADVISORY. ALTHOUGH TEMPS SHOULD BE MARGINAL...AND
AM NOT OVERLY CONCERNED AT THIS TIME.
WITH REGARDS TO THE DENSE FOG...WITH INCREASING MOISTURE IN THE
BOUNDARY LAYER THIS PAST EVENING DENSE FOG DEVELOPED ALONG TO THE
NORTH OF THIS BOUNDARY. MANY REPORTS OF DENSE FOR WERE RECEIVED
THIS PAST EVENING ACROSS NORTHWEST INDIANA...PRIMARILY FOR LAKE
AND PORTER COUNTIES IN INDIANA. WITH THE BOUNDARY SITUATED AND
EXPECTED TO REMAIN THIS WAY THROUGH THE REMAINDER OF THE
MORNING...FEEL CURRENT DENSE FOG ADVISORY FOR THESE LOCATIONS
REMAINS VALID. ALTHOUGH...SOUTHERN AREAS OF COOK COUNTY AND
EASTERN AREAS OF WILL COUNTY WILL NEED TO BE MONITORED OVER THE
NEXT COUPLE OF HOURS AS VIS IN THESE LOCATIONS CONTINUES TO BOUNCE
AROUND 1/2 MILE. END TIMING FOR THIS DENSE FOG ADVISORY REMAINS 9
AM CST...AND SEEMS REASONABLE. THIS SAGGING BOUNDARY AND SLIGHTLY
DRIER AIR SHOULD HELP WITH THE MORE DENSE FOG...BUT WITH PATCHY
DENSE FOG STILL NOT OUT OF THE QUESTION AT LEAST THROUGH MID DAY.
CONFIDENCE WITH THIS FOG REMAINS LOW AT THIS TIME AND WILL NEED TO
MONITOR...POSSIBLY EXTENDING THIS ADVISORY OR MAYBE EVEN EXPANDING
IT LATER THIS MORNING.
WITH SURFACE LOW EXITING TO THE EAST THIS EVENING AND THE ARRIVAL
OF DRIER AIR...SHOULD OBSERVE OVERALL PRECIP CHANCES TO WIND DOWN
FOR THE TIME BEING. ALTHOUGH WITH GUIDANCE CONTINUING TO INDICATE
BROAD SCALE LIFT WITH THE APPROACHING LONGWAVE TROUGH TO THE WEST
IT DOES APPEAR AS IF AREAS ACROSS THE SOUTHERN CWA COULD SEE
ADDITIONAL PRECIP TONIGHT. ALTHOUGH LIGHT PRECIP...THERMAL
PROFILES WOULD INDICATE THAT THIS PRECIP WOULD BE IN THE FORM OF
LIGHT FREEZING RAIN OR LIGHT FREEZING DRIZZLE. ANOTHER PERIOD I AM
CONCERNED ABOUT AT THIS TIME IS LATE TONIGHT INTO EARLY SATURDAY
MORNING...ONCE AGAIN FOR AREAS ACROSS THE SOUTHERN CWA. WILL NEED
TO MONITOR SURFACE TEMP TRENDS ACROSS EAST CENTRAL ILLINOIS DURING
THIS TIME...WITH FREEZING RAIN ONCE AGAIN POSSIBLY BEING AN ISSUE.
EXPANDING PRECIP TO THE SOUTH IS EXPECTED TO INCH FURTHER NORTH
TOWARDS THE SOUTHERN CWA TOWARDS THE 12Z SATURDAY TIME
FRAME...WITH SOUTHWEST FLOW ALOFT PERSISTING OUT AHEAD OF THE
APPROACHING LONGWAVE TROUGH. WITH A SLOW TEMP TREND EXPECTED
SATURDAY MORNING...A PERIOD OF LIGHT FREEZING RAIN COULD CAUSE
SOME ISSUES PRIMARILY SOUTH OF I-80.
WITH REGARDS TO WINTER STORM SATURDAY THROUGH SUNDAY...LATEST
THINKING/UPDATES TO FORECAST CONTINUE TO SUPPORT CURRENT WINTER
STORM WATCH ACROSS NORTHERN PORTIONS OF THE CWA. EXPECTED VARYING
PRECIP TYPES INCLUDING ALMOST ALL WINTER PRECIP TYPES COULD BE
OBSERVED SATURDAY INTO SATURDAY NIGHT...WITH A VARYING THERMAL
PROFILE EXPECTED TO CHANGE THROUGH THE PERIOD FOR ALL AREAS. WILL
NEED TO MONITOR THE SATURDAY MORNING TIME FRAME INTO THE DAY
SATURDAY FOR THE VARYING PREICP TYPE...POSSIBLY ADDING YET ANOTHER
HEADLINE TO ACCOMMODATE FOR THE WINTRY MIX. EXPECTED SURFACE LOW
TRACK STILL SUPPORTIVE FOR BEST CHANCES FOR SNOW OR ALL SNOW
ACROSS NORTHWEST AND NORTH CENTRAL ILLINOIS WITH SNOWFALL TOTALS
IN EXCESS OF 6 INCHES STILL APPEARING POSSIBLE. THE EXPECTED RAIN
SNOW LINE HAS VARIED SLIGHTLY...BUT THE GENERAL IDEA REMAINING THE
SAME. OHARE TO PERU ILLINOIS LINE ARE THE DIVIDING LINE AT THIS
TIME...WITH CURRENT SNOW FORECAST INDICATING RAPID INCREASE IN
SNOW AMOUNTS RIGHT TO THE NORTH OF THIS LINE AND WITH AREAS TO THE
SOUTH OBSERVING LIGHT SNOW ACCUMULATIONS.
ALTHOUGH LATEST TRENDS ARE INDICATING THAT THE AXIS OF HEAVIEST
RAINFALL IS BEGINNING TO SHIFT SOUTH OF THE CWA...DECENT RAINFALL
AMOUNTS OF UP TO AN INCH STILL SUPPORT THE POSSIBILITY OF
FLOODING...AND HAVE MADE NO CHANGES TO THE CURRENT FLOOD WATCH.
RODRIGUEZ
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* CIG/VSBY TRENDS THROUGH THE DAY WITH IFR CONTINUING. DENSE FOG
IN CLOSE PROXIMITY TO MDW WITH 1/4-1/2SM VSBY STILL POSSIBLE
THROUGH DAYBREAK.
* PERIODIC -RA/DZ THROUGH MIDDAY WITH LOW CHANCE FOR SOME
-FZRA/FZDZ THIS AFTERNOON...MAINLY A ORD.
* NORTH TO NORTH-NORTHEAST WINDS INCREASING TO AROUND 10 KT THEN
TURNING NORTHWEST THIS EVENING.
MDB
//DISCUSSION...UPDATED 09Z...
WARM FRONTAL BOUNDARY HAS BEEN OSCILLATING NORTH AND SOUTH OVER A
NARROW CORRIDOR FROM ROUGHLY KGBG TO KGYY AND SOUTHERN LOWER
MICHIGAN THE PAST FEW HOURS. THIS HAS RESULTED IN A SOMEWHAT
TRANSIENT BAND OF DENSE FOG WHICH AS BEEN AFFECTING MDW AND GYY AT
TIMES. A LOOK AT AREA WEBCAMS AND SURFACE OBS SHOWS THAT THERE HAS
BEEN SOME SLIGHT IMPROVEMENT IN VSBY RIGHT ALONG THE BOUNDARY BUT
THIS MAY BE DUE TO THE BAND OF DENSE FOG MOVING BACK AND FORTH VS.
ANY CHANGE IN LOWEST VSBYS. EXPECT THAT THE BOUNDARY WILL MEANDER
THROUGH DAYBREAK LEAVING MDW/GYY IN A VARIABLE VSBY SITUATION AND
CANNOT RULE OUT A RETURN TO 1/4-1/2SM VSBY FOR AT LEAST A SHORT
TIME. THE BOUNDARY DOES LOOK TO PUSH SOUTH LATER THIS MORNING AS
SURFACE LOW PRESSURE MOVES NORTHEAST ALONG IT. THIS SHOULD ALLOW
NORTHERLY WINDS TO SET UP WITH COOLER AIR SPREADING SOUTH WHICH
SHOULD HELP VSBY. MAY BE TOUGH TO LOSE THE IFR CIGS BUT MVFR VSBY
LOOKS TO OCCUR TOWARD/DURING THE AFTERNOON AT SOME POINT.
OTHERWISE PERIODS OF -RA/DZ WILL CONTINUE THROUGH THE MORNING.
MDB
FROM 06Z...
MESSY CONDITIONS CONTINUE ACROSS THE TERMINALS TONIGHT WITH A
FRONTAL BOUNDARY STRETCHING FROM LOW PRESSURE OVER OKLAHOMA TO
ROUGHLY A KEOK TO KC75 TO KVPZ LINE. ABUNDANT MOISTURE AND LIFT
CONTINUE OVER THE BOUNDARY BRINGING RAIN SHOWERS AND AREAS OF
DRIZZLE TO THE TERMINALS. VSBY IS LOWEST RIGHT ALONG THE BOUNDARY
WITH GYY AROUND 1/4SM AND THIS WILL LIKELY PERSIST AS LONG AS THE
BOUNDARY IS NEARBY...WHICH AT THIS POINT LOOKS TO BE FOR MUCH OF
THE OVERNIGHT. AREAS NORTH HAVE SEEN VSBY GENERALLY AROUND A MILE
AND THIS SHOULD BE THE TREND THROUGH THE NIGHT...THOUGH THERE MAY
BE SOME DOWNWARD FLUCTUATIONS AT TIMES. CIGS SHOULD STAY STEADY
IN THE 002-004 RANGE THROUGH THE NIGHT AS WELL. RFD MAY SEE SOME
FREEZING RAIN/FREEZING DRIZZLE OVERNIGHT AS TEMPS COOL SLIGHTLY.
THINGS BECOME LESS CERTAIN AFTER DAYBREAK. THE LOW WILL TRACK
NORTHEAST TO NORTH-CENTRAL INDIANA BY FRIDAY AFTERNOON TURNING
WINDS FROM NORTHEAST TO NORTH-NORTHWEST THROUGH THE AFTERNOON. THE
MAIN QUESTION WILL BE HOW QUICKLY AND TO WHAT EXTENT CIGS/VSBY
IMPROVE. WITH THE BOUNDARY STILL IN THE AREA THROUGH THE MORNING
WILL ONLY HAVE VERY MINOR INCREASES IN CIGS/VSBY WITH BETTER
INCREASES DURING THE AFTERNOON AS COLDER AIR FILTERS INTO THE
REGION. SHOWERS/DRIZZLE WILL CONTINUE PERIODICALLY BEFORE TAPERING
OFF DURING THE AFTERNOON. RFD WILL HAVE THE BEST CHANCE OF SEEING
FREEZING RAIN THROUGH THE MORNING...WITH A LOW CHANCE THAT SOME
LIGHT FREEZING RAIN OR FREEZING DRIZZLE WILL MAKE IT INTO THE
CHICAGO TERMINALS DURING THE EARLY AFTERNOON AS COLDER AIR
ARRIVES. MVFR AND POSSIBLY IFR LOOK TO BE IN PLACE FOR FRIDAY
EVENING WITH NORTH-NORTHWEST WINDS.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* HIGH CONFIDENCE IN IFR CONTINUING WITH LOWEST CONDITIONS THROUGH
DAYBREAK. LOW CONFIDENCE WITH SPEED/MAGNITUDE OF CIG/VSBY
IMPROVEMENT THROUGH THE DAY.
* HIGH CONFIDENCE IN PRECIP WINDING DOWN THIS AFTERNOON...MEDIUM-
HIGH CONFIDENCE THAT THREAT FOR -FZRA/FZDZ AT ORD IS LOW.
* HIGH CONFIDENCE IN WIND TRENDS.
MDB
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SAT...WINTRY MIX OF PRECIP FROM MIDDAY ON...WITH A CHANCE OF A
PERIOD OF FREEZING RAIN DURING THE NIGHT. MVFR TO IFR.
SUN...SNOW. MVFR TO IFR.
MON...MVFR CIGS. CHANCE OF SNOW SHOWERS WITH IFR.
TUE...VFR.
WED...VFR BECOMING MVFR CIGS.
THU...MVFR CIGS IMPROVING TO VFR.
TRS
&&
.MARINE...
301 AM CST
LOW PRESSURE CENTERED OVER NORTH-CENTRAL OKLAHOMA WILL TRACK
NORTHEAST ALONG A FRONTAL BOUNDARY WHICH EXTENDS NORTHEAST INTO
NORTHERN INDIANA AND EASTWARD ACROSS LAKE ERIE AND ONTARIO.
MEANWHILE HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE LITTLE
THROUGH THE DAY. THE STRONGEST PRESSURE GRADIENT IS STARTING TO SET
UP EARLY THIS MORNING AND WILL LIKELY RESULT IN AN INCREASE IN
NORTHEAST WINDS ACROSS MUCH OF THE LAKE THROUGH MID MORNING BEFORE
THE PRESSURE GRADIENT EASES. SPEEDS MAY PUSH 30 KT FOR A TIME
THROUGH MID OR LATE MORNING...ESPECIALLY ACROSS CENTRAL SECTIONS OF
THE LAKE. THE LOW WILL PASS SOUTH OF THE LAKE LATER THIS AFTERNOON
AND BEGIN TO WEAKEN WITH THE HIGH WEAKENING AS WELL. ANOTHER SURFACE
LOW WILL DEVELOP OVER THE ARKLATEX SATURDAY AND LIFT NORTHEAST TO
NORTHERN OHIO BY SUNDAY AFTERNOON. A VERY STRONG HIGH WILL THEN
DEVELOP SOUTHWARD INTO THE NORTHERN PLAINS AS THE LOW MOVES INTO NEW
ENGLAND SUNDAY NIGHT. THIS WILL LEAVE LAKE MICHIGAN IN THE PRESSURE
GRADIENT BETWEEN THE TWO SYSTEMS SATURDAY NIGHT AND SUNDAY WITH
COLDER AIR SPILLING ACROSS THE LAKE AS WELL. THIS WILL SET THE STAGE
FOR ANOTHER ROUND OF STRONG WINDS WHICH WILL START OUT NORTHEAST
THEN SHIFT NORTH-NORTHWEST AND EASE UP LATE SUNDAY AFTERNOON. THE
HIGH WILL PASS SOUTH OF THE LAKE TUESDAY BEFORE LOW PRESSURE TRACKS
SOUTHEAST ACROSS THE CANADIAN PRAIRIES AND NORTHERN PLAINS. THIS
SHOULD LEAD TO ANOTHER PERIOD OF INCREASED WINDS...THIS TIME FROM
THE SOUTH AND SOUTHWEST WEDNESDAY. WILL KEEP SPEEDS BELOW GALE FORCE
THROUGH THE PERIOD BUT WILL NEED TO MONITOR FOR SHORT WINDOWS OF
GALE FORCE WINDS SATURDAY NIGHT AND SUNDAY MORNING...AND AGAIN EARLY
WEDNESDAY.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011 UNTIL NOON FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
FLOOD WATCH...ILZ033-ILZ039...9 AM SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002 UNTIL 9 AM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...9 AM SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...LMZ740...9 AM FRIDAY TO 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 AM FRIDAY.
&&
$$
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AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
318 AM CST FRI DEC 20 2013
.DISCUSSION...
813 PM CST
FOR EVENING UPDATE...
MOVED UP START AND EXPANDED SLIGHTLY FREEZING RAIN ADVISORY FOR
FAR NORTH AND NORTH CENTRAL IL TONIGHT-FRIDAY. HAVE ALSO MADE SOME
ADJUSTMENTS TO WEEKEND STORM SYSTEM AS OUTLINED BELOW.
TONIGHT/FRIDAY...
HAVE SLIGHTLY EXPANDED AND STARTED THE FREEZING RAIN ADVISORY
EARLIER TONIGHT AS TEMPERATURES HOVER RIGHT AROUND 32F ACROSS
NORTH CENTRAL AND FAR NORTHEAST ILLINOIS...AND A REPORT OF A LIGHT
GLAZE HAS ALREADY BEEN RECEIVED FROM THE NORTHWEST SIDE OF ROCKFORD.
EVENING GOES WATER VAPOR LOOP DEPICTS A SHORT WAVE CENTER NEARING
THE OZARKS IN THE BROAD MOIST WSW FLOW OVER THE AREA. THIS FEATURE
HAS LED TO AN EXPANSION IN LOW CLOUDS AS WELL AS LIGHT RAIN/DRIZZLE
ACROSS NORTHEAST MO...EASTERN IA...SOUTHERN WI...AND NORTHWEST AND
NORTH CENTRAL IL. THE 00Z DVN SOUNDING SHOWED 25-35KT OF
SOUTHWESTERLY FLOW WITHIN A SATURATED LAYER FROM 750MB TO THE
SURFACE. THE MIN TEMP OBSERVED IN THAT LAYER OF ONLY -1C...SO
CERTAINLY NO ICE CRYSTALS INVOLVED. THE RAP APPEARS TO ANALYZE THIS
WELL AT 285K-290K WITH SATURATED ISENTROPIC ASCENT ACROSS NORTHERN
IL INTO OVERNIGHT...AND THE CONVERGENCE OF THE LOW-LEVEL BOUNDARY
DRAPED ACROSS THE AREA HELPING TO POOL MOISTURE/SATURATION.
THE SURFACE STATIONARY BOUNDARY IS ARCED FROM SOUTH OF PERU TO THE
SOUTH SIDE OF CHICAGO. FOR TEMPERATURES...BELIEVE THAT NORTH OF THE
BOUNDARY WILL BASICALLY HOLD STEADY OR EASE DOWNWARD...WHILE SOUTH
OF THERE MAY EVEN KEEP INCHING UP. FOR POINTS NORTH...THIS CREATES
AN EARLIER AND PROBABLY BETTER POTENTIAL FOR LIGHT ICING THAN
ORIGINALLY FORECAST...AS TEMPS ACROSS NORTH CENTRAL IL ARE ALREADY
32-33F. SO HAVE EXPANDED FREEZING RAIN DEPICTION IN THE GRIDS AND
AGAIN STARTED THE ADVISORY EARLIER.
SATURDAY/SUNDAY...
HAVE MADE ADJUSTMENTS TO THE FORECAST GRIDS FOR SATURDAY INTO SUNDAY
BASED ON MODEL THERMAL PROFILES AND SOUNDINGS...PARTICULARLY THE
1000-850 MB CRITICAL THICKNESS (1300 DM) WHICH IS A KEY INDICATOR
FOR SNOW VERSUS RAIN/ZR/SLEET. THE GFS RUNS TODAY WERE THE COLDEST
WITH THE NAM/ECMWF SHOWING A MUCH MORE DISTINCT WARM NOSE AT 850
MB...BUT EVEN THE GFS WOULD ONLY FAVOR THE FAR NORTHERN CWA FOR A
WINTRY MIX TRANSITIONING TO SNOW/SLEET AND THEN ALL SNOW ON SATURDAY
NIGHT WHERE THERE IS THE BEST OVERLAP WITH FORCING AND LIFT THROUGH
THE DGZ. IN BETWEEN THE FAVORED AREA FOR MORE SIGNIFICANT SNOW/SLEET
ACCUMS AND MAINLY RAIN OVER THE SOUTHEAST HALF OF THE CWA...HAVE
INDICATED A TRANSITION ZONE WHERE A MIXED BAG INCLUDING FREEZING
RAIN IS POSSIBLE. AM CONCERNED THAT IF P-TYPE IS MAINLY ZR FOR A
TIME...THERE COULD BE DECENT ICE ACCRETION...AND THIS WOULD
INCLUDE PARTS OF THE WEST AND NORTHWEST CHICAGO METRO.
FINALLY...SUNDAY MORNING IT APPEARS THAT ALL BUT THE SOUTHEAST
THIRD OF THE CWA WILL TRANSITION OVER TO ALL SNOW AS COLDER AIR
PUSHES IN ALOFT.
THE TWEAKS TO QPF AND WEATHER TYPES AND SNOW AMOUNT GRIDS RESULTED
IN A MUCH TIGHTER SNOWFALL GRADIENT...WITH POTENTIAL FOR AMOUNTS IN
EXCESS OF 6 INCHES IN NORTH CENTRAL/NW AND EXTREME NORTHEASTERN
ILLINOIS...QUICKLY TAPERING TO THE SOUTHEAST. LITTLE OR NO SNOW
ACCUMULATION IS ANTICIPATED IN THE SOUTHEAST THIRD OF THE CWA.
NEEDLESS TO SAY...THIS IS STILL A FLUID SITUATION AND SMALL CHANGES
IN THE TRACK OF THE LOW PRESSURE SYSTEM AND THERMAL PROFILES WILL
HAVE LARGE IMPLICATIONS IN PRECIPITATION TYPE AND AMOUNTS. HAVE MADE
NO CHANGES TO THE WINTER STORM WATCH AND FLOOD WATCH IN EFFECT.
MTF/RC/RATZER
//PREV DISCUSSION...
UPDATED...415 PM CST FOR THIS WEEKEND PORTION
TONIGHT THROUGH FRIDAY NIGHT
UPDATED...1224 PM CST
FRONTAL BOUNDARY IS DRAPED FROM THE CHICAGO METRO AREA WSW TO NEAR
THE QUAD CITIES THIS AFTERNOON. ASCENT IS FORECAST TO INCREASE THIS
EVENING AND TONIGHT ON TOP OF THE BOUNDARY WHICH WILL MEANDER SOME
AS THE SURFACE WAVE LIFTS ACROSS THE REGION. WARM ADVECTION ALOFT
LEAVES LITTLE DOUBT THAT PRECIP WILL MELT ALOFT WITH 3-4C SATURATED
WARM LAYER TEMPS AS FAR NORTH AS THE WI STATE LINE. THE BIG CONCERN
WILL BE SURFACE/GROUND TEMPERATURE TRENDS. TEMPERATURES ARE
EXPECTED TO MOSTLY HOLD STEADY INTO THE LATE EVENING...THEN COLDER
//BELOW FREEZING// SURFACE TEMPS WILL START TO TRICKLE SOUTHEAST
INTO FAR NORTHERN IL AS THE LOW STARTS TO PASS TO OUR SOUTH.
CURRENTLY IT APPEARS THAT ONLY THE FAR REACHES OF THE CWA...
INCLUDING PORTIONS OF OGLE...WINNEBAGO...BOONE...AND MCHENRY
COUNTIES...WILL SEE SURFACE TEMPERATURES FALLING BELOW FREEZING
OVERNIGHT AND WHERE THE CONCERN FOR LIGHT FREEZING RAIN AND LIGHT
ICE ACCUMULATIONS WILL BE. A FREEZING RAIN ADVISORY HAS BEEN ISSUED
FOR THESE COUNTIES...AND EXPECT A GLAZE UP TO A TENTH OF AN INCH OF
ICE FOR THESE AREAS.
BY MID MORNING FRIDAY...TEMPERATURES ARE EXPECTED TO CONTINUE TO
SLOWLY FALL WITH THE LOW DEPARTING EAST. FORCING QUICKLY TAPERS BUT
PERSISTENT LOW LEVEL MOISTURE AND WEAK OMEGA RAISES THE CONCERN FOR
FREEZING DRIZZLE TO SPREAD SOUTH OF THE CURRENT ADVISORY
AREA...PERHAPS AS FAR SOUTH AS THE I-80 CORRIDOR. MID/HIGH LEVEL
MOISTURE WILL BE PRESENT...HOWEVER MID LEVEL DRY LAYER IS EXPECTED
TO INHIBIT SEEDER/FEEDER FROM INTRODUCING ICE INTO THE LOW LEVEL
MOISTURE LAYER...WHICH ONLY HAS TEMPERATURES AS COOL AS -5C.
SURFACE TEMPERATURES WILL BE RIGHT AROUND THE FREEZING MARK. FOR
NOW PLAN ON HIGHLIGHTING AREA WITH AN SPS...AND CANNOT RULE OUT
EXPANSION OF ADVISORY FARTHER SOUTH LATER INTO THE DAY FRIDAY IF
IT APPEARS TEMPERATURES WILL BE COOLER OR IF PRECIP MORE ROBUST.
DEUBELBEISS
FOR THE WEEKEND...
UPDATED...415 PM CST...
A VERY ACTIVE WEATHER PATTERN IS SETTING UP...WITH A FLOOD WATCH
ISSUED FOR THE SOUTHEASTERN PORTIONS OF THE CWA AND A WINTER STORM
WATCH ISSUED FOR THE NORTHERN AND NORTHWESTERN PORTIONS OF THE
CWA.
THE FIRST AREA OF CONCERN WILL BE THE POTENTIAL FOR HEAVY RAINFALL
OVER AT LEAST PORTIONS OF THE AREA. HAVE BEEN MONITORING THE
DEVELOPMENT OF A SOUTHERN STREAM SYSTEM OVER THE SOUTH HIGH PLAINS.
AS OF THURSDAY AFTERNOON...THE SYSTEM IS MOVING ONSHORE INTO
SOUTHERN CALIFORNIA AND WILL FINALLY BE SAMPLED BY THE UPPER AIR
DATA NETWORK. WHILE THE MODELS HAVE PROVIDED A MYRIAD OF SOLUTIONS
FOR THE TRACK OF THIS SYSTEM...MUCH OF THE VIABLE GUIDANCE LOOKED AT
TODAY IS CONVERGING ON THE "WARMER" SOLUTION FOR THE LOCAL
AREA...WITH THE EXCEPTION OF THE GFS WHICH IS THE OUTLIER...PUSHING
THE SYSTEM TO FAR EAST...TOO FAST. THE CONVERGED SOLUTION WILL
TRACK A SERIES OF WAVES ALONG A WARM FRONT DEVELOPING FROM THE SOUTH
HIGH PLAINS INTO NORTHERN ILLINOIS. WARM AIR...MOIST AIR...WITH
TEMPS IN THE UPPER 30S AND DEW POINTS IN THE LOWER TO MIDDLE 30S HAS
ALREADY OVERSPREAD MUCH OF THE AREA. THE WARM FRONT WILL MEANDER
OVER THE AREA AS THE MAIN SFC LOW DEEPENS AND TRACKS ALONG THE
BOUNDARY...CROSSING THE MIDDLE MISSISSIPPI VALLEY BY FRIDAY
MORNING. BY FRIDAY MORNING...THE WARM FRONT SHOULD LAY RIGHT
THROUGH THE MIDDLE OF THE CWA...WITH TEMPS IN THE LOWER 30S ALONG
THE WISCONSIN BORDER...WITH LOWER 40S OVER LOCATIONS SOUTH OF THE
ILLINOIS AND KANKAKEE RIVERS. AS THE SFC LOW TRACKS NEWD ALONG THE
PATH OF THE FRONTAL TROUGH...HIGH PRESSURE WILL BE MOVING OFF THE
SERN COAST. THIS WILL SET UP A WIDE OPEN GULF OF MEXICO...WITH
COPIOUS AMOUNTS OF MOISTURE STREAMING NWD. PWATS ARE FORECAST TO
RISE TO 1.0 TO 1.5 INCHES OVER THE SERN PORTIONS OF THE CWA RIDING
ON A STRONG LOW LEVEL JET...WITH MAX 850MB WINDS OVER 60-70KT.
WHILE THE STRONGEST OF THE LOW LEVEL JET WILL BE TO THE
SOUTH...MOSTLY OVER THE OHIO VALLEY...THERE WILL BE AMPLE ISENTROPIC
LIFT AND MOISTURE TRANSPORT TO SUPPORT AREAS OF HEAVY RAINFALL. AT
THIS POINT...IT LOOKS LIKE THE HEAVIEST RAIN WILL BE OVER THE SERN
PORTIONS OF THE CWA...OUTLINED IN THE FLOOD WATCH ISSUED THIS
AFTERNOON. HOWEVER...THE HEAVY RAIN WILL NOT BE THE ONLY PROBLEM.
WITH COOLER AIR REMAINING AT THE SFC NORTH OF THE WARM FRONT...THE
STRONG ISENTROPIC LIFT ALONG AND NORTH OF THE BOUNDARY WILL FORCE
THE WARMER AIR OVER THE COOLER AIR AT THE SFC...SETTING UP A PERIOD
OF MIXED FREEZING AND FROZEN PCPN. THE EXACT LOCATION OF THE WINTRY
MIX OF PCPN STILL REMAINS A LITTLE TOUGH TO NARROW DOWN...BUT MOST
OF THE AREA NORTH OF THE KANKAKEE AND ILLINOIS RIVERS WILL SEE A
LEAST SOME PERIODS OF THE WINTRY MIX PCPN...WITH THE ROCKFORD AREA
LIKELY NOT SEEING ANY LIQUID WHILE THE CHICAGO METRO SHOULD SEE SOME
AND AND SOME OF THE WINTRY MIX.
AS THE HEAVY RAIN SITUATION IS WINDING DOWN SATURDAY NIGHT OR EARLY
SUNDAY MORNING...THE MAIN FORECAST CONCERN WILL SHIFT TO THE
POTENTIAL FOR HEAVY SNOWFALL. THE SRN STREAM SYSTEM NOT ONLY WILL
BE RESPONSIBLE FOR DRAWING MOISTURE NORTHWARD...THERE SHOULD BE SOME
PHASING WITH A NORTHERN STREAM SHORTWAVE DROPPING OUT OF THE NRN
PLAINS. THIS SHOULD LEAD TO THE DEVELOPMENT OF A WEAK SECONDARY
CIRCULATION OVER NRN IL BY SUNDAY MORNING...ENHANCING THE DRAW OF
COOLER AIR FROM THE NORTH. THE STRONGER COLD ADVECTION AND A STRONG
DEFORMATION ZONE ARE ADVERTISED TO SET UP OVER NRN IL/SRN WI WHICH
WILL BE THE PRIMARY FOCUSING ELEMENTS FOR A BAND OF HEAVY SNOW. AT
THIS POINT...BASED ON THE GOOD CONSENSUS OF THE NAM AND
ECMWF...WHICH WOULD WOULD INDICATE AN AXIS OF HEAVIER SNOW GENERALLY
FROM ERN IOWA TO SERN WISCONSIN. ALL THINGS CONSIDERED...CONFIDENCE
IS BECOMING HIGH ENOUGH FOR IN EXCESS OF 6 INCHES OF SNOW OVER THE
NRN AND NWRN PORTIONS OF THE CWA...AS OUTLINED IN THE WINTER STORM
WATCH ISSUED THIS AFTERNOON. CURRENTLY ANTICIPATE THAT THE ENTIRE
CWA WILL SEE AT LEAST SOME SNOW...WITH 2 TO 4 INCHES ALONG A LINE
FROM CHICAGO TO PONTIAC AND 1 TO 2 INCHES FROM VALPARAISO TO
PONTIAC...TAPERING OFF TO AN INCH OR LESS OVER THE FAR SERN PORTIONS
OF THE CWA.
AK
LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...
UPDATED 316 PM CST
SUNDAY NIGHT...
GUIDANCE CONTINUES TO BE CONSISTENT IN DELIVERING A SHOT OF ARCTIC
AIR IN THE WAKE OF THE SIGNIFICANT WEEKEND STORM. A NORTHERN STREAM
TROUGH CURRENTLY NEAR THE NORTH POLE WILL DIG IN OVER THE NORTH
CENTRAL CONUS COUPLED WITH A ~1040 MB HIGH DROPPING SOUTH FROM THE
NORTHERN PLAINS. ALL OF THE SYSTEM SNOWS SHOULD BE OFF TO THE EAST
SUNDAY NIGHT...BUT POSITIVE VORTICITY ADVECTION FROM SHORT WAVES
ROTATING AROUND DEEP UPPER TROUGH COULD SQUEEZE OUT SOME LIGHT SNOW
OR FLURRIES IN THE ARCTIC AIR MASS. THE ECMWF CONTINUES TO BE MOST
BULLISH IN SQUEEZING OUT LIGHT QPF OVER THE AREA. THERE ALSO COULD
BE A BRIEF PERIOD OF FAVORABLE LAKE EFFECT CONDITIONS FOR PORTIONS
OF NW INDIANA DEPENDING ON IF WINDS CAN REMAIN CLOSER TO DUE NORTH
BEFORE BACKING WEST NORTHWEST. TEMPERATURES WILL PLUMMET IN STRONG
COLD ADVECTION BUT PERSISTENT NW WINDS AND CLOUD COVER COULD LIMIT
HOW FAR THEY FALL. WITH THE RAPIDLY FALLING TEMPERATURES SUNDAY
NIGHT...THERE COULD VERY WELL BE A FLASH FREEZE OF ANY REMAINING
MOISTURE ON THE GROUND.
MONDAY...
MAINTAINED A SLIGHT CHANCE OF FLURRIES ON MONDAY MORNING AS THE DEEP
UPPER TROUGH WILL BE OVERHEAD AND IT MAY NOT BE HARD TO SQUEEZE OUT
DENDRITES DESPITE THE COLD DRY AIR MASS. ALSO GUIDANCE INDICATES A
FAIRLY STOUT WAVE FOCUSED INTO THE NORTHEAST CWA AND WISCONSIN...SO
FELT COMFORTABLE WITH THE SLIGHT CHANCE POP FROM GUIDANCE BLEND
INITIALIZATION FOR NORTHEAST IL AND EXTREME NW INDIANA. HIGH
TEMPERATURES MONDAY AND LOWS MONDAY NIGHT WILL BE COLD
EVERYWHERE...BUT HOW COLD WILL DEPEND ON WHICH AREAS MAINTAIN
SUBSTANTIAL SNOW PACK AFTER THE WEEKEND SYSTEM. AT THIS TIME...IT
APPEARS THAT THE NORTHERN CWA WOULD HAVE THE BEST CHANCE. WITH
SURFACE HIGH BEING NEAR OR OVER THE AREA AND NO MORE THAN PARTLY
CLOUDY SKIES EXPECTED...DROPPED LOW TEMPERATURES MONDAY NIGHT FROM
PREVIOUS FORECAST TO 5 TO 10 BELOW WEST OF THE FOX VALLEY. STAYED
MORE CONSERVATIVE IN THE SOUTHERN CWA WHERE LITTLE OR NO SNOW COVER
SHOULD BE LEFT. TO NOTE...THE ECMWF AND GFS WHICH HAVE CLEAR SKIES
HAVE LOWS IN THE COLDEST SPOTS 10 DEGREES COLDER THAN IN FORECAST
GRIDS...WHILE CANADIAN MODEL KEEPS CLOUD COVER AND IS A GOOD DEAL
WARMER.
TUESDAY NIGHT THROUGH THURSDAY...
AFTER A BITTERLY COLD START TO CHRISTMAS EVE DAY...SOUTHWEST WARM
ADVECTION BEHIND TROUGH DEPARTING TO THE EAST WILL ENABLE A DECENT
AFTERNOON TEMPERATURE RECOVERY...BUT STILL WELL BELOW CLIMO. COULD
SEE TEMPERATURES BEING A BIT WARMER THAN CURRENTLY FORECAST IN AREAS
WITHOUT SNOW COVER. WILL HAVE TO WATCH FOR A NORTHERN STREAM WAVE
BEING A BIT FARTHER SOUTH THAN MODEL CONSENSUS ON CHRISTMAS EVE
NIGHT...BUT WITH ECMWF TRENDING SOUTH...INDICATED A SLIGHT CHANCE OF
LIGHT SNOW NEAR THE WISCONSIN BORDER. THIS FEATURE COULD THEN GO ON
TO RESULT IN AT LEAST SOME LIGHT SNOW OR FLURRIES IN THE AIR FOR THE
ENTIRE AREA ON CHRISTMAS DAY. THIS WOULD BE A CONSOLATION PRIZE FOR
AREAS THAT LOSE THEIR SNOW COVER THIS WEEKEND...BUT FOR AREAS THAT
KEEP AT LEAST 1 INCH OF SNOW ON THE GROUND...A WHITE CHRISTMAS IS
HIGHLY LIKELY. TEMPERATURES WILL MODERATE TO NEAR NORMAL ON
CHRISTMAS DAY...WITH ANOTHER SHOT OF ARCTIC AIR POSSIBLE ON THURSDAY
BEHIND THE CHRISTMAS DAY SYSTEM.
CONFIDENCE IN A WHITE CHRISTMAS FOR AREAS THAT MAINTAIN AT LEAST 1
INCH OF SNOW COVER THIS WEEKEND...HIGH.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* CIG/VSBY TRENDS THROUGH THE DAY WITH IFR CONTINUING. DENSE FOG
IN CLOSE PROXIMITY TO MDW WITH 1/4-1/2SM VSBY STILL POSSIBLE
THROUGH DAYBREAK.
* PERIODIC -RA/DZ THROUGH MIDDAY WITH LOW CHANCE FOR SOME
-FZRA/FZDZ THIS AFTERNOON...MAINLY A ORD.
* NORTH TO NORTH-NORTHEAST WINDS INCREASING TO AROUND 10 KT THEN
TURNING NORTHWEST THIS EVENING.
MDB
//DISCUSSION...UPDATED 09Z...
WARM FRONTAL BOUNDARY HAS BEEN OSCILLATING NORTH AND SOUTH OVER A
NARROW CORRIDOR FROM ROUGHLY KGBG TO KGYY AND SOUTHERN LOWER
MICHIGAN THE PAST FEW HOURS. THIS HAS RESULTED IN A SOMEWHAT
TRANSIENT BAND OF DENSE FOG WHICH AS BEEN AFFECTING MDW AND GYY AT
TIMES. A LOOK AT AREA WEBCAMS AND SURFACE OBS SHOWS THAT THERE HAS
BEEN SOME SLIGHT IMPROVEMENT IN VSBY RIGHT ALONG THE BOUNDARY BUT
THIS MAY BE DUE TO THE BAND OF DENSE FOG MOVING BACK AND FORTH VS.
ANY CHANGE IN LOWEST VSBYS. EXPECT THAT THE BOUNDARY WILL MEANDER
THROUGH DAYBREAK LEAVING MDW/GYY IN A VARIABLE VSBY SITUATION AND
CANNOT RULE OUT A RETURN TO 1/4-1/2SM VSBY FOR AT LEAST A SHORT
TIME. THE BOUNDARY DOES LOOK TO PUSH SOUTH LATER THIS MORNING AS
SURFACE LOW PRESSURE MOVES NORTHEAST ALONG IT. THIS SHOULD ALLOW
NORTHERLY WINDS TO SET UP WITH COOLER AIR SPREADING SOUTH WHICH
SHOULD HELP VSBY. MAY BE TOUGH TO LOSE THE IFR CIGS BUT MVFR VSBY
LOOKS TO OCCUR TOWARD/DURING THE AFTERNOON AT SOME POINT.
OTHERWISE PERIODS OF -RA/DZ WILL CONTINUE THROUGH THE MORNING.
MDB
FROM 06Z...
MESSY CONDITIONS CONTINUE ACROSS THE TERMINALS TONIGHT WITH A
FRONTAL BOUNDARY STRETCHING FROM LOW PRESSURE OVER OKLAHOMA TO
ROUGHLY A KEOK TO KC75 TO KVPZ LINE. ABUNDANT MOISTURE AND LIFT
CONTINUE OVER THE BOUNDARY BRINGING RAIN SHOWERS AND AREAS OF
DRIZZLE TO THE TERMINALS. VSBY IS LOWEST RIGHT ALONG THE BOUNDARY
WITH GYY AROUND 1/4SM AND THIS WILL LIKELY PERSIST AS LONG AS THE
BOUNDARY IS NEARBY...WHICH AT THIS POINT LOOKS TO BE FOR MUCH OF
THE OVERNIGHT. AREAS NORTH HAVE SEEN VSBY GENERALLY AROUND A MILE
AND THIS SHOULD BE THE TREND THROUGH THE NIGHT...THOUGH THERE MAY
BE SOME DOWNWARD FLUCTUATIONS AT TIMES. CIGS SHOULD STAY STEADY
IN THE 002-004 RANGE THROUGH THE NIGHT AS WELL. RFD MAY SEE SOME
FREEZING RAIN/FREEZING DRIZZLE OVERNIGHT AS TEMPS COOL SLIGHTLY.
THINGS BECOME LESS CERTAIN AFTER DAYBREAK. THE LOW WILL TRACK
NORTHEAST TO NORTH-CENTRAL INDIANA BY FRIDAY AFTERNOON TURNING
WINDS FROM NORTHEAST TO NORTH-NORTHWEST THROUGH THE AFTERNOON. THE
MAIN QUESTION WILL BE HOW QUICKLY AND TO WHAT EXTENT CIGS/VSBY
IMPROVE. WITH THE BOUNDARY STILL IN THE AREA THROUGH THE MORNING
WILL ONLY HAVE VERY MINOR INCREASES IN CIGS/VSBY WITH BETTER
INCREASES DURING THE AFTERNOON AS COLDER AIR FILTERS INTO THE
REGION. SHOWERS/DRIZZLE WILL CONTINUE PERIODICALLY BEFORE TAPERING
OFF DURING THE AFTERNOON. RFD WILL HAVE THE BEST CHANCE OF SEEING
FREEZING RAIN THROUGH THE MORNING...WITH A LOW CHANCE THAT SOME
LIGHT FREEZING RAIN OR FREEZING DRIZZLE WILL MAKE IT INTO THE
CHICAGO TERMINALS DURING THE EARLY AFTERNOON AS COLDER AIR
ARRIVES. MVFR AND POSSIBLY IFR LOOK TO BE IN PLACE FOR FRIDAY
EVENING WITH NORTH-NORTHWEST WINDS.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* HIGH CONFIDENCE IN IFR CONTINUING WITH LOWEST CONDITIONS THROUGH
DAYBREAK. LOW CONFIDENCE WITH SPEED/MAGNITUDE OF CIG/VSBY
IMPROVEMENT THROUGH THE DAY.
* HIGH CONFIDENCE IN PRECIP WINDING DOWN THIS AFTERNOON...MEDIUM-
HIGH CONFIDENCE THAT THREAT FOR -FZRA/FZDZ AT ORD IS LOW.
* HIGH CONFIDENCE IN WIND TRENDS.
MDB
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SAT...WINTRY MIX OF PRECIP FROM MIDDAY ON...WITH A CHANCE OF A
PERIOD OF FREEZING RAIN DURING THE NIGHT. MVFR TO IFR.
SUN...SNOW. MVFR TO IFR.
MON...MVFR CIGS. CHANCE OF SNOW SHOWERS WITH IFR.
TUE...VFR.
WED...VFR BECOMING MVFR CIGS.
THU...MVFR CIGS IMPROVING TO VFR.
TRS
&&
.MARINE...
301 AM CST
LOW PRESSURE CENTERED OVER NORTH-CENTRAL OKLAHOMA WILL TRACK
NORTHEAST ALONG A FRONTAL BOUNDARY WHICH EXTENDS NORTHEAST INTO
NORTHERN INDIANA AND EASTWARD ACROSS LAKE ERIE AND ONTARIO.
MEANWHILE HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE LITTLE
THROUGH THE DAY. THE STRONGEST PRESSURE GRADIENT IS STARTING TO SET
UP EARLY THIS MORNING AND WILL LIKELY RESULT IN AN INCREASE IN
NORTHEAST WINDS ACROSS MUCH OF THE LAKE THROUGH MID MORNING BEFORE
THE PRESSURE GRADIENT EASES. SPEEDS MAY PUSH 30 KT FOR A TIME
THROUGH MID OR LATE MORNING...ESPECIALLY ACROSS CENTRAL SECTIONS OF
THE LAKE. THE LOW WILL PASS SOUTH OF THE LAKE LATER THIS AFTERNOON
AND BEGIN TO WEAKEN WITH THE HIGH WEAKENING AS WELL. ANOTHER SURFACE
LOW WILL DEVELOP OVER THE ARKLATEX SATURDAY AND LIFT NORTHEAST TO
NORTHERN OHIO BY SUNDAY AFTERNOON. A VERY STRONG HIGH WILL THEN
DEVELOP SOUTHWARD INTO THE NORTHERN PLAINS AS THE LOW MOVES INTO NEW
ENGLAND SUNDAY NIGHT. THIS WILL LEAVE LAKE MICHIGAN IN THE PRESSURE
GRADIENT BETWEEN THE TWO SYSTEMS SATURDAY NIGHT AND SUNDAY WITH
COLDER AIR SPILLING ACROSS THE LAKE AS WELL. THIS WILL SET THE STAGE
FOR ANOTHER ROUND OF STRONG WINDS WHICH WILL START OUT NORTHEAST
THEN SHIFT NORTH-NORTHWEST AND EASE UP LATE SUNDAY AFTERNOON. THE
HIGH WILL PASS SOUTH OF THE LAKE TUESDAY BEFORE LOW PRESSURE TRACKS
SOUTHEAST ACROSS THE CANADIAN PRAIRIES AND NORTHERN PLAINS. THIS
SHOULD LEAD TO ANOTHER PERIOD OF INCREASED WINDS...THIS TIME FROM
THE SOUTH AND SOUTHWEST WEDNESDAY. WILL KEEP SPEEDS BELOW GALE FORCE
THROUGH THE PERIOD BUT WILL NEED TO MONITOR FOR SHORT WINDOWS OF
GALE FORCE WINDS SATURDAY NIGHT AND SUNDAY MORNING...AND AGAIN EARLY
WEDNESDAY.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011 UNTIL NOON FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
FLOOD WATCH...ILZ033-ILZ039...9 AM SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002 UNTIL 9 AM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...9 AM SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...LMZ740...9 AM FRIDAY TO 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 AM FRIDAY.
&&
$$
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AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1212 AM CST FRI DEC 20 2013
.DISCUSSION...
813 PM CST
FOR EVENING UPDATE...
MOVED UP START AND EXPANDED SLIGHTLY FREEZING RAIN ADVISORY FOR
FAR NORTH AND NORTH CENTRAL IL TONIGHT-FRIDAY. HAVE ALSO MADE SOME
ADJUSTMENTS TO WEEKEND STORM SYSTEM AS OUTLINED BELOW.
TONIGHT/FRIDAY...
HAVE SLIGHTLY EXPANDED AND STARTED THE FREEZING RAIN ADVISORY
EARLIER TONIGHT AS TEMPERATURES HOVER RIGHT AROUND 32F ACROSS
NORTH CENTRAL AND FAR NORTHEAST ILLINOIS...AND A REPORT OF A LIGHT
GLAZE HAS ALREADY BEEN RECEIVED FROM THE NORTHWEST SIDE OF ROCKFORD.
EVENING GOES WATER VAPOR LOOP DEPICTS A SHORT WAVE CENTER NEARING
THE OZARKS IN THE BROAD MOIST WSW FLOW OVER THE AREA. THIS FEATURE
HAS LED TO AN EXPANSION IN LOW CLOUDS AS WELL AS LIGHT RAIN/DRIZZLE
ACROSS NORTHEAST MO...EASTERN IA...SOUTHERN WI...AND NORTHWEST AND
NORTH CENTRAL IL. THE 00Z DVN SOUNDING SHOWED 25-35KT OF
SOUTHWESTERLY FLOW WITHIN A SATURATED LAYER FROM 750MB TO THE
SURFACE. THE MIN TEMP OBSERVED IN THAT LAYER OF ONLY -1C...SO
CERTAINLY NO ICE CRYSTALS INVOLVED. THE RAP APPEARS TO ANALYZE THIS
WELL AT 285K-290K WITH SATURATED ISENTROPIC ASCENT ACROSS NORTHERN
IL INTO OVERNIGHT...AND THE CONVERGENCE OF THE LOW-LEVEL BOUNDARY
DRAPED ACROSS THE AREA HELPING TO POOL MOISTURE/SATURATION.
THE SURFACE STATIONARY BOUNDARY IS ARCED FROM SOUTH OF PERU TO THE
SOUTH SIDE OF CHICAGO. FOR TEMPERATURES...BELIEVE THAT NORTH OF THE
BOUNDARY WILL BASICALLY HOLD STEADY OR EASE DOWNWARD...WHILE SOUTH
OF THERE MAY EVEN KEEP INCHING UP. FOR POINTS NORTH...THIS CREATES
AN EARLIER AND PROBABLY BETTER POTENTIAL FOR LIGHT ICING THAN
ORIGINALLY FORECAST...AS TEMPS ACROSS NORTH CENTRAL IL ARE ALREADY
32-33F. SO HAVE EXPANDED FREEZING RAIN DEPICTION IN THE GRIDS AND
AGAIN STARTED THE ADVISORY EARLIER.
SATURDAY/SUNDAY...
HAVE MADE ADJUSTMENTS TO THE FORECAST GRIDS FOR SATURDAY INTO SUNDAY
BASED ON MODEL THERMAL PROFILES AND SOUNDINGS...PARTICULARLY THE
1000-850 MB CRITICAL THICKNESS (1300 DM) WHICH IS A KEY INDICATOR
FOR SNOW VERSUS RAIN/ZR/SLEET. THE GFS RUNS TODAY WERE THE COLDEST
WITH THE NAM/ECMWF SHOWING A MUCH MORE DISTINCT WARM NOSE AT 850
MB...BUT EVEN THE GFS WOULD ONLY FAVOR THE FAR NORTHERN CWA FOR A
WINTRY MIX TRANSITIONING TO SNOW/SLEET AND THEN ALL SNOW ON SATURDAY
NIGHT WHERE THERE IS THE BEST OVERLAP WITH FORCING AND LIFT THROUGH
THE DGZ. IN BETWEEN THE FAVORED AREA FOR MORE SIGNIFICANT SNOW/SLEET
ACCUMS AND MAINLY RAIN OVER THE SOUTHEAST HALF OF THE CWA...HAVE
INDICATED A TRANSITION ZONE WHERE A MIXED BAG INCLUDING FREEZING
RAIN IS POSSIBLE. AM CONCERNED THAT IF P-TYPE IS MAINLY ZR FOR A
TIME...THERE COULD BE DECENT ICE ACCRETION...AND THIS WOULD
INCLUDE PARTS OF THE WEST AND NORTHWEST CHICAGO METRO.
FINALLY...SUNDAY MORNING IT APPEARS THAT ALL BUT THE SOUTHEAST
THIRD OF THE CWA WILL TRANSITION OVER TO ALL SNOW AS COLDER AIR
PUSHES IN ALOFT.
THE TWEAKS TO QPF AND WEATHER TYPES AND SNOW AMOUNT GRIDS RESULTED
IN A MUCH TIGHTER SNOWFALL GRADIENT...WITH POTENTIAL FOR AMOUNTS IN
EXCESS OF 6 INCHES IN NORTH CENTRAL/NW AND EXTREME NORTHEASTERN
ILLINOIS...QUICKLY TAPERING TO THE SOUTHEAST. LITTLE OR NO SNOW
ACCUMULATION IS ANTICIPATED IN THE SOUTHEAST THIRD OF THE CWA.
NEEDLESS TO SAY...THIS IS STILL A FLUID SITUATION AND SMALL CHANGES
IN THE TRACK OF THE LOW PRESSURE SYSTEM AND THERMAL PROFILES WILL
HAVE LARGE IMPLICATIONS IN PRECIPITATION TYPE AND AMOUNTS. HAVE MADE
NO CHANGES TO THE WINTER STORM WATCH AND FLOOD WATCH IN EFFECT.
MTF/RC/RATZER
//PREV DISCUSSION...
UPDATED...415 PM CST FOR THIS WEEKEND PORTION
TONIGHT THROUGH FRIDAY NIGHT
UPDATED...1224 PM CST
FRONTAL BOUNDARY IS DRAPED FROM THE CHICAGO METRO AREA WSW TO NEAR
THE QUAD CITIES THIS AFTERNOON. ASCENT IS FORECAST TO INCREASE THIS
EVENING AND TONIGHT ON TOP OF THE BOUNDARY WHICH WILL MEANDER SOME
AS THE SURFACE WAVE LIFTS ACROSS THE REGION. WARM ADVECTION ALOFT
LEAVES LITTLE DOUBT THAT PRECIP WILL MELT ALOFT WITH 3-4C SATURATED
WARM LAYER TEMPS AS FAR NORTH AS THE WI STATE LINE. THE BIG CONCERN
WILL BE SURFACE/GROUND TEMPERATURE TRENDS. TEMPERATURES ARE
EXPECTED TO MOSTLY HOLD STEADY INTO THE LATE EVENING...THEN COLDER
//BELOW FREEZING// SURFACE TEMPS WILL START TO TRICKLE SOUTHEAST
INTO FAR NORTHERN IL AS THE LOW STARTS TO PASS TO OUR SOUTH.
CURRENTLY IT APPEARS THAT ONLY THE FAR REACHES OF THE CWA...
INCLUDING PORTIONS OF OGLE...WINNEBAGO...BOONE...AND MCHENRY
COUNTIES...WILL SEE SURFACE TEMPERATURES FALLING BELOW FREEZING
OVERNIGHT AND WHERE THE CONCERN FOR LIGHT FREEZING RAIN AND LIGHT
ICE ACCUMULATIONS WILL BE. A FREEZING RAIN ADVISORY HAS BEEN ISSUED
FOR THESE COUNTIES...AND EXPECT A GLAZE UP TO A TENTH OF AN INCH OF
ICE FOR THESE AREAS.
BY MID MORNING FRIDAY...TEMPERATURES ARE EXPECTED TO CONTINUE TO
SLOWLY FALL WITH THE LOW DEPARTING EAST. FORCING QUICKLY TAPERS BUT
PERSISTENT LOW LEVEL MOISTURE AND WEAK OMEGA RAISES THE CONCERN FOR
FREEZING DRIZZLE TO SPREAD SOUTH OF THE CURRENT ADVISORY
AREA...PERHAPS AS FAR SOUTH AS THE I-80 CORRIDOR. MID/HIGH LEVEL
MOISTURE WILL BE PRESENT...HOWEVER MID LEVEL DRY LAYER IS EXPECTED
TO INHIBIT SEEDER/FEEDER FROM INTRODUCING ICE INTO THE LOW LEVEL
MOISTURE LAYER...WHICH ONLY HAS TEMPERATURES AS COOL AS -5C.
SURFACE TEMPERATURES WILL BE RIGHT AROUND THE FREEZING MARK. FOR
NOW PLAN ON HIGHLIGHTING AREA WITH AN SPS...AND CANNOT RULE OUT
EXPANSION OF ADVISORY FARTHER SOUTH LATER INTO THE DAY FRIDAY IF
IT APPEARS TEMPERATURES WILL BE COOLER OR IF PRECIP MORE ROBUST.
DEUBELBEISS
FOR THE WEEKEND...
UPDATED...415 PM CST...
A VERY ACTIVE WEATHER PATTERN IS SETTING UP...WITH A FLOOD WATCH
ISSUED FOR THE SOUTHEASTERN PORTIONS OF THE CWA AND A WINTER STORM
WATCH ISSUED FOR THE NORTHERN AND NORTHWESTERN PORTIONS OF THE
CWA.
THE FIRST AREA OF CONCERN WILL BE THE POTENTIAL FOR HEAVY RAINFALL
OVER AT LEAST PORTIONS OF THE AREA. HAVE BEEN MONITORING THE
DEVELOPMENT OF A SOUTHERN STREAM SYSTEM OVER THE SOUTH HIGH PLAINS.
AS OF THURSDAY AFTERNOON...THE SYSTEM IS MOVING ONSHORE INTO
SOUTHERN CALIFORNIA AND WILL FINALLY BE SAMPLED BY THE UPPER AIR
DATA NETWORK. WHILE THE MODELS HAVE PROVIDED A MYRIAD OF SOLUTIONS
FOR THE TRACK OF THIS SYSTEM...MUCH OF THE VIABLE GUIDANCE LOOKED AT
TODAY IS CONVERGING ON THE "WARMER" SOLUTION FOR THE LOCAL
AREA...WITH THE EXCEPTION OF THE GFS WHICH IS THE OUTLIER...PUSHING
THE SYSTEM TO FAR EAST...TOO FAST. THE CONVERGED SOLUTION WILL
TRACK A SERIES OF WAVES ALONG A WARM FRONT DEVELOPING FROM THE SOUTH
HIGH PLAINS INTO NORTHERN ILLINOIS. WARM AIR...MOIST AIR...WITH
TEMPS IN THE UPPER 30S AND DEW POINTS IN THE LOWER TO MIDDLE 30S HAS
ALREADY OVERSPREAD MUCH OF THE AREA. THE WARM FRONT WILL MEANDER
OVER THE AREA AS THE MAIN SFC LOW DEEPENS AND TRACKS ALONG THE
BOUNDARY...CROSSING THE MIDDLE MISSISSIPPI VALLEY BY FRIDAY
MORNING. BY FRIDAY MORNING...THE WARM FRONT SHOULD LAY RIGHT
THROUGH THE MIDDLE OF THE CWA...WITH TEMPS IN THE LOWER 30S ALONG
THE WISCONSIN BORDER...WITH LOWER 40S OVER LOCATIONS SOUTH OF THE
ILLINOIS AND KANKAKEE RIVERS. AS THE SFC LOW TRACKS NEWD ALONG THE
PATH OF THE FRONTAL TROUGH...HIGH PRESSURE WILL BE MOVING OFF THE
SERN COAST. THIS WILL SET UP A WIDE OPEN GULF OF MEXICO...WITH
COPIOUS AMOUNTS OF MOISTURE STREAMING NWD. PWATS ARE FORECAST TO
RISE TO 1.0 TO 1.5 INCHES OVER THE SERN PORTIONS OF THE CWA RIDING
ON A STRONG LOW LEVEL JET...WITH MAX 850MB WINDS OVER 60-70KT.
WHILE THE STRONGEST OF THE LOW LEVEL JET WILL BE TO THE
SOUTH...MOSTLY OVER THE OHIO VALLEY...THERE WILL BE AMPLE ISENTROPIC
LIFT AND MOISTURE TRANSPORT TO SUPPORT AREAS OF HEAVY RAINFALL. AT
THIS POINT...IT LOOKS LIKE THE HEAVIEST RAIN WILL BE OVER THE SERN
PORTIONS OF THE CWA...OUTLINED IN THE FLOOD WATCH ISSUED THIS
AFTERNOON. HOWEVER...THE HEAVY RAIN WILL NOT BE THE ONLY PROBLEM.
WITH COOLER AIR REMAINING AT THE SFC NORTH OF THE WARM FRONT...THE
STRONG ISENTROPIC LIFT ALONG AND NORTH OF THE BOUNDARY WILL FORCE
THE WARMER AIR OVER THE COOLER AIR AT THE SFC...SETTING UP A PERIOD
OF MIXED FREEZING AND FROZEN PCPN. THE EXACT LOCATION OF THE WINTRY
MIX OF PCPN STILL REMAINS A LITTLE TOUGH TO NARROW DOWN...BUT MOST
OF THE AREA NORTH OF THE KANKAKEE AND ILLINOIS RIVERS WILL SEE A
LEAST SOME PERIODS OF THE WINTRY MIX PCPN...WITH THE ROCKFORD AREA
LIKELY NOT SEEING ANY LIQUID WHILE THE CHICAGO METRO SHOULD SEE SOME
AND AND SOME OF THE WINTRY MIX.
AS THE HEAVY RAIN SITUATION IS WINDING DOWN SATURDAY NIGHT OR EARLY
SUNDAY MORNING...THE MAIN FORECAST CONCERN WILL SHIFT TO THE
POTENTIAL FOR HEAVY SNOWFALL. THE SRN STREAM SYSTEM NOT ONLY WILL
BE RESPONSIBLE FOR DRAWING MOISTURE NORTHWARD...THERE SHOULD BE SOME
PHASING WITH A NORTHERN STREAM SHORTWAVE DROPPING OUT OF THE NRN
PLAINS. THIS SHOULD LEAD TO THE DEVELOPMENT OF A WEAK SECONDARY
CIRCULATION OVER NRN IL BY SUNDAY MORNING...ENHANCING THE DRAW OF
COOLER AIR FROM THE NORTH. THE STRONGER COLD ADVECTION AND A STRONG
DEFORMATION ZONE ARE ADVERTISED TO SET UP OVER NRN IL/SRN WI WHICH
WILL BE THE PRIMARY FOCUSING ELEMENTS FOR A BAND OF HEAVY SNOW. AT
THIS POINT...BASED ON THE GOOD CONSENSUS OF THE NAM AND
ECMWF...WHICH WOULD WOULD INDICATE AN AXIS OF HEAVIER SNOW GENERALLY
FROM ERN IOWA TO SERN WISCONSIN. ALL THINGS CONSIDERED...CONFIDENCE
IS BECOMING HIGH ENOUGH FOR IN EXCESS OF 6 INCHES OF SNOW OVER THE
NRN AND NWRN PORTIONS OF THE CWA...AS OUTLINED IN THE WINTER STORM
WATCH ISSUED THIS AFTERNOON. CURRENTLY ANTICIPATE THAT THE ENTIRE
CWA WILL SEE AT LEAST SOME SNOW...WITH 2 TO 4 INCHES ALONG A LINE
FROM CHICAGO TO PONTIAC AND 1 TO 2 INCHES FROM VALPARAISO TO
PONTIAC...TAPERING OFF TO AN INCH OR LESS OVER THE FAR SERN PORTIONS
OF THE CWA.
AK
LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...
UPDATED 316 PM CST
SUNDAY NIGHT...
GUIDANCE CONTINUES TO BE CONSISTENT IN DELIVERING A SHOT OF ARCTIC
AIR IN THE WAKE OF THE SIGNIFICANT WEEKEND STORM. A NORTHERN STREAM
TROUGH CURRENTLY NEAR THE NORTH POLE WILL DIG IN OVER THE NORTH
CENTRAL CONUS COUPLED WITH A ~1040 MB HIGH DROPPING SOUTH FROM THE
NORTHERN PLAINS. ALL OF THE SYSTEM SNOWS SHOULD BE OFF TO THE EAST
SUNDAY NIGHT...BUT POSITIVE VORTICITY ADVECTION FROM SHORT WAVES
ROTATING AROUND DEEP UPPER TROUGH COULD SQUEEZE OUT SOME LIGHT SNOW
OR FLURRIES IN THE ARCTIC AIR MASS. THE ECMWF CONTINUES TO BE MOST
BULLISH IN SQUEEZING OUT LIGHT QPF OVER THE AREA. THERE ALSO COULD
BE A BRIEF PERIOD OF FAVORABLE LAKE EFFECT CONDITIONS FOR PORTIONS
OF NW INDIANA DEPENDING ON IF WINDS CAN REMAIN CLOSER TO DUE NORTH
BEFORE BACKING WEST NORTHWEST. TEMPERATURES WILL PLUMMET IN STRONG
COLD ADVECTION BUT PERSISTENT NW WINDS AND CLOUD COVER COULD LIMIT
HOW FAR THEY FALL. WITH THE RAPIDLY FALLING TEMPERATURES SUNDAY
NIGHT...THERE COULD VERY WELL BE A FLASH FREEZE OF ANY REMAINING
MOISTURE ON THE GROUND.
MONDAY...
MAINTAINED A SLIGHT CHANCE OF FLURRIES ON MONDAY MORNING AS THE DEEP
UPPER TROUGH WILL BE OVERHEAD AND IT MAY NOT BE HARD TO SQUEEZE OUT
DENDRITES DESPITE THE COLD DRY AIR MASS. ALSO GUIDANCE INDICATES A
FAIRLY STOUT WAVE FOCUSED INTO THE NORTHEAST CWA AND WISCONSIN...SO
FELT COMFORTABLE WITH THE SLIGHT CHANCE POP FROM GUIDANCE BLEND
INITIALIZATION FOR NORTHEAST IL AND EXTREME NW INDIANA. HIGH
TEMPERATURES MONDAY AND LOWS MONDAY NIGHT WILL BE COLD
EVERYWHERE...BUT HOW COLD WILL DEPEND ON WHICH AREAS MAINTAIN
SUBSTANTIAL SNOW PACK AFTER THE WEEKEND SYSTEM. AT THIS TIME...IT
APPEARS THAT THE NORTHERN CWA WOULD HAVE THE BEST CHANCE. WITH
SURFACE HIGH BEING NEAR OR OVER THE AREA AND NO MORE THAN PARTLY
CLOUDY SKIES EXPECTED...DROPPED LOW TEMPERATURES MONDAY NIGHT FROM
PREVIOUS FORECAST TO 5 TO 10 BELOW WEST OF THE FOX VALLEY. STAYED
MORE CONSERVATIVE IN THE SOUTHERN CWA WHERE LITTLE OR NO SNOW COVER
SHOULD BE LEFT. TO NOTE...THE ECMWF AND GFS WHICH HAVE CLEAR SKIES
HAVE LOWS IN THE COLDEST SPOTS 10 DEGREES COLDER THAN IN FORECAST
GRIDS...WHILE CANADIAN MODEL KEEPS CLOUD COVER AND IS A GOOD DEAL
WARMER.
TUESDAY NIGHT THROUGH THURSDAY...
AFTER A BITTERLY COLD START TO CHRISTMAS EVE DAY...SOUTHWEST WARM
ADVECTION BEHIND TROUGH DEPARTING TO THE EAST WILL ENABLE A DECENT
AFTERNOON TEMPERATURE RECOVERY...BUT STILL WELL BELOW CLIMO. COULD
SEE TEMPERATURES BEING A BIT WARMER THAN CURRENTLY FORECAST IN AREAS
WITHOUT SNOW COVER. WILL HAVE TO WATCH FOR A NORTHERN STREAM WAVE
BEING A BIT FARTHER SOUTH THAN MODEL CONSENSUS ON CHRISTMAS EVE
NIGHT...BUT WITH ECMWF TRENDING SOUTH...INDICATED A SLIGHT CHANCE OF
LIGHT SNOW NEAR THE WISCONSIN BORDER. THIS FEATURE COULD THEN GO ON
TO RESULT IN AT LEAST SOME LIGHT SNOW OR FLURRIES IN THE AIR FOR THE
ENTIRE AREA ON CHRISTMAS DAY. THIS WOULD BE A CONSOLATION PRIZE FOR
AREAS THAT LOSE THEIR SNOW COVER THIS WEEKEND...BUT FOR AREAS THAT
KEEP AT LEAST 1 INCH OF SNOW ON THE GROUND...A WHITE CHRISTMAS IS
HIGHLY LIKELY. TEMPERATURES WILL MODERATE TO NEAR NORMAL ON
CHRISTMAS DAY...WITH ANOTHER SHOT OF ARCTIC AIR POSSIBLE ON THURSDAY
BEHIND THE CHRISTMAS DAY SYSTEM.
CONFIDENCE IN A WHITE CHRISTMAS FOR AREAS THAT MAINTAIN AT LEAST 1
INCH OF SNOW COVER THIS WEEKEND...HIGH.
RC
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* VSBY AROUND 1SM WITH CIGS 002-004 THROUGH THE NIGHT WITH MINIMAL
IMPROVEMENT EXPECTED AFTER DAYBREAK.
* PERIODIC -SHRA/-DZ THROUGH MIDDAY FRIDAY WITH DECREASING CHANCES
THROUGH THE AFTERNOON. LOW CHANCE FOR SOME -FZRA/FZDZ FRIDAY
AFTERNOON.
* NORTH-NORTHEAST WINDS PERSIST THROUGH THE AFTERNOON WITH SPEEDS
INCREASING TO NEAR 10 KT BY MIDDAY.
* WINDS SHIFT NORTH-NORTHWEST FRIDAY EVENING WITH SOME CIG/VSBY
IMPROVEMENT POSSIBLE.
MDB
//DISCUSSION...UPDATED 06Z...
MESSY CONDITIONS CONTINUE ACROSS THE TERMINALS TONIGHT WITH A
FRONTAL BOUNDARY STRETCHING FROM LOW PRESSURE OVER OKLAHOMA TO
ROUGHLY A KEOK TO KC75 TO KVPZ LINE. ABUNDANT MOISTURE AND LIFT
CONTINUE OVER THE BOUNDARY BRINGING RAIN SHOWERS AND AREAS OF
DRIZZLE TO THE TERMINALS. VSBY IS LOWEST RIGHT ALONG THE BOUNDARY
WITH GYY AROUND 1/4SM AND THIS WILL LIKELY PERSIST AS LONG AS THE
BOUNDARY IS NEARBY...WHICH AT THIS POINT LOOKS TO BE FOR MUCH OF
THE OVERNIGHT. AREAS NORTH HAVE SEEN VSBY GENERALLY AROUND A MILE
AND THIS SHOULD BE THE TREND THROUGH THE NIGHT...THOUGH THERE MAY
BE SOME DOWNWARD FLUCTUATIONS AT TIMES. CIGS SHOULD STAY STEADY
IN THE 002-004 RANGE THROUGH THE NIGHT AS WELL. RFD MAY SEE SOME
FREEZING RAIN/FREEZING DRIZZLE OVERNIGHT AS TEMPS COOL SLIGHTLY.
THINGS BECOME LESS CERTAIN AFTER DAYBREAK. THE LOW WILL TRACK
NORTHEAST TO NORTH-CENTRAL INDIANA BY FRIDAY AFTERNOON TURNING
WINDS FROM NORTHEAST TO NORTH-NORTHWEST THROUGH THE AFTERNOON. THE
MAIN QUESTION WILL BE HOW QUICKLY AND TO WHAT EXTENT CIGS/VSBY
IMPROVE. WITH THE BOUNDARY STILL IN THE AREA THROUGH THE MORNING
WILL ONLY HAVE VERY MINOR INCREASES IN CIGS/VSBY WITH BETTER
INCREASES DURING THE AFTERNOON AS COLDER AIR FILTERS INTO THE
REGION. SHOWERS/DRIZZLE WILL CONTINUE PERIODICALLY BEFORE TAPERING
OFF DURING THE AFTERNOON. RFD WILL HAVE THE BEST CHANCE OF SEEING
FREEZING RAIN THROUGH THE MORNING...WITH A LOW CHANCE THAT SOME
LIGHT FREEZING RAIN OR FREEZING DRIZZLE WILL MAKE IT INTO THE
CHICAGO TERMINALS DURING THE EARLY AFTERNOON AS COLDER AIR
ARRIVES. MVFR AND POSSIBLY IFR LOOK TO BE IN PLACE FOR FRIDAY
EVENING WITH NORTH-NORTHWEST WINDS.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE VSBY AROUND 1SM AND CIGS 002-004 THROUGH THE
OVERNIGHT. LOW CONFIDENCE IN DEGREE OF ANY VARIABILITY AND
TIMING/MAGNITUDE OF IMPROVEMENT AFTER DAYBREAK.
* HIGH CONFIDENCE IN PERIODIC -SHRA/-DZ THROUGH MIDDAY
FRIDAY...WITH LOW CONFIDENCE IN -FZRA/-FZDA EARLY FRIDAY
AFTERNOON.
* HIGH CONFIDENCE IN WIND TRENDS.
MDB
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SAT...WINTRY MIX OF PRECIP FROM MIDDAY ON...WITH A CHANCE OF A
PERIOD OF FREEZING RAIN DURING THE NIGHT. MVFR TO IFR.
SUN...SNOW. MVFR TO IFR.
MON...MVFR CIGS. CHANCE OF SNOW SHOWERS WITH IFR.
TUE...VFR.
WED...VFR BECOMING MVFR CIGS.
THU...MVFR CIGS IMPROVING TO VFR.
TRS
&&
.MARINE...
308 PM CST
THERE ARE TWO LOWS SET TO MOVE FROM THE SOUTHERN PLAINS TO THE
LOWER/EASTERN GREAT LAKES REGION THROUGH SUNDAY. THE SECOND ONE WILL
HAVE A LARGER INFLUENCE ON THE WINDS ACROSS THE LAKE...NAMELY
SATURDAY NIGHT THROUGH EARLY MONDAY. AS WINDS TURN
NORTHERLY BEHIND THIS LOW...SPEEDS WILL INCREASE BUT ARE LIKELY TO
REMAIN BELOW GALES ON SUNDAY...ALTHOUGH COULD BE CLOSE ESPECIALLY
IF THE SYSTEM IS DEEPER THAN FORECAST.
IN THE IMMEDIATE NEAR TERM...A FRONT WILL REMAIN DRAPED ACROSS THE
SOUTHERN TWO TO FOUR OPEN WATER ZONES OF LAKE MICHIGAN...WHERE
WINDS WILL BE SOMEWHAT VARIABLE IN SPEED. THIS FRONT WILL INCH
SOUTHWARD FRIDAY MORNING IN THE WAKE OF THE FIRST LOW.
A WINTRY MIX IS EXPECTED ACROSS THE SOUTHERN TWO-THIRDS OF THE
LAKE WITH BOTH SYSTEMS...TONIGHT AND FRIDAY AND AGAIN SATURDAY
NIGHT WHICH SHOULD CHANGE TO ALL SNOW SUNDAY.
IN THE WAKE OF THESE SYSTEMS...STRONG HIGH PRESSURE WILL PASS TO
THE SOUTH OF THE REGION BEFORE LIKELY STRONG SOUTHERLY WINDS TAKE
EFFECT ACROSS THE ENTIRE LAKE SOMETIME CHRISTMAS EVE NIGHT INTO
CHRISTMAS.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011 UNTIL NOON FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
FLOOD WATCH...ILZ033-ILZ039...9 AM SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002 UNTIL 9 AM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...9 AM SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...LMZ740...9 AM FRIDAY TO 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 AM FRIDAY.
&&
$$
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WWW.TWITTER.COM/NWSCHICAGO
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AREA FORECAST DISCUSSION
NWS INDIANAPOLIS IN
320 AM EST FRI DEC 20 2013
.UPDATE...
THE LONG TERM SECTION HAS BEEN UPDATED BELOW.
&&
.SYNOPSIS...
ISSUED AT 245 AM EST FRI DEC 20 2013
AN ACTIVE...WET...WEATHER PATTERN WILL BE IN PLACE FOR CENTRAL
INDIANA FOR THE NEXT COUPLE OF DAYS...BRINGING ABUNDANT RAINFALL.
A FRONTAL BOUNDARY IS EXPECTED TO PUSH ACROSS INDIANA VERY SLOWLY
OVER THE NEXT FEW DAYS. AS THE FRONT SLOWLY PASSES TO THE
SOUTHEAST THROUGH SUNDAY SEVERAL UPPER LEVEL DISTURBANCES ARE
EXPECTED TO PUSH ALONG THE FRONT...RESULTING IN RAIN. VERY WARM AND
MOIST AIR AHEAD OF THE FRONT WILL PROVIDE AMPLE MOISTURE FOR
WIDESPREAD RAINFALL...SOME OF WHICH COULD BE HEAVY AND RESULT IN
FLOODING.
COLD HIGH PRESSURE WILL BUILD INTO THE REGION TO START NEXT WEEK.
A WEAK LOW PRESSURE TROUGH WILL MOVE INTO THE GREAT LAKES AND OHIO
VALLEY NEXT THURSDAY AND MAY PRODUCE SOME LIGHT SNOW.
&&
.NEAR TERM /TODAY/...
ISSUED AT 245 AM EST FRI DEC 20 2013
SURFACE ANALYSIS EARLY THIS MORNING SHOWS LOW PRESSURE OVER
MISSOURI WITH A WARM FRONT EXTENDING NORTHEAST INTO NORTHERN
ILLINOIS AND SOUTHERN MICHIGAN. ABUNDANT CLOUD COVER WAS STREAMING
NORTHWARD INTO THE OHIO VALLEY AHEAD OF THE FRONT. WATER VAPOR
IMAGERY SHOWS A DEEPENING TROUGH OVER THE AMERICAN
SOUTHWEST...WITH A STREAM OF TROPICAL MOISTURE STRETCHING ACROSS
TEXAS INTO THE OHIO VALLEY. RADAR SHOWS SCATTERED SHOWERS DEVELOPING ACROSS
INDIANA AND NORTHERN ILLINOIS. DEW POINTS WERE IN THE MIDDLE 40S
AS SURFACE FLOW WAS FROM THE SOUTH ACROSS THE FORECAST AREA.
GFS AND NAM FAIL TO SHOW MUCH IN THE WAY OF ORGANIZED SHORT WAVES
PUSHING ACROSS THE FORECAST AREA TODAY. HOWEVER THE 300K GFS
ISENTROPIC SURFACE SHOWS GOOD LIFT STARTING TODAY WITH A SURGE OF
MOISTURE...SPECIFIC HUMIDITIES OVER 5 G/KG...PUSHING INTO THE
AREA THIS MORNING. FORECAST SOUNDINGS SHOW DEEP MOISTURE AVAILABLE
AROUND 12Z...WITH LOWER LEVEL MOISTURE LINGERING ACROSS THE AREA
THROUGH THE DAY. MODERATE LOWER LEVEL JET...NEAR 40 KNTS...IS
EXPECTED TO REMAIN IN THE AREA TODAY. GOOD LOWER LEVEL CONVERGENCE
IS SEEN IN THE Q VECTORS TODAY AS THE SURFACE FRONTAL BOUNDARY
SAGS EASTWARD ACROSS INDIANA ALONG WITH A WEAK LOW PRESSURE CENTER.
THUS WITH THESE FAVORABLE INGREDIENTS FOR PRECIP WILL TREND TOWARD
THE 100 POPS AS SEEN IN MUCH OF THE GUIDANCE. WITH THE EXPECTED
RAINFALL AMID THE STRONG WARM AIR ADVECTION...WILL TREND HIGHS AT OR
ABOVE GUIDANCE.
&&
.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
ISSUED AT 245 AM EST FRI DEC 20 2013
A VERY ACTIVE AND VERY WET PATTERN LOOKS TO BE IN PLACE THROUGH
SUNDAY AFTERNOON. MAIN FORECAST CHALLENGE WILL BE POPS. THE STRONG
WAVE OVER THE AMERICAN SOUTHWEST IS EXPECTED TO PUSH QUICKLY TOWARD
THE OHIO VALLEY AMID THE SOUTHWEST FLOW ON FRIDAY NIGHT...AND
THEN PASS ACROSS INDIANA ON SATURDAY NIGHT. A VERY FAVORABLE SET UP
FOR RAIN REMAINS IN PLACE. AT THE SURFACE...A FRONTAL BOUNDARY
REMAINS IN PLACE ACROSS INDIANA. THIS RESULTS IN GOOD LOWER LEVEL Q
VECTOR CONVERGENCE. THE PREVIOUSLY MENTIONED TROPICAL FLOW ALOFT WILL
HELP PROVIDE AMPLE MOISTURE. PRECIPITABLE WATER TONIGHT THROUGH
SATURDAY NIGHT REMAINS OVER 1 INCH WHICH IS OVER 100 PERCENT OF
NORMAL. THIS SHOWS WE ARE DEALING WITH A VERY MOIST AIR MASS FOR
THIS TIME OF YEAR. FORECAST SOUNDINGS SHOW DEEP SATURATION
PERSISTING ACROSS THE AREA THROUGH AT LEAST SATURDAY NIGHT. NAM AND
GFS ALSO SHOW A VERY STRONG LOWER LEVEL JET NEAR 70 KNTS PUSHING
THROUGH THE OHIO VALLEY ON SATURDAY AND SATURDAY NIGHT. AGAIN...ALL
OF THESE THINGS ARE QUITE FAVORABLE FOR RAIN...AND SOME OF THE RAIN
SHOULD BE HEAVY. VERY IMPRESSED WITH NAM RAW OUTPUT SUGGESTING 17-20
UBAR/S OF LIFT ON SATURDAY AFTERNOON AND SATURDAY NIGHT. THAT SPITS
OUT OVER 2.5 INCHES OF RAIN IF IT VERIFIES. BOTTOM LINE HERE IS VERY
STRONG FORCING WILL BE PUSHING THROUGH. THE ONGOING FLOOD WATCH
LOOKS LIKE A GOOD BET. WOULD NOT BE SURPRISED TO SEE AREAL FLOOD
WARNINGS THIS WEEKEND. INTERESTING FACT FOR IND...IN DECEMBER THE
NORMAL AMOUNT OF PRECIPITATION FOR THE ENTIRE MONTH IS 3.17 INCHES.
WE COULD SEE 2/3RDS OR MORE OF THAT ON FRI NIGHT-SAT-SATURDAY NIGHT.
WILL USE 100 POPS. GIVEN THE CLOUDS AND PRECIP...WILL TREND HIGHS
COOLER THAN GUIDANCE AND LOWS WARMER.
THE STRONGEST FORCING DEPARTS THE AREA TO THE NORTHEAST ON SUNDAY
AS A DRY SLOT BEGINS TO INTRUDE FROM THE SOUTHWEST. FORECAST
SOUNDINGS SHOW SUBSIDENCE BUILDING ALOFT AS THEY BEGIN TO DRY
OUT...TOP DOWN. LOWER LEVELS REMAIN SATURATED...INDICATIVE OF
TRAPPED STRATOCU AMID COLD AIR ADVECTION. FORECAST SOUNDINGS BEGIN
TO TAKE A TUMBLE ON SUNDAY AFTERNOON ALSO...AS THE SURFACE COLD
FRONT PUSHES SOUTHEAST OF THE OHIO VALLEY. BY 00Z MONDAY...THE
MAJORITY OF THE FORECAST SOUNDINGS ARE BELOW FREEZING AND DEEP
MOISTURE IS LOST AS SURFACE HIGH PRESSURE OVER THE PLAINS STATES
PROVIDES A COLD NORTHWEST FLOW OF COLD AIR AS 850MB TEMPS FALL
BACK TO NEAR 0C. MOISTURE ON SUNDAY AND SUNDAY NIGHT APPEARS
LIMITED AS PRECIPITABLE WATER IS REDUCED TO MORE NORMAL LEVELS AND
DRY AIR CONTINUES TO STREAM INTO THE COLUMN. HOWEVER WITH
LINGERING LOWER LEVEL MOISTURE AND BROAD CYCLONIC FLOW IN PLACE ON
SUNDAY AND SUNDAY NIGHT...CANNOT RULE OUT LIGHT PRECIPITATION
AMOUNTS. WILL STICK CLOSE TO GUIDANCE POPS AT THOSE TIMES. GIVEN
THE CHANGE IN AIR MASS WILL TREND COOLER THAN THE MAVMOS ON SUNDAY
HIGHS AND PROBABLY COOLER THAN MEXMOS LOWS ON SUNDAY NIGHT GIVEN
THE EXPECTED COLD AIR ADVECTION.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
ISSUED AT 315 AM EST FRI DEC 20 2013
MODELS ARE IN GOOD AGREEMENT EARLY BUT VARY A DECENT BIT NEAR THE
END OF THE FORECAST PERIOD IN REGARDS TO TEMPERATURES. GENERALLY DID
NOT DEVIATE FROM ALLBLEND WITH EXCEPTIONS MENTIONED BELOW. THE LONG
TERM STARTS WITH CANADIAN HIGH PRESSURE BUILDING OVER THE AREA. THIS
WILL MOVE ACROSS CENTRAL INDIANA THROUGH TUESDAY NIGHT KEEPING DRY
WEATHER IN THE FORECAST AND BELOW NORMAL TEMPERATURES WITH HIGHS
MAINLY IN THE 20S. BY WEDNESDAY THE HIGH WILL BE OFF TO THE EAST
ALLOWING TEMPERATURES TO CLIMB INTO THE MID TO UPPER 30S. AFTER THAT
AN UPPER LOW WILL SWING THROUGH ONTARIO AND BRING A COLD FRONT
THROUGH INDIANA BETWEEN WEDNESDAY NIGHT AND THURSDAY ALONG WITH A
WEAK UPPER WAVE. THIS WILL BRING LOW CHANCES FOR SNOW TO THE AREA
AND A REINFORCING SHOT OF COLD AIR FOR THE END OF THE WEEK. TRENDED
TEMPERATURES LOWER THAN ALLBLEND ON THURSDAY TO LEAN CLOSER TO THE
COLDER TEMPERATURES OF THE ECMWF WHICH MATCH THE UPPER PATTERN
BETTER.
&&
.AVIATION /DISCUSSION FOR 200900Z TAF ISSUANCE/...
ISSUED AT 315 AM EST FRI DEC 20 2013
UPDATED TO IMPROVE CONDITIONS FOR THE NEXT FEW HOURS AS THEY ARE
FALLING SLOWER THAN ANTICIPATED. WITH THE FRONT TO THE NORTH OF
THE SITES MAY TAKE LONGER FOR POOR FLYING CONDITIONS TO DEVELOP. PREVIOUS
DISCUSSION FOLLOWS...
STEADILY DETERIORATING CONDITIONS FOR AVIATORS WITH LIFR
CONDITIONS DEVELOPING FOR MUCH OF FRIDAY.
FRONTAL BOUNDARY EXTENDING FROM SOUTHERN LOWER MICHIGAN W/SW INTO
NORTH CENTRAL ILLINOIS LATE THIS EVENING. STRENGTHENING LOW LEVEL
JET CONTINUES TO BRING GULF MOISTURE INTO THE OHIO VALLEY. RH
PROGS AT 950/925MB OFF THE RAP INDICATE SUBTLY DRIER AIR LIFTING
NORTH ACROSS CENTRAL INDIANA...AND THIS HAS LIKELY DELAYED
CEILINGS FROM FALLING BELOW VFR. AS DEEPER MOISTURE AND LIGHT RAIN
SHOWERS EXPAND INTO THE FORECAST AREA OVERNIGHT...EXPECT IFR
CEILINGS TO BECOME PREVALENT PRIOR TO DAYBREAK...DROPPING TO 500FT
OR LOWER AS THE INVERSION STRENGTHENS DURING THE MORNING.
RAIN WILL CONTINUE AS WELL THROUGH MUCH OF THE DAY AS A SURFACE
WAVE TRAVERSES THE NEARLY STATIONARY BOUNDARY JUST TO THE
NORTHWEST OF THE REGION. SLIGHTLY DRIER AIR ALOFT ATTEMPTS TO
BRIEFLY WORK INTO THE REGION BEHIND THE SURFACE WAVE LATE FRIDAY
AFTERNOON BUT WITH SATURATED CONDITIONS TRAPPED BENEATH THE
INVERSION...MAY ONLY SEE RAIN LIGHTEN TO DRIZZLE FOR A FEW HOURS.
MORE WIDESPREAD AND HEAVIER RAINFALL WILL QUICKLY EXPAND INTO
CENTRAL INDIANA NEAR THE END OF THE FORECAST PERIOD AS DEEPER
MOISTURE ADVECTS INTO THE OHIO VALLEY.
LOW LEVEL WIND SHEAR WILL REMAIN A FACTOR THROUGH THE FIRST 12
HOURS OF THE FORECAST WITH THE PRESENCE OF THE LOW LEVEL JET. RAP
INDICATING POTENTIAL FOR SOUTHWEST WINDS TO APPROACH 60KTS
OVERNIGHT IN THE 2-3KFT LAYER. LLWS CONCERNS WILL NOT DIMINISH
UNTIL EARLY AFTERNOON AS THE LOW LEVEL JET WEAKENS. SOUTHWEST
WINDS AT 10 TO 15 KTS ARE EXPECTED THROUGH MUCH OF THE PERIOD...
VEERING TO MORE OF A WESTERLY DIRECTION FRIDAY EVENING AS THE
BOUNDARY SAGS INTO THE FORECAST AREA.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR INZ021-
028>031-035>049-051>057-060>065-067>072.
&&
$$
SYNOPSIS...PUMA
NEAR TERM...PUMA
SHORT TERM...PUMA
LONG TERM....CP
AVIATION...RYAN/CP
VISIT US AT HTTP://WWW.WEATHER.GOV/IND
FOLLOW US ON TWITTER AND YOUTUBE AT:
WWW.TWITTER.COM/NWSINDIANAPOLIS
WWW.YOUTUBE.COM/NWSINDIANAPOLIS
AREA FORECAST DISCUSSION
NWS INDIANAPOLIS IN
245 AM EST FRI DEC 20 2013
.UPDATE...
THE SYNOPSIS...NEAR TERM AND SHORT TERM SECTIONS HAVE BEEN UPDATED BELOW.
&&
.SYNOPSIS...
ISSUED AT 245 AM EST FRI DEC 20 2013
AN ACTIVE...WET...WEATHER PATTERN WILL BE IN PLACE FOR CENTRAL
INDIANA FOR THE NEXT COUPLE OF DAYS...BRINGING ABUNDANT RAINFALL.
A FRONTAL BOUNDARY IS EXPECTED TO PUSH ACROSS INDIANA VERY SLOWLY
OVER THE NEXT FEW DAYS. AS THE FRONT SLOWLY PASSES TO THE
SOUTHEAST THROUGH SUNDAY SEVERAL UPPER LEVEL DISTURBANCES ARE
EXPECTED TO PUSH ALONG THE FRONT...RESULTING IN RAIN. VERY WARM AND
MOIST AIR AHEAD OF THE FRONT WILL PROVIDE AMPLE MOISTURE FOR
WIDESPREAD RAINFALL...SOME OF WHICH COULD BE HEAVY AND RESULT IN
FLOODING.
COLD HIGH PRESSURE WILL BUILD INTO THE REGION TO START NEXT WEEK.
A WEAK LOW PRESSURE TROUGH WILL MOVE INTO THE GREAT LAKES AND OHIO
VALLEY NEXT THURSDAY AND MAY PRODUCE SOME LIGHT SNOW.
&&
.NEAR TERM /TODAY/...
ISSUED AT 245 AM EST FRI DEC 20 2013
SURFACE ANALYSIS EARLY THIS MORNING SHOWS LOW PRESSURE OVER
MISSOURI WITH A WARM FRONT EXTENDING NORTHEAST INTO NORTHERN
ILLINOIS AND SOUTHERN MICHIGAN. ABUNDANT CLOUD COVER WAS STREAMING
NORTHWARD INTO THE OHIO VALLEY AHEAD OF THE FRONT. WATER VAPOR
IMAGERY SHOWS A DEEPENING TROUGH OVER THE AMERICAN
SOUTHWEST...WITH A STREAM OF TROPICAL MOISTURE STRETCHING ACROSS
TEXAS INTO THE OHIO VALLEY. RADAR SHOWS SCATTERED SHOWERS DEVELOPING ACROSS
INDIANA AND NORTHERN ILLINOIS. DEW POINTS WERE IN THE MIDDLE 40S
AS SURFACE FLOW WAS FROM THE SOUTH ACROSS THE FORECAST AREA.
GFS AND NAM FAIL TO SHOW MUCH IN THE WAY OF ORGANIZED SHORT WAVES
PUSHING ACROSS THE FORECAST AREA TODAY. HOWEVER THE 300K GFS
ISENTROPIC SURFACE SHOWS GOOD LIFT STARTING TODAY WITH A SURGE OF
MOISTURE...SPECIFIC HUMIDITIES OVER 5 G/KG...PUSHING INTO THE
AREA THIS MORNING. FORECAST SOUNDINGS SHOW DEEP MOISTURE AVAILABLE
AROUND 12Z...WITH LOWER LEVEL MOISTURE LINGERING ACROSS THE AREA
THROUGH THE DAY. MODERATE LOWER LEVEL JET...NEAR 40 KNTS...IS
EXPECTED TO REMAIN IN THE AREA TODAY. GOOD LOWER LEVEL CONVERGENCE
IS SEEN IN THE Q VECTORS TODAY AS THE SURFACE FRONTAL BOUNDARY
SAGS EASTWARD ACROSS INDIANA ALONG WITH A WEAK LOW PRESSURE CENTER.
THUS WITH THESE FAVORABLE INGREDIENTS FOR PRECIP WILL TREND TOWARD
THE 100 POPS AS SEEN IN MUCH OF THE GUIDANCE. WITH THE EXPECTED
RAINFALL AMID THE STRONG WARM AIR ADVECTION...WILL TREND HIGHS AT OR
ABOVE GUIDANCE.
&&
.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
ISSUED AT 245 AM EST FRI DEC 20 2013
A VERY ACTIVE AND VERY WET PATTERN LOOKS TO BE IN PLACE THROUGH
SUNDAY AFTERNOON. MAIN FORECAST CHALLENGE WILL BE POPS. THE STRONG
WAVE OVER THE AMERICAN SOUTHWEST IS EXPECTED TO PUSH QUICKLY TOWARD
THE OHIO VALLEY AMID THE SOUTHWEST FLOW ON FRIDAY NIGHT...AND
THEN PASS ACROSS INDIANA ON SATURDAY NIGHT. A VERY FAVORABLE SET UP
FOR RAIN REMAINS IN PLACE. AT THE SURFACE...A FRONTAL BOUNDARY
REMAINS IN PLACE ACROSS INDIANA. THIS RESULTS IN GOOD LOWER LEVEL Q
VECTOR CONVERGENCE. THE PREVIOUSLY MENTIONED TROPICAL FLOW ALOFT WILL
HELP PROVIDE AMPLE MOISTURE. PRECIPITABLE WATER TONIGHT THROUGH
SATURDAY NIGHT REMAINS OVER 1 INCH WHICH IS OVER 100 PERCENT OF
NORMAL. THIS SHOWS WE ARE DEALING WITH A VERY MOIST AIR MASS FOR
THIS TIME OF YEAR. FORECAST SOUNDINGS SHOW DEEP SATURATION
PERSISTING ACROSS THE AREA THROUGH AT LEAST SATURDAY NIGHT. NAM AND
GFS ALSO SHOW A VERY STRONG LOWER LEVEL JET NEAR 70 KNTS PUSHING
THROUGH THE OHIO VALLEY ON SATURDAY AND SATURDAY NIGHT. AGAIN...ALL
OF THESE THINGS ARE QUITE FAVORABLE FOR RAIN...AND SOME OF THE RAIN
SHOULD BE HEAVY. VERY IMPRESSED WITH NAM RAW OUTPUT SUGGESTING 17-20
UBAR/S OF LIFT ON SATURDAY AFTERNOON AND SATURDAY NIGHT. THAT SPITS
OUT OVER 2.5 INCHES OF RAIN IF IT VERIFIES. BOTTOM LINE HERE IS VERY
STRONG FORCING WILL BE PUSHING THROUGH. THE ONGOING FLOOD WATCH
LOOKS LIKE A GOOD BET. WOULD NOT BE SURPRISED TO SEE AREAL FLOOD
WARNINGS THIS WEEKEND. INTERESTING FACT FOR IND...IN DECEMBER THE
NORMAL AMOUNT OF PRECIPITATION FOR THE ENTIRE MONTH IS 3.17 INCHES.
WE COULD SEE 2/3RDS OR MORE OF THAT ON FRI NIGHT-SAT-SATURDAY NIGHT.
WILL USE 100 POPS. GIVEN THE CLOUDS AND PRECIP...WILL TREND HIGHS
COOLER THAN GUIDANCE AND LOWS WARMER.
THE STRONGEST FORCING DEPARTS THE AREA TO THE NORTHEAST ON SUNDAY
AS A DRY SLOT BEGINS TO INTRUDE FROM THE SOUTHWEST. FORECAST
SOUNDINGS SHOW SUBSIDENCE BUILDING ALOFT AS THEY BEGIN TO DRY
OUT...TOP DOWN. LOWER LEVELS REMAIN SATURATED...INDICATIVE OF
TRAPPED STRATOCU AMID COLD AIR ADVECTION. FORECAST SOUNDINGS BEGIN
TO TAKE A TUMBLE ON SUNDAY AFTERNOON ALSO...AS THE SURFACE COLD
FRONT PUSHES SOUTHEAST OF THE OHIO VALLEY. BY 00Z MONDAY...THE
MAJORITY OF THE FORECAST SOUNDINGS ARE BELOW FREEZING AND DEEP
MOISTURE IS LOST AS SURFACE HIGH PRESSURE OVER THE PLAINS STATES
PROVIDES A COLD NORTHWEST FLOW OF COLD AIR AS 850MB TEMPS FALL
BACK TO NEAR 0C. MOISTURE ON SUNDAY AND SUNDAY NIGHT APPEARS
LIMITED AS PRECIPITABLE WATER IS REDUCED TO MORE NORMAL LEVELS AND
DRY AIR CONTINUES TO STREAM INTO THE COLUMN. HOWEVER WITH
LINGERING LOWER LEVEL MOISTURE AND BROAD CYCLONIC FLOW IN PLACE ON
SUNDAY AND SUNDAY NIGHT...CANNOT RULE OUT LIGHT PRECIPITATION
AMOUNTS. WILL STICK CLOSE TO GUIDANCE POPS AT THOSE TIMES. GIVEN
THE CHANGE IN AIR MASS WILL TREND COOLER THAN THE MAVMOS ON SUNDAY
HIGHS AND PROBABLY COOLER THAN MEXMOS LOWS ON SUNDAY NIGHT GIVEN
THE EXPECTED COLD AIR ADVECTION.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
ISSUED AT 205 PM EST THU DEC 19 2013
LONG TERM PERIOD WILL GENERALLY BE A QUIET ONE WITH STRONG HIGH
PRESSURE TRAVERSING THE REGION IN BETWEEN THE VERY TAIL END OF OUR
WEEKEND FRONTAL SYSTEM SUNDAY NIGHT...AND THE NEXT FRONTAL SYSTEM
WHICH LOOKS TO HOLD OFF UNTIL WEDNESDAY NIGHT INTO THURSDAY.
THUS...A DRY FORECAST WILL HOLD THROUGH MUCH OF THE PERIOD.
VERY LOW POPS EARLY IN THE PERIOD REASONABLE...AND ANY REMAINING
PRECIP SHOULD BE ALL SNOW BY THEN. ADDITIONALLY...LATE WEEK SYSTEM
SHOULD BE COLD ENOUGH TO BE ALL SNOW AS WELL. NOTHING SIGNIFICANT
APPEARING ON THE HORIZON JUST YET.
TEMPERATURES WERE INITIALIZED REASONABLY...WITH A BIT OF A ROLLER
COASTER RIDE THROUGH THE HOLIDAY WEEK. SEE LITTLE OPPORTUNITY FOR
IMPROVEMENT OVER A BLEND.
&&
.AVIATION /DISCUSSION FOR 200600Z TAF ISSUANCE/...
ISSUED AT 1142 PM EST THU DEC 19 2013
STEADILY DETERIORATING CONDITIONS FOR AVIATORS WITH LIFR
CONDITIONS DEVELOPING FOR MUCH OF FRIDAY.
FRONTAL BOUNDARY EXTENDING FROM SOUTHERN LOWER MICHIGAN W/SW INTO
NORTH CENTRAL ILLINOIS LATE THIS EVENING. STRENGTHENING LOW LEVEL
JET CONTINUES TO BRING GULF MOISTURE INTO THE OHIO VALLEY. RH
PROGS AT 950/925MB OFF THE RAP INDICATE SUBTLY DRIER AIR LIFTING
NORTH ACROSS CENTRAL INDIANA...AND THIS HAS LIKELY DELAYED
CEILINGS FROM FALLING BELOW VFR. AS DEEPER MOISTURE AND LIGHT RAIN
SHOWERS EXPAND INTO THE FORECAST AREA OVERNIGHT...EXPECT IFR
CEILINGS TO BECOME PREVALENT PRIOR TO DAYBREAK...DROPPING TO 500FT
OR LOWER AS THE INVERSION STRENGHTENS DURING THE MORNING.
RAIN WILL CONTINUE AS WELL THROUGH MUCH OF THE DAY AS A SURFACE
WAVE TRAVERSES THE NEARLY STATIONARY BOUNDARY JUST TO THE
NORTHWEST OF THE REGION. SLIGHTLY DRIER AIR ALOFT ATTEMPTS TO
BRIEFLY WORK INTO THE REGION BEHIND THE SURFACE WAVE LATE FRIDAY
AFTERNOON BUT WITH SATURATED CONDITIONS TRAPPED BENEATH THE
INVERSION...MAY ONLY SEE RAIN LIGHTEN TO DRIZZLE FOR A FEW HOURS.
MORE WIDESPREAD AND HEAVIER RAINFALL WILL QUICKLY EXPAND INTO
CENTRAL INDIANA NEAR THE END OF THE FORECAST PERIOD AS DEEPER
MOISTURE ADVECTS INTO THE OHIO VALLEY.
LOW LEVEL WIND SHEAR WILL REMAIN A FACTOR THROUGH THE FIRST 12
HOURS OF THE FORECAST WITH THE PRESENCE OF THE LOW LEVEL JET. RAP
INDICATING POTENTIAL FOR SOUTHWEST WINDS TO APPROACH 60KTS
OVERNIGHT IN THE 2-3KFT LAYER. LLWS CONCERNS WILL NOT DIMINISH
UNTIL EARLY AFTERNOON AS THE LOW LEVEL JET WEAKENS. SOUTHWEST
WINDS AT 10 TO 15 KTS ARE EXPECTED THROUGH MUCH OF THE PERIOD...
VEERING TO MORE OF A WESTERLY DIRECTION FRIDAY EVENING AS THE
BOUNDARY SAGS INTO THE FORECAST AREA.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH FROM LATE TONIGHT THROUGH SUNDAY MORNING FOR INZ021-
028>031-035>049-051>057-060>065-067>072.
&&
$$
SYNOPSIS...PUMA
NEAR TERM...PUMA
SHORT TERM...PUMA
LONG TERM...NIELD
AVIATION...RYAN
VISIT US AT HTTP://WWW.WEATHER.GOV/IND
FOLLOW US ON TWITTER AND YOUTUBE AT:
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AREA FORECAST DISCUSSION
NWS INDIANAPOLIS IN
1142 PM EST THU DEC 19 2013
.UPDATE...
THE AVIATION SECTION HAS BEEN UPDATED BELOW.
&&
.SYNOPSIS...
ISSUED AT 300 PM EST THU DEC 19 2013
A LOW PRESSURE TROUGH FROM TEXAS TO THE GREAT LAKES WILL WILL SETTLE
INTO THE OHIO VALLEY THIS WEEKEND. A COUPLE OF SHORT WAVES EMBEDDED
WITHIN THE TROUGH WILL PRODUCE SEVERAL SURGES OF RAINFALL WITH THE
INITIAL RAIN BEING LIGHT THROUGH FRIDAY EVENING. THE SECOND WAVE
WILL BRING SUBSTANTIAL RAIN SATURDAY BEFORE IT DEPARTS THE REGION
SUNDAY. COLD HIGH PRESSURE WILL BUILD INTO THE REGION TO START THE
WEEK. A WEAK LOW PRESSURE TROUGH WILL MOVE INTO THE GREAT LAKES AND
OHIO VALLEY NEXT THURSDAY AND MAY PRODUCE SOME LIGHT SNOW.
ABOVE NORMAL TEMPERATURES WILL PREVAIL INTO FRIDAY THEN RETURN TO
NORMAL AND THEN BELOW NORMAL BY SUNDAY NIGHT AND REMAIN BELOW NORMAL
MOST OF NEXT WEEK.
&&
.NEAR TERM /REST OF TONIGHT/...
ISSUED AT 928 PM EST THU DEC 19 2013
DECENT LIFT ONGOING ACROSS THE AREA THIS EVENING ALONG A 35-40 KT
LOW LEVEL JET...HOWEVER DEEPER MOISTURE FOR PRECIPITATION IS STILL
LACKING A BIT BASED ON THIS EVENING/S UPPER AIR. STILL APPEARS SOME
PRECIPITATION WILL DEVELOP LATER TONIGHT UNDER SUSTAINED WARM/MOIST
ADVECTION...BUT IT MAY HOLD OFF UNTIL THE EARLY MORNING HOURS ON
FRIDAY.
TEMPERATURES HAVE HELD NEARLY STEADY THIS EVENING...AND WITH WARM
ADVECTION CONTINUING TONIGHT...THINK IT WILL BE TOUGH FOR
TEMPERATURES TO REACH THE CURRENT FORECAST LOWS...ESPECIALLY OVER
THE SOUTH. WILL ALLOW FOR A SLIGHT FALL TO THE TEMPERATURES FOR THE
REST OF THE NIGHT.
PREVIOUS DISCUSSION FOLLOWS.
MODELS SIMILAR AND WILL USE A BLEND. FIRST UPPER WAVE AND ASSOCIATED
SURFACE LOW WILL LIFT NORTHEAST TO NEAR QUINCY BY FRIDAY MORNING.
INCREASING LIFT WILL CONTINUE MOISTENING ATMOSPHERE COLUMN AND BY
MIDNIGHT SHOULD BEGIN TO SPREAD VERY LIGHT RAIN ACROSS CENTRAL
INDIANA. MILD SOUTHWEST FLOW CONTINUING WILL RESULT IN MINIMUM
TEMPERATURES AT OR NEAR LAST NIGHTS VALUES OR IN THE UPPER 30S TO
LOWER 40S.
&&
.SHORT TERM /FRIDAY THROUGH SUNDAY/...
ISSUED AT 300 PM EST THU DEC 19 2013
ISSUE FOR THIS PERIOD IS WHERE THE HEAVY RAIN AXIS WILL END UP.
MODELS STILL VARY A BIT WITH DIFFERENCES IN SURFACE LOW TRACK
WHICH TIES TO HEAVY RAIN AXIS. WILL CONTINUE TO USE A BLEND OF
MODELS TO AVERAGE RAIN AMOUNTS ACROSS THE FORECAST AREA AND
INCLUDE HPC EXCESSIVE RAINFALL GUIDANCE AS WELL AS RIVER FORECAST
CENTER QUANTITATIVE PRECIPITATION FORECASTS AS PART OF BLEND.
FRIDAY AND FRIDAY NIGHT...
DURING THIS TIME FRAME ALL MODELS LIFT THE INITIAL SURFACE LOW FROM
THE MID MISSISSIPPI VALLEY FRIDAY MORNING TO THE NEW ENGLAND
SATURDAY MORNING. THIS WAVE WILL PRODUCE PERIODS OF LIGHT RAIN AND
WILL SETTLE A COLD FRONT SURFACE BOUNDARY TO A POSITION NEAR THE
OHIO RIVER. ON SOUTHWEST WINDS...TEMPERATURES SURGE INTO THE 50S FOR
MOST AREAS FRIDAY THEN SETTLE BACK INTO THE MID 30S NORTH TO MID 40S
SOUTH BY DAYBREAK SATURDAY.
SATURDAY INTO SUNDAY MORNING...
MODELS DIFFER SOME ON TRACK OF THE MAIN WAVE AND SURFACE LOW LIFTING
INTO THE REGION SO WILL AGAIN CONTINUE A BLEND BUT LEAN TOWARDS A
TRACK UP INTO AND ACROSS OUR SOUTHERN COUNTIES.
ALL MODELS SHOW A STRONG THERMAL BOUNDARY AND STRONG JET DYNAMICS
YIELDING SUBSTANTIAL LIFT OF UNUSUALLY MOIST AIR ORIGINATING IN LOW
LATITUDES BASED ON WATER VAPOR IMAGES...RESULTING IN SUBSTANTIAL AND
PROLONGED RAINS FROM SATURDAY MORNING INTO SUNDAY MORNING. AXIS OF
HEAVIEST PRECIPITATION WILL BE PLACED NEAR BUT JUST SOUTH HPC
PRECIPITATION GUIDANCE IN LINE WITH RIVER FORECAST CENTER. RAIN
AMOUNTS FROM 2 INCHES NORTH TO 4 INCHES SOUTH STILL APPEAR LIKELY
DURING THIS 24 HOUR PERIOD. AGAIN MODEL DIFFERENCES SUGGEST A TRACK
FURTHER NORTH THAN THIS PUSHES HEAVY RAIN AXIS ALONG AND NORTH OF
I-70 AND ALSO BRINGS MILDER TEMPERATURES SATURDAY NIGHT AND SUNDAY
CLOSER TO I-70. DRY SLOT WRAPS IN AFTER MIDNIGHT SATURDAY NIGHT WILL
BRING AND END TO HEAVIEST RAIN.
SUNDAY...
DRY SLOT STILL IN PLAY SUNDAY AS COLD FRONT SWEEPS COLDER AIR IN
BEGINNING SUNDAY MORNING. WRAP AROUND CLOUD SHIELD WILL MOVE INTO
CENTRAL INDIANA SUNDAY AFTERNOON AND BRING A MIX OF LIGHTER RAIN
SHOWERS AND SNOW SHOWERS THAT TRANSITION INTO ALL SNOW SHOWERS
BEFORE NIGHTFALL. NO SNOW ACCUMULATION IS EXPECTED.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
ISSUED AT 205 PM EST THU DEC 19 2013
LONG TERM PERIOD WILL GENERALLY BE A QUIET ONE WITH STRONG HIGH
PRESSURE TRAVERSING THE REGION IN BETWEEN THE VERY TAIL END OF OUR
WEEKEND FRONTAL SYSTEM SUNDAY NIGHT...AND THE NEXT FRONTAL SYSTEM
WHICH LOOKS TO HOLD OFF UNTIL WEDNESDAY NIGHT INTO THURSDAY.
THUS...A DRY FORECAST WILL HOLD THROUGH MUCH OF THE PERIOD.
VERY LOW POPS EARLY IN THE PERIOD REASONABLE...AND ANY REMAINING
PRECIP SHOULD BE ALL SNOW BY THEN. ADDITIONALLY...LATE WEEK SYSTEM
SHOULD BE COLD ENOUGH TO BE ALL SNOW AS WELL. NOTHING SIGNIFICANT
APPEARING ON THE HORIZON JUST YET.
TEMPERATURES WERE INITIALIZED REASONABLY...WITH A BIT OF A ROLLER
COASTER RIDE THROUGH THE HOLIDAY WEEK. SEE LITTLE OPPORTUNITY FOR
IMPROVEMENT OVER A BLEND.
&&
.AVIATION /DISCUSSION FOR 200600Z TAF ISSUANCE/...
ISSUED AT 1142 PM EST THU DEC 19 2013
STEADILY DETERIORATING CONDITIONS FOR AVIATORS WITH LIFR
CONDITIONS DEVELOPING FOR MUCH OF FRIDAY.
FRONTAL BOUNDARY EXTENDING FROM SOUTHERN LOWER MICHIGAN W/SW INTO
NORTH CENTRAL ILLINOIS LATE THIS EVENING. STRENGTHENING LOW LEVEL
JET CONTINUES TO BRING GULF MOISTURE INTO THE OHIO VALLEY. RH
PROGS AT 950/925MB OFF THE RAP INDICATE SUBTLY DRIER AIR LIFTING
NORTH ACROSS CENTRAL INDIANA...AND THIS HAS LIKELY DELAYED
CEILINGS FROM FALLING BELOW VFR. AS DEEPER MOISTURE AND LIGHT RAIN
SHOWERS EXPAND INTO THE FORECAST AREA OVERNIGHT...EXPECT IFR
CEILINGS TO BECOME PREVALENT PRIOR TO DAYBREAK...DROPPING TO 500FT
OR LOWER AS THE INVERSION STRENGHTENS DURING THE MORNING.
RAIN WILL CONTINUE AS WELL THROUGH MUCH OF THE DAY AS A SURFACE
WAVE TRAVERSES THE NEARLY STATIONARY BOUNDARY JUST TO THE
NORTHWEST OF THE REGION. SLIGHTLY DRIER AIR ALOFT ATTEMPTS TO
BRIEFLY WORK INTO THE REGION BEHIND THE SURFACE WAVE LATE FRIDAY
AFTERNOON BUT WITH SATURATED CONDITIONS TRAPPED BENEATH THE
INVERSION...MAY ONLY SEE RAIN LIGHTEN TO DRIZZLE FOR A FEW HOURS.
MORE WIDESPREAD AND HEAVIER RAINFALL WILL QUICKLY EXPAND INTO
CENTRAL INDIANA NEAR THE END OF THE FORECAST PERIOD AS DEEPER
MOISTURE ADVECTS INTO THE OHIO VALLEY.
LOW LEVEL WIND SHEAR WILL REMAIN A FACTOR THROUGH THE FIRST 12
HOURS OF THE FORECAST WITH THE PRESENCE OF THE LOW LEVEL JET. RAP
INDICATING POTENTIAL FOR SOUTHWEST WINDS TO APPROACH 60KTS
OVERNIGHT IN THE 2-3KFT LAYER. LLWS CONCERNS WILL NOT DIMINISH
UNTIL EARLY AFTERNOON AS THE LOW LEVEL JET WEAKENS. SOUTHWEST
WINDS AT 10 TO 15 KTS ARE EXPECTED THROUGH MUCH OF THE PERIOD...
VEERING TO MORE OF A WESTERLY DIRECTION FRIDAY EVENING AS THE
BOUNDARY SAGS INTO THE FORECAST AREA.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH FROM LATE FRIDAY NIGHT THROUGH SUNDAY MORNING FOR
INZ021-028>031-035>049-051>057-060>065-067>072.
&&
$$
SYNOPSIS...TUCEK
NEAR TERM...TUCEK/JAS
SHORT TERM...TUCEK
LONG TERM...NIELD
AVIATION...RYAN
VISIT US AT HTTP://WWW.WEATHER.GOV/IND
FOLLOW US ON TWITTER AND YOUTUBE AT:
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AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1130 PM CST THU DEC 19 2013
.UPDATE...
ISSUED AT 802 PM CST THU DEC 19 2013
BASED ON CURRENT TRENDS...HAVE MOVED UP THE ONSET OF THE FREEZING
RAIN ADVISORY FOR THE EASTERN SEGMENT THAT WAS PREVIOUSLY SET TO
BEGIN AT MIDNIGHT...TO 10 PM. ALSO...ADDED FAR NORTHWEST ILLINOIS
COUNTIES TO THE CURRENT ADVISORY AREA.
AT 745 PM...KDVN RADAR SHOWED WIDESPREAD LIGHT RAIN ACROSS THE CENTRAL
AND NORTHERN PORTIONS OF THE FORECAST AREA WITH WIDESPREAD
DRIZZLE THE ENTIRE AREA NORTH OF HIGHWAY 34. THE FREEZING LINE AT
THE SURFACE WAS ROUGHLY ALONG A LINE FROM WESTERN STEPHENSON COUNTY
IL...TO CEDAR RAPIDS AND SOUTHWEST TO NEAR PELLA. SURFACE
OBSERVATIONS WERE INDEED REPORTING FREEZING RAIN NW OF THIS LINE.
USED RAP MODEL TRENDS TO TRANSITION THE 32 DEGREE LINE AND
FREEZING PRECIP AREA SOUTHEAST THIS EVENING AND OVERNIGHT.
THE PRECIPITATION SHOULD CONTINUE UNTIL THE WAVE OF LOW PRESSURE
STILL OUT OVER THE OK PANHANDLE PASSES TO OUR SOUTHEAST THROUGH
CENTRAL IL FRIDAY AFTERNOON. WITH THIS TIMING...THE PRECIPITATION
SHOULD CONTINUE THROUGH MOST OF FRIDAY MORNING...WHEN LOW LEVEL
COLD ADVECTION SHOULD CHANGE THE PRECIPITATION OVER TO LIGHT SNOW
AND POSSIBLY SLEET ACROSS THE NORTHWEST.
&&
.SYNOPSIS...
ISSUED AT 330 PM CST THU DEC 19 2013
A FRONTAL BOUNDARY REMAINS DRAPED ACROSS THE AREA THIS AFTERNOON...
ROUGHLY ALONG INTERSTATE 80. MOISTURE IS POOLING ALONG AND SOUTH
OF THE FRONT...EVIDENT BY DEW POINTS THAT HAVE CLIMBED INTO THE
30S AND EVEN LOWER 40S. TO THE NORTH...DEW POINTS ARE IN THE MID
AND UPPER 20S. FOG NEVER DID FORM TODAY...WITH VISIBILITIES GENERALLY
REMAINING OVER 6 MILES...WITH ONLY A FEW SITES DROPPING TO 4-6SM
FOR ONLY AN HOUR OR TWO. HIGH LEVEL CLOUDS BLANKET THE AREA...WITH
SOME LOW LEVEL STRATUS JUST NOW OVER THE PAST HOUR/TWO FORMING
OVER AREAS SOUTH OF I 80. AS OF 3 PM...TEMPERATURES RANGE FROM THE
LOWER 30S ALONG HIGHWAY 20...TO THE UPPER 40S AND LOWER 50S IN
NORTHEAST MO.
&&
.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 330 PM CST THU DEC 19 2013
GENERAL SHORT TERM FORECAST HAS NOT CHANGED MUCH...OTHER THAN
WITH ABOUT A 6 HOUR DELAY. STILL EXPECT LIGHT RAIN AND FREEZING
RAIN TO DEVELOP ACROSS THE AREA THIS EVENING AND ESPECIALLY
OVERNIGHT. NO CHANGE TO GOING FREEZING RAIN ADVISORY AREAL
COVERAGE...HOWEVER WE HAVE EXTENDED IT UNTIL MID MORNING FRIDAY.
DO NOT EXPECT THAT MUCH RAINFALL WITH THIS EVENT...WITH MOST AREAS
SEEING A FEW HUNDREDTHS OF AN INCH TO UNDER A TENTH. MINOR ICE
ACCUMULATIONS OR A LIGHT GLAZE WILL STILL BE POSSIBLE ON UNTREATED
SURFACES LATE TONIGHT THROUGH THE MORNING COMMUTE FRIDAY FOR AREAS
IN THE ADVISORY. SEE THE LATEST WINTER WEATHER MESSAGE FOR MORE
INFORMATION. LOWS TONIGHT WILL RANGE FROM AROUND 20 IN THE NW
CWFA...TO THE MID 30S IN PARTS OF WEST CENTRAL IL.
ONLY A SLIGHT RISE IN TEMPS IS EXPECTED FRIDAY...AS THE WINTRY
MIX OF -RA/-FZRA/-SN SLOWLY EXITS TO THE EAST AND NORTH WINDS
USHER COLD AIR INTO THE AREA. THE NW 1/3 OF THE AREA MAY SEE THE
PCPN CHANGE TO ALL SNOW BEFORE ENDING DURING THE DAY FRIDAY WITH
ONLY A DUSTING OF ACCUMULATION POSSIBLE.
.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 330 PM CST THU DEC 19 2013
A WINTER STORM WILL IMPACT THE CWA SATURDAY NIGHT AND SUNDAY. FOR
THIS POTENTIAL...WHICH IS COMPLICATED IN MANY WAYS...A WINTER
STORM WATCH HAS BEEN ISSUED FOR ALL COUNTIES FROM 00Z SUN TO 00Z
MONDAY.
UPPER AIR OBSERVATIONS CONFIRM A STRONG UPPER LOW IS DIGGING
SOUTHEAST THROUGH CALIFORNIA TODAY...AND WILL BE KICKED OUT OF THE
BASE OF THE TROF BY A STRONG 150KT JET STREAK OBSERVED AT 300MB.
THIS WILL SET THE STAGE FOR CYCLOGENESIS ALONG THE FRONTAL BOUNDARY
WHICH WILL BE STALLED TO OUR SOUTH FRIDAY NIGHT. GUIDANCE IS IN
FAIRLY GOOD AGREEMENT THAT THE SURFACE LOW WILL PASS FROM NEAR
SOUTHWEST MO SATURDAY AFTERNOON...TO NORTHERN INDIANA BY SUNDAY
MORNING. THE UPPER LOW SHOULD EJECT NORTHEAST...WITH MODELS AGREEING
A TRACK THROUGH THE CWA AS A PARTIALLY CLOSED OFF 500MB LOW OCCURRING
ABOUT 12Z SUNDAY. THIS SYNOPTICALLY SETS THE STAGE FOR A SIGNIFICANT
WINTER STORM FOR OUR CWA AND MUCH OF THE MIDWEST. HEAVY RAINS WILL
TAKE PLACE A BIT FARTHER SOUTHEAST...FROM FRIDAY THROUGH SUNDAY.
THERMALLY...MODELS ARE A BIT COLDER THAN LAST NIGHTS RUNS...AND I
HAVE ADJUSTED THE SLEET/ZR TRANSITION TO SNOW A BIT FARTHER EAST.
HOWEVER...IT MAY BE SEEN THAT A SIGNIFICANT AMOUNT OF QPF FOR THIS
EVENT FALLS AS SLEET AND POSSIBLE RA/ZR IN THE SOUTHEAST AND FAR
EAST. WEST OF A LINE FROM BURLINGTON TO STERLING ILLINOIS...THIS
EVENT SHOULD BE DOMINATED BY SNOW SATURDAY NIGHT AND SUNDAY.
THUS...AMOUNTS WILL SEE A STEEP GRADIENT FROM 6-8 INCHES WIDESPREAD
IN THE IOWA AND FAR WESTERN IL COUNTIES...TO UNDER 4 INCHES IN THE
EAST. THOUGH AMOUNTS SHOULD BE UNDER 6 INCHES IN THE EAST AND
SOUTHEAST...IT DOES APPEAR THAT SLEET AND FREEZING RAIN MAY BE
ENOUGH OF A THREAT TO WARRANT A WATCH INCLUSION. BLOWING SNOW IN
OPEN AREAS...AND WIDESPREAD SIGNIFICANT DRIFTING SHOULD CONTINUE
THROUGH SUNDAY AFTERNOON...AND THE WATCH WILL BE CONTINUED THROUGH
6PM FOR THIS REASON.
BEYOND THIS...TEMPERATURES CONTINUE TO BE COOLED IN THIS GUIDANCE
BLEND FORECAST OF THE EXTENDED. WE WILL CERTAINLY KEEP WHAT SNOW
COVER IS ON THE GROUND SUNDAY AFTERNOON THROUGH DECEMBER 25. YOU
GUESSED IT...ITS GOING TO BE A WHITE CHRISTMAS IN MUCH OF THE UPPER
MIDWEST.
ERVIN
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1129 PM CST THU DEC 19 2013
A WAVE OF LOW PRESSURE MOVING ALONG A SLOW MOVING COLD FRONT WILL
CONTINUE TO RESULT IN LIGHT FREEZING RAIN AND DRIZZLE OVER THE
REGION OVERNIGHT INTO EARLY FRIDAY. LATE THURSDAY EVENING...
PRECIPITATION WAS FREEZING ON PAVED SURFACES AT CID AND
DBQ...WHILE MLI AND BRL REMAINED JUST ENOUGH ABOVE FREEZING
RESULTING IN LIQUID PRECIPITATION. THIS FREEZING LINE WILL
GRADUALLY MOVE SOUTHEAST TOWARD MORNING...POSSIBLY RESULTING IN A
LIGHT GLAZING ON RUNWAYS AT MLI FRIDAY MORNING. OTHERWISE...DEEP
LOW LEVEL MOISTURE WILL LINGER KEEPING WIDESPREAD IFR AND LIFR
CONDITIONS DUE TO LOW CLOUDS AND FOG IN PLACE TONIGHT THROUGH MUCH
OF FRIDAY. WHILE THE PRECIPITATION IS EXPECTED TO END FRIDAY
AFTERNOON...CIGS ARE EXPECTED TO REMAIN BELOW 1000 FT WELL INTO
FRIDAY EVENING.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR BENTON-BUCHANAN-
CEDAR-CLINTON-DELAWARE-DES MOINES-DUBUQUE-HENRY IA-IOWA-
JACKSON-JEFFERSON-JOHNSON-JONES-KEOKUK-LINN-LOUISA-
MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR BENTON-BUCHANAN-CEDAR-CLINTON-DELAWARE-DES
MOINES-DUBUQUE-HENRY IA-IOWA-JACKSON-JEFFERSON-JOHNSON-
JONES-KEOKUK-LEE-LINN-LOUISA-MUSCATINE-SCOTT-VAN BUREN-
WASHINGTON.
IL...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR CARROLL-JO
DAVIESS-MERCER-ROCK ISLAND-STEPHENSON-WHITESIDE.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR BUREAU-CARROLL-HANCOCK-HENDERSON-HENRY IL-JO
DAVIESS-MCDONOUGH-MERCER-PUTNAM-ROCK ISLAND-STEPHENSON-
WARREN-WHITESIDE.
MO...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR SCOTLAND.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR CLARK-SCOTLAND.
&&
$$
UPDATE...SHEETS
SYNOPSIS...14
SHORT TERM...14
LONG TERM...ERVIN
AVIATION...SHEETS
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
357 AM CST Fri Dec 20 2013
...Updated for synopsis and short term discussion...
.SYNOPSIS...
ISSUED AT 340 AM CST FRI DEC 20 2013
An upper level trough was progressing southeastward into
northwestern Mexico and the southern Rockies early this morning
while a wedge of arctic air surged southward into the central
plains. Stratus covered western Kansas in the wake of the front,
with ceilings from 1000-2000 ft. Mid to high level winds were
generally out of the west-southwest over the central and southern
plains ahead of the southwestern system.
&&
.SHORT TERM...(Today and tonight)
ISSUED AT 340 AM CST FRI DEC 20 2013
The approaching winter weather will be covered in the long
term discussion since the vast majority of winter weather
is expected after 12z Saturday.
Cold high pressure will be centered over Nebraska and South Dakota
today, but the southern periphery of the high will be wedged into
southwestern Kansas. It is a tough call as to whether the low stratus
clouds will clear out, allowing temperatures to modify a little
today. The NAM and SREF indicate clearing with highs around 33F at
Dodge City, 30F at Hays and 36 at Elkhart, while the RAP holds
onto the stratus for areas east of Garden City, with much cooler
highs in upper teens to lower and mid 20s. Opted to go with an in
between solution due to the uncertainty, with mid to high 20s at
Hays, Dodge City and Pratt, and lower 30s in far southwestern and
Western Kansas. Some mid to high level cloud will be increasing
late today in advance of the aforementioned upper level trough. By
tonight, mid level cloud will continue to increase over southwestern
Kansas, with only limited radiational cooling in the brief clear
breaks. Temperatures should bottom out in the upper teens to lower
20s, but could be lower if temperatures stay colder today.
.LONG TERM...(Saturday through Thursday)
ISSUED AT 254 AM CST FRI DEC 20 2013
Models this morning remain in good agreement with an upper level
trough/low lifting northeast from west central Texas into western
Oklahoma on Saturday. Widespread steady precipitation is expected
by the early Saturday morning across southwest and south central
Kansas given the moisture, warm air advection, and improving
frontogenesis ahead of the approaching upper level system. The
warm air advection early Saturday will result in a wintry mix
early Saturday, however the NAM, GFS, and ECMWF still disagree
with the magnitude of warm layer aloft. At this time confidence is
low on which model may be more correct so have decided to lean
towards a compromise between the warmer GFS and the cooler NAM and
ECMWF. Based on this as a first guess and applying the top down
approach it still appears that there will be an extended period of
sleet and freezing rain across much of south central Kansas early
Saturday morning. The area more favorable for ice accumulations
currently appears to be southeast of a Stafford to Greensburg to
Ashland line. Further northwest a brief period of freezing
precipitation will be possible early Saturday, however this should
quickly change over to snow during the early morning hours.
By Saturday afternoon the atmosphere will cool enough for mainly
snow and an area of 850-700mb frontogenesis will begin to improve
across southwest Kansas. The 00z Friday model runs continue to
indicated some discrepancies with where this area of forcing will
develop, however they all agree that as frontogenesis improves the
snow will become steadier and heavier at times Saturday afternoon
and early Saturday night. Both the GFS and ECMWF continues to
highlight this area of frontogenesis will be developing near a
line from roughly Hugoton to near Dodge City to around LaCrosse.
00z NAM was further southeast. At this time given the agreement
between the GFS and ECMWF and the run to run consistency on
location of this frontogenesis have decided to stay close to the
00z GFS/ECMWF. The steadiest and heaviest snowfall appears to
occur from 18z to 06z as the forcing along the mid level
baroclinic zone strengths and remains nearly stationary. After 06z
this baroclinic zone will begin to slide east towards central
Kansas as the upper trough moves across southeast Kansas and into
Missouri. Snow accumulations of 2 to near 6 inches still appears
reasonable. Locally higher accumulations are not out of the
question from Dodge City northeast where the snow is expected to
begin sooner and the mid level forcing appears to last slightly
longer. Given that there still is some uncertainty on location and
snowfall amounts late Saturday and Saturday night have decided to
continue with the Winter Storm Watch and not upgrade to a warning
or advisory just yet.
On Sunday a weaker upper level disturbance will cross western
Kansas. Although snow is not anticipated with this next weaker
system, increasing clouds may aid in keeping temperatures down
Sunday afternoon. Based on possible cloud cover and expected
snowfall on Sunday will continue to favor the cooler MAV/MOSGUIDE
for highs given expected snow cover.
On Sunday night an area of high pressure at the surface will
start to build into Kansas from the north. As the surface ridge
axis moves into portions of western Kansas the winds will become
light and variable. Light winds and snow cover will provided
favorable conditions for temperatures to fall back to near zero
given a period of clear skies. At this time however am somewhat
concerned about some increasing clouds after midnight. As a result
will trim temperatures back into the single digits which are
cooler latest guidance.
A gradual warming trend will then begin to develop early next
week as a northwest flow backs and becomes more perpendicular to
the Rockies. How quickly temperatures will rebound early next week
is still somewhat unclear, but the latest temperature trend
currently in the forecast still appears to be on track. A cold
front crossing western Kansas mid week will end this warming trend
briefly.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 1159 PM CST THU DEC 19 2013
IFR/MVFR CIGS will persist in the wake of an arctic front through
18z and then gradually clear between 21 and 02z. Winds will
gradaually become light east to southeasterly after 21z as surface
pressures fall in the lee of the Rockies.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 27 20 26 19 / 10 50 80 80
GCK 28 19 27 19 / 10 30 70 70
EHA 32 21 30 22 / 10 40 70 60
LBL 30 20 28 21 / 10 50 80 80
HYS 26 19 28 17 / 0 20 70 70
P28 29 23 28 21 / 10 70 80 80
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH from late tonight through late Saturday night
FOR KSZ064>066-076>081-085>090.
&&
$$
SYNOPSIS...Finch
SHORT TERM...Finch
LONG TERM...Burgert
AVIATION...Finch
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
400 AM CST FRI DEC 20 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CST FRI DEC 20 2013
SNOW BEGINNING TO TAPER OFF ACROSS THE AREA THIS MORNING AS WEAK
ISENTROPIC UPGLIDE WE HAD IS SLOWLY FADING AWAY. BEST EVIDENCE OF
THE LOSS OF LIFT WAS THE CONSIDERABLE AMOUNT OF WARMING WE SAW WITH
CLOUD TOP TEMPS BETWEEN 5Z AND 7Z...IR WARMING THESE TWO HOURS
MATCHED UP WELL WITH THE LOSS OF SNOW OBSERVATIONS. THERE WILL BE
ONE MORE POTENTIAL SNOW BAND TO WATCH OUT FOR THIS MORNING FROM
SOUTH CENTRAL MN TOWARD THE EAU CLAIRE AREA. LOOKING BACK OVER THE
ERN NEB/SODAK BORDER...THERE HAS BEEN A BAND OF COOLING CLOUD TOPS
THE LAST COUPLE OF HOURS...WHICH IS ASSOCIATED A SECTION OF THE
H7-H6 FGEN THAT THE RAP SHOWS BECOMING ACTIVE ONCE AGAIN. THIS IS
BEING AIDED BY A SLIGHT LOWERING OF THE TROPOPAUSE LEVEL THAT
EMANATED FROM THE PRIMARY UPPER TROUGH OVER THE ROCKIES LAST NIGHT.
THIS BAND OF FGEN WILL SLIDE EAST THROUGH THE MORNING AND MOST
HI-RES MODELS...ALONG WITH THE 20.00/20.06 NAM12 SHOW ONE LAST BAND
OF SNOW CUTTING ACROSS OR NEAR THE SE CORNER OF THE MPX CWA BETWEEN
ABOUT 14Z AND 18Z.
THE BIGGER QUESTION FOR TODAY THOUGH IS WHAT WILL HAPPEN WITH THE
CLOUD COVER. SEEING SOME CONFLICTING TRENDS WITH THE CLOUD COVER
EARLY THIS MORNING...WHICH IS HELPING MAKE THE CLOUD FORECAST RATHER
DIFFICULT. A VERY DRY HIGH PRESSURE OF CONTINENTAL POLAR ORIGIN IS
CURRENTLY CENTERED FROM CENTRAL SODAK INTO NORTH CENTRAL MN. WITHIN
THIS HIGH WE ARE SEEING CLOUD HEIGHTS INCREASE OR EVEN CLEAR OUT
ACROSS CENTRAL MN...BUT BENEATH THE RIDGE OVER SODAK...THEY HAVE
BEEN EXPANDING THE LAST FEW HOURS. OVER SRN MN...THE CLOUDS HAVE
FINALLY BEGUN TO LOWER AS SLIGHTLY MORE MOIST AIR HAS BEEN PUSHED
NORTH OF THE STALLED OUT BOUNDARY THAT SITS FROM NE OKLAHOMA INTO
SRN MICH. THE MODELS SHOW PLENTY OF LOW LEVEL MOISTURE HANGING
AROUND THROUGH THE DAY...INDICATING A MOSTLY CLOUDY DAY IS IN
STORE...BUT SUSPECT THAT DRIER AIR OVER NRN MN WILL HELP KEEP THE
CLOUDS THINNER ACROSS NRN PORTIONS OF THE AREA. THE NAM/GFS SHOW
EVEN THE LOW LEVEL MOISTURE STARTING TO EVACUATE WRN MN
TONIGHT...WITH MOSTLY CLEAR SKIES WORKING INTO THE WEST LATE. IF
THIS HAPPENS...WE WILL PROBABLY HAVE TO TREND LOWS TONIGHT IN THE
WEST CLOSER TO THE COOL END OF GUIDANCE...WHICH SHOWS LOWS DROPPING
BACK DOWN INTO THE TEENS BELOW ZERO IN THE WEST AS IS SEEN WITH
GEM/ECMWF/NAM.
AS FOR THE MOISTURE AHEAD OF THE BOUNDARY TO OUR SOUTHEAST...IT IS
QUITE IMPRESSIVE. LOW LEVEL AIR TRAJECTORIES SHOW THAT THE AIR IN
THE WARM SECTOR OF THE SYSTEM TO OUR SOUTH CAN BE TRACED BACK TO NOT
JUST THE GULF OF MEXICO...BUT CLEAR DOWN INTO THE NRN CARIBBEAN AND
BACK EAST ACROSS CUBA INTO THE TROPICAL WRN ATLANTIC...HENCE WHY
HISTORIC RAINFALLS ARE EXPECTED IN THE COMING DAYS ACROSS THE OHIO
VALLEY.
.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 400 AM CST FRI DEC 20 2013
THE ARCTIC FRONT WILL OSCILLATE BACK AND FORTH ACROSS THE FORECAST
AREA DURING THE LONGER TERM. THIS WILL OFFER AT LEAST TWO SNOW
EVENTS AS WAVES OF LOW PRESSURE MOVE THROUGH FROM SUNDAY INTO
MONDAY AND THEN FROM TUESDAY INTO WEDNESDAY. SNOW ACCUMULATIONS OF AN
INCH OR TWO ARE POSSIBLE WITH EACH EVENT. FAIRLY STRONG HIGH
PRESSURE WILL FOLLOW EACH OF THESE WAVES. MONDAY MORNING STILL
LOOKS THE COLDEST WITH LOWS FROM NEAR 20 BELOW IN WEST CENTRAL MN
TO AROUND ZERO AT KEAU. COUPLE THIS WITH NORTHWEST WINDS NEAR 10
MPH AND WIND CHILL READINGS COME OUT TO AROUND 35 BELOW ZERO
ACROSS THE WESTERN CWA. HIGHS ON MONDAY WILL LIKELY STAY BELOW
ZERO ACROSS THE WEST WITH SINGLE DIGITS ABOVE ZERO FOR THE TWIN
CITIES AND WEST CENTRAL WI. A NON-DIURNAL TEMPERATURE TREND WAS
THEN INSERTED FOR MONDAY NIGHT ACROSS WEST CENTRAL AND SOUTHWEST
MN AS SOUTHERLY FLOW INCREASES ON THE BACK SIDE OF THE HIGH AS THE
NEXT WAVE OF LOW PRESSURE MOVES INTO THE DAKOTAS. CENTRAL AREAS OF
MN AND WEST CENTRAL WI WILL STILL HAVE A VERY COLD NIGHT WITH LOWS
MONDAY NIGHT FROM 10 BELOW TO 15 BELOW ZERO. THE WAVE OF LOW
PRESSURE ARRIVING ON TUESDAY POSES SOME PRECIP TYPE PROBLEMS FOR
SOUTHWEST MN WITH THE GFS INDICATING SOME POTENTIAL FOR FREEZING
DRIZZLE/FREEZING RAIN. THE ECMWF IS NOT AS AGGRESSIVE WITH THE LOW
LEVEL WARMING...PARTLY BECAUSE THE WHOLE UPPER WAVE IS FARTHER
SOUTH COMPARED TO THE GFS. THE ECMWF HAS DEEPER SATURATION AS
WELL. POPS FOR THE TUESDAY AND WEDNESDAY PERIOD WILL LIKELY NEED
TO BE ADJUSTED UPWARD IF THE POSITION OF THE GFS GETS CLOSER TO
THE ECMWF. POPS WERE EXPANDED AND ADJUSTED UPWARD FOR THE WAVE
FROM SUNDAY INTO MONDAY AS THE NORTHERN STREAM HAS BECOME
STRONGER. THE OTHER PROBLEM ON SUNDAY TO KEEP AN EYE ON IS THE
BLOWING SNOW FROM WEST CENTRAL INTO SOUTH CENTRAL MN. WITH MORE
WIDESPREAD SNOW FORECAST ALONG WITH INCREASING NORTHWEST WINDS AS
THE NEXT SURGE OF ARCTIC PUSHES IN...SOME PRETTY POOR VISIBILITIES
MAY RESULT ACROSS THE MN RIVER VALLEY DURING THE AFTERNOON AND NIGHT.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1026 PM CST THU DEC 19 2013
LITTLE CHANGE TO PREVIOUS THINKING...AT LEAST EARLY ON. BANDING ON
RADAR SHOULD CONTINUE TO TREND SOUTHEAST AS UPPER TROUGH SHEARS TO
THE EAST. WILL CONTINUE SNOW OVER THE EAST OVERNIGHT AND END
AROUND 12Z AS FORCING MOVES OFF. WILL END SNOW FROM NORTHWEST
THROUGH 08Z AS WELL. THEN FOCUS TURNS TO REMAINING CEILING OVER
THE AREA. APPEARS IFR CEILINGS WILL BE GENERATED OVER PARTS OF
CENTRAL CWA WHERE BEST SATURATION OCCURRED. QUESTION REMAINS IF
THIS DEVELOPS FURTHER TO THE SOUTHEAST OVERNIGHT INTO FRIDAY
MORNING. LOW CONFIDENCE ON MVFR CEILING FORECAST OVER THE AREA
INTO FRIDAY. THE SREF MVFR CIG PROBABILITIES REMAIN HIGH THROUGH
THE DAY ESPECIALLY OVER THE EASTERN CWA...AHEAD OF SURFACE RIDGE.
WILL HOLD ONTO THE MVFR CIGS THROUGH THE PERIOD...SIMILAR TO LAMP
GUIDANCE TREND FOR NOW. SURFACE WINDS WILL GRADUALLY TURN MORE
NORTHERLY INTO FRIDAY AND SLACKEN WITH THE APPROACH OF THE SURFACE
HIGH.
KMSP...
BANDED PRECIPITATION PATTERN DIFFICULT TO FORECAST. MODELS
SUGGEST DRYING TREND CONTINUING OVER THE SOUTHERN METRO OVERNIGHT.
STILL BELIEVE WHATEVER SNOW BAND REMAINS OVER THE CENTRAL CWA WILL
WORK SOUTHEAST AND WEAKEN THE REMINDER OF THE NIGHT. SO BELIEVE
MORE SNOW TO WORK ACROSS THE AIRPORT OVERNIGHT. WILL TRAIL IT OFF
AFTER 12Z BUT RETAIN THE MVFR CIGS DURING THE DAY. STILL A QUESTION
OF THESE WILL CLEAR THROUGH THE DAY...SO HELP ONTO THEM FOR NOW. NORTHEAST
TO NORTH WINDS THIS MORNING...WILL GRADUALLY DIMINISH INTO FRIDAY
AS SURFACE RIDGE BUILDS EAST.
/OUTLOOK FOR KMSP/
FRI EVENING...MVFR CIGS PSBL. WNDS LIGHT NW.
SAT...VFR. WNDS SE 5 KTS...BECOMING NW.
SUN...VFR. POSSIBLE MVFR CIGS/VSBYS -SN. WNDS WNW 15-20 KT G25-30KT.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
SHORT TERM...MPG
LONG TERM...RAH
AVIATION...DWE
AREA FORECAST DISCUSSION
NWS RALEIGH NC
111 AM EST FRI DEC 20 2013
.SYNOPSIS...SOUTH SOUTHWEST FLOW AROUND BERMUDA HIGH PRESSURE WILL
RESULT IN WARMING CONDITIONS THROUGH SUNDAY...FOLLOWED BY THE
PASSAGE OF A COLD FRONT SUNDAY NIGHT AND MONDAY.
&&
.NEAR TERM /TONIGHT/...
AS OF 940 PM THURSDAY...
THE SURFACE HIGH IS NOW WELL OFF OF THE NC COAST THIS EVENING...WITH
A LIGHT SOUTH-SOUTHWESTERLY WIND AT MOST OBSERVING SITES.
ALOFT...CIRRUS CONTINUES TO SPREAD EAST ACROSS THE REGION...THOUGH
THERE IS CURRENTLY A PATCH OF CLEARING ACROSS THE SOUTHERN PIEDMONT.
THE CIRRUS IS MAKING THE LOW TEMP FORECAST A LITTLE TRICKY..WITH
HIGHLY VARIABLE OBSERVED TEMPS RANGING FROM THE UPPER 30S TO LOWER
50S. WITH MORE CIRRUS IMMEDIATELY UPSTREAM OVER THE TN
VALLEY...TEMPS SHOULD BE VERY SLOW TO FALL FOR THE REMAINDER OF THE
NIGHT. MOST GUIDANCE SEEMS TOO LOW OVERALL BASED ON CURRENT
TRENDS...SO HAVE MADE SOME ADJUSTMENTS TO TRY TO CAPTURE WARMER
READINGS NORTH AND WEST WHERE CIRRUS SHOULD MOST PREVALENT. THE
CIRRUS MAY ALSO LIMIT STRATUS DEVELOPMENT IN THE WEAK RETURN FLOW
THAT HAS DEVELOPED. THE RAP IS MOST AGGRESSIVE WITH THE STRATUS BUT
APPEARS TO HAVE TRENDED LATER AND MORE PATCHY....FOCUSED MOSTLY
ACROSS THE SOUTHERN COASTAL PLAIN. LOWS 37-44.
&&
.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
AS OF 225 PM THURSDAY...
THE MAIN WEATHER PLAYERS FOR FRIDAY WILL BE THE LONG WAVE TROUGH
MOVING ACROSS THE ROCKIES AND SW STATES...AND A LENGTHY DRAWN-OUT
SFC FRONTAL SYSTEM THAT IS EXPECTED TO EXTEND FROM THE NEW ENGLAND
STATES...SOUTHWEST ACROSS THE MIDWEST...AND SOUTH ACROSS TEXAS.
ACROSS OUR AREA HOWEVER...HIGH PRESSURE CENTERED OVER THE WRN
ATLANTIC WILL CONTINUE TO INFLUENCE OUR WEATHER...PROVIDING FAIR
WEATHER AND WARMER TEMPERATURES AS LOW LEVEL SW FLOW CONTINUES TO
ADVECT WARMER AIR AND ADDITIONAL MOISTURE INTO OUR AREA. AS SUCH...
LOOK FOR PARTIAL SUNSHINE THROUGH A VEIL OF HIGH CLOUDS (AFTER ANY
MORNING LOW CLOUDS AND FOG BURN OFF)...BUT THE MAIN WEATHER STORY
WILL BE THE WARMER TEMPS...AS INCREASING LOW LEVEL THICKNESS VALUES
AND BL WARMING PER LATEST FORECAST SOUNDINGS SUGGEST EARLY-
SPRING-LIKE HIGHS IN THE MID-UPPER 60S.
WITH LITTLE CHANGE IN THE PATTERN FRIDAY NIGHT...LOOK FOR ADDITIONAL
PATCHY LOW CLOUDS AND FOG TO FORM TOWARD SUNRISE SATURDAY...AND LOW
TEMPS 15+ DEGREES ABOVE NORMAL...UPR 40S TO AROUND 50.
STRONG WARM AIR AND MOISTURE ADVECTION WILL CONTINUE AHEAD OF AN
APPROACHING COLD FRONT ON SATURDAY. HIGH CLOUDINESS WILL BE
WIDESPREAD...BUT EVEN MILKY SUN WILL ALLOW HIGHS TO SOAR INTO THE
UPPER 60S TO MID 70S WHICH SHOULD ECLIPSE RECORD HIGHS FOR THE 21ST
FOR RDU AND GSO...LISTED BELOW. AS THE FRONT CREEPS UP TO THE
WESTERN SLOPES...SCATTERED SHOWERS ARE EXPECTED IN THE WESTERN
PIEDMONT LATER SATURDAY NIGHT. ONGOING WARM FLOW AND CLOUD COVERAGE
WILL PRODUCE A VERY MILD NIGHT...WITH LOWS IN THE UPPER 50S TO
PERHAPS EVEN LOW 60S...WHICH ARE HIGHER THAN CLIMATOLOGICAL MAX
TEMPS FOR THE DATE.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 255 PM THURSDAY...
UPPER SHORT WAVE IS WELL OFF TO THE NORTHWEST OVER THE UPPER MID
WEST AND THE FRONT WILL BE STRETCHED/SHEARED MORE PARALLEL TO THE
MID AND UPPER FLOW...SO THERE IS NOT INITIALLY STRONG DRIVING FORCES
TO PROPEL THE FRONT EAST. THE LATEST GFS HAS NONETHELESS SPED UP
EASTWARD PROGRESSION ACROSS THE AREA LATE SUNDAY. WILL MAINTAIN A
SLOWER ECMWF TIMING...WITH LIKELY POPS IN THE FAR WESTERN PIEDMONT
LATE IN THE DAY...AND ONLY SMALL CHANCES IN THE EAST. THERE WILL BE
A STRONG LOW LEVEL JET (EXCEEDING 50KT AT H92-H85) WITH DIFFLUENT
FLOW ALOFT...SO ISOLATED THUNDER WILL BE MAINTAINED DESPITE WEAK
INSTABILITY. HIGHS WILL AGAIN APPROACH OR EXCEED RECORDS...WITH MOST
AREAS REACHING MID AND UPPER 70S.
LIKELY POPS EXPECTED SUNDAY NIGHT IN THE WEST...TRANSITIONING TO THE
EAST ON MONDAY AS THE FRONT SLOWS AND MODELS COME MORE IN ALIGNMENT
WITH A POSITION OVER THE COASTAL PLAIN BY MONDAY EVENING.
AGAIN...STRONG LOW LEVEL FORCING AND UPPER DYNAMICS SHOULD PRODUCE
ENOUGH LIFT FOR ISOLATED THUNDER. HIGHS MONDAY WILL BE LEVELING OFF
BY AFTERNOON IN THE WEST AFTER MAXING OUT IN THE UPPER 50S...
MEANWHILE...THE EAST WILL REACH THE MID AND UPPER 60S BEFORE THE
COLD AIR ADVECTION KICKS IN BEHIND THE FRONT. PRECIP WILL TAPER OFF
BY MIDNIGHT IN THE EAST...WITH DRIER AND COOLER AIR SURGING INTO THE
AREA MONDAY NIGHT...LOWS WILL BE IN THE 30S...WITH THE NORTHWEST
FALLING BELOW FREEZING.
HIGH PRESSURE WILL DOMINATE TUESDAY THROUGH THURSDAY...PROVIDING US
WITH COOL...BUT SEASONABLE TEMPERATURES THROUGH THE CHRISTMAS
HOLIDAY. TUESDAYS HIGHS WILL BE IN THE 40S...WITH 45 TO 50 DEGREES
EXPECTED ON CHRISTMAS DAY AFTER A MORNING LOW IN THE MID TO UPPER
20S. COOL AIR WILL BE LOOSENING ITS GRIP IN THE LATE WEEK...WITH AN
INVERTED TROF SETTING UP ALONG THE COAST TO PROVIDE INCREASED
CLOUDINESSS IN THE SOUTH AND EAST. HIGHS THURSDAY ARE LOW CONFIDENCE
AT THIS POINT...50 TO 55 LOOKS REASONABLE AT THIS POINT.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
AS OF 110 AM THURSDAY...
RETURN FLOW AROUND BERMUDA HIGH PRESSURE WILL RESULT IN CONTIUED LOW
LEVEL MOISTENING OF THE VERY DRY ANTECEDENT AIR MASS...AND THIS MAY
LEAD TO SOME LOW STRATUS (LOW TO MEDIUM CONFIDENCE) GENERALLY IN THE
LOW END MVFR/IFR RANGE BY AROUND DAYBREAK AT KGSO/KINT AND POSSIBLY
KFAY (MAYBE MORE VISBY RESTRICTIONS AT FIRST AT KFAY). CANT RULE OUT
SOME BRIEF SUB VFR CONDITIONS AT KRDU AND KRWI AS WELL. EXPECT ANY
LOW STRATUS AND/OR FOG WILL MIX OUT BY 16/17Z AT THE LATEST. VFR
CONDITIONS ARE THEN EXPECTED TO CONTINUE FOR THE REMAINDER OF THE
TAF PERIOD. HOWEVER... WE WILL LIKELY SEE SUSTAINED WINDS DURING
FRIDAY AFTERNOON IN THE 10 TO 15 MPH RANGE... WITH GUSTS POSSIBLE IN
THE 20 TO 25 MPH RANGE.
LOOKING AHEAD: WARM/MOIST SOUTHERLY RETURN FLOW WILL INCREASE ACROSS
THE CAROLINAS THROUGH SUNDAY NIGHT. LOW STRATUS WILL BE POSSIBLE
MAINLY EACH MORNING...FOLLOWED BY NUMEROUS SHOWERS WITH THE PASSAGE
OF A COLD FRONT SUNDAY NIGHT AND MONDAY.
&&
.CLIMATE...
AS OF 230 PM WEDNESDAY...
DAILY RECORDS FOR SATURDAY/SUNDAY DECEMBER 21/22 ARE AS FOLLOWS:
RALEIGH/DURHAM...
HIGHHI MIN
DECEMBER 21... 71 DEGREES...SET IN 196759 DEGREES...SET IN 1923
DECEMBER 22... 75 DEGREES...SET IN 196761 DEGREES...SET IN 2011
--------------------------------------------------------------------
GREENSBORO...
HIGHHI MIN
DECEMBER 21... 66 DEGREES...SET IN 192355 DEGREES...SET IN 1984
DECEMBER 22... 71 DEGREES...SET IN 192360 DEGREES...SET IN 2011
--------------------------------------------------------------------
FAYETTEVILLE...
HIGHHI MIN
DECEMBER 21... 77 DEGREES...SET IN 193160 DEGREES...SET IN 1923
DECEMBER 22... 75 DEGREES...SET IN 201160 DEGREES...SET IN 2011
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE
&&
$$
SYNOPSIS...26
NEAR TERM...NP/SMITH
SHORT TERM...NP
LONG TERM...MLM
AVIATION...26
CLIMATE...RAH
FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
351 AM CST FRI DEC 20 2013
.TODAY AND TONIGHT...FORECAST CONFIDENCE...MEDIUM TO HIGH
SURFACE LOW PRESSURE WILL SLOWLY MOVE ACROSS CENTRAL IL AND IN
TODAY. THE 850MB BAROCLINIC ZONE WILL REMAIN STATIONARY OVER
SOUTHERN WI...WITH THE SURFACE AND 925MB FRONT OVER NORTHERN IL.
SURFACE TEMPS WILL REMAIN BELOW FREEZING TODAY EXCEPT FOR RIGHT
ALONG THE SHORELINE.
A PERSISTENT DRY LAYER FROM 10-15 KFT IS EXPECTED TO HANG IN THERE
THROUGH THE DAY...POSSIBLY MOISTENING UP LATE THIS AFTERNOON. THIS
MEANS THAT SATURATED...SUB-FREEZING CONDITIONS FROM THE GROUND UP TO
AROUND 8KFT TODAY WILL CONTINUE TO PRODUCE LIGHT FREEZING
DRIZZLE. IF THE DEEPER SATURATION CAN OCCUR TO GET SOME SNOW
PRODUCTION...THEN SNOW COULD MIX IN WITH THE FREEZING DRIZZLE/RAIN
THIS AFTERNOON.
AS FOR FORCING...THE STRONGER 850-700MB WARM AIR ADVECTION THAT
PRODUCED SHOWERY PRECIP IN THE EVENING THROUGH AROUND 2 AM IS EASING
UP THIS MORNING...BUT EXPECTED TO RAMP UP AGAIN EARLY THIS AFTERNOON
WITH A PASSING WEAK SHORTWAVE. THE NAM AND HRRR MODELS SHOW A LULL
IN PRECIP FOR ABOUT 3 HOURS MID MORNING...THEN ANOTHER ROUND OF
SHOWERY PRECIP THIS AFTERNOON.
THUS...EXTENDED THE FREEZING RAIN ADVISORY UNTIL 21Z FOR MOST OF MKX
FORECAST AREA. ONLY EXTENDED THE NORTHERN TIER OF COUNTIES UNTIL 18Z
SINCE DEEPER SATURATION SHOULD LEAD TO MORE SNOW THAN FREEZING
RAIN/DRIZZLE THERE. AGAIN...LAKESHORE AREAS WILL BE MARGINAL FOR THE
BELOW-FREEZING TEMPS TODAY TO MAINTAIN THE FREEZING RAIN
THREAT...BUT INLAND PORTIONS OF THE LAKE COUNTIES ARE EXPECTED TO
REMAIN BELOW FREEZING SO KEPT ALL COUNTIES IN THE ADVISORY.
LIGHT FREEZING DRIZZLE COULD PERSIST INTO THE EVENING...BUT DRYING
IS EXPECTED TO WORK INTO THE LOWER LEVELS AS THE SURFACE LOW SLIDES
EAST. WITH CLOUDS LINGERING OVER SOUTHERN WI...TEMPS WILL REMAIN
MODERATE...WITH LOWS DROPPING INTO THE UPPER TEENS TOWARD CENTRAL WI
AND THE UPPER 20S IN SOUTHEAST WI.
.SATURDAY AND SUNDAY...FORECAST CONFIDENCE...MEDIUM TO HIGH
NOT MUCH HAS CHANGED WITH WEEKEND WINTER STORM...AS LATEST MODELS
STILL TAKE AIM AT SOUTHERN WISCONSIN. MAIN NOTICEABLE CHANGES ARE
AN OVERALL CONSENSUS INCREASE IN QPF AND VERY SLIGHT SHIFT
SOUTHWARD. THIS MINOR SHIFT RESULTED IN THE 00Z GUIDANCE
SUGGESTING SNOW FOR ALL OF THE FORECAST AREA...WITH THE MILDER AIR
ALOFT STAYING SOUTH.
OVERALL...LOOKS LIKE A PRETTY SOLID WINTER STORM IF THE CURRENT
DETAILS HOLD. CONSENSUS SFC LOW TRACK FROM WEST-CENTRAL INDIANA TO
SE MICHIGAN AND 700 MB LOW TRACK ACROSS SOUTHERN WISCONSIN ARE
USUALLY GOOD INDICATORS FOR A DECENT SNOWFALL. IN ADDITION...THOUGH
THE DENDRITE GROWTH ZONE IS NOT PARTICULARLY DEEP...FORCING WITHIN
THIS REGION REMAINS STRONG. WILL ALSO GET A BIT OF UPPER SUPPORT
AT THE ONSET OF THIS SYSTEM...AS THE FORECAST AREA WILL WITHIN THE
RIGHT ENTRANCE REGION OF A VERY STRONG UPPER JET. LATEST FORECAST
HAS THE HIGHEST AMOUNTS ACROSS THE SOUTHEAST TWO-THIRDS OF THE
FORECAST AREA...TAPERING OFF QUICKLY TOWARD THE FAR NW. THE SNOW
IS CURRENTLY EXPECTED TO MOVE IN DURING THE EVENING...WITH THE
HEAVIER SNOW ARRIVING BY MIDNIGHT AND PERSISTING INTO EARLY SUNDAY
MORNING.
WILL MAINTAIN THE WINTER STORM WATCH AS IS FOR NOW...AS THE STORM
IS A BIT TOO FAR OUT FOR A WARNING. ALSO...IT WOULD NOT TAKE MUCH
OF A SHIFT NORTH OR SOUTH IN THE STORM TRACK TO IMPACT CURRENT
EXPECTED AMOUNTS. THIS IS INCREASING CONFIDENCE WITH THIS SYSTEM
THOUGH...AS MODELS SEEM TO BE SETTLING ON A SOLUTION.
LIGHT SNOW MAY LINGER INTO SUNDAY NIGHT AS THE UPPER TROUGH
APPROACHES.
.MONDAY THOUGH THURSDAY...FORECAST CONFIDENCE...LOW TO MEDIUM
LOOKS LIKE BELOW NORMAL TEMPS NEXT WEEK...WITH A CHANCE FOR LIGHT
SNOW AT TIMES AS SERIES OF SHORTWAVES PUSH THROUGH THE AREA. COULD
GET PRETTY CHILLY A COUPLE OF THE NIGHTS...WITH MODELS SUGGESTING
SUB-ZERO TEMPS. MAIN ISSUE WITH THIS PERIOD IS THAT MODELS ARE NOT
AGREEING VERY WELL ON THE TIMING OF THE WAVES AND EXTENT OF COLDER
TEMPS BEHIND THE WAVES. THUS KEPT POPS ON THE LOW END FOR NOW AND
DID NOT GO QUITE AS COLD AS SOME OF THE MODELS SUGGEST.
&&
.AVIATION/12Z TAFS/ AND MARINE...THESE SECTIONS WILL BE ADDED
SHORTLY.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR
WIZ056>060-062>072.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ046-047-051-052-056>060-062>072.
FREEZING RAIN ADVISORY UNTIL NOON CST TODAY FOR WIZ046-047-051-
052.
LM...WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR LMZ643.
SMALL CRAFT ADVISORY UNTIL 6 PM CST THIS EVENING FOR LMZ643>646.
&&
$$
TODAY/TONIGHT AND AVIATION/MARINE...MRC
SATURDAY THROUGH THURSDAY...DDV
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
324 AM CST FRI DEC 20 2013
.UPDATE...
ISSUED AT 323 AM CST FRI DEC 20 2013
PRELIMINARY CHANGES TO THE FREEZING RAIN ADVISORY BELOW. PLEASE
NOTE THE NORTHERNMOST COUNTIES MAY CHANGE OVER THE NEXT HOUR BASED
ON TRENDS.
UPDATE ISSUED AT 926 PM CST THU DEC 19 2013
RADAR/OBSERVATION TRENDS CONTINUE TO SHOW THE BAND OF FREEZING
DRIZZLE SURGING NORTHWARD ACROSS SOUTHEAST MINNESOTA AND WESTERN
WISCONSIN. WILL BE ADDING SOME COUNTIES TO THE FREEZING RAIN
ADVISORY...LIKELY THE REST OF THE FORECAST AREA EXCEPT
CLARK/TAYLOR COUNTIES WHERE ICE APPEARS TO BE IN FOR THE FULL
SATURATED COLUMN. ROADS HAVE ICED UP ACROSS SOUTHWEST WISCONSIN
AND NORTHEAST IOWA WHERE THE FREEZING DRIZZLE/RAIN HAS PERSISTED.
UPDATE COMING SHORTLY.
&&
.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 307 PM CST THU DEC 19 2013
AS OF MID AFTERNOON THURSDAY...AREA OF LOW PRESSURE SITUATED IN
NORTHEAST KANSAS WITH WARM FRONT EXTENDING NORTHEAST INTO SOUTHERN
IOWA AND NORTHERN ILLINOIS. INCREASING ISENTROPIC LIFT LATER THIS
EVENING AND MOISTURE TRANSPORT OVERRUNNING THE WARM FRONT WILL
SATURATE THE LOW LEVELS...ESPECIALLY AFTER 00Z. FORECAST SOUNDINGS
STILL SHOW A COMPLICATED TOP DOWN PRECIPITATION TYPE SCENARIO WITH
BOTH A WARM NOSE AND A LOSS OF ICE IN THE UPPER LEVELS. FIRST...THE
PROBABILITY OF NO ICE PRESENT SHIFTED SLIGHTLY NORTH FROM
PREVIOUS FORECAST. 19.12Z NAM AND RAP NOW SHOW THIS EXTENDING NORTH
TO JUST SHY OF THE I-90 CORRIDOR IN WISCONSIN. IT IS NOT UNTIL VERY
EARLY FRIDAY MORNING THAT ICE GETS REINTRODUCED...AND A CHANGEOVER
TO LIGHT SNOW WOULD THEN OCCUR FOR PLACES SUCH AS VIROQUA OVER TO
JUNEAU/ADAMS COUNTIES. AT THE SAME TIME...RAP SOUNDINGS FOR DBQ
SHOW MAX WARM NOSE OF +4 DEGREES...AROUND +1 FOR BLR...AND THEN
BELOW ZERO FOR AREAS TO THE NORTH. SO...TIGHT GRADIENT FOR
FREEZING RAIN AND SNOW LINE. AS FAR AS ICE ACCUMULATIONS...UP TO
1/10 OF AN INCH STILL EXPECTED ON EXPOSED SURFACES...WHICH WILL
MAKE FOR SLICK TRAVEL OVERNIGHT INTO THE MORNING HOURS FRIDAY.
GIVEN THIS NORTHWARD JOG IN THE LOSS OF ICE / WARM NOSE...HAVE
EXPANDED THE FREEZING RAIN ADVISORY TO INCLUDE VERNON...JUNEAU AND
ADAMS COUNTIES IN WISCONSIN.
THE NORTHERN SIDE OF THIS WEATHER SYSTEM STILL EXPECTED TO PRODUCE A
BAND OF ACCUMULATING SNOW ALONG AND NORTH OF I-90...MAINLY AFTER
MIDNIGHT INTO FRIDAY MORNING. NO BIG CHANGES FROM
PREVIOUS FORECAST...WITH 1 TO 2 INCHES FOR MOST LOCATIONS AND
LOCALLY 3 INCH AMOUNTS POSSIBLE MAINLY FOR CENTRAL WISCONSIN. THIS
TOO COULD MAKE FOR SLICK ROADWAYS FOR THE FRIDAY MORNING
COMMUTE...AND CONSIDERED A HEADLINE FOR THIS BUT WILL HOLD OFF NOW
GIVEN COLLABORATION. IF LATER FORECASTS SHOW AN UPTICK IN
AMOUNTS...OR A DELAY MORE TOWARD THE MORNING COMMUTE...THEN AN
WINTER WEATHER ADVISORY MAY BE NEEDED FOR A FEW COUNTIES.
.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 307 PM CST THU DEC 19 2013
FOCUS OF THIS PERIOD IS SQUARELY ON THE WEEKEND AND THE POTENTIAL
FOR A WINTER STORM TO IMPACT PARTS OF THE FORECAST AREA. STILL
SOME DIFFERENCES BETWEEN THE MODELS BUT THE 19.12Z GFS AND ECMWF
ARE IN BETTER AGREEMENT WITH THE OVERALL PATTERN WITH THE 19.12Z
NAM APPEARING AT THIS TIME TO BE THE ODD MODEL OUT. THE UPPER
LEVEL LOW CURRENTLY ALONG THE CALIFORNIA COAST WILL MOVE OUT OF
THE DESERT SOUTHWEST AND TRACK NORTHEAST ACROSS THE CENTRAL
PORTION OF THE COUNTRY OVER THE WEEKEND. AS IT MOVES TOWARD THE
AREA...A NORTHERN STREAM SHORT WAVE WILL START TO MOVE TOWARD THE
UPPER MIDWEST FROM SOUTHWEST CANADA. THE DIFFERENCES IN THE MODEL
SOLUTIONS REVOLVE AROUND WHETHER THESE TWO SYSTEMS GET PHASED OR
WHETHER THEY STAY SEPARATE. THE NAM WOULD SUGGEST THEY GET PHASED
WHICH PUSHES THE SURFACE LOW AND ASSOCIATED QPF FARTHER SOUTHEAST.
THE GFS AND ECMWF DO NOT PHASE THE TWO SYSTEMS WHICH BRINGS THE
SURFACE LOW AND QPF BACK MORE TO THE NORTHWEST.
THE FORCING FROM THE SHORT WAVE TROUGH WILL START TO MOVE IN
SATURDAY NIGHT. MODERATE TO STRONG PV ADVECTION IN THE 500-300 MB
LAYER SHOULD OCCUR LATE SATURDAY NIGHT JUST AHEAD OF THE WAVES
PASSAGE. MODERATE TO STRONG QG CONVERGENCE WILL BE PRODUCED BY THE
WAVE AND CENTERED OVER THE SOUTHEAST PART OF THE FORECAST AREA AT
12Z SUNDAY. WEAK TO MODERATE FRONTOGENESIS IS SHOWN BY THE GFS IN
THE 600-500 MB LAYER BETWEEN 06Z AND 18Z SUNDAY...ALSO OVER THE
SOUTHEAST PORTIONS OF THE FORECAST AREA. THERE MAY ALSO BE SOME
JET DYNAMICS THAT COME INTO PLAY AS WELL. THE GFS IS SUGGESTING A
SPLIT JET WITH THE AREA UNDER THE RIGHT ENTRANCE REGION OF THE
NORTHERN STREAM JET CORE TO ADD SOME AGEOSTROPHIC LIFT TO THE MIX.
THE GFS BUFKIT SOUNDING FOR BLUE RIVER SUGGEST THE DENDRITIC
GROWTH ZONE SHOULD BE ABOUT 100 MB DEEP WITH GOOD VERTICAL MOTIONS
THROUGH IT. THIS SHOULD LEAD TO SNOW RATIOS IN THE 14-16 TO 1
RANGE LEADING TO SNOW ACCUMULATIONS OF 4 TO 7 INCHES FROM ABOUT
FAYETTE COUNTY IOWA NORTHEAST INTO ADAMS/JUNEAU COUNTIES IN
CENTRAL WISCONSIN. THE POTENTIAL FOR THE HIGHER AMOUNTS IS THE
GREATEST IN PRIMARILY GRANT COUNTY WISCONSIN. THE NORTHWEST WINDS
WILL COME UP SUNDAY ON THE BACK SIDE OF THE SYSTEM WHICH WILL
LIKELY LEAD TO SOME DRIFTING SNOW AND POSSIBLY A LITTLE BLOWING
SNOW OVER THE MORE OPEN AREAS OF NORTHEAST IOWA. IN COORDINATION
WITH SURROUNDING OFFICES...WILL ISSUE A WINTER STORM WATCH FOR
SATURDAY NIGHT AND SUNDAY FOR THE ACCUMULATING SNOW AND ANY
POSSIBLE IMPACT ON THE BACK SIDE OF THE SYSTEM.
WITH THE FOCUS ON THE WEEKEND SYSTEM...HAVE NOT LOOKED EXTENSIVELY
AT THE FORECAST FOR NEXT WEEK. HAVE LET THE MODEL CONSENSUS GRIDS
RIDE WHICH GIVES A SMALL CHANCE FOR SOME SNOW TUESDAY AND TUESDAY
NIGHT ACROSS THE NORTH AS ANOTHER NORTHERN STREAM SHORT WAVE
TROUGH MOVES ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION. THE
COLDEST TEMPERATURES IN THE FORECAST LOOK TO BE BEHIND THE WEEKEND
SYSTEM WITH LOWS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO SUNDAY
NIGHT...HIGHS ONLY IN THE SINGLE DIGITS ABOVE ZERO MONDAY WITH
SINGLE DIGITS BELOW ZERO FOR THE ENTIRE AREA MONDAY NIGHT.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1137 PM CST THU DEC 19 2013
FREEZING RAIN AND DRIZZLE HAS SPREAD ACROSS THE REGION WITH
CONDITIONS DROPPING FROM MVFR TO IFR AS THE MAIN BAND OF DRIZZLE
MOVES IN. THIS WILL CREATE ICY CONDITIONS THROUGH MID TO LATE
MORNING ON FRIDAY. THIS FREEZING RAIN/DRIZZLE IS EXPECTED TO
CHANGE OVER TO LIGHT SNOW FOR A PERIOD ON FRIDAY BEFORE POSSIBLY
GOING BACK TO FREEZING DRIZZLE THROUGH THE REST OF THE DAY.
CONFIDENCE IS NOT HIGH ON WHETHER THAT SECOND CHANGE OVER WILL
OCCUR BACK TO DRIZZLE...BUT IT LOOKS POSSIBLE. CONDITIONS WILL
REMAIN MVFR TO IFR WITH WINDS SHIFTING FROM THE EAST TO NORTHEAST
IN THE AFTERNOON.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL NOON CST TODAY FOR WIZ041>044-053.
FREEZING RAIN ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR WIZ054-
055-061.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ043-044-053>055-061.
MN...FREEZING RAIN ADVISORY UNTIL NOON CST TODAY FOR MNZ095-096.
IA...FREEZING RAIN ADVISORY UNTIL NOON CST TODAY FOR IAZ008>010-018-
019.
FREEZING RAIN ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR IAZ011-
029-030.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR IAZ011-029-030.
&&
$$
UPDATE...BAUMGARDT
SHORT TERM...ZT
LONG TERM...04
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1137 PM CST THU DEC 19 2013
.UPDATE...
ISSUED AT 926 PM CST THU DEC 19 2013
RADAR/OBSERVATION TRENDS CONTINUE TO SHOW THE BAND OF FREEZING
DRIZZLE SURGING NORTHWARD ACROSS SOUTHEAST MINNESOTA AND WESTERN
WISCONSIN. WILL BE ADDING SOME COUNTIES TO THE FREEZING RAIN
ADVISORY...LIKELY THE REST OF THE FORECAST AREA EXCEPT
CLARK/TAYLOR COUNTIES WHERE ICE APPEARS TO BE IN FOR THE FULL
SATURATED COLUMN. ROADS HAVE ICED UP ACROSS SOUTHWEST WISCONSIN
AND NORTHEAST IOWA WHERE THE FREEZING DRIZZLE/RAIN HAS PERSISTED.
UPDATE COMING SHORTLY.
&&
.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 307 PM CST THU DEC 19 2013
AS OF MID AFTERNOON THURSDAY...AREA OF LOW PRESSURE SITUATED IN
NORTHEAST KANSAS WITH WARM FRONT EXTENDING NORTHEAST INTO SOUTHERN
IOWA AND NORTHERN ILLINOIS. INCREASING ISENTROPIC LIFT LATER THIS
EVENING AND MOISTURE TRANSPORT OVERRUNNING THE WARM FRONT WILL
SATURATE THE LOW LEVELS...ESPECIALLY AFTER 00Z. FORECAST SOUNDINGS
STILL SHOW A COMPLICATED TOP DOWN PRECIPITATION TYPE SCENARIO WITH
BOTH A WARM NOSE AND A LOSS OF ICE IN THE UPPER LEVELS. FIRST...THE
PROBABILITY OF NO ICE PRESENT SHIFTED SLIGHTLY NORTH FROM
PREVIOUS FORECAST. 19.12Z NAM AND RAP NOW SHOW THIS EXTENDING NORTH
TO JUST SHY OF THE I-90 CORRIDOR IN WISCONSIN. IT IS NOT UNTIL VERY
EARLY FRIDAY MORNING THAT ICE GETS REINTRODUCED...AND A CHANGEOVER
TO LIGHT SNOW WOULD THEN OCCUR FOR PLACES SUCH AS VIROQUA OVER TO
JUNEAU/ADAMS COUNTIES. AT THE SAME TIME...RAP SOUNDINGS FOR DBQ
SHOW MAX WARM NOSE OF +4 DEGREES...AROUND +1 FOR BLR...AND THEN
BELOW ZERO FOR AREAS TO THE NORTH. SO...TIGHT GRADIENT FOR
FREEZING RAIN AND SNOW LINE. AS FAR AS ICE ACCUMULATIONS...UP TO
1/10 OF AN INCH STILL EXPECTED ON EXPOSED SURFACES...WHICH WILL
MAKE FOR SLICK TRAVEL OVERNIGHT INTO THE MORNING HOURS FRIDAY.
GIVEN THIS NORTHWARD JOG IN THE LOSS OF ICE / WARM NOSE...HAVE
EXPANDED THE FREEZING RAIN ADVISORY TO INCLUDE VERNON...JUNEAU AND
ADAMS COUNTIES IN WISCONSIN.
THE NORTHERN SIDE OF THIS WEATHER SYSTEM STILL EXPECTED TO PRODUCE A
BAND OF ACCUMULATING SNOW ALONG AND NORTH OF I-90...MAINLY AFTER
MIDNIGHT INTO FRIDAY MORNING. NO BIG CHANGES FROM
PREVIOUS FORECAST...WITH 1 TO 2 INCHES FOR MOST LOCATIONS AND
LOCALLY 3 INCH AMOUNTS POSSIBLE MAINLY FOR CENTRAL WISCONSIN. THIS
TOO COULD MAKE FOR SLICK ROADWAYS FOR THE FRIDAY MORNING
COMMUTE...AND CONSIDERED A HEADLINE FOR THIS BUT WILL HOLD OFF NOW
GIVEN COLLABORATION. IF LATER FORECASTS SHOW AN UPTICK IN
AMOUNTS...OR A DELAY MORE TOWARD THE MORNING COMMUTE...THEN AN
WINTER WEATHER ADVISORY MAY BE NEEDED FOR A FEW COUNTIES.
.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 307 PM CST THU DEC 19 2013
FOCUS OF THIS PERIOD IS SQUARELY ON THE WEEKEND AND THE POTENTIAL
FOR A WINTER STORM TO IMPACT PARTS OF THE FORECAST AREA. STILL
SOME DIFFERENCES BETWEEN THE MODELS BUT THE 19.12Z GFS AND ECMWF
ARE IN BETTER AGREEMENT WITH THE OVERALL PATTERN WITH THE 19.12Z
NAM APPEARING AT THIS TIME TO BE THE ODD MODEL OUT. THE UPPER
LEVEL LOW CURRENTLY ALONG THE CALIFORNIA COAST WILL MOVE OUT OF
THE DESERT SOUTHWEST AND TRACK NORTHEAST ACROSS THE CENTRAL
PORTION OF THE COUNTRY OVER THE WEEKEND. AS IT MOVES TOWARD THE
AREA...A NORTHERN STREAM SHORT WAVE WILL START TO MOVE TOWARD THE
UPPER MIDWEST FROM SOUTHWEST CANADA. THE DIFFERENCES IN THE MODEL
SOLUTIONS REVOLVE AROUND WHETHER THESE TWO SYSTEMS GET PHASED OR
WHETHER THEY STAY SEPARATE. THE NAM WOULD SUGGEST THEY GET PHASED
WHICH PUSHES THE SURFACE LOW AND ASSOCIATED QPF FARTHER SOUTHEAST.
THE GFS AND ECMWF DO NOT PHASE THE TWO SYSTEMS WHICH BRINGS THE
SURFACE LOW AND QPF BACK MORE TO THE NORTHWEST.
THE FORCING FROM THE SHORT WAVE TROUGH WILL START TO MOVE IN
SATURDAY NIGHT. MODERATE TO STRONG PV ADVECTION IN THE 500-300 MB
LAYER SHOULD OCCUR LATE SATURDAY NIGHT JUST AHEAD OF THE WAVES
PASSAGE. MODERATE TO STRONG QG CONVERGENCE WILL BE PRODUCED BY THE
WAVE AND CENTERED OVER THE SOUTHEAST PART OF THE FORECAST AREA AT
12Z SUNDAY. WEAK TO MODERATE FRONTOGENESIS IS SHOWN BY THE GFS IN
THE 600-500 MB LAYER BETWEEN 06Z AND 18Z SUNDAY...ALSO OVER THE
SOUTHEAST PORTIONS OF THE FORECAST AREA. THERE MAY ALSO BE SOME
JET DYNAMICS THAT COME INTO PLAY AS WELL. THE GFS IS SUGGESTING A
SPLIT JET WITH THE AREA UNDER THE RIGHT ENTRANCE REGION OF THE
NORTHERN STREAM JET CORE TO ADD SOME AGEOSTROPHIC LIFT TO THE MIX.
THE GFS BUFKIT SOUNDING FOR BLUE RIVER SUGGEST THE DENDRITIC
GROWTH ZONE SHOULD BE ABOUT 100 MB DEEP WITH GOOD VERTICAL MOTIONS
THROUGH IT. THIS SHOULD LEAD TO SNOW RATIOS IN THE 14-16 TO 1
RANGE LEADING TO SNOW ACCUMULATIONS OF 4 TO 7 INCHES FROM ABOUT
FAYETTE COUNTY IOWA NORTHEAST INTO ADAMS/JUNEAU COUNTIES IN
CENTRAL WISCONSIN. THE POTENTIAL FOR THE HIGHER AMOUNTS IS THE
GREATEST IN PRIMARILY GRANT COUNTY WISCONSIN. THE NORTHWEST WINDS
WILL COME UP SUNDAY ON THE BACK SIDE OF THE SYSTEM WHICH WILL
LIKELY LEAD TO SOME DRIFTING SNOW AND POSSIBLY A LITTLE BLOWING
SNOW OVER THE MORE OPEN AREAS OF NORTHEAST IOWA. IN COORDINATION
WITH SURROUNDING OFFICES...WILL ISSUE A WINTER STORM WATCH FOR
SATURDAY NIGHT AND SUNDAY FOR THE ACCUMULATING SNOW AND ANY
POSSIBLE IMPACT ON THE BACK SIDE OF THE SYSTEM.
WITH THE FOCUS ON THE WEEKEND SYSTEM...HAVE NOT LOOKED EXTENSIVELY
AT THE FORECAST FOR NEXT WEEK. HAVE LET THE MODEL CONSENSUS GRIDS
RIDE WHICH GIVES A SMALL CHANCE FOR SOME SNOW TUESDAY AND TUESDAY
NIGHT ACROSS THE NORTH AS ANOTHER NORTHERN STREAM SHORT WAVE
TROUGH MOVES ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION. THE
COLDEST TEMPERATURES IN THE FORECAST LOOK TO BE BEHIND THE WEEKEND
SYSTEM WITH LOWS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO SUNDAY
NIGHT...HIGHS ONLY IN THE SINGLE DIGITS ABOVE ZERO MONDAY WITH
SINGLE DIGITS BELOW ZERO FOR THE ENTIRE AREA MONDAY NIGHT.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1137 PM CST THU DEC 19 2013
FREEZING RAIN AND DRIZZLE HAS SPREAD ACROSS THE REGION WITH
CONDITIONS DROPPING FROM MVFR TO IFR AS THE MAIN BAND OF DRIZZLE
MOVES IN. THIS WILL CREATE ICY CONDITIONS THROUGH MID TO LATE
MORNING ON FRIDAY. THIS FREEZING RAIN/DRIZZLE IS EXPECTED TO
CHANGE OVER TO LIGHT SNOW FOR A PERIOD ON FRIDAY BEFORE POSSIBLY
GOING BACK TO FREEZING DRIZZLE THROUGH THE REST OF THE DAY.
CONFIDENCE IS NOT HIGH ON WHETHER THAT SECOND CHANGE OVER WILL
OCCUR BACK TO DRIZZLE...BUT IT LOOKS POSSIBLE. CONDITIONS WILL
REMAIN MVFR TO IFR WITH WINDS SHIFTING FROM THE EAST TO NORTHEAST
IN THE AFTERNOON.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR WIZ032>034-
041>044-053>055-061.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ043-044-053>055-061.
MN...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR MNZ079-086>088-
094>096.
IA...FREEZING RAIN ADVISORY UNTIL 9 AM CST FRIDAY FOR IAZ008>011-018-
019-029-030.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR IAZ011-029-030.
&&
$$
UPDATE...HALBACH
SHORT TERM...ZT
LONG TERM...04
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS PUEBLO CO
545 AM MST FRI DEC 20 2013
.UPDATE...
ISSUED AT 542 AM MST FRI DEC 20 2013
UPDATED THE FORECAST TO ADD FZFG TO EL PASO COUNTY FOR THE
MORNING HOURS. LIGHT PRECIP WILL LIKELY NOT MEASURE SO WILL LEAVE
AREA LOW POPS INTACT. ROSE
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 250 AM MST FRI DEC 20 2013
...MUCH COOLER TODAY...
...SNOW CHANCES NOT LOOKING TOO GREAT...
CURRENTLY...SOME LIGHT SHSN OVER THE WRN PORTION OF THE
STATE...MAINLY INVOF KGJT. SOME LIGHT PRECIP ALSO LIKELY MOVING INTO
THE SAWATCH RANGE AND CONTDVD THRU THE MORNING HOURS. TEMPS MAINLY
IN THE 20S...WITH SOME SINGLE DIGITS FOR THE HIGH VALLEYS. EXTENSIVE
LOW CLOUD DECK NOW COVERING THE ERN PLAINS...BUT FAIRLY SHALLOW AND
THE ERN MTS ARE ACTUALLY RELATIVELY CLEAR THIS MORN.
MAIN QUESTION TODAY IS HOW LONG THE LOW CLOUDS WILL TAKE TO BREAK UP
OVER THE PLAINS. THIS WILL DETERMINE POTENTIAL HIGH TEMPS TODAY.
CURRENT MODEL SOUNDINGS ARE NOT VERY HELPFUL...WITH THE NAM BREAKING
THINGS OUT PRETTY EARLY AND THE RAP HOLDING ON TO A LOW CLOUD DECK
THROUGH THE EARLY AFTERNOON. GIVEN THE PRETTY STOUT LLVL INVERSION
AS ALREADY HINTED OUT IN THE 00Z DEN SOUNDING...AND THE GENERALLY
LIGHT UPSLOPE WINDS EXPECTED OVER THE PLAINS...WILL LEAN TOWARDS A
LATER TIME FOR THE LOW CIGS TO DISSIPATE. THIS WILL KEEP AFTERNOON
HIGHS FROM REACHING THE POTENTIAL SUGGESTED BY H7 TEMPS ONLY A FEW
DEGREES BELOW ZERO. HAVE CUT BACK TEMPS A FEW DEGREES FROM CURRENT
FORECAST...BUT SOME GUIDANCE SUGGESTS THEY MAY EVEN END UP LOWER
THAN FORECAST. BOTTOM LINE...IT WILL BE A GOOD 20 DEGREES COOLER
THAN YESTERDAY...AND FINALLY FEEL LIKE DECEMBER FOR SERN CO.
SNOW POTENTIAL IS NOT LOOKING TOO GREAT TODAY. A NUMBER OF MODEL
SOUNDINGS SUGGEST SOME LIGHT PRECIP OVER THE PLAINS THIS MORN...BUT
GIVEN THE RELATIVELY SHALLOW CLOUD LAYER DO NOT EXPECT ANYTHING THAT
FALLS TO ACCUMULATE OR EVEN MEASURE. SO...HAVE KEPT POPS LOW FOR THE
PLAINS THROUGH TONIGHT. PERSISTENT LIGHT SHSN WILL BE ONGOING OVER
THE CONTDVD AND WILL PICK UP GRADUALLY AS WE GO THROUGH THE
AFTERNOON BEFORE TAPERING OFF THIS EVENING. BUT ACCUMS NOT LOOKING
TOO IMPRESSIVE WITH AT BEST A FEW INCHES OVER THE DVD BY SUN MORNING.
WITH SOME PARTIAL CLEARING TONIGHT AND LIGHT WINDS...TEMPS WILL BE
ON THE COLD SIDE...WITH SOME TEENS POSSIBLE FOR THE PLAINS AND
CONTINUED SINGLE DIGITS AND NEGATIVE READINGS FOR THE MTS AND HIGH
VALLEYS. ROSE
.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 250 AM MST FRI DEC 20 2013
SATURDAY INTO SUNDAY APPEARS TO BE THE MOST ACTIVE WX PD DURING THIS
FORECAST SEGMENT. THE SOUTHERN STORM TRACKING OVER NM MAY CLIP THE
FAR SE CORNER OF COLORADO...WHILE THE NORTHERN SYSTEM WILL LIKELY
BRING SNOW TO THE MOUNTAINS AND POSSIBLY PARTS OF THE I-25 CORRIDOR.
FOR THE FAR SE PLAINS...IT APPEARS THE BEST CHANCE OF BACA COUNTY
SEEING ANY PRECIP WILL BE SAT AFTERNOON AND EVENING. BOTH GFS AND EC
HAVE AN IMPRESSIVE BAND OF PRECIP DEVELOPING OVER THE N TX PHDL INTO
THE OK PHDL...WITH THE N PARTS OF THIS BAND ENTERING INTO SE BACA
COUNTY. ON THE OTHER HAND THE NAM (00Z AND 06Z RUNS) KEEP THE PRECIP
DOWN INTO TX. I HAVE LEANED TOWARDS THE GFS AND EC BUT HAVE
DECREASED POPS A BIT OVER THE BACA COUNTY REGION TO ACCOUNT FOR THE
TRENDS IN THE NAM GUIDANCE.
THE N TIER SYSTEM WILL DROP INTO CO DURING SAT MORNING AND MOVE
ACROSS THE REGION SAT NITE. SNOW IN THE C MTNS IS LIKELY...WITH A
GOOD CHANCE OF SNOW OVER MOST OF THE OTHER MTNS DURING THE LATTER
AFTERNOON AND EVENING HOURS. IT DOES NOT APPEAR THAT ANY SIGNIF
ACCUMS WILL OCCUR...BUT 2-3" IS NOT OUT OF THE QUESTION...ESPECIALLY
ON THE NW SLOPES. SOME SNOW SHOWERS MAY MAKE IT OUT ONTO THE I-25
CORRIDOR...ESPECIALLY SAT EVE/NITE.
DRY AND COOL WX WILL BE LIKELY LATER SUNDAY INTO EARLY TUESDAY.
TUESDAY..XMAS EVE..MAY BE RATHER QUITE NICE GIVEN THE LEE TROUGH AND
DOWNSLOPE. TEMPS ON THE PLAINS WILL LIKELY BE IN THE 50S WITH A 60
OR TWO POSSIBLE.
BY LATE TUESDAY/TUE NITE ANOTHER COLD FRONT WILL MOVE ACROSS THE
REGION. HOWEVER...THIS SYSTEM LOOKS WEAKER ON BOTH THE EC AND GFS
AND THE CHANCE OF SNOW IS DECREASING FOR XMAS EVE INTO XMAS FOR THE
ENTIRE REGION. I HAVE NOT REMOVED POPS COMPLETELY...BUT THE TREND IN THE
GUIDANCE IS SHOWING THE SNOW CHANCES FOR THE LOWER ELEVATIONS
DECREASING. I WOULD NOT BE TOO SURPRISED IF LATER SHIFTS REMOVE THE
POPS COMPLETELY FOR THE LOWER ELEVATIONS XMAS EVE INTO XMAS. TEMPS
XMAS DAY WILL BE A GOOD 10-20F COOLER THAN XMAS EVE.
ANOTHER DISTURBANCE WILL MOVE DOWN ACROSS THE REGION ON FRIDAY
BRINGING ANOTHER COOL FRONT TO THE REGION. /HODANISH
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 250 AM MST FRI DEC 20 2013
MAIN QUESTION IS HOW QUICKLY IFR-MVFR CIGS WILL CLEAR FROM THE
PLAINS TODAY. WITH GENERALLY LIGHT UPSLOPE WINDS AND STRONG
TEMPERATURE INVERSIONS...EXPECT CIGS TO STAY LOW FOR A GOOD PORTION
OF THIS MORNING AND POSSIBLY THROUGH THE AFTERNOON...FOR KPUB FROM
17-18Z...AND AT KCOS 18-19Z. NO ACCUMULATING PRECIP IS EXPECTED BUT
SOME LIGHT PRECIP WILL BE POSSIBLE WITHIN THE LOW CLOUD DECK...WITH
TOPS BREAKING OUT ONLY 1000 FT OR SO AGL. VFR CONDITIONS WILL THEN
PERSIST THROUGH SUN MORNING. LIGHT SHSN WILL CONTINUE THROUGH THIS
EVE OVER THE CONTDVD...WITH MT TOPS OBSCURED DURING THIS PERIOD.
AT KALS...SOME LOCAL PC FG OR BR POSSIBLE THROUGH 15-16Z...AND AGAIN
LATE TONIGHT...BUT WILL STICK WITH A PERSISTENCE FORECAST FOR NOW IN
THE TAFS AND LEAVE CONDITIONS VFR. ROSE
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...ROSE
SHORT TERM...ROSE
LONG TERM...HODANISH
AVIATION...ROSE
AREA FORECAST DISCUSSION
NWS ALBANY NY
930 AM EST FRI DEC 20 2013
.SYNOPSIS...
WAVES OF LOW PRESSURE WILL TRACK ALONG A NEARLY STATIONARY FRONT
FROM THE GREAT LAKES THROUGH NORTHERN NEW YORK AND NORTHERN NEW
ENGLAND THROUGH TONIGHT. THE FRONT WILL SINK SOUTH AS A COLD FRONT
INTO PARTS OF CENTRAL NEW YORK AND SOUTHERN VERMONT SATURDAY
NIGHT...SUPPORTING CHANCES FOR FREEZING RAIN IN THE NORTH COUNTRY.
STRONG LOW PRESSURE WILL TRACK NORTHEAST OUT OF THE TENNESSEE AND
OHIO VALLEY SUNDAY AS THE FRONT SURGES NORTH INTO CANADA...
BRINGING LOCALLY HEAVY RAIN AND WARMER TEMPERATURES TO OUR REGION.
A COLD FRONT WILL TRACK THROUGH OUR AREA SUNDAY NIGHT AND MONDAY
MORNING BRINGING A RETURN TO COLDER WEATHER FOR THE BEGINNING OF
NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 930 AM EST...RADARS INDICATING SOME LIGHT SPOTTY RETURNS
ACROSS MAINLY OUR NORTHERN AREAS. THE HRRR LOOKS ON CUE...WITH
LIGHTLY PRECIPITATION LIKELY TO FILL IN AS THE AFTERNOON
ARRIVES...DUE TO INCREASED CONVERGENCE AND MOISTURE ALONG AN
APPROACHING BOUNDARY.
TEMPERATURES IN THE VALLEYS GENERALLY IN THE 30S ABOVE FREEZING.
HOWEVER...MESO SITES INDICATED TEMPERATURES INTO THE 40S ACROSS
MAINLY THE HIGHER ELEVATIONS OF CATSKILLS...BUT EVEN ABOVE FREEZING
ACROSS OUR SOUTHERN ADIRONDACKS. SNOW MELT HAS COMMENCE...AND MANY
AREAS WILL LIKELY NOT DROP BACK BELOW FREEZING UNTIL SUNDAY NIGHT.
NO REAL CHANGES WITH THIS PACKAGE...TWEAKED THE POPS (DOWNWARD A
LITTLE IN THE BEGINNING GRIDS) AND OF COURSE RE-TOOLED THE HOURLY
GRIDS. LOOK FOR LOTS OF CLOUDS TODAY...AND AN INCREASING CHANCE OF
MAINLY RAIN SHOWERS THIS AFTERNOON (WITH PERHAPS SOME POCKETS OF
FREEZING RAIN UP NORTH)...MAINLY ALBANY NORTH.
HIGH TEMPERATURES THIS AFTERNOON REACHING 45-50 SOUTH OF CAPITAL
DISTRICT...40-45 CAPITAL DISTRICT AND SURROUNDING PARTS. TO THE
NORTH...HIGHS WILL GENERALLY BE 35-40.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
ONE WEAK UPPER IMPULSE AND WEAK FORCING AFFECTS OUR REGION THIS
AFTERNOON AND TONIGHT. THE BEST COVERAGE OF PRECIPITATION TONIGHT
SHOULD BE NORTH OF THE MOHAWK VALLEY AND WEST OF THE LAKE GEORGE
SARATOGA REGION. HOWEVER...SOLID CHANCES FROM SCHOHARIE VALLEY
THROUGH THE CAPITAL DISTRICT...SOUTHERN VT INTO THE BERKSHIRES AND
EASTERN CATSKILLS. PRECIPITATION AMOUNTS SHOULD BE LIGHT...BUT
NIGHTTIME COOLING IN THE SOUTHERN ADIRONDACKS COULD ALLOW SOME OF
THE PRECIPITATION TO FALL AS FREEZING RAIN...MAYBE UP TO A TENTH
OF AN INCH. HOLDING OFF ON ANY ADVISORIES SINCE TEMPERATURES COULD BE
BORDERLINE AND NEXT SET OF GUIDANCE CAN BE CONSULTED AND STILL GET
LEAD TIME ON AN ADVISORY IF IT NEEDS TO BE ISSUED THIS
AFTERNOON...BUT AGAIN JUST FOR PARTS OF NORTHERN HERKIMER AND
HAMILTON COUNTIES. LOWS TONIGHT IN THE 30S.
STRONGER UPPER ENERGY...FORCING AND MOISTURE ADVECTION APPROACHES
SATURDAY AFTERNOON THROUGH SUNDAY AFTERNOON. RAIN SHOULD SPREAD
ACROSS THE REGION SATURDAY AFTERNOON AND NIGHT...AND BE HEAVY AT
TIMES SATURDAY NIGHT THROUGH SUNDAY. THERE ARE CONSIDERABLE
DISAGREEMENTS IN SOURCES OF GUIDANCE AND ENSEMBLES AS TO HOW MUCH
COLDER AIR SINKS SOUTH SATURDAY NIGHT IN RESPONSE TO ENHANCED UPPER
CONFLUENCE IN CANADA AS UPPER ENERGY TRACKS WELL NORTH OF THE U.S.
CANADIAN BORDER. BASED ON THE SOURCES OF GUIDANCE THAT RESOLVE
THESE ISSUES BEST...SIDING ON SOME COLD AIR DRAINING SOUTH IN
RESPONSE TO ENHANCED AGEOSTROPHIC NORTHERLY LOW LEVEL FLOW...
RESULTING IN SOME POTENTIAL FREEZING RAIN FOR THE SOUTHERN
ADIRONDACKS TO THE LAKE GEORGE AREA. WE WILL SEE HOW THE SNOW PACK
ACROSS THE ENTIRE REGION INFLUENCES SURFACE TEMPERATURES THROUGH
SATURDAY NIGHT AS WELL. WITH SUCH HIGH UNCERTAINTIES IN THE
RAIN/FREEZING RAIN LINE...NO HEADLINES YET UNTIL WE GET CLOSER TO
THE POTENTIAL EVENT. WHATEVER AREAS GET FREEZING RAIN COULD GET UP
TO A QUARTER INCH.
A VERY STRONG BOUNDARY LAYER JET SEGMENT AND ISENTROPIC LIFT...
ALONG WITH ANOMALOUSLY HIGH PWAT...SHOULD SUPPORT A HEAVY
RAIN EVENT...AND COMBINED WITH SNOW MELT...COULD RESULT IN SOME
FLOODING POTENTIAL. THIS WILL BE ADDRESSED IN THE HWO AS RAINFALL
FORECASTS FROM SOURCES OF GUIDANCE AND ENSEMBLES STILL A BROAD
RANGE AND AXIS OF HEAVIEST RAIN COULD FALL NORTH OF WHERE MAXIMUM
SNOW MELT OCCURS. A WEST TO SOUTHWEST BOUNDARY LAYER FLOW USUALLY
RESULTS IN THE HEAVIEST PRECIPITATION IN THE ADIRONDACKS...WHICH
AGAIN MAY SEE THE LEAST WARM TEMPERATURES AND LEAST SNOW MELT.
SO...STILL HOLDING OFF ON ANY FLOOD WATCHES.
HIGHS SATURDAY IN THE 40S TO AROUND 50...WITH LOWS SATURDAY NIGHT
AROUND 40 TO THE MID 40S...LOWER TO MID 30S IN THE NORTH COUNTRY.
HIGHS SUNDAY IN THE 50S MANY AREAS...BUT INTO THE 60S TOWARD POU
AND NW CT...AND IN THE 40S IN THE NORTH COUNTRY. THE COLD
FRONT TRACKS THROUGH THE REGION SUNDAY NIGHT AND SHOWERS SHOULD
CHANGE TO SNOW SHOWERS AS COLD AIR SPREADS ACROSS THE REGION.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
HAVE GENERALLY POPULATED THIS PORTION OF THE GRIDDED DATABASE WITH
00Z/20 HPC GUIDANCE.
MON-TUE...THE COLD FRONT ASSOCIATED WITH THIS WEEKEND/S STORM SYSTEM
SHOULD BE EXITING THE REGION MON AM...WITH RAIN SHOWERS TAPERING
OFF...BUT PROBABLY CHANGING TO SNOW SHOWERS BEFORE ENDING FOR AREAS
N AND W OF ALBANY. IN THE WAKE OF THE SFC FRONT...THE UPPER LEVEL
TROUGH WILL GRADUALLY TRANSLATE EASTWARD...PASSING ACROSS THE REGION
LATE MON NT OR ON TUE. THE COMBINATION OF THE ASSOCIATED COLD
POOL...AND COLDER AIR POURING ACROSS THE GREAT LAKES WILL LIKELY
LEAD TO AT LEAST SCATTERED SNOW SHOWERS AND FLURRIES FROM LATE
MONDAY INTO TUESDAY...ALONG WITH THE POSSIBILITY OF SOME LAKE EFFECT
SNOWBANDS SOMEWHERE ACROSS THE WESTERN ADIRONDACKS AND/OR MOHAWK
VALLEY...WHICH COULD OCCASIONALLY EXTEND INTO THE CAPITAL REGION AND
BERKSHIRES/SOUTHERN GREEN MTNS. AS FOR TEMPS...EXPECT MAXES TO REACH
THE 30S TO LOWER 40S MON IN VALLEY AREAS...AND 20S TO LOWER 30S
ACROSS HIGHER ELEVATIONS...WITH MOST MAX TEMPS LIKELY OCCURRING IN
THE MORNING WITH FALLING AFTERNOON TEMPS. FOR MON NT...EXPECT TEMPS
TO FALL INTO THE SINGLE DIGITS AND TEENS ACROSS NORTHERN AREAS...AND
TEENS AND LOWER/MID 20S FOR CENTRAL AND SOUTHERN AREAS. ON
TUE...EXPECT MAX TEMPS TO ONLY REACH THE SINGLE DIGITS AND LOWER
TEENS ACROSS MUCH OF THE SOUTHERN ADIRONDACKS...WITH MAINLY 20S FOR
VALLEY AREAS.
TUE NT-WED NT...HIGH PRESSURE WILL THEN BUILD IN FOR TUE
NT-WED...WHILE A WEAK CLIPPER TYPE SYSTEM PASSES BY TO OUR N AND W
WED NT. HAVE INCLUDED SOME SLIGHT CHC POPS FOR WED NT ACROSS
PORTIONS OF THE WESTERN ADIRONDACKS. AS FOR TEMPS...EXPECT TUE
NT/WED AM MINS TO FALL INTO THE SINGLE DIGITS AND TEENS IN MOST
AREAS...WITH SOME READINGS POSSIBLY FALLING TO BETWEEN ZERO AND 5
BELOW ACROSS PORTIONS OF THE SOUTHERN ADIRONDACKS. ON WED...EXPECT
MAX TEMPS TO REACH 25-30 IN VALLEY AREAS...AND UPPER TEENS TO LOWER
20S ACROSS HIGHER ELEVATIONS. FOR WED NT/THU AM...EXPECT MINS TO
FALL INTO THE TEENS AND 20S IN MOST AREAS.
THU...THE 00Z/20 ECMWF CONTINUES TO HINT AT A WEAK COASTAL SYSTEM
OFF THE SE COAST POTENTIALLY PHASING WITH SOME ENERGY ACROSS THE
GREAT LAKES TO ALLOW FOR LIGHT PRECIPITATION TO DEVELOP ACROSS THE
REGION. ALTHOUGH THE DETERMINISTIC 00Z/20 GFS IS NOT QUITE AS
EMPHATIC WITH THIS PHASING...SOME MEMBERS OF THE 00Z/20 GEFS DO
INDEED DEPICT SOME FORM OF THIS...WITH SOME SIGNAL NOTED IN THE MEAN
GEFS. WILL THEREFORE INDICATE CHC POPS...MAINLY FOR SNOW ON
THU...WITH PERHAPS A RAIN/SNOW MIX FOR SOUTHERN AREAS. AS FOR
TEMPS...HAVE INDICATED MAXES REACHING THE 35-40 IN MOST
VALLEYS...AND 25-30 FOR HIGHER ELEVATIONS.
&&
.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
MAINLY VFR LEVEL CLOUDS PERSIST ACROSS THE REGION...WITH BASES OF
3500-6000 FT AGL CONFINED MAINLY TO KGFL/KALB...WITH MUCH HIGHER
CIGS FURTHER SOUTH AND EAST. SOME SPRINKLES MAY OCCUR NEAR OR
NORTH OF KGFL OVER THE NEXT 2 HOURS.
THROUGH THE DAY...SKIES SHOULD REMAIN MOSTLY CLOUDY...BUT
INITIALLY CIGS SHOULD REMAIN VFR. HOWEVER...SOME AREAS OF LIGHT
RAIN SHOWERS WILL DEVELOP AROUND MIDDAY FOR KGFL/KPSF/KALB...WITH
CIGS GRADUALLY LOWERING INTO THE MVFR RANGE IN THESE AREAS. THE
SHOWERS SHOULD REMAIN NORTH OF KPOU...WHERE VFR CONDITIONS SHOULD
CONTINUE THROUGH THE DAY.
OCCASIONAL LIGHT RAIN OR DRIZZLE WILL CONTINUE OVERNIGHT FOR
KGFL/KALB AND KPSF...WHILE REMAINING GENERALLY NORTH OF KPOU.
CIGS/VSBYS WILL CONTINUE TO BE MAINLY MVFR AT
KGFL/KALB/KPSF...WITH SOME OCCASIONAL IFR CONDITIONS
POSSIBLE...ESP AFTER 05Z/SAT. AT KPOU...THE VSBY MAY LOWER INTO
THE MVFR RANGE LATER TONIGHT.
WINDS WILL BE SOUTHERLY LESS THAN 10 KT THROUGH 12Z SATURDAY.
OUTLOOK...
SATURDAY NIGHT: HIGH OPERATIONAL IMPACT. DEFINITE RA.
SUNDAY: HIGH OPERATIONAL IMPACT. LIKELY RA.
SUNDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA.
MONDAY: MODERATE OPERATIONAL IMPACT. SLIGHT CHANCE OF SHRA...SHSN.
MONDAY NIGHT: MODERATE OPERATIONAL IMPACT. SCATTERED SHSN.
TUESDAY: LOW OPERATIONAL IMPACT.BREEZY ISOLATED SHSN.
TUESDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
CHRISTMAS DAY: NO OPERATIONAL IMPACT. NO SIG WX.
&&
.HYDROLOGY...
WARMER TEMPERATURES WILL HAPPEN FRIDAY INTO THE WEEKEND...WITH A
FRONTAL BOUNDARY BRINGING SOME SHOWERS AND MIXED PRECIPITATION TO
CLOSE THE WORK WEEK. SOME SNOW MELT IS LIKELY BY THIS WEEKEND.
ALSO...A STORM SYSTEM MOVING ALONG A FRONTAL BOUNDARY MAY BRING
SIGNIFICANT PCPN TO THE FORECAST AREA SAT NIGHT INTO SUNDAY WITH
EVEN MILDER TEMPS.
TEMPERATURES SUNDAY ARE EXPECTED TO WARM INTO THE 50S OR POSSIBLY
EVEN 60S ACROSS THE EASTERN CATSKILLS...MID HUDSON VALLEY...CENTRAL
AND SOUTHERN TACONICS INTO THE BERKSHIRES AND ACROSS LITCHFIELD
COUNTY WITH 50S ACROSS THE CAPITAL REGION...40S FURTHER NORTH.
BETWEEN THE RAIN AND RUNOFF FROM SNOWMELT DUE TO THE MILD/WARM
TEMPERATURES SOME FLOODING COULD BE A PROBLEM INCLUDING ICE JAMS
ISSUES. AT THIS POINT...WE BELIEVE MOST IF NOT ALL OF THE SNOW COULD
BE MELTED FROM ABOUT THE MOHAWK RIVER...FURTHER NORTH TEMPERATURES
MIGHT NOT BE WARM ENOUGH TO MELT ALL OF THE SNOW.
THE POTENTIAL IS THERE FOR 1-2 INCHES OF RAINFALL FROM ALBANY
NORTHWARD...POSSIBLY SOME AREAS REACHING 3 INCHES. LESS AMOUNTS OF
RAIN LOOK TO FALL SOUTH OF THE CAPITAL REGION...AN INCH OR LESS.
WILL KEEP MENTION OF IN OUR HAZARDOUS WEATHER OUTLOOK.
FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED
AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
MA...NONE.
VT...NONE.
&&
$$
SYNOPSIS...HWJIV/NAS
NEAR TERM...HWJIV
SHORT TERM...NAS
LONG TERM...KL
AVIATION...KL
HYDROLOGY...NAS
AREA FORECAST DISCUSSION
NWS TAMPA BAY RUSKIN FL
935 AM EST FRI DEC 20 2013
.UPDATE (REST OF TODAY THROUGH SATURDAY)...
14Z WATER VAPOR AND H4 RAP ANALYSIS SHOWS AN AMPLIFYING UPPER LEVEL
PATTERN OVER THE CONUS. LONGWAVE TROUGHING NOW COVERS THE NATION TO
THE WEST OF THE CONTINENTAL DIVIDE...AND IS HIGHLIGHTED BY A POTENT
SHORTWAVE/CLOSED LOW FEATURE EJECTING EASTWARD OVER THE SW STATES
AND NORTHERN MEXICO. THE ADVANCEMENT OF THIS WESTERN TROUGH AND
ASSOCIATED HEIGHT FALLS HAVE HELPED TO "RIDGE UP" THE DOWNSTREAM
FLOW FROM THE EASTERN GULF OF MEXICO TO THE MID-ATLANTIC STATES.
THIS RIDGE OVER OUR HEADS WILL BE OUR PROTECTOR THROUGH THE UPCOMING
WEEKEND AND PROVIDE A GENERALLY FAIR AND UNSEASONABLY WARM FORECAST.
WV IMAGERY SHOWS SOUTHERN STREAM MOISTURE RAPIDLY ADVECTING
NORTHWARD ACROSS THE SOUTHERN PLAINS AHEAD OF THE STRONG SOUTHWEST
SHORTWAVE. THIS MOISTURE RETURN IS THE FIRST STAGE IN THE PRIMING OF
THE ATMOSPHERE FOR A POTENTIALLY SIGNIFICANT SEVERE WEATHER OUTBREAK
ACROSS THE LOWER MS VALLEY DURING SATURDAY. HOWEVER...AS MENTIONED
ABOVE THIS INCLEMENT WEATHER IS NOT IN OUR FORECAST WITH THE UPPER
RIDGE IN PLACE. 20/12Z KTBW SOUNDING...ALTHOUGH STILL ON THE DRY
SIDE...SHOWS THAT WE HAVE SEEN SOME MOISTURE RETURN THROUGH THE
COLUMN DURING THE PAST 24 HOURS...WITH THE PW VALUE JUMPING FROM
0.27" ON THURSDAY MORNING TO AROUND AN INCH THIS MORNING. MUCH OF
THIS MOISTURE RETURN HAS BEEN IN THE LOWER LEVELS BELOW A WELL
DEFINED SUBSIDENCE INVERSION (ASSOCIATED WITH THE UPPER RIDGING)
JUST ABOVE 700MB.
AT THE SURFACE...HIGH PRESSURE RIDGES BACK FROM THE WESTERN ATLANTIC
TO THE GA/CAROLINA COAST...PLACING OUR REGION WITHIN A LIGHT
SOUTHEAST FLOW REGIME. THIS FLOW HAS BEEN ADVECTING INCREASING
LEVELS OF BOUNDARY LAYER MOISTURE ACROSS THE PENINSULA AND THESE
MOISTURE LEVELS WILL ONLY CONTINUE TO INCREASE THROUGH THE NEXT 24
HOURS. TEMPERATURES ARE ALREADY RISING QUICKLY THROUGH THE 60S
TOWARD ABOVE NORMAL AFTERNOON TEMPERATURES.
REST OF TODAY...
SUNNY/MOSTLY SUNNY SKIES THIS MORNING WILL GIVE WAY TO A MIX OF SUN
AND CLOUDS UNDER A DEVELOPING SCT-BKN CUMULUS FIELD FOR THE
AFTERNOON. EFFICIENT DIURNAL MIXING AND A WARM POTENTIAL WITH 850MB
TEMPS OF 13-15C WILL ALLOW HIGH TEMPS TO REACH THE MID/UPPER 70S
ACROSS THE NORTHERN NATURE COAST...TO THE LOWER 80S AROUND THE I-4
CORRIDOR...AND LOWER TO MIDDLE 80S DOWN TOWARD FORT MYERS. THE
ENHANCED TERRESTRIAL HEATING AND A GENERALLY WEAK GRADIENT SHOULD
ALLOW FOR A FEEBLE SEA-BREEZE CIRCULATION TO TURN WINDS ONSHORE AT
THE BEACHES DURING THE AFTERNOON. WHILE NOT ANTICIPATING MUCH
ACTIVITY...THE WARM TEMPS AND MOISTURE RETURN ARE SHOWN TO RESULT IN
SEVERAL HUNDRED J/KG OF CAPE THIS AFTERNOON FROM THE TAMPA BAY AREA
SOUTHWARD. THIS INSTABILITY COMBINED WITH SOME ENHANCED FOCUS ALONG
ANY SEA-BREEZE MAY BE JUST ENOUGH TO FORCE A FEW ISOLATED SHOWERS.
ANY SHOWERS WILL BE BRIEF AND HAVE VERY LIMITED IMPACTS TO
OUTDOOR ACTIVITIES...BUT HAVE KEPT THE 20% POP FOR THIS
POSSIBILITY. LOOKING AT THE KTBW SOUNDING PROFILE...ANY SHOWERS WILL
ALSO BE SHALLOW IN NATURE...HELD IN CHECK BY THE STRONG SUBSIDENCE
INVERSION ABOVE 12-15KFT.
TONIGHT...A WARM AND FAIR OVERNIGHT PERIOD. THE CONTINUED MOISTURE
ADVECTION WITHIN THE LIGHT SE FLOW REGIME WILL PREVENT LOW TEMPS
FROM DROPPING OUT OF THE 60S FOR JUST ABOUT ALL AREAS. BOUNDARY
LAYER MOISTURE UNDERNEATH THE SUPPRESSION ALOFT DOES SET UP A
FAVORABLE SCENARIO FOR PATCHY/AREAS OF FOG DURING THE LATE NIGHT
HOURS. A WIDESPREAD DENSE FOG EVENT IS UNLIKELY...BUT LOCALIZED
AREAS OF REDUCED VISIBILITY ARE A GOOD BET FOR ANYONE DOING EARLY
TRAVELING SATURDAY MORNING. BOTH STATISTICAL MOS AND ENSEMBLE SREF
PROBS SUGGEST THIS FOG POTENTIAL.
SATURDAY...UNSEASONABLY WARM TEMPERATURES TO START OUT THE WEEKEND
UNDER AN UPPER RIDGE CHARACTERIZED BY H5 HEIGHTS OF 1.5-2 STANDARD
DEVIATIONS ABOVE CLIMO. GRADIENT WILL INCREASE SOMEWHAT AND SHOULD
HELP PREVENT MUCH IF ANY SEABREEZE DEVELOPMENT...OR AT LEAST INLAND
PENETRATION DESPITE THE STRONG TERRESTRIAL HEATING. THEREFORE...HAVE
A RAIN FREE DAY IN THE FORECAST. THE STRONGER GRADIENT WILL RESULT
IN EVEN MORE EFFICIENT DIURNAL MIXING WITHIN A VERY WARM POTENTIAL
COLUMN WITH 850MB TEMPS AROUND 16C. THESE 850MB TEMPS ARE ALSO 1.5-2
STANDARD DEVIATIONS ABOVE CLIMO. COMBINE ALL THIS AND WE ARE LOOKING
AT NEAR RECORD TEMPERATURES FOR THE WINTER SOLSTICE...WITH LOWER 80S
FAR NORTH AND WIDESPREAD MIDDLE 80S ELSEWHERE. BELOW IS A SELECT
LISTING OF SOME OF THE RECORD TEMPERATURES FOR DEC 21ST ACROSS THE
AREA:
BROOKSVILLE...86
FORT MYERS....87
LAKELAND......82
SARASOTA......86
PUNTA GORDA...84
ST PETERSBURG.82
TAMPA INTL....85
WINTER HAVEN..85
HAVE A GREAT FRIDAY AND BEGINNING TO THE WEEKEND! STAY COOL!
&&
.AVIATION...
20/12Z-21/12Z...PREVAILING VFR TODAY WITH FEW-SCT LOW AND MID
CLOUDS.ISOLD SHRA THIS AFTERNOON BUT WITH LOW ODDS OF IMPACTING THE
TERMINALS. LIGHT EAST WINDS BECOME SE AND INCREASE IN THE AFTERNOON.
A DEVELOPING WEATHER SYSTEM OVER THE SW U.S. WILL INCREASE LOW-LEVEL
MOISTURE THROUGH THE PERIOD WITH MVFR CONDITIONS TOWARD SUNRISE SAT.
&&
.MARINE...
WINDS WILL REMAIN OUT OF THE SOUTHEAST THROUGH THE WEEKEND WITH
SPEEDS REACHING EXERCISE CAUTION LEVELS STARTING LATER TONIGHT. A
COLD FRONT WILL APPROACH THE WATERS LATE IN THE WEEKEND INTO EARLY
NEXT WEEK WITH WINDS TURNING TO THE NORTHWEST AND SPEEDS INCREASING
AGAIN EARLY TO MID WEEK.
&&
.PRELIMINARY POINT TEMPS/POPS...
TPA 81 68 84 68 / 20 10 10 10
FMY 84 66 86 68 / 20 10 10 10
GIF 82 64 84 65 / 10 10 10 10
SRQ 82 67 84 67 / 20 10 10 10
BKV 82 61 85 62 / 20 10 10 10
SPG 79 67 81 68 / 20 10 10 10
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GULF WATERS...NONE.
&&
$$
UPDATE...MROCZKA
AVIATION...RUDE
AREA FORECAST DISCUSSION
NWS COLUMBIA SC
608 AM EST FRI DEC 20 2013
.SYNOPSIS...
HIGH PRESSURE CENTERED OFF THE COAST WILL RIDGE INTO THE
SOUTHEASTERN STATES THROUGH SATURDAY. SOUTHERLY FLOW ON THE
BACKSIDE OF THE HIGH WILL BRING WARM TEMPERATURES TO THE FORECAST
AREA. A COLD FRONT WILL SLOWLY MOVE THROUGH OUR REGION SUNDAY
NIGHT INTO MONDAY. COOL AND DRY HIGH PRESSURE WILL RETURN TUESDAY
AND WEDNESDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
MOISTURE HAS INCREASED IN THE SOUTHERLY FLOW ON THE BACKSIDE OF
THE OFFSHORE HIGH. THIS SHALLOW MOISTURE PLUS NOCTURNAL COOLING
HAS RESULTED IN STRATUS AND FOG MAINLY IN SOUTHERN AND EASTERN
SECTIONS. STRATUS HAS BEEN MORE DOMINATE BECAUSE OF SIGNIFICANT
BOUNDARY-LAYER WIND. HEATING AND MIXING SHOULD HELP DIMINISH THE
LOWER CLOUDINESS LATER THIS MORNING. THE HRRR INDICATES THIS WILL
HAPPEN BETWEEN 1000 AM AND 1100 AM. SATELLITE TRENDS INDICATE
UPPER-LEVEL CLOUDINESS WILL CONTINUE TO STREAM INTO THE AREA...BUT
THIS CLOUDINESS SHOULD GENERALLY BE THIN ENOUGH FOR PARTLY SUNNY
SKIES. WE USED THE GUIDANCE CONSENSUS FOR THE HIGH TEMPERATURE
FORECAST.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
HIGH PRESSURE OFF THE COAST WILL CONTINUE TO CIRCULATE A SOUTHERLY
FLOW INTO THE FORECAST AREA AHEAD OF A SLOW MOVING COLD FRONT.
EXPECT WIDESPREAD STRATUS WILL DEVELOP TONIGHT BECAUSE OF HIGH LOW-
LEVEL MOISTURE AND NOCTURNAL COOLING. THIS CLOUDINESS SHOULD
CONTINUE THROUGH MUCH OF SATURDAY MORNING...BUT HEATING AND MIXING
SHOULD DIMINISH THE CLOUDINESS LATE IN THE MORNING OR EARLY IN
THE AFTERNOON. MUCH OF THE FORCING ASSOCIATED WITH THE
APPROACHING COLD FRONT WILL REMAIN WEST OF THE FORECAST AREA
THROUGH SATURDAY NIGHT BUT THE MOISTURE MAY BECOME DEEP ENOUGH FOR
SHOWERS BY SATURDAY NIGHT. WE FORECASTED JUST CHANCE POPS. ABOVE
NORMAL TEMPERATURES WILL OCCUR IN THE WARM SECTOR AHEAD OF THE
FRONT. WE USED THE GUIDANCE CONSENSUS FOR THE HIGH TEMPERATURE
FORECAST. THE TIMING OF DIMINISHING STRATUS SATURDAY ADDS UNCERTAINTY
TO THE TEMPERATURE FORECAST.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
THE WARM PATTERN AHEAD OF THE COLD FRONT WILL CONTINUE SUNDAY.
HIGH PRESSURE WELL OFF THE EAST COAST WILL CIRCULATE INCREASING
MOISTURE INTO THE FORECAST AREA FROM THE ATLANTIC AND GULF OF
MEXICO. MUCH OF THE FORCING ASSOCIATED WITH THE APPROACHING COLD
FRONT WILL STILL BE WEST OF THE AREA SO WE FORECASTED JUST CHANCE
POPS SUNDAY. THE GREATER SHOWER CHANCE SHOULD BE SUNDAY NIGHT AND
MONDAY MAINLY BECAUSE OF CONVERGENCE ALONG THE FRONT PLUS LIFT
ASSOCIATED WITH THE RIGHT ENTRANCE REGION OF THE H25 JET. THERE
MAY BE ENOUGH INSTABILITY FOR A FEW THUNDERSTORMS LATE SUNDAY AND
SUNDAY NIGHT. SHEAR WILL BE HIGH BUT INSTABILITY WEAK LIMITING THE
SEVERE THUNDERSTORM THREAT. THE GFS AND ECMWF SHOW DRY RIDGING
BEHIND THE FRONT DOMINATING TUESDAY AND WEDNESDAY. THE MODELS SHOW
A TROUGH OFF THE COAST THURSDAY SUPPORTING A SMALL RAIN CHANCE.
VERY WARM TEMPERATURES WILL OCCUR AHEAD OF THE FRONT SUNDAY WITH
MORE SEASONABLE TEMPERATURES DURING THE REST OF THE MEDIUM-RANGE
PERIOD. THE GFS...ECWMF...AND EKD MOS SUPPORT HIGHS NEAR 80 AHEAD
OF THE FRONT SUNDAY. THE GFS ENSEMBLES HAD A HIGH SPREAD WITH THE
MEAN MAINLY IN THE LOWER 70S. WE LEANED TOWARD THE WARMER
GUIDANCE...BUT THE EXTENT OF STRATUS ADDS UNCERTAINTY TO THE
TEMPERATURE FORECAST.
&&
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
MOISTURE HAS INCREASED IN THE SOUTHERLY FLOW ON THE BACKSIDE OF
THE OFFSHORE HIGH. THIS SHALLOW MOISTURE PLUS NOCTURNAL COOLING
HAS RESULTED IN MVFR STRATUS AND FOG MAINLY IN SOUTHERN AND
EASTERN SECTIONS. STRATUS HAS BEEN MORE DOMINATE BECAUSE OF
SIGNIFICANT BOUNDARY-LAYER WIND. HEATING AND MIXING SHOULD HELP
DIMINISH THE LOWER CLOUDINESS LATER THIS MORNING. THE HRRR
INDICATES THIS WILL HAPPEN BETWEEN 1000 AM AND 1100 AM AND VFR
CONDITIONS SHOULD OCCUR DURING THE AFTERNOON INTO THE EVENING.
HOWEVER...HIGH LOW-LEVEL MOISTURE IN THE SOUTHERLY FLOW AND
NOCTURNAL COOLING WILL BRING MVFR OR IFR STRATUS OR FOG LATE
TONIGHT.
EXTENDED AVIATION OUTLOOK...HIGH CONFIDENCE FOR CEILING AND VISIBILITY
RESTRICTIONS THROUGH MONDAY ASSOCIATED WITH THE SLOW MOVING COLD
FRONT.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
814 AM CST FRI DEC 20 2013
.DISCUSSION...
805 AM CST
HAVE EXPANDED THE DENSE FOG ADVISORY TO INCLUDE AREAS SOUTH OF A
PONTIAC TO VALPARAISO LINE. HAVE RECEIVED MULTIPLE REPORTS OF
DENSE FOG ALONG THE SYNOPTIC BOUNDARY...WHICH IS PRACTICALLY
STATIONARY AS THE 1006MB SFC LOW NEAR QUINCY EASES ITS WAY
NORTHEAST. GOOD POOLING OF MOISTURE AND LIGHT WINDS ALONG THIS
SHOULD CONTINUE TO ALLOW FOR DENSE FOG THROUGH 12P-3P...UNTIL THE
LOW LIFTS THROUGH THE AREA. THE RAP AND HRRR FOR THE MOST PART
SUPPORT THIS REASONING.
TEMPERATURES NORTH OF THE BOUNDARY ARE HOLDING FAIRLY STEADY...OR
EASING DOWN EVER SO GRADUALLY. THE FREEZING RAIN ADVISORY AREA
LOOKS GOOD THOUGH AND MATCHES THE 32 DEGREE ISOTHERM AT THE
SURFACE AND REPORTS WE HAVE RECEIVED...SO NO CHANGES PLANNED
THERE. STILL A CHANCE SOME LIGHT FREEZING PRECIP INCHES ITS WAY
SOUTH OF THE ADVISORY LATE THIS MORNING OR AFTERNOON...INCLUDING
INTO NORTHERN COOK AND DUPAGE COUNTIES.
MTF
&&
.PREV DISCUSSION...
355 AM CST
SEVERAL ISSUES ONGOING THIS MORNING AS WELL THROUGH THE
WEEKEND...WITH DENSE FOG AND FREEZING RAIN ISSUES THIS MORNING
WITH THE FREEZING RAIN NOW LINGERING INTO THE AFTERNOON AND
POSSIBLY TONIGHT...CONTINUED FLOODING CONCERNS...AND LASTLY
POTENTIAL SNOWFALL WHICH THE AXIS OF HEAVIEST SNOW STILL APPEARS
TO BE ACROSS THE NORTH AND NORTHWEST AREAS OF THE CWA.
ADDRESSING THE MORE IMPORTANT ISSUES IN THE NEAR TERM...LIGHT
FREEZING RAIN OR FREEZING DRIZZLE CONTINUES ACROSS THE ADVISORY
AREA THIS MORNING...WITH LIGHT RAIN OR DRIZZLE ONGOING FOR THE
REMAINDER OF THE CWA. BROAD SOUTHWESTERLY FLOW ALOFT CONTINUES TO
USHER SEVERAL WAVES OF ENERGY...WITH ELONGATED TROUGH OF LOW
PRESSURE EXTENDING FROM THE CENTRAL PLAINS UP THROUGH SOUTHERN
GREAT LAKES. AS THESE WAVES OF ENERGY/SPEED MAXES LIFT NORTHEAST
ACROSS THE REGION THIS MORNING...EXPECT THIS TROUGH OF LOW
PRESSURE TO LIFT EAST NORTHEAST TO CENTRAL ILLINOIS AND NORTHWEST
INDIANA THROUGH THE EARLY AFTERNOON. PRESENT LOW/MID LEVEL
CONVERGENCE WILL CONTINUE TO BE A PERSISTENT THROUGH THIS
PERIOD...WITH CURRENT UPSTREAM WAVE TO AID IN TIGHTENING LOW/MID
LEVEL BAROCLINIC ZONE. THIS WILL ENHANCE FRONTOGENETIC FORCING
ACROSS THE ADVISORY AREA...ALL AIDING IN CONTINUED PRECIP
DEVELOPMENT AT LEAST THROUGH EARLY AFTERNOON FOR THE ENTIRE CWA.
HAVE INCREASED POPS THIS MORNING AND EARLY AFTERNOON...BUT WONDER
IF AFTERNOON POPS WILL NEED TO BE RAISED EVEN FURTHER WITH SHORT
TERM GUIDANCE HINTING AT CONTINUED TO DEVELOPMENT EVEN INTO THE
LATE AFTERNOON. ALTHOUGH CURRENT ASSOCIATED BOUNDARY DRAPED ACROSS
EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA DID MAKE SOME
NORTHWARD PROGRESSION EARLY THIS MORNING...FEEL THAT THIS
NORTHWARD MOVEMENT HAS ENDED AND WILL REMAIN SITUATED UNTIL
DROPPING SOUTH/SOUTHEAST OF THE CWA THIS AFTERNOON. GUIDANCE
HINTING AT SOME WEAK CAA TO BEGIN OCCURRING OVER THE NEXT SEVERAL
HOURS AND WITH LATEST RAP ANALYSIS ALREADY INDICATING THIS ACROSS
WESTERN ILLINOIS...FEEL PRETTY CONFIDENT WITH THIS TREND. THIS
WILL HELP TEMPS IN THE ADVISORY AREA TO HOVER JUST BELOW OR AT THE
FREEZING MARK THROUGH MOST OF TODAY. WITH THIS CONTINUED PRECIP
AND TEMP TRENDS...HAVE DECIDED TO EXTEND THE FREEZING RAIN
ADVISORY THROUGH THE AFTERNOON AND HAVE ALSO INCLUDED KANE COUNTY
IN THE ADVISORY AS WELL. WILL NEED TO ALSO MONITOR THE AFTERNOON
PERIOD FOR THE REMAINING CWA...AS COLD ADVECTION SHOULD HELP TEMPS
LOWER AROUND FREEZING INTO THE LATE AFTERNOON PERIOD. WITH PRECIP
POSSIBLY LINGERING...COULD SEE SOME POSSIBLE LIGHT ICING IN AREAS
OUTSIDE OF THE ADVISORY. ALTHOUGH TEMPS SHOULD BE MARGINAL...AND
AM NOT OVERLY CONCERNED AT THIS TIME.
WITH REGARDS TO THE DENSE FOG...WITH INCREASING MOISTURE IN THE
BOUNDARY LAYER THIS PAST EVENING DENSE FOG DEVELOPED ALONG TO THE
NORTH OF THIS BOUNDARY. MANY REPORTS OF DENSE FOR WERE RECEIVED
THIS PAST EVENING ACROSS NORTHWEST INDIANA...PRIMARILY FOR LAKE
AND PORTER COUNTIES IN INDIANA. WITH THE BOUNDARY SITUATED AND
EXPECTED TO REMAIN THIS WAY THROUGH THE REMAINDER OF THE
MORNING...FEEL CURRENT DENSE FOG ADVISORY FOR THESE LOCATIONS
REMAINS VALID. ALTHOUGH...SOUTHERN AREAS OF COOK COUNTY AND
EASTERN AREAS OF WILL COUNTY WILL NEED TO BE MONITORED OVER THE
NEXT COUPLE OF HOURS AS VIS IN THESE LOCATIONS CONTINUES TO BOUNCE
AROUND 1/2 MILE. END TIMING FOR THIS DENSE FOG ADVISORY REMAINS 9
AM CST...AND SEEMS REASONABLE. THIS SAGGING BOUNDARY AND SLIGHTLY
DRIER AIR SHOULD HELP WITH THE MORE DENSE FOG...BUT WITH PATCHY
DENSE FOG STILL NOT OUT OF THE QUESTION AT LEAST THROUGH MID DAY.
CONFIDENCE WITH THIS FOG REMAINS LOW AT THIS TIME AND WILL NEED TO
MONITOR...POSSIBLY EXTENDING THIS ADVISORY OR MAYBE EVEN EXPANDING
IT LATER THIS MORNING.
WITH SURFACE LOW EXITING TO THE EAST THIS EVENING AND THE ARRIVAL
OF DRIER AIR...SHOULD OBSERVE OVERALL PRECIP CHANCES TO WIND DOWN
FOR THE TIME BEING. ALTHOUGH WITH GUIDANCE CONTINUING TO INDICATE
BROAD SCALE LIFT WITH THE APPROACHING LONGWAVE TROUGH TO THE WEST
IT DOES APPEAR AS IF AREAS ACROSS THE SOUTHERN CWA COULD SEE
ADDITIONAL PRECIP TONIGHT. ALTHOUGH LIGHT PRECIP...THERMAL
PROFILES WOULD INDICATE THAT THIS PRECIP WOULD BE IN THE FORM OF
LIGHT FREEZING RAIN OR LIGHT FREEZING DRIZZLE. ANOTHER PERIOD I AM
CONCERNED ABOUT AT THIS TIME IS LATE TONIGHT INTO EARLY SATURDAY
MORNING...ONCE AGAIN FOR AREAS ACROSS THE SOUTHERN CWA. WILL NEED
TO MONITOR SURFACE TEMP TRENDS ACROSS EAST CENTRAL ILLINOIS DURING
THIS TIME...WITH FREEZING RAIN ONCE AGAIN POSSIBLY BEING AN ISSUE.
EXPANDING PRECIP TO THE SOUTH IS EXPECTED TO INCH FURTHER NORTH
TOWARDS THE SOUTHERN CWA TOWARDS THE 12Z SATURDAY TIME
FRAME...WITH SOUTHWEST FLOW ALOFT PERSISTING OUT AHEAD OF THE
APPROACHING LONGWAVE TROUGH. WITH A SLOW TEMP TREND EXPECTED
SATURDAY MORNING...A PERIOD OF LIGHT FREEZING RAIN COULD CAUSE
SOME ISSUES PRIMARILY SOUTH OF I-80.
WITH REGARDS TO WINTER STORM SATURDAY THROUGH SUNDAY...LATEST
THINKING/UPDATES TO FORECAST CONTINUE TO SUPPORT CURRENT WINTER
STORM WATCH ACROSS NORTHERN PORTIONS OF THE CWA. EXPECTED VARYING
PRECIP TYPES INCLUDING ALMOST ALL WINTER PRECIP TYPES COULD BE
OBSERVED SATURDAY INTO SATURDAY NIGHT...WITH A VARYING THERMAL
PROFILE EXPECTED TO CHANGE THROUGH THE PERIOD FOR ALL AREAS. WILL
NEED TO MONITOR THE SATURDAY MORNING TIME FRAME INTO THE DAY
SATURDAY FOR THE VARYING PRECIP TYPE...POSSIBLY ADDING YET ANOTHER
HEADLINE TO ACCOMMODATE FOR THE WINTRY MIX. EXPECTED SURFACE LOW
TRACK STILL SUPPORTIVE FOR BEST CHANCES FOR SNOW OR ALL SNOW
ACROSS NORTHWEST AND NORTH CENTRAL ILLINOIS WITH SNOWFALL TOTALS
IN EXCESS OF 6 INCHES STILL APPEARING POSSIBLE. THE EXPECTED RAIN
SNOW LINE HAS VARIED SLIGHTLY...BUT THE GENERAL IDEA REMAINING THE
SAME. OHARE TO PERU ILLINOIS LINE ARE THE DIVIDING LINE AT THIS
TIME...WITH CURRENT SNOW FORECAST INDICATING RAPID INCREASE IN
SNOW AMOUNTS RIGHT TO THE NORTH OF THIS LINE AND WITH AREAS TO THE
SOUTH OBSERVING LIGHT SNOW ACCUMULATIONS.
ALTHOUGH LATEST TRENDS ARE INDICATING THAT THE AXIS OF HEAVIEST
RAINFALL IS BEGINNING TO SHIFT SOUTH OF THE CWA...DECENT RAINFALL
AMOUNTS OF UP TO AN INCH STILL SUPPORT THE POSSIBILITY OF
FLOODING...AND HAVE MADE NO CHANGES TO THE CURRENT FLOOD WATCH.
RODRIGUEZ
MEDIUM AND LONG RANGE...MONDAY THROUGH THURSDAY...
MAIN CONCERNS BEYOND THIS WEEKEND ARE THE RETURN OF ARCTIC AIR AND
MUCH COLDER TEMPERATURES MONDAY-TUESDAY...AND THE POTENTIAL FOR A
LITTLE LIGHT SNOW CHRISTMAS EVE-CHRISTMAS DAY.
DEEP UPPER TROUGH TRAVERSING THE REGION MONDAY WITH FAIRLY
IMPRESSIVE SHORT WAVE ENERGY PASSING OVERHEAD. FORECAST SOUNDINGS
INDICATE SATURATION IN LOW LEVELS...WITH TEMPS NEAR -15C AS BOUNDARY
LAYER COOLS IN BLUSTERY COLD ADVECTION BEHIND DEPARTING WEEKEND LOW
PRESSURE SYSTEM. THIS SHOULD SUPPORT FLURRIES/LIGHT SNOW SHOWERS
ACROSS THE CWA INTO THE AFTERNOON HOURS. OF MORE IMPORTANCE THAN THE
POTENTIAL FOR LIGHT SNOW SHOWERS OR FLURRIES HOWEVER WILL BE THE
MUCH COLDER TEMPS AND WIND CHILLS AS ARCTIC AIR PLUNGES BACK INTO
THE REGION. TEMPS AT H8 FALL TO AROUND -16 C BY LATE AFTERNOON WITH
H9 TEMPS NEARLY SO...SUGGESTING SURFACE TEMPS MAY STRUGGLE TO RISE
ABOVE 10-15F AND WILL LIKELY FALL INTO THE SINGLE DIGITS ACROSS
NORTH CENTRAL IL AND WIND CHILLS IN THE NEGATIVE SINGLE DIGITS.
SURFACE HIGH PRESSURE RIDGE WILL BUILD ACROSS THE MISSISSIPPI VALLEY
AND INTO IL MONDAY NIGHT IN RESPONSE TO SUBSIDENCE BEHIND THE
DEPARTING UPPER TROUGH...WITH CLEARING SKIES...NEW SNOW COVER
ESPECIALLY FAR NORTHERN IL...AND DECREASING WINDS EXPECTED TO RESULT
IN STRONG RADIATIONAL COOLING. BOTH GFS AND ECMWF MOS DEPICT
SUB-ZERO LOWS ACROSS MUCH OF NORTHERN IL BY SUNRISE TUESDAY. SURFACE
HIGH PRESSURE RIDGE MOVES ACROSS THE AREA DURING THE DAY TUESDAY...
WITH WINDS BACKING TO THE SOUTH-SOUTHEAST DURING THE AFTERNOON AS
WARM ADVECTION DEVELOPS (ALOFT AT LEAST) IN ADVANCE OF A SHORT WAVE
EMERGING FROM THE PLAINS. MODERATION IN TEMPS LIMITED AT THE SURFACE
HOWEVER WITH VERY COLD START TO DAY AND STRONG INVERSION LIMITING
WARMING AT THE SURFACE WITH HIGHS IN THE TEENS/LOW 20S.
LONG RANGE GUIDANCE SIMILAR IN BRINGING SHORT WAVE TROUGH ACROSS
THE REGION DURING THE TUESDAY NIGHT/WEDNESDAY PERIOD AND ANOTHER
WEDNESDAY NIGHT/THURSDAY...THOUGH DIFFERENCES DO EXIST WITH
AMPLITUDE OF THESE INDIVIDUAL WAVES AND ASSOCIATED SURFACE
REFLECTIONS. THE ECMWF IS STRONGER/MORE AMPLIFIED WITH BOTH...
THOUGH AT THIS DISTANCE HAVE FOCUSED MAINLY ON SIMILARITIES BETWEEN
GUIDANCE. THIS YIELDS A LITTLE TEMPERATURE MODERATION CHRISTMAS EVE
AND CHRISTMAS DAY WITH A CHANCE OF SOME LIGHT SNOW...PERHAPS
0.5-1.0" BASED ON ROUGH QPF OUTPUT. LIGHT SNOW MAY LINGER ACROSS
THE EASTERN CWA CHRISTMAS NIGHT INTO THURSDAY WITH SURFACE COLD
FRONTAL TROUGH. AS MENTIONED...BRIEF MODERATION PRODUCES HIGHS IN
THE 20S/AROUND 30 FOR CHRISTMAS DAY THEN COLDER AIR LOOKS TO RETURN
THURSDAY BEHIND THE FRONT WITH TEMPS IN THE TEENS/LOW 20S.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 14Z...
* IFR CIGS LIKELY CONTINUING THROUGH THE AFTERNOON AND POSSIBLY
INTO TONIGHT.
* VSBY GRADUALLY THIS MORNING BUT LIKELY LEVELS OFF AT MVFR
THROUGH THE AFTERNOON.
* VARIABLE NORTH TO NORTH-NORTHEAST WINDS WITH SPEEDS 10-12 KT
WITH A FEW GUSTS INTO THE UPPER TEENS POSSIBLE. WINDS TURN NORTH
THEN NORTH-NORTHWEST THIS EVENING.
* PERIODIC LIGHT RAIN AND DRIZZLE CONTINUE THROUGH EARLY
AFTERNOON. TEMPS WILL FALL SO SLIGHT CHANCE FOR -FZRA/FZDZ THIS
AFTERNOON BEFORE PRECIP ENDS.
MDB/MTF
//DISCUSSION...UPDATED 12Z...
LOW PRESSURE IS NOW MOVING NORTHEAST ACROSS CENTRAL MISSOURI WITH
A FRONTAL BOUNDARY STRETCHED FROM THE LOW TO SOUTHERN ONTARIO.
THIS FRONT HAS BEEN DRIFTING SOUTH THE LAST FEW HOURS WHICH HAS
HELPED VSBY TO NOTICEABLY IMPROVE WITH CIGS ALSO IMPROVING BUT AT
A MUCH SLOWER RATE. WAVES OF RAIN/DRIZZLE CONTINUE TO MOVE ACROSS
DPA/ORD/MDW/GYY WITH FREEZING RAIN AT RFD THANKS TO AN INFLUX OF
COLDER AIR. THIS COLDER AIR WILL SPREAD SOUTHWARD ACROSS THE OTHER
TERMINALS INTO THE AFTERNOON. WITH DAYTIME HEATING AND AN END TO
THE PRECIP ARRIVING THIS AFTERNOON THE THREAT FOR FZRA/FZDZ ACROSS
THE CHI/NW INDIANA TERMINALS LOOKS LOW. HOWEVER...IF COOLING
OCCURS MORE QUICKLY THAN FORECAST THEN THE THREAT FOR FREEZING
PRECIP WILL INCREASE EARLY THIS AFTERNOON. OTHERWISE...EXPECT IFR
CIG TO PREVAIL THROUGH MUCH OF THE DAY WITH MAINLY MVFR VSBY BY
MID MORNING IF NOT SOONER AT SITES THAT STILL HAVE IFR VSBY. WINDS
WILL VARY BETWEEN NORTH AND NORTH-NORTHEAST THROUGH THE AFTERNOON
THEN TURN NORTH-NORTHWEST THIS EVENING.
THE NEXT STORM SYSTEM WILL APPROACH FROM THE SOUTH SATURDAY...WITH
PRECIP POSSIBLY REACHING THE CHI/NW INDIANA TERMINALS DURING THE
MORNING. A MIX OF PRECIPITATION TYPES IS EXPECTED WITH DETAILS OF
TIMING OF TYPE CHANGES STILL UNCERTAIN. OVERALL...RFD WILL HAVE
THE BEST CHANCE FOR SIGNIFICANT ACCUMULATING SNOW...THOUGH SLEET
MAY MIX IN AT TIMES.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 14Z...
* HIGH CONFIDENCE IN IFR CIGS CONTINUING THROUGH MUCH OF THE DAY.
LOW CONFIDENCE IN HOW QUICKLY CIGS IMPROVE.
* HIGH CONFIDENCE IN MAINLY MVFR VSBY TODAY.
* HIGH CONFIDENCE IN WIND TRENDS.
* HIGH CONFIDENCE IN LIGHT RAIN/DRIZZLE CONTINUING THROUGH EARLY
AFTERNOON. LOW CONFIDENCE IN POTENTIAL FOR -FZRA/FZDZ THIS
AFTERNOON.
MDB/MTF
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...WINTRY MIX...IFR LIKELY.
SUNDAY...SNOW AND IFR.
MONDAY...CHANCE FOR SNOW...MVFR/IFR POSSIBLE.
TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE SNOW...MVFR POSSIBLE.
THURSDAY...MVFR BECOMING VFR.
MDB
&&
.MARINE...
301 AM CST
LOW PRESSURE CENTERED OVER NORTH-CENTRAL OKLAHOMA WILL TRACK
NORTHEAST ALONG A FRONTAL BOUNDARY WHICH EXTENDS NORTHEAST INTO
NORTHERN INDIANA AND EASTWARD ACROSS LAKE ERIE AND ONTARIO.
MEANWHILE HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE LITTLE
THROUGH THE DAY. THE STRONGEST PRESSURE GRADIENT IS STARTING TO SET
UP EARLY THIS MORNING AND WILL LIKELY RESULT IN AN INCREASE IN
NORTHEAST WINDS ACROSS MUCH OF THE LAKE THROUGH MID MORNING BEFORE
THE PRESSURE GRADIENT EASES. SPEEDS MAY PUSH 30 KT FOR A TIME
THROUGH MID OR LATE MORNING...ESPECIALLY ACROSS CENTRAL SECTIONS OF
THE LAKE. THE LOW WILL PASS SOUTH OF THE LAKE LATER THIS AFTERNOON
AND BEGIN TO WEAKEN WITH THE HIGH WEAKENING AS WELL. ANOTHER SURFACE
LOW WILL DEVELOP OVER THE ARKLATEX SATURDAY AND LIFT NORTHEAST TO
NORTHERN OHIO BY SUNDAY AFTERNOON. A VERY STRONG HIGH WILL THEN
DEVELOP SOUTHWARD INTO THE NORTHERN PLAINS AS THE LOW MOVES INTO NEW
ENGLAND SUNDAY NIGHT. THIS WILL LEAVE LAKE MICHIGAN IN THE PRESSURE
GRADIENT BETWEEN THE TWO SYSTEMS SATURDAY NIGHT AND SUNDAY WITH
COLDER AIR SPILLING ACROSS THE LAKE AS WELL. THIS WILL SET THE STAGE
FOR ANOTHER ROUND OF STRONG WINDS WHICH WILL START OUT NORTHEAST
THEN SHIFT NORTH-NORTHWEST AND EASE UP LATE SUNDAY AFTERNOON. THE
HIGH WILL PASS SOUTH OF THE LAKE TUESDAY BEFORE LOW PRESSURE TRACKS
SOUTHEAST ACROSS THE CANADIAN PRAIRIES AND NORTHERN PLAINS. THIS
SHOULD LEAD TO ANOTHER PERIOD OF INCREASED WINDS...THIS TIME FROM
THE SOUTH AND SOUTHWEST WEDNESDAY. WILL KEEP SPEEDS BELOW GALE FORCE
THROUGH THE PERIOD BUT WILL NEED TO MONITOR FOR SHORT WINDOWS OF
GALE FORCE WINDS SATURDAY NIGHT AND SUNDAY MORNING...AND AGAIN EARLY
WEDNESDAY.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 3 PM FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
DENSE FOG ADVISORY...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 3 PM
FRIDAY.
FLOOD WATCH...ILZ033-ILZ039...9 AM SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 3
PM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...9 AM SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM FRIDAY.
&&
$$
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AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
559 AM CST FRI DEC 20 2013
.DISCUSSION...
355 AM CST
SEVERAL ISSUES ONGOING THIS MORNING AS WELL THROUGH THE
WEEKEND...WITH DENSE FOG AND FREEZING RAIN ISSUES THIS MORNING
WITH THE FREEZING RAIN NOW LINGERING INTO THE AFTERNOON AND
POSSIBLY TONIGHT...CONTINUED FLOODING CONCERNS...AND LASTLY
POTENTIAL SNOWFALL WHICH THE AXIS OF HEAVIEST SNOW STILL APPEARS
TO BE ACROSS THE NORTH AND NORTHWEST AREAS OF THE CWA.
ADDRESSING THE MORE IMPORTANT ISSUES IN THE NEAR TERM...LIGHT
FREEZING RAIN OR FREEZING DRIZZLE CONTINUES ACROSS THE ADVISORY
AREA THIS MORNING...WITH LIGHT RAIN OR DRIZZLE ONGOING FOR THE
REMAINDER OF THE CWA. BROAD SOUTHWESTERLY FLOW ALOFT CONTINUES TO
USHER SEVERAL WAVES OF ENERGY...WITH ELONGATED TROUGH OF LOW
PRESSURE EXTENDING FROM THE CENTRAL PLAINS UP THROUGH SOUTHERN
GREAT LAKES. AS THESE WAVES OF ENERGY/SPEED MAXES LIFT NORTHEAST
ACROSS THE REGION THIS MORNING...EXPECT THIS TROUGH OF LOW
PRESSURE TO LIFT EAST NORTHEAST TO CENTRAL ILLINOIS AND NORTHWEST
INDIANA THROUGH THE EARLY AFTERNOON. PRESENT LOW/MID LEVEL
CONVERGENCE WILL CONTINUE TO BE A PERSISTENT THROUGH THIS
PERIOD...WITH CURRENT UPSTREAM WAVE TO AID IN TIGHTENING LOW/MID
LEVEL BAROCLINIC ZONE. THIS WILL ENHANCE FRONTOGENTIC FORCING
ACROSS THE ADVISORY AREA...ALL AIDING IN CONTINUED PRECIP
DEVELOPMENT AT LEAST THROUGH EARLY AFTERNOON FOR THE ENTIRE CWA.
HAVE INCREASED POPS THIS MORNING AND EARLY AFTERNOON...BUT WONDER
IF AFTERNOON POPS WILL NEED TO BE RAISED EVEN FURTHER WITH SHORT
TERM GUIDANCE HINTING AT CONTINUED TO DEVELOPMENT EVEN INTO THE
LATE AFTERNOON. ALTHOUGH CURRENT ASSOCIATED BOUNDARY DRAPED ACROSS
EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA DID MAKE SOME
NORTHWARD PROGRESSION EARLY THIS MORNING...FEEL THAT THIS
NORTHWARD MOVEMENT HAS ENDED AND WILL REMAIN SITUATED UNTIL
DROPPING SOUTH/SOUTHEAST OF THE CWA THIS AFTERNOON. GUIDANCE
HINTING AT SOME WEAK CAA TO BEGIN OCCURRING OVER THE NEXT SEVERAL
HOURS AND WITH LATEST RAP ANALYSIS ALREADY INDICATING THIS ACROSS
WESTERN ILLINOIS...FEEL PRETTY CONFIDENT WITH THIS TREND. THIS
WILL HELP TEMPS IN THE ADVISORY AREA TO HOVER JUST BELOW OR AT THE
FREEZING MARK THROUGH MOST OF TODAY. WITH THIS CONTINUED PRECIP
AND TEMP TRENDS...HAVE DECIDED TO EXTEND THE FREEZING RAIN
ADVISORY THROUGH THE AFTERNOON AND HAVE ALSO INCLUDED KANE COUNTY
IN THE ADVISORY AS WELL. WILL NEED TO ALSO MONITOR THE AFTERNOON
PERIOD FOR THE REMAINING CWA...AS COLD ADVECTION SHOULD HELP TEMPS
LOWER AROUND FREEZING INTO THE LATE AFTERNOON PERIOD. WITH PRECIP
POSSIBLY LINGERING...COULD SEE SOME POSSIBLE LIGHT ICING IN AREAS
OUTSIDE OF THE ADVISORY. ALTHOUGH TEMPS SHOULD BE MARGINAL...AND
AM NOT OVERLY CONCERNED AT THIS TIME.
WITH REGARDS TO THE DENSE FOG...WITH INCREASING MOISTURE IN THE
BOUNDARY LAYER THIS PAST EVENING DENSE FOG DEVELOPED ALONG TO THE
NORTH OF THIS BOUNDARY. MANY REPORTS OF DENSE FOR WERE RECEIVED
THIS PAST EVENING ACROSS NORTHWEST INDIANA...PRIMARILY FOR LAKE
AND PORTER COUNTIES IN INDIANA. WITH THE BOUNDARY SITUATED AND
EXPECTED TO REMAIN THIS WAY THROUGH THE REMAINDER OF THE
MORNING...FEEL CURRENT DENSE FOG ADVISORY FOR THESE LOCATIONS
REMAINS VALID. ALTHOUGH...SOUTHERN AREAS OF COOK COUNTY AND
EASTERN AREAS OF WILL COUNTY WILL NEED TO BE MONITORED OVER THE
NEXT COUPLE OF HOURS AS VIS IN THESE LOCATIONS CONTINUES TO BOUNCE
AROUND 1/2 MILE. END TIMING FOR THIS DENSE FOG ADVISORY REMAINS 9
AM CST...AND SEEMS REASONABLE. THIS SAGGING BOUNDARY AND SLIGHTLY
DRIER AIR SHOULD HELP WITH THE MORE DENSE FOG...BUT WITH PATCHY
DENSE FOG STILL NOT OUT OF THE QUESTION AT LEAST THROUGH MID DAY.
CONFIDENCE WITH THIS FOG REMAINS LOW AT THIS TIME AND WILL NEED TO
MONITOR...POSSIBLY EXTENDING THIS ADVISORY OR MAYBE EVEN EXPANDING
IT LATER THIS MORNING.
WITH SURFACE LOW EXITING TO THE EAST THIS EVENING AND THE ARRIVAL
OF DRIER AIR...SHOULD OBSERVE OVERALL PRECIP CHANCES TO WIND DOWN
FOR THE TIME BEING. ALTHOUGH WITH GUIDANCE CONTINUING TO INDICATE
BROAD SCALE LIFT WITH THE APPROACHING LONGWAVE TROUGH TO THE WEST
IT DOES APPEAR AS IF AREAS ACROSS THE SOUTHERN CWA COULD SEE
ADDITIONAL PRECIP TONIGHT. ALTHOUGH LIGHT PRECIP...THERMAL
PROFILES WOULD INDICATE THAT THIS PRECIP WOULD BE IN THE FORM OF
LIGHT FREEZING RAIN OR LIGHT FREEZING DRIZZLE. ANOTHER PERIOD I AM
CONCERNED ABOUT AT THIS TIME IS LATE TONIGHT INTO EARLY SATURDAY
MORNING...ONCE AGAIN FOR AREAS ACROSS THE SOUTHERN CWA. WILL NEED
TO MONITOR SURFACE TEMP TRENDS ACROSS EAST CENTRAL ILLINOIS DURING
THIS TIME...WITH FREEZING RAIN ONCE AGAIN POSSIBLY BEING AN ISSUE.
EXPANDING PRECIP TO THE SOUTH IS EXPECTED TO INCH FURTHER NORTH
TOWARDS THE SOUTHERN CWA TOWARDS THE 12Z SATURDAY TIME
FRAME...WITH SOUTHWEST FLOW ALOFT PERSISTING OUT AHEAD OF THE
APPROACHING LONGWAVE TROUGH. WITH A SLOW TEMP TREND EXPECTED
SATURDAY MORNING...A PERIOD OF LIGHT FREEZING RAIN COULD CAUSE
SOME ISSUES PRIMARILY SOUTH OF I-80.
WITH REGARDS TO WINTER STORM SATURDAY THROUGH SUNDAY...LATEST
THINKING/UPDATES TO FORECAST CONTINUE TO SUPPORT CURRENT WINTER
STORM WATCH ACROSS NORTHERN PORTIONS OF THE CWA. EXPECTED VARYING
PRECIP TYPES INCLUDING ALMOST ALL WINTER PRECIP TYPES COULD BE
OBSERVED SATURDAY INTO SATURDAY NIGHT...WITH A VARYING THERMAL
PROFILE EXPECTED TO CHANGE THROUGH THE PERIOD FOR ALL AREAS. WILL
NEED TO MONITOR THE SATURDAY MORNING TIME FRAME INTO THE DAY
SATURDAY FOR THE VARYING PREICP TYPE...POSSIBLY ADDING YET ANOTHER
HEADLINE TO ACCOMMODATE FOR THE WINTRY MIX. EXPECTED SURFACE LOW
TRACK STILL SUPPORTIVE FOR BEST CHANCES FOR SNOW OR ALL SNOW
ACROSS NORTHWEST AND NORTH CENTRAL ILLINOIS WITH SNOWFALL TOTALS
IN EXCESS OF 6 INCHES STILL APPEARING POSSIBLE. THE EXPECTED RAIN
SNOW LINE HAS VARIED SLIGHTLY...BUT THE GENERAL IDEA REMAINING THE
SAME. OHARE TO PERU ILLINOIS LINE ARE THE DIVIDING LINE AT THIS
TIME...WITH CURRENT SNOW FORECAST INDICATING RAPID INCREASE IN
SNOW AMOUNTS RIGHT TO THE NORTH OF THIS LINE AND WITH AREAS TO THE
SOUTH OBSERVING LIGHT SNOW ACCUMULATIONS.
ALTHOUGH LATEST TRENDS ARE INDICATING THAT THE AXIS OF HEAVIEST
RAINFALL IS BEGINNING TO SHIFT SOUTH OF THE CWA...DECENT RAINFALL
AMOUNTS OF UP TO AN INCH STILL SUPPORT THE POSSIBILITY OF
FLOODING...AND HAVE MADE NO CHANGES TO THE CURRENT FLOOD WATCH.
RODRIGUEZ
MEDIUM AND LONG RANGE...MONDAY THROUGH THURSDAY...
MAIN CONCERNS BEYOND THIS WEEKEND ARE THE RETURN OF ARCTIC AIR AND
MUCH COLDER TEMPERATURES MONDAY-TUESDAY...AND THE POTENTIAL FOR A
LITTLE LIGHT SNOW CHRISTMAS EVE-CHRISTMAS DAY.
DEEP UPPER TROUGH TRAVERSING THE REGION MONDAY WITH FAIRLY
IMPRESSIVE SHORT WAVE ENERGY PASSING OVERHEAD. FORECAST SOUNDINGS
INDICATE SATURATION IN LOW LEVELS...WITH TEMPS NEAR -15C AS BOUNDARY
LAYER COOLS IN BLUSTERY COLD ADVECTION BEHIND DEPARTING WEEKEND LOW
PRESSURE SYSTEM. THIS SHOULD SUPPORT FLURRIES/LIGHT SNOW SHOWERS
ACROSS THE CWA INTO THE AFTERNOON HOURS. OF MORE IMPORTANCE THAN THE
POTENTIAL FOR LIGHT SNOW SHOWERS OR FLURRIES HOWEVER WILL BE THE
MUCH COLDER TEMPS AND WIND CHILLS AS ARCTIC AIR PLUNGES BACK INTO
THE REGION. TEMPS AT H8 FALL TO AROUND -16 C BY LATE AFTERNOON WITH
H9 TEMPS NEARLY SO...SUGGESTING SURFACE TEMPS MAY STRUGGLE TO RISE
ABOVE 10-15F AND WILL LIKELY FALL INTO THE SINGLE DIGITS ACROSS
NORTH CENTRAL IL AND WIND CHILLS IN THE NEGATIVE SINGLE DIGITS.
SURFACE HIGH PRESSURE RIDGE WILL BUILD ACROSS THE MISSISSIPPI VALLEY
AND INTO IL MONDAY NIGHT IN RESPONSE TO SUBSIDENCE BEHIND THE
DEPARTING UPPER TROUGH...WITH CLEARING SKIES...NEW SNOW COVER
ESPECIALLY FAR NORTHERN IL...AND DECREASING WINDS EXPECTED TO RESULT
IN STRONG RADIATIONAL COOLING. BOTH GFS AND ECMWF MOS DEPICT
SUB-ZERO LOWS ACROSS MUCH OF NORTHERN IL BY SUNRISE TUESDAY. SURFACE
HIGH PRESSURE RIDGE MOVES ACROSS THE AREA DURING THE DAY TUESDAY...
WITH WINDS BACKING TO THE SOUTH-SOUTHEAST DURING THE AFTERNOON AS
WARM ADVECTION DEVELOPS (ALOFT AT LEAST) IN ADVANCE OF A SHORT WAVE
EMERGING FROM THE PLAINS. MODERATION IN TEMPS LIMITED AT THE SURFACE
HOWEVER WITH VERY COLD START TO DAY AND STRONG INVERSION LIMITING
WARMING AT THE SURFACE WITH HIGHS IN THE TEENS/LOW 20S.
LONG RANGE GUIDANCE SIMILAR IN BRINGING SHORT WAVE TROUGH ACROSS
THE REGION DURING THE TUESDAY NIGHT/WEDNESDAY PERIOD AND ANOTHER
WEDNESDAY NIGHT/THURSDAY...THOUGH DIFFERENCES DO EXIST WITH
AMPLITUDE OF THESE INDIVIDUAL WAVES AND ASSOCIATED SURFACE
REFLECTIONS. THE ECMWF IS STRONGER/MORE AMPLIFIED WITH BOTH...
THOUGH AT THIS DISTANCE HAVE FOCUSED MAINLY ON SIMILARITIES BETWEEN
GUIDANCE. THIS YIELDS A LITTLE TEMPERATURE MODERATION CHRISTMAS EVE
AND CHRISTMAS DAY WITH A CHANCE OF SOME LIGHT SNOW...PERHAPS
0.5-1.0" BASED ON ROUGH QPF OUTPUT. LIGHT SNOW MAY LINGER ACROSS
THE EASTERN CWA CHRISTMAS NIGHT INTO THURSDAY WITH SURFACE COLD
FRONTAL TROUGH. AS MENTIONED...BRIEF MODERATION PRODUCES HIGHS IN
THE 20S/AROUND 30 FOR CHRISTMAS DAY THEN COLDER AIR LOOKS TO RETURN
THURSDAY BEHIND THE FRONT WITH TEMPS IN THE TEENS/LOW 20S.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 12Z...
* IFR CIGS LIKELY CONTINUING THROUGH THE AFTERNOON AND POSSIBLY
INTO TONIGHT.
* VSBY GRADUALLY THIS MORNING BUT LIKELY LEVELS OFF AT MVFR
THROUGH THE AFTERNOON.
* VARIABLE NORTH TO NORTH-NORTHEAST WINDS WITH SPEEDS 10-12 KT
WITH A FEW GUSTS INTO THE UPPER TEENS POSSIBLE. WINDS TURN NORTH
THEN NORTH-NORTHWEST THIS EVENING.
* PERIODIC LIGHT RAIN AND DRIZZLE CONTINUE THROUGH EARLY
AFTERNOON. TEMPS WILL FALL SO SLIGHT CHANCE FOR -FZRA/FZDZ THIS
AFTERNOON BEFORE PRECIP ENDS.
MDB
//DISCUSSION...UPDATED 12Z...
LOW PRESSURE IS NOW MOVING NORTHEAST ACROSS CENTRAL MISSOURI WITH
A FRONTAL BOUNDARY STRETCHED FROM THE LOW TO SOUTHERN ONTARIO.
THIS FRONT HAS BEEN DRIFTING SOUTH THE LAST FEW HOURS WHICH HAS
HELPED VSBY TO NOTICEABLY IMPROVE WITH CIGS ALSO IMPROVING BUT AT
A MUCH SLOWER RATE. WAVES OF RAIN/DRIZZLE CONTINUE TO MOVE ACROSS
DPA/ORD/MDW/GYY WITH FREEZING RAIN AT RFD THANKS TO AN INFLUX OF
COLDER AIR. THIS COLDER AIR WILL SPREAD SOUTHWARD ACROSS THE OTHER
TERMINALS INTO THE AFTERNOON. WITH DAYTIME HEATING AND AN END TO
THE PRECIP ARRIVING THIS AFTERNOON THE THREAT FOR FZRA/FZDZ ACROSS
THE CHI/NW INDIANA TERMINALS LOOKS LOW. HOWEVER...IF COOLING
OCCURS MORE QUICKLY THAN FORECAST THEN THE THREAT FOR FREEZING
PRECIP WILL INCREASE EARLY THIS AFTERNOON. OTHERWISE...EXPECT IFR
CIG TO PREVAIL THROUGH MUCH OF THE DAY WITH MAINLY MVFR VSBY BY
MID MORNING IF NOT SOONER AT SITES THAT STILL HAVE IFR VSBY. WINDS
WILL VARY BETWEEN NORTH AND NORTH-NORTHEAST THROUGH THE AFTERNOON
THEN TURN NORTH-NORTHWEST THIS EVENING.
THE NEXT STORM SYSTEM WILL APPROACH FROM THE SOUTH SATURDAY...WITH
PRECIP POSSIBLY REACHING THE CHI/NW INDIANA TERMINALS DURING THE
MORNING. A MIX OF PRECIPITATION TYPES IS EXPECTED WITH DETAILS OF
TIMING OF TYPE CHANGES STILL UNCERTAIN. OVERALL...RFD WILL HAVE
THE BEST CHANCE FOR SIGNIFICANT ACCUMULATING SNOW...THOUGH SLEET
MAY MIX IN AT TIMES.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 12Z...
* HIGH CONFIDENCE IN IFR CIGS CONTINUING THROUGH MUCH OF THE DAY.
LOW CONFIDENCE IN HOW QUICKLY CIGS IMPROVE.
* HIGH CONFIDENCE IN MAINLY MVFR VSBY TODAY.
* HIGH CONFIDENCE IN WIND TRENDS.
* HIGH CONFIDENCE IN LIGHT RAIN/DRIZZLE CONTINUING THROUGH EARLY
AFTERNOON. LOW CONFIDENCE IN POTENTIAL FOR -FZRA/FZDZ THIS
AFTERNOON.
MDB
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...WINTRY MIX...IFR LIKELY.
SUNDAY...SNOW AND IFR.
MONDAY...CHANCE FOR SNOW...MVFR/IFR POSSIBLE.
TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE SNOW...MVFR POSSIBLE.
THURSDAY...MVFR BECOMING VFR.
MDB
&&
.MARINE...
301 AM CST
LOW PRESSURE CENTERED OVER NORTH-CENTRAL OKLAHOMA WILL TRACK
NORTHEAST ALONG A FRONTAL BOUNDARY WHICH EXTENDS NORTHEAST INTO
NORTHERN INDIANA AND EASTWARD ACROSS LAKE ERIE AND ONTARIO.
MEANWHILE HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE LITTLE
THROUGH THE DAY. THE STRONGEST PRESSURE GRADIENT IS STARTING TO SET
UP EARLY THIS MORNING AND WILL LIKELY RESULT IN AN INCREASE IN
NORTHEAST WINDS ACROSS MUCH OF THE LAKE THROUGH MID MORNING BEFORE
THE PRESSURE GRADIENT EASES. SPEEDS MAY PUSH 30 KT FOR A TIME
THROUGH MID OR LATE MORNING...ESPECIALLY ACROSS CENTRAL SECTIONS OF
THE LAKE. THE LOW WILL PASS SOUTH OF THE LAKE LATER THIS AFTERNOON
AND BEGIN TO WEAKEN WITH THE HIGH WEAKENING AS WELL. ANOTHER SURFACE
LOW WILL DEVELOP OVER THE ARKLATEX SATURDAY AND LIFT NORTHEAST TO
NORTHERN OHIO BY SUNDAY AFTERNOON. A VERY STRONG HIGH WILL THEN
DEVELOP SOUTHWARD INTO THE NORTHERN PLAINS AS THE LOW MOVES INTO NEW
ENGLAND SUNDAY NIGHT. THIS WILL LEAVE LAKE MICHIGAN IN THE PRESSURE
GRADIENT BETWEEN THE TWO SYSTEMS SATURDAY NIGHT AND SUNDAY WITH
COLDER AIR SPILLING ACROSS THE LAKE AS WELL. THIS WILL SET THE STAGE
FOR ANOTHER ROUND OF STRONG WINDS WHICH WILL START OUT NORTHEAST
THEN SHIFT NORTH-NORTHWEST AND EASE UP LATE SUNDAY AFTERNOON. THE
HIGH WILL PASS SOUTH OF THE LAKE TUESDAY BEFORE LOW PRESSURE TRACKS
SOUTHEAST ACROSS THE CANADIAN PRAIRIES AND NORTHERN PLAINS. THIS
SHOULD LEAD TO ANOTHER PERIOD OF INCREASED WINDS...THIS TIME FROM
THE SOUTH AND SOUTHWEST WEDNESDAY. WILL KEEP SPEEDS BELOW GALE FORCE
THROUGH THE PERIOD BUT WILL NEED TO MONITOR FOR SHORT WINDOWS OF
GALE FORCE WINDS SATURDAY NIGHT AND SUNDAY MORNING...AND AGAIN EARLY
WEDNESDAY.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 3 PM FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
FLOOD WATCH...ILZ033-ILZ039...9 AM SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002 UNTIL 9 AM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...9 AM SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...LMZ740...9 AM FRIDAY TO 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 AM FRIDAY.
&&
$$
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AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
510 AM CST FRI DEC 20 2013
.DISCUSSION...
355 AM CST
SEVERAL ISSUES ONGOING THIS MORNING AS WELL THROUGH THE
WEEKEND...WITH DENSE FOG AND FREEZING RAIN ISSUES THIS MORNING
WITH THE FREEZING RAIN NOW LINGERING INTO THE AFTERNOON AND
POSSIBLY TONIGHT...CONTINUED FLOODING CONCERNS...AND LASTLY
POTENTIAL SNOWFALL WHICH THE AXIS OF HEAVIEST SNOW STILL APPEARS
TO BE ACROSS THE NORTH AND NORTHWEST AREAS OF THE CWA.
ADDRESSING THE MORE IMPORTANT ISSUES IN THE NEAR TERM...LIGHT
FREEZING RAIN OR FREEZING DRIZZLE CONTINUES ACROSS THE ADVISORY
AREA THIS MORNING...WITH LIGHT RAIN OR DRIZZLE ONGOING FOR THE
REMAINDER OF THE CWA. BROAD SOUTHWESTERLY FLOW ALOFT CONTINUES TO
USHER SEVERAL WAVES OF ENERGY...WITH ELONGATED TROUGH OF LOW
PRESSURE EXTENDING FROM THE CENTRAL PLAINS UP THROUGH SOUTHERN
GREAT LAKES. AS THESE WAVES OF ENERGY/SPEED MAXES LIFT NORTHEAST
ACROSS THE REGION THIS MORNING...EXPECT THIS TROUGH OF LOW
PRESSURE TO LIFT EAST NORTHEAST TO CENTRAL ILLINOIS AND NORTHWEST
INDIANA THROUGH THE EARLY AFTERNOON. PRESENT LOW/MID LEVEL
CONVERGENCE WILL CONTINUE TO BE A PERSISTENT THROUGH THIS
PERIOD...WITH CURRENT UPSTREAM WAVE TO AID IN TIGHTENING LOW/MID
LEVEL BAROCLINIC ZONE. THIS WILL ENHANCE FRONTOGENTIC FORCING
ACROSS THE ADVISORY AREA...ALL AIDING IN CONTINUED PRECIP
DEVELOPMENT AT LEAST THROUGH EARLY AFTERNOON FOR THE ENTIRE CWA.
HAVE INCREASED POPS THIS MORNING AND EARLY AFTERNOON...BUT WONDER
IF AFTERNOON POPS WILL NEED TO BE RAISED EVEN FURTHER WITH SHORT
TERM GUIDANCE HINTING AT CONTINUED TO DEVELOPMENT EVEN INTO THE
LATE AFTERNOON. ALTHOUGH CURRENT ASSOCIATED BOUNDARY DRAPED ACROSS
EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA DID MAKE SOME
NORTHWARD PROGRESSION EARLY THIS MORNING...FEEL THAT THIS
NORTHWARD MOVEMENT HAS ENDED AND WILL REMAIN SITUATED UNTIL
DROPPING SOUTH/SOUTHEAST OF THE CWA THIS AFTERNOON. GUIDANCE
HINTING AT SOME WEAK CAA TO BEGIN OCCURRING OVER THE NEXT SEVERAL
HOURS AND WITH LATEST RAP ANALYSIS ALREADY INDICATING THIS ACROSS
WESTERN ILLINOIS...FEEL PRETTY CONFIDENT WITH THIS TREND. THIS
WILL HELP TEMPS IN THE ADVISORY AREA TO HOVER JUST BELOW OR AT THE
FREEZING MARK THROUGH MOST OF TODAY. WITH THIS CONTINUED PRECIP
AND TEMP TRENDS...HAVE DECIDED TO EXTEND THE FREEZING RAIN
ADVISORY THROUGH THE AFTERNOON AND HAVE ALSO INCLUDED KANE COUNTY
IN THE ADVISORY AS WELL. WILL NEED TO ALSO MONITOR THE AFTERNOON
PERIOD FOR THE REMAINING CWA...AS COLD ADVECTION SHOULD HELP TEMPS
LOWER AROUND FREEZING INTO THE LATE AFTERNOON PERIOD. WITH PRECIP
POSSIBLY LINGERING...COULD SEE SOME POSSIBLE LIGHT ICING IN AREAS
OUTSIDE OF THE ADVISORY. ALTHOUGH TEMPS SHOULD BE MARGINAL...AND
AM NOT OVERLY CONCERNED AT THIS TIME.
WITH REGARDS TO THE DENSE FOG...WITH INCREASING MOISTURE IN THE
BOUNDARY LAYER THIS PAST EVENING DENSE FOG DEVELOPED ALONG TO THE
NORTH OF THIS BOUNDARY. MANY REPORTS OF DENSE FOR WERE RECEIVED
THIS PAST EVENING ACROSS NORTHWEST INDIANA...PRIMARILY FOR LAKE
AND PORTER COUNTIES IN INDIANA. WITH THE BOUNDARY SITUATED AND
EXPECTED TO REMAIN THIS WAY THROUGH THE REMAINDER OF THE
MORNING...FEEL CURRENT DENSE FOG ADVISORY FOR THESE LOCATIONS
REMAINS VALID. ALTHOUGH...SOUTHERN AREAS OF COOK COUNTY AND
EASTERN AREAS OF WILL COUNTY WILL NEED TO BE MONITORED OVER THE
NEXT COUPLE OF HOURS AS VIS IN THESE LOCATIONS CONTINUES TO BOUNCE
AROUND 1/2 MILE. END TIMING FOR THIS DENSE FOG ADVISORY REMAINS 9
AM CST...AND SEEMS REASONABLE. THIS SAGGING BOUNDARY AND SLIGHTLY
DRIER AIR SHOULD HELP WITH THE MORE DENSE FOG...BUT WITH PATCHY
DENSE FOG STILL NOT OUT OF THE QUESTION AT LEAST THROUGH MID DAY.
CONFIDENCE WITH THIS FOG REMAINS LOW AT THIS TIME AND WILL NEED TO
MONITOR...POSSIBLY EXTENDING THIS ADVISORY OR MAYBE EVEN EXPANDING
IT LATER THIS MORNING.
WITH SURFACE LOW EXITING TO THE EAST THIS EVENING AND THE ARRIVAL
OF DRIER AIR...SHOULD OBSERVE OVERALL PRECIP CHANCES TO WIND DOWN
FOR THE TIME BEING. ALTHOUGH WITH GUIDANCE CONTINUING TO INDICATE
BROAD SCALE LIFT WITH THE APPROACHING LONGWAVE TROUGH TO THE WEST
IT DOES APPEAR AS IF AREAS ACROSS THE SOUTHERN CWA COULD SEE
ADDITIONAL PRECIP TONIGHT. ALTHOUGH LIGHT PRECIP...THERMAL
PROFILES WOULD INDICATE THAT THIS PRECIP WOULD BE IN THE FORM OF
LIGHT FREEZING RAIN OR LIGHT FREEZING DRIZZLE. ANOTHER PERIOD I AM
CONCERNED ABOUT AT THIS TIME IS LATE TONIGHT INTO EARLY SATURDAY
MORNING...ONCE AGAIN FOR AREAS ACROSS THE SOUTHERN CWA. WILL NEED
TO MONITOR SURFACE TEMP TRENDS ACROSS EAST CENTRAL ILLINOIS DURING
THIS TIME...WITH FREEZING RAIN ONCE AGAIN POSSIBLY BEING AN ISSUE.
EXPANDING PRECIP TO THE SOUTH IS EXPECTED TO INCH FURTHER NORTH
TOWARDS THE SOUTHERN CWA TOWARDS THE 12Z SATURDAY TIME
FRAME...WITH SOUTHWEST FLOW ALOFT PERSISTING OUT AHEAD OF THE
APPROACHING LONGWAVE TROUGH. WITH A SLOW TEMP TREND EXPECTED
SATURDAY MORNING...A PERIOD OF LIGHT FREEZING RAIN COULD CAUSE
SOME ISSUES PRIMARILY SOUTH OF I-80.
WITH REGARDS TO WINTER STORM SATURDAY THROUGH SUNDAY...LATEST
THINKING/UPDATES TO FORECAST CONTINUE TO SUPPORT CURRENT WINTER
STORM WATCH ACROSS NORTHERN PORTIONS OF THE CWA. EXPECTED VARYING
PRECIP TYPES INCLUDING ALMOST ALL WINTER PRECIP TYPES COULD BE
OBSERVED SATURDAY INTO SATURDAY NIGHT...WITH A VARYING THERMAL
PROFILE EXPECTED TO CHANGE THROUGH THE PERIOD FOR ALL AREAS. WILL
NEED TO MONITOR THE SATURDAY MORNING TIME FRAME INTO THE DAY
SATURDAY FOR THE VARYING PREICP TYPE...POSSIBLY ADDING YET ANOTHER
HEADLINE TO ACCOMMODATE FOR THE WINTRY MIX. EXPECTED SURFACE LOW
TRACK STILL SUPPORTIVE FOR BEST CHANCES FOR SNOW OR ALL SNOW
ACROSS NORTHWEST AND NORTH CENTRAL ILLINOIS WITH SNOWFALL TOTALS
IN EXCESS OF 6 INCHES STILL APPEARING POSSIBLE. THE EXPECTED RAIN
SNOW LINE HAS VARIED SLIGHTLY...BUT THE GENERAL IDEA REMAINING THE
SAME. OHARE TO PERU ILLINOIS LINE ARE THE DIVIDING LINE AT THIS
TIME...WITH CURRENT SNOW FORECAST INDICATING RAPID INCREASE IN
SNOW AMOUNTS RIGHT TO THE NORTH OF THIS LINE AND WITH AREAS TO THE
SOUTH OBSERVING LIGHT SNOW ACCUMULATIONS.
ALTHOUGH LATEST TRENDS ARE INDICATING THAT THE AXIS OF HEAVIEST
RAINFALL IS BEGINNING TO SHIFT SOUTH OF THE CWA...DECENT RAINFALL
AMOUNTS OF UP TO AN INCH STILL SUPPORT THE POSSIBILITY OF
FLOODING...AND HAVE MADE NO CHANGES TO THE CURRENT FLOOD WATCH.
RODRIGUEZ
MEDIUM AND LONG RANGE...MONDAY THROUGH THURSDAY...
MAIN CONCERNS BEYOND THIS WEEKEND ARE THE RETURN OF ARCTIC AIR AND
MUCH COLDER TEMPERATURES MONDAY-TUESDAY...AND THE POTENTIAL FOR A
LITTLE LIGHT SNOW CHRISTMAS EVE-CHRISTMAS DAY.
DEEP UPPER TROUGH TRAVERSING THE REGION MONDAY WITH FAIRLY
IMPRESSIVE SHORT WAVE ENERGY PASSING OVERHEAD. FORECAST SOUNDINGS
INDICATE SATURATION IN LOW LEVELS...WITH TEMPS NEAR -15C AS BOUNDARY
LAYER COOLS IN BLUSTERY COLD ADVECTION BEHIND DEPARTING WEEKEND LOW
PRESSURE SYSTEM. THIS SHOULD SUPPORT FLURRIES/LIGHT SNOW SHOWERS
ACROSS THE CWA INTO THE AFTERNOON HOURS. OF MORE IMPORTANCE THAN THE
POTENTIAL FOR LIGHT SNOW SHOWERS OR FLURRIES HOWEVER WILL BE THE
MUCH COLDER TEMPS AND WIND CHILLS AS ARCTIC AIR PLUNGES BACK INTO
THE REGION. TEMPS AT H8 FALL TO AROUND -16 C BY LATE AFTERNOON WITH
H9 TEMPS NEARLY SO...SUGGESTING SURFACE TEMPS MAY STRUGGLE TO RISE
ABOVE 10-15F AND WILL LIKELY FALL INTO THE SINGLE DIGITS ACROSS
NORTH CENTRAL IL AND WIND CHILLS IN THE NEGATIVE SINGLE DIGITS.
SURFACE HIGH PRESSURE RIDGE WILL BUILD ACROSS THE MISSISSIPPI VALLEY
AND INTO IL MONDAY NIGHT IN RESPONSE TO SUBSIDENCE BEHIND THE
DEPARTING UPPER TROUGH...WITH CLEARING SKIES...NEW SNOW COVER
ESPECIALLY FAR NORTHERN IL...AND DECREASING WINDS EXPECTED TO RESULT
IN STRONG RADIATIONAL COOLING. BOTH GFS AND ECMWF MOS DEPICT
SUB-ZERO LOWS ACROSS MUCH OF NORTHERN IL BY SUNRISE TUESDAY. SURFACE
HIGH PRESSURE RIDGE MOVES ACROSS THE AREA DURING THE DAY TUESDAY...
WITH WINDS BACKING TO THE SOUTH-SOUTHEAST DURING THE AFTERNOON AS
WARM ADVECTION DEVELOPS (ALOFT AT LEAST) IN ADVANCE OF A SHORT WAVE
EMERGING FROM THE PLAINS. MODERATION IN TEMPS LIMITED AT THE SURFACE
HOWEVER WITH VERY COLD START TO DAY AND STRONG INVERSION LIMITING
WARMING AT THE SURFACE WITH HIGHS IN THE TEENS/LOW 20S.
LONG RANGE GUIDANCE SIMILAR IN BRINGING SHORT WAVE TROUGH ACROSS
THE REGION DURING THE TUESDAY NIGHT/WEDNESDAY PERIOD AND ANOTHER
WEDNESDAY NIGHT/THURSDAY...THOUGH DIFFERENCES DO EXIST WITH
AMPLITUDE OF THESE INDIVIDUAL WAVES AND ASSOCIATED SURFACE
REFLECTIONS. THE ECMWF IS STRONGER/MORE AMPLIFIED WITH BOTH...
THOUGH AT THIS DISTANCE HAVE FOCUSED MAINLY ON SIMILARITIES BETWEEN
GUIDANCE. THIS YIELDS A LITTLE TEMPERATURE MODERATION CHRISTMAS EVE
AND CHRISTMAS DAY WITH A CHANCE OF SOME LIGHT SNOW...PERHAPS
0.5-1.0" BASED ON ROUGH QPF OUTPUT. LIGHT SNOW MAY LINGER ACROSS
THE EASTERN CWA CHRISTMAS NIGHT INTO THURSDAY WITH SURFACE COLD
FRONTAL TROUGH. AS MENTIONED...BRIEF MODERATION PRODUCES HIGHS IN
THE 20S/AROUND 30 FOR CHRISTMAS DAY THEN COLDER AIR LOOKS TO RETURN
THURSDAY BEHIND THE FRONT WITH TEMPS IN THE TEENS/LOW 20S.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* CIG/VSBY TRENDS THROUGH THE DAY WITH IFR CONTINUING. DENSE FOG
IN CLOSE PROXIMITY TO MDW WITH 1/4-1/2SM VSBY STILL POSSIBLE
THROUGH DAYBREAK.
* PERIODIC -RA/DZ THROUGH MIDDAY WITH LOW CHANCE FOR SOME
-FZRA/FZDZ THIS AFTERNOON...MAINLY A ORD.
* NORTH TO NORTH-NORTHEAST WINDS INCREASING TO AROUND 10 KT THEN
TURNING NORTHWEST THIS EVENING.
MDB
//DISCUSSION...UPDATED 09Z...
WARM FRONTAL BOUNDARY HAS BEEN OSCILLATING NORTH AND SOUTH OVER A
NARROW CORRIDOR FROM ROUGHLY KGBG TO KGYY AND SOUTHERN LOWER
MICHIGAN THE PAST FEW HOURS. THIS HAS RESULTED IN A SOMEWHAT
TRANSIENT BAND OF DENSE FOG WHICH AS BEEN AFFECTING MDW AND GYY AT
TIMES. A LOOK AT AREA WEBCAMS AND SURFACE OBS SHOWS THAT THERE HAS
BEEN SOME SLIGHT IMPROVEMENT IN VSBY RIGHT ALONG THE BOUNDARY BUT
THIS MAY BE DUE TO THE BAND OF DENSE FOG MOVING BACK AND FORTH VS.
ANY CHANGE IN LOWEST VSBYS. EXPECT THAT THE BOUNDARY WILL MEANDER
THROUGH DAYBREAK LEAVING MDW/GYY IN A VARIABLE VSBY SITUATION AND
CANNOT RULE OUT A RETURN TO 1/4-1/2SM VSBY FOR AT LEAST A SHORT
TIME. THE BOUNDARY DOES LOOK TO PUSH SOUTH LATER THIS MORNING AS
SURFACE LOW PRESSURE MOVES NORTHEAST ALONG IT. THIS SHOULD ALLOW
NORTHERLY WINDS TO SET UP WITH COOLER AIR SPREADING SOUTH WHICH
SHOULD HELP VSBY. MAY BE TOUGH TO LOSE THE IFR CIGS BUT MVFR VSBY
LOOKS TO OCCUR TOWARD/DURING THE AFTERNOON AT SOME POINT.
OTHERWISE PERIODS OF -RA/DZ WILL CONTINUE THROUGH THE MORNING.
MDB
FROM 06Z...
MESSY CONDITIONS CONTINUE ACROSS THE TERMINALS TONIGHT WITH A
FRONTAL BOUNDARY STRETCHING FROM LOW PRESSURE OVER OKLAHOMA TO
ROUGHLY A KEOK TO KC75 TO KVPZ LINE. ABUNDANT MOISTURE AND LIFT
CONTINUE OVER THE BOUNDARY BRINGING RAIN SHOWERS AND AREAS OF
DRIZZLE TO THE TERMINALS. VSBY IS LOWEST RIGHT ALONG THE BOUNDARY
WITH GYY AROUND 1/4SM AND THIS WILL LIKELY PERSIST AS LONG AS THE
BOUNDARY IS NEARBY...WHICH AT THIS POINT LOOKS TO BE FOR MUCH OF
THE OVERNIGHT. AREAS NORTH HAVE SEEN VSBY GENERALLY AROUND A MILE
AND THIS SHOULD BE THE TREND THROUGH THE NIGHT...THOUGH THERE MAY
BE SOME DOWNWARD FLUCTUATIONS AT TIMES. CIGS SHOULD STAY STEADY
IN THE 002-004 RANGE THROUGH THE NIGHT AS WELL. RFD MAY SEE SOME
FREEZING RAIN/FREEZING DRIZZLE OVERNIGHT AS TEMPS COOL SLIGHTLY.
THINGS BECOME LESS CERTAIN AFTER DAYBREAK. THE LOW WILL TRACK
NORTHEAST TO NORTH-CENTRAL INDIANA BY FRIDAY AFTERNOON TURNING
WINDS FROM NORTHEAST TO NORTH-NORTHWEST THROUGH THE AFTERNOON. THE
MAIN QUESTION WILL BE HOW QUICKLY AND TO WHAT EXTENT CIGS/VSBY
IMPROVE. WITH THE BOUNDARY STILL IN THE AREA THROUGH THE MORNING
WILL ONLY HAVE VERY MINOR INCREASES IN CIGS/VSBY WITH BETTER
INCREASES DURING THE AFTERNOON AS COLDER AIR FILTERS INTO THE
REGION. SHOWERS/DRIZZLE WILL CONTINUE PERIODICALLY BEFORE TAPERING
OFF DURING THE AFTERNOON. RFD WILL HAVE THE BEST CHANCE OF SEEING
FREEZING RAIN THROUGH THE MORNING...WITH A LOW CHANCE THAT SOME
LIGHT FREEZING RAIN OR FREEZING DRIZZLE WILL MAKE IT INTO THE
CHICAGO TERMINALS DURING THE EARLY AFTERNOON AS COLDER AIR
ARRIVES. MVFR AND POSSIBLY IFR LOOK TO BE IN PLACE FOR FRIDAY
EVENING WITH NORTH-NORTHWEST WINDS.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* HIGH CONFIDENCE IN IFR CONTINUING WITH LOWEST CONDITIONS THROUGH
DAYBREAK. LOW CONFIDENCE WITH SPEED/MAGNITUDE OF CIG/VSBY
IMPROVEMENT THROUGH THE DAY.
* HIGH CONFIDENCE IN PRECIP WINDING DOWN THIS AFTERNOON...MEDIUM-
HIGH CONFIDENCE THAT THREAT FOR -FZRA/FZDZ AT ORD IS LOW.
* HIGH CONFIDENCE IN WIND TRENDS.
MDB
//OUTLOOK FOR ORD/MDW FOR 12Z SATURDAY-12Z THURSDAY...UPDATED 00Z...
SAT...WINTRY MIX OF PRECIP FROM MIDDAY ON...WITH A CHANCE OF A
PERIOD OF FREEZING RAIN DURING THE NIGHT. MVFR TO IFR.
SUN...SNOW. MVFR TO IFR.
MON...MVFR CIGS. CHANCE OF SNOW SHOWERS WITH IFR.
TUE...VFR.
WED...VFR BECOMING MVFR CIGS.
THU...MVFR CIGS IMPROVING TO VFR.
TRS
&&
.MARINE...
301 AM CST
LOW PRESSURE CENTERED OVER NORTH-CENTRAL OKLAHOMA WILL TRACK
NORTHEAST ALONG A FRONTAL BOUNDARY WHICH EXTENDS NORTHEAST INTO
NORTHERN INDIANA AND EASTWARD ACROSS LAKE ERIE AND ONTARIO.
MEANWHILE HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE LITTLE
THROUGH THE DAY. THE STRONGEST PRESSURE GRADIENT IS STARTING TO SET
UP EARLY THIS MORNING AND WILL LIKELY RESULT IN AN INCREASE IN
NORTHEAST WINDS ACROSS MUCH OF THE LAKE THROUGH MID MORNING BEFORE
THE PRESSURE GRADIENT EASES. SPEEDS MAY PUSH 30 KT FOR A TIME
THROUGH MID OR LATE MORNING...ESPECIALLY ACROSS CENTRAL SECTIONS OF
THE LAKE. THE LOW WILL PASS SOUTH OF THE LAKE LATER THIS AFTERNOON
AND BEGIN TO WEAKEN WITH THE HIGH WEAKENING AS WELL. ANOTHER SURFACE
LOW WILL DEVELOP OVER THE ARKLATEX SATURDAY AND LIFT NORTHEAST TO
NORTHERN OHIO BY SUNDAY AFTERNOON. A VERY STRONG HIGH WILL THEN
DEVELOP SOUTHWARD INTO THE NORTHERN PLAINS AS THE LOW MOVES INTO NEW
ENGLAND SUNDAY NIGHT. THIS WILL LEAVE LAKE MICHIGAN IN THE PRESSURE
GRADIENT BETWEEN THE TWO SYSTEMS SATURDAY NIGHT AND SUNDAY WITH
COLDER AIR SPILLING ACROSS THE LAKE AS WELL. THIS WILL SET THE STAGE
FOR ANOTHER ROUND OF STRONG WINDS WHICH WILL START OUT NORTHEAST
THEN SHIFT NORTH-NORTHWEST AND EASE UP LATE SUNDAY AFTERNOON. THE
HIGH WILL PASS SOUTH OF THE LAKE TUESDAY BEFORE LOW PRESSURE TRACKS
SOUTHEAST ACROSS THE CANADIAN PRAIRIES AND NORTHERN PLAINS. THIS
SHOULD LEAD TO ANOTHER PERIOD OF INCREASED WINDS...THIS TIME FROM
THE SOUTH AND SOUTHWEST WEDNESDAY. WILL KEEP SPEEDS BELOW GALE FORCE
THROUGH THE PERIOD BUT WILL NEED TO MONITOR FOR SHORT WINDOWS OF
GALE FORCE WINDS SATURDAY NIGHT AND SUNDAY MORNING...AND AGAIN EARLY
WEDNESDAY.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 3 PM FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
FLOOD WATCH...ILZ033-ILZ039...9 AM SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002 UNTIL 9 AM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...9 AM SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...LMZ740...9 AM FRIDAY TO 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 AM FRIDAY.
&&
$$
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AREA FORECAST DISCUSSION
NWS DODGE CITY KS
513 AM CST Fri Dec 20 2013
...Updated aviation discussion...
.SYNOPSIS...
ISSUED AT 340 AM CST FRI DEC 20 2013
An upper level trough was progressing southeastward into
northwestern Mexico and the southern Rockies early this morning
while a wedge of arctic air surged southward into the central
plains. Stratus covered western Kansas in the wake of the front,
with ceilings from 1000-2000 ft. Mid to high level winds were
generally out of the west-southwest over the central and southern
plains ahead of the southwestern system.
&&
.SHORT TERM...(Today and tonight)
ISSUED AT 340 AM CST FRI DEC 20 2013
The approaching winter weather will be covered in the long
term discussion since the vast majority of winter weather
is expected after 12z Saturday.
Cold high pressure will be centered over Nebraska and South Dakota
today, but the southern periphery of the high will be wedged into
southwestern Kansas. It is a tough call as to whether the low stratus
clouds will clear out, allowing temperatures to modify a little
today. The NAM and SREF indicate clearing with highs around 33F at
Dodge City, 30F at Hays and 36 at Elkhart, while the RAP holds
onto the stratus for areas east of Garden City, with much cooler
highs in upper teens to lower and mid 20s. Opted to go with an in
between solution due to the uncertainty, with mid to high 20s at
Hays, Dodge City and Pratt, and lower 30s in far southwestern and
Western Kansas. Some mid to high level cloud will be increasing
late today in advance of the aforementioned upper level trough. By
tonight, mid level cloud will continue to increase over southwestern
Kansas, with only limited radiational cooling in the brief clear
breaks. Temperatures should bottom out in the upper teens to lower
20s, but could be lower if temperatures stay colder today.
.LONG TERM...(Saturday through Thursday)
ISSUED AT 254 AM CST FRI DEC 20 2013
Models this morning remain in good agreement with an upper level
trough/low lifting northeast from west central Texas into western
Oklahoma on Saturday. Widespread steady precipitation is expected
by the early Saturday morning across southwest and south central
Kansas given the moisture, warm air advection, and improving
frontogenesis ahead of the approaching upper level system. The
warm air advection early Saturday will result in a wintry mix
early Saturday, however the NAM, GFS, and ECMWF still disagree
with the magnitude of warm layer aloft. At this time confidence is
low on which model may be more correct so have decided to lean
towards a compromise between the warmer GFS and the cooler NAM and
ECMWF. Based on this as a first guess and applying the top down
approach it still appears that there will be an extended period of
sleet and freezing rain across much of south central Kansas early
Saturday morning. The area more favorable for ice accumulations
currently appears to be southeast of a Stafford to Greensburg to
Ashland line. Further northwest a brief period of freezing
precipitation will be possible early Saturday, however this should
quickly change over to snow during the early morning hours.
By Saturday afternoon the atmosphere will cool enough for mainly
snow and an area of 850-700mb frontogenesis will begin to improve
across southwest Kansas. The 00z Friday model runs continue to
indicated some discrepancies with where this area of forcing will
develop, however they all agree that as frontogenesis improves the
snow will become steadier and heavier at times Saturday afternoon
and early Saturday night. Both the GFS and ECMWF continues to
highlight this area of frontogenesis will be developing near a
line from roughly Hugoton to near Dodge City to around LaCrosse.
00z NAM was further southeast. At this time given the agreement
between the GFS and ECMWF and the run to run consistency on
location of this frontogenesis have decided to stay close to the
00z GFS/ECMWF. The steadiest and heaviest snowfall appears to
occur from 18z to 06z as the forcing along the mid level
baroclinic zone strengths and remains nearly stationary. After 06z
this baroclinic zone will begin to slide east towards central
Kansas as the upper trough moves across southeast Kansas and into
Missouri. Snow accumulations of 2 to near 6 inches still appears
reasonable. Locally higher accumulations are not out of the
question from Dodge City northeast where the snow is expected to
begin sooner and the mid level forcing appears to last slightly
longer. Given that there still is some uncertainty on location and
snowfall amounts late Saturday and Saturday night have decided to
continue with the Winter Storm Watch and not upgrade to a warning
or advisory just yet.
On Sunday a weaker upper level disturbance will cross western
Kansas. Although snow is not anticipated with this next weaker
system, increasing clouds may aid in keeping temperatures down
Sunday afternoon. Based on possible cloud cover and expected
snowfall on Sunday will continue to favor the cooler MAV/MOSGUIDE
for highs given expected snow cover.
On Sunday night an area of high pressure at the surface will
start to build into Kansas from the north. As the surface ridge
axis moves into portions of western Kansas the winds will become
light and variable. Light winds and snow cover will provided
favorable conditions for temperatures to fall back to near zero
given a period of clear skies. At this time however am somewhat
concerned about some increasing clouds after midnight. As a result
will trim temperatures back into the single digits which are
cooler latest guidance.
A gradual warming trend will then begin to develop early next
week as a northwest flow backs and becomes more perpendicular to
the Rockies. How quickly temperatures will rebound early next week
is still somewhat unclear, but the latest temperature trend
currently in the forecast still appears to be on track. A cold
front crossing western Kansas mid week will end this warming trend
briefly.
&&
.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
ISSUED AT 511 AM CST FRI DEC 20 2013
Gusty north winds will decrease into the 10 to 15 knot range by
the early afternoon as an area of high pressure at the surface
builds into the central plains. Towards 00z Saturday these
north/northeast winds will begin to gradually veer to the
southeast as the surface ridge axis moves across central Kansas.
06z NAM BUFR soundings and latest HRRR both suggest that the MVFR
cigs will gradually erode between 15z and 18z and give way to vfr
cigs. Will reintroduce decreasing cigs after midnight as warm air
advection improves.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 27 20 26 19 / 10 50 100 100
GCK 28 19 27 19 / 10 30 90 90
EHA 32 21 30 22 / 10 40 80 60
LBL 30 20 28 21 / 10 50 100 100
HYS 26 19 28 17 / 0 20 80 90
P28 29 23 28 21 / 10 70 100 100
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH from late tonight through late Saturday night
FOR KSZ064>066-076>081-085>090.
&&
$$
SYNOPSIS...Finch
SHORT TERM...Finch
LONG TERM...Burgert
AVIATION...Burgert
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
608 AM CST FRI DEC 20 2013
.UPDATE...
12Z AVIATION DISCUSSION ADDED BELOW.
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CST FRI DEC 20 2013
SNOW BEGINNING TO TAPER OFF ACROSS THE AREA THIS MORNING AS WEAK
ISENTROPIC UPGLIDE WE HAD IS SLOWLY FADING AWAY. BEST EVIDENCE OF
THE LOSS OF LIFT WAS THE CONSIDERABLE AMOUNT OF WARMING WE SAW WITH
CLOUD TOP TEMPS BETWEEN 5Z AND 7Z...IR WARMING THESE TWO HOURS
MATCHED UP WELL WITH THE LOSS OF SNOW OBSERVATIONS. THERE WILL BE
ONE MORE POTENTIAL SNOW BAND TO WATCH OUT FOR THIS MORNING FROM
SOUTH CENTRAL MN TOWARD THE EAU CLAIRE AREA. LOOKING BACK OVER THE
ERN NEB/SODAK BORDER...THERE HAS BEEN A BAND OF COOLING CLOUD TOPS
THE LAST COUPLE OF HOURS...WHICH IS ASSOCIATED A SECTION OF THE
H7-H6 FGEN THAT THE RAP SHOWS BECOMING ACTIVE ONCE AGAIN. THIS IS
BEING AIDED BY A SLIGHT LOWERING OF THE TROPOPAUSE LEVEL THAT
EMANATED FROM THE PRIMARY UPPER TROUGH OVER THE ROCKIES LAST NIGHT.
THIS BAND OF FGEN WILL SLIDE EAST THROUGH THE MORNING AND MOST
HI-RES MODELS...ALONG WITH THE 20.00/20.06 NAM12 SHOW ONE LAST BAND
OF SNOW CUTTING ACROSS OR NEAR THE SE CORNER OF THE MPX CWA BETWEEN
ABOUT 14Z AND 18Z.
THE BIGGER QUESTION FOR TODAY THOUGH IS WHAT WILL HAPPEN WITH THE
CLOUD COVER. SEEING SOME CONFLICTING TRENDS WITH THE CLOUD COVER
EARLY THIS MORNING...WHICH IS HELPING MAKE THE CLOUD FORECAST RATHER
DIFFICULT. A VERY DRY HIGH PRESSURE OF CONTINENTAL POLAR ORIGIN IS
CURRENTLY CENTERED FROM CENTRAL SODAK INTO NORTH CENTRAL MN. WITHIN
THIS HIGH WE ARE SEEING CLOUD HEIGHTS INCREASE OR EVEN CLEAR OUT
ACROSS CENTRAL MN...BUT BENEATH THE RIDGE OVER SODAK...THEY HAVE
BEEN EXPANDING THE LAST FEW HOURS. OVER SRN MN...THE CLOUDS HAVE
FINALLY BEGUN TO LOWER AS SLIGHTLY MORE MOIST AIR HAS BEEN PUSHED
NORTH OF THE STALLED OUT BOUNDARY THAT SITS FROM NE OKLAHOMA INTO
SRN MICH. THE MODELS SHOW PLENTY OF LOW LEVEL MOISTURE HANGING
AROUND THROUGH THE DAY...INDICATING A MOSTLY CLOUDY DAY IS IN
STORE...BUT SUSPECT THAT DRIER AIR OVER NRN MN WILL HELP KEEP THE
CLOUDS THINNER ACROSS NRN PORTIONS OF THE AREA. THE NAM/GFS SHOW
EVEN THE LOW LEVEL MOISTURE STARTING TO EVACUATE WRN MN
TONIGHT...WITH MOSTLY CLEAR SKIES WORKING INTO THE WEST LATE. IF
THIS HAPPENS...WE WILL PROBABLY HAVE TO TREND LOWS TONIGHT IN THE
WEST CLOSER TO THE COOL END OF GUIDANCE...WHICH SHOWS LOWS DROPPING
BACK DOWN INTO THE TEENS BELOW ZERO IN THE WEST AS IS SEEN WITH
GEM/ECMWF/NAM.
AS FOR THE MOISTURE AHEAD OF THE BOUNDARY TO OUR SOUTHEAST...IT IS
QUITE IMPRESSIVE. LOW LEVEL AIR TRAJECTORIES SHOW THAT THE AIR IN
THE WARM SECTOR OF THE SYSTEM TO OUR SOUTH CAN BE TRACED BACK TO NOT
JUST THE GULF OF MEXICO...BUT CLEAR DOWN INTO THE NRN CARIBBEAN AND
BACK EAST ACROSS CUBA INTO THE TROPICAL WRN ATLANTIC...HENCE WHY
HISTORIC RAINFALLS ARE EXPECTED IN THE COMING DAYS ACROSS THE OHIO
VALLEY.
.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 400 AM CST FRI DEC 20 2013
THE ARCTIC FRONT WILL OSCILLATE BACK AND FORTH ACROSS THE FORECAST
AREA DURING THE LONGER TERM. THIS WILL OFFER AT LEAST TWO SNOW
EVENTS AS WAVES OF LOW PRESSURE MOVE THROUGH FROM SUNDAY INTO
MONDAY AND THEN FROM TUESDAY INTO WEDNESDAY. SNOW ACCUMULATIONS OF AN
INCH OR TWO ARE POSSIBLE WITH EACH EVENT. FAIRLY STRONG HIGH
PRESSURE WILL FOLLOW EACH OF THESE WAVES. MONDAY MORNING STILL
LOOKS THE COLDEST WITH LOWS FROM NEAR 20 BELOW IN WEST CENTRAL MN
TO AROUND ZERO AT KEAU. COUPLE THIS WITH NORTHWEST WINDS NEAR 10
MPH AND WIND CHILL READINGS COME OUT TO AROUND 35 BELOW ZERO
ACROSS THE WESTERN CWA. HIGHS ON MONDAY WILL LIKELY STAY BELOW
ZERO ACROSS THE WEST WITH SINGLE DIGITS ABOVE ZERO FOR THE TWIN
CITIES AND WEST CENTRAL WI. A NON-DIURNAL TEMPERATURE TREND WAS
THEN INSERTED FOR MONDAY NIGHT ACROSS WEST CENTRAL AND SOUTHWEST
MN AS SOUTHERLY FLOW INCREASES ON THE BACK SIDE OF THE HIGH AS THE
NEXT WAVE OF LOW PRESSURE MOVES INTO THE DAKOTAS. CENTRAL AREAS OF
MN AND WEST CENTRAL WI WILL STILL HAVE A VERY COLD NIGHT WITH LOWS
MONDAY NIGHT FROM 10 BELOW TO 15 BELOW ZERO. THE WAVE OF LOW
PRESSURE ARRIVING ON TUESDAY POSES SOME PRECIP TYPE PROBLEMS FOR
SOUTHWEST MN WITH THE GFS INDICATING SOME POTENTIAL FOR FREEZING
DRIZZLE/FREEZING RAIN. THE ECMWF IS NOT AS AGGRESSIVE WITH THE LOW
LEVEL WARMING...PARTLY BECAUSE THE WHOLE UPPER WAVE IS FARTHER
SOUTH COMPARED TO THE GFS. THE ECMWF HAS DEEPER SATURATION AS
WELL. POPS FOR THE TUESDAY AND WEDNESDAY PERIOD WILL LIKELY NEED
TO BE ADJUSTED UPWARD IF THE POSITION OF THE GFS GETS CLOSER TO
THE ECMWF. POPS WERE EXPANDED AND ADJUSTED UPWARD FOR THE WAVE
FROM SUNDAY INTO MONDAY AS THE NORTHERN STREAM HAS BECOME
STRONGER. THE OTHER PROBLEM ON SUNDAY TO KEEP AN EYE ON IS THE
BLOWING SNOW FROM WEST CENTRAL INTO SOUTH CENTRAL MN. WITH MORE
WIDESPREAD SNOW FORECAST ALONG WITH INCREASING NORTHWEST WINDS AS
THE NEXT SURGE OF ARCTIC PUSHES IN...SOME PRETTY POOR VISIBILITIES
MAY RESULT ACROSS THE MN RIVER VALLEY DURING THE AFTERNOON AND NIGHT.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 539 AM CST FRI DEC 20 2013
LOW CONFIDENCE CIG FORECAST THIS PERIOD. MODEL FOLLOWED CLOSEST
FOR THIS PACKAGE WAS THE TREND FROM THE SREF FOR CIGS LESS THAN 3K
FEET...WHICH HAS A GOOD HANDEL OUT THE GATE ANYWAYS OF THE
CONFIGURATION OF MVFR CIGS ACROSS SRN MN...THEN UP THE MN/SD
BORDER. THOUGH WE HAVE SEEN CLEARING ACROSS CENTRAL MN...CLOUDS
HAVE BEEN FILLING BACK IN FOR THE LAST HOUR AND CURRENT TRENDS
WOULD INDICATE AXN WILL CLOUD BACK IN SHORTLY THIS MORNING. AFTER
THAT...NOT REALLY SEEING A STRONG SIGNAL FOR CLOUDS TO START
CLEARING OUT UNTIL AFTER 6Z ACROSS WRN MN. EXPECT CIGS TO BE MVFR
AT WORST...THOUGH IFR CIGS CAN NOT BE RULED OUT THIS EVENING AT
EAU AS THIS IS WHERE MODELS PEG DEWPOINTS TO INCREASE TO NEAR 20
DEGS THIS AFTERNOON. THAT EXTRA LOW LEVEL MOISTURE TONIGHT MAY
ALLOW FOR CIGS TO DROP TO IFR LEVELS. AS FOR SNOW...CONFIDENCE IS
HIGH THAT IT IS FINISHED FOR ALL TERMINALS.
KMSP...EXPECT CLOUDY CONDITIONS TO PREVAIL TODAY WITH THE MAIN
QUESTION BEING WHEN/IF THOSE CIGS COME BACK TO MVFR LEVELS. MAY
COME EARLIER THAN CURRENTLY INDICATED...BUT HAVE 00Z BASED ON WHEN
SREF PROBS FOR CIGS LESS THAN 3K FT INCREASE...WHICH IS COINCIDENT
WITH MEAN 925-850MB WIND SWITCHING OVER THE SW...HELPING BRING THE
LOWER CIGS THAT WILL BE DOWN TOWARD IA BACK TOWARD MSP. FOR NOW
HAVE CIGS REMAINING ABOVE 017...BUT COULD CERTAINLY SEE THEM DIP
BELOW THAT LEVEL TONIGHT.
/OUTLOOK FOR KMSP/
SAT...BECOMING VFR. WNDS LGT AND VRB.
SUN...MVFR CIGS/VSBYS POSSIBLE WITH -SN. WNDS WNW 15-20G25-30KT.
MON...VFR. WINDS NW 5-10 KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
SHORT TERM...MPG
LONG TERM...RAH
AVIATION...MPG
AREA FORECAST DISCUSSION...UPDATED
NWS ST LOUIS MO
926 AM CST Fri Dec 20 2013
.UPDATE:
Issued at 924 AM CST Fri Dec 20 2013
Strong cold front continues to plod east, a bit slower than going
forecast. Have updated movement to blend with latest RUC guidance,
with an uptick in high temps ahead of the slow moving but strong
thermal gradient. Have also continued mention of light rain near
and ahead of the boundary. Updated zones out in a second.
Truett
&&
.SHORT TERM: (Through Late This Afternoon)
Issued at 421 AM CST Fri Dec 20 2013
The cold front has just passed through KUIN and KMBY at 10z and
will continue to move southward throughout the day, especially as
the surface low now in west central MO lifts by the area.
Temperatures will fall in its wake, with some rise ahead of the
front and values into the lower 60s expected across southern
sections of the CWA. Precipitation thus far has been scattered/spotty
and primarily confined to the warm sector and am anticipating that
to continue.
Glass
.LONG TERM: (Tonight through Thursday)
Issued at 421 AM CST Fri Dec 20 2013
The cold front will become quasi-stationary this evening from the
Ohio Valley through the lower MS valley into the southern Plains.
A strong overunning pattern will become established this evening
as the low level jet provides lift and rich moisture transport
into the cool sector. This coupled with low-mid level frontogenetic
forcing and the development of a coupled ULJ structure later
tonight will result in strong ascent and the northward spread of
precipitation into the cold air. Precipitation will expand even
further north on Saturday as the low-mid level flow backs in response
to the southern stream upper low/trof ejecting northeastward.
Present indications are the southward extent of freezing air will
be greater than previously thought and there will be potential for
a quarter inch and greater of ice accumulation from central MO
into NE MO and west central IL beginning later tonight through the
day on Saturday and into Saturday evening. Complicating the ice
forecast is the freezing line could waver north and south on
Saturday and Saturday evening. As the upper low/trof ejects
rapidly northeastward from western OK across northern MO on
Saturday night it should spread a band of heavy snow from eastern
KS across NW MO into SE IA with northeast Missouri potentially
seeing 2-4 inches on the southern end of this band and the
stronger ascent. A winter storm watch has been issued primarily
for the potential for signficant ice accumulations across the
northeast third of the CWA. Lastly, presistent rain across the
southeast third of the area tonight through Saturday evening is
expected to result in anywhere from 2-4 inches of rainfall which
could bring flooding problems to some of the rivers and small
streams, and lots of standing water. The flood watch continues in
this area.
Glass
&&
.AVIATION: (For the 12z TAFs through 12z Saturday Morning)
Issued at 637 AM CST Fri Dec 20 2013
Cold front is making it way southeast across forecast area today,
then will stall out just south of forecast area. As of 12z, it was
south of KUIN. The front will move through KCOU by 13z and metro
area by 18z-19z timeframe. As front approaches taf sites, cigs to
lower to ifr with scattered light rain and patchy fog. Then
precipitation to taper off by midday most locations, but cigs to
remain ifr through rest of forecast period. Will see another round
of precipitation early this evening and persist through rest of
forecast period for sites along I-70 corridor. For KCOU, the
temperatures will be below freezing so will see some light
freezing rain while metro area to remain above freezing. As for
winds, south winds to veer to the northwest to north behind the
frontal boundary.
Specifics for KSTL:
Cold front is making it way southeast across region today, then will
stall out just south of forecast area. As of 12z, it was south of
KUIN. The front will move through metro area between 18z-19z. As
front approaches KSTL, cigs to lower to ifr with scattered light
rain and patchy fog by 18z. Then precipitation to taper off by
22z, but cigs to remain ifr through rest of forecast period. Will
see another round of precipitation after 01z and remain over area
through rest of forecast period. Temperatures will remain above
freezing tonight so precipitation will be all rain. As for winds,
south winds to veer to the northwest to north behind the frontal
boundary.
Byrd
&&
.HYDROLOGY:
Issued at 407 PM CST Thu Dec 19 2013
Based on this morning`s QPF ensemble from WPC, our 72-hour
contingency forecasts (forecasts based on an uncertain 72 hours of
QPF) indicate the most likely outcomes across the Meramec, Big,
Bourbeuse, Black, and Kaskaskia basins are either minor flooding or
crests a little below flood stage. No flooding is most likely in
basins to the north of I-70. Minor flood crests were indicated
along the upper Meramec River at Steelville and Sullivan and on the
Black River near Annapolis.
Fuchs
&&
.LSX WATCHES/WARNINGS/ADVISORIES:
MO...FLOOD WATCH from 6 PM CST this evening through Saturday evening
FOR Crawford MO-Franklin MO-Gasconade MO-Iron MO-Jefferson
MO-Madison MO-Osage MO-Reynolds MO-St. Charles MO-St.
Francois MO-St. Louis City MO-St. Louis MO-Ste. Genevieve
MO-Warren MO-Washington MO.
WINTER STORM WATCH from 6 PM CST this evening through late
Saturday night FOR Audrain MO-Boone MO-Callaway MO-Cole MO-
Moniteau MO-Montgomery MO.
WINTER STORM WATCH from Saturday morning through late Saturday
night FOR Knox MO-Lewis MO-Marion MO-Monroe MO-Pike MO-
Ralls MO-Shelby MO.
IL...FLOOD WATCH from 6 PM CST this evening through Saturday evening
FOR Bond IL-Clinton IL-Fayette IL-Jersey IL-Macoupin IL-
Madison IL-Marion IL-Monroe IL-Montgomery IL-Randolph IL-
St. Clair IL-Washington IL.
WINTER STORM WATCH from Saturday morning through late Saturday
night FOR Adams IL-Brown IL-Pike IL.
&&
$$
WFO LSX
AREA FORECAST DISCUSSION
NWS PORTLAND OR
321 AM PST FRI DEC 20 2013
.SYNOPSIS...LIGHT SNOW IS BEGINNING TO MOVE INTO WASHINGTON EARLY
THIS MORNING...AND IS EXPECTED TO SPREAD SOUTHWARD AND INLAND INTO
THE FORECAST AREA OVER THE NEXT FEW HOURS. THIS IS ASSOCIATED WITH A
WARM FRONT AND ONSHORE FLOW DEVELOPING OVER THE COLD AIR MASS THAT IS
ALREADY IN PLACE. EVENTUALLY...ENOUGH MILD PACIFIC AIR WILL MOVE IN
ALOFT TO CHANGE PRECIPITATION TO A BRIEF PERIOD OF SLEET OR FREEZING
RAIN THEN ALL RAIN FOR MOST AREAS BY MIDDAY. RAIN WILL CONTINUE INTO
TONIGHT...THEN DECREASE INTO SATURDAY. NORTHWEST FLOW ALOFT WILL KEEP
A CHANCE FOR RAIN THROUGH THE WEEKEND. A GULF OF ALASKA COLD FRONT
WILL BRING MORE ORGANIZED RAIN TO THE DISTRICT MONDAY... FOLLOWED BY
DRIER WEATHER FOR THE REST OF THE WEEK.
&&
.SHORT TERM...TODAY THROUGH SUNDAY...A NAILBITER OF A FORECAST THIS
MORNING...WITH POTENTIAL FOR A WINTRY MIX OF PRECIPITATION TO IMPACT
THE MORNING COMMUTE FOR A LARGE PORTION OF SOUTHWEST WASHINGTON AND
NORTHWEST OREGON. EVEN WITH PRECIPITATION EXPECTED TO ARRIVE WITHIN
THE NEXT FEW HOURS...QUESTIONS REMAIN REGARDING THE PREDOMINANT
PRECIPITATION TYPE THIS MORNING.
RADAR AND SURFACE OBSERVATIONS...AS WELL AS SOME WEBCAMS ARE
INDICATING LIGHT SNOW SPREADING ONSHORE INTO WASHINGTON AS A WARM
FRONT APPROACHES THE COAST. ISENTROPIC LIFT IS BEGINNING TO INCREASE
JUST OFFSHORE OF OUR FORECAST AREA...WITH RADAR ECHOES COMING CLOSE
TO THE PACIFIC COUNTY COAST. EXPECT LIGHT PRECIPITATION WILL BEGIN
WITHIN THE NEXT HOUR OR TWO THERE...THEN SPREAD INLAND AND SOUTH INTO
OREGON BY SUNRISE.
TEMPERATURES ARE GENERALLY RIGHT AROUND FREEZING FOR ALL BUT THE
IMMEDIATE COAST. TEMPS HAVE CREPT UP SLIGHTLY ACROSS THE PORTLAND AND
VANCOUVER METRO AREA AFTER A QUICK DROP BELOW FREEZING EARLIER IN THE
EVENING. KPTV TOWER TEMPS REMAIN ALL BELOW FREEZING...HOWEVER WE HAVE
REACHED 33 DEGREES HERE AT THE OFFICE IN PARKROSE AND MOST OF
DOWNTOWN PORTLAND/VANCOUVER IS 33-34 DEGREES. HOWEVER OUTLYING AREAS
OF BOTH PORTLAND AND VANCOUVER REMAIN IN THE 30-32 DEGREE RANGE AS
PRECIPITATION APPROACHES. MUCH COLDER TEMPS EXIST IN THE CASCADE
VALLEYS...WHICH WILL COME INTO PLAY AS PRECIPITATION ARRIVES
ESPECIALLY FOR THE SOUTH WASHINGTON CASCADES.
00Z UW WRF-GFS SOUNDINGS AND LATEST HRRR PRECIPITATION-TYPE
ALGORITHMS ALL SUGGEST ENOUGH OF A WET BULB EFFECT WILL OCCUR TO
CAUSE PRECIPITATION TO START OFF AS SNOW AS IT ARRIVES EARLY THIS
MORNING. SIGNIFICANT SNOW IS LESS LIKELY SOUTH OF PORTLAND SIMPLY
BECAUSE PRECIPITATION WILL BE LIGHTER TO NON-EXISTENT DURING THE
FIRST FEW HOURS OF THIS MORNING. AREAS SALEM NORTHWARD STAND A CHANCE
TO SEE AT LEAST SOME FLAKES IN THE AIR DURING THE MORNING
COMMUTE...BUT THE BEST CHANCE FOR ACCUMULATING SNOW WILL BE NORTH OF
THE COLUMBIA RIVER. MOST MODELS ARE SHOWING 0.10-0.20 INCH OF QPF
ACROSS SW WASHINGTON THIS MORNING WITH AMOUNTS DROPPING OFF TO THE
SOUTH. THIS WOULD RESULT IN A QUICK 1-2 INCHES OF SNOW DURING THE
MORNING COMMUTE...MAINLY NORTHERN CLARK COUNTY AND AREAS NORTH.
DECIDED TO ISSUE A WINTER WX ADVISORY FOR THE GREATER VANCOUVER METRO
AREA...LOWER COLUMBIA AND I-5 CORRIDOR IN COWLITZ CO AS A
RESULT...BUT WE LEFT THE NORTH WILLAMETTE VALLEY ZONE OUT OF IT AS
ACCUMULATIONS ARE EXPECTED TO BE LESS THAN AN INCH BEFORE CHANGEOVER.
SNOW SHOULD ARRIVE IN KELSO-LONGVIEW BETWEEN 4-430 AM...THEN SPREAD
INTO CLARK COUNTY BY 530 AM. LOOKING AT INFRARED IMAGERY IT APPEARS A
MORE SUBSTANTIAL BATCH OF PRECIPITATION EXTENDS SW FROM
QUILLAYUTE...THIS WILL BE WHAT EVENTUALLY MAKES IT EAST OF THE COAST
RANGE AS IT PUSHES SOUTHEAST. OBVIOUSLY...WILL NEED TO WATCH THIS
BAND CLOSELY FOR THE PORTLAND AREA AS WELL. THERE MAY BE A BRIEF MIX
OF SNOW AND RAIN BEFORE WET-BULBING TURNS PRECIP OVER TO SNOW.
MODELS ARE UNANIMOUS IN PUSHING A MID-LEVEL WARM FRONT QUICKLY
THROUGH THE FORECAST AREA BETWEEN 7-9 AM...WHILE THE SURFACE FRONT
WILL TAKE LONGER. THIS WILL RESULT IN A TRANSITION TO SLEET AND
RAIN...WITH FREEZING RAIN LIKELY IN THE MOST SHELTERED VALLEYS. SNOW
LEVELS WILL SHOOT UP TO 5000-7000 FEET ALMOST INSTANTLY BEHIND THE
MID-LEVEL FRONT.
DUE TO THE MOUNTAIN VALLEY FREEZING RAIN THREAT WE ALSO EXPANDED THE
WINTER WEATHER ADVISORY INTO THE S WA CASCADES. ALSO CONCERNED ABOUT
THE NEHALEM RIVER VALLEY SO WE INCLUDED THE NORTH OREGON COAST RANGE.
THE GREATEST ICE ACCUMULATIONS WILL PROBABLY BE IN THE WIND RIVER AND
UPPER HOOD RIVER VALLEYS...WHERE COLD AIR WILL REMAIN LOCKED IN THE
LONGEST. A COUPLE SPOTS COULD GET A QUARTER INCH OF ICE...BUT MOST
SHOULD SEE ONE TENTH OF AN INCH OR LESS. THE BROADER INTERIOR
LOWLANDS SUCH AS THE WILLAMETTE VALLEY WILL PROBABLY NOT SEE
SIGNIFICANT ICE ACCUMULATIONS EXCEPT PERHAPS A FEW POCKETS IN
NORTHERN CLARK COUNTY LIKE YACOLT.
EVERYTHING SHOULD CHANGE TO PLAIN RAIN MOST AREAS BY 10 AM...WITH ANY
LINGERING POCKETS OF FREEZING RAIN LIKELY ENDING IN THE CASCADE
VALLEYS AND CENTRAL GORGE BY MID AFTERNOON. DECIDED TO SHORTEN THE
ADVISORIES FOR THE CENTRAL GORGE AND UPPER HOOD RIVER VALLEY FOR THIS
REASON.
ONCE PRECIPITATION CHANGES TO RAIN...THIS WILL JUST BE A TYPICAL
DECENT RAIN EVENT FOR MUCH OF THE AREA WITH 1 TO 2 INCHES ALONG THE
COAST AND IN THE HIGHER TERRAIN AND ABOUT 0.5 INCH IN THE VALLEYS
BEFORE PRECIPITATION EASES LATER FRIDAY NIGHT. SOUTH WINDS WILL BE
BREEZY THIS AFTERNOON WITH GUSTS 25-35 MPH IN THE LOWLANDS.
MOISTURE WILL CONTINUE RIDING OVER THE UPPER RIDGE AND INTO THE
PACIFIC NORTHWEST THROUGH THE WEEKEND...BUT THE MOISTURE WILL BE LESS
ORGANIZED. THUS EXPECTED MAINLY SOME OCCASIONAL LIGHT RAIN ESPECIALLY
OVER THE NORTHERN FORECAST ZONES THROUGH THE WEEKEND. TEMPS REMAIN
REASONABLY MILD FOR THIS TIME OF YEAR. PERHAPS A BIT OF NIGHT AND
MORNING FOG...ESPECIALLY SOUTH VALLEY AREAS. THE NEXT FRONT IS LATE
MONDAY AND MONDAY NIGHT. WEAGLE
.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS.
SUNDAY NIGHT THROUGH CHRISTMAS DAY...UPPER LEVEL RIDGING OVER THE
EPAC WILL DOMINATE MUCH OF THE EXTENDED FORECAST. THIS WILL CONTINUE
GENERAL NORTHWESTERLY UPPER LEVEL FLOW THROUGH THE PERIOD...AND
PREVENT ANY SUBSTANTIAL SYSTEMS FROM AFFECTING THE AREA. WEAK WARM
FRONT EXITS SUNDAY NIGHT AND IS FOLLOWED BY A DECAYING COLD FRONT ON
MONDAY. THE COLD FRONT WILL WEAKEN AS IT MOVES INLAND...THEREFORE
EXPECT PRECIP TO GENERALLY REMAIN CONFINED TO THE MORE NORTHERN
AREAS OF THE CWA. TUESDAY THE UPPER RIDGE SHIFTS EAST A BIT...
PLACING THE RIDGE AXIS OVER THE PAC NW BY WEDNESDAY. EXPECT
INCREASINGLY DRY AND COOL CONDITIONS FOR CHRISTMAS EVE ONWARD.
BURGESS
&&
.AVIATION...BRIEF LOCAL MVFR AND IFR LOW STRATUS/FOG WILL PERSIST
FOR INLAND SITES THE NEXT FEW HOURS UNTIL PRECIP AND MID LEVEL
CLOUDS SPREADS INLAND. LIGHT SNOW BEING REPORTED EARLY THIS
MORNING AT KUIL...SO STILL EXPECTING THE THREAT FOR SNOW TO BEGIN
AROUND 12Z-14Z...FOLLOWED BY RAIN/SLEET/FREEZING RAIN MIX. IT
WILL BE A QUICK TRANSITION TO SOLID RAIN AROUND 18Z-20Z THIS
MORNING ONCE S WINDS BEGIN TO WARM THE AIR MASS. MIX OF VFR AND MVFR
CONDITIONS WITH CIGS AROUND 3K FT WILL PREVAIL AFTER 20Z THROUGH
LATE TONIGHT IN RAIN AND ABOVE FREEZING TEMPERATURES.
KPDX AND APPROACHES...MAIN THREAT FOR SNOW ARRIVES AROUND 13Z-14Z
THIS MORNING WITH IFR CONDITIONS POSSIBLE...TRANSITIONING TO A
SNOW/SLEET/RAIN MIX BY 16Z. WARMER AIR ALOFT AND S WINDS WILL
BEGIN TO WARM AIR MASS BY 18Z AT THE LATEST. MVFR CIGS IN SOLID
RAIN WILL CONTINUE AFTERWARDS. /27
&&
.MARINE...RATHER QUIET CONDITIONS THROUGH EARLY THIS MORNING THEN
EXPECT INCREASING WINDS AND SEAS TODAY AND TONIGHT WITH AN
APPROACHING FRONT. SOUTH WINDS WILL INCREASE LATER THIS MORNING
WITH SOLID GUSTS 20-25 KTS. POST FRONTAL GALE FORCE GUSTS TO 35
KT CAN BE EXPECTED MUCH OF TODAY...MADE THE DECISION TO ISSUE A
GALE WARNING FOR GUSTS ACROSS THE WATERS DUE TO THE TIME OF DAY
THE GUSTS WILL IMPACT THE WATERS SINCE THERE MAY BE INCREASED
ACTIVITY. IT WILL BE A MARGINAL EVENT...BUT MODELS ARE SUGGESTING
MORE FREQUENT GUSTS THAN PREVIOUS RUNS. /27
WINDS TURN TO HARD WEST IN THE AFTERNOON AS THE FRONT PUSHES
INLAND...BUT GUSTY WINDS WINDS CONTINUE. SEAS WILL BE ON THE
REBOUND TODAY...BACK ABOVE 10 FT BY LATER THIS MORNING. SEAS WILL
PUSH TO 11 TO 14 FT BY THIS EVENING...WITH HIGHEST OVER THE OUTER
N WATERS. UNSETTLED WEATHER CONTINUES INTO NEXT WEEK...WITH SEAS
RUNNING NEAR 10 FT OR HIGHER AT TIMES. ROCKEY.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY UNTIL 2 PM PST THIS AFTERNOON FOR UPPER
HOOD RIVER VALLEY.
WINTER WEATHER ADVISORY UNTIL NOON PST TODAY FOR CENTRAL
COLUMBIA RIVER GORGE-WESTERN COLUMBIA RIVER GORGE.
WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR COAST
RANGE OF NORTHWEST OREGON-LOWER COLUMBIA.
WA...WINTER WEATHER ADVISORY UNTIL NOON PST TODAY FOR CENTRAL
COLUMBIA RIVER GORGE-WESTERN COLUMBIA RIVER GORGE.
WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR
GREATER VANCOUVER AREA.
WINTER WEATHER ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR SOUTH
WASHINGTON CASCADE FOOTHILLS-SOUTH WASHINGTON CASCADES.
WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR I-5
CORRIDOR IN COWLITZ COUNTY.
PZ...GALE WARNING FROM 9 AM THIS MORNING TO 7 PM PST THIS EVENING
FOR COASTAL WATERS FROM CAPE SHOALWATER TO FLORENCE OUT 60 NM.
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 3 PM
THIS AFTERNOON TO 9 PM PST THIS EVENING.
&&
$$
MORE WEATHER INFORMATION ONLINE AT..
HTTP://WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV
WWW.TWITTER.COM/NWSPORTLAND
THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
535 AM CST FRI DEC 20 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 405 AM CST FRI DEC 20 2013
FREEZING DRIZZLE/RAIN HAVE CAUSED SOME PROBLEMS FROM SLIGHTLY
NORTH OF I-90 IN WI...WEST TO JUST OUTSIDE OF ROCHESTER DOWNTOWN
AREA...THEN SOUTH. ACCIDENTS WERE PLENTIFUL...ROAD CREWS HAVE
BEEN OUT WORKING. THE CHALLENGE NOW IS WHAT WILL TODAY LOOK LIKE
AND WHAT TO DO WITH THE IMPACT AND ADVISORY.
GOES WATER VAPOR SHOWING SHORTWAVE TROUGH ENERGY ON A NW-SE AXIS
CENTERED NEAR ABOUT TOPEKA...RIDING NORTHEAST AT THE AREA.
PRESSURES HAVE BEEN RISING OVER THE FORECAST AREA AND COLD AIR
ADVECTION IS DECREASING TEMPERATURES /ABOUT 1F PER HOUR/ DESPITE
SOME PRECIPITATION. TO THE SOUTH ALONG THE FRONTAL BOUNDARY...FROM
THE QUAD CITIES TO SOUTH OF CHICAGO...SURFACE PRESSURES HAVE BEEN
WEAKLY FALLING WITH UPPER WAVE FORCING. SURFACE LOW CENTER IS
CLOSER TO WICHITA AT 08Z. WEAK 700-600MB-CENTERED FRONTOGENETIC
FORCING IS LOCATED ACROSS THE NORTHERN FORECAST ARE YIELDING THE
LINEAR SNOW BAND. THIS HAS SEEDED THE LOW-LEVEL 3-4KFT SUPERCOOLED
LIQUID LAYER /FINALLY/ TO CHANGE THE FZDZ/FZRA TO SNOW.
THE TREND TODAY IN THE RAP FRONTOGENESIS IS TO SHIFT
EASTWARD FROM ABOUT WHERE IT IS NOW...WITHOUT MUCH MORE SOUTHWARD
PROGRESSION...EXITING BY 15Z. 20.06Z NAM HAS VERY SIMILAR
GUIDANCE...HOWEVER THE BAND WOULD SHIFT A BIT FURTHER SOUTH. SINCE
THIS IS THE SEEDER CLOUD...IT DETERMINES THE NORTHERN EXTENT OF
THE FZRA/FZDZ AREA. TO THE SOUTH...ABOUT A 2KM DEEP SUPERCOOLED
LIQUID LAYER EXISTS. RADAR HAS SHOWN SOME DECREASE IN EITHER THE
DEPTH OR LIQUID DROP SIZE OVER THE PAST HOURS IN THE DRIZZLE LAYER
WITH LESS REFLECTIVITY. THIS MAKES FOR PAUSE ON THE ADVISORY. BUT ANOTHER
AREA OF FZRA SHOWERS ARE HEADING IN FROM ERN IOWA...WITH MORE INTO
NRN MO...SO NO SHORTAGE OF INSTABILITY SHOWERS HEADING THIS WAY.
WITH UPSTREAM ENERGY AND LIFT SHIFTING INTO THE AREA...FELT THE
NEED TO EXTEND /IN TIME/ THE FREEZING RAIN ADVISORY...SOUTH OF
THE SNOW BAND...WHERE MORE ICE CAN BE EXPECTED THIS MORNING. WHILE
THE LIFT IS NOTHING LIKE LAST EVENING...THE SURFACE LOW SHIFTING
TO THE SOUTH OF THE AREA WITH DEFORMATION IN THE LOW-LEVELS OVER
NERN IA AND SRN WI MEAN FZRA/FZDZ COULD CONTINUE. MODEL GUIDANCE
ALSO SUGGESTS A WEAK INVERTED TROUGH EMANATING NW FROM THE
SURFACE LOW TO ENHANCE LOW-LEVEL VERTICAL MOTION...ENHANCING CLOUD
DROP GROWTH FOR DRIZZLE. THE LATEST HRRR RUNS HAVE THIS
SUGGESTION...ESPECIALLY LATER ACROSS THE SOUTHERN COUNTIES. THE
SNOW BAND SHOULD ONLY MOVE ABOUT ONE MORE COUNTY SOUTH BEFORE
SHIFTING EAST...AND AGAIN ALLOWING FOR AN ALL LIQUID PRECIPITATION
TYPE. HOWEVER...BEING FURTHER NORTH...THE LIFT IS SOMEWHAT MORE
LIMITED AND THE THREAT ALSO MORE LIMITED /I-90 ROUGHLY/.
THEREFORE...THINK THERE IS ADDITIONAL THREAT FOR FREEZING
PRECIPITATION...ESPECIALLY ACROSS THE SOUTH...THROUGH THE DAY.
WILL EXTENDED THE FREEZING RAIN ADVISORY IN EXTREME NERN IA AND
SWRN WI UNTIL 3PM...AND AREAS NORTH UNTIL 18Z. WILL CANCEL THE
FREEZING RAIN ADVISORY IN AREAS IT IS NOW SNOWING. CONFIDENCE IS
LOW IN THAT NORTHERN AREA...IF THERE WILL BE ENOUGH VERTICAL
MOTION TO CAUSE FZDZ TODAY...BUT IF NEEDED IT CAN BE CANCELLED
EARLY. ICING LOOKS TO BE ABOUT ANOTHER 0.05 INCHES ACROSS THE
SOUTHERN AREA...BEFORE DIMINISHING LATER.
.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 405 AM CST FRI DEC 20 2013
SATURDAY SEEMS TO BE AN IN BETWEEN DAY BEFORE THE STRONG CYCLONE
OVER THE SWRN U.S. CURRENTLY...SHIFTS TOWARD THE GREAT LAKES.
CLOUD TO GROUND LIGHTNING STRIKES WERE SEEN OVERNIGHT IN AZ WHICH
IN THE WEST...USUALLY HAPPENS ONLY WITH THE STRONGEST IMPULSES. SO
THIS IS A NICE SHORTWAVE TROUGH. THERE ARE A NUMBER OF FAVORABLE
DYNAMICS WITH THIS SYSTEM THAT SHIFT IN...INCLUDING AN INTENSE
160KT+ JET THAT DEVELOPS OVER SRN CANADA AS THE RIDGE BUILDS
DOWNSTREAM OF THE SHORTWAVE EJECTING INTO THE PLAINS. THIS IS
CLASSIC FOR MIDWESTERN HEAVY SNOWFALL CLIMATOLOGY. THIS PLACES A
VERY FAVORABLE ENTRANCE REGION OVER IL/SRN WI SAT NIGHT AND
SUNDAY. A VERY WARM AND MOIST SECTOR /SPC MDT RISK/ WILL BE RIDING
NORTH OUT OF THE GULF ON 50-60KT LOW-LEVEL WINDS AS INFLOW TO THE
FORCING...WHICH IS STRONG QVECTOR CONVERGENCE ALOFT AS
EXPECTED...TO THE SOUTHEAST. THIS STORM WILL PRODUCE HEAVY
SNOWFALL...THE QUESTION IS LOCATION.
WHILE THE WPC WINTER WEATHER DESK CONFIDENCE IS LOWER...IT SEEMS
THE MODELS ARE DRAWING IN ON A SOLUTION THAT WOULD PLACE THE HEAVY
SNOW BAND JUST INTO GRANT COUNTY. THIS WAS VERY CLOSE TO THE
ONGOING FORECAST SO REALLY ONLY MINOR CHANGES WERE MADE. THE NAM
SOLUTIONS STILL SEEM OUT TO LUNCH COMPARED TO THE OTHER
DETERMINISTIC MODELS...A DRY AND EAST OUTLIER. OVERALL...WILL
KEEP THE WATCH UNTIL CONFIDENCE GROWS ON THE LOCATION...BUT THE
REGION WILL SEE A 7-10 INCH SNOW BAND FROM THIS SYSTEM.
WILL BE MONITORING FOR POSSIBLE CHRISTMAS DAY WEATHER ON THE WARM
AIR ADVECTION SHIFTING IN...AFTER THE MONDAY AND MONDAY NIGHT
COOL DOWN POST STORM. THE 20.00Z ECMWF IS A BIT MORE AGGRESSIVE ON
HOLIDAY WEATHER...WE WILL SEE.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 535 AM CST FRI DEC 20 2013
A BAND OF LIGHT SNOW HAS MOVED OVER THE KRST/KLSE TAF SITES WITHIN
THE LAST COUPLE OF HOURS. EXPECTING THIS SNOW TO TAPER OFF BY 15Z.
CONCERNED THAT THERE COULD STILL BE SOME VERY LIGHT FZDZ ONCE THE
SNOW BAND TAPERS OFF...MAINLY AT KLSE TIL NOON. PLAN ON LESS THAN
AN INCH OF SNOW ACCUMULATION. WILL HAVE TO WATCH POTENTIAL FOR
FREEZING DRIZZLE INTO THIS AFTERNOON DUE TO A VERY SATURATED BOUNDARY
LAYER WITH CONTINUED LIFT AS A LINGERING TROUGH OF LOW PRESSURE
REMAINS OVERHEAD. EXPECTING PRECIPITATION TO SHOVE OFF TO THE EAST
BY THIS EVENING AS HIGH PRESSURE BEGINS TO BUILD IN.
OTHERWISE...EXPECT MVFR CONDITIONS THROUGH THE PERIOD.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL NOON CST TODAY FOR WIZ041>044-053.
FREEZING RAIN ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR WIZ054-
055-061.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ043-044-053>055-061.
MN...FREEZING RAIN ADVISORY UNTIL NOON CST TODAY FOR MNZ095-096.
IA...FREEZING RAIN ADVISORY UNTIL NOON CST TODAY FOR IAZ008>010-018-
019.
FREEZING RAIN ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR IAZ011-
029-030.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR IAZ011-029-030.
&&
$$
SHORT TERM...BAUMGARDT
LONG TERM...BAUMGARDT
AVIATION...DAS
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
405 AM CST FRI DEC 20 2013
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 405 AM CST FRI DEC 20 2013
FREEZING DRIZZLE/RAIN HAVE CAUSED SOME PROBLEMS FROM SLIGHTLY
NORTH OF I-90 IN WI...WEST TO JUST OUTSIDE OF ROCHESTER DOWNTOWN
AREA...THEN SOUTH. ACCIDENTS WERE PLENTIFUL...ROAD CREWS HAVE
BEEN OUT WORKING. THE CHALLENGE NOW IS WHAT WILL TODAY LOOK LIKE
AND WHAT TO DO WITH THE IMPACT AND ADVISORY.
GOES WATER VAPOR SHOWING SHORTWAVE TROUGH ENERGY ON A NW-SE AXIS
CENTERED NEAR ABOUT TOPEKA...RIDING NORTHEAST AT THE AREA.
PRESSURES HAVE BEEN RISING OVER THE FORECAST AREA AND COLD AIR
ADVECTION IS DECREASING TEMPERATURES /ABOUT 1F PER HOUR/ DESPITE
SOME PRECIPITATION. TO THE SOUTH ALONG THE FRONTAL BOUNDARY...FROM
THE QUAD CITIES TO SOUTH OF CHICAGO...SURFACE PRESSURES HAVE BEEN
WEAKLY FALLING WITH UPPER WAVE FORCING. SURFACE LOW CENTER IS
CLOSER TO WICHITA AT 08Z. WEAK 700-600MB-CENTERED FRONTOGENETIC
FORCING IS LOCATED ACROSS THE NORTHERN FORECAST ARE YIELDING THE
LINEAR SNOW BAND. THIS HAS SEEDED THE LOW-LEVEL 3-4KFT SUPERCOOLED
LIQUID LAYER /FINALLY/ TO CHANGE THE FZDZ/FZRA TO SNOW.
THE TREND TODAY IN THE RAP FRONTOGENESIS IS TO SHIFT
EASTWARD FROM ABOUT WHERE IT IS NOW...WITHOUT MUCH MORE SOUTHWARD
PROGRESSION...EXITING BY 15Z. 20.06Z NAM HAS VERY SIMILAR
GUIDANCE...HOWEVER THE BAND WOULD SHIFT A BIT FURTHER SOUTH. SINCE
THIS IS THE SEEDER CLOUD...IT DETERMINES THE NORTHERN EXTENT OF
THE FZRA/FZDZ AREA. TO THE SOUTH...ABOUT A 2KM DEEP SUPERCOOLED
LIQUID LAYER EXISTS. RADAR HAS SHOWN SOME DECREASE IN EITHER THE
DEPTH OR LIQUID DROP SIZE OVER THE PAST HOURS IN THE DRIZZLE LAYER
WITH LESS REFLECTIVITY. THIS MAKES FOR PAUSE ON THE ADVISORY. BUT ANOTHER
AREA OF FZRA SHOWERS ARE HEADING IN FROM ERN IOWA...WITH MORE INTO
NRN MO...SO NO SHORTAGE OF INSTABILITY SHOWERS HEADING THIS WAY.
WITH UPSTREAM ENERGY AND LIFT SHIFTING INTO THE AREA...FELT THE
NEED TO EXTEND /IN TIME/ THE FREEZING RAIN ADVISORY...SOUTH OF
THE SNOW BAND...WHERE MORE ICE CAN BE EXPECTED THIS MORNING. WHILE
THE LIFT IS NOTHING LIKE LAST EVENING...THE SURFACE LOW SHIFTING
TO THE SOUTH OF THE AREA WITH DEFORMATION IN THE LOW-LEVELS OVER
NERN IA AND SRN WI MEAN FZRA/FZDZ COULD CONTINUE. MODEL GUIDANCE
ALSO SUGGESTS A WEAK INVERTED TROUGH EMANATING NW FROM THE
SURFACE LOW TO ENHANCE LOW-LEVEL VERTICAL MOTION...ENHANCING CLOUD
DROP GROWTH FOR DRIZZLE. THE LATEST HRRR RUNS HAVE THIS
SUGGESTION...ESPECIALLY LATER ACROSS THE SOUTHERN COUNTIES. THE
SNOW BAND SHOULD ONLY MOVE ABOUT ONE MORE COUNTY SOUTH BEFORE
SHIFTING EAST...AND AGAIN ALLOWING FOR AN ALL LIQUID PRECIPITATION
TYPE. HOWEVER...BEING FURTHER NORTH...THE LIFT IS SOMEWHAT MORE
LIMITED AND THE THREAT ALSO MORE LIMITED /I-90 ROUGHLY/.
THEREFORE...THINK THERE IS ADDITIONAL THREAT FOR FREEZING
PRECIPITATION...ESPECIALLY ACROSS THE SOUTH...THROUGH THE DAY.
WILL EXTENDED THE FREEZING RAIN ADVISORY IN EXTREME NERN IA AND
SWRN WI UNTIL 3PM...AND AREAS NORTH UNTIL 18Z. WILL CANCEL THE
FREEZING RAIN ADVISORY IN AREAS IT IS NOW SNOWING. CONFIDENCE IS
LOW IN THAT NORTHERN AREA...IF THERE WILL BE ENOUGH VERTICAL
MOTION TO CAUSE FZDZ TODAY...BUT IF NEEDED IT CAN BE CANCELLED
EARLY. ICING LOOKS TO BE ABOUT ANOTHER 0.05 INCHES ACROSS THE
SOUTHERN AREA...BEFORE DIMINISHING LATER.
.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 405 AM CST FRI DEC 20 2013
SATURDAY SEEMS TO BE AN IN BETWEEN DAY BEFORE THE STRONG CYCLONE
OVER THE SWRN U.S. CURRENTLY...SHIFTS TOWARD THE GREAT LAKES.
CLOUD TO GROUND LIGHTNING STRIKES WERE SEEN OVERNIGHT IN AZ WHICH
IN THE WEST...USUALLY HAPPENS ONLY WITH THE STRONGEST IMPULSES. SO
THIS IS A NICE SHORTWAVE TROUGH. THERE ARE A NUMBER OF FAVORABLE
DYNAMICS WITH THIS SYSTEM THAT SHIFT IN...INCLUDING AN INTENSE
160KT+ JET THAT DEVELOPS OVER SRN CANADA AS THE RIDGE BUILDS
DOWNSTREAM OF THE SHORTWAVE EJECTING INTO THE PLAINS. THIS IS
CLASSIC FOR MIDWESTERN HEAVY SNOWFALL CLIMATOLOGY. THIS PLACES A
VERY FAVORABLE ENTRANCE REGION OVER IL/SRN WI SAT NIGHT AND
SUNDAY. A VERY WARM AND MOIST SECTOR /SPC MDT RISK/ WILL BE RIDING
NORTH OUT OF THE GULF ON 50-60KT LOW-LEVEL WINDS AS INFLOW TO THE
FORCING...WHICH IS STRONG QVECTOR CONVERGENCE ALOFT AS
EXPECTED...TO THE SOUTHEAST. THIS STORM WILL PRODUCE HEAVY
SNOWFALL...THE QUESTION IS LOCATION.
WHILE THE WPC WINTER WEATHER DESK CONFIDENCE IS LOWER...IT SEEMS
THE MODELS ARE DRAWING IN ON A SOLUTION THAT WOULD PLACE THE HEAVY
SNOW BAND JUST INTO GRANT COUNTY. THIS WAS VERY CLOSE TO THE
ONGOING FORECAST SO REALLY ONLY MINOR CHANGES WERE MADE. THE NAM
SOLUTIONS STILL SEEM OUT TO LUNCH COMPARED TO THE OTHER
DETERMINISTIC MODELS...A DRY AND EAST OUTLIER. OVERALL...WILL
KEEP THE WATCH UNTIL CONFIDENCE GROWS ON THE LOCATION...BUT THE
REGION WILL SEE A 7-10 INCH SNOW BAND FROM THIS SYSTEM.
WILL BE MONITORING FOR POSSIBLE CHRISTMAS DAY WEATHER ON THE WARM
AIR ADVECTION SHIFTING IN...AFTER THE MONDAY AND MONDAY NIGHT
COOL DOWN POST STORM. THE 20.00Z ECMWF IS A BIT MORE AGGRESSIVE ON
HOLIDAY WEATHER...WE WILL SEE.
&&
.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1137 PM CST THU DEC 19 2013
FREEZING RAIN AND DRIZZLE HAS SPREAD ACROSS THE REGION WITH
CONDITIONS DROPPING FROM MVFR TO IFR AS THE MAIN BAND OF DRIZZLE
MOVES IN. THIS WILL CREATE ICY CONDITIONS THROUGH MID TO LATE
MORNING ON FRIDAY. THIS FREEZING RAIN/DRIZZLE IS EXPECTED TO
CHANGE OVER TO LIGHT SNOW FOR A PERIOD ON FRIDAY BEFORE POSSIBLY
GOING BACK TO FREEZING DRIZZLE THROUGH THE REST OF THE DAY.
CONFIDENCE IS NOT HIGH ON WHETHER THAT SECOND CHANGE OVER WILL
OCCUR BACK TO DRIZZLE...BUT IT LOOKS POSSIBLE. CONDITIONS WILL
REMAIN MVFR TO IFR WITH WINDS SHIFTING FROM THE EAST TO NORTHEAST
IN THE AFTERNOON.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 9 AM CST THIS MORNING FOR
WIZ032>034-041>044-053>055-061.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ043-044-053>055-061.
MN...FREEZING RAIN ADVISORY UNTIL 9 AM CST THIS MORNING FOR MNZ079-
086>088-094>096.
IA...FREEZING RAIN ADVISORY UNTIL 9 AM CST THIS MORNING FOR
IAZ008>011-018-019-029-030.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR IAZ011-029-030.
&&
$$
SHORT TERM...BAUMGARDT
LONG TERM...BAUMGARDT
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS PUEBLO CO
1105 AM MST FRI DEC 20 2013
.UPDATE...
ISSUED AT 1044 AM MST FRI DEC 20 2013
LOW CLOUDS AND FOG ARE NOT DISSIPATING OVER EL PASO COUNTY AND
ALONG THE LOWER ARKANSAS RIVER VALLEY. MIDDLE CLOUD DECK OVER THE
REGION IS HAMPERING THE DISSIPATION OF THE LOW CLOUDS AND FOG.
UPDATED GRIDS FOR LOW CLOUDS AND AREAS OF FOG TO CONTINUE IN THESE
REGIONS WELL INTO THE EVENING. ALSO COOLED DAYTIME TEMPERATURES
WITH PERSISTENT CLOUDS. AS THE SURFACE HIGH MOVES EAST OF THE
REGION...COLD AIR WILL BECOME MORE SHALLOW OVERNIGHT. ANTICIPATE
LOW CLOUDS AND ANY FOG WILL SETTLE ALONG THE ARKANSAS RIVER VALLEY
BY SUNRISE.
UPDATE ISSUED AT 927 AM MST FRI DEC 20 2013
UPDATED GRIDS TO HAVE FOG PERSIST UNTIL EARLY AFTERNOON OVER EL
PASO COUNTY. PERSISTENT SOUTHERLY FLOW SHOULD KEEP LOW CLOUDS AND
FOG OVER EL PASO COUNTY. COLD AIR IS FAIRLY SHALLOW SO THERE IS
HOPE THE FOG AND LOW CLOUDS WILL DISSIPATE BY EARLY AFTERNOON.
ABOVE THE FOG AND LOW CLOUDS...THERE ARE SOME MIDDLE AND HIGH
LEVEL CLOUDS. WILL HAVE TO MONITOR EROSION OF LOW CLOUDS OVER EL
PASO COUNTY AND MAY HAVE TO EXTEND FOG FURTHER INTO THE AFTERNOON.
--PGW--
UPDATE ISSUED AT 542 AM MST FRI DEC 20 2013
UPDATED THE FORECAST TO ADD FZFG TO EL PASO COUNTY FOR THE
MORNING HOURS. LIGHT PRECIP WILL LIKELY NOT MEASURE SO WILL LEAVE
AREA LOW POPS INTACT. ROSE
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 250 AM MST FRI DEC 20 2013
...MUCH COOLER TODAY...
...SNOW CHANCES NOT LOOKING TOO GREAT...
CURRENTLY...SOME LIGHT SHSN OVER THE WRN PORTION OF THE
STATE...MAINLY INVOF KGJT. SOME LIGHT PRECIP ALSO LIKELY MOVING INTO
THE SAWATCH RANGE AND CONTDVD THRU THE MORNING HOURS. TEMPS MAINLY
IN THE 20S...WITH SOME SINGLE DIGITS FOR THE HIGH VALLEYS. EXTENSIVE
LOW CLOUD DECK NOW COVERING THE ERN PLAINS...BUT FAIRLY SHALLOW AND
THE ERN MTS ARE ACTUALLY RELATIVELY CLEAR THIS MORN.
MAIN QUESTION TODAY IS HOW LONG THE LOW CLOUDS WILL TAKE TO BREAK UP
OVER THE PLAINS. THIS WILL DETERMINE POTENTIAL HIGH TEMPS TODAY.
CURRENT MODEL SOUNDINGS ARE NOT VERY HELPFUL...WITH THE NAM BREAKING
THINGS OUT PRETTY EARLY AND THE RAP HOLDING ON TO A LOW CLOUD DECK
THROUGH THE EARLY AFTERNOON. GIVEN THE PRETTY STOUT LLVL INVERSION
AS ALREADY HINTED OUT IN THE 00Z DEN SOUNDING...AND THE GENERALLY
LIGHT UPSLOPE WINDS EXPECTED OVER THE PLAINS...WILL LEAN TOWARDS A
LATER TIME FOR THE LOW CIGS TO DISSIPATE. THIS WILL KEEP AFTERNOON
HIGHS FROM REACHING THE POTENTIAL SUGGESTED BY H7 TEMPS ONLY A FEW
DEGREES BELOW ZERO. HAVE CUT BACK TEMPS A FEW DEGREES FROM CURRENT
FORECAST...BUT SOME GUIDANCE SUGGESTS THEY MAY EVEN END UP LOWER
THAN FORECAST. BOTTOM LINE...IT WILL BE A GOOD 20 DEGREES COOLER
THAN YESTERDAY...AND FINALLY FEEL LIKE DECEMBER FOR SERN CO.
SNOW POTENTIAL IS NOT LOOKING TOO GREAT TODAY. A NUMBER OF MODEL
SOUNDINGS SUGGEST SOME LIGHT PRECIP OVER THE PLAINS THIS MORN...BUT
GIVEN THE RELATIVELY SHALLOW CLOUD LAYER DO NOT EXPECT ANYTHING THAT
FALLS TO ACCUMULATE OR EVEN MEASURE. SO...HAVE KEPT POPS LOW FOR THE
PLAINS THROUGH TONIGHT. PERSISTENT LIGHT SHSN WILL BE ONGOING OVER
THE CONTDVD AND WILL PICK UP GRADUALLY AS WE GO THROUGH THE
AFTERNOON BEFORE TAPERING OFF THIS EVENING. BUT ACCUMS NOT LOOKING
TOO IMPRESSIVE WITH AT BEST A FEW INCHES OVER THE DVD BY SUN MORNING.
WITH SOME PARTIAL CLEARING TONIGHT AND LIGHT WINDS...TEMPS WILL BE
ON THE COLD SIDE...WITH SOME TEENS POSSIBLE FOR THE PLAINS AND
CONTINUED SINGLE DIGITS AND NEGATIVE READINGS FOR THE MTS AND HIGH
VALLEYS. ROSE
.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 250 AM MST FRI DEC 20 2013
SATURDAY INTO SUNDAY APPEARS TO BE THE MOST ACTIVE WX PD DURING THIS
FORECAST SEGMENT. THE SOUTHERN STORM TRACKING OVER NM MAY CLIP THE
FAR SE CORNER OF COLORADO...WHILE THE NORTHERN SYSTEM WILL LIKELY
BRING SNOW TO THE MOUNTAINS AND POSSIBLY PARTS OF THE I-25 CORRIDOR.
FOR THE FAR SE PLAINS...IT APPEARS THE BEST CHANCE OF BACA COUNTY
SEEING ANY PRECIP WILL BE SAT AFTERNOON AND EVENING. BOTH GFS AND EC
HAVE AN IMPRESSIVE BAND OF PRECIP DEVELOPING OVER THE N TX PHDL INTO
THE OK PHDL...WITH THE N PARTS OF THIS BAND ENTERING INTO SE BACA
COUNTY. ON THE OTHER HAND THE NAM (00Z AND 06Z RUNS) KEEP THE PRECIP
DOWN INTO TX. I HAVE LEANED TOWARDS THE GFS AND EC BUT HAVE
DECREASED POPS A BIT OVER THE BACA COUNTY REGION TO ACCOUNT FOR THE
TRENDS IN THE NAM GUIDANCE.
THE N TIER SYSTEM WILL DROP INTO CO DURING SAT MORNING AND MOVE
ACROSS THE REGION SAT NITE. SNOW IN THE C MTNS IS LIKELY...WITH A
GOOD CHANCE OF SNOW OVER MOST OF THE OTHER MTNS DURING THE LATTER
AFTERNOON AND EVENING HOURS. IT DOES NOT APPEAR THAT ANY SIGNIF
ACCUMS WILL OCCUR...BUT 2-3" IS NOT OUT OF THE QUESTION...ESPECIALLY
ON THE NW SLOPES. SOME SNOW SHOWERS MAY MAKE IT OUT ONTO THE I-25
CORRIDOR...ESPECIALLY SAT EVE/NITE.
DRY AND COOL WX WILL BE LIKELY LATER SUNDAY INTO EARLY TUESDAY.
TUESDAY..XMAS EVE..MAY BE RATHER QUITE NICE GIVEN THE LEE TROUGH AND
DOWNSLOPE. TEMPS ON THE PLAINS WILL LIKELY BE IN THE 50S WITH A 60
OR TWO POSSIBLE.
BY LATE TUESDAY/TUE NITE ANOTHER COLD FRONT WILL MOVE ACROSS THE
REGION. HOWEVER...THIS SYSTEM LOOKS WEAKER ON BOTH THE EC AND GFS
AND THE CHANCE OF SNOW IS DECREASING FOR XMAS EVE INTO XMAS FOR THE
ENTIRE REGION. I HAVE NOT REMOVED POPS COMPLETELY...BUT THE TREND IN THE
GUIDANCE IS SHOWING THE SNOW CHANCES FOR THE LOWER ELEVATIONS
DECREASING. I WOULD NOT BE TOO SURPRISED IF LATER SHIFTS REMOVE THE
POPS COMPLETELY FOR THE LOWER ELEVATIONS XMAS EVE INTO XMAS. TEMPS
XMAS DAY WILL BE A GOOD 10-20F COOLER THAN XMAS EVE.
ANOTHER DISTURBANCE WILL MOVE DOWN ACROSS THE REGION ON FRIDAY
BRINGING ANOTHER COOL FRONT TO THE REGION. /HODANISH
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1044 AM MST FRI DEC 20 2013
SHALLOW POLAR AIR MASS WILL REMAIN OVER INTERSTATE 25 CORRIDOR AND
EASTERN PLAINS WELL INTO THE EVENING. WITH PERSISTENT WEAK
SOUTHERLY FLOW...ANTICIPATE KCOS AND KPUB WILL STAY IN LOWER MVFR
TO IFR CONDITIONS THROUGHOUT THE DAY AND INTO THE EVENING. AS THE
COLD AIR BECOMES SHALLOW TONIGHT...EXPECT IMPROVING CONDITIONS TO
DESCEND SOUTHWARD OVER EL PASO COUNTY. OFTEN...CAN SEE A RAPID
IMPROVEMENT AT KCOS WHEN THIS HAPPENS. BEST ESTIMATE AT THIS TIME
IS TO HAVE CONDITIONS IMPROVE AROUND MIDNIGHT. IF WEAK EASTERLY
FLOW PERSISTS ALONG ARKANSAS RIVER...KPUB COULD STAY IFR UNTIL
SUNRISE.
KALS...WEAK DISTURBANCE PASSING OVERHEAD AND MIDDLE LEVEL CLOUDS
SHOULD HAMPER FOG DEVELOPMENT TONIGHT.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...PGW
SHORT TERM...ROSE
LONG TERM...HODANISH
AVIATION...PGW
AREA FORECAST DISCUSSION
NWS PUEBLO CO
934 AM MST FRI DEC 20 2013
.UPDATE...
ISSUED AT 927 AM MST FRI DEC 20 2013
UPDATED GRIDS TO HAVE FOG PERSIST UNTIL EARLY AFTERNOON OVER EL
PASO COUNTY. PERSISTENT SOUTHERLY FLOW SHOULD KEEP LOW CLOUDS AND
FOG OVER EL PASO COUNTY. COLD AIR IS FAIRLY SHALLOW SO THERE IS
HOPE THE FOG AND LOW CLOUDS WILL DISSIPATE BY EARLY AFTERNOON.
ABOVE THE FOG AND LOW CLOUDS...THERE ARE SOME MIDDLE AND HIGH
LEVEL CLOUDS. WILL HAVE TO MONITOR EROSION OF LOW CLOUDS OVER EL
PASO COUNTY AND MAY HAVE TO EXTEND FOG FURTHER INTO THE AFTERNOON.
--PGW--
UPDATE ISSUED AT 542 AM MST FRI DEC 20 2013
UPDATED THE FORECAST TO ADD FZFG TO EL PASO COUNTY FOR THE
MORNING HOURS. LIGHT PRECIP WILL LIKELY NOT MEASURE SO WILL LEAVE
AREA LOW POPS INTACT. ROSE
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 250 AM MST FRI DEC 20 2013
...MUCH COOLER TODAY...
...SNOW CHANCES NOT LOOKING TOO GREAT...
CURRENTLY...SOME LIGHT SHSN OVER THE WRN PORTION OF THE
STATE...MAINLY INVOF KGJT. SOME LIGHT PRECIP ALSO LIKELY MOVING INTO
THE SAWATCH RANGE AND CONTDVD THRU THE MORNING HOURS. TEMPS MAINLY
IN THE 20S...WITH SOME SINGLE DIGITS FOR THE HIGH VALLEYS. EXTENSIVE
LOW CLOUD DECK NOW COVERING THE ERN PLAINS...BUT FAIRLY SHALLOW AND
THE ERN MTS ARE ACTUALLY RELATIVELY CLEAR THIS MORN.
MAIN QUESTION TODAY IS HOW LONG THE LOW CLOUDS WILL TAKE TO BREAK UP
OVER THE PLAINS. THIS WILL DETERMINE POTENTIAL HIGH TEMPS TODAY.
CURRENT MODEL SOUNDINGS ARE NOT VERY HELPFUL...WITH THE NAM BREAKING
THINGS OUT PRETTY EARLY AND THE RAP HOLDING ON TO A LOW CLOUD DECK
THROUGH THE EARLY AFTERNOON. GIVEN THE PRETTY STOUT LLVL INVERSION
AS ALREADY HINTED OUT IN THE 00Z DEN SOUNDING...AND THE GENERALLY
LIGHT UPSLOPE WINDS EXPECTED OVER THE PLAINS...WILL LEAN TOWARDS A
LATER TIME FOR THE LOW CIGS TO DISSIPATE. THIS WILL KEEP AFTERNOON
HIGHS FROM REACHING THE POTENTIAL SUGGESTED BY H7 TEMPS ONLY A FEW
DEGREES BELOW ZERO. HAVE CUT BACK TEMPS A FEW DEGREES FROM CURRENT
FORECAST...BUT SOME GUIDANCE SUGGESTS THEY MAY EVEN END UP LOWER
THAN FORECAST. BOTTOM LINE...IT WILL BE A GOOD 20 DEGREES COOLER
THAN YESTERDAY...AND FINALLY FEEL LIKE DECEMBER FOR SERN CO.
SNOW POTENTIAL IS NOT LOOKING TOO GREAT TODAY. A NUMBER OF MODEL
SOUNDINGS SUGGEST SOME LIGHT PRECIP OVER THE PLAINS THIS MORN...BUT
GIVEN THE RELATIVELY SHALLOW CLOUD LAYER DO NOT EXPECT ANYTHING THAT
FALLS TO ACCUMULATE OR EVEN MEASURE. SO...HAVE KEPT POPS LOW FOR THE
PLAINS THROUGH TONIGHT. PERSISTENT LIGHT SHSN WILL BE ONGOING OVER
THE CONTDVD AND WILL PICK UP GRADUALLY AS WE GO THROUGH THE
AFTERNOON BEFORE TAPERING OFF THIS EVENING. BUT ACCUMS NOT LOOKING
TOO IMPRESSIVE WITH AT BEST A FEW INCHES OVER THE DVD BY SUN MORNING.
WITH SOME PARTIAL CLEARING TONIGHT AND LIGHT WINDS...TEMPS WILL BE
ON THE COLD SIDE...WITH SOME TEENS POSSIBLE FOR THE PLAINS AND
CONTINUED SINGLE DIGITS AND NEGATIVE READINGS FOR THE MTS AND HIGH
VALLEYS. ROSE
.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 250 AM MST FRI DEC 20 2013
SATURDAY INTO SUNDAY APPEARS TO BE THE MOST ACTIVE WX PD DURING THIS
FORECAST SEGMENT. THE SOUTHERN STORM TRACKING OVER NM MAY CLIP THE
FAR SE CORNER OF COLORADO...WHILE THE NORTHERN SYSTEM WILL LIKELY
BRING SNOW TO THE MOUNTAINS AND POSSIBLY PARTS OF THE I-25 CORRIDOR.
FOR THE FAR SE PLAINS...IT APPEARS THE BEST CHANCE OF BACA COUNTY
SEEING ANY PRECIP WILL BE SAT AFTERNOON AND EVENING. BOTH GFS AND EC
HAVE AN IMPRESSIVE BAND OF PRECIP DEVELOPING OVER THE N TX PHDL INTO
THE OK PHDL...WITH THE N PARTS OF THIS BAND ENTERING INTO SE BACA
COUNTY. ON THE OTHER HAND THE NAM (00Z AND 06Z RUNS) KEEP THE PRECIP
DOWN INTO TX. I HAVE LEANED TOWARDS THE GFS AND EC BUT HAVE
DECREASED POPS A BIT OVER THE BACA COUNTY REGION TO ACCOUNT FOR THE
TRENDS IN THE NAM GUIDANCE.
THE N TIER SYSTEM WILL DROP INTO CO DURING SAT MORNING AND MOVE
ACROSS THE REGION SAT NITE. SNOW IN THE C MTNS IS LIKELY...WITH A
GOOD CHANCE OF SNOW OVER MOST OF THE OTHER MTNS DURING THE LATTER
AFTERNOON AND EVENING HOURS. IT DOES NOT APPEAR THAT ANY SIGNIF
ACCUMS WILL OCCUR...BUT 2-3" IS NOT OUT OF THE QUESTION...ESPECIALLY
ON THE NW SLOPES. SOME SNOW SHOWERS MAY MAKE IT OUT ONTO THE I-25
CORRIDOR...ESPECIALLY SAT EVE/NITE.
DRY AND COOL WX WILL BE LIKELY LATER SUNDAY INTO EARLY TUESDAY.
TUESDAY..XMAS EVE..MAY BE RATHER QUITE NICE GIVEN THE LEE TROUGH AND
DOWNSLOPE. TEMPS ON THE PLAINS WILL LIKELY BE IN THE 50S WITH A 60
OR TWO POSSIBLE.
BY LATE TUESDAY/TUE NITE ANOTHER COLD FRONT WILL MOVE ACROSS THE
REGION. HOWEVER...THIS SYSTEM LOOKS WEAKER ON BOTH THE EC AND GFS
AND THE CHANCE OF SNOW IS DECREASING FOR XMAS EVE INTO XMAS FOR THE
ENTIRE REGION. I HAVE NOT REMOVED POPS COMPLETELY...BUT THE TREND IN THE
GUIDANCE IS SHOWING THE SNOW CHANCES FOR THE LOWER ELEVATIONS
DECREASING. I WOULD NOT BE TOO SURPRISED IF LATER SHIFTS REMOVE THE
POPS COMPLETELY FOR THE LOWER ELEVATIONS XMAS EVE INTO XMAS. TEMPS
XMAS DAY WILL BE A GOOD 10-20F COOLER THAN XMAS EVE.
ANOTHER DISTURBANCE WILL MOVE DOWN ACROSS THE REGION ON FRIDAY
BRINGING ANOTHER COOL FRONT TO THE REGION. /HODANISH
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 250 AM MST FRI DEC 20 2013
MAIN QUESTION IS HOW QUICKLY IFR-MVFR CIGS WILL CLEAR FROM THE
PLAINS TODAY. WITH GENERALLY LIGHT UPSLOPE WINDS AND STRONG
TEMPERATURE INVERSIONS...EXPECT CIGS TO STAY LOW FOR A GOOD PORTION
OF THIS MORNING AND POSSIBLY THROUGH THE AFTERNOON...FOR KPUB FROM
17-18Z...AND AT KCOS 18-19Z. NO ACCUMULATING PRECIP IS EXPECTED BUT
SOME LIGHT PRECIP WILL BE POSSIBLE WITHIN THE LOW CLOUD DECK...WITH
TOPS BREAKING OUT ONLY 1000 FT OR SO AGL. VFR CONDITIONS WILL THEN
PERSIST THROUGH SUN MORNING. LIGHT SHSN WILL CONTINUE THROUGH THIS
EVE OVER THE CONTDVD...WITH MT TOPS OBSCURED DURING THIS PERIOD.
AT KALS...SOME LOCAL PC FG OR BR POSSIBLE THROUGH 15-16Z...AND AGAIN
LATE TONIGHT...BUT WILL STICK WITH A PERSISTENCE FORECAST FOR NOW IN
THE TAFS AND LEAVE CONDITIONS VFR. ROSE
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...PGW
SHORT TERM...ROSE
LONG TERM...HODANISH
AVIATION...ROSE
AREA FORECAST DISCUSSION
NWS ALBANY NY
120 PM EST FRI DEC 20 2013
.SYNOPSIS...
WAVES OF LOW PRESSURE WILL TRACK ALONG A NEARLY STATIONARY FRONT
FROM THE GREAT LAKES THROUGH NORTHERN NEW YORK AND NORTHERN NEW
ENGLAND THROUGH TONIGHT. THE FRONT WILL SINK SOUTH AS A COLD FRONT
INTO PARTS OF CENTRAL NEW YORK AND SOUTHERN VERMONT SATURDAY
NIGHT...SUPPORTING CHANCES FOR FREEZING RAIN IN THE NORTH COUNTRY.
STRONG LOW PRESSURE WILL TRACK NORTHEAST OUT OF THE TENNESSEE AND
OHIO VALLEY SUNDAY AS THE FRONT SURGES NORTH INTO CANADA...
BRINGING LOCALLY HEAVY RAIN AND WARMER TEMPERATURES TO OUR REGION.
A COLD FRONT WILL TRACK THROUGH OUR AREA SUNDAY NIGHT AND MONDAY
MORNING BRINGING A RETURN TO COLDER WEATHER FOR THE BEGINNING OF
NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 1245 PM...RADAR INDICATED FAIRLY WIDESPREAD LIGHT RAIN
OCCURRING OR WILL SHORTLY SPREAD INTO THE NORTHERN THREE-FOURTHS OF
THE FORECAST AREA. HAVE ADJUSTED POPS UPWARD TO LIKELY AND
CATEGORICAL IN THESE AREAS AND INCREASED POPS OVER THE FAR SOUTH TO
SLIGHT OR LOW CHANCE. TEMPS IN THE ADIRONDACK ZONES GENERALLY IN THE
MID OR UPPER 30S SO NO THREAT FOR ANY FREEZING RAIN FOR THE REST OF
TODAY. HAVE ADJUSTED TEMPS HIGHER...ESPECIALLY ACROSS THE HIGHER
TERRAIN WHERE THE SOUTHWEST FLOW HAS SCOURED OUT ANY REMAINING
COLDER AIR. TEMPS OVER THE HIGHER TERRAIN OF THE CATSKILLS ARE
CURRENTLY AROUND 50.
.PREVIOUS DISCUSSION...
AS OF 930 AM EST...RADARS INDICATING SOME LIGHT SPOTTY RETURNS
ACROSS MAINLY OUR NORTHERN AREAS. THE HRRR LOOKS ON CUE...WITH
LIGHTLY PRECIPITATION LIKELY TO FILL IN AS THE AFTERNOON
ARRIVES...DUE TO INCREASED CONVERGENCE AND MOISTURE ALONG AN
APPROACHING BOUNDARY.
TEMPERATURES IN THE VALLEYS GENERALLY IN THE 30S ABOVE FREEZING.
HOWEVER...MESO SITES INDICATED TEMPERATURES INTO THE 40S ACROSS
MAINLY THE HIGHER ELEVATIONS OF CATSKILLS...BUT EVEN ABOVE FREEZING
ACROSS OUR SOUTHERN ADIRONDACKS. SNOW MELT HAS COMMENCE...AND MANY
AREAS WILL LIKELY NOT DROP BACK BELOW FREEZING UNTIL SUNDAY NIGHT.
NO REAL CHANGES WITH THIS PACKAGE...TWEAKED THE POPS (DOWNWARD A
LITTLE IN THE BEGINNING GRIDS) AND OF COURSE RE-TOOLED THE HOURLY
GRIDS. LOOK FOR LOTS OF CLOUDS TODAY...AND AN INCREASING CHANCE OF
MAINLY RAIN SHOWERS THIS AFTERNOON (WITH PERHAPS SOME POCKETS OF
FREEZING RAIN UP NORTH)...MAINLY ALBANY NORTH.
HIGH TEMPERATURES THIS AFTERNOON REACHING 45-50 SOUTH OF CAPITAL
DISTRICT...40-45 CAPITAL DISTRICT AND SURROUNDING PARTS. TO THE
NORTH...HIGHS WILL GENERALLY BE 35-40.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
ONE WEAK UPPER IMPULSE AND WEAK FORCING AFFECTS OUR REGION THIS
AFTERNOON AND TONIGHT. THE BEST COVERAGE OF PRECIPITATION TONIGHT
SHOULD BE NORTH OF THE MOHAWK VALLEY AND WEST OF THE LAKE GEORGE
SARATOGA REGION. HOWEVER...SOLID CHANCES FROM SCHOHARIE VALLEY
THROUGH THE CAPITAL DISTRICT...SOUTHERN VT INTO THE BERKSHIRES AND
EASTERN CATSKILLS. PRECIPITATION AMOUNTS SHOULD BE LIGHT...BUT
NIGHTTIME COOLING IN THE SOUTHERN ADIRONDACKS COULD ALLOW SOME OF
THE PRECIPITATION TO FALL AS FREEZING RAIN...MAYBE UP TO A TENTH
OF AN INCH. HOLDING OFF ON ANY ADVISORIES SINCE TEMPERATURES COULD BE
BORDERLINE AND NEXT SET OF GUIDANCE CAN BE CONSULTED AND STILL GET
LEAD TIME ON AN ADVISORY IF IT NEEDS TO BE ISSUED THIS
AFTERNOON...BUT AGAIN JUST FOR PARTS OF NORTHERN HERKIMER AND
HAMILTON COUNTIES. LOWS TONIGHT IN THE 30S.
STRONGER UPPER ENERGY...FORCING AND MOISTURE ADVECTION APPROACHES
SATURDAY AFTERNOON THROUGH SUNDAY AFTERNOON. RAIN SHOULD SPREAD
ACROSS THE REGION SATURDAY AFTERNOON AND NIGHT...AND BE HEAVY AT
TIMES SATURDAY NIGHT THROUGH SUNDAY. THERE ARE CONSIDERABLE
DISAGREEMENTS IN SOURCES OF GUIDANCE AND ENSEMBLES AS TO HOW MUCH
COLDER AIR SINKS SOUTH SATURDAY NIGHT IN RESPONSE TO ENHANCED UPPER
CONFLUENCE IN CANADA AS UPPER ENERGY TRACKS WELL NORTH OF THE U.S.
CANADIAN BORDER. BASED ON THE SOURCES OF GUIDANCE THAT RESOLVE
THESE ISSUES BEST...SIDING ON SOME COLD AIR DRAINING SOUTH IN
RESPONSE TO ENHANCED AGEOSTROPHIC NORTHERLY LOW LEVEL FLOW...
RESULTING IN SOME POTENTIAL FREEZING RAIN FOR THE SOUTHERN
ADIRONDACKS TO THE LAKE GEORGE AREA. WE WILL SEE HOW THE SNOW PACK
ACROSS THE ENTIRE REGION INFLUENCES SURFACE TEMPERATURES THROUGH
SATURDAY NIGHT AS WELL. WITH SUCH HIGH UNCERTAINTIES IN THE
RAIN/FREEZING RAIN LINE...NO HEADLINES YET UNTIL WE GET CLOSER TO
THE POTENTIAL EVENT. WHATEVER AREAS GET FREEZING RAIN COULD GET UP
TO A QUARTER INCH.
A VERY STRONG BOUNDARY LAYER JET SEGMENT AND ISENTROPIC LIFT...
ALONG WITH ANOMALOUSLY HIGH PWAT...SHOULD SUPPORT A HEAVY
RAIN EVENT...AND COMBINED WITH SNOW MELT...COULD RESULT IN SOME
FLOODING POTENTIAL. THIS WILL BE ADDRESSED IN THE HWO AS RAINFALL
FORECASTS FROM SOURCES OF GUIDANCE AND ENSEMBLES STILL A BROAD
RANGE AND AXIS OF HEAVIEST RAIN COULD FALL NORTH OF WHERE MAXIMUM
SNOW MELT OCCURS. A WEST TO SOUTHWEST BOUNDARY LAYER FLOW USUALLY
RESULTS IN THE HEAVIEST PRECIPITATION IN THE ADIRONDACKS...WHICH
AGAIN MAY SEE THE LEAST WARM TEMPERATURES AND LEAST SNOW MELT.
SO...STILL HOLDING OFF ON ANY FLOOD WATCHES.
HIGHS SATURDAY IN THE 40S TO AROUND 50...WITH LOWS SATURDAY NIGHT
AROUND 40 TO THE MID 40S...LOWER TO MID 30S IN THE NORTH COUNTRY.
HIGHS SUNDAY IN THE 50S MANY AREAS...BUT INTO THE 60S TOWARD POU
AND NW CT...AND IN THE 40S IN THE NORTH COUNTRY. THE COLD
FRONT TRACKS THROUGH THE REGION SUNDAY NIGHT AND SHOWERS SHOULD
CHANGE TO SNOW SHOWERS AS COLD AIR SPREADS ACROSS THE REGION.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
HAVE GENERALLY POPULATED THIS PORTION OF THE GRIDDED DATABASE WITH
00Z/20 HPC GUIDANCE.
MON-TUE...THE COLD FRONT ASSOCIATED WITH THIS WEEKEND/S STORM SYSTEM
SHOULD BE EXITING THE REGION MON AM...WITH RAIN SHOWERS TAPERING
OFF...BUT PROBABLY CHANGING TO SNOW SHOWERS BEFORE ENDING FOR AREAS
N AND W OF ALBANY. IN THE WAKE OF THE SFC FRONT...THE UPPER LEVEL
TROUGH WILL GRADUALLY TRANSLATE EASTWARD...PASSING ACROSS THE REGION
LATE MON NT OR ON TUE. THE COMBINATION OF THE ASSOCIATED COLD
POOL...AND COLDER AIR POURING ACROSS THE GREAT LAKES WILL LIKELY
LEAD TO AT LEAST SCATTERED SNOW SHOWERS AND FLURRIES FROM LATE
MONDAY INTO TUESDAY...ALONG WITH THE POSSIBILITY OF SOME LAKE EFFECT
SNOWBANDS SOMEWHERE ACROSS THE WESTERN ADIRONDACKS AND/OR MOHAWK
VALLEY...WHICH COULD OCCASIONALLY EXTEND INTO THE CAPITAL REGION AND
BERKSHIRES/SOUTHERN GREEN MTNS. AS FOR TEMPS...EXPECT MAXES TO REACH
THE 30S TO LOWER 40S MON IN VALLEY AREAS...AND 20S TO LOWER 30S
ACROSS HIGHER ELEVATIONS...WITH MOST MAX TEMPS LIKELY OCCURRING IN
THE MORNING WITH FALLING AFTERNOON TEMPS. FOR MON NT...EXPECT TEMPS
TO FALL INTO THE SINGLE DIGITS AND TEENS ACROSS NORTHERN AREAS...AND
TEENS AND LOWER/MID 20S FOR CENTRAL AND SOUTHERN AREAS. ON
TUE...EXPECT MAX TEMPS TO ONLY REACH THE SINGLE DIGITS AND LOWER
TEENS ACROSS MUCH OF THE SOUTHERN ADIRONDACKS...WITH MAINLY 20S FOR
VALLEY AREAS.
TUE NT-WED NT...HIGH PRESSURE WILL THEN BUILD IN FOR TUE
NT-WED...WHILE A WEAK CLIPPER TYPE SYSTEM PASSES BY TO OUR N AND W
WED NT. HAVE INCLUDED SOME SLIGHT CHC POPS FOR WED NT ACROSS
PORTIONS OF THE WESTERN ADIRONDACKS. AS FOR TEMPS...EXPECT TUE
NT/WED AM MINS TO FALL INTO THE SINGLE DIGITS AND TEENS IN MOST
AREAS...WITH SOME READINGS POSSIBLY FALLING TO BETWEEN ZERO AND 5
BELOW ACROSS PORTIONS OF THE SOUTHERN ADIRONDACKS. ON WED...EXPECT
MAX TEMPS TO REACH 25-30 IN VALLEY AREAS...AND UPPER TEENS TO LOWER
20S ACROSS HIGHER ELEVATIONS. FOR WED NT/THU AM...EXPECT MINS TO
FALL INTO THE TEENS AND 20S IN MOST AREAS.
THU...THE 00Z/20 ECMWF CONTINUES TO HINT AT A WEAK COASTAL SYSTEM
OFF THE SE COAST POTENTIALLY PHASING WITH SOME ENERGY ACROSS THE
GREAT LAKES TO ALLOW FOR LIGHT PRECIPITATION TO DEVELOP ACROSS THE
REGION. ALTHOUGH THE DETERMINISTIC 00Z/20 GFS IS NOT QUITE AS
EMPHATIC WITH THIS PHASING...SOME MEMBERS OF THE 00Z/20 GEFS DO
INDEED DEPICT SOME FORM OF THIS...WITH SOME SIGNAL NOTED IN THE MEAN
GEFS. WILL THEREFORE INDICATE CHC POPS...MAINLY FOR SNOW ON
THU...WITH PERHAPS A RAIN/SNOW MIX FOR SOUTHERN AREAS. AS FOR
TEMPS...HAVE INDICATED MAXES REACHING THE 35-40 IN MOST
VALLEYS...AND 25-30 FOR HIGHER ELEVATIONS.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
LIGHT RAIN TO IMPACT MAINLY THE NORTHERN TAFS THIS AFTERNOON
ALTHOUGH FOR THE MOST PART THE IMPACT SHOULD BE MARGINAL. WE DID
INCLUDE A 3-HR TEMPO 2SM BR (IFR) KPSF 19Z-22Z). OTHERWISE VFR
CIGS/VSBY WILL LIKELY TRANSITION TO MVFR AT THE REMAINING TAF
SITES...EXCEPT KPOU WHERE LESS IN THE WAY OF SHOWERS WILL MEAN A
CONTINUATION OF VFR INTO THE EVENING.
HOWEVER...AS HIGH DEWPOINTS WORK INTO THE REGION TONIGHT...EVERYONE
LOOKS TO DIP INTO THE MVFR THRESHOLD (LOW MVFR AT KALB) AND IFR
CONDITIONS AT KGFL...AFTER 00Z THIS EVENING. ONCE CONDITIONS
DROP...THEY MIGHT HANG AT THESE RESPECTIVE VALUES INTO AT LEAST
SATURDAY MORNING...POSSIBLY LONGER NORTH OF KPOU. A MILD BUT MOIST
SOUTHERLY FLOW WILL CONTINUE THROUGH THE PERIOD.
THE WIND WILL BE SOUTHERLY LESS THAN 10 KT THROUGH 12Z SATURDAY.
OUTLOOK...
SATURDAY NIGHT: HIGH OPERATIONAL IMPACT. DEFINITE RA.
SUNDAY: HIGH OPERATIONAL IMPACT. LIKELY RA.
SUNDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA.
MONDAY: MODERATE OPERATIONAL IMPACT. SLIGHT CHANCE OF SHRA...SHSN.
MONDAY NIGHT: MODERATE OPERATIONAL IMPACT. SCATTERED SHSN.
TUESDAY: LOW OPERATIONAL IMPACT.BREEZY ISOLATED SHSN.
TUESDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
WEDNESDAY: NO OPERATIONAL IMPACT. NO SIG WX.
&&
.HYDROLOGY...
WARMER TEMPERATURES WILL HAPPEN FRIDAY INTO THE WEEKEND...WITH A
FRONTAL BOUNDARY BRINGING SOME SHOWERS AND MIXED PRECIPITATION TO
CLOSE THE WORK WEEK. SOME SNOW MELT IS LIKELY BY THIS WEEKEND.
ALSO...A STORM SYSTEM MOVING ALONG A FRONTAL BOUNDARY MAY BRING
SIGNIFICANT PCPN TO THE FORECAST AREA SAT NIGHT INTO SUNDAY WITH
EVEN MILDER TEMPS.
TEMPERATURES SUNDAY ARE EXPECTED TO WARM INTO THE 50S OR POSSIBLY
EVEN 60S ACROSS THE EASTERN CATSKILLS...MID HUDSON VALLEY...CENTRAL
AND SOUTHERN TACONICS INTO THE BERKSHIRES AND ACROSS LITCHFIELD
COUNTY WITH 50S ACROSS THE CAPITAL REGION...40S FURTHER NORTH.
BETWEEN THE RAIN AND RUNOFF FROM SNOWMELT DUE TO THE MILD/WARM
TEMPERATURES SOME FLOODING COULD BE A PROBLEM INCLUDING ICE JAMS
ISSUES. AT THIS POINT...WE BELIEVE MOST IF NOT ALL OF THE SNOW COULD
BE MELTED FROM ABOUT THE MOHAWK RIVER...FURTHER NORTH TEMPERATURES
MIGHT NOT BE WARM ENOUGH TO MELT ALL OF THE SNOW.
THE POTENTIAL IS THERE FOR 1-2 INCHES OF RAINFALL FROM ALBANY
NORTHWARD...POSSIBLY SOME AREAS REACHING 3 INCHES. LESS AMOUNTS OF
RAIN LOOK TO FALL SOUTH OF THE CAPITAL REGION...AN INCH OR LESS.
WILL KEEP MENTION OF IN OUR HAZARDOUS WEATHER OUTLOOK.
FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED
AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
MA...NONE.
VT...NONE.
&&
$$
SYNOPSIS...HWJIV/NAS
NEAR TERM...HWJIV/NAS
SHORT TERM...NAS
LONG TERM...KL
AVIATION...HWJIV
HYDROLOGY...NAS
AREA FORECAST DISCUSSION
NWS ALBANY NY
110 PM EST FRI DEC 20 2013
.SYNOPSIS...
WAVES OF LOW PRESSURE WILL TRACK ALONG A NEARLY STATIONARY FRONT
FROM THE GREAT LAKES THROUGH NORTHERN NEW YORK AND NORTHERN NEW
ENGLAND THROUGH TONIGHT. THE FRONT WILL SINK SOUTH AS A COLD FRONT
INTO PARTS OF CENTRAL NEW YORK AND SOUTHERN VERMONT SATURDAY
NIGHT...SUPPORTING CHANCES FOR FREEZING RAIN IN THE NORTH COUNTRY.
STRONG LOW PRESSURE WILL TRACK NORTHEAST OUT OF THE TENNESSEE AND
OHIO VALLEY SUNDAY AS THE FRONT SURGES NORTH INTO CANADA...
BRINGING LOCALLY HEAVY RAIN AND WARMER TEMPERATURES TO OUR REGION.
A COLD FRONT WILL TRACK THROUGH OUR AREA SUNDAY NIGHT AND MONDAY
MORNING BRINGING A RETURN TO COLDER WEATHER FOR THE BEGINNING OF
NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 1245 PM...RADAR INDICATED FAIRLY WIDESPREAD LIGHT RAIN
OCCURRING OR WILL SHORTLY SPREAD INTO THE NORTHERN THREE-FOURTHS OF
THE FORECAST AREA. HAVE ADJUSTED POPS UPWARD TO LIKELY AND
CATEGORICAL IN THESE AREAS AND INCREASED POPS OVER THE FAR SOUTH TO
SLIGHT OR LOW CHANCE. TEMPS IN THE ADIRONDACK ZONES GENERALLY IN THE
MID OR UPPER 30S SO NO THREAT FOR ANY FREEZING RAIN FOR THE REST OF
TODAY. HAVE ADJUSTED TEMPS HIGHER...ESPECIALLY ACROSS THE HIGHER
TERRAIN WHERE THE WOUTHWEST FLOW HAS SCOURED OUT ANY REMAINING
COLDER AIR. TEMPS OVER THE HIGHER TERRAIN OF THE CATSKILLS ARE
CURRENTLY AROUND 50.
.PREVIOUS DISCUSSION...
AS OF 930 AM EST...RADARS INDICATING SOME LIGHT SPOTTY RETURNS
ACROSS MAINLY OUR NORTHERN AREAS. THE HRRR LOOKS ON CUE...WITH
LIGHTLY PRECIPITATION LIKELY TO FILL IN AS THE AFTERNOON
ARRIVES...DUE TO INCREASED CONVERGENCE AND MOISTURE ALONG AN
APPROACHING BOUNDARY.
TEMPERATURES IN THE VALLEYS GENERALLY IN THE 30S ABOVE FREEZING.
HOWEVER...MESO SITES INDICATED TEMPERATURES INTO THE 40S ACROSS
MAINLY THE HIGHER ELEVATIONS OF CATSKILLS...BUT EVEN ABOVE FREEZING
ACROSS OUR SOUTHERN ADIRONDACKS. SNOW MELT HAS COMMENCE...AND MANY
AREAS WILL LIKELY NOT DROP BACK BELOW FREEZING UNTIL SUNDAY NIGHT.
NO REAL CHANGES WITH THIS PACKAGE...TWEAKED THE POPS (DOWNWARD A
LITTLE IN THE BEGINNING GRIDS) AND OF COURSE RE-TOOLED THE HOURLY
GRIDS. LOOK FOR LOTS OF CLOUDS TODAY...AND AN INCREASING CHANCE OF
MAINLY RAIN SHOWERS THIS AFTERNOON (WITH PERHAPS SOME POCKETS OF
FREEZING RAIN UP NORTH)...MAINLY ALBANY NORTH.
HIGH TEMPERATURES THIS AFTERNOON REACHING 45-50 SOUTH OF CAPITAL
DISTRICT...40-45 CAPITAL DISTRICT AND SURROUNDING PARTS. TO THE
NORTH...HIGHS WILL GENERALLY BE 35-40.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
ONE WEAK UPPER IMPULSE AND WEAK FORCING AFFECTS OUR REGION THIS
AFTERNOON AND TONIGHT. THE BEST COVERAGE OF PRECIPITATION TONIGHT
SHOULD BE NORTH OF THE MOHAWK VALLEY AND WEST OF THE LAKE GEORGE
SARATOGA REGION. HOWEVER...SOLID CHANCES FROM SCHOHARIE VALLEY
THROUGH THE CAPITAL DISTRICT...SOUTHERN VT INTO THE BERKSHIRES AND
EASTERN CATSKILLS. PRECIPITATION AMOUNTS SHOULD BE LIGHT...BUT
NIGHTTIME COOLING IN THE SOUTHERN ADIRONDACKS COULD ALLOW SOME OF
THE PRECIPITATION TO FALL AS FREEZING RAIN...MAYBE UP TO A TENTH
OF AN INCH. HOLDING OFF ON ANY ADVISORIES SINCE TEMPERATURES COULD BE
BORDERLINE AND NEXT SET OF GUIDANCE CAN BE CONSULTED AND STILL GET
LEAD TIME ON AN ADVISORY IF IT NEEDS TO BE ISSUED THIS
AFTERNOON...BUT AGAIN JUST FOR PARTS OF NORTHERN HERKIMER AND
HAMILTON COUNTIES. LOWS TONIGHT IN THE 30S.
STRONGER UPPER ENERGY...FORCING AND MOISTURE ADVECTION APPROACHES
SATURDAY AFTERNOON THROUGH SUNDAY AFTERNOON. RAIN SHOULD SPREAD
ACROSS THE REGION SATURDAY AFTERNOON AND NIGHT...AND BE HEAVY AT
TIMES SATURDAY NIGHT THROUGH SUNDAY. THERE ARE CONSIDERABLE
DISAGREEMENTS IN SOURCES OF GUIDANCE AND ENSEMBLES AS TO HOW MUCH
COLDER AIR SINKS SOUTH SATURDAY NIGHT IN RESPONSE TO ENHANCED UPPER
CONFLUENCE IN CANADA AS UPPER ENERGY TRACKS WELL NORTH OF THE U.S.
CANADIAN BORDER. BASED ON THE SOURCES OF GUIDANCE THAT RESOLVE
THESE ISSUES BEST...SIDING ON SOME COLD AIR DRAINING SOUTH IN
RESPONSE TO ENHANCED AGEOSTROPHIC NORTHERLY LOW LEVEL FLOW...
RESULTING IN SOME POTENTIAL FREEZING RAIN FOR THE SOUTHERN
ADIRONDACKS TO THE LAKE GEORGE AREA. WE WILL SEE HOW THE SNOW PACK
ACROSS THE ENTIRE REGION INFLUENCES SURFACE TEMPERATURES THROUGH
SATURDAY NIGHT AS WELL. WITH SUCH HIGH UNCERTAINTIES IN THE
RAIN/FREEZING RAIN LINE...NO HEADLINES YET UNTIL WE GET CLOSER TO
THE POTENTIAL EVENT. WHATEVER AREAS GET FREEZING RAIN COULD GET UP
TO A QUARTER INCH.
A VERY STRONG BOUNDARY LAYER JET SEGMENT AND ISENTROPIC LIFT...
ALONG WITH ANOMALOUSLY HIGH PWAT...SHOULD SUPPORT A HEAVY
RAIN EVENT...AND COMBINED WITH SNOW MELT...COULD RESULT IN SOME
FLOODING POTENTIAL. THIS WILL BE ADDRESSED IN THE HWO AS RAINFALL
FORECASTS FROM SOURCES OF GUIDANCE AND ENSEMBLES STILL A BROAD
RANGE AND AXIS OF HEAVIEST RAIN COULD FALL NORTH OF WHERE MAXIMUM
SNOW MELT OCCURS. A WEST TO SOUTHWEST BOUNDARY LAYER FLOW USUALLY
RESULTS IN THE HEAVIEST PRECIPITATION IN THE ADIRONDACKS...WHICH
AGAIN MAY SEE THE LEAST WARM TEMPERATURES AND LEAST SNOW MELT.
SO...STILL HOLDING OFF ON ANY FLOOD WATCHES.
HIGHS SATURDAY IN THE 40S TO AROUND 50...WITH LOWS SATURDAY NIGHT
AROUND 40 TO THE MID 40S...LOWER TO MID 30S IN THE NORTH COUNTRY.
HIGHS SUNDAY IN THE 50S MANY AREAS...BUT INTO THE 60S TOWARD POU
AND NW CT...AND IN THE 40S IN THE NORTH COUNTRY. THE COLD
FRONT TRACKS THROUGH THE REGION SUNDAY NIGHT AND SHOWERS SHOULD
CHANGE TO SNOW SHOWERS AS COLD AIR SPREADS ACROSS THE REGION.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
HAVE GENERALLY POPULATED THIS PORTION OF THE GRIDDED DATABASE WITH
00Z/20 HPC GUIDANCE.
MON-TUE...THE COLD FRONT ASSOCIATED WITH THIS WEEKEND/S STORM SYSTEM
SHOULD BE EXITING THE REGION MON AM...WITH RAIN SHOWERS TAPERING
OFF...BUT PROBABLY CHANGING TO SNOW SHOWERS BEFORE ENDING FOR AREAS
N AND W OF ALBANY. IN THE WAKE OF THE SFC FRONT...THE UPPER LEVEL
TROUGH WILL GRADUALLY TRANSLATE EASTWARD...PASSING ACROSS THE REGION
LATE MON NT OR ON TUE. THE COMBINATION OF THE ASSOCIATED COLD
POOL...AND COLDER AIR POURING ACROSS THE GREAT LAKES WILL LIKELY
LEAD TO AT LEAST SCATTERED SNOW SHOWERS AND FLURRIES FROM LATE
MONDAY INTO TUESDAY...ALONG WITH THE POSSIBILITY OF SOME LAKE EFFECT
SNOWBANDS SOMEWHERE ACROSS THE WESTERN ADIRONDACKS AND/OR MOHAWK
VALLEY...WHICH COULD OCCASIONALLY EXTEND INTO THE CAPITAL REGION AND
BERKSHIRES/SOUTHERN GREEN MTNS. AS FOR TEMPS...EXPECT MAXES TO REACH
THE 30S TO LOWER 40S MON IN VALLEY AREAS...AND 20S TO LOWER 30S
ACROSS HIGHER ELEVATIONS...WITH MOST MAX TEMPS LIKELY OCCURRING IN
THE MORNING WITH FALLING AFTERNOON TEMPS. FOR MON NT...EXPECT TEMPS
TO FALL INTO THE SINGLE DIGITS AND TEENS ACROSS NORTHERN AREAS...AND
TEENS AND LOWER/MID 20S FOR CENTRAL AND SOUTHERN AREAS. ON
TUE...EXPECT MAX TEMPS TO ONLY REACH THE SINGLE DIGITS AND LOWER
TEENS ACROSS MUCH OF THE SOUTHERN ADIRONDACKS...WITH MAINLY 20S FOR
VALLEY AREAS.
TUE NT-WED NT...HIGH PRESSURE WILL THEN BUILD IN FOR TUE
NT-WED...WHILE A WEAK CLIPPER TYPE SYSTEM PASSES BY TO OUR N AND W
WED NT. HAVE INCLUDED SOME SLIGHT CHC POPS FOR WED NT ACROSS
PORTIONS OF THE WESTERN ADIRONDACKS. AS FOR TEMPS...EXPECT TUE
NT/WED AM MINS TO FALL INTO THE SINGLE DIGITS AND TEENS IN MOST
AREAS...WITH SOME READINGS POSSIBLY FALLING TO BETWEEN ZERO AND 5
BELOW ACROSS PORTIONS OF THE SOUTHERN ADIRONDACKS. ON WED...EXPECT
MAX TEMPS TO REACH 25-30 IN VALLEY AREAS...AND UPPER TEENS TO LOWER
20S ACROSS HIGHER ELEVATIONS. FOR WED NT/THU AM...EXPECT MINS TO
FALL INTO THE TEENS AND 20S IN MOST AREAS.
THU...THE 00Z/20 ECMWF CONTINUES TO HINT AT A WEAK COASTAL SYSTEM
OFF THE SE COAST POTENTIALLY PHASING WITH SOME ENERGY ACROSS THE
GREAT LAKES TO ALLOW FOR LIGHT PRECIPITATION TO DEVELOP ACROSS THE
REGION. ALTHOUGH THE DETERMINISTIC 00Z/20 GFS IS NOT QUITE AS
EMPHATIC WITH THIS PHASING...SOME MEMBERS OF THE 00Z/20 GEFS DO
INDEED DEPICT SOME FORM OF THIS...WITH SOME SIGNAL NOTED IN THE MEAN
GEFS. WILL THEREFORE INDICATE CHC POPS...MAINLY FOR SNOW ON
THU...WITH PERHAPS A RAIN/SNOW MIX FOR SOUTHERN AREAS. AS FOR
TEMPS...HAVE INDICATED MAXES REACHING THE 35-40 IN MOST
VALLEYS...AND 25-30 FOR HIGHER ELEVATIONS.
&&
.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
MAINLY VFR LEVEL CLOUDS PERSIST ACROSS THE REGION...WITH BASES OF
3500-6000 FT AGL CONFINED MAINLY TO KGFL/KALB...WITH MUCH HIGHER
CIGS FURTHER SOUTH AND EAST. SOME SPRINKLES MAY OCCUR NEAR OR
NORTH OF KGFL OVER THE NEXT 2 HOURS.
THROUGH THE DAY...SKIES SHOULD REMAIN MOSTLY CLOUDY...BUT
INITIALLY CIGS SHOULD REMAIN VFR. HOWEVER...SOME AREAS OF LIGHT
RAIN SHOWERS WILL DEVELOP AROUND MIDDAY FOR KGFL/KPSF/KALB...WITH
CIGS GRADUALLY LOWERING INTO THE MVFR RANGE IN THESE AREAS. THE
SHOWERS SHOULD REMAIN NORTH OF KPOU...WHERE VFR CONDITIONS SHOULD
CONTINUE THROUGH THE DAY.
OCCASIONAL LIGHT RAIN OR DRIZZLE WILL CONTINUE OVERNIGHT FOR
KGFL/KALB AND KPSF...WHILE REMAINING GENERALLY NORTH OF KPOU.
CIGS/VSBYS WILL CONTINUE TO BE MAINLY MVFR AT
KGFL/KALB/KPSF...WITH SOME OCCASIONAL IFR CONDITIONS
POSSIBLE...ESP AFTER 05Z/SAT. AT KPOU...THE VSBY MAY LOWER INTO
THE MVFR RANGE LATER TONIGHT.
WINDS WILL BE SOUTHERLY LESS THAN 10 KT THROUGH 12Z SATURDAY.
OUTLOOK...
SATURDAY NIGHT: HIGH OPERATIONAL IMPACT. DEFINITE RA.
SUNDAY: HIGH OPERATIONAL IMPACT. LIKELY RA.
SUNDAY NIGHT: MODERATE OPERATIONAL IMPACT. CHANCE OF SHRA.
MONDAY: MODERATE OPERATIONAL IMPACT. SLIGHT CHANCE OF SHRA...SHSN.
MONDAY NIGHT: MODERATE OPERATIONAL IMPACT. SCATTERED SHSN.
TUESDAY: LOW OPERATIONAL IMPACT.BREEZY ISOLATED SHSN.
TUESDAY NIGHT: NO OPERATIONAL IMPACT. NO SIG WX.
CHRISTMAS DAY: NO OPERATIONAL IMPACT. NO SIG WX.
&&
.HYDROLOGY...
WARMER TEMPERATURES WILL HAPPEN FRIDAY INTO THE WEEKEND...WITH A
FRONTAL BOUNDARY BRINGING SOME SHOWERS AND MIXED PRECIPITATION TO
CLOSE THE WORK WEEK. SOME SNOW MELT IS LIKELY BY THIS WEEKEND.
ALSO...A STORM SYSTEM MOVING ALONG A FRONTAL BOUNDARY MAY BRING
SIGNIFICANT PCPN TO THE FORECAST AREA SAT NIGHT INTO SUNDAY WITH
EVEN MILDER TEMPS.
TEMPERATURES SUNDAY ARE EXPECTED TO WARM INTO THE 50S OR POSSIBLY
EVEN 60S ACROSS THE EASTERN CATSKILLS...MID HUDSON VALLEY...CENTRAL
AND SOUTHERN TACONICS INTO THE BERKSHIRES AND ACROSS LITCHFIELD
COUNTY WITH 50S ACROSS THE CAPITAL REGION...40S FURTHER NORTH.
BETWEEN THE RAIN AND RUNOFF FROM SNOWMELT DUE TO THE MILD/WARM
TEMPERATURES SOME FLOODING COULD BE A PROBLEM INCLUDING ICE JAMS
ISSUES. AT THIS POINT...WE BELIEVE MOST IF NOT ALL OF THE SNOW COULD
BE MELTED FROM ABOUT THE MOHAWK RIVER...FURTHER NORTH TEMPERATURES
MIGHT NOT BE WARM ENOUGH TO MELT ALL OF THE SNOW.
THE POTENTIAL IS THERE FOR 1-2 INCHES OF RAINFALL FROM ALBANY
NORTHWARD...POSSIBLY SOME AREAS REACHING 3 INCHES. LESS AMOUNTS OF
RAIN LOOK TO FALL SOUTH OF THE CAPITAL REGION...AN INCH OR LESS.
WILL KEEP MENTION OF IN OUR HAZARDOUS WEATHER OUTLOOK.
FOR DETAILS ON SPECIFIC AREA RIVERS AND LAKES...INCLUDING OBSERVED
AND FORECAST RIVER STAGES AND LAKE ELEVATIONS...PLEASE VISIT THE
ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
MA...NONE.
VT...NONE.
&&
$$
SYNOPSIS...HWJIV/NAS
NEAR TERM...GJM/HWJIV
SHORT TERM...NAS
LONG TERM...KL
AVIATION...KL
HYDROLOGY...NAS
AREA FORECAST DISCUSSION
NWS TAMPA BAY RUSKIN FL
205 PM EST FRI DEC 20 2013
...NEAR RECORD HIGH TEMPERATURES THIS WEEKEND...
...WINTER OFFICIALLY BEGINS JUST AFTER NOON EST ON SATURDAY...
.SYNOPSIS...
19Z WATER VAPOR AND H4 RAP ANALYSIS SHOWS AN AMPLIFYING UPPER LEVEL
PATTERN OVER THE CONUS. LONGWAVE TROUGHING NOW COVERS THE NATION TO
THE WEST OF THE CONTINENTAL DIVIDE...AND IS HIGHLIGHTED BY A POTENT
SHORTWAVE/CLOSED LOW FEATURE EJECTING EASTWARD OVER THE SW STATES
AND NORTHERN MEXICO. THE ADVANCEMENT OF THIS WESTERN TROUGH AND
ASSOCIATED HEIGHT FALLS HAVE HELPED TO "RIDGE UP" THE DOWNSTREAM
FLOW FROM THE EASTERN GULF OF MEXICO TO THE MID-ATLANTIC STATES.
THIS RIDGE OVER OUR HEADS WILL BE OUR PROTECTOR THROUGH THE UPCOMING
WEEKEND AND PROVIDE A GENERALLY FAIR AND UNSEASONABLY WARM FORECAST.
WV IMAGERY SHOWS SOUTHERN STREAM MOISTURE RAPIDLY ADVECTING
NORTHWARD ACROSS THE SOUTHERN PLAINS AHEAD OF THE STRONG SOUTHWEST
SHORTWAVE. THIS MOISTURE RETURN IS THE FIRST STAGE IN THE PRIMING OF
THE ATMOSPHERE FOR A POTENTIALLY SIGNIFICANT SEVERE WEATHER OUTBREAK
ACROSS THE LOWER MS VALLEY DURING SATURDAY. HOWEVER...AS MENTIONED
ABOVE THIS INCLEMENT WEATHER IS NOT IN OUR FORECAST WITH THE UPPER
RIDGE IN PLACE. 20/12Z KTBW SOUNDING...ALTHOUGH STILL ON THE DRY
SIDE...SHOWS THAT WE HAVE SEEN SOME MOISTURE RETURN THROUGH THE
COLUMN DURING THE PAST 24 HOURS...WITH THE PW VALUE JUMPING FROM
0.27" ON THURSDAY MORNING TO AROUND AN INCH THIS MORNING. MUCH OF
THIS MOISTURE RETURN HAS BEEN IN THE LOWER LEVELS BELOW A WELL
DEFINED SUBSIDENCE INVERSION (ASSOCIATED WITH THE UPPER RIDGING)
JUST ABOVE 700MB.
AT THE SURFACE...HIGH PRESSURE RIDGES BACK FROM THE WESTERN ATLANTIC
TO THE GA/CAROLINA COAST...PLACING OUR REGION WITHIN A LIGHT
SOUTHEAST FLOW REGIME. THIS FLOW HAS BEEN ADVECTING INCREASING
LEVELS OF BOUNDARY LAYER MOISTURE ACROSS THE PENINSULA...AND THESE
MOISTURE LEVELS WILL ONLY CONTINUE TO INCREASE THROUGH THE NEXT 24
HOURS. TEMPERATURES ARE APPROACHING OR SURPASSING 80 DEGREES AT MOST
STATIONS THIS MID-AFTERNOON.
&&
.SHORT TERM (TONIGHT THROUGH SUNDAY NIGHT)...
TONIGHT...A WARM AND FAIR OVERNIGHT PERIOD. THE CONTINUED MOISTURE
ADVECTION WITHIN THE LIGHT SE FLOW REGIME WILL PREVENT LOW TEMPS
FROM DROPPING OUT OF THE 60S FOR JUST ABOUT ALL AREAS. BOUNDARY
LAYER MOISTURE UNDERNEATH THE SUPPRESSION ALOFT DOES SET UP A
FAVORABLE SCENARIO FOR PATCHY/AREAS OF FOG DURING THE LATE NIGHT
HOURS. A WIDESPREAD DENSE FOG EVENT IS UNLIKELY...BUT LOCALIZED
AREAS OF REDUCED VISIBILITY ARE A GOOD BET FOR ANYONE DOING EARLY
TRAVELING SATURDAY MORNING. BOTH STATISTICAL MOS AND ENSEMBLE SREF
PROBS SUGGEST THIS FOG POTENTIAL.
SATURDAY...UNSEASONABLY WARM TEMPERATURES TO START OUT THE WEEKEND
UNDER AN UPPER RIDGE CHARACTERIZED BY H5 HEIGHTS OF 1.5-2 STANDARD
DEVIATIONS ABOVE CLIMO. GRADIENT WILL INCREASE SOMEWHAT AND SHOULD
HELP PREVENT MUCH IF ANY SEABREEZE DEVELOPMENT...OR AT LEAST INLAND
PENETRATION...DESPITE THE STRONG TERRESTRIAL HEATING. THEREFORE...
HAVE A RAIN FREE DAY IN THE FORECAST. THE STRONGER GRADIENT WILL
RESULT IN EVEN MORE EFFICIENT DIURNAL MIXING WITHIN A VERY WARM
POTENTIAL COLUMN WITH 850MB TEMPS AROUND 16C. THESE 850MB TEMPS ARE
ALSO 1.5-2 STANDARD DEVIATIONS ABOVE CLIMO. COMBINE ALL THIS AND WE
ARE LOOKING AT NEAR RECORD TEMPERATURES FOR THE WINTER SOLSTICE...
WITH LOWER 80S FAR NORTH AND WIDESPREAD MIDDLE 80S ELSEWHERE. BELOW
IS A SELECT LISTING OF SOME OF THE RECORD TEMPERATURES FOR DEC 21ST
ACROSS THE AREA:
BROOKSVILLE...86
FORT MYERS....87
LAKELAND......82
SARASOTA......86
PUNTA GORDA...84
ST PETERSBURG.82
TAMPA INTL....85
WINTER HAVEN..85
SUNDAY...
THE SYNOPTIC PATTERN OVER THE FLORIDA PENINSULA DOES NOT CHANGE MUCH
ON SUNDAY WITH THE MID/UPPER LEVEL RIDGE CONTINUING TO PROTECT THE
REGION FROM THE STORM SYSTEM TO OUR NORTHWEST. IT WILL NOT BE UNTIL
LATER SUNDAY NIGHT INTO MONDAY THAT THE RIDGE BEGINS TO BREAK DOWN
AND ALLOW A COLD FRONT TO FINALLY APPROACH. ONCE AGAIN LOOKING FOR
AREAS OF FOG TO BE AROUND THE REGION LATE SATURDAY NIGHT INTO EARLY
SUNDAY MORNING. ONCE THIS FOG AND LOWER CLOUDS BURN OFF...EXPECT A
MIX OF SUN AND CLOUDS AND NEAR RECORD TEMPERATURES REACHING THE
LOWER TO MIDDLE 80S ALMOST REGION-WIDE. A SLIGHTLY WEAKER GRADIENT
MAY ALLOW AN ONSHORE COMPONENT OF WIND TO DEVELOP NEAR THE COAST
DURING THE AFTERNOON WHICH WOULD ONLY SERVE TO KNOCK TEMPS AT THE
BEACHES BACK INTO THE 70S.
&&
.LONG TERM (MONDAY THROUGH NEXT THURSDAY)...
NO SIGNIFICANT CHANGES TO THE EXTENDED FORECAST AS THE UPPER
DISTURBANCE CENTERED OVER SOUTHERN CALIFORNIA EARLY THIS MORNING IS
FORECAST TO PROPAGATE TO THE EAST TODAY AND BECOME NEGATIVELY TILTED
OVER TEXAS AND OKLAHOMA ON SATURDAY BEFORE SHEARING OFF TO THE
NORTHEAST SUNDAY WITHIN A DEEP LAYERED TROUGH. MEANWHILE ACROSS
FLORIDA...ABOVE NORMAL TEMPERATURES WILL PREVAIL THROUGH THE PERIOD
WITH MOIST SPRING-LIKE DEW POINTS EXPECTED SUNDAY NIGHT THROUGH MUCH
OF MONDAY BEFORE THE FRONTAL PASSAGE. THE COLD FRONT ASSOCIATED
WITH THE AFOREMENTIONED TROUGH PUSH ACROSS THE FORECAST AREA AT A
FAIRLY PROGRESSIVE CLIP FROM NORTHWEST TO SOUTHEAST...STARTING EARLY
MONDAY ACROSS THE NATURE COAST AND OVER THE REMAINDER OF THE AREA
THROUGH MONDAY NIGHT. MUCH OF THE AREA WILL CLEAR OUT TUESDAY AND
CHRISTMAS DAY WEDNESDAY BEFORE A WEAK VORT MAX PASSES OVER THE
REGION WITHIN A SOUTHWEST MID-UPR LEVEL FLOW AND FORCES WEAK
ISENTROPIC UPGLIDE TO PRODUCE CLOUDINESS AND SOME LIGHT SHOWERS
LATER IN THE PERIOD.
&&
.AVIATION...
20/18Z-21/18Z...PREVAILING VFR FOR THE REST OF TODAY WITH SCT TO LCL
BKN CLOUDS AND POSSIBLY ISOLD SHRA BUT WITH LITTLE IMPACT ON THE
TERMINALS. SE WINDS WITH SOME GUSTS DURING THIS AFTERNOON.
INCREASING LOW-LEVEL MOISTURE WILL RESULT IN MVFR VSBY OR CIGS
TOWARD SUNRISE SAT THEN VFR AFTER 14-15Z. SE WINDS CONTINUE AND
BECOME GUSTY SAT.
&&
.MARINE...
HIGH PRESSURE SHIFTING EASTWARD INTO THE ATLANTIC HAS ALLOWED WINDS
OVER THE EASTERN GULF TO SHIFT FROM EASTERLY TO SOUTHEASTERLY. A
SLOW MOVING COLD FRONT WILL APPROACH THE EASTERN GULF WATERS DURING
THE SECOND HALF OF THE UPCOMING WEEKEND...BUT NOT PASS THROUGH THE
WATERS UNTIL THE EARLY PART OF NEXT WEEK. AHEAD OF THE APPROACHING
COLD FRONT THE PRESSURE GRADIENT WILL TIGHTEN WHICH WILL SUPPORT
WINDS AND SEAS APPROACHING CAUTIONARY LEVELS AT TIMES LATE TONIGHT
THROUGH SUNDAY...ESPECIALLY AWAY FROM SHORE.
&&
.FIRE WEATHER...
LOW LEVEL MOISTURE CONTINUES TO INCREASE ACROSS THE REGION AND WILL
PREVENT ANY CHANCE OF CRITICALLY LOW RELATIVE HUMIDITY LEVELS THE
NEXT SEVERAL DAYS. A FRONT WILL APPROACH LATE IN THE WEEKEND...BUT
WILL NOT CROSS THE FLORIDA PENINSULA UNTIL THE EARLY PORTION OF NEXT
WEEK. FIRE WEATHER CONCERNS THROUGH THE WEEKEND WILL INCLUDE
ELEVATED DISPERSION INDICES BOTH SATURDAY AND SUNDAY AFTERNOON AND
THE POTENTIAL FOR AREAS OF LATE NIGHT AND EARLY MORNING FOG BOTH
FRIDAY NIGHT AND SATURDAY NIGHT.
&&
.PRELIMINARY POINT TEMPS/POPS...
TPA 68 84 68 82 / 10 10 10 10
FMY 67 86 67 84 / 10 10 10 10
GIF 62 84 65 85 / 10 10 10 10
SRQ 66 83 66 81 / 10 10 10 10
BKV 64 85 64 84 / 10 10 10 10
SPG 68 81 68 81 / 10 10 10 10
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GULF WATERS...NONE.
&&
$$
SYNOPSIS/SHORT TERM/MARINE/FIRE WX...MROCZKA
AVIATION...RUDE
LONG TERM...LAMARRE
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
416 PM CST FRI DEC 20 2013
.DISCUSSION...
337 PM CST...INCLUDING UPDATED WINTER STORM DISCUSSION BELOW...
TONIGHT THROUGH SATURDAY MORNING...
325 PM CST...
TONIGHT...THE FREEZING RAIN ADVISORY CONTINUES THROUGH 7 PM FOR
FAR NORTHERN IL AS LIGHT SHOWER ACTIVITY AND PATCHY DRIZZLE
CONTINUE TO OVERRIDE A SUBFREEZING BOUNDARY LAYER. THE GOES WATER
VAPOR LOOP SHOWS MODEST DRYING OVER THE AREA IN THE MID-
LEVELS...BUT JUST ENOUGH WEAK ASCENT APPEARS TO BE PRESENT WITHIN
THE LOW-LEVEL SATURATION TO KEEP TRIGGERING THESE LIGHT SHOWERS.
THE FREEZING DEMARCATION HELD STEADY MUCH OF TODAY FROM NEAR
MENDOTA NORTHEAST TO LAKE COUNTY IL. DO NOT SEE MUCH SHIFT WITH
THAT THROUGH EARLY THIS EVE. SO WITH IT BEING A BUSY HOLIDAY
TRAVEL TIME ADDED TO THE NORMAL FRIDAY COMMUTE...CERTAINLY LET THE
ADVISORY CONTINUE TO 7 PM. AS TEMPERATURES SLOWLY FALL BELOW
FREEZING SOUTH OF THE ADVISORY...UNTREATED WET ROADWAYS ARE LIKELY
TO EXPERIENCE SOME GLAZING TOO.
THE DENSE FOG ADVISORY FOR SOUTHERN AREAS SHOULD BE FINE ENDING AT 7
PM AS WINDS BEGIN TO INCREASE BEHIND THE BOUNDARY AND LOWER DEW
POINTS SEEP IN.
FORCING REMAINS WEAK THROUGH MUCH OF TONIGHT WITH LIMITED MOISTURE
TRANSPORT AND REALLY ANY TYPE OF MID-LEVEL WAVE/TRIGGER. SO WHILE
THERE IS A CHANCE FOR FREEZING DRIZZLE...ANY PRECIP SHOULD BE PATCHY
AT BEST AND LIGHT AFTER 7-8 PM.
SATURDAY MORNING...THE RAP AND OTHER HIGH RES GUIDANCE KEY IN ON
MOISTURE TRANSPORT AHEAD OF THE MAIN DEVELOPING SYSTEM /DESCRIBED
BELOW/ ADVANCING INTO THE SOUTHERN CWA IN THE PRE-DAWN HOURS AND
INTO SAT MORNING. THE CONVERGENCE AT THE NOSE OF THIS CREEPS INTO
THE SOUTHERN FORECAST AREA IN THE MORNING...WHERE FREEZING DRIZZLE
AND RAIN LOOK POSSIBLE...THOUGH THERE COULD BE QUITE A BIT OF RAIN
AND CONVECTIVE ACTIVITY ACROSS THE MID-MISSISSIPPI VALLEY THAT MAY
HALT THE FRONT EDGE ADVANCE OF THE PRECIP. HAVE CONTINUED MENTION
OF LIGHT FREEZING PRECIP SAT MORNING ACROSS AREAS MAINLY SOUTH OF
I-80.
MTF
DISCUSSION ON WINTER STORM.
WE HAVE UPGRADED PORTIONS OF THE WINTER STORM WATCH TO WARNING AND
CONTINUED THE WATCH FOR LAKE AND KANE COUNTIES.
THE VIGOROUS MID LEVEL FEATURE...CURRENTLY NOTED IN WATER VAPOR NEAR
THE BAJA OF CALIFORNIA EARLY THIS AFTERNOON IS FORECAST TO TAKE ON A
NEGATIVE TILT AS IT MOVES OUT ACROSS THE TEXAS PANHANDLE AROUND
MIDDAY ON SATURDAY. THIS FEATURE WILL LIFT QUICKLY
NORTH-NORTHEASTWARD ACROSS THE MID MISSISSIPPI VALLEY AND ACROSS
NORTHERN ILLINOIS SATURDAY NIGHT. MODEL GUIDANCE CONTINUES TO WAVER
AROUND A BIT ON THE ACTUAL TRACK OF THE 850 AND SURFACE LOWS.
THEREFORE...I HAVE TRENDED CLOSER TO THE ENSEMBLE MEANS...WHICH
TRACK THE 850 LOW RIGHT ACROSS NORTHEASTERN ILLINOIS LATE SATURDAY
NIGHT. THIS TRACK FAVORS NORTH CENTRAL AND FAR NORTHEASTERN ILLINOIS
FOR THE HEAVIEST SNOWFALL...ESPECIALLY SATURDAY NIGHT INTO EARLY
SUNDAY AS STRONG FRONTOGENESIS SETS UP WITHIN THE DEFORMATION
ZONE...JUST TO THE NORTH AND WEST OF THE 850 LOW TRACK. THIS WILL
LIKELY SUPPORT AN AREA OF HEAVY SNOWFALL ACROSS THESE AREAS...WITH
SNOW RATES LIKELY TO REACH OR EVEN EXCEED AN 1 INCH PER HOUR AT
TIMES...GIVEN THE GOOD COUPLING OF THE LARGE SCALE FORCING FOR
ASCENT FROM THE MID LEVEL WAVE AND THE GOOD FRONTOGENESIS. MID LEVEL
LAPSE RATES WILL ALSO SUPPORT GOOD SNOWFALL ACROSS THE WARNING
AREAS. I CHOSE TO LEAVE THE WATCH IN PLACE FOR LAKE AND KANE
COUNTIES. THESE AREAS MAY ALSO SEE 6+ INCHES OF SNOW...IN PORTIONS
OF THE COUNTIES...BUT DUE TO THE POTENTLY FOR SOME SLIGHT SHIFTS YET
IN THE TRACK OF THE SYSTEM...WITH A POTENTIAL FOR A FARTHER
NORTHWEST TRACK...I CHOOSE TO HOLD OFF.
THE OTHER CONCERN IS THE THREAT FOR FREEZING RAIN AND SLEET
ACCUMULATIONS...ESPECIALLY ACROSS SOUTHERN SECTIONS OF THE WARNING
AREA...AND PLACES TO THE SOUTH. TEMPERATURES ARE EXPECTED TO REMAIN
RIGHT AROUND THE FREEZING POINT...SO IT APPEARS THAT ICING AMOUNTS
MAY BE LIMITED SOME...ESPECIALLY NEAR CHICAGO. WITH THAT BEING
SAID...I STILL THINK THERE IS A DECENT POTENTIAL TO HAVE AN AREA OF
SOME ICE ACCUMULATIONS...OF 0.1 TO 0.2 INCHES...PRIMARILY NORTH OF
I-80 UP TO AROUND THE I-88 CORRIDOR. CLOSER TO THE LAKE AND THE
CITY ICE AMOUNTS MAY BE LESS DUE TO THE FLOW OFF THE LAKE POSSIBLY
RESULTING IN TEMPS JUST ABOVE FREEZING. IT APPEARS THE MAIN ICING
THREAT WILL NOT OCCUR UNTIL TOMORROW AFTERNOON AND INTO THE
EVENING. THEREFORE...WE HAVE SOME TIME TO BETTER IRON OUT THE
AREAS MOST SUSCEPTIBLE TO ICING. WE WILL HIGHLIGHT THIS THREAT IN
AN SPS.
IT ALSO APPEARS THE HEAVY RAIN THREAT WILL MAINLY BE ACROSS MY
SOUTHEASTERN COUNTIES...SO NO CHANGES TO THE GOING FLOOD WATCH.
STRONG MOISTURE CONVERGENCE AND ANOMALOUSLY HIGH PWATS WILL LIKELY
PRODUCE AMOUNTS IN EXCESS OF AN INCH OR SO ACROSS THESE AREAS...AND
WITH ALL OF THIS BECOMING RUNOFF...RAPID RISES ON AREA STREAMS ARE
EXPECTED.
THE SNOW THREAT FOR AREAS SOUTH OF THE CURRENT WARNING AREA APPEAR
TO SOMEWHAT LIMITED...WITH A SHARP GRADIENT IN THE SNOW
ACCUMULATIONS EXPECTED. AN IMPRESSIVE DRY SLOT WILL PUNCH IN ACROSS
THE AREA LATE SATURDAY NIGHT INTO SUNDAY...LIKELY RESULT IN ONLY
LIGHT SNOW OR EVEN FZ DRIZZLE GIVEN THE LOSE OF ICE IN THE CLOUDS.
TOTAL SNOW AMOUNTS LOOK TO DROP TO UNDER AN INCH BY THE TIME YOU GET
CLOSE TO CHICAGO AND INTERSTATE 80.
MUCH COLDER AIR SPILLS IN ACROSS THE AREA SUNDAY NIGHT...WITH LIGHT
PRECIP CONTINUING IN ASSOCIATION WILL ANOTHER UPPER LEVEL
DISTURBANCE. TEMPERATURES WILL LIKELY DROP INTO THE SINGLE DIGITS
IN MOST AREAS SUNDAY NIGHT. THUS...ANY STANDING WATER
REMAINING...WITH LIKELY QUICKLY FREEZE IN PLACE ACROSS THE AREA.
KJB
EXTENDED FORECAST PERIOD /MONDAY MORNING THROUGH FRIDAY INCLUDING
THE CHRISTMAS HOLIDAY...
300 PM CST...
THE SENSIBLE WEATHER WILL QUIET CONSIDERABLY WITH THE MAIN FORECAST
CONCERNS FOCUSING ON TEMPERATURES AND THE CHANCE FOR SOME LIGHT
SNOW ON CHRISTMAS EVE AND EARLY CHRISTMAS DAY. THE GENERAL TREND
FOR THE EXTENDED FORECAST PERIOD WILL BE FOR MUCH BELOW NORMAL
TEMPERATURES WITH THE ONLY CHANCE FOR SOME LIGHT SNOW ON CHRISTMAS
EVE INTO CHRISTMAS DAY.
A HIGH AMPLITUDE LONGWAVE TROUGH IS EXPECTED TO CARVE OUT OVER THE
CNTRL CONUS WITH THE TROUGH AXIS EXTENDING FROM HUDSON BAY THROUGH
CENTRAL TEXAS. INITIALLY ON MONDAY...THE LOCAL AREA WILL SEE THE
TROUGH AXIS MOVING THROUGH THE AREA TRANSITIONING THE REGION FROM
RELATIVE WARM ADVECTION TO STRONG COLD ADVECTION. TEMPERATURES WILL
DROP OFF QUICKLY BY MONDAY MORNING...WITH LOWS EXPECTED TO DROP ONTO
THE SINGLE DIGITS WEST OF THE FOX VALLEY AND I-55 CORRIDOR. LOWS
OVER THE EASTERN PORTION OF THE FORECAST AREA SHOULD HANG IN THE
MIDDLE TO UPPER TEENS. AS THE LONGWAVE TROUGH CONTINUES TO THE ERN
CONUS MONDAY AND MONDAY NIGHT...WEAK UPPER RIDGING WILL BUILD ACROSS
THE UPPER MISSISSIPPI VALLEY...WITH THE AMPLITUDE OF THE UPPER LEVEL
PATTERN CONTINUING TO AMPLIFY. WITH DEEP LAYER FLOW REMAINING ON
THE NWLY FLOW SIDE OF THE UPPER RIDGE...TEMPERATURES WILL CONTINUE
TO DROP WITH LOWS TUESDAY MORNING BELOW ZERO OVER MUCH OF THE CWA...
GENERALLY WEST OF A LINE FROM WAUKEGAN TO PONTIAC...WITH THE
COLDEST AIR OVER THE ROCKFORD AREA WHERE TEMPS SHOULD BOTTOM OUT AT
-5F TO -10F. WIND CHILLS WILL BE A CONCERN AS WELL. WITH WINDS OF
5-10 KT LIKELY...WIND CHILLS WILL APPROACH THE -20F WIND CHILL
ADVISORY CRITERIA WEST OF THE FOX VALLEY AND I-55 CORRIDOR. BY
TUESDAY NIGHT...THE LONGER RANGE MODELS ARE ADVERTISING A PAIR OF
NORTHERN STREAM SHORTWAVES TRACKING ACROSS THE NRN PLAINS. THE
NRN-MOST WAVE...WHICH IS ALSO THE STRONGER OF THE PAIR...SHOULD
TRACK TO THE EAST...ACROSS THE UPPER GREAT LAKES WHILE THE MORE
SOUTHERLY...WEAKER WAVE DROPS THROUGH THE NRN PLAINS TO THE MIDDLE
MISSISSIPPI VALLEY. THIS THERE IS SOME DISCREPANCY AMONG THE LONGER
RANGE GUIDANCE ON THE SPEED OF PROGRESSION OF THIS WAVE...BUT THE
GENERAL CONSENSUS IS THAT THE WAVE WILL CROSS THE MIDDLE MISSISSIPPI
VALLEY...TRACKING OVER THE IL/WI BOARDER. FOLLOWING A PERIOD OF
STRONG COLD/DRY ADVECTION...THERE WILL BE LITTLE IN SITU MOISTURE
FOR THE SYSTEM TO WORK WITH AND WILL LARGELY HAVE TO RELY ON
DYNAMICS TO PRODUCE ANY PCPN. AT THIS POINT...ANTICIPATE THAT UPPER
DYNAMICS SHOULD BE STRONG ENOUGH TO PRODUCE AT LEAST SOME LIGHT SNOW
FOR LATE CHRISTMAS EVE INTO EARLY CHRISTMAS DAY. GIVEN THE LACK OF
DEEP LAYER MOISTURE OR ANY SIGNIFICANT LOW LEVEL MOISTURE TRANSPORT
AS FLOW THROUGH THE LOWER LEVELS SHOULD BE MORE WESTERLY AND UNABLE
TO TAP ANY GULF MOISTURE...ANY ACCUMULATIONS WILL LIKELY BE LIGHT.
A BRIEF PERIOD OF MORE WLY OR AT LEAST BROAD...FLAT TROUGHING SHOULD
COVER THE MIDWEST ON WEDNESDAY...ALLOWING FOR SOME MODERATION OF
TEMPERATURES ON WEDNESDAY AND THURSDAY...WITH HIGHS IN THE UPPER 20S
TO LOWER 30S ON WEDNESDAY AND UPPER TEENS TO MIDDLE 20S ON THURSDAY.
A REINFORCING SHOT OF COLD AIR ASSOCIATED WITH A STRONG NORTHERN
STREAM SHORTWAVE DIGGING INTO THE UPPER MISSISSIPPI VALLEY AND
SOUTHERN GREAT LAKES WILL BRING SUB-ZERO TEMPERATURES BACK TO MUCH
OF THE CWA FOR FRIDAY MORNING.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 22Z...
* NNE WINDS BECOMING NNW 02Z/8 PM CST-ISH THIS EVENING.
* CONTINUED IFR CIGS/MVFR VSBY WITH SOME LGT DZ/BR.
* NE WINDS AGAIN BY MID-MORNING SATURDAY.
* MIXED PCPN...IP/RA/FZRA POTENTIAL SAT AFTN/EVE.
RATZER
//DISCUSSION...UPDATED 18Z...
SO FAR AT MDW/ORD/GYY THE TEMPERATURES HAVE REMAINED ENOUGH ABOVE
FREEZING THAT ICE AT THE SFC HAS NOT BEEN A PROBLEM. DPA HAS BEEN
RIGHT ON THE LINE BUT STILL ABOVE FREEZING...WHILE RFD HAS BEEN
HAVING CONSIDERABLE ICE PROBLEMS. RADAR TRENDS SUGGEST ORD/MDW
PRECIP MAY END A BIT SOONER THAN PREVIOUSLY EXPECTED THIS
AFTERNOON...AND FCST SOUNDINGS SUGGEST INCOMING COLD AIR WOULD
PRODUCE ONLY A BRIEF PERIOD OF LIGHT FREEZING DRIZZLE AT WORST.
AFTER A BREAK IN PRECIP OVERNIGHT INTO TOMORROW MORNING...THE
NEXT LOW PRESSURE SYSTEM BEGINS AFFECTING THE AREA. AS PRECIP
DEVELOPS TOWARD MIDDAY TOMORROW...AGAIN THE FREEZING LINE WILL LIE
VERY CLOSE TO THE TERMINALS. TAFS REFLECT THE MORE OPTIMISTIC VIEW
THAT ORD/MDW REMAIN ON THE LIQUID SIDE AT LEAST THROUGH THE
AFTERNOON.
IF PRECIP REMAINS MOSTLY LIQUID THEN CIG/VSBY AND WIND TRENDS WILL
BE THE BIGGER ISSUES. AM NOT SEEING MUCH EITHER IN THE
OBSERVATIONS OR IN FCST GUIDANCE TO SUGGEST CIGS WILL IMPROVE
ABOVE IFR THROUGH THE AFTERNOON...AND SOME POSSIBILITY EXISTS FOR
LIFR. VSBYS ARE IN SLIGHTLY BETTER SHAPE.
STILL THINK WINDS WILL BACK TO NORTHWEST BY THIS EVENING THEN
FLUCTUATE BETWEEN NNW AND NNW TONIGHT AND TOMORROW AS THE LOW
PRESSURE SYSTEMS TO OUR SOUTH MIGRATE THROUGH THE AREA.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 22Z...
* MEDIUM CONFIDENCE IN TIMING OF WIND SHIFT FROM NE TO NNW BY MID-
EVENING.
* HIGH CONFIDENCE IN IFR CIGS REMAINING OVC006-008 AND VSBYS
GENERALLY 3-6SM IN BR/PATCHY -DZ NEXT SEVERAL HOURS.
* LOW CONFIDENCE ON CIG TRENDS OVERNIGHT.
* MEDIUM CONFIDENCE ON TIMING OF PRECIP TOMORROW BUT LOW
CONFIDENCE IN PRECIP TYPE TOMORROW AFTERNOON.
RATZER/LENNING
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...WINTRY MIX...IFR LIKELY.
SUNDAY...SNOW AND IFR.
MONDAY...CHANCE FOR SNOW...MVFR/IFR POSSIBLE.
TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE SNOW...MVFR POSSIBLE.
THURSDAY...MVFR BECOMING VFR.
MDB
&&
.MARINE...
218 PM...LOW PRESSURE OVER CENTRAL ILLINOIS WILL MOVE NORTHEAST
ACROSS THE EASTERN LAKES TONIGHT AS IT SLOWLY WEAKENS AS WEAK HIGH
PRESSURE OVER THE UPPER MIDWEST IS ABSORBED BY STRONGER HIGH
PRESSURE MOVING ACROSS SOUTHERN CANADA SATURDAY AND SATURDAY
NIGHT. THE GRADIENT WILL SLOWLY WEAKEN TONIGHT WITH SPEEDS IN THE
10-15 KT RANGE BY MORNING. NEW LOW PRESSURE WILL DEVELOP OVER
TEXAS TONIGHT AND MOVE NORTHEAST TO NORTHERN INDIANA BY SUNDAY
MORNING. AS THIS LOW APPROACHES THE LAKES REGION...IT WILL DEEPEN
AND THE GRADIENT WILL TIGHTEN BETWEEN THE STRONGER HIGH ACROSS
SOUTHERN CANADA. NORTHEAST WINDS WILL STEADILY INCREASE SATURDAY
EVENING WITH 30 KTS EXPECTED. DEPENDING ON THE EXACT STRENGTH AND
TRACK OF THIS LOW...ITS POSSIBLE THERE COULD BE A PERIOD OF LOW
END GALES BUT CONFIDENCE IS TOO LOW TO INCLUDE IN THIS FORECAST. A
TROUGH OF LOW PRESSURE WILL THEN LINGER ACROSS THE WESTERN LAKES
REGION SUNDAY NIGHT WITH NORTHERLY WINDS SHIFTING NORTHWESTERLY.
STRONG HIGH PRESSURE WILL BUILD ACROSS THE PLAINS SUNDAY AND
SUNDAY NIGHT AND THEN SHIFT EAST ACROSS THE LAKES REGION MONDAY
NIGHT AND TUESDAY. THERE IS A POTENTIAL FOR A PERIOD OF STRONG
WINDS AHEAD OF THE HIGH...IN THE MONDAY/MONDAY NIGHT TIME PERIOD.
BUT CONFIDENCE REGARDING SPECIFICS DURING THIS TIME PERIOD REMAIN
LOW. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 7 PM FRIDAY.
WINTER STORM WARNING...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-
ILZ011...6 PM SATURDAY TO 6 PM SUNDAY.
WINTER STORM WATCH...ILZ006-ILZ012...6 PM SATURDAY TO 6 PM
SUNDAY.
DENSE FOG ADVISORY...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 7 PM
FRIDAY.
FLOOD WATCH...ILZ033-ILZ039...NOON SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 7
PM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...NOON SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 PM FRIDAY.
&&
$$
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AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
337 PM CST FRI DEC 20 2013
.DISCUSSION...
337 PM CST...INCLUDING UPDATED WINTER STORM DISCUSSION BELOW...
TONIGHT THROUGH SATURDAY MORNING...
325 PM CST...
TONIGHT...THE FREEZING RAIN ADVISORY CONTINUES THROUGH 7 PM FOR
FAR NORTHERN IL AS LIGHT SHOWER ACTIVITY AND PATCHY DRIZZLE
CONTINUE TO OVERRIDE A SUBFREEZING BOUNDARY LAYER. THE GOES WATER
VAPOR LOOP SHOWS MODEST DRYING OVER THE AREA IN THE MID-
LEVELS...BUT JUST ENOUGH WEAK ASCENT APPEARS TO BE PRESENT WITHIN
THE LOW-LEVEL SATURATION TO KEEP TRIGGERING THESE LIGHT SHOWERS.
THE FREEZING DEMARCATION HELD STEADY MUCH OF TODAY FROM NEAR
MENDOTA NORTHEAST TO LAKE COUNTY IL. DO NOT SEE MUCH SHIFT WITH
THAT THROUGH EARLY THIS EVE. SO WITH IT BEING A BUSY HOLIDAY
TRAVEL TIME ADDED TO THE NORMAL FRIDAY COMMUTE...CERTAINLY LET THE
ADVISORY CONTINUE TO 7 PM. AS TEMPERATURES SLOWLY FALL BELOW
FREEZING SOUTH OF THE ADVISORY...UNTREATED WET ROADWAYS ARE LIKELY
TO EXPERIENCE SOME GLAZING TOO.
THE DENSE FOG ADVISORY FOR SOUTHERN AREAS SHOULD BE FINE ENDING AT 7
PM AS WINDS BEGIN TO INCREASE BEHIND THE BOUNDARY AND LOWER DEW
POINTS SEEP IN.
FORCING REMAINS WEAK THROUGH MUCH OF TONIGHT WITH LIMITED MOISTURE
TRANSPORT AND REALLY ANY TYPE OF MID-LEVEL WAVE/TRIGGER. SO WHILE
THERE IS A CHANCE FOR FREEZING DRIZZLE...ANY PRECIP SHOULD BE PATCHY
AT BEST AND LIGHT AFTER 7-8 PM.
SATURDAY MORNING...THE RAP AND OTHER HIGH RES GUIDANCE KEY IN ON
MOISTURE TRANSPORT AHEAD OF THE MAIN DEVELOPING SYSTEM /DESCRIBED
BELOW/ ADVANCING INTO THE SOUTHERN CWA IN THE PRE-DAWN HOURS AND
INTO SAT MORNING. THE CONVERGENCE AT THE NOSE OF THIS CREEPS INTO
THE SOUTHERN FORECAST AREA IN THE MORNING...WHERE FREEZING DRIZZLE
AND RAIN LOOK POSSIBLE...THOUGH THERE COULD BE QUITE A BIT OF RAIN
AND CONVECTIVE ACTIVITY ACROSS THE MID-MISSISSIPPI VALLEY THAT MAY
HALT THE FRONT EDGE ADVANCE OF THE PRECIP. HAVE CONTINUED MENTION
OF LIGHT FREEZING PRECIP SAT MORNING ACROSS AREAS MAINLY SOUTH OF
I-80.
MTF
DISCUSSION ON WINTER STORM.
WE HAVE UPGRADED PORTIONS OF THE WINTER STORM WATCH TO WARNING AND
CONTINUED THE WATCH FOR LAKE AND KANE COUNTIES.
THE VIGOROUS MID LEVEL FEATURE...CURRENTLY NOTED IN WATER VAPOR NEAR
THE BAJA OF CALIFORNIA EARLY THIS AFTERNOON IS FORECAST TO TAKE ON A
NEGATIVE TILT AS IT MOVES OUT ACROSS THE TEXAS PANHANDLE AROUND
MIDDAY ON SATURDAY. THIS FEATURE WILL LIFT QUICKLY
NORTH-NORTHEASTWARD ACROSS THE MID MISSISSIPPI VALLEY AND ACROSS
NORTHERN ILLINOIS SATURDAY NIGHT. MODEL GUIDANCE CONTINUES TO WAVER
AROUND A BIT ON THE ACTUAL TRACK OF THE 850 AND SURFACE LOWS.
THEREFORE...I HAVE TRENDED CLOSER TO THE ENSEMBLE MEANS...WHICH
TRACK THE 850 LOW RIGHT ACROSS NORTHEASTERN ILLINOIS LATE SATURDAY
NIGHT. THIS TRACK FAVORS NORTH CENTRAL AND FAR NORTHEASTERN ILLINOIS
FOR THE HEAVIEST SNOWFALL...ESPECIALLY SATURDAY NIGHT INTO EARLY
SUNDAY AS STRONG FRONTOGENESIS SETS UP WITHIN THE DEFORMATION
ZONE...JUST TO THE NORTH AND WEST OF THE 850 LOW TRACK. THIS WILL
LIKELY SUPPORT AN AREA OF HEAVY SNOWFALL ACROSS THESE AREAS...WITH
SNOW RATES LIKELY TO REACH OR EVEN EXCEED AN 1 INCH PER HOUR AT
TIMES...GIVEN THE GOOD COUPLING OF THE LARGE SCALE FORCING FOR
ASCENT FROM THE MID LEVEL WAVE AND THE GOOD FRONTOGENESIS. MID LEVEL
LAPSE RATES WILL ALSO SUPPORT GOOD SNOWFALL ACROSS THE WARNING
AREAS. I CHOSE TO LEAVE THE WATCH IN PLACE FOR LAKE AND KANE
COUNTIES. THESE AREAS MAY ALSO SEE 6+ INCHES OF SNOW...IN PORTIONS
OF THE COUNTIES...BUT DUE TO THE POTENTLY FOR SOME SLIGHT SHIFTS YET
IN THE TRACK OF THE SYSTEM...WITH A POTENTIAL FOR A FARTHER
NORTHWEST TRACK...I CHOOSE TO HOLD OFF.
THE OTHER CONCERN IS THE THREAT FOR FREEZING RAIN AND SLEET
ACCUMULATIONS...ESPECIALLY ACROSS SOUTHERN SECTIONS OF THE WARNING
AREA...AND PLACES TO THE SOUTH. TEMPERATURES ARE EXPECTED TO REMAIN
RIGHT AROUND THE FREEZING POINT...SO IT APPEARS THAT ICING AMOUNTS
MAY BE LIMITED SOME...ESPECIALLY NEAR CHICAGO. WITH THAT BEING
SAID...I STILL THINK THERE IS A DECENT POTENTIAL TO HAVE AN AREA OF
SOME ICE ACCUMULATIONS...OF 0.1 TO 0.2 INCHES...PRIMARILY NORTH OF
I-80 UP TO AROUND THE I-88 CORRIDOR. CLOSER TO THE LAKE AND THE
CITY ICE AMOUNTS MAY BE LESS DUE TO THE FLOW OFF THE LAKE POSSIBLY
RESULTING IN TEMPS JUST ABOVE FREEZING. IT APPEARS THE MAIN ICING
THREAT WILL NOT OCCUR UNTIL TOMORROW AFTERNOON AND INTO THE
EVENING. THEREFORE...WE HAVE SOME TIME TO BETTER IRON OUT THE
AREAS MOST SUSCEPTIBLE TO ICING. WE WILL HIGHLIGHT THIS THREAT IN
AN SPS.
IT ALSO APPEARS THE HEAVY RAIN THREAT WILL MAINLY BE ACROSS MY
SOUTHEASTERN COUNTIES...SO NO CHANGES TO THE GOING FLOOD WATCH.
STRONG MOISTURE CONVERGENCE AND ANOMALOUSLY HIGH PWATS WILL LIKELY
PRODUCE AMOUNTS IN EXCESS OF AN INCH OR SO ACROSS THESE AREAS...AND
WITH ALL OF THIS BECOMING RUNOFF...RAPID RISES ON AREA STREAMS ARE
EXPECTED.
THE SNOW THREAT FOR AREAS SOUTH OF THE CURRENT WARNING AREA APPEAR
TO SOMEWHAT LIMITED...WITH A SHARP GRADIENT IN THE SNOW
ACCUMULATIONS EXPECTED. AN IMPRESSIVE DRY SLOT WILL PUNCH IN ACROSS
THE AREA LATE SATURDAY NIGHT INTO SUNDAY...LIKELY RESULT IN ONLY
LIGHT SNOW OR EVEN FZ DRIZZLE GIVEN THE LOSE OF ICE IN THE CLOUDS.
TOTAL SNOW AMOUNTS LOOK TO DROP TO UNDER AN INCH BY THE TIME YOU GET
CLOSE TO CHICAGO AND INTERSTATE 80.
MUCH COLDER AIR SPILLS IN ACROSS THE AREA SUNDAY NIGHT...WITH LIGHT
PRECIP CONTINUING IN ASSOCIATION WILL ANOTHER UPPER LEVEL
DISTURBANCE. TEMPERATURES WILL LIKELY DROP INTO THE SINGLE DIGITS
IN MOST AREAS SUNDAY NIGHT. THUS...ANY STANDING WATER
REMAINING...WITH LIKELY QUICKLY FREEZE IN PLACE ACROSS THE AREA.
KJB
EXTENDED FORECAST PERIOD /MONDAY MORNING THROUGH FRIDAY INCLUDING
THE CHRISTMAS HOLIDAY...
300 PM CST...
THE SENSIBLE WEATHER WILL QUIET CONSIDERABLY WITH THE MAIN FORECAST
CONCERNS FOCUSING ON TEMPERATURES AND THE CHANCE FOR SOME LIGHT
SNOW ON CHRISTMAS EVE AND EARLY CHRISTMAS DAY. THE GENERAL TREND
FOR THE EXTENDED FORECAST PERIOD WILL BE FOR MUCH BELOW NORMAL
TEMPERATURES WITH THE ONLY CHANCE FOR SOME LIGHT SNOW ON CHRISTMAS
EVE INTO CHRISTMAS DAY.
A HIGH AMPLITUDE LONGWAVE TROUGH IS EXPECTED TO CARVE OUT OVER THE
CNTRL CONUS WITH THE TROUGH AXIS EXTENDING FROM HUDSON BAY THROUGH
CENTRAL TEXAS. INITIALLY ON MONDAY...THE LOCAL AREA WILL SEE THE
TROUGH AXIS MOVING THROUGH THE AREA TRANSITIONING THE REGION FROM
RELATIVE WARM ADVECTION TO STRONG COLD ADVECTION. TEMPERATURES WILL
DROP OFF QUICKLY BY MONDAY MORNING...WITH LOWS EXPECTED TO DROP ONTO
THE SINGLE DIGITS WEST OF THE FOX VALLEY AND I-55 CORRIDOR. LOWS
OVER THE EASTERN PORTION OF THE FORECAST AREA SHOULD HANG IN THE
MIDDLE TO UPPER TEENS. AS THE LONGWAVE TROUGH CONTINUES TO THE ERN
CONUS MONDAY AND MONDAY NIGHT...WEAK UPPER RIDGING WILL BUILD ACROSS
THE UPPER MISSISSIPPI VALLEY...WITH THE AMPLITUDE OF THE UPPER LEVEL
PATTERN CONTINUING TO AMPLIFY. WITH DEEP LAYER FLOW REMAINING ON
THE NWLY FLOW SIDE OF THE UPPER RIDGE...TEMPERATURES WILL CONTINUE
TO DROP WITH LOWS TUESDAY MORNING BELOW ZERO OVER MUCH OF THE CWA...
GENERALLY WEST OF A LINE FROM WAUKEGAN TO PONTIAC...WITH THE
COLDEST AIR OVER THE ROCKFORD AREA WHERE TEMPS SHOULD BOTTOM OUT AT
-5F TO -10F. WIND CHILLS WILL BE A CONCERN AS WELL. WITH WINDS OF
5-10 KT LIKELY...WIND CHILLS WILL APPROACH THE -20F WIND CHILL
ADVISORY CRITERIA WEST OF THE FOX VALLEY AND I-55 CORRIDOR. BY
TUESDAY NIGHT...THE LONGER RANGE MODELS ARE ADVERTISING A PAIR OF
NORTHERN STREAM SHORTWAVES TRACKING ACROSS THE NRN PLAINS. THE
NRN-MOST WAVE...WHICH IS ALSO THE STRONGER OF THE PAIR...SHOULD
TRACK TO THE EAST...ACROSS THE UPPER GREAT LAKES WHILE THE MORE
SOUTHERLY...WEAKER WAVE DROPS THROUGH THE NRN PLAINS TO THE MIDDLE
MISSISSIPPI VALLEY. THIS THERE IS SOME DISCREPANCY AMONG THE LONGER
RANGE GUIDANCE ON THE SPEED OF PROGRESSION OF THIS WAVE...BUT THE
GENERAL CONSENSUS IS THAT THE WAVE WILL CROSS THE MIDDLE MISSISSIPPI
VALLEY...TRACKING OVER THE IL/WI BOARDER. FOLLOWING A PERIOD OF
STRONG COLD/DRY ADVECTION...THERE WILL BE LITTLE IN SITU MOISTURE
FOR THE SYSTEM TO WORK WITH AND WILL LARGELY HAVE TO RELY ON
DYNAMICS TO PRODUCE ANY PCPN. AT THIS POINT...ANTICIPATE THAT UPPER
DYNAMICS SHOULD BE STRONG ENOUGH TO PRODUCE AT LEAST SOME LIGHT SNOW
FOR LATE CHRISTMAS EVE INTO EARLY CHRISTMAS DAY. GIVEN THE LACK OF
DEEP LAYER MOISTURE OR ANY SIGNIFICANT LOW LEVEL MOISTURE TRANSPORT
AS FLOW THROUGH THE LOWER LEVELS SHOULD BE MORE WESTERLY AND UNABLE
TO TAP ANY GULF MOISTURE...ANY ACCUMULATIONS WILL LIKELY BE LIGHT.
A BRIEF PERIOD OF MORE WLY OR AT LEAST BROAD...FLAT TROUGHING SHOULD
COVER THE MIDWEST ON WEDNESDAY...ALLOWING FOR SOME MODERATION OF
TEMPERATURES ON WEDNESDAY AND THURSDAY...WITH HIGHS IN THE UPPER 20S
TO LOWER 30S ON WEDNESDAY AND UPPER TEENS TO MIDDLE 20S ON THURSDAY.
A REINFORCING SHOT OF COLD AIR ASSOCIATED WITH A STRONG NORTHERN
STREAM SHORTWAVE DIGGING INTO THE UPPER MISSISSIPPI VALLEY AND
SOUTHERN GREAT LAKES WILL BRING SUB-ZERO TEMPERATURES BACK TO MUCH
OF THE CWA FOR FRIDAY MORNING.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* ONGOING IFR CIG/VSBY TRENDS.
* PRECIPITATION ENDING TIME AND POSSIBLE LIGHT FREEZING RAIN TODAY.
* WINDS BACKING NORTH THEN NORTHWEST.
LENNING
//DISCUSSION...UPDATED 18Z...
SO FAR AT MDW/ORD/GYY THE TEMPERATURES HAVE REMAINED ENOUGH ABOVE
FREEZING THAT ICE AT THE SFC HAS NOT BEEN A PROBLEM. DPA HAS BEEN
RIGHT ON THE LINE BUT STILL ABOVE FREEZING...WHILE RFD HAS BEEN
HAVING CONSIDERABLE ICE PROBLEMS. RADAR TRENDS SUGGEST ORD/MDW
PRECIP MAY END A BIT SOONER THAN PREVIOUSLY EXPECTED THIS
AFTERNOON...AND FCST SOUNDINGS SUGGEST INCOMING COLD AIR WOULD
PRODUCE ONLY A BRIEF PERIOD OF LIGHT FREEZING DRIZZLE AT WORST.
AFTER A BREAK IN PRECIP OVERNIGHT INTO TOMORROW MORNING...THE
NEXT LOW PRESSURE SYSTEM BEGINS AFFECTING THE AREA. AS PRECIP
DEVELOPS TOWARD MIDDAY TOMORROW...AGAIN THE FREEZING LINE WILL LIE
VERY CLOSE TO THE TERMINALS. TAFS REFLECT THE MORE OPTIMISTIC VIEW
THAT ORD/MDW REMAIN ON THE LIQUID SIDE AT LEAST THROUGH THE
AFTERNOON.
IF PRECIP REMAINS MOSTLY LIQUID THEN CIG/VSBY AND WIND TRENDS WILL
BE THE BIGGER ISSUES. AM NOT SEEING MUCH EITHER IN THE
OBSERVATIONS OR IN FCST GUIDANCE TO SUGGEST CIGS WILL IMPROVE
ABOVE IFR THROUGH THE AFTERNOON...AND SOME POSSIBILITY EXISTS FOR
LIFR. VSBYS ARE IN SLIGHTLY BETTER SHAPE.
STILL THINK WINDS WILL BACK TO NORTHWEST BY THIS EVENING THEN
FLUCTUATE BETWEEN NNW AND NNW TONIGHT AND TOMORROW AS THE LOW
PRESSURE SYSTEMS TO OUR SOUTH MIGRATE THROUGH THE AREA.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* LOW CONFIDENCE ABOUT EXACT CIG/VSBY TRENDS THIS AFTERNOON BUT
FAVOR MOSTLY IFR WITH OCCASIONAL LIFR CIGS AND VFR VSBYS.
* WINDS HAVE BEEN STEADY NNE BUT STILL MEDIUM TO HIGH CONFIDENCE
THAT TREND WILL VERY SOON BE MORE NORTHERLY THIS AFTERNOON.
* LOW CONFIDENCE ON HOW LOW CIGS GO OVERNIGHT.
* MEDIUM CONFIDENCE ON TIMING OF PRECIP TOMORROW BUT LOW
CONFIDENCE IN PRECIP TYPE TOMORROW AFTERNOON.
LENNING
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...WINTRY MIX...IFR LIKELY.
SUNDAY...SNOW AND IFR.
MONDAY...CHANCE FOR SNOW...MVFR/IFR POSSIBLE.
TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE SNOW...MVFR POSSIBLE.
THURSDAY...MVFR BECOMING VFR.
MDB
&&
.MARINE...
218 PM...LOW PRESSURE OVER CENTRAL ILLINOIS WILL MOVE NORTHEAST
ACROSS THE EASTERN LAKES TONIGHT AS IT SLOWLY WEAKENS AS WEAK HIGH
PRESSURE OVER THE UPPER MIDWEST IS ABSORBED BY STRONGER HIGH
PRESSURE MOVING ACROSS SOUTHERN CANADA SATURDAY AND SATURDAY
NIGHT. THE GRADIENT WILL SLOWLY WEAKEN TONIGHT WITH SPEEDS IN THE
10-15 KT RANGE BY MORNING. NEW LOW PRESSURE WILL DEVELOP OVER
TEXAS TONIGHT AND MOVE NORTHEAST TO NORTHERN INDIANA BY SUNDAY
MORNING. AS THIS LOW APPROACHES THE LAKES REGION...IT WILL DEEPEN
AND THE GRADIENT WILL TIGHTEN BETWEEN THE STRONGER HIGH ACROSS
SOUTHERN CANADA. NORTHEAST WINDS WILL STEADILY INCREASE SATURDAY
EVENING WITH 30 KTS EXPECTED. DEPENDING ON THE EXACT STRENGTH AND
TRACK OF THIS LOW...ITS POSSIBLE THERE COULD BE A PERIOD OF LOW
END GALES BUT CONFIDENCE IS TOO LOW TO INCLUDE IN THIS FORECAST. A
TROUGH OF LOW PRESSURE WILL THEN LINGER ACROSS THE WESTERN LAKES
REGION SUNDAY NIGHT WITH NORTHERLY WINDS SHIFTING NORTHWESTERLY.
STRONG HIGH PRESSURE WILL BUILD ACROSS THE PLAINS SUNDAY AND
SUNDAY NIGHT AND THEN SHIFT EAST ACROSS THE LAKES REGION MONDAY
NIGHT AND TUESDAY. THERE IS A POTENTIAL FOR A PERIOD OF STRONG
WINDS AHEAD OF THE HIGH...IN THE MONDAY/MONDAY NIGHT TIME PERIOD.
BUT CONFIDENCE REGARDING SPECIFICS DURING THIS TIME PERIOD REMAIN
LOW. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 7 PM FRIDAY.
WINTER STORM WARNING...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-
ILZ011...6 PM SATURDAY TO 6 PM SUNDAY.
WINTER STORM WATCH...ILZ006-ILZ012...6 PM SATURDAY TO 6 PM
SUNDAY.
DENSE FOG ADVISORY...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 7 PM
FRIDAY.
FLOOD WATCH...ILZ033-ILZ039...NOON SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 7
PM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...NOON SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 PM FRIDAY.
&&
$$
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
330 PM CST FRI DEC 20 2013
.DISCUSSION...
303 PM CST...
DISCUSSION ON WINTER STORM WILL BE ISSUED SHORTLY.
HEADLINE NOTES FOR STORM...
A WINTER STORM WARNING WILL BE ISSUED FOR:
WINNEBAGO...LEE...OGLE...BOONE...MCHENRY AND DEKALB COUNTIES.
THE WINTER STORM WATCH WILL REMAIN IN EFFECT FOR KANE AND LAKE
COUNTIES IN ILLINOIS.
A FLOOD WATCH REMAINS IN EFFECT FOR:
FORD...IROQUOIS...NEWTON...JASPER AND BENTON COUNTIES.
RC
TONIGHT THROUGH SATURDAY MORNING...
325 PM CST...
TONIGHT...THE FREEZING RAIN ADVISORY CONTINUES THROUGH 7 PM FOR
FAR NORTHERN IL AS LIGHT SHOWER ACTIVITY AND PATCHY DRIZZLE
CONTINUE TO OVERRIDE A SUBFREEZING BOUNDARY LAYER. THE GOES WATER
VAPOR LOOP SHOWS MODEST DRYING OVER THE AREA IN THE MID-
LEVELS...BUT JUST ENOUGH WEAK ASCENT APPEARS TO BE PRESENT WITHIN
THE LOW-LEVEL SATURATION TO KEEP TRIGGERING THESE LIGHT SHOWERS.
THE FREEZING DEMARCATION HELD STEADY MUCH OF TODAY FROM NEAR
MENDOTA NORTHEAST TO LAKE COUNTY IL. DO NOT SEE MUCH SHIFT WITH
THAT THROUGH EARLY THIS EVE. SO WITH IT BEING A BUSY HOLIDAY
TRAVEL TIME ADDED TO THE NORMAL FRIDAY COMMUTE...CERTAINLY LET THE
ADVISORY CONTINUE TO 7 PM. AS TEMPERATURES SLOWLY FALL BELOW
FREEZING SOUTH OF THE ADVISORY...UNTREATED WET ROADWAYS ARE LIKELY
TO EXPERIENCE SOME GLAZING TOO.
THE DENSE FOG ADVISORY FOR SOUTHERN AREAS SHOULD BE FINE ENDING AT 7
PM AS WINDS BEGIN TO INCREASE BEHIND THE BOUNDARY AND LOWER DEW
POINTS SEEP IN.
FORCING REMAINS WEAK THROUGH MUCH OF TONIGHT WITH LIMITED MOISTURE
TRANSPORT AND REALLY ANY TYPE OF MID-LEVEL WAVE/TRIGGER. SO WHILE
THERE IS A CHANCE FOR FREEZING DRIZZLE...ANY PRECIP SHOULD BE PATCHY
AT BEST AND LIGHT AFTER 7-8 PM.
SATURDAY MORNING...THE RAP AND OTHER HIGH RES GUIDANCE KEY IN ON
MOISTURE TRANSPORT AHEAD OF THE MAIN DEVELOPING SYSTEM /DESCRIBED
BELOW/ ADVANCING INTO THE SOUTHERN CWA IN THE PRE-DAWN HOURS AND
INTO SAT MORNING. THE CONVERGENCE AT THE NOSE OF THIS CREEPS INTO
THE SOUTHERN FORECAST AREA IN THE MORNING...WHERE FREEZING DRIZZLE
AND RAIN LOOK POSSIBLE...THOUGH THERE COULD BE QUITE A BIT OF RAIN
AND CONVECTIVE ACTIVITY ACROSS THE MID-MISSISSIPPI VALLEY THAT MAY
HALT THE FRONT EDGE ADVANCE OF THE PRECIP. HAVE CONTINUED MENTION
OF LIGHT FREEZING PRECIP SAT MORNING ACROSS AREAS MAINLY SOUTH OF
I-80.
MTF
EXTENDED FORECAST PERIOD /MONDAY MORNING THROUGH FRIDAY INCLUDING
THE CHRISTMAS HOLIDAY...
300 PM CST...
THE SENSIBLE WEATHER WILL QUIET CONSIDERABLY WITH THE MAIN FORECAST
CONCERNS FOCUSING ON TEMPERATURES AND THE CHANCE FOR SOME LIGHT
SNOW ON CHRISTMAS EVE AND EARLY CHRISTMAS DAY. THE GENERAL TREND
FOR THE EXTENDED FORECAST PERIOD WILL BE FOR MUCH BELOW NORMAL
TEMPERATURES WITH THE ONLY CHANCE FOR SOME LIGHT SNOW ON CHRISTMAS
EVE INTO CHRISTMAS DAY.
A HIGH AMPLITUDE LONGWAVE TROUGH IS EXPECTED TO CARVE OUT OVER THE
CNTRL CONUS WITH THE TROUGH AXIS EXTENDING FROM HUDSON BAY THROUGH
CENTRAL TEXAS. INITIALLY ON MONDAY...THE LOCAL AREA WILL SEE THE
TROUGH AXIS MOVING THROUGH THE AREA TRANSITIONING THE REGION FROM
RELATIVE WARM ADVECTION TO STRONG COLD ADVECTION. TEMPERATURES WILL
DROP OFF QUICKLY BY MONDAY MORNING...WITH LOWS EXPECTED TO DROP ONTO
THE SINGLE DIGITS WEST OF THE FOX VALLEY AND I-55 CORRIDOR. LOWS
OVER THE EASTERN PORTION OF THE FORECAST AREA SHOULD HANG IN THE
MIDDLE TO UPPER TEENS. AS THE LONGWAVE TROUGH CONTINUES TO THE ERN
CONUS MONDAY AND MONDAY NIGHT...WEAK UPPER RIDGING WILL BUILD ACROSS
THE UPPER MISSISSIPPI VALLEY...WITH THE AMPLITUDE OF THE UPPER LEVEL
PATTERN CONTINUING TO AMPLIFY. WITH DEEP LAYER FLOW REMAINING ON
THE NWLY FLOW SIDE OF THE UPPER RIDGE...TEMPERATURES WILL CONTINUE
TO DROP WITH LOWS TUESDAY MORNING BELOW ZERO OVER MUCH OF THE CWA...
GENERALLY WEST OF A LINE FROM WAUKEGAN TO PONTIAC...WITH THE
COLDEST AIR OVER THE ROCKFORD AREA WHERE TEMPS SHOULD BOTTOM OUT AT
-5F TO -10F. WIND CHILLS WILL BE A CONCERN AS WELL. WITH WINDS OF
5-10 KT LIKELY...WIND CHILLS WILL APPROACH THE -20F WIND CHILL
ADVISORY CRITERIA WEST OF THE FOX VALLEY AND I-55 CORRIDOR. BY
TUESDAY NIGHT...THE LONGER RANGE MODELS ARE ADVERTISING A PAIR OF
NORTHERN STREAM SHORTWAVES TRACKING ACROSS THE NRN PLAINS. THE
NRN-MOST WAVE...WHICH IS ALSO THE STRONGER OF THE PAIR...SHOULD
TRACK TO THE EAST...ACROSS THE UPPER GREAT LAKES WHILE THE MORE
SOUTHERLY...WEAKER WAVE DROPS THROUGH THE NRN PLAINS TO THE MIDDLE
MISSISSIPPI VALLEY. THIS THERE IS SOME DISCREPANCY AMONG THE LONGER
RANGE GUIDANCE ON THE SPEED OF PROGRESSION OF THIS WAVE...BUT THE
GENERAL CONSENSUS IS THAT THE WAVE WILL CROSS THE MIDDLE MISSISSIPPI
VALLEY...TRACKING OVER THE IL/WI BOARDER. FOLLOWING A PERIOD OF
STRONG COLD/DRY ADVECTION...THERE WILL BE LITTLE IN SITU MOISTURE
FOR THE SYSTEM TO WORK WITH AND WILL LARGELY HAVE TO RELY ON
DYNAMICS TO PRODUCE ANY PCPN. AT THIS POINT...ANTICIPATE THAT UPPER
DYNAMICS SHOULD BE STRONG ENOUGH TO PRODUCE AT LEAST SOME LIGHT SNOW
FOR LATE CHRISTMAS EVE INTO EARLY CHRISTMAS DAY. GIVEN THE LACK OF
DEEP LAYER MOISTURE OR ANY SIGNIFICANT LOW LEVEL MOISTURE TRANSPORT
AS FLOW THROUGH THE LOWER LEVELS SHOULD BE MORE WESTERLY AND UNABLE
TO TAP ANY GULF MOISTURE...ANY ACCUMULATIONS WILL LIKELY BE LIGHT.
A BRIEF PERIOD OF MORE WLY OR AT LEAST BROAD...FLAT TROUGHING SHOULD
COVER THE MIDWEST ON WEDNESDAY...ALLOWING FOR SOME MODERATION OF
TEMPERATURES ON WEDNESDAY AND THURSDAY...WITH HIGHS IN THE UPPER 20S
TO LOWER 30S ON WEDNESDAY AND UPPER TEENS TO MIDDLE 20S ON THURSDAY.
A REINFORCING SHOT OF COLD AIR ASSOCIATED WITH A STRONG NORTHERN
STREAM SHORTWAVE DIGGING INTO THE UPPER MISSISSIPPI VALLEY AND
SOUTHERN GREAT LAKES WILL BRING SUB-ZERO TEMPERATURES BACK TO MUCH
OF THE CWA FOR FRIDAY MORNING.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* ONGOING IFR CIG/VSBY TRENDS.
* PRECIPITATION ENDING TIME AND POSSIBLE LIGHT FREEZING RAIN TODAY.
* WINDS BACKING NORTH THEN NORTHWEST.
LENNING
//DISCUSSION...UPDATED 18Z...
SO FAR AT MDW/ORD/GYY THE TEMPERATURES HAVE REMAINED ENOUGH ABOVE
FREEZING THAT ICE AT THE SFC HAS NOT BEEN A PROBLEM. DPA HAS BEEN
RIGHT ON THE LINE BUT STILL ABOVE FREEZING...WHILE RFD HAS BEEN
HAVING CONSIDERABLE ICE PROBLEMS. RADAR TRENDS SUGGEST ORD/MDW
PRECIP MAY END A BIT SOONER THAN PREVIOUSLY EXPECTED THIS
AFTERNOON...AND FCST SOUNDINGS SUGGEST INCOMING COLD AIR WOULD
PRODUCE ONLY A BRIEF PERIOD OF LIGHT FREEZING DRIZZLE AT WORST.
AFTER A BREAK IN PRECIP OVERNIGHT INTO TOMORROW MORNING...THE
NEXT LOW PRESSURE SYSTEM BEGINS AFFECTING THE AREA. AS PRECIP
DEVELOPS TOWARD MIDDAY TOMORROW...AGAIN THE FREEZING LINE WILL LIE
VERY CLOSE TO THE TERMINALS. TAFS REFLECT THE MORE OPTIMISTIC VIEW
THAT ORD/MDW REMAIN ON THE LIQUID SIDE AT LEAST THROUGH THE
AFTERNOON.
IF PRECIP REMAINS MOSTLY LIQUID THEN CIG/VSBY AND WIND TRENDS WILL
BE THE BIGGER ISSUES. AM NOT SEEING MUCH EITHER IN THE
OBSERVATIONS OR IN FCST GUIDANCE TO SUGGEST CIGS WILL IMPROVE
ABOVE IFR THROUGH THE AFTERNOON...AND SOME POSSIBILITY EXISTS FOR
LIFR. VSBYS ARE IN SLIGHTLY BETTER SHAPE.
STILL THINK WINDS WILL BACK TO NORTHWEST BY THIS EVENING THEN
FLUCTUATE BETWEEN NNW AND NNW TONIGHT AND TOMORROW AS THE LOW
PRESSURE SYSTEMS TO OUR SOUTH MIGRATE THROUGH THE AREA.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* LOW CONFIDENCE ABOUT EXACT CIG/VSBY TRENDS THIS AFTERNOON BUT
FAVOR MOSTLY IFR WITH OCCASIONAL LIFR CIGS AND VFR VSBYS.
* WINDS HAVE BEEN STEADY NNE BUT STILL MEDIUM TO HIGH CONFIDENCE
THAT TREND WILL VERY SOON BE MORE NORTHERLY THIS AFTERNOON.
* LOW CONFIDENCE ON HOW LOW CIGS GO OVERNIGHT.
* MEDIUM CONFIDENCE ON TIMING OF PRECIP TOMORROW BUT LOW
CONFIDENCE IN PRECIP TYPE TOMORROW AFTERNOON.
LENNING
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...WINTRY MIX...IFR LIKELY.
SUNDAY...SNOW AND IFR.
MONDAY...CHANCE FOR SNOW...MVFR/IFR POSSIBLE.
TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE SNOW...MVFR POSSIBLE.
THURSDAY...MVFR BECOMING VFR.
MDB
&&
.MARINE...
218 PM...LOW PRESSURE OVER CENTRAL ILLINOIS WILL MOVE NORTHEAST
ACROSS THE EASTERN LAKES TONIGHT AS IT SLOWLY WEAKENS AS WEAK HIGH
PRESSURE OVER THE UPPER MIDWEST IS ABSORBED BY STRONGER HIGH
PRESSURE MOVING ACROSS SOUTHERN CANADA SATURDAY AND SATURDAY
NIGHT. THE GRADIENT WILL SLOWLY WEAKEN TONIGHT WITH SPEEDS IN THE
10-15 KT RANGE BY MORNING. NEW LOW PRESSURE WILL DEVELOP OVER
TEXAS TONIGHT AND MOVE NORTHEAST TO NORTHERN INDIANA BY SUNDAY
MORNING. AS THIS LOW APPROACHES THE LAKES REGION...IT WILL DEEPEN
AND THE GRADIENT WILL TIGHTEN BETWEEN THE STRONGER HIGH ACROSS
SOUTHERN CANADA. NORTHEAST WINDS WILL STEADILY INCREASE SATURDAY
EVENING WITH 30 KTS EXPECTED. DEPENDING ON THE EXACT STRENGTH AND
TRACK OF THIS LOW...ITS POSSIBLE THERE COULD BE A PERIOD OF LOW
END GALES BUT CONFIDENCE IS TOO LOW TO INCLUDE IN THIS FORECAST. A
TROUGH OF LOW PRESSURE WILL THEN LINGER ACROSS THE WESTERN LAKES
REGION SUNDAY NIGHT WITH NORTHERLY WINDS SHIFTING NORTHWESTERLY.
STRONG HIGH PRESSURE WILL BUILD ACROSS THE PLAINS SUNDAY AND
SUNDAY NIGHT AND THEN SHIFT EAST ACROSS THE LAKES REGION MONDAY
NIGHT AND TUESDAY. THERE IS A POTENTIAL FOR A PERIOD OF STRONG
WINDS AHEAD OF THE HIGH...IN THE MONDAY/MONDAY NIGHT TIME PERIOD.
BUT CONFIDENCE REGARDING SPECIFICS DURING THIS TIME PERIOD REMAIN
LOW. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 7 PM FRIDAY.
WINTER STORM WARNING...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-
ILZ011...6 PM SATURDAY TO 6 PM SUNDAY.
WINTER STORM WATCH...ILZ006-ILZ012...6 PM SATURDAY TO 6 PM
SUNDAY.
DENSE FOG ADVISORY...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 7 PM
FRIDAY.
FLOOD WATCH...ILZ033-ILZ039...NOON SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 7
PM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...NOON SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 9 PM FRIDAY.
&&
$$
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
304 PM CST FRI DEC 20 2013
.DISCUSSION...
303 PM CST...
DISCUSSION ON WINTER STORM WILL BE ISSUED SHORTLY.
HEADLINE NOTES FOR STORM...
A WINTER STORM WARNING WILL BE ISSUED FOR:
WINNEBAGO...LEE...OGLE...BOONE...MCHENRY AND DEKALB COUNTIES.
THE WINTER STORM WATCH WILL REMAIN IN EFFECT FOR KANE AND LAKE
COUNTIES IN ILLINOIS.
A FLOOD WATCH REMAINS IN EFFECT FOR:
FORD...IROQUOIS...NEWTON...JASPER AND BENTON COUNTIES.
RC
PREVIOUS DISCUSSIONS...1155 AM CST
WATER VAPOR SHOWS SOME RELATIVE DRYING MOVING OVER THE AREA IN
THIS DEEP SOUTHWEST MOIST PLUME AND THAT ALONG WITH JUST LESS
ASCENT IS LIKELY RESPONSIBLE FOR THE DIMINISHING SHOWER COVERAGE.
THIS TREND SHOULD SLOWLY CONTINUE ALTHOUGH PROFILES REMAIN AT
LEAST SUPPORTIVE OF DRIZZLE THROUGH THE AFTERNOON. THE FREEZING
LINE HAS MAINTAINED ITS GROUND THROUGH THE PAST SEVERAL HOURS AND
EXPECT VERY LITTLE CHANGE WITH THAT THROUGH MID AFTERNOON...HENCE
THE PRESERVING OF THE FREEZING RAIN ADVISORY.
WHILE VISIBILITY OBSERVATIONS OF DENSE FOG ARE FAR MORE SPOTTY IN
THE SOUTHERN CWA THAN THEY WERE THIS MORNING...THE SHOWERS HAVE
LIKELY BEEN PARTLY RESPONSIBLE FOR THE SOMEWHAT CHAOTIC VISIBILITY
FIELD. WITH CONTINUED MOISTURE POOLING FROM ADVECTION AND
SNOW SUBLIMATION...ALONG WITH LIGHT WINDS IMMEDIATELY ALONG THE
BOUNDARY...WILL CONTINUE THAT ADVISORY AS IS UNTIL 3 PM.
AS THE SURFACE LOW MOVES INTO NORTH CENTRAL IN BY 4-5 PM...THE
SOMEWHAT DEEPER NORTHERLY FLOW IN THE LOW-LEVELS...ALONG WITH
NIGHTFALL SHOULD ADVANCE THE FREEZING LINE SOUTHWARD. FORCING FOR
PRECIP INTO TONIGHT LOOKS TO BE MAINLY DRIZZLE AS ANY APPRECIABLE
MOISTURE TRANSPORT SHIFTS SOUTHEAST AND THERE IS A LACK OF ANY
REAL SHORT WAVE IMPULSES PRESENTLY FORECAST. SOUNDINGS MARGINALLY
SUPPORTIVE OF DRIZZLE ARE MAINLY INDICATED IN THE SOUTHERN
FORECAST AREA. OVERALL NOT FEELING THAT A HEADLINE WILL BE
NEEDED...AND MORE SO HANDLED WITH AN SPS. IT IS POSSIBLE THE
CURRENT FREEZING RAIN ADVISORY IS EXTENDED UNTIL 6-7 PM TO ACCOUNT
FOR THE LATE AFTERNOON RUSH IF RADAR TRENDS AND REPORTS CONTINUE
TO INDICATE SHOWERS AND DRIZZLE OVER THE SUBFREEZING BOUNDARY
LAYER AS WE NEAR 3 PM.
MTF
355 AM CST...
SEVERAL ISSUES ONGOING THIS MORNING AS WELL THROUGH THE
WEEKEND...WITH DENSE FOG AND FREEZING RAIN ISSUES THIS MORNING
WITH THE FREEZING RAIN NOW LINGERING INTO THE AFTERNOON AND
POSSIBLY TONIGHT...CONTINUED FLOODING CONCERNS...AND LASTLY
POTENTIAL SNOWFALL WHICH THE AXIS OF HEAVIEST SNOW STILL APPEARS
TO BE ACROSS THE NORTH AND NORTHWEST AREAS OF THE CWA.
ADDRESSING THE MORE IMPORTANT ISSUES IN THE NEAR TERM...LIGHT
FREEZING RAIN OR FREEZING DRIZZLE CONTINUES ACROSS THE ADVISORY
AREA THIS MORNING...WITH LIGHT RAIN OR DRIZZLE ONGOING FOR THE
REMAINDER OF THE CWA. BROAD SOUTHWESTERLY FLOW ALOFT CONTINUES TO
USHER SEVERAL WAVES OF ENERGY...WITH ELONGATED TROUGH OF LOW
PRESSURE EXTENDING FROM THE CENTRAL PLAINS UP THROUGH SOUTHERN
GREAT LAKES. AS THESE WAVES OF ENERGY/SPEED MAXES LIFT NORTHEAST
ACROSS THE REGION THIS MORNING...EXPECT THIS TROUGH OF LOW
PRESSURE TO LIFT EAST NORTHEAST TO CENTRAL ILLINOIS AND NORTHWEST
INDIANA THROUGH THE EARLY AFTERNOON. PRESENT LOW/MID LEVEL
CONVERGENCE WILL CONTINUE TO BE A PERSISTENT THROUGH THIS
PERIOD...WITH CURRENT UPSTREAM WAVE TO AID IN TIGHTENING LOW/MID
LEVEL BAROCLINIC ZONE. THIS WILL ENHANCE FRONTOGENETIC FORCING
ACROSS THE ADVISORY AREA...ALL AIDING IN CONTINUED PRECIP
DEVELOPMENT AT LEAST THROUGH EARLY AFTERNOON FOR THE ENTIRE CWA.
HAVE INCREASED POPS THIS MORNING AND EARLY AFTERNOON...BUT WONDER
IF AFTERNOON POPS WILL NEED TO BE RAISED EVEN FURTHER WITH SHORT
TERM GUIDANCE HINTING AT CONTINUED TO DEVELOPMENT EVEN INTO THE
LATE AFTERNOON. ALTHOUGH CURRENT ASSOCIATED BOUNDARY DRAPED ACROSS
EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA DID MAKE SOME
NORTHWARD PROGRESSION EARLY THIS MORNING...FEEL THAT THIS
NORTHWARD MOVEMENT HAS ENDED AND WILL REMAIN SITUATED UNTIL
DROPPING SOUTH/SOUTHEAST OF THE CWA THIS AFTERNOON. GUIDANCE
HINTING AT SOME WEAK CAA TO BEGIN OCCURRING OVER THE NEXT SEVERAL
HOURS AND WITH LATEST RAP ANALYSIS ALREADY INDICATING THIS ACROSS
WESTERN ILLINOIS...FEEL PRETTY CONFIDENT WITH THIS TREND. THIS
WILL HELP TEMPS IN THE ADVISORY AREA TO HOVER JUST BELOW OR AT THE
FREEZING MARK THROUGH MOST OF TODAY. WITH THIS CONTINUED PRECIP
AND TEMP TRENDS...HAVE DECIDED TO EXTEND THE FREEZING RAIN
ADVISORY THROUGH THE AFTERNOON AND HAVE ALSO INCLUDED KANE COUNTY
IN THE ADVISORY AS WELL. WILL NEED TO ALSO MONITOR THE AFTERNOON
PERIOD FOR THE REMAINING CWA...AS COLD ADVECTION SHOULD HELP TEMPS
LOWER AROUND FREEZING INTO THE LATE AFTERNOON PERIOD. WITH PRECIP
POSSIBLY LINGERING...COULD SEE SOME POSSIBLE LIGHT ICING IN AREAS
OUTSIDE OF THE ADVISORY. ALTHOUGH TEMPS SHOULD BE MARGINAL...AND
AM NOT OVERLY CONCERNED AT THIS TIME.
WITH REGARDS TO THE DENSE FOG...WITH INCREASING MOISTURE IN THE
BOUNDARY LAYER THIS PAST EVENING DENSE FOG DEVELOPED ALONG TO THE
NORTH OF THIS BOUNDARY. MANY REPORTS OF DENSE FOR WERE RECEIVED
THIS PAST EVENING ACROSS NORTHWEST INDIANA...PRIMARILY FOR LAKE
AND PORTER COUNTIES IN INDIANA. WITH THE BOUNDARY SITUATED AND
EXPECTED TO REMAIN THIS WAY THROUGH THE REMAINDER OF THE
MORNING...FEEL CURRENT DENSE FOG ADVISORY FOR THESE LOCATIONS
REMAINS VALID. ALTHOUGH...SOUTHERN AREAS OF COOK COUNTY AND
EASTERN AREAS OF WILL COUNTY WILL NEED TO BE MONITORED OVER THE
NEXT COUPLE OF HOURS AS VIS IN THESE LOCATIONS CONTINUES TO BOUNCE
AROUND 1/2 MILE. END TIMING FOR THIS DENSE FOG ADVISORY REMAINS 9
AM CST...AND SEEMS REASONABLE. THIS SAGGING BOUNDARY AND SLIGHTLY
DRIER AIR SHOULD HELP WITH THE MORE DENSE FOG...BUT WITH PATCHY
DENSE FOG STILL NOT OUT OF THE QUESTION AT LEAST THROUGH MID DAY.
CONFIDENCE WITH THIS FOG REMAINS LOW AT THIS TIME AND WILL NEED TO
MONITOR...POSSIBLY EXTENDING THIS ADVISORY OR MAYBE EVEN EXPANDING
IT LATER THIS MORNING.
WITH SURFACE LOW EXITING TO THE EAST THIS EVENING AND THE ARRIVAL
OF DRIER AIR...SHOULD OBSERVE OVERALL PRECIP CHANCES TO WIND DOWN
FOR THE TIME BEING. ALTHOUGH WITH GUIDANCE CONTINUING TO INDICATE
BROAD SCALE LIFT WITH THE APPROACHING LONGWAVE TROUGH TO THE WEST
IT DOES APPEAR AS IF AREAS ACROSS THE SOUTHERN CWA COULD SEE
ADDITIONAL PRECIP TONIGHT. ALTHOUGH LIGHT PRECIP...THERMAL
PROFILES WOULD INDICATE THAT THIS PRECIP WOULD BE IN THE FORM OF
LIGHT FREEZING RAIN OR LIGHT FREEZING DRIZZLE. ANOTHER PERIOD I AM
CONCERNED ABOUT AT THIS TIME IS LATE TONIGHT INTO EARLY SATURDAY
MORNING...ONCE AGAIN FOR AREAS ACROSS THE SOUTHERN CWA. WILL NEED
TO MONITOR SURFACE TEMP TRENDS ACROSS EAST CENTRAL ILLINOIS DURING
THIS TIME...WITH FREEZING RAIN ONCE AGAIN POSSIBLY BEING AN ISSUE.
EXPANDING PRECIP TO THE SOUTH IS EXPECTED TO INCH FURTHER NORTH
TOWARDS THE SOUTHERN CWA TOWARDS THE 12Z SATURDAY TIME
FRAME...WITH SOUTHWEST FLOW ALOFT PERSISTING OUT AHEAD OF THE
APPROACHING LONGWAVE TROUGH. WITH A SLOW TEMP TREND EXPECTED
SATURDAY MORNING...A PERIOD OF LIGHT FREEZING RAIN COULD CAUSE
SOME ISSUES PRIMARILY SOUTH OF I-80.
WITH REGARDS TO WINTER STORM SATURDAY THROUGH SUNDAY...LATEST
THINKING/UPDATES TO FORECAST CONTINUE TO SUPPORT CURRENT WINTER
STORM WATCH ACROSS NORTHERN PORTIONS OF THE CWA. EXPECTED VARYING
PRECIP TYPES INCLUDING ALMOST ALL WINTER PRECIP TYPES COULD BE
OBSERVED SATURDAY INTO SATURDAY NIGHT...WITH A VARYING THERMAL
PROFILE EXPECTED TO CHANGE THROUGH THE PERIOD FOR ALL AREAS. WILL
NEED TO MONITOR THE SATURDAY MORNING TIME FRAME INTO THE DAY
SATURDAY FOR THE VARYING PRECIP TYPE...POSSIBLY ADDING YET ANOTHER
HEADLINE TO ACCOMMODATE FOR THE WINTRY MIX. EXPECTED SURFACE LOW
TRACK STILL SUPPORTIVE FOR BEST CHANCES FOR SNOW OR ALL SNOW
ACROSS NORTHWEST AND NORTH CENTRAL ILLINOIS WITH SNOWFALL TOTALS
IN EXCESS OF 6 INCHES STILL APPEARING POSSIBLE. THE EXPECTED RAIN
SNOW LINE HAS VARIED SLIGHTLY...BUT THE GENERAL IDEA REMAINING THE
SAME. OHARE TO PERU ILLINOIS LINE ARE THE DIVIDING LINE AT THIS
TIME...WITH CURRENT SNOW FORECAST INDICATING RAPID INCREASE IN
SNOW AMOUNTS RIGHT TO THE NORTH OF THIS LINE AND WITH AREAS TO THE
SOUTH OBSERVING LIGHT SNOW ACCUMULATIONS.
ALTHOUGH LATEST TRENDS ARE INDICATING THAT THE AXIS OF HEAVIEST
RAINFALL IS BEGINNING TO SHIFT SOUTH OF THE CWA...DECENT RAINFALL
AMOUNTS OF UP TO AN INCH STILL SUPPORT THE POSSIBILITY OF
FLOODING...AND HAVE MADE NO CHANGES TO THE CURRENT FLOOD WATCH.
RODRIGUEZ
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* ONGOING IFR CIG/VSBY TRENDS.
* PRECIPITATION ENDING TIME AND POSSIBLE LIGHT FREEZING RAIN TODAY.
* WINDS BACKING NORTH THEN NORTHWEST.
LENNING
//DISCUSSION...UPDATED 18Z...
SO FAR AT MDW/ORD/GYY THE TEMPERATURES HAVE REMAINED ENOUGH ABOVE
FREEZING THAT ICE AT THE SFC HAS NOT BEEN A PROBLEM. DPA HAS BEEN
RIGHT ON THE LINE BUT STILL ABOVE FREEZING...WHILE RFD HAS BEEN
HAVING CONSIDERABLE ICE PROBLEMS. RADAR TRENDS SUGGEST ORD/MDW
PRECIP MAY END A BIT SOONER THAN PREVIOUSLY EXPECTED THIS
AFTERNOON...AND FCST SOUNDINGS SUGGEST INCOMING COLD AIR WOULD
PRODUCE ONLY A BRIEF PERIOD OF LIGHT FREEZING DRIZZLE AT WORST.
AFTER A BREAK IN PRECIP OVERNIGHT INTO TOMORROW MORNING...THE
NEXT LOW PRESSURE SYSTEM BEGINS AFFECTING THE AREA. AS PRECIP
DEVELOPS TOWARD MIDDAY TOMORROW...AGAIN THE FREEZING LINE WILL LIE
VERY CLOSE TO THE TERMINALS. TAFS REFLECT THE MORE OPTIMISTIC VIEW
THAT ORD/MDW REMAIN ON THE LIQUID SIDE AT LEAST THROUGH THE
AFTERNOON.
IF PRECIP REMAINS MOSTLY LIQUID THEN CIG/VSBY AND WIND TRENDS WILL
BE THE BIGGER ISSUES. AM NOT SEEING MUCH EITHER IN THE
OBSERVATIONS OR IN FCST GUIDANCE TO SUGGEST CIGS WILL IMPROVE
ABOVE IFR THROUGH THE AFTERNOON...AND SOME POSSIBILITY EXISTS FOR
LIFR. VSBYS ARE IN SLIGHTLY BETTER SHAPE.
STILL THINK WINDS WILL BACK TO NORTHWEST BY THIS EVENING THEN
FLUCTUATE BETWEEN NNW AND NNW TONIGHT AND TOMORROW AS THE LOW
PRESSURE SYSTEMS TO OUR SOUTH MIGRATE THROUGH THE AREA.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* LOW CONFIDENCE ABOUT EXACT CIG/VSBY TRENDS THIS AFTERNOON BUT
FAVOR MOSTLY IFR WITH OCCASIONAL LIFR CIGS AND VFR VSBYS.
* WINDS HAVE BEEN STEADY NNE BUT STILL MEDIUM TO HIGH CONFIDENCE
THAT TREND WILL VERY SOON BE MORE NORTHERLY THIS AFTERNOON.
* LOW CONFIDENCE ON HOW LOW CIGS GO OVERNIGHT.
* MEDIUM CONFIDENCE ON TIMING OF PRECIP TOMORROW BUT LOW
CONFIDENCE IN PRECIP TYPE TOMORROW AFTERNOON.
LENNING
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...WINTRY MIX...IFR LIKELY.
SUNDAY...SNOW AND IFR.
MONDAY...CHANCE FOR SNOW...MVFR/IFR POSSIBLE.
TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE SNOW...MVFR POSSIBLE.
THURSDAY...MVFR BECOMING VFR.
MDB
&&
.MARINE...
218 PM...LOW PRESSURE OVER CENTRAL ILLINOIS WILL MOVE NORTHEAST
ACROSS THE EASTERN LAKES TONIGHT AS IT SLOWLY WEAKENS AS WEAK HIGH
PRESSURE OVER THE UPPER MIDWEST IS ABSORBED BY STRONGER HIGH
PRESSURE MOVING ACROSS SOUTHERN CANADA SATURDAY AND SATURDAY
NIGHT. THE GRADIENT WILL SLOWLY WEAKEN TONIGHT WITH SPEEDS IN THE
10-15 KT RANGE BY MORNING. NEW LOW PRESSURE WILL DEVELOP OVER
TEXAS TONIGHT AND MOVE NORTHEAST TO NORTHERN INDIANA BY SUNDAY
MORNING. AS THIS LOW APPROACHES THE LAKES REGION...IT WILL DEEPEN
AND THE GRADIENT WILL TIGHTEN BETWEEN THE STRONGER HIGH ACROSS
SOUTHERN CANADA. NORTHEAST WINDS WILL STEADILY INCREASE SATURDAY
EVENING WITH 30 KTS EXPECTED. DEPENDING ON THE EXACT STRENGTH AND
TRACK OF THIS LOW...ITS POSSIBLE THERE COULD BE A PERIOD OF LOW
END GALES BUT CONFIDENCE IS TOO LOW TO INCLUDE IN THIS FORECAST. A
TROUGH OF LOW PRESSURE WILL THEN LINGER ACROSS THE WESTERN LAKES
REGION SUNDAY NIGHT WITH NORTHERLY WINDS SHIFTING NORTHWESTERLY.
STRONG HIGH PRESSURE WILL BUILD ACROSS THE PLAINS SUNDAY AND
SUNDAY NIGHT AND THEN SHIFT EAST ACROSS THE LAKES REGION MONDAY
NIGHT AND TUESDAY. THERE IS A POTENTIAL FOR A PERIOD OF STRONG
WINDS AHEAD OF THE HIGH...IN THE MONDAY/MONDAY NIGHT TIME PERIOD.
BUT CONFIDENCE REGARDING SPECIFICS DURING THIS TIME PERIOD REMAIN
LOW. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 7 PM FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
DENSE FOG ADVISORY...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 7 PM
FRIDAY.
FLOOD WATCH...ILZ033-ILZ039...NOON SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 7
PM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...NOON SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM FRIDAY.
&&
$$
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
257 PM CST FRI DEC 20 2013
.DISCUSSION...
1155 AM CST
HAVE CONTINUED ALL CURRENT HEADLINES AS IS INTO THIS AFTERNOON.
NO SIGNIFICANT CHANGES ARE AT LEAST PLANNED THIS AFTERNOON FOR THE
WINTER STORM WATCH THAT IS IN EFFECT FOR SATURDAY NIGHT INTO
SUNDAY. HOWEVER...WE CONTINUE TO ANALYZE THE POTENTIAL FOR
FREEZING RAIN TO THE SOUTH OF THE CURRENT WATCH...INCLUDING EVEN
DURING THE DAY SATURDAY. THIS MAY REQUIRE A WINTER WEATHER
HEADLINE.
WATER VAPOR SHOWS SOME RELATIVE DRYING MOVING OVER THE AREA IN
THIS DEEP SOUTHWEST MOIST PLUME AND THAT ALONG WITH JUST LESS
ASCENT IS LIKELY RESPONSIBLE FOR THE DIMINISHING SHOWER COVERAGE.
THIS TREND SHOULD SLOWLY CONTINUE ALTHOUGH PROFILES REMAIN AT
LEAST SUPPORTIVE OF DRIZZLE THROUGH THE AFTERNOON. THE FREEZING
LINE HAS MAINTAINED ITS GROUND THROUGH THE PAST SEVERAL HOURS AND
EXPECT VERY LITTLE CHANGE WITH THAT THROUGH MID AFTERNOON...HENCE
THE PRESERVING OF THE FREEZING RAIN ADVISORY.
WHILE VISIBILITY OBSERVATIONS OF DENSE FOG ARE FAR MORE SPOTTY IN
THE SOUTHERN CWA THAN THEY WERE THIS MORNING...THE SHOWERS HAVE
LIKELY BEEN PARTLY RESPONSIBLE FOR THE SOMEWHAT CHAOTIC VISIBILITY
FIELD. WITH CONTINUED MOISTURE POOLING FROM ADVECTION AND
SNOW SUBLIMATION...ALONG WITH LIGHT WINDS IMMEDIATELY ALONG THE
BOUNDARY...WILL CONTINUE THAT ADVISORY AS IS UNTIL 3 PM.
AS THE SURFACE LOW MOVES INTO NORTH CENTRAL IN BY 4-5 PM...THE
SOMEWHAT DEEPER NORTHERLY FLOW IN THE LOW-LEVELS...ALONG WITH
NIGHTFALL SHOULD ADVANCE THE FREEZING LINE SOUTHWARD. FORCING FOR
PRECIP INTO TONIGHT LOOKS TO BE MAINLY DRIZZLE AS ANY APPRECIABLE
MOISTURE TRANSPORT SHIFTS SOUTHEAST AND THERE IS A LACK OF ANY
REAL SHORT WAVE IMPULSES PRESENTLY FORECAST. SOUNDINGS MARGINALLY
SUPPORTIVE OF DRIZZLE ARE MAINLY INDICATED IN THE SOUTHERN
FORECAST AREA. OVERALL NOT FEELING THAT A HEADLINE WILL BE
NEEDED...AND MORE SO HANDLED WITH AN SPS. IT IS POSSIBLE THE
CURRENT FREEZING RAIN ADVISORY IS EXTENDED UNTIL 6-7 PM TO ACCOUNT
FOR THE LATE AFTERNOON RUSH IF RADAR TRENDS AND REPORTS CONTINUE
TO INDICATE SHOWERS AND DRIZZLE OVER THE SUBFREEZING BOUNDARY
LAYER AS WE NEAR 3 PM.
MTF
//PREV DISCUSSION...
355 AM CST
SEVERAL ISSUES ONGOING THIS MORNING AS WELL THROUGH THE
WEEKEND...WITH DENSE FOG AND FREEZING RAIN ISSUES THIS MORNING
WITH THE FREEZING RAIN NOW LINGERING INTO THE AFTERNOON AND
POSSIBLY TONIGHT...CONTINUED FLOODING CONCERNS...AND LASTLY
POTENTIAL SNOWFALL WHICH THE AXIS OF HEAVIEST SNOW STILL APPEARS
TO BE ACROSS THE NORTH AND NORTHWEST AREAS OF THE CWA.
ADDRESSING THE MORE IMPORTANT ISSUES IN THE NEAR TERM...LIGHT
FREEZING RAIN OR FREEZING DRIZZLE CONTINUES ACROSS THE ADVISORY
AREA THIS MORNING...WITH LIGHT RAIN OR DRIZZLE ONGOING FOR THE
REMAINDER OF THE CWA. BROAD SOUTHWESTERLY FLOW ALOFT CONTINUES TO
USHER SEVERAL WAVES OF ENERGY...WITH ELONGATED TROUGH OF LOW
PRESSURE EXTENDING FROM THE CENTRAL PLAINS UP THROUGH SOUTHERN
GREAT LAKES. AS THESE WAVES OF ENERGY/SPEED MAXES LIFT NORTHEAST
ACROSS THE REGION THIS MORNING...EXPECT THIS TROUGH OF LOW
PRESSURE TO LIFT EAST NORTHEAST TO CENTRAL ILLINOIS AND NORTHWEST
INDIANA THROUGH THE EARLY AFTERNOON. PRESENT LOW/MID LEVEL
CONVERGENCE WILL CONTINUE TO BE A PERSISTENT THROUGH THIS
PERIOD...WITH CURRENT UPSTREAM WAVE TO AID IN TIGHTENING LOW/MID
LEVEL BAROCLINIC ZONE. THIS WILL ENHANCE FRONTOGENETIC FORCING
ACROSS THE ADVISORY AREA...ALL AIDING IN CONTINUED PRECIP
DEVELOPMENT AT LEAST THROUGH EARLY AFTERNOON FOR THE ENTIRE CWA.
HAVE INCREASED POPS THIS MORNING AND EARLY AFTERNOON...BUT WONDER
IF AFTERNOON POPS WILL NEED TO BE RAISED EVEN FURTHER WITH SHORT
TERM GUIDANCE HINTING AT CONTINUED TO DEVELOPMENT EVEN INTO THE
LATE AFTERNOON. ALTHOUGH CURRENT ASSOCIATED BOUNDARY DRAPED ACROSS
EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA DID MAKE SOME
NORTHWARD PROGRESSION EARLY THIS MORNING...FEEL THAT THIS
NORTHWARD MOVEMENT HAS ENDED AND WILL REMAIN SITUATED UNTIL
DROPPING SOUTH/SOUTHEAST OF THE CWA THIS AFTERNOON. GUIDANCE
HINTING AT SOME WEAK CAA TO BEGIN OCCURRING OVER THE NEXT SEVERAL
HOURS AND WITH LATEST RAP ANALYSIS ALREADY INDICATING THIS ACROSS
WESTERN ILLINOIS...FEEL PRETTY CONFIDENT WITH THIS TREND. THIS
WILL HELP TEMPS IN THE ADVISORY AREA TO HOVER JUST BELOW OR AT THE
FREEZING MARK THROUGH MOST OF TODAY. WITH THIS CONTINUED PRECIP
AND TEMP TRENDS...HAVE DECIDED TO EXTEND THE FREEZING RAIN
ADVISORY THROUGH THE AFTERNOON AND HAVE ALSO INCLUDED KANE COUNTY
IN THE ADVISORY AS WELL. WILL NEED TO ALSO MONITOR THE AFTERNOON
PERIOD FOR THE REMAINING CWA...AS COLD ADVECTION SHOULD HELP TEMPS
LOWER AROUND FREEZING INTO THE LATE AFTERNOON PERIOD. WITH PRECIP
POSSIBLY LINGERING...COULD SEE SOME POSSIBLE LIGHT ICING IN AREAS
OUTSIDE OF THE ADVISORY. ALTHOUGH TEMPS SHOULD BE MARGINAL...AND
AM NOT OVERLY CONCERNED AT THIS TIME.
WITH REGARDS TO THE DENSE FOG...WITH INCREASING MOISTURE IN THE
BOUNDARY LAYER THIS PAST EVENING DENSE FOG DEVELOPED ALONG TO THE
NORTH OF THIS BOUNDARY. MANY REPORTS OF DENSE FOR WERE RECEIVED
THIS PAST EVENING ACROSS NORTHWEST INDIANA...PRIMARILY FOR LAKE
AND PORTER COUNTIES IN INDIANA. WITH THE BOUNDARY SITUATED AND
EXPECTED TO REMAIN THIS WAY THROUGH THE REMAINDER OF THE
MORNING...FEEL CURRENT DENSE FOG ADVISORY FOR THESE LOCATIONS
REMAINS VALID. ALTHOUGH...SOUTHERN AREAS OF COOK COUNTY AND
EASTERN AREAS OF WILL COUNTY WILL NEED TO BE MONITORED OVER THE
NEXT COUPLE OF HOURS AS VIS IN THESE LOCATIONS CONTINUES TO BOUNCE
AROUND 1/2 MILE. END TIMING FOR THIS DENSE FOG ADVISORY REMAINS 9
AM CST...AND SEEMS REASONABLE. THIS SAGGING BOUNDARY AND SLIGHTLY
DRIER AIR SHOULD HELP WITH THE MORE DENSE FOG...BUT WITH PATCHY
DENSE FOG STILL NOT OUT OF THE QUESTION AT LEAST THROUGH MID DAY.
CONFIDENCE WITH THIS FOG REMAINS LOW AT THIS TIME AND WILL NEED TO
MONITOR...POSSIBLY EXTENDING THIS ADVISORY OR MAYBE EVEN EXPANDING
IT LATER THIS MORNING.
WITH SURFACE LOW EXITING TO THE EAST THIS EVENING AND THE ARRIVAL
OF DRIER AIR...SHOULD OBSERVE OVERALL PRECIP CHANCES TO WIND DOWN
FOR THE TIME BEING. ALTHOUGH WITH GUIDANCE CONTINUING TO INDICATE
BROAD SCALE LIFT WITH THE APPROACHING LONGWAVE TROUGH TO THE WEST
IT DOES APPEAR AS IF AREAS ACROSS THE SOUTHERN CWA COULD SEE
ADDITIONAL PRECIP TONIGHT. ALTHOUGH LIGHT PRECIP...THERMAL
PROFILES WOULD INDICATE THAT THIS PRECIP WOULD BE IN THE FORM OF
LIGHT FREEZING RAIN OR LIGHT FREEZING DRIZZLE. ANOTHER PERIOD I AM
CONCERNED ABOUT AT THIS TIME IS LATE TONIGHT INTO EARLY SATURDAY
MORNING...ONCE AGAIN FOR AREAS ACROSS THE SOUTHERN CWA. WILL NEED
TO MONITOR SURFACE TEMP TRENDS ACROSS EAST CENTRAL ILLINOIS DURING
THIS TIME...WITH FREEZING RAIN ONCE AGAIN POSSIBLY BEING AN ISSUE.
EXPANDING PRECIP TO THE SOUTH IS EXPECTED TO INCH FURTHER NORTH
TOWARDS THE SOUTHERN CWA TOWARDS THE 12Z SATURDAY TIME
FRAME...WITH SOUTHWEST FLOW ALOFT PERSISTING OUT AHEAD OF THE
APPROACHING LONGWAVE TROUGH. WITH A SLOW TEMP TREND EXPECTED
SATURDAY MORNING...A PERIOD OF LIGHT FREEZING RAIN COULD CAUSE
SOME ISSUES PRIMARILY SOUTH OF I-80.
WITH REGARDS TO WINTER STORM SATURDAY THROUGH SUNDAY...LATEST
THINKING/UPDATES TO FORECAST CONTINUE TO SUPPORT CURRENT WINTER
STORM WATCH ACROSS NORTHERN PORTIONS OF THE CWA. EXPECTED VARYING
PRECIP TYPES INCLUDING ALMOST ALL WINTER PRECIP TYPES COULD BE
OBSERVED SATURDAY INTO SATURDAY NIGHT...WITH A VARYING THERMAL
PROFILE EXPECTED TO CHANGE THROUGH THE PERIOD FOR ALL AREAS. WILL
NEED TO MONITOR THE SATURDAY MORNING TIME FRAME INTO THE DAY
SATURDAY FOR THE VARYING PRECIP TYPE...POSSIBLY ADDING YET ANOTHER
HEADLINE TO ACCOMMODATE FOR THE WINTRY MIX. EXPECTED SURFACE LOW
TRACK STILL SUPPORTIVE FOR BEST CHANCES FOR SNOW OR ALL SNOW
ACROSS NORTHWEST AND NORTH CENTRAL ILLINOIS WITH SNOWFALL TOTALS
IN EXCESS OF 6 INCHES STILL APPEARING POSSIBLE. THE EXPECTED RAIN
SNOW LINE HAS VARIED SLIGHTLY...BUT THE GENERAL IDEA REMAINING THE
SAME. OHARE TO PERU ILLINOIS LINE ARE THE DIVIDING LINE AT THIS
TIME...WITH CURRENT SNOW FORECAST INDICATING RAPID INCREASE IN
SNOW AMOUNTS RIGHT TO THE NORTH OF THIS LINE AND WITH AREAS TO THE
SOUTH OBSERVING LIGHT SNOW ACCUMULATIONS.
ALTHOUGH LATEST TRENDS ARE INDICATING THAT THE AXIS OF HEAVIEST
RAINFALL IS BEGINNING TO SHIFT SOUTH OF THE CWA...DECENT RAINFALL
AMOUNTS OF UP TO AN INCH STILL SUPPORT THE POSSIBILITY OF
FLOODING...AND HAVE MADE NO CHANGES TO THE CURRENT FLOOD WATCH.
RODRIGUEZ
.EXTENDED FORECAST PERIOD...FROM MONDAY MORNING THROUGH FRIDAY...
INCLUDING THE CHRISTMAS HOLIDAY...
UPDATED...300PM CST...
THE SENSIBLE WEATHER WILL QUIET CONSIDERABLY WITH THE MAIN FORECAST
CONCERNS FOCUSING ON TEMPERATURES AND THE CHANCE FOR SOME LIGHT
SNOW ON CHRISTMAS EVE AND EARLY CHRISTMAS DAY. THE GENERAL TREND
FOR THE EXTENDED FORECAST PERIOD WILL BE FOR MUCH BELOW NORMAL
TEMPERATURES WITH THE ONLY CHANCE FOR SOME LIGHT SNOW ON CHRISTMAS
EVE INTO CHRISTMAS DAY.
A HIGH AMPLITUDE LONGWAVE TROUGH IS EXPECTED TO CARVE OUT OVER THE
CNTRL CONUS WITH THE TROUGH AXIS EXTENDING FROM HUDSON BAY THROUGH
CENTRAL TEXAS. INITIALLY ON MONDAY...THE LOCAL AREA WILL SEE THE
TROUGH AXIS MOVING THROUGH THE AREA TRANSITIONING THE REGION FROM
RELATIVE WARM ADVECTION TO STRONG COLD ADVECTION. TEMPERATURES WILL
DROP OFF QUICKLY BY MONDAY MORNING...WITH LOWS EXPECTED TO DROP ONTO
THE SINGLE DIGITS WEST OF THE FOX VALLEY AND I-55 CORRIDOR. LOWS
OVER THE EASTERN PORTION OF THE FORECAST AREA SHOULD HANG IN THE
MIDDLE TO UPPER TEENS. AS THE LONGWAVE TROUGH CONTINUES TO THE ERN
CONUS MONDAY AND MONDAY NIGHT...WEAK UPPER RIDGING WILL BUILD ACROSS
THE UPPER MISSISSIPPI VALLEY...WITH THE AMPLITUDE OF THE UPPER LEVEL
PATTERN CONTINUING TO AMPLIFY. WITH DEEP LAYER FLOW REMAINING ON
THE NWLY FLOW SIDE OF THE UPPER RIDGE...TEMPERATURES WILL CONTINUE
TO DROP WITH LOWS TUESDAY MORNING BELOW ZERO OVER MUCH OF THE CWA...
GENERALLY WEST OF A LINE FROM WAUKEGAN TO PONTIAC...WITH THE
COLDEST AIR OVER THE ROCKFORD AREA WHERE TEMPS SHOULD BOTTOM OUT AT
-5F TO -10F. WIND CHILLS WILL BE A CONCERN AS WELL. WITH WINDS OF
5-10 KT LIKELY...WIND CHILLS WILL APPROACH THE -20F WIND CHILL
ADVISORY CRITERIA WEST OF THE FOX VALLEY AND I-55 CORRIDOR. BY
TUESDAY NIGHT...THE LONGER RANGE MODELS ARE ADVERTISING A PAIR OF
NORTHERN STREAM SHORTWAVES TRACKING ACROSS THE NRN PLAINS. THE
NRN-MOST WAVE...WHICH IS ALSO THE STRONGER OF THE PAIR...SHOULD
TRACK TO THE EAST...ACROSS THE UPPER GREAT LAKES WHILE THE MORE
SOUTHERLY...WEAKER WAVE DROPS THROUGH THE NRN PLAINS TO THE MIDDLE
MISSISSIPPI VALLEY. THIS THERE IS SOME DISCREPANCY AMONG THE LONGER
RANGE GUIDANCE ON THE SPEED OF PROGRESSION OF THIS WAVE...BUT THE
GENERAL CONSENSUS IS THAT THE WAVE WILL CROSS THE MIDDLE MISSISSIPPI
VALLEY...TRACKING OVER THE IL/WI BOARDER. FOLLOWING A PERIOD OF
STRONG COLD/DRY ADVECTION...THERE WILL BE LITTLE IN SITU MOISTURE
FOR THE SYSTEM TO WORK WITH AND WILL LARGELY HAVE TO RELY ON
DYNAMICS TO PRODUCE ANY PCPN. AT THIS POINT...ANTICIPATE THAT UPPER
DYNAMICS SHOULD BE STRONG ENOUGH TO PRODUCE AT LEAST SOME LIGHT SNOW
FOR LATE CHRISTMAS EVE INTO EARLY CHRISTMAS DAY. GIVEN THE LACK OF
DEEP LAYER MOISTURE OR ANY SIGNIFICANT LOW LEVEL MOISTURE TRANSPORT
AS FLOW THROUGH THE LOWER LEVELS SHOULD BE MORE WESTERLY AND UNABLE
TO TAP ANY GULF MOISTURE...ANY ACCUMULATIONS WILL LIKELY BE LIGHT.
A BRIEF PERIOD OF MORE WLY OR AT LEAST BROAD...FLAT TROUGHING SHOULD
COVER THE MIDWEST ON WEDNESDAY...ALLOWING FOR SOME MODERATION OF
TEMPERATURES ON WEDNESDAY AND THURSDAY...WITH HIGHS IN THE UPPER 20S
TO LOWER 30S ON WEDNESDAY AND UPPER TEENS TO MIDDLE 20S ON THURSDAY.
A REINFORCING SHOT OF COLD AIR ASSOCIATED WITH A STRONG NORTHERN
STREAM SHORTWAVE DIGGING INTO THE UPPER MISSISSIPPI VALLEY AND
SOUTHERN GREAT LAKES WILL BRING SUB-ZERO TEMPERATURES BACK TO MUCH
OF THE CWA FOR FRIDAY MORNING.
KREIN
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* ONGOING IFR CIG/VSBY TRENDS.
* PRECIPITATION ENDING TIME AND POSSIBLE LIGHT FREEZING RAIN TODAY.
* WINDS BACKING NORTH THEN NORTHWEST.
LENNING
//DISCUSSION...UPDATED 18Z...
SO FAR AT MDW/ORD/GYY THE TEMPERATURES HAVE REMAINED ENOUGH ABOVE
FREEZING THAT ICE AT THE SFC HAS NOT BEEN A PROBLEM. DPA HAS BEEN
RIGHT ON THE LINE BUT STILL ABOVE FREEZING...WHILE RFD HAS BEEN
HAVING CONSIDERABLE ICE PROBLEMS. RADAR TRENDS SUGGEST ORD/MDW
PRECIP MAY END A BIT SOONER THAN PREVIOUSLY EXPECTED THIS
AFTERNOON...AND FCST SOUNDINGS SUGGEST INCOMING COLD AIR WOULD
PRODUCE ONLY A BRIEF PERIOD OF LIGHT FREEZING DRIZZLE AT WORST.
AFTER A BREAK IN PRECIP OVERNIGHT INTO TOMORROW MORNING...THE
NEXT LOW PRESSURE SYSTEM BEGINS AFFECTING THE AREA. AS PRECIP
DEVELOPS TOWARD MIDDAY TOMORROW...AGAIN THE FREEZING LINE WILL LIE
VERY CLOSE TO THE TERMINALS. TAFS REFLECT THE MORE OPTIMISTIC VIEW
THAT ORD/MDW REMAIN ON THE LIQUID SIDE AT LEAST THROUGH THE
AFTERNOON.
IF PRECIP REMAINS MOSTLY LIQUID THEN CIG/VSBY AND WIND TRENDS WILL
BE THE BIGGER ISSUES. AM NOT SEEING MUCH EITHER IN THE
OBSERVATIONS OR IN FCST GUIDANCE TO SUGGEST CIGS WILL IMPROVE
ABOVE IFR THROUGH THE AFTERNOON...AND SOME POSSIBILITY EXISTS FOR
LIFR. VSBYS ARE IN SLIGHTLY BETTER SHAPE.
STILL THINK WINDS WILL BACK TO NORTHWEST BY THIS EVENING THEN
FLUCTUATE BETWEEN NNW AND NNW TONIGHT AND TOMORROW AS THE LOW
PRESSURE SYSTEMS TO OUR SOUTH MIGRATE THROUGH THE AREA.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* LOW CONFIDENCE ABOUT EXACT CIG/VSBY TRENDS THIS AFTERNOON BUT
FAVOR MOSTLY IFR WITH OCCASIONAL LIFR CIGS AND VFR VSBYS.
* WINDS HAVE BEEN STEADY NNE BUT STILL MEDIUM TO HIGH CONFIDENCE
THAT TREND WILL VERY SOON BE MORE NORTHERLY THIS AFTERNOON.
* LOW CONFIDENCE ON HOW LOW CIGS GO OVERNIGHT.
* MEDIUM CONFIDENCE ON TIMING OF PRECIP TOMORROW BUT LOW
CONFIDENCE IN PRECIP TYPE TOMORROW AFTERNOON.
LENNING
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...WINTRY MIX...IFR LIKELY.
SUNDAY...SNOW AND IFR.
MONDAY...CHANCE FOR SNOW...MVFR/IFR POSSIBLE.
TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE SNOW...MVFR POSSIBLE.
THURSDAY...MVFR BECOMING VFR.
MDB
&&
.MARINE...
218 PM...LOW PRESSURE OVER CENTRAL ILLINOIS WILL MOVE NORTHEAST
ACROSS THE EASTERN LAKES TONIGHT AS IT SLOWLY WEAKENS AS WEAK HIGH
PRESSURE OVER THE UPPER MIDWEST IS ABSORBED BY STRONGER HIGH
PRESSURE MOVING ACROSS SOUTHERN CANADA SATURDAY AND SATURDAY
NIGHT. THE GRADIENT WILL SLOWLY WEAKEN TONIGHT WITH SPEEDS IN THE
10-15 KT RANGE BY MORNING. NEW LOW PRESSURE WILL DEVELOP OVER
TEXAS TONIGHT AND MOVE NORTHEAST TO NORTHERN INDIANA BY SUNDAY
MORNING. AS THIS LOW APPROACHES THE LAKES REGION...IT WILL DEEPEN
AND THE GRADIENT WILL TIGHTEN BETWEEN THE STRONGER HIGH ACROSS
SOUTHERN CANADA. NORTHEAST WINDS WILL STEADILY INCREASE SATURDAY
EVENING WITH 30 KTS EXPECTED. DEPENDING ON THE EXACT STRENGTH AND
TRACK OF THIS LOW...ITS POSSIBLE THERE COULD BE A PERIOD OF LOW
END GALES BUT CONFIDENCE IS TOO LOW TO INCLUDE IN THIS FORECAST. A
TROUGH OF LOW PRESSURE WILL THEN LINGER ACROSS THE WESTERN LAKES
REGION SUNDAY NIGHT WITH NORTHERLY WINDS SHIFTING NORTHWESTERLY.
STRONG HIGH PRESSURE WILL BUILD ACROSS THE PLAINS SUNDAY AND
SUNDAY NIGHT AND THEN SHIFT EAST ACROSS THE LAKES REGION MONDAY
NIGHT AND TUESDAY. THERE IS A POTENTIAL FOR A PERIOD OF STRONG
WINDS AHEAD OF THE HIGH...IN THE MONDAY/MONDAY NIGHT TIME PERIOD.
BUT CONFIDENCE REGARDING SPECIFICS DURING THIS TIME PERIOD REMAIN
LOW. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 7 PM FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
DENSE FOG ADVISORY...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 7 PM
FRIDAY.
FLOOD WATCH...ILZ033-ILZ039...NOON SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 7
PM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...NOON SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM FRIDAY.
&&
$$
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
218 PM CST FRI DEC 20 2013
.DISCUSSION...
1155 AM CST
HAVE CONTINUED ALL CURRENT HEADLINES AS IS INTO THIS AFTERNOON.
NO SIGNIFICANT CHANGES ARE AT LEAST PLANNED THIS AFTERNOON FOR THE
WINTER STORM WATCH THAT IS IN EFFECT FOR SATURDAY NIGHT INTO
SUNDAY. HOWEVER...WE CONTINUE TO ANALYZE THE POTENTIAL FOR
FREEZING RAIN TO THE SOUTH OF THE CURRENT WATCH...INCLUDING EVEN
DURING THE DAY SATURDAY. THIS MAY REQUIRE A WINTER WEATHER
HEADLINE.
WATER VAPOR SHOWS SOME RELATIVE DRYING MOVING OVER THE AREA IN
THIS DEEP SOUTHWEST MOIST PLUME AND THAT ALONG WITH JUST LESS
ASCENT IS LIKELY RESPONSIBLE FOR THE DIMINISHING SHOWER COVERAGE.
THIS TREND SHOULD SLOWLY CONTINUE ALTHOUGH PROFILES REMAIN AT
LEAST SUPPORTIVE OF DRIZZLE THROUGH THE AFTERNOON. THE FREEZING
LINE HAS MAINTAINED ITS GROUND THROUGH THE PAST SEVERAL HOURS AND
EXPECT VERY LITTLE CHANGE WITH THAT THROUGH MID AFTERNOON...HENCE
THE PRESERVING OF THE FREEZING RAIN ADVISORY.
WHILE VISIBILITY OBSERVATIONS OF DENSE FOG ARE FAR MORE SPOTTY IN
THE SOUTHERN CWA THAN THEY WERE THIS MORNING...THE SHOWERS HAVE
LIKELY BEEN PARTLY RESPONSIBLE FOR THE SOMEWHAT CHAOTIC VISIBILITY
FIELD. WITH CONTINUED MOISTURE POOLING FROM ADVECTION AND
SNOW SUBLIMATION...ALONG WITH LIGHT WINDS IMMEDIATELY ALONG THE
BOUNDARY...WILL CONTINUE THAT ADVISORY AS IS UNTIL 3 PM.
AS THE SURFACE LOW MOVES INTO NORTH CENTRAL IN BY 4-5 PM...THE
SOMEWHAT DEEPER NORTHERLY FLOW IN THE LOW-LEVELS...ALONG WITH
NIGHTFALL SHOULD ADVANCE THE FREEZING LINE SOUTHWARD. FORCING FOR
PRECIP INTO TONIGHT LOOKS TO BE MAINLY DRIZZLE AS ANY APPRECIABLE
MOISTURE TRANSPORT SHIFTS SOUTHEAST AND THERE IS A LACK OF ANY
REAL SHORT WAVE IMPULSES PRESENTLY FORECAST. SOUNDINGS MARGINALLY
SUPPORTIVE OF DRIZZLE ARE MAINLY INDICATED IN THE SOUTHERN
FORECAST AREA. OVERALL NOT FEELING THAT A HEADLINE WILL BE
NEEDED...AND MORE SO HANDLED WITH AN SPS. IT IS POSSIBLE THE
CURRENT FREEZING RAIN ADVISORY IS EXTENDED UNTIL 6-7 PM TO ACCOUNT
FOR THE LATE AFTERNOON RUSH IF RADAR TRENDS AND REPORTS CONTINUE
TO INDICATE SHOWERS AND DRIZZLE OVER THE SUBFREEZING BOUNDARY
LAYER AS WE NEAR 3 PM.
MTF
//PREV DISCUSSION...
355 AM CST
SEVERAL ISSUES ONGOING THIS MORNING AS WELL THROUGH THE
WEEKEND...WITH DENSE FOG AND FREEZING RAIN ISSUES THIS MORNING
WITH THE FREEZING RAIN NOW LINGERING INTO THE AFTERNOON AND
POSSIBLY TONIGHT...CONTINUED FLOODING CONCERNS...AND LASTLY
POTENTIAL SNOWFALL WHICH THE AXIS OF HEAVIEST SNOW STILL APPEARS
TO BE ACROSS THE NORTH AND NORTHWEST AREAS OF THE CWA.
ADDRESSING THE MORE IMPORTANT ISSUES IN THE NEAR TERM...LIGHT
FREEZING RAIN OR FREEZING DRIZZLE CONTINUES ACROSS THE ADVISORY
AREA THIS MORNING...WITH LIGHT RAIN OR DRIZZLE ONGOING FOR THE
REMAINDER OF THE CWA. BROAD SOUTHWESTERLY FLOW ALOFT CONTINUES TO
USHER SEVERAL WAVES OF ENERGY...WITH ELONGATED TROUGH OF LOW
PRESSURE EXTENDING FROM THE CENTRAL PLAINS UP THROUGH SOUTHERN
GREAT LAKES. AS THESE WAVES OF ENERGY/SPEED MAXES LIFT NORTHEAST
ACROSS THE REGION THIS MORNING...EXPECT THIS TROUGH OF LOW
PRESSURE TO LIFT EAST NORTHEAST TO CENTRAL ILLINOIS AND NORTHWEST
INDIANA THROUGH THE EARLY AFTERNOON. PRESENT LOW/MID LEVEL
CONVERGENCE WILL CONTINUE TO BE A PERSISTENT THROUGH THIS
PERIOD...WITH CURRENT UPSTREAM WAVE TO AID IN TIGHTENING LOW/MID
LEVEL BAROCLINIC ZONE. THIS WILL ENHANCE FRONTOGENETIC FORCING
ACROSS THE ADVISORY AREA...ALL AIDING IN CONTINUED PRECIP
DEVELOPMENT AT LEAST THROUGH EARLY AFTERNOON FOR THE ENTIRE CWA.
HAVE INCREASED POPS THIS MORNING AND EARLY AFTERNOON...BUT WONDER
IF AFTERNOON POPS WILL NEED TO BE RAISED EVEN FURTHER WITH SHORT
TERM GUIDANCE HINTING AT CONTINUED TO DEVELOPMENT EVEN INTO THE
LATE AFTERNOON. ALTHOUGH CURRENT ASSOCIATED BOUNDARY DRAPED ACROSS
EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA DID MAKE SOME
NORTHWARD PROGRESSION EARLY THIS MORNING...FEEL THAT THIS
NORTHWARD MOVEMENT HAS ENDED AND WILL REMAIN SITUATED UNTIL
DROPPING SOUTH/SOUTHEAST OF THE CWA THIS AFTERNOON. GUIDANCE
HINTING AT SOME WEAK CAA TO BEGIN OCCURRING OVER THE NEXT SEVERAL
HOURS AND WITH LATEST RAP ANALYSIS ALREADY INDICATING THIS ACROSS
WESTERN ILLINOIS...FEEL PRETTY CONFIDENT WITH THIS TREND. THIS
WILL HELP TEMPS IN THE ADVISORY AREA TO HOVER JUST BELOW OR AT THE
FREEZING MARK THROUGH MOST OF TODAY. WITH THIS CONTINUED PRECIP
AND TEMP TRENDS...HAVE DECIDED TO EXTEND THE FREEZING RAIN
ADVISORY THROUGH THE AFTERNOON AND HAVE ALSO INCLUDED KANE COUNTY
IN THE ADVISORY AS WELL. WILL NEED TO ALSO MONITOR THE AFTERNOON
PERIOD FOR THE REMAINING CWA...AS COLD ADVECTION SHOULD HELP TEMPS
LOWER AROUND FREEZING INTO THE LATE AFTERNOON PERIOD. WITH PRECIP
POSSIBLY LINGERING...COULD SEE SOME POSSIBLE LIGHT ICING IN AREAS
OUTSIDE OF THE ADVISORY. ALTHOUGH TEMPS SHOULD BE MARGINAL...AND
AM NOT OVERLY CONCERNED AT THIS TIME.
WITH REGARDS TO THE DENSE FOG...WITH INCREASING MOISTURE IN THE
BOUNDARY LAYER THIS PAST EVENING DENSE FOG DEVELOPED ALONG TO THE
NORTH OF THIS BOUNDARY. MANY REPORTS OF DENSE FOR WERE RECEIVED
THIS PAST EVENING ACROSS NORTHWEST INDIANA...PRIMARILY FOR LAKE
AND PORTER COUNTIES IN INDIANA. WITH THE BOUNDARY SITUATED AND
EXPECTED TO REMAIN THIS WAY THROUGH THE REMAINDER OF THE
MORNING...FEEL CURRENT DENSE FOG ADVISORY FOR THESE LOCATIONS
REMAINS VALID. ALTHOUGH...SOUTHERN AREAS OF COOK COUNTY AND
EASTERN AREAS OF WILL COUNTY WILL NEED TO BE MONITORED OVER THE
NEXT COUPLE OF HOURS AS VIS IN THESE LOCATIONS CONTINUES TO BOUNCE
AROUND 1/2 MILE. END TIMING FOR THIS DENSE FOG ADVISORY REMAINS 9
AM CST...AND SEEMS REASONABLE. THIS SAGGING BOUNDARY AND SLIGHTLY
DRIER AIR SHOULD HELP WITH THE MORE DENSE FOG...BUT WITH PATCHY
DENSE FOG STILL NOT OUT OF THE QUESTION AT LEAST THROUGH MID DAY.
CONFIDENCE WITH THIS FOG REMAINS LOW AT THIS TIME AND WILL NEED TO
MONITOR...POSSIBLY EXTENDING THIS ADVISORY OR MAYBE EVEN EXPANDING
IT LATER THIS MORNING.
WITH SURFACE LOW EXITING TO THE EAST THIS EVENING AND THE ARRIVAL
OF DRIER AIR...SHOULD OBSERVE OVERALL PRECIP CHANCES TO WIND DOWN
FOR THE TIME BEING. ALTHOUGH WITH GUIDANCE CONTINUING TO INDICATE
BROAD SCALE LIFT WITH THE APPROACHING LONGWAVE TROUGH TO THE WEST
IT DOES APPEAR AS IF AREAS ACROSS THE SOUTHERN CWA COULD SEE
ADDITIONAL PRECIP TONIGHT. ALTHOUGH LIGHT PRECIP...THERMAL
PROFILES WOULD INDICATE THAT THIS PRECIP WOULD BE IN THE FORM OF
LIGHT FREEZING RAIN OR LIGHT FREEZING DRIZZLE. ANOTHER PERIOD I AM
CONCERNED ABOUT AT THIS TIME IS LATE TONIGHT INTO EARLY SATURDAY
MORNING...ONCE AGAIN FOR AREAS ACROSS THE SOUTHERN CWA. WILL NEED
TO MONITOR SURFACE TEMP TRENDS ACROSS EAST CENTRAL ILLINOIS DURING
THIS TIME...WITH FREEZING RAIN ONCE AGAIN POSSIBLY BEING AN ISSUE.
EXPANDING PRECIP TO THE SOUTH IS EXPECTED TO INCH FURTHER NORTH
TOWARDS THE SOUTHERN CWA TOWARDS THE 12Z SATURDAY TIME
FRAME...WITH SOUTHWEST FLOW ALOFT PERSISTING OUT AHEAD OF THE
APPROACHING LONGWAVE TROUGH. WITH A SLOW TEMP TREND EXPECTED
SATURDAY MORNING...A PERIOD OF LIGHT FREEZING RAIN COULD CAUSE
SOME ISSUES PRIMARILY SOUTH OF I-80.
WITH REGARDS TO WINTER STORM SATURDAY THROUGH SUNDAY...LATEST
THINKING/UPDATES TO FORECAST CONTINUE TO SUPPORT CURRENT WINTER
STORM WATCH ACROSS NORTHERN PORTIONS OF THE CWA. EXPECTED VARYING
PRECIP TYPES INCLUDING ALMOST ALL WINTER PRECIP TYPES COULD BE
OBSERVED SATURDAY INTO SATURDAY NIGHT...WITH A VARYING THERMAL
PROFILE EXPECTED TO CHANGE THROUGH THE PERIOD FOR ALL AREAS. WILL
NEED TO MONITOR THE SATURDAY MORNING TIME FRAME INTO THE DAY
SATURDAY FOR THE VARYING PRECIP TYPE...POSSIBLY ADDING YET ANOTHER
HEADLINE TO ACCOMMODATE FOR THE WINTRY MIX. EXPECTED SURFACE LOW
TRACK STILL SUPPORTIVE FOR BEST CHANCES FOR SNOW OR ALL SNOW
ACROSS NORTHWEST AND NORTH CENTRAL ILLINOIS WITH SNOWFALL TOTALS
IN EXCESS OF 6 INCHES STILL APPEARING POSSIBLE. THE EXPECTED RAIN
SNOW LINE HAS VARIED SLIGHTLY...BUT THE GENERAL IDEA REMAINING THE
SAME. OHARE TO PERU ILLINOIS LINE ARE THE DIVIDING LINE AT THIS
TIME...WITH CURRENT SNOW FORECAST INDICATING RAPID INCREASE IN
SNOW AMOUNTS RIGHT TO THE NORTH OF THIS LINE AND WITH AREAS TO THE
SOUTH OBSERVING LIGHT SNOW ACCUMULATIONS.
ALTHOUGH LATEST TRENDS ARE INDICATING THAT THE AXIS OF HEAVIEST
RAINFALL IS BEGINNING TO SHIFT SOUTH OF THE CWA...DECENT RAINFALL
AMOUNTS OF UP TO AN INCH STILL SUPPORT THE POSSIBILITY OF
FLOODING...AND HAVE MADE NO CHANGES TO THE CURRENT FLOOD WATCH.
RODRIGUEZ
MEDIUM AND LONG RANGE...MONDAY THROUGH THURSDAY...
MAIN CONCERNS BEYOND THIS WEEKEND ARE THE RETURN OF ARCTIC AIR AND
MUCH COLDER TEMPERATURES MONDAY-TUESDAY...AND THE POTENTIAL FOR A
LITTLE LIGHT SNOW CHRISTMAS EVE-CHRISTMAS DAY.
DEEP UPPER TROUGH TRAVERSING THE REGION MONDAY WITH FAIRLY
IMPRESSIVE SHORT WAVE ENERGY PASSING OVERHEAD. FORECAST SOUNDINGS
INDICATE SATURATION IN LOW LEVELS...WITH TEMPS NEAR -15C AS BOUNDARY
LAYER COOLS IN BLUSTERY COLD ADVECTION BEHIND DEPARTING WEEKEND LOW
PRESSURE SYSTEM. THIS SHOULD SUPPORT FLURRIES/LIGHT SNOW SHOWERS
ACROSS THE CWA INTO THE AFTERNOON HOURS. OF MORE IMPORTANCE THAN THE
POTENTIAL FOR LIGHT SNOW SHOWERS OR FLURRIES HOWEVER WILL BE THE
MUCH COLDER TEMPS AND WIND CHILLS AS ARCTIC AIR PLUNGES BACK INTO
THE REGION. TEMPS AT H8 FALL TO AROUND -16 C BY LATE AFTERNOON WITH
H9 TEMPS NEARLY SO...SUGGESTING SURFACE TEMPS MAY STRUGGLE TO RISE
ABOVE 10-15F AND WILL LIKELY FALL INTO THE SINGLE DIGITS ACROSS
NORTH CENTRAL IL AND WIND CHILLS IN THE NEGATIVE SINGLE DIGITS.
SURFACE HIGH PRESSURE RIDGE WILL BUILD ACROSS THE MISSISSIPPI VALLEY
AND INTO IL MONDAY NIGHT IN RESPONSE TO SUBSIDENCE BEHIND THE
DEPARTING UPPER TROUGH...WITH CLEARING SKIES...NEW SNOW COVER
ESPECIALLY FAR NORTHERN IL...AND DECREASING WINDS EXPECTED TO RESULT
IN STRONG RADIATIONAL COOLING. BOTH GFS AND ECMWF MOS DEPICT
SUB-ZERO LOWS ACROSS MUCH OF NORTHERN IL BY SUNRISE TUESDAY. SURFACE
HIGH PRESSURE RIDGE MOVES ACROSS THE AREA DURING THE DAY TUESDAY...
WITH WINDS BACKING TO THE SOUTH-SOUTHEAST DURING THE AFTERNOON AS
WARM ADVECTION DEVELOPS (ALOFT AT LEAST) IN ADVANCE OF A SHORT WAVE
EMERGING FROM THE PLAINS. MODERATION IN TEMPS LIMITED AT THE SURFACE
HOWEVER WITH VERY COLD START TO DAY AND STRONG INVERSION LIMITING
WARMING AT THE SURFACE WITH HIGHS IN THE TEENS/LOW 20S.
LONG RANGE GUIDANCE SIMILAR IN BRINGING SHORT WAVE TROUGH ACROSS
THE REGION DURING THE TUESDAY NIGHT/WEDNESDAY PERIOD AND ANOTHER
WEDNESDAY NIGHT/THURSDAY...THOUGH DIFFERENCES DO EXIST WITH
AMPLITUDE OF THESE INDIVIDUAL WAVES AND ASSOCIATED SURFACE
REFLECTIONS. THE ECMWF IS STRONGER/MORE AMPLIFIED WITH BOTH...
THOUGH AT THIS DISTANCE HAVE FOCUSED MAINLY ON SIMILARITIES BETWEEN
GUIDANCE. THIS YIELDS A LITTLE TEMPERATURE MODERATION CHRISTMAS EVE
AND CHRISTMAS DAY WITH A CHANCE OF SOME LIGHT SNOW...PERHAPS
0.5-1.0" BASED ON ROUGH QPF OUTPUT. LIGHT SNOW MAY LINGER ACROSS
THE EASTERN CWA CHRISTMAS NIGHT INTO THURSDAY WITH SURFACE COLD
FRONTAL TROUGH. AS MENTIONED...BRIEF MODERATION PRODUCES HIGHS IN
THE 20S/AROUND 30 FOR CHRISTMAS DAY THEN COLDER AIR LOOKS TO RETURN
THURSDAY BEHIND THE FRONT WITH TEMPS IN THE TEENS/LOW 20S.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* ONGOING IFR CIG/VSBY TRENDS.
* PRECIPITATION ENDING TIME AND POSSIBLE LIGHT FREEZING RAIN TODAY.
* WINDS BACKING NORTH THEN NORTHWEST.
LENNING
//DISCUSSION...UPDATED 18Z...
SO FAR AT MDW/ORD/GYY THE TEMPERATURES HAVE REMAINED ENOUGH ABOVE
FREEZING THAT ICE AT THE SFC HAS NOT BEEN A PROBLEM. DPA HAS BEEN
RIGHT ON THE LINE BUT STILL ABOVE FREEZING...WHILE RFD HAS BEEN
HAVING CONSIDERABLE ICE PROBLEMS. RADAR TRENDS SUGGEST ORD/MDW
PRECIP MAY END A BIT SOONER THAN PREVIOUSLY EXPECTED THIS
AFTERNOON...AND FCST SOUNDINGS SUGGEST INCOMING COLD AIR WOULD
PRODUCE ONLY A BRIEF PERIOD OF LIGHT FREEZING DRIZZLE AT WORST.
AFTER A BREAK IN PRECIP OVERNIGHT INTO TOMORROW MORNING...THE
NEXT LOW PRESSURE SYSTEM BEGINS AFFECTING THE AREA. AS PRECIP
DEVELOPS TOWARD MIDDAY TOMORROW...AGAIN THE FREEZING LINE WILL LIE
VERY CLOSE TO THE TERMINALS. TAFS REFLECT THE MORE OPTIMISTIC VIEW
THAT ORD/MDW REMAIN ON THE LIQUID SIDE AT LEAST THROUGH THE
AFTERNOON.
IF PRECIP REMAINS MOSTLY LIQUID THEN CIG/VSBY AND WIND TRENDS WILL
BE THE BIGGER ISSUES. AM NOT SEEING MUCH EITHER IN THE
OBSERVATIONS OR IN FCST GUIDANCE TO SUGGEST CIGS WILL IMPROVE
ABOVE IFR THROUGH THE AFTERNOON...AND SOME POSSIBILITY EXISTS FOR
LIFR. VSBYS ARE IN SLIGHTLY BETTER SHAPE.
STILL THINK WINDS WILL BACK TO NORTHWEST BY THIS EVENING THEN
FLUCTUATE BETWEEN NNW AND NNW TONIGHT AND TOMORROW AS THE LOW
PRESSURE SYSTEMS TO OUR SOUTH MIGRATE THROUGH THE AREA.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* LOW CONFIDENCE ABOUT EXACT CIG/VSBY TRENDS THIS AFTERNOON BUT
FAVOR MOSTLY IFR WITH OCCASIONAL LIFR CIGS AND VFR VSBYS.
* WINDS HAVE BEEN STEADY NNE BUT STILL MEDIUM TO HIGH CONFIDENCE
THAT TREND WILL VERY SOON BE MORE NORTHERLY THIS AFTERNOON.
* LOW CONFIDENCE ON HOW LOW CIGS GO OVERNIGHT.
* MEDIUM CONFIDENCE ON TIMING OF PRECIP TOMORROW BUT LOW
CONFIDENCE IN PRECIP TYPE TOMORROW AFTERNOON.
LENNING
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...WINTRY MIX...IFR LIKELY.
SUNDAY...SNOW AND IFR.
MONDAY...CHANCE FOR SNOW...MVFR/IFR POSSIBLE.
TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE SNOW...MVFR POSSIBLE.
THURSDAY...MVFR BECOMING VFR.
MDB
&&
.MARINE...
218 PM...LOW PRESSURE OVER CENTRAL ILLINOIS WILL MOVE NORTHEAST
ACROSS THE EASTERN LAKES TONIGHT AS IT SLOWLY WEAKENS AS WEAK HIGH
PRESSURE OVER THE UPPER MIDWEST IS ABSORBED BY STRONGER HIGH
PRESSURE MOVING ACROSS SOUTHERN CANADA SATURDAY AND SATURDAY
NIGHT. THE GRADIENT WILL SLOWLY WEAKEN TONIGHT WITH SPEEDS IN THE
10-15 KT RANGE BY MORNING. NEW LOW PRESSURE WILL DEVELOP OVER
TEXAS TONIGHT AND MOVE NORTHEAST TO NORTHERN INDIANA BY SUNDAY
MORNING. AS THIS LOW APPROACHES THE LAKES REGION...IT WILL DEEPEN
AND THE GRADIENT WILL TIGHTEN BETWEEN THE STRONGER HIGH ACROSS
SOUTHERN CANADA. NORTHEAST WINDS WILL STEADILY INCREASE SATURDAY
EVENING WITH 30 KTS EXPECTED. DEPENDING ON THE EXACT STRENGTH AND
TRACK OF THIS LOW...ITS POSSIBLE THERE COULD BE A PERIOD OF LOW
END GALES BUT CONFIDENCE IS TOO LOW TO INCLUDE IN THIS FORECAST. A
TROUGH OF LOW PRESSURE WILL THEN LINGER ACROSS THE WESTERN LAKES
REGION SUNDAY NIGHT WITH NORTHERLY WINDS SHIFTING NORTHWESTERLY.
STRONG HIGH PRESSURE WILL BUILD ACROSS THE PLAINS SUNDAY AND
SUNDAY NIGHT AND THEN SHIFT EAST ACROSS THE LAKES REGION MONDAY
NIGHT AND TUESDAY. THERE IS A POTENTIAL FOR A PERIOD OF STRONG
WINDS AHEAD OF THE HIGH...IN THE MONDAY/MONDAY NIGHT TIME PERIOD.
BUT CONFIDENCE REGARDING SPECIFICS DURING THIS TIME PERIOD REMAIN
LOW. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 7 PM FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
DENSE FOG ADVISORY...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 7 PM
FRIDAY.
FLOOD WATCH...ILZ033-ILZ039...NOON SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 7
PM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...NOON SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP TO WILMETTE HARBORS
UNTIL 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM FRIDAY.
&&
$$
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AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
213 PM CST FRI DEC 20 2013
.DISCUSSION...
1155 AM CST
HAVE CONTINUED ALL CURRENT HEADLINES AS IS INTO THIS AFTERNOON.
NO SIGNIFICANT CHANGES ARE AT LEAST PLANNED THIS AFTERNOON FOR THE
WINTER STORM WATCH THAT IS IN EFFECT FOR SATURDAY NIGHT INTO
SUNDAY. HOWEVER...WE CONTINUE TO ANALYZE THE POTENTIAL FOR
FREEZING RAIN TO THE SOUTH OF THE CURRENT WATCH...INCLUDING EVEN
DURING THE DAY SATURDAY. THIS MAY REQUIRE A WINTER WEATHER
HEADLINE.
WATER VAPOR SHOWS SOME RELATIVE DRYING MOVING OVER THE AREA IN
THIS DEEP SOUTHWEST MOIST PLUME AND THAT ALONG WITH JUST LESS
ASCENT IS LIKELY RESPONSIBLE FOR THE DIMINISHING SHOWER COVERAGE.
THIS TREND SHOULD SLOWLY CONTINUE ALTHOUGH PROFILES REMAIN AT
LEAST SUPPORTIVE OF DRIZZLE THROUGH THE AFTERNOON. THE FREEZING
LINE HAS MAINTAINED ITS GROUND THROUGH THE PAST SEVERAL HOURS AND
EXPECT VERY LITTLE CHANGE WITH THAT THROUGH MID AFTERNOON...HENCE
THE PRESERVING OF THE FREEZING RAIN ADVISORY.
WHILE VISIBILITY OBSERVATIONS OF DENSE FOG ARE FAR MORE SPOTTY IN
THE SOUTHERN CWA THAN THEY WERE THIS MORNING...THE SHOWERS HAVE
LIKELY BEEN PARTLY RESPONSIBLE FOR THE SOMEWHAT CHAOTIC VISIBILITY
FIELD. WITH CONTINUED MOISTURE POOLING FROM ADVECTION AND
SNOW SUBLIMATION...ALONG WITH LIGHT WINDS IMMEDIATELY ALONG THE
BOUNDARY...WILL CONTINUE THAT ADVISORY AS IS UNTIL 3 PM.
AS THE SURFACE LOW MOVES INTO NORTH CENTRAL IN BY 4-5 PM...THE
SOMEWHAT DEEPER NORTHERLY FLOW IN THE LOW-LEVELS...ALONG WITH
NIGHTFALL SHOULD ADVANCE THE FREEZING LINE SOUTHWARD. FORCING FOR
PRECIP INTO TONIGHT LOOKS TO BE MAINLY DRIZZLE AS ANY APPRECIABLE
MOISTURE TRANSPORT SHIFTS SOUTHEAST AND THERE IS A LACK OF ANY
REAL SHORT WAVE IMPULSES PRESENTLY FORECAST. SOUNDINGS MARGINALLY
SUPPORTIVE OF DRIZZLE ARE MAINLY INDICATED IN THE SOUTHERN
FORECAST AREA. OVERALL NOT FEELING THAT A HEADLINE WILL BE
NEEDED...AND MORE SO HANDLED WITH AN SPS. IT IS POSSIBLE THE
CURRENT FREEZING RAIN ADVISORY IS EXTENDED UNTIL 6-7 PM TO ACCOUNT
FOR THE LATE AFTERNOON RUSH IF RADAR TRENDS AND REPORTS CONTINUE
TO INDICATE SHOWERS AND DRIZZLE OVER THE SUBFREEZING BOUNDARY
LAYER AS WE NEAR 3 PM.
MTF
//PREV DISCUSSION...
355 AM CST
SEVERAL ISSUES ONGOING THIS MORNING AS WELL THROUGH THE
WEEKEND...WITH DENSE FOG AND FREEZING RAIN ISSUES THIS MORNING
WITH THE FREEZING RAIN NOW LINGERING INTO THE AFTERNOON AND
POSSIBLY TONIGHT...CONTINUED FLOODING CONCERNS...AND LASTLY
POTENTIAL SNOWFALL WHICH THE AXIS OF HEAVIEST SNOW STILL APPEARS
TO BE ACROSS THE NORTH AND NORTHWEST AREAS OF THE CWA.
ADDRESSING THE MORE IMPORTANT ISSUES IN THE NEAR TERM...LIGHT
FREEZING RAIN OR FREEZING DRIZZLE CONTINUES ACROSS THE ADVISORY
AREA THIS MORNING...WITH LIGHT RAIN OR DRIZZLE ONGOING FOR THE
REMAINDER OF THE CWA. BROAD SOUTHWESTERLY FLOW ALOFT CONTINUES TO
USHER SEVERAL WAVES OF ENERGY...WITH ELONGATED TROUGH OF LOW
PRESSURE EXTENDING FROM THE CENTRAL PLAINS UP THROUGH SOUTHERN
GREAT LAKES. AS THESE WAVES OF ENERGY/SPEED MAXES LIFT NORTHEAST
ACROSS THE REGION THIS MORNING...EXPECT THIS TROUGH OF LOW
PRESSURE TO LIFT EAST NORTHEAST TO CENTRAL ILLINOIS AND NORTHWEST
INDIANA THROUGH THE EARLY AFTERNOON. PRESENT LOW/MID LEVEL
CONVERGENCE WILL CONTINUE TO BE A PERSISTENT THROUGH THIS
PERIOD...WITH CURRENT UPSTREAM WAVE TO AID IN TIGHTENING LOW/MID
LEVEL BAROCLINIC ZONE. THIS WILL ENHANCE FRONTOGENETIC FORCING
ACROSS THE ADVISORY AREA...ALL AIDING IN CONTINUED PRECIP
DEVELOPMENT AT LEAST THROUGH EARLY AFTERNOON FOR THE ENTIRE CWA.
HAVE INCREASED POPS THIS MORNING AND EARLY AFTERNOON...BUT WONDER
IF AFTERNOON POPS WILL NEED TO BE RAISED EVEN FURTHER WITH SHORT
TERM GUIDANCE HINTING AT CONTINUED TO DEVELOPMENT EVEN INTO THE
LATE AFTERNOON. ALTHOUGH CURRENT ASSOCIATED BOUNDARY DRAPED ACROSS
EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA DID MAKE SOME
NORTHWARD PROGRESSION EARLY THIS MORNING...FEEL THAT THIS
NORTHWARD MOVEMENT HAS ENDED AND WILL REMAIN SITUATED UNTIL
DROPPING SOUTH/SOUTHEAST OF THE CWA THIS AFTERNOON. GUIDANCE
HINTING AT SOME WEAK CAA TO BEGIN OCCURRING OVER THE NEXT SEVERAL
HOURS AND WITH LATEST RAP ANALYSIS ALREADY INDICATING THIS ACROSS
WESTERN ILLINOIS...FEEL PRETTY CONFIDENT WITH THIS TREND. THIS
WILL HELP TEMPS IN THE ADVISORY AREA TO HOVER JUST BELOW OR AT THE
FREEZING MARK THROUGH MOST OF TODAY. WITH THIS CONTINUED PRECIP
AND TEMP TRENDS...HAVE DECIDED TO EXTEND THE FREEZING RAIN
ADVISORY THROUGH THE AFTERNOON AND HAVE ALSO INCLUDED KANE COUNTY
IN THE ADVISORY AS WELL. WILL NEED TO ALSO MONITOR THE AFTERNOON
PERIOD FOR THE REMAINING CWA...AS COLD ADVECTION SHOULD HELP TEMPS
LOWER AROUND FREEZING INTO THE LATE AFTERNOON PERIOD. WITH PRECIP
POSSIBLY LINGERING...COULD SEE SOME POSSIBLE LIGHT ICING IN AREAS
OUTSIDE OF THE ADVISORY. ALTHOUGH TEMPS SHOULD BE MARGINAL...AND
AM NOT OVERLY CONCERNED AT THIS TIME.
WITH REGARDS TO THE DENSE FOG...WITH INCREASING MOISTURE IN THE
BOUNDARY LAYER THIS PAST EVENING DENSE FOG DEVELOPED ALONG TO THE
NORTH OF THIS BOUNDARY. MANY REPORTS OF DENSE FOR WERE RECEIVED
THIS PAST EVENING ACROSS NORTHWEST INDIANA...PRIMARILY FOR LAKE
AND PORTER COUNTIES IN INDIANA. WITH THE BOUNDARY SITUATED AND
EXPECTED TO REMAIN THIS WAY THROUGH THE REMAINDER OF THE
MORNING...FEEL CURRENT DENSE FOG ADVISORY FOR THESE LOCATIONS
REMAINS VALID. ALTHOUGH...SOUTHERN AREAS OF COOK COUNTY AND
EASTERN AREAS OF WILL COUNTY WILL NEED TO BE MONITORED OVER THE
NEXT COUPLE OF HOURS AS VIS IN THESE LOCATIONS CONTINUES TO BOUNCE
AROUND 1/2 MILE. END TIMING FOR THIS DENSE FOG ADVISORY REMAINS 9
AM CST...AND SEEMS REASONABLE. THIS SAGGING BOUNDARY AND SLIGHTLY
DRIER AIR SHOULD HELP WITH THE MORE DENSE FOG...BUT WITH PATCHY
DENSE FOG STILL NOT OUT OF THE QUESTION AT LEAST THROUGH MID DAY.
CONFIDENCE WITH THIS FOG REMAINS LOW AT THIS TIME AND WILL NEED TO
MONITOR...POSSIBLY EXTENDING THIS ADVISORY OR MAYBE EVEN EXPANDING
IT LATER THIS MORNING.
WITH SURFACE LOW EXITING TO THE EAST THIS EVENING AND THE ARRIVAL
OF DRIER AIR...SHOULD OBSERVE OVERALL PRECIP CHANCES TO WIND DOWN
FOR THE TIME BEING. ALTHOUGH WITH GUIDANCE CONTINUING TO INDICATE
BROAD SCALE LIFT WITH THE APPROACHING LONGWAVE TROUGH TO THE WEST
IT DOES APPEAR AS IF AREAS ACROSS THE SOUTHERN CWA COULD SEE
ADDITIONAL PRECIP TONIGHT. ALTHOUGH LIGHT PRECIP...THERMAL
PROFILES WOULD INDICATE THAT THIS PRECIP WOULD BE IN THE FORM OF
LIGHT FREEZING RAIN OR LIGHT FREEZING DRIZZLE. ANOTHER PERIOD I AM
CONCERNED ABOUT AT THIS TIME IS LATE TONIGHT INTO EARLY SATURDAY
MORNING...ONCE AGAIN FOR AREAS ACROSS THE SOUTHERN CWA. WILL NEED
TO MONITOR SURFACE TEMP TRENDS ACROSS EAST CENTRAL ILLINOIS DURING
THIS TIME...WITH FREEZING RAIN ONCE AGAIN POSSIBLY BEING AN ISSUE.
EXPANDING PRECIP TO THE SOUTH IS EXPECTED TO INCH FURTHER NORTH
TOWARDS THE SOUTHERN CWA TOWARDS THE 12Z SATURDAY TIME
FRAME...WITH SOUTHWEST FLOW ALOFT PERSISTING OUT AHEAD OF THE
APPROACHING LONGWAVE TROUGH. WITH A SLOW TEMP TREND EXPECTED
SATURDAY MORNING...A PERIOD OF LIGHT FREEZING RAIN COULD CAUSE
SOME ISSUES PRIMARILY SOUTH OF I-80.
WITH REGARDS TO WINTER STORM SATURDAY THROUGH SUNDAY...LATEST
THINKING/UPDATES TO FORECAST CONTINUE TO SUPPORT CURRENT WINTER
STORM WATCH ACROSS NORTHERN PORTIONS OF THE CWA. EXPECTED VARYING
PRECIP TYPES INCLUDING ALMOST ALL WINTER PRECIP TYPES COULD BE
OBSERVED SATURDAY INTO SATURDAY NIGHT...WITH A VARYING THERMAL
PROFILE EXPECTED TO CHANGE THROUGH THE PERIOD FOR ALL AREAS. WILL
NEED TO MONITOR THE SATURDAY MORNING TIME FRAME INTO THE DAY
SATURDAY FOR THE VARYING PRECIP TYPE...POSSIBLY ADDING YET ANOTHER
HEADLINE TO ACCOMMODATE FOR THE WINTRY MIX. EXPECTED SURFACE LOW
TRACK STILL SUPPORTIVE FOR BEST CHANCES FOR SNOW OR ALL SNOW
ACROSS NORTHWEST AND NORTH CENTRAL ILLINOIS WITH SNOWFALL TOTALS
IN EXCESS OF 6 INCHES STILL APPEARING POSSIBLE. THE EXPECTED RAIN
SNOW LINE HAS VARIED SLIGHTLY...BUT THE GENERAL IDEA REMAINING THE
SAME. OHARE TO PERU ILLINOIS LINE ARE THE DIVIDING LINE AT THIS
TIME...WITH CURRENT SNOW FORECAST INDICATING RAPID INCREASE IN
SNOW AMOUNTS RIGHT TO THE NORTH OF THIS LINE AND WITH AREAS TO THE
SOUTH OBSERVING LIGHT SNOW ACCUMULATIONS.
ALTHOUGH LATEST TRENDS ARE INDICATING THAT THE AXIS OF HEAVIEST
RAINFALL IS BEGINNING TO SHIFT SOUTH OF THE CWA...DECENT RAINFALL
AMOUNTS OF UP TO AN INCH STILL SUPPORT THE POSSIBILITY OF
FLOODING...AND HAVE MADE NO CHANGES TO THE CURRENT FLOOD WATCH.
RODRIGUEZ
MEDIUM AND LONG RANGE...MONDAY THROUGH THURSDAY...
MAIN CONCERNS BEYOND THIS WEEKEND ARE THE RETURN OF ARCTIC AIR AND
MUCH COLDER TEMPERATURES MONDAY-TUESDAY...AND THE POTENTIAL FOR A
LITTLE LIGHT SNOW CHRISTMAS EVE-CHRISTMAS DAY.
DEEP UPPER TROUGH TRAVERSING THE REGION MONDAY WITH FAIRLY
IMPRESSIVE SHORT WAVE ENERGY PASSING OVERHEAD. FORECAST SOUNDINGS
INDICATE SATURATION IN LOW LEVELS...WITH TEMPS NEAR -15C AS BOUNDARY
LAYER COOLS IN BLUSTERY COLD ADVECTION BEHIND DEPARTING WEEKEND LOW
PRESSURE SYSTEM. THIS SHOULD SUPPORT FLURRIES/LIGHT SNOW SHOWERS
ACROSS THE CWA INTO THE AFTERNOON HOURS. OF MORE IMPORTANCE THAN THE
POTENTIAL FOR LIGHT SNOW SHOWERS OR FLURRIES HOWEVER WILL BE THE
MUCH COLDER TEMPS AND WIND CHILLS AS ARCTIC AIR PLUNGES BACK INTO
THE REGION. TEMPS AT H8 FALL TO AROUND -16 C BY LATE AFTERNOON WITH
H9 TEMPS NEARLY SO...SUGGESTING SURFACE TEMPS MAY STRUGGLE TO RISE
ABOVE 10-15F AND WILL LIKELY FALL INTO THE SINGLE DIGITS ACROSS
NORTH CENTRAL IL AND WIND CHILLS IN THE NEGATIVE SINGLE DIGITS.
SURFACE HIGH PRESSURE RIDGE WILL BUILD ACROSS THE MISSISSIPPI VALLEY
AND INTO IL MONDAY NIGHT IN RESPONSE TO SUBSIDENCE BEHIND THE
DEPARTING UPPER TROUGH...WITH CLEARING SKIES...NEW SNOW COVER
ESPECIALLY FAR NORTHERN IL...AND DECREASING WINDS EXPECTED TO RESULT
IN STRONG RADIATIONAL COOLING. BOTH GFS AND ECMWF MOS DEPICT
SUB-ZERO LOWS ACROSS MUCH OF NORTHERN IL BY SUNRISE TUESDAY. SURFACE
HIGH PRESSURE RIDGE MOVES ACROSS THE AREA DURING THE DAY TUESDAY...
WITH WINDS BACKING TO THE SOUTH-SOUTHEAST DURING THE AFTERNOON AS
WARM ADVECTION DEVELOPS (ALOFT AT LEAST) IN ADVANCE OF A SHORT WAVE
EMERGING FROM THE PLAINS. MODERATION IN TEMPS LIMITED AT THE SURFACE
HOWEVER WITH VERY COLD START TO DAY AND STRONG INVERSION LIMITING
WARMING AT THE SURFACE WITH HIGHS IN THE TEENS/LOW 20S.
LONG RANGE GUIDANCE SIMILAR IN BRINGING SHORT WAVE TROUGH ACROSS
THE REGION DURING THE TUESDAY NIGHT/WEDNESDAY PERIOD AND ANOTHER
WEDNESDAY NIGHT/THURSDAY...THOUGH DIFFERENCES DO EXIST WITH
AMPLITUDE OF THESE INDIVIDUAL WAVES AND ASSOCIATED SURFACE
REFLECTIONS. THE ECMWF IS STRONGER/MORE AMPLIFIED WITH BOTH...
THOUGH AT THIS DISTANCE HAVE FOCUSED MAINLY ON SIMILARITIES BETWEEN
GUIDANCE. THIS YIELDS A LITTLE TEMPERATURE MODERATION CHRISTMAS EVE
AND CHRISTMAS DAY WITH A CHANCE OF SOME LIGHT SNOW...PERHAPS
0.5-1.0" BASED ON ROUGH QPF OUTPUT. LIGHT SNOW MAY LINGER ACROSS
THE EASTERN CWA CHRISTMAS NIGHT INTO THURSDAY WITH SURFACE COLD
FRONTAL TROUGH. AS MENTIONED...BRIEF MODERATION PRODUCES HIGHS IN
THE 20S/AROUND 30 FOR CHRISTMAS DAY THEN COLDER AIR LOOKS TO RETURN
THURSDAY BEHIND THE FRONT WITH TEMPS IN THE TEENS/LOW 20S.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* ONGOING IFR CIG/VSBY TRENDS.
* PRECIPITATION ENDING TIME AND POSSIBLE LIGHT FREEZING RAIN TODAY.
* WINDS BACKING NORTH THEN NORTHWEST.
LENNING
//DISCUSSION...UPDATED 18Z...
SO FAR AT MDW/ORD/GYY THE TEMPERATURES HAVE REMAINED ENOUGH ABOVE
FREEZING THAT ICE AT THE SFC HAS NOT BEEN A PROBLEM. DPA HAS BEEN
RIGHT ON THE LINE BUT STILL ABOVE FREEZING...WHILE RFD HAS BEEN
HAVING CONSIDERABLE ICE PROBLEMS. RADAR TRENDS SUGGEST ORD/MDW
PRECIP MAY END A BIT SOONER THAN PREVIOUSLY EXPECTED THIS
AFTERNOON...AND FCST SOUNDINGS SUGGEST INCOMING COLD AIR WOULD
PRODUCE ONLY A BRIEF PERIOD OF LIGHT FREEZING DRIZZLE AT WORST.
AFTER A BREAK IN PRECIP OVERNIGHT INTO TOMORROW MORNING...THE
NEXT LOW PRESSURE SYSTEM BEGINS AFFECTING THE AREA. AS PRECIP
DEVELOPS TOWARD MIDDAY TOMORROW...AGAIN THE FREEZING LINE WILL LIE
VERY CLOSE TO THE TERMINALS. TAFS REFLECT THE MORE OPTIMISTIC VIEW
THAT ORD/MDW REMAIN ON THE LIQUID SIDE AT LEAST THROUGH THE
AFTERNOON.
IF PRECIP REMAINS MOSTLY LIQUID THEN CIG/VSBY AND WIND TRENDS WILL
BE THE BIGGER ISSUES. AM NOT SEEING MUCH EITHER IN THE
OBSERVATIONS OR IN FCST GUIDANCE TO SUGGEST CIGS WILL IMPROVE
ABOVE IFR THROUGH THE AFTERNOON...AND SOME POSSIBILITY EXISTS FOR
LIFR. VSBYS ARE IN SLIGHTLY BETTER SHAPE.
STILL THINK WINDS WILL BACK TO NORTHWEST BY THIS EVENING THEN
FLUCTUATE BETWEEN NNW AND NNW TONIGHT AND TOMORROW AS THE LOW
PRESSURE SYSTEMS TO OUR SOUTH MIGRATE THROUGH THE AREA.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* LOW CONFIDENCE ABOUT EXACT CIG/VSBY TRENDS THIS AFTERNOON BUT
FAVOR MOSTLY IFR WITH OCCASIONAL LIFR CIGS AND VFR VSBYS.
* WINDS HAVE BEEN STEADY NNE BUT STILL MEDIUM TO HIGH CONFIDENCE
THAT TREND WILL VERY SOON BE MORE NORTHERLY THIS AFTERNOON.
* LOW CONFIDENCE ON HOW LOW CIGS GO OVERNIGHT.
* MEDIUM CONFIDENCE ON TIMING OF PRECIP TOMORROW BUT LOW
CONFIDENCE IN PRECIP TYPE TOMORROW AFTERNOON.
LENNING
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...WINTRY MIX...IFR LIKELY.
SUNDAY...SNOW AND IFR.
MONDAY...CHANCE FOR SNOW...MVFR/IFR POSSIBLE.
TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE SNOW...MVFR POSSIBLE.
THURSDAY...MVFR BECOMING VFR.
MDB
&&
.MARINE...
301 AM CST
LOW PRESSURE CENTERED OVER NORTH-CENTRAL OKLAHOMA WILL TRACK
NORTHEAST ALONG A FRONTAL BOUNDARY WHICH EXTENDS NORTHEAST INTO
NORTHERN INDIANA AND EASTWARD ACROSS LAKE ERIE AND ONTARIO.
MEANWHILE HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE LITTLE
THROUGH THE DAY. THE STRONGEST PRESSURE GRADIENT IS STARTING TO SET
UP EARLY THIS MORNING AND WILL LIKELY RESULT IN AN INCREASE IN
NORTHEAST WINDS ACROSS MUCH OF THE LAKE THROUGH MID MORNING BEFORE
THE PRESSURE GRADIENT EASES. SPEEDS MAY PUSH 30 KT FOR A TIME
THROUGH MID OR LATE MORNING...ESPECIALLY ACROSS CENTRAL SECTIONS OF
THE LAKE. THE LOW WILL PASS SOUTH OF THE LAKE LATER THIS AFTERNOON
AND BEGIN TO WEAKEN WITH THE HIGH WEAKENING AS WELL. ANOTHER SURFACE
LOW WILL DEVELOP OVER THE ARKLATEX SATURDAY AND LIFT NORTHEAST TO
NORTHERN OHIO BY SUNDAY AFTERNOON. A VERY STRONG HIGH WILL THEN
DEVELOP SOUTHWARD INTO THE NORTHERN PLAINS AS THE LOW MOVES INTO NEW
ENGLAND SUNDAY NIGHT. THIS WILL LEAVE LAKE MICHIGAN IN THE PRESSURE
GRADIENT BETWEEN THE TWO SYSTEMS SATURDAY NIGHT AND SUNDAY WITH
COLDER AIR SPILLING ACROSS THE LAKE AS WELL. THIS WILL SET THE STAGE
FOR ANOTHER ROUND OF STRONG WINDS WHICH WILL START OUT NORTHEAST
THEN SHIFT NORTH-NORTHWEST AND EASE UP LATE SUNDAY AFTERNOON. THE
HIGH WILL PASS SOUTH OF THE LAKE TUESDAY BEFORE LOW PRESSURE TRACKS
SOUTHEAST ACROSS THE CANADIAN PRAIRIES AND NORTHERN PLAINS. THIS
SHOULD LEAD TO ANOTHER PERIOD OF INCREASED WINDS...THIS TIME FROM
THE SOUTH AND SOUTHWEST WEDNESDAY. WILL KEEP SPEEDS BELOW GALE FORCE
THROUGH THE PERIOD BUT WILL NEED TO MONITOR FOR SHORT WINDOWS OF
GALE FORCE WINDS SATURDAY NIGHT AND SUNDAY MORNING...AND AGAIN EARLY
WEDNESDAY.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 7 PM FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
DENSE FOG ADVISORY...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 7 PM
FRIDAY.
FLOOD WATCH...ILZ033-ILZ039...NOON SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 7
PM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...NOON SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM FRIDAY.
&&
$$
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AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1158 AM CST FRI DEC 20 2013
.DISCUSSION...
1155 AM CST
HAVE CONTINUED ALL CURRENT HEADLINES AS IS INTO THIS AFTERNOON.
NO SIGNIFICANT CHANGES ARE AT LEAST PLANNED THIS AFTERNOON FOR THE
WINTER STORM WATCH THAT IS IN EFFECT FOR SATURDAY NIGHT INTO
SUNDAY. HOWEVER...WE CONTINUE TO ANALYZE THE POTENTIAL FOR
FREEZING RAIN TO THE SOUTH OF THE CURRENT WATCH...INCLUDING EVEN
DURING THE DAY SATURDAY. THIS MAY REQUIRE A WINTER WEATHER
HEADLINE.
WATER VAPOR SHOWS SOME RELATIVE DRYING MOVING OVER THE AREA IN
THIS DEEP SOUTHWEST MOIST PLUME AND THAT ALONG WITH JUST LESS
ASCENT IS LIKELY RESPONSIBLE FOR THE DIMINISHING SHOWER COVERAGE.
THIS TREND SHOULD SLOWLY CONTINUE ALTHOUGH PROFILES REMAIN AT
LEAST SUPPORTIVE OF DRIZZLE THROUGH THE AFTERNOON. THE FREEZING
LINE HAS MAINTAINED ITS GROUND THROUGH THE PAST SEVERAL HOURS AND
EXPECT VERY LITTLE CHANGE WITH THAT THROUGH MID AFTERNOON...HENCE
THE PRESERVING OF THE FREEZING RAIN ADVISORY.
WHILE VISIBILITY OBSERVATIONS OF DENSE FOG ARE FAR MORE SPOTTY IN
THE SOUTHERN CWA THAN THEY WERE THIS MORNING...THE SHOWERS HAVE
LIKELY BEEN PARTLY RESPONSIBLE FOR THE SOMEWHAT CHAOTIC VISIBILITY
FIELD. WITH CONTINUED MOISTURE POOLING FROM ADVECTION AND
SNOW SUBLIMATION...ALONG WITH LIGHT WINDS IMMEDIATELY ALONG THE
BOUNDARY...WILL CONTINUE THAT ADVISORY AS IS UNTIL 3 PM.
AS THE SURFACE LOW MOVES INTO NORTH CENTRAL IN BY 4-5 PM...THE
SOMEWHAT DEEPER NORTHERLY FLOW IN THE LOW-LEVELS...ALONG WITH
NIGHTFALL SHOULD ADVANCE THE FREEZING LINE SOUTHWARD. FORCING FOR
PRECIP INTO TONIGHT LOOKS TO BE MAINLY DRIZZLE AS ANY APPRECIABLE
MOISTURE TRANSPORT SHIFTS SOUTHEAST AND THERE IS A LACK OF ANY
REAL SHORT WAVE IMPULSES PRESENTLY FORECAST. SOUNDINGS MARGINALLY
SUPPORTIVE OF DRIZZLE ARE MAINLY INDICATED IN THE SOUTHERN
FORECAST AREA. OVERALL NOT FEELING THAT A HEADLINE WILL BE
NEEDED...AND MORE SO HANDLED WITH AN SPS. IT IS POSSIBLE THE
CURRENT FREEZING RAIN ADVISORY IS EXTENDED UNTIL 6-7 PM TO ACCOUNT
FOR THE LATE AFTERNOON RUSH IF RADAR TRENDS AND REPORTS CONTINUE
TO INDICATE SHOWERS AND DRIZZLE OVER THE SUBFREEZING BOUNDARY
LAYER AS WE NEAR 3 PM.
MTF
//PREV DISCUSSION...
355 AM CST
SEVERAL ISSUES ONGOING THIS MORNING AS WELL THROUGH THE
WEEKEND...WITH DENSE FOG AND FREEZING RAIN ISSUES THIS MORNING
WITH THE FREEZING RAIN NOW LINGERING INTO THE AFTERNOON AND
POSSIBLY TONIGHT...CONTINUED FLOODING CONCERNS...AND LASTLY
POTENTIAL SNOWFALL WHICH THE AXIS OF HEAVIEST SNOW STILL APPEARS
TO BE ACROSS THE NORTH AND NORTHWEST AREAS OF THE CWA.
ADDRESSING THE MORE IMPORTANT ISSUES IN THE NEAR TERM...LIGHT
FREEZING RAIN OR FREEZING DRIZZLE CONTINUES ACROSS THE ADVISORY
AREA THIS MORNING...WITH LIGHT RAIN OR DRIZZLE ONGOING FOR THE
REMAINDER OF THE CWA. BROAD SOUTHWESTERLY FLOW ALOFT CONTINUES TO
USHER SEVERAL WAVES OF ENERGY...WITH ELONGATED TROUGH OF LOW
PRESSURE EXTENDING FROM THE CENTRAL PLAINS UP THROUGH SOUTHERN
GREAT LAKES. AS THESE WAVES OF ENERGY/SPEED MAXES LIFT NORTHEAST
ACROSS THE REGION THIS MORNING...EXPECT THIS TROUGH OF LOW
PRESSURE TO LIFT EAST NORTHEAST TO CENTRAL ILLINOIS AND NORTHWEST
INDIANA THROUGH THE EARLY AFTERNOON. PRESENT LOW/MID LEVEL
CONVERGENCE WILL CONTINUE TO BE A PERSISTENT THROUGH THIS
PERIOD...WITH CURRENT UPSTREAM WAVE TO AID IN TIGHTENING LOW/MID
LEVEL BAROCLINIC ZONE. THIS WILL ENHANCE FRONTOGENETIC FORCING
ACROSS THE ADVISORY AREA...ALL AIDING IN CONTINUED PRECIP
DEVELOPMENT AT LEAST THROUGH EARLY AFTERNOON FOR THE ENTIRE CWA.
HAVE INCREASED POPS THIS MORNING AND EARLY AFTERNOON...BUT WONDER
IF AFTERNOON POPS WILL NEED TO BE RAISED EVEN FURTHER WITH SHORT
TERM GUIDANCE HINTING AT CONTINUED TO DEVELOPMENT EVEN INTO THE
LATE AFTERNOON. ALTHOUGH CURRENT ASSOCIATED BOUNDARY DRAPED ACROSS
EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA DID MAKE SOME
NORTHWARD PROGRESSION EARLY THIS MORNING...FEEL THAT THIS
NORTHWARD MOVEMENT HAS ENDED AND WILL REMAIN SITUATED UNTIL
DROPPING SOUTH/SOUTHEAST OF THE CWA THIS AFTERNOON. GUIDANCE
HINTING AT SOME WEAK CAA TO BEGIN OCCURRING OVER THE NEXT SEVERAL
HOURS AND WITH LATEST RAP ANALYSIS ALREADY INDICATING THIS ACROSS
WESTERN ILLINOIS...FEEL PRETTY CONFIDENT WITH THIS TREND. THIS
WILL HELP TEMPS IN THE ADVISORY AREA TO HOVER JUST BELOW OR AT THE
FREEZING MARK THROUGH MOST OF TODAY. WITH THIS CONTINUED PRECIP
AND TEMP TRENDS...HAVE DECIDED TO EXTEND THE FREEZING RAIN
ADVISORY THROUGH THE AFTERNOON AND HAVE ALSO INCLUDED KANE COUNTY
IN THE ADVISORY AS WELL. WILL NEED TO ALSO MONITOR THE AFTERNOON
PERIOD FOR THE REMAINING CWA...AS COLD ADVECTION SHOULD HELP TEMPS
LOWER AROUND FREEZING INTO THE LATE AFTERNOON PERIOD. WITH PRECIP
POSSIBLY LINGERING...COULD SEE SOME POSSIBLE LIGHT ICING IN AREAS
OUTSIDE OF THE ADVISORY. ALTHOUGH TEMPS SHOULD BE MARGINAL...AND
AM NOT OVERLY CONCERNED AT THIS TIME.
WITH REGARDS TO THE DENSE FOG...WITH INCREASING MOISTURE IN THE
BOUNDARY LAYER THIS PAST EVENING DENSE FOG DEVELOPED ALONG TO THE
NORTH OF THIS BOUNDARY. MANY REPORTS OF DENSE FOR WERE RECEIVED
THIS PAST EVENING ACROSS NORTHWEST INDIANA...PRIMARILY FOR LAKE
AND PORTER COUNTIES IN INDIANA. WITH THE BOUNDARY SITUATED AND
EXPECTED TO REMAIN THIS WAY THROUGH THE REMAINDER OF THE
MORNING...FEEL CURRENT DENSE FOG ADVISORY FOR THESE LOCATIONS
REMAINS VALID. ALTHOUGH...SOUTHERN AREAS OF COOK COUNTY AND
EASTERN AREAS OF WILL COUNTY WILL NEED TO BE MONITORED OVER THE
NEXT COUPLE OF HOURS AS VIS IN THESE LOCATIONS CONTINUES TO BOUNCE
AROUND 1/2 MILE. END TIMING FOR THIS DENSE FOG ADVISORY REMAINS 9
AM CST...AND SEEMS REASONABLE. THIS SAGGING BOUNDARY AND SLIGHTLY
DRIER AIR SHOULD HELP WITH THE MORE DENSE FOG...BUT WITH PATCHY
DENSE FOG STILL NOT OUT OF THE QUESTION AT LEAST THROUGH MID DAY.
CONFIDENCE WITH THIS FOG REMAINS LOW AT THIS TIME AND WILL NEED TO
MONITOR...POSSIBLY EXTENDING THIS ADVISORY OR MAYBE EVEN EXPANDING
IT LATER THIS MORNING.
WITH SURFACE LOW EXITING TO THE EAST THIS EVENING AND THE ARRIVAL
OF DRIER AIR...SHOULD OBSERVE OVERALL PRECIP CHANCES TO WIND DOWN
FOR THE TIME BEING. ALTHOUGH WITH GUIDANCE CONTINUING TO INDICATE
BROAD SCALE LIFT WITH THE APPROACHING LONGWAVE TROUGH TO THE WEST
IT DOES APPEAR AS IF AREAS ACROSS THE SOUTHERN CWA COULD SEE
ADDITIONAL PRECIP TONIGHT. ALTHOUGH LIGHT PRECIP...THERMAL
PROFILES WOULD INDICATE THAT THIS PRECIP WOULD BE IN THE FORM OF
LIGHT FREEZING RAIN OR LIGHT FREEZING DRIZZLE. ANOTHER PERIOD I AM
CONCERNED ABOUT AT THIS TIME IS LATE TONIGHT INTO EARLY SATURDAY
MORNING...ONCE AGAIN FOR AREAS ACROSS THE SOUTHERN CWA. WILL NEED
TO MONITOR SURFACE TEMP TRENDS ACROSS EAST CENTRAL ILLINOIS DURING
THIS TIME...WITH FREEZING RAIN ONCE AGAIN POSSIBLY BEING AN ISSUE.
EXPANDING PRECIP TO THE SOUTH IS EXPECTED TO INCH FURTHER NORTH
TOWARDS THE SOUTHERN CWA TOWARDS THE 12Z SATURDAY TIME
FRAME...WITH SOUTHWEST FLOW ALOFT PERSISTING OUT AHEAD OF THE
APPROACHING LONGWAVE TROUGH. WITH A SLOW TEMP TREND EXPECTED
SATURDAY MORNING...A PERIOD OF LIGHT FREEZING RAIN COULD CAUSE
SOME ISSUES PRIMARILY SOUTH OF I-80.
WITH REGARDS TO WINTER STORM SATURDAY THROUGH SUNDAY...LATEST
THINKING/UPDATES TO FORECAST CONTINUE TO SUPPORT CURRENT WINTER
STORM WATCH ACROSS NORTHERN PORTIONS OF THE CWA. EXPECTED VARYING
PRECIP TYPES INCLUDING ALMOST ALL WINTER PRECIP TYPES COULD BE
OBSERVED SATURDAY INTO SATURDAY NIGHT...WITH A VARYING THERMAL
PROFILE EXPECTED TO CHANGE THROUGH THE PERIOD FOR ALL AREAS. WILL
NEED TO MONITOR THE SATURDAY MORNING TIME FRAME INTO THE DAY
SATURDAY FOR THE VARYING PRECIP TYPE...POSSIBLY ADDING YET ANOTHER
HEADLINE TO ACCOMMODATE FOR THE WINTRY MIX. EXPECTED SURFACE LOW
TRACK STILL SUPPORTIVE FOR BEST CHANCES FOR SNOW OR ALL SNOW
ACROSS NORTHWEST AND NORTH CENTRAL ILLINOIS WITH SNOWFALL TOTALS
IN EXCESS OF 6 INCHES STILL APPEARING POSSIBLE. THE EXPECTED RAIN
SNOW LINE HAS VARIED SLIGHTLY...BUT THE GENERAL IDEA REMAINING THE
SAME. OHARE TO PERU ILLINOIS LINE ARE THE DIVIDING LINE AT THIS
TIME...WITH CURRENT SNOW FORECAST INDICATING RAPID INCREASE IN
SNOW AMOUNTS RIGHT TO THE NORTH OF THIS LINE AND WITH AREAS TO THE
SOUTH OBSERVING LIGHT SNOW ACCUMULATIONS.
ALTHOUGH LATEST TRENDS ARE INDICATING THAT THE AXIS OF HEAVIEST
RAINFALL IS BEGINNING TO SHIFT SOUTH OF THE CWA...DECENT RAINFALL
AMOUNTS OF UP TO AN INCH STILL SUPPORT THE POSSIBILITY OF
FLOODING...AND HAVE MADE NO CHANGES TO THE CURRENT FLOOD WATCH.
RODRIGUEZ
MEDIUM AND LONG RANGE...MONDAY THROUGH THURSDAY...
MAIN CONCERNS BEYOND THIS WEEKEND ARE THE RETURN OF ARCTIC AIR AND
MUCH COLDER TEMPERATURES MONDAY-TUESDAY...AND THE POTENTIAL FOR A
LITTLE LIGHT SNOW CHRISTMAS EVE-CHRISTMAS DAY.
DEEP UPPER TROUGH TRAVERSING THE REGION MONDAY WITH FAIRLY
IMPRESSIVE SHORT WAVE ENERGY PASSING OVERHEAD. FORECAST SOUNDINGS
INDICATE SATURATION IN LOW LEVELS...WITH TEMPS NEAR -15C AS BOUNDARY
LAYER COOLS IN BLUSTERY COLD ADVECTION BEHIND DEPARTING WEEKEND LOW
PRESSURE SYSTEM. THIS SHOULD SUPPORT FLURRIES/LIGHT SNOW SHOWERS
ACROSS THE CWA INTO THE AFTERNOON HOURS. OF MORE IMPORTANCE THAN THE
POTENTIAL FOR LIGHT SNOW SHOWERS OR FLURRIES HOWEVER WILL BE THE
MUCH COLDER TEMPS AND WIND CHILLS AS ARCTIC AIR PLUNGES BACK INTO
THE REGION. TEMPS AT H8 FALL TO AROUND -16 C BY LATE AFTERNOON WITH
H9 TEMPS NEARLY SO...SUGGESTING SURFACE TEMPS MAY STRUGGLE TO RISE
ABOVE 10-15F AND WILL LIKELY FALL INTO THE SINGLE DIGITS ACROSS
NORTH CENTRAL IL AND WIND CHILLS IN THE NEGATIVE SINGLE DIGITS.
SURFACE HIGH PRESSURE RIDGE WILL BUILD ACROSS THE MISSISSIPPI VALLEY
AND INTO IL MONDAY NIGHT IN RESPONSE TO SUBSIDENCE BEHIND THE
DEPARTING UPPER TROUGH...WITH CLEARING SKIES...NEW SNOW COVER
ESPECIALLY FAR NORTHERN IL...AND DECREASING WINDS EXPECTED TO RESULT
IN STRONG RADIATIONAL COOLING. BOTH GFS AND ECMWF MOS DEPICT
SUB-ZERO LOWS ACROSS MUCH OF NORTHERN IL BY SUNRISE TUESDAY. SURFACE
HIGH PRESSURE RIDGE MOVES ACROSS THE AREA DURING THE DAY TUESDAY...
WITH WINDS BACKING TO THE SOUTH-SOUTHEAST DURING THE AFTERNOON AS
WARM ADVECTION DEVELOPS (ALOFT AT LEAST) IN ADVANCE OF A SHORT WAVE
EMERGING FROM THE PLAINS. MODERATION IN TEMPS LIMITED AT THE SURFACE
HOWEVER WITH VERY COLD START TO DAY AND STRONG INVERSION LIMITING
WARMING AT THE SURFACE WITH HIGHS IN THE TEENS/LOW 20S.
LONG RANGE GUIDANCE SIMILAR IN BRINGING SHORT WAVE TROUGH ACROSS
THE REGION DURING THE TUESDAY NIGHT/WEDNESDAY PERIOD AND ANOTHER
WEDNESDAY NIGHT/THURSDAY...THOUGH DIFFERENCES DO EXIST WITH
AMPLITUDE OF THESE INDIVIDUAL WAVES AND ASSOCIATED SURFACE
REFLECTIONS. THE ECMWF IS STRONGER/MORE AMPLIFIED WITH BOTH...
THOUGH AT THIS DISTANCE HAVE FOCUSED MAINLY ON SIMILARITIES BETWEEN
GUIDANCE. THIS YIELDS A LITTLE TEMPERATURE MODERATION CHRISTMAS EVE
AND CHRISTMAS DAY WITH A CHANCE OF SOME LIGHT SNOW...PERHAPS
0.5-1.0" BASED ON ROUGH QPF OUTPUT. LIGHT SNOW MAY LINGER ACROSS
THE EASTERN CWA CHRISTMAS NIGHT INTO THURSDAY WITH SURFACE COLD
FRONTAL TROUGH. AS MENTIONED...BRIEF MODERATION PRODUCES HIGHS IN
THE 20S/AROUND 30 FOR CHRISTMAS DAY THEN COLDER AIR LOOKS TO RETURN
THURSDAY BEHIND THE FRONT WITH TEMPS IN THE TEENS/LOW 20S.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* IFR CIG/VSBY TRENDS.
* PRECIPITATION ENDING TIME AND POSSIBLE LIGHT FREEZING RAIN TODAY.
* WINDS BACKING NORTH THEN NORTHWEST.
LENNING
//DISCUSSION...UPDATED 18Z...
SO FAR AT MDW/ORD/GYY THE TEMPERATURES HAVE REMAINED ENOUGH ABOVE
FREEZING THAT ICE AT THE SFC HAS NOT BEEN A PROBLEM. DPA HAS BEEN
RIGHT ON THE LINE BUT STILL ABOVE FREEZING...WHILE RFD HAS BEEN
HAVING CONSIDERABLE ICE PROBLEMS. RADAR TRENDS SUGGEST ORD/MDW
PRECIP MAY END A BIT SOONER THAN PREVIOUSLY EXPECTED THIS
AFTERNOON...AND FCST SOUNDINGS SUGGEST INCOMING COLD AIR WOULD
PRODUCE ONLY A BRIEF PERIOD OF LIGHT FREEZING DRIZZLE AT WORST.
AFTER A BREAK IN PRECIP OVERNIGHT INTO TOMORROW MORNING...THE
NEXT LOW PRESSURE SYSTEM BEGINS AFFECTING THE AREA. AS PRECIP
DEVELOPS TOWARD MIDDAY TOMORROW...AGAIN THE FREEZING LINE WILL LIE
VERY CLOSE TO THE TERMINALS. TAFS REFLECT THE MORE OPTIMISTIC VIEW
THAT ORD/MDW REMAIN ON THE LIQUID SIDE AT LEAST THROUGH THE
AFTERNOON.
IF PRECIP REMAINS MOSTLY LIQUID THEN CIG/VSBY AND WIND TRENDS WILL
BE THE BIGGER ISSUES. AM NOT SEEING MUCH EITHER IN THE
OBSERVATIONS OR IN FCST GUIDANCE TO SUGGEST CIGS WILL IMPROVE
ABOVE IFR THROUGH THE AFTERNOON...AND SOME POSSIBILITY EXISTS FOR
LIFR. VSBYS ARE IN SLIGHTLY BETTER SHAPE.
STILL THINK WINDS WILL BACK TO NORTHWEST BY THIS EVENING THEN
FLUCTUATE BETWEEN NNW AND NNW TONIGHT AND TOMORROW AS THE LOW
PRESSURE SYSTEMS TO OUR SOUTH MIGRATE THROUGH THE AREA.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE IN IFR CIGS CONTINUING. LOW CONFIDENCE IN HOW
THEY CHANGE AFTER PRECIP ENDS THIS AFTERNOON.
* HIGH CONFIDENCE IN MVFR OR BETTER VSBY TODAY. LOW CONFIDENCE IT
REMAINS VFR AS IN LATEST OBS.
* HIGH CONFIDENCE IN WIND BACKING TO NORTHWEST...MEDIUM CONFIDENCE
ON TIMING.
* HIGH CONFIDENCE IN LIGHT RAIN/DRIZZLE CONTINUING THROUGH EARLY
AFTERNOON. LOW CONFIDENCE IN POTENTIAL FOR -FZRA/FZDZ THIS
AFTERNOON.
LENNING
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...WINTRY MIX...IFR LIKELY.
SUNDAY...SNOW AND IFR.
MONDAY...CHANCE FOR SNOW...MVFR/IFR POSSIBLE.
TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE SNOW...MVFR POSSIBLE.
THURSDAY...MVFR BECOMING VFR.
MDB
&&
.MARINE...
301 AM CST
LOW PRESSURE CENTERED OVER NORTH-CENTRAL OKLAHOMA WILL TRACK
NORTHEAST ALONG A FRONTAL BOUNDARY WHICH EXTENDS NORTHEAST INTO
NORTHERN INDIANA AND EASTWARD ACROSS LAKE ERIE AND ONTARIO.
MEANWHILE HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE LITTLE
THROUGH THE DAY. THE STRONGEST PRESSURE GRADIENT IS STARTING TO SET
UP EARLY THIS MORNING AND WILL LIKELY RESULT IN AN INCREASE IN
NORTHEAST WINDS ACROSS MUCH OF THE LAKE THROUGH MID MORNING BEFORE
THE PRESSURE GRADIENT EASES. SPEEDS MAY PUSH 30 KT FOR A TIME
THROUGH MID OR LATE MORNING...ESPECIALLY ACROSS CENTRAL SECTIONS OF
THE LAKE. THE LOW WILL PASS SOUTH OF THE LAKE LATER THIS AFTERNOON
AND BEGIN TO WEAKEN WITH THE HIGH WEAKENING AS WELL. ANOTHER SURFACE
LOW WILL DEVELOP OVER THE ARKLATEX SATURDAY AND LIFT NORTHEAST TO
NORTHERN OHIO BY SUNDAY AFTERNOON. A VERY STRONG HIGH WILL THEN
DEVELOP SOUTHWARD INTO THE NORTHERN PLAINS AS THE LOW MOVES INTO NEW
ENGLAND SUNDAY NIGHT. THIS WILL LEAVE LAKE MICHIGAN IN THE PRESSURE
GRADIENT BETWEEN THE TWO SYSTEMS SATURDAY NIGHT AND SUNDAY WITH
COLDER AIR SPILLING ACROSS THE LAKE AS WELL. THIS WILL SET THE STAGE
FOR ANOTHER ROUND OF STRONG WINDS WHICH WILL START OUT NORTHEAST
THEN SHIFT NORTH-NORTHWEST AND EASE UP LATE SUNDAY AFTERNOON. THE
HIGH WILL PASS SOUTH OF THE LAKE TUESDAY BEFORE LOW PRESSURE TRACKS
SOUTHEAST ACROSS THE CANADIAN PRAIRIES AND NORTHERN PLAINS. THIS
SHOULD LEAD TO ANOTHER PERIOD OF INCREASED WINDS...THIS TIME FROM
THE SOUTH AND SOUTHWEST WEDNESDAY. WILL KEEP SPEEDS BELOW GALE FORCE
THROUGH THE PERIOD BUT WILL NEED TO MONITOR FOR SHORT WINDOWS OF
GALE FORCE WINDS SATURDAY NIGHT AND SUNDAY MORNING...AND AGAIN EARLY
WEDNESDAY.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 3 PM FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
DENSE FOG ADVISORY...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 3 PM
FRIDAY.
FLOOD WATCH...ILZ033-ILZ039...NOON SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 3
PM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...NOON SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM FRIDAY.
&&
$$
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AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1040 AM CST FRI DEC 20 2013
.DISCUSSION...
805 AM CST
HAVE EXPANDED THE DENSE FOG ADVISORY TO INCLUDE AREAS SOUTH OF A
PONTIAC TO VALPARAISO LINE. HAVE RECEIVED MULTIPLE REPORTS OF
DENSE FOG ALONG THE SYNOPTIC BOUNDARY...WHICH IS PRACTICALLY
STATIONARY AS THE 1006MB SFC LOW NEAR QUINCY EASES ITS WAY
NORTHEAST. GOOD POOLING OF MOISTURE AND LIGHT WINDS ALONG THIS
SHOULD CONTINUE TO ALLOW FOR DENSE FOG THROUGH 12P-3P...UNTIL THE
LOW LIFTS THROUGH THE AREA. THE RAP AND HRRR FOR THE MOST PART
SUPPORT THIS REASONING.
TEMPERATURES NORTH OF THE BOUNDARY ARE HOLDING FAIRLY STEADY...OR
EASING DOWN EVER SO GRADUALLY. THE FREEZING RAIN ADVISORY AREA
LOOKS GOOD THOUGH AND MATCHES THE 32 DEGREE ISOTHERM AT THE
SURFACE AND REPORTS WE HAVE RECEIVED...SO NO CHANGES PLANNED
THERE. STILL A CHANCE SOME LIGHT FREEZING PRECIP INCHES ITS WAY
SOUTH OF THE ADVISORY LATE THIS MORNING OR AFTERNOON...INCLUDING
INTO NORTHERN COOK AND DUPAGE COUNTIES.
MTF
//PREV DISCUSSION...
355 AM CST
SEVERAL ISSUES ONGOING THIS MORNING AS WELL THROUGH THE
WEEKEND...WITH DENSE FOG AND FREEZING RAIN ISSUES THIS MORNING
WITH THE FREEZING RAIN NOW LINGERING INTO THE AFTERNOON AND
POSSIBLY TONIGHT...CONTINUED FLOODING CONCERNS...AND LASTLY
POTENTIAL SNOWFALL WHICH THE AXIS OF HEAVIEST SNOW STILL APPEARS
TO BE ACROSS THE NORTH AND NORTHWEST AREAS OF THE CWA.
ADDRESSING THE MORE IMPORTANT ISSUES IN THE NEAR TERM...LIGHT
FREEZING RAIN OR FREEZING DRIZZLE CONTINUES ACROSS THE ADVISORY
AREA THIS MORNING...WITH LIGHT RAIN OR DRIZZLE ONGOING FOR THE
REMAINDER OF THE CWA. BROAD SOUTHWESTERLY FLOW ALOFT CONTINUES TO
USHER SEVERAL WAVES OF ENERGY...WITH ELONGATED TROUGH OF LOW
PRESSURE EXTENDING FROM THE CENTRAL PLAINS UP THROUGH SOUTHERN
GREAT LAKES. AS THESE WAVES OF ENERGY/SPEED MAXES LIFT NORTHEAST
ACROSS THE REGION THIS MORNING...EXPECT THIS TROUGH OF LOW
PRESSURE TO LIFT EAST NORTHEAST TO CENTRAL ILLINOIS AND NORTHWEST
INDIANA THROUGH THE EARLY AFTERNOON. PRESENT LOW/MID LEVEL
CONVERGENCE WILL CONTINUE TO BE A PERSISTENT THROUGH THIS
PERIOD...WITH CURRENT UPSTREAM WAVE TO AID IN TIGHTENING LOW/MID
LEVEL BAROCLINIC ZONE. THIS WILL ENHANCE FRONTOGENETIC FORCING
ACROSS THE ADVISORY AREA...ALL AIDING IN CONTINUED PRECIP
DEVELOPMENT AT LEAST THROUGH EARLY AFTERNOON FOR THE ENTIRE CWA.
HAVE INCREASED POPS THIS MORNING AND EARLY AFTERNOON...BUT WONDER
IF AFTERNOON POPS WILL NEED TO BE RAISED EVEN FURTHER WITH SHORT
TERM GUIDANCE HINTING AT CONTINUED TO DEVELOPMENT EVEN INTO THE
LATE AFTERNOON. ALTHOUGH CURRENT ASSOCIATED BOUNDARY DRAPED ACROSS
EAST CENTRAL ILLINOIS AND NORTHWEST INDIANA DID MAKE SOME
NORTHWARD PROGRESSION EARLY THIS MORNING...FEEL THAT THIS
NORTHWARD MOVEMENT HAS ENDED AND WILL REMAIN SITUATED UNTIL
DROPPING SOUTH/SOUTHEAST OF THE CWA THIS AFTERNOON. GUIDANCE
HINTING AT SOME WEAK CAA TO BEGIN OCCURRING OVER THE NEXT SEVERAL
HOURS AND WITH LATEST RAP ANALYSIS ALREADY INDICATING THIS ACROSS
WESTERN ILLINOIS...FEEL PRETTY CONFIDENT WITH THIS TREND. THIS
WILL HELP TEMPS IN THE ADVISORY AREA TO HOVER JUST BELOW OR AT THE
FREEZING MARK THROUGH MOST OF TODAY. WITH THIS CONTINUED PRECIP
AND TEMP TRENDS...HAVE DECIDED TO EXTEND THE FREEZING RAIN
ADVISORY THROUGH THE AFTERNOON AND HAVE ALSO INCLUDED KANE COUNTY
IN THE ADVISORY AS WELL. WILL NEED TO ALSO MONITOR THE AFTERNOON
PERIOD FOR THE REMAINING CWA...AS COLD ADVECTION SHOULD HELP TEMPS
LOWER AROUND FREEZING INTO THE LATE AFTERNOON PERIOD. WITH PRECIP
POSSIBLY LINGERING...COULD SEE SOME POSSIBLE LIGHT ICING IN AREAS
OUTSIDE OF THE ADVISORY. ALTHOUGH TEMPS SHOULD BE MARGINAL...AND
AM NOT OVERLY CONCERNED AT THIS TIME.
WITH REGARDS TO THE DENSE FOG...WITH INCREASING MOISTURE IN THE
BOUNDARY LAYER THIS PAST EVENING DENSE FOG DEVELOPED ALONG TO THE
NORTH OF THIS BOUNDARY. MANY REPORTS OF DENSE FOR WERE RECEIVED
THIS PAST EVENING ACROSS NORTHWEST INDIANA...PRIMARILY FOR LAKE
AND PORTER COUNTIES IN INDIANA. WITH THE BOUNDARY SITUATED AND
EXPECTED TO REMAIN THIS WAY THROUGH THE REMAINDER OF THE
MORNING...FEEL CURRENT DENSE FOG ADVISORY FOR THESE LOCATIONS
REMAINS VALID. ALTHOUGH...SOUTHERN AREAS OF COOK COUNTY AND
EASTERN AREAS OF WILL COUNTY WILL NEED TO BE MONITORED OVER THE
NEXT COUPLE OF HOURS AS VIS IN THESE LOCATIONS CONTINUES TO BOUNCE
AROUND 1/2 MILE. END TIMING FOR THIS DENSE FOG ADVISORY REMAINS 9
AM CST...AND SEEMS REASONABLE. THIS SAGGING BOUNDARY AND SLIGHTLY
DRIER AIR SHOULD HELP WITH THE MORE DENSE FOG...BUT WITH PATCHY
DENSE FOG STILL NOT OUT OF THE QUESTION AT LEAST THROUGH MID DAY.
CONFIDENCE WITH THIS FOG REMAINS LOW AT THIS TIME AND WILL NEED TO
MONITOR...POSSIBLY EXTENDING THIS ADVISORY OR MAYBE EVEN EXPANDING
IT LATER THIS MORNING.
WITH SURFACE LOW EXITING TO THE EAST THIS EVENING AND THE ARRIVAL
OF DRIER AIR...SHOULD OBSERVE OVERALL PRECIP CHANCES TO WIND DOWN
FOR THE TIME BEING. ALTHOUGH WITH GUIDANCE CONTINUING TO INDICATE
BROAD SCALE LIFT WITH THE APPROACHING LONGWAVE TROUGH TO THE WEST
IT DOES APPEAR AS IF AREAS ACROSS THE SOUTHERN CWA COULD SEE
ADDITIONAL PRECIP TONIGHT. ALTHOUGH LIGHT PRECIP...THERMAL
PROFILES WOULD INDICATE THAT THIS PRECIP WOULD BE IN THE FORM OF
LIGHT FREEZING RAIN OR LIGHT FREEZING DRIZZLE. ANOTHER PERIOD I AM
CONCERNED ABOUT AT THIS TIME IS LATE TONIGHT INTO EARLY SATURDAY
MORNING...ONCE AGAIN FOR AREAS ACROSS THE SOUTHERN CWA. WILL NEED
TO MONITOR SURFACE TEMP TRENDS ACROSS EAST CENTRAL ILLINOIS DURING
THIS TIME...WITH FREEZING RAIN ONCE AGAIN POSSIBLY BEING AN ISSUE.
EXPANDING PRECIP TO THE SOUTH IS EXPECTED TO INCH FURTHER NORTH
TOWARDS THE SOUTHERN CWA TOWARDS THE 12Z SATURDAY TIME
FRAME...WITH SOUTHWEST FLOW ALOFT PERSISTING OUT AHEAD OF THE
APPROACHING LONGWAVE TROUGH. WITH A SLOW TEMP TREND EXPECTED
SATURDAY MORNING...A PERIOD OF LIGHT FREEZING RAIN COULD CAUSE
SOME ISSUES PRIMARILY SOUTH OF I-80.
WITH REGARDS TO WINTER STORM SATURDAY THROUGH SUNDAY...LATEST
THINKING/UPDATES TO FORECAST CONTINUE TO SUPPORT CURRENT WINTER
STORM WATCH ACROSS NORTHERN PORTIONS OF THE CWA. EXPECTED VARYING
PRECIP TYPES INCLUDING ALMOST ALL WINTER PRECIP TYPES COULD BE
OBSERVED SATURDAY INTO SATURDAY NIGHT...WITH A VARYING THERMAL
PROFILE EXPECTED TO CHANGE THROUGH THE PERIOD FOR ALL AREAS. WILL
NEED TO MONITOR THE SATURDAY MORNING TIME FRAME INTO THE DAY
SATURDAY FOR THE VARYING PRECIP TYPE...POSSIBLY ADDING YET ANOTHER
HEADLINE TO ACCOMMODATE FOR THE WINTRY MIX. EXPECTED SURFACE LOW
TRACK STILL SUPPORTIVE FOR BEST CHANCES FOR SNOW OR ALL SNOW
ACROSS NORTHWEST AND NORTH CENTRAL ILLINOIS WITH SNOWFALL TOTALS
IN EXCESS OF 6 INCHES STILL APPEARING POSSIBLE. THE EXPECTED RAIN
SNOW LINE HAS VARIED SLIGHTLY...BUT THE GENERAL IDEA REMAINING THE
SAME. OHARE TO PERU ILLINOIS LINE ARE THE DIVIDING LINE AT THIS
TIME...WITH CURRENT SNOW FORECAST INDICATING RAPID INCREASE IN
SNOW AMOUNTS RIGHT TO THE NORTH OF THIS LINE AND WITH AREAS TO THE
SOUTH OBSERVING LIGHT SNOW ACCUMULATIONS.
ALTHOUGH LATEST TRENDS ARE INDICATING THAT THE AXIS OF HEAVIEST
RAINFALL IS BEGINNING TO SHIFT SOUTH OF THE CWA...DECENT RAINFALL
AMOUNTS OF UP TO AN INCH STILL SUPPORT THE POSSIBILITY OF
FLOODING...AND HAVE MADE NO CHANGES TO THE CURRENT FLOOD WATCH.
RODRIGUEZ
MEDIUM AND LONG RANGE...MONDAY THROUGH THURSDAY...
MAIN CONCERNS BEYOND THIS WEEKEND ARE THE RETURN OF ARCTIC AIR AND
MUCH COLDER TEMPERATURES MONDAY-TUESDAY...AND THE POTENTIAL FOR A
LITTLE LIGHT SNOW CHRISTMAS EVE-CHRISTMAS DAY.
DEEP UPPER TROUGH TRAVERSING THE REGION MONDAY WITH FAIRLY
IMPRESSIVE SHORT WAVE ENERGY PASSING OVERHEAD. FORECAST SOUNDINGS
INDICATE SATURATION IN LOW LEVELS...WITH TEMPS NEAR -15C AS BOUNDARY
LAYER COOLS IN BLUSTERY COLD ADVECTION BEHIND DEPARTING WEEKEND LOW
PRESSURE SYSTEM. THIS SHOULD SUPPORT FLURRIES/LIGHT SNOW SHOWERS
ACROSS THE CWA INTO THE AFTERNOON HOURS. OF MORE IMPORTANCE THAN THE
POTENTIAL FOR LIGHT SNOW SHOWERS OR FLURRIES HOWEVER WILL BE THE
MUCH COLDER TEMPS AND WIND CHILLS AS ARCTIC AIR PLUNGES BACK INTO
THE REGION. TEMPS AT H8 FALL TO AROUND -16 C BY LATE AFTERNOON WITH
H9 TEMPS NEARLY SO...SUGGESTING SURFACE TEMPS MAY STRUGGLE TO RISE
ABOVE 10-15F AND WILL LIKELY FALL INTO THE SINGLE DIGITS ACROSS
NORTH CENTRAL IL AND WIND CHILLS IN THE NEGATIVE SINGLE DIGITS.
SURFACE HIGH PRESSURE RIDGE WILL BUILD ACROSS THE MISSISSIPPI VALLEY
AND INTO IL MONDAY NIGHT IN RESPONSE TO SUBSIDENCE BEHIND THE
DEPARTING UPPER TROUGH...WITH CLEARING SKIES...NEW SNOW COVER
ESPECIALLY FAR NORTHERN IL...AND DECREASING WINDS EXPECTED TO RESULT
IN STRONG RADIATIONAL COOLING. BOTH GFS AND ECMWF MOS DEPICT
SUB-ZERO LOWS ACROSS MUCH OF NORTHERN IL BY SUNRISE TUESDAY. SURFACE
HIGH PRESSURE RIDGE MOVES ACROSS THE AREA DURING THE DAY TUESDAY...
WITH WINDS BACKING TO THE SOUTH-SOUTHEAST DURING THE AFTERNOON AS
WARM ADVECTION DEVELOPS (ALOFT AT LEAST) IN ADVANCE OF A SHORT WAVE
EMERGING FROM THE PLAINS. MODERATION IN TEMPS LIMITED AT THE SURFACE
HOWEVER WITH VERY COLD START TO DAY AND STRONG INVERSION LIMITING
WARMING AT THE SURFACE WITH HIGHS IN THE TEENS/LOW 20S.
LONG RANGE GUIDANCE SIMILAR IN BRINGING SHORT WAVE TROUGH ACROSS
THE REGION DURING THE TUESDAY NIGHT/WEDNESDAY PERIOD AND ANOTHER
WEDNESDAY NIGHT/THURSDAY...THOUGH DIFFERENCES DO EXIST WITH
AMPLITUDE OF THESE INDIVIDUAL WAVES AND ASSOCIATED SURFACE
REFLECTIONS. THE ECMWF IS STRONGER/MORE AMPLIFIED WITH BOTH...
THOUGH AT THIS DISTANCE HAVE FOCUSED MAINLY ON SIMILARITIES BETWEEN
GUIDANCE. THIS YIELDS A LITTLE TEMPERATURE MODERATION CHRISTMAS EVE
AND CHRISTMAS DAY WITH A CHANCE OF SOME LIGHT SNOW...PERHAPS
0.5-1.0" BASED ON ROUGH QPF OUTPUT. LIGHT SNOW MAY LINGER ACROSS
THE EASTERN CWA CHRISTMAS NIGHT INTO THURSDAY WITH SURFACE COLD
FRONTAL TROUGH. AS MENTIONED...BRIEF MODERATION PRODUCES HIGHS IN
THE 20S/AROUND 30 FOR CHRISTMAS DAY THEN COLDER AIR LOOKS TO RETURN
THURSDAY BEHIND THE FRONT WITH TEMPS IN THE TEENS/LOW 20S.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 16Z...
* IFR CIG/VSBY TRENDS THIS AFTERNOON.
* WINDS GRADUALLY BACKING TO NORTH AND THEN NORTHWEST.
* PRECIPITATION TRENDS...MOST LIKELY LIQUID AT ORD/MDW BUT MIXED
PRECIP POSSIBLE.
LENNING
//DISCUSSION...UPDATED 12Z...
LOW PRESSURE IS NOW MOVING NORTHEAST ACROSS CENTRAL MISSOURI WITH
A FRONTAL BOUNDARY STRETCHED FROM THE LOW TO SOUTHERN ONTARIO.
THIS FRONT HAS BEEN DRIFTING SOUTH THE LAST FEW HOURS WHICH HAS
HELPED VSBY TO NOTICEABLY IMPROVE WITH CIGS ALSO IMPROVING BUT AT
A MUCH SLOWER RATE. WAVES OF RAIN/DRIZZLE CONTINUE TO MOVE ACROSS
DPA/ORD/MDW/GYY WITH FREEZING RAIN AT RFD THANKS TO AN INFLUX OF
COLDER AIR. THIS COLDER AIR WILL SPREAD SOUTHWARD ACROSS THE OTHER
TERMINALS INTO THE AFTERNOON. WITH DAYTIME HEATING AND AN END TO
THE PRECIP ARRIVING THIS AFTERNOON THE THREAT FOR FZRA/FZDZ ACROSS
THE CHI/NW INDIANA TERMINALS LOOKS LOW. HOWEVER...IF COOLING
OCCURS MORE QUICKLY THAN FORECAST THEN THE THREAT FOR FREEZING
PRECIP WILL INCREASE EARLY THIS AFTERNOON. OTHERWISE...EXPECT IFR
CIG TO PREVAIL THROUGH MUCH OF THE DAY WITH MAINLY MVFR VSBY BY
MID MORNING IF NOT SOONER AT SITES THAT STILL HAVE IFR VSBY. WINDS
WILL VARY BETWEEN NORTH AND NORTH-NORTHEAST THROUGH THE AFTERNOON
THEN TURN NORTH-NORTHWEST THIS EVENING.
THE NEXT STORM SYSTEM WILL APPROACH FROM THE SOUTH SATURDAY...WITH
PRECIP POSSIBLY REACHING THE CHI/NW INDIANA TERMINALS DURING THE
MORNING. A MIX OF PRECIPITATION TYPES IS EXPECTED WITH DETAILS OF
TIMING OF TYPE CHANGES STILL UNCERTAIN. OVERALL...RFD WILL HAVE
THE BEST CHANCE FOR SIGNIFICANT ACCUMULATING SNOW...THOUGH SLEET
MAY MIX IN AT TIMES.
MDB
//ORD AND MDW CONFIDENCE...UPDATED 16Z...
* HIGH CONFIDENCE IN IFR CIGS CONTINUING. LOW CONFIDENCE IN HOW
THEY CHANGE AFTER PRECIP ENDS THIS AFTERNOON.
* HIGH CONFIDENCE IN MVFR OR BETTER VSBY TODAY.
* HIGH CONFIDENCE IN WIND BACKING TO NORTHWEST...MEDIUM CONFIDENCE
ON TIMING.
* HIGH CONFIDENCE IN LIGHT RAIN/DRIZZLE CONTINUING THROUGH EARLY
AFTERNOON. LOW CONFIDENCE IN POTENTIAL FOR -FZRA/FZDZ THIS
AFTERNOON.
LENNING
//OUTLOOK FOR ORD/MDW FOR 00Z SUNDAY-12Z FRIDAY...UPDATED 12Z...
SATURDAY NIGHT...WINTRY MIX...IFR LIKELY.
SUNDAY...SNOW AND IFR.
MONDAY...CHANCE FOR SNOW...MVFR/IFR POSSIBLE.
TUESDAY...VFR.
WEDNESDAY...SLIGHT CHANCE SNOW...MVFR POSSIBLE.
THURSDAY...MVFR BECOMING VFR.
MDB
&&
.MARINE...
301 AM CST
LOW PRESSURE CENTERED OVER NORTH-CENTRAL OKLAHOMA WILL TRACK
NORTHEAST ALONG A FRONTAL BOUNDARY WHICH EXTENDS NORTHEAST INTO
NORTHERN INDIANA AND EASTWARD ACROSS LAKE ERIE AND ONTARIO.
MEANWHILE HIGH PRESSURE OVER THE NORTHERN PLAINS WILL MOVE LITTLE
THROUGH THE DAY. THE STRONGEST PRESSURE GRADIENT IS STARTING TO SET
UP EARLY THIS MORNING AND WILL LIKELY RESULT IN AN INCREASE IN
NORTHEAST WINDS ACROSS MUCH OF THE LAKE THROUGH MID MORNING BEFORE
THE PRESSURE GRADIENT EASES. SPEEDS MAY PUSH 30 KT FOR A TIME
THROUGH MID OR LATE MORNING...ESPECIALLY ACROSS CENTRAL SECTIONS OF
THE LAKE. THE LOW WILL PASS SOUTH OF THE LAKE LATER THIS AFTERNOON
AND BEGIN TO WEAKEN WITH THE HIGH WEAKENING AS WELL. ANOTHER SURFACE
LOW WILL DEVELOP OVER THE ARKLATEX SATURDAY AND LIFT NORTHEAST TO
NORTHERN OHIO BY SUNDAY AFTERNOON. A VERY STRONG HIGH WILL THEN
DEVELOP SOUTHWARD INTO THE NORTHERN PLAINS AS THE LOW MOVES INTO NEW
ENGLAND SUNDAY NIGHT. THIS WILL LEAVE LAKE MICHIGAN IN THE PRESSURE
GRADIENT BETWEEN THE TWO SYSTEMS SATURDAY NIGHT AND SUNDAY WITH
COLDER AIR SPILLING ACROSS THE LAKE AS WELL. THIS WILL SET THE STAGE
FOR ANOTHER ROUND OF STRONG WINDS WHICH WILL START OUT NORTHEAST
THEN SHIFT NORTH-NORTHWEST AND EASE UP LATE SUNDAY AFTERNOON. THE
HIGH WILL PASS SOUTH OF THE LAKE TUESDAY BEFORE LOW PRESSURE TRACKS
SOUTHEAST ACROSS THE CANADIAN PRAIRIES AND NORTHERN PLAINS. THIS
SHOULD LEAD TO ANOTHER PERIOD OF INCREASED WINDS...THIS TIME FROM
THE SOUTH AND SOUTHWEST WEDNESDAY. WILL KEEP SPEEDS BELOW GALE FORCE
THROUGH THE PERIOD BUT WILL NEED TO MONITOR FOR SHORT WINDOWS OF
GALE FORCE WINDS SATURDAY NIGHT AND SUNDAY MORNING...AND AGAIN EARLY
WEDNESDAY.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...FREEZING RAIN ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012 UNTIL 3 PM FRIDAY.
WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012...6 PM SATURDAY TO 6 PM SUNDAY.
DENSE FOG ADVISORY...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL 3 PM
FRIDAY.
FLOOD WATCH...ILZ033-ILZ039...9 AM SATURDAY TO 6 AM SUNDAY.
IN...DENSE FOG ADVISORY...INZ001-INZ002-INZ010-INZ011-INZ019 UNTIL 3
PM FRIDAY.
FLOOD WATCH...INZ010-INZ011-INZ019...9 AM SATURDAY TO 6 AM
SUNDAY.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 9 PM FRIDAY.
DENSE FOG ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM FRIDAY.
&&
$$
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AREA FORECAST DISCUSSION
NWS DODGE CITY KS
210 PM CST Fri Dec 20 2013
...Updated Long Term Section...
.SHORT TERM...(Today and tonight)
ISSUED AT 340 AM CST FRI DEC 20 2013
The approaching winter weather will be covered in the long
term discussion since the vast majority of winter weather
is expected after 12z Saturday.
Cold high pressure will be centered over Nebraska and South Dakota
today, but the southern periphery of the high will be wedged into
southwestern Kansas. It is a tough call as to whether the low stratus
clouds will clear out, allowing temperatures to modify a little
today. The NAM and SREF indicate clearing with highs around 33F at
Dodge City, 30F at Hays and 36 at Elkhart, while the RAP holds
onto the stratus for areas east of Garden City, with much cooler
highs in upper teens to lower and mid 20s. Opted to go with an in
between solution due to the uncertainty, with mid to high 20s at
Hays, Dodge City and Pratt, and lower 30s in far southwestern and
Western Kansas. Some mid to high level cloud will be increasing
late today in advance of the aforementioned upper level trough. By
tonight, mid level cloud will continue to increase over southwestern
Kansas, with only limited radiational cooling in the brief clear
breaks. Temperatures should bottom out in the upper teens to lower
20s, but could be lower if temperatures stay colder today.
.LONG TERM...(Saturday night through Friday)
ISSUED AT 209 PM CST FRI DEC 20 2013
After the strong upper level cyclone near the Arizona/old Mexico
border lifts out across the central United States Saturday and
Saturday night, a period of quiet weather should return to western
Kansas. Sea surface temperatures remain very warm in the north
Pacific with a large warm pool more than 2C above climatology
centered near 150W 45N. Vigorous low pressure systems west of the
warm pool have carried warm air northward and have supported a
persistent high amplitude upper level ridge around 140W to 150W
since late November. Surface anticyclogenesis downstream from
the ridge has favored maintenance of a large pool of very cold air
in Canada with frequent incursions of frigid air into the United
States. There is little indication that a major adjustment
will occur in the near term, although the CFS and the multi-model
ensemble solutions persist in developing warm temperatures in
western Canada in January.
Tropical thunderstorms remain active across much of the Indian Ocean
south of the equator and over the Maritime Continent into eastern
Asia. There have been several fast moving Kelvin waves that have
rippled through the tropics, but there has been little coherent
propagation that projects onto a Madden-Julian Oscillation. The CFS
persists in propagating a Madden-Julian Oscillation into the western
hemisphere in early January, but most of the other models are much
less aggressive. The typical response to an eastward propagating
Madden Julian Oscillation in Phases 5 and 6 of the Wheeler-Hendon
phase space diagram is warmer than average temperatures in the
Midwest and eastern United States. Given doubts about evolution of
the Madden-Julian Oscillation, confidence in the warm temperatures
in early January is very low.
Atmospheric relative angular momentum remains below climatological
averages, but mountain torque contribution from Asia has been
positive in recent days. The tendency of atmospheric relative
angular momentum is strongly positive, and the atmosphere likely
will remain in Phase 4 of the Weickmann Berry Global Wind
Oscillation phase space diagram for a few days. Phase 4 correlates
with anticyclonic flow in the western United States, so the concept
of building heights in the western part of the country and
progressing the long wave trough to the Mississippi Valley by 26-27
December is reasonable. As such, the really frigid air probably will
remain east of western Kansas next week, although there will be
occasional glancing blows of arctic air through early January.
Progression of the long wave pattern will be less favorable for
anticyclonic wave breaks in the southwestern United States, and the
potential for significant precipitation in this part of the world is
low for the rest of December.
Stratospheric temperatures have become anomalously warm at 10mb in
the eastern United States since early December, and stratospheric
temperatures have been warming at 30mb and 50mb over the North
Atlantic. Whether this will support maintenance of a blocky
anticyclone in the North Atlantic and persistence of the mean trough
in the eastern United States remains to be seen, but the atmosphere
seems to favor this pattern. The atmosphere likely will continue to
be characterized by ridging near the west coast and a mean trough in
the eastern part of the country through at least the first part of
January.
In the nearer term, snowfall will wind down quickly Saturday
evening, and skies should become partly cloudy on Sunday. Cold air
and snow cover in much of southwest Kansas will keep temperatures
below freezing Sunday. A minor upper level trough embedded in strong
northwest flow will approach northern Kansas Sunday night, and mid
level frontogenesis will favor development of widespread mid level
cloudiness and scattered snow flurries. Temperatures south of the
mid level cloud shield will radiate to near zero over the snow field
with somewhat warmer temperatures in west central Kansas, where snow
cover is likely to be minimal to nonexistent. Low level south to
southeast flow will recirculate arctic air Monday, and temperatures
will remain cold with highest values near the Colorado border.
The next vigorous upper level trough near the dateline will ripple
through the flow into the western United States Tuesday and approach
the Central Plains Tuesday night. Lee troughing resulting from
increasing flow perpendicular to the Rockies will increase south
flow Monday night and Tuesday, and temperatures should rise above
freezing Tuesday. A weak front will pass through western Kansas
Tuesday night, and a stronger surge of cold air should arrive
Wednesday night. The ECMWF has a stronger trough rotating through
the Northern Plains than the GFS Wednesday night and carries a much
stronger surge of cold air into Kansas than the GFS. The blended
forecast for Thursday may be too warm, but confidence is not high
enough to justify getting too carried away with the cold air yet.
Eastward progression of the ridge and downslope flow will support
considerably warmer temperatures Friday and Saturday.
&&
.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1125 AM CST FRI DEC 20 2013
North winds at 10 to 15 knots will become light and variable this
afternoon and continue through the remainder of the taf period.
MVFR cigs at the beginning of the period are expected to dissipate
or rise into the VFR category by late afternoon. An approaching
storm system will begin impacting central and southwest Kansas
late tonight or early Saturday morning with MVFR ceilings
redeveloping. There will also be some potential for freezing
drizzle or flurries developing at Garden City and Dodge City
toward the end of the period.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 16 26 17 28 / 40 90 100 0
GCK 16 28 17 29 / 20 70 90 0
EHA 18 30 20 31 / 40 80 60 10
LBL 17 28 18 30 / 40 90 100 0
HYS 14 28 15 27 / 10 50 90 10
P28 21 29 19 29 / 50 100 100 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY from Midnight tonight to 6 AM CST Sunday
FOR KSZ045-046-063>066-075>081-084>090.
&&
$$
SHORT TERM...Finch
LONG TERM...Ruthi
AVIATION...Gerard
AREA FORECAST DISCUSSION
NWS WICHITA KS
1155 AM CST FRI DEC 20 2013
.UPDATE...
ISSUED AT 1153 AM CST FRI DEC 20 2013
MAIN ISSUE IS LOW CLOUDS. ONLY RUC SO FAR SEEMS TO HAVE MUCH OF A
HANDLE ON THE EXTENSIVE LOW CLOUDS. HOWEVER NOT VERY CONFIDENT IN
HOW LONG CLOUDS WILL PERSIST WEST OF I-35 WITH SOME BREAKS FINALLY
APPEARING ON VISIBLE SATELLITE OVER WESTERN KS/NORTHWEST OK.
TEMPERATURES WILL BE LIMITED TODAY WITH THE EXTENSIVE CLOUDS AND
MID SHIFT HAD THIS FAIRLY WELL IN HAND...WITH ONLY MINOR TWEAKS
TO GOING FORECAST. -HOWERTON
&&
.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 229 AM CST FRI DEC 20 2013
ARCTIC FRONT WILL CONTINUE TO PUSH THROUGH THE REMAINDER OF
SOUTHEAST KS THRU MID MORNING. LOW-LEVEL MOISTURE AND WEAK
CONVERGENCE WITHIN THE 850 BOUNDARY WILL YIELD SOME FLURRIES AND
SPOTTY LIGHT FREEZING DRIZZLE INTO MID MORNING IN SOUTH
CENTRAL/SOUTHEAST KS WHICH MAY CAUSE SOME SLICK SPOTS. THE ARCTIC
AIR IS EXPECTED TO REMAIN ENTRENCHED THROUGH THIS WEEKEND.
A VIGOROUS STORM SYSTEM OVER THE NORTHERN BAJA/DESERT SOUTHWEST
EARLY THIS MORNING...REMAINS PROGGED TO MOVE ACROSS THE SOUTHWEST
TODAY...EJECTING NORTHEASTWARD ACROSS THE SOUTHERN PLAINS AND MID
MISSISSIPPI VALLEY SATURDAY INTO SATURDAY NIGHT. THE 00Z GFS AND
ECMWF MODELS REMAIN CONSISTENTLY FURTHER NORTH WITH THE MID-LEVEL
DEFORMATION ZONE AND 850-700 RH AXIS...WHEREAS THE NAM HAS TRENDED
FURTHER SOUTH. WILL LEAN WITH A GFS/ECMWF COMPROMISE WHICH IS
CLOSE TO OUR GOING FORECAST...HOWEVER WE FEEL THERE IS STILL
ENOUGH UNCERTAINTY ON THE MID-LEVEL DEFORMATION ZONE/TROWAL
LOCATION AND ASSOCIATED PRECIPITATION TYPES TO KEEP A WINTER
STORM WATCH IN EFFECT FOR NOW.
SOME LIGHT FREEZING PRECIPITATION MAY BREAK OUT IN SOUTH
CENTRAL/SOUTHEAST KS AS SOON AS LATE TONIGHT. THE STRONGEST LIFT WITH
A PERIOD OF COUPLED FORCING ARRIVES SATURDAY AFTERNOON/EVENING
TARGETING SOUTH CENTRAL KS INTO THE FLINT HILLS. THE GFS/ECMWF BLEND
WOULD SUGGEST A SWATH OF HEAVIER SNOW ACCUMULATIONS FROM SOUTHWEST
AND SOUTH CENTRAL KS THROUGH NORTHEAST KS. LIGHT ICE ACCUMULATIONS
(0.1-0.2 INCH) WILL BE POSSIBLE IN THE SOUTH DUE TO FREEZING RAIN.
GIVEN EXPECTED MARGINAL SURFACE TEMPS (UPR 20S/LWR 30S)...THIS WOULD
PREDOMINATELY AFFECT UNTREATED ROAD SURFACES AND OVERPASSES.
IN THE WAKE OF THE STORM SYSTEM SUNDAY...ARCTIC HIGH PRESSURE ACROSS
THE CENTRAL PLAINS WILL KEEP TEMPERATURES MUCH COLDER THAN NORMAL
SUNDAY-SUNDAY NIGHT. LOWS COULD BE WELL DOWN IN THE SINGLE DIGITS
SUNDAY NIGHT ESPECIALLY WHERE THERE IS SNOWPACK.
JMC
.LONG TERM...(MONDAY THROUGH THURSDAY)
ISSUED AT 229 AM CST FRI DEC 20 2013
INITIAL UPPER TROUGH WILL SHIFT TO THE EASTERN CONUS EARLY NEXT
WEEK. FOR MID-LATE WEEK...UPPER RIDGING WILL AMPLIFY UP THE WEST
COAST INTO BRITISH COLUMBIA. THIS WILL ALLOW SHORTWAVE ENERGY TO
DIG OUT OF SOUTHWEST CANADA INTO THE NORTH CENTRAL CONUS. THIS
PATTERN FAVORS COLDER THAN AVERAGE TEMPERATURES TO CONTINUE IN OUR
AREA. EXPECTING MOST OR ALL OF THIS PERIOD TO REMAIN DRY.
JMC
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1153 AM CST FRI DEC 20 2013
VERY DIFFICULT FORECAST WITH MODELS STRUGGLING BADLY WITH LOW LEVEL
MOISTURE. DEEP LAYER LIFT IS SOMEWHAT LIMITED. GFS SUGGEST A
TRANSIENT BAND WILL MOVE ACROSS KHUT/KRSL/KSLN THIS EVENING...WITH
SECOND AREA IN THE VICINITY OF KCNU AFTER MIDNIGHT AND KICT IN THE
MORNING. THE PREDOMINATE WEATHER TYPE IS MORE LIKELY LIGHT SNOW AT
KRSL/KSLN/KHUT TONIGHT...WITH WINTRY MIX A KCNU AND SNOW/SLEET AT
KICT SAT MORNING. -HOWERTON
&&
.PRELIMINARY POINT TEMPS/POPS...
WICHITA-KICT 27 22 30 21 / 10 50 90 90
HUTCHINSON 25 20 29 19 / 10 30 90 90
NEWTON 25 21 29 19 / 10 40 90 90
ELDORADO 26 22 31 20 / 10 50 90 90
WINFIELD-KWLD 28 24 32 22 / 10 70 90 90
RUSSELL 25 14 27 17 / 10 10 60 50
GREAT BEND 25 16 28 18 / 10 20 70 60
SALINA 24 17 28 18 / 10 20 90 90
MCPHERSON 24 19 29 18 / 10 30 90 90
COFFEYVILLE 32 25 34 24 / 10 90 90 90
CHANUTE 29 24 33 23 / 10 70 90 90
IOLA 29 23 33 23 / 10 60 90 90
PARSONS-KPPF 30 24 33 24 / 10 80 90 90
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE SATURDAY NIGHT
FOR KSZ047>053-067>072-082-083-091>096-098>100.
&&
$$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
1125 AM CST Fri Dec 20 2013
...Updated aviation discussion...
.SYNOPSIS...
ISSUED AT 340 AM CST FRI DEC 20 2013
An upper level trough was progressing southeastward into
northwestern Mexico and the southern Rockies early this morning
while a wedge of arctic air surged southward into the central
plains. Stratus covered western Kansas in the wake of the front,
with ceilings from 1000-2000 ft. Mid to high level winds were
generally out of the west-southwest over the central and southern
plains ahead of the southwestern system.
&&
.SHORT TERM...(Today and tonight)
ISSUED AT 340 AM CST FRI DEC 20 2013
The approaching winter weather will be covered in the long
term discussion since the vast majority of winter weather
is expected after 12z Saturday.
Cold high pressure will be centered over Nebraska and South Dakota
today, but the southern periphery of the high will be wedged into
southwestern Kansas. It is a tough call as to whether the low stratus
clouds will clear out, allowing temperatures to modify a little
today. The NAM and SREF indicate clearing with highs around 33F at
Dodge City, 30F at Hays and 36 at Elkhart, while the RAP holds
onto the stratus for areas east of Garden City, with much cooler
highs in upper teens to lower and mid 20s. Opted to go with an in
between solution due to the uncertainty, with mid to high 20s at
Hays, Dodge City and Pratt, and lower 30s in far southwestern and
Western Kansas. Some mid to high level cloud will be increasing
late today in advance of the aforementioned upper level trough. By
tonight, mid level cloud will continue to increase over southwestern
Kansas, with only limited radiational cooling in the brief clear
breaks. Temperatures should bottom out in the upper teens to lower
20s, but could be lower if temperatures stay colder today.
.LONG TERM...(Saturday through Thursday)
ISSUED AT 254 AM CST FRI DEC 20 2013
Models this morning remain in good agreement with an upper level
trough/low lifting northeast from west central Texas into western
Oklahoma on Saturday. Widespread steady precipitation is expected
by the early Saturday morning across southwest and south central
Kansas given the moisture, warm air advection, and improving
frontogenesis ahead of the approaching upper level system. The
warm air advection early Saturday will result in a wintry mix
early Saturday, however the NAM, GFS, and ECMWF still disagree
with the magnitude of warm layer aloft. At this time confidence is
low on which model may be more correct so have decided to lean
towards a compromise between the warmer GFS and the cooler NAM and
ECMWF. Based on this as a first guess and applying the top down
approach it still appears that there will be an extended period of
sleet and freezing rain across much of south central Kansas early
Saturday morning. The area more favorable for ice accumulations
currently appears to be southeast of a Stafford to Greensburg to
Ashland line. Further northwest a brief period of freezing
precipitation will be possible early Saturday, however this should
quickly change over to snow during the early morning hours.
By Saturday afternoon the atmosphere will cool enough for mainly
snow and an area of 850-700mb frontogenesis will begin to improve
across southwest Kansas. The 00z Friday model runs continue to
indicated some discrepancies with where this area of forcing will
develop, however they all agree that as frontogenesis improves the
snow will become steadier and heavier at times Saturday afternoon
and early Saturday night. Both the GFS and ECMWF continues to
highlight this area of frontogenesis will be developing near a
line from roughly Hugoton to near Dodge City to around LaCrosse.
00z NAM was further southeast. At this time given the agreement
between the GFS and ECMWF and the run to run consistency on
location of this frontogenesis have decided to stay close to the
00z GFS/ECMWF. The steadiest and heaviest snowfall appears to
occur from 18z to 06z as the forcing along the mid level
baroclinic zone strengths and remains nearly stationary. After 06z
this baroclinic zone will begin to slide east towards central
Kansas as the upper trough moves across southeast Kansas and into
Missouri. Snow accumulations of 2 to near 6 inches still appears
reasonable. Locally higher accumulations are not out of the
question from Dodge City northeast where the snow is expected to
begin sooner and the mid level forcing appears to last slightly
longer. Given that there still is some uncertainty on location and
snowfall amounts late Saturday and Saturday night have decided to
continue with the Winter Storm Watch and not upgrade to a warning
or advisory just yet.
On Sunday a weaker upper level disturbance will cross western
Kansas. Although snow is not anticipated with this next weaker
system, increasing clouds may aid in keeping temperatures down
Sunday afternoon. Based on possible cloud cover and expected
snowfall on Sunday will continue to favor the cooler MAV/MOSGUIDE
for highs given expected snow cover.
On Sunday night an area of high pressure at the surface will
start to build into Kansas from the north. As the surface ridge
axis moves into portions of western Kansas the winds will become
light and variable. Light winds and snow cover will provided
favorable conditions for temperatures to fall back to near zero
given a period of clear skies. At this time however am somewhat
concerned about some increasing clouds after midnight. As a result
will trim temperatures back into the single digits which are
cooler latest guidance.
A gradual warming trend will then begin to develop early next
week as a northwest flow backs and becomes more perpendicular to
the Rockies. How quickly temperatures will rebound early next week
is still somewhat unclear, but the latest temperature trend
currently in the forecast still appears to be on track. A cold
front crossing western Kansas mid week will end this warming trend
briefly.
&&
.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1125 AM CST FRI DEC 20 2013
North winds at 10 to 15 knots will become light and variable this
afternoon and continue through the remainder of the taf period.
MVFR cigs at the beginning of the period are expected to dissipate
or rise into the VFR category by late afternoon. An approaching
storm system will begin impacting central and southwest Kansas
late tonight or early Saturday morning with MVFR ceilings
redeveloping. There will also be some potential for freezing
drizzle or flurries developing at Garden City and Dodge City
toward the end of the period.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 23 20 26 17 / 10 50 100 100
GCK 24 19 27 17 / 10 30 90 90
EHA 28 21 30 20 / 10 40 80 60
LBL 25 20 28 18 / 10 50 100 100
HYS 21 19 28 15 / 0 20 80 90
P28 25 23 28 19 / 10 70 100 100
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH from late tonight through late Saturday night
FOR KSZ064>066-076>081-085>090.
&&
$$
SYNOPSIS...Finch
SHORT TERM...Finch
LONG TERM...Burgert
AVIATION...Gerard
AREA FORECAST DISCUSSION
NWS PADUCAH KY
239 PM CST Fri Dec 20 2013
.SHORT TERM...(This Evening through Sunday)
ISSUED AT 238 PM CST FRI DEC 20 2013
Flood Watch will continue as is tonight through Saturday night.
Still looking at 2-4+ inches area wide, slightly higher amounts
to 5 inches possible near and just NW of the Ohio River. Front
will enter the area tonight and stall near the Ohio River. Rain
and storms forecast to increase tonight especially after midnight,
continuing through Saturday.
Could see a few strong to severe storms Saturday late day and
evening as wind fields increase substantially with some surface
based instability along and south of the boundary, especially
across west Kentucky. Isolated damaging wind gusts and a brief
short lived tornado or two cannot be ruled out. The activity
should quickly push to the east after midnight Saturday as we
dry slot. Mid level drying will be pronounced, but low level
moisture will linger with SW flow aloft. May be some drizzle into
Sunday but that`s about it, as temperatures fall through the day.
In terms of temps, dew points and winds with the front coming into
the area tonight and Saturday, used a blend of RAP 13km data and
short term 3 hourly GFS/NAM data.
.LONG TERM...(Sunday Night through Friday)
ISSUED AT 238 PM CST FRI DEC 20 2013
In the wake of the weekend storm...colder and drier air will arrive
for early next week. Model soundings depict some lingering moisture
Sunday night until the passage of the 850 mb trough axis. This could
translate into some flurries or drizzle...but no measurable precip
is indicated in the 12z gfs/nam/ecmwf model qpf. By Monday
night...mainly clear skies are expected.
Monday night...the combination of clear skies and decreasing winds
should allow temps to radiate nicely. Will lower Monday night
lows closer to gfs and ecmwf mos...both of which range from 10 to 15
degrees across most of the area.
Tuesday will be another cold day...but there is about a 10 degree
difference between ecmwf and gfs mos highs. The 00z ecmwf is more
progressive with the eastward motion of the thermal trough...while
the 12z gfs lingers the cold air through the day. Will split the
difference between them...which yields highs in the upper 20s to
lower 30s despite sunny skies.
The models depict a 500 mb longwave trough axis setting up over the
Mississippi Valley Christmas Day into Thursday. Shortwaves rotating
through the trough will bring at least some cloudiness...if not
measurable light precip. Model soundings have trended drier during
this time period...and the 12z gfs and gfs ensemble mean show zero
qpf. The 12z ecmwf indicates some patchy light precip. Will follow
the model trends and lower pops into the slight chance category for
Christmas night and Thursday. Precip type would be mainly snow until
boundary layer temps become marginal for snow Thursday
afternoon.
In the wake of the departing longwave trough...another shot of cold
air is expected for Friday. As would be expected seven days
out...there is fair to poor agreement on how cold it will get.
Forecast will represent a blend of gfs/ecmwf temps.
&&
.AVIATION...
ISSUED AT 1123 AM CST FRI DEC 20 2013
Low end MVFR cigs to persist through the afternoon with gusty SSW
winds in the 10-20kt range. Will carry VCSH for now given limited
activity seen radar. Activity should increase tonight, especially
from 03 UTC on. Brought the front through KCGI, but held for now
on KPAH/KEVV and KOWB. Went prevailing SHRA overnight with VCTS as
instability supportive of TSRA develops. The cold front entering
into the region should reach to about the Ohio River and then
stall, maybe lift slightly back to the north Saturday morning.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...FLOOD WATCH from 6 PM CST this evening through late Saturday
night FOR ILZ075>078-080>094.
MO...FLOOD WATCH from 6 PM CST this evening through late Saturday
night FOR MOZ076-086-087-100-107>112-114.
IN...FLOOD WATCH from 6 PM CST this evening through late Saturday
night FOR INZ081-082-085>088.
KY...FLOOD WATCH from 6 PM CST this evening through late Saturday
night FOR KYZ001>022.
&&
$$
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1218 PM CST FRI DEC 20 2013
.UPDATED FOR 18Z AVIATION DISCUSSION...
ISSUED AT 1209 PM CST FRI DEC 20 2013
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CST FRI DEC 20 2013
SNOW BEGINNING TO TAPER OFF ACROSS THE AREA THIS MORNING AS WEAK
ISENTROPIC UPGLIDE WE HAD IS SLOWLY FADING AWAY. BEST EVIDENCE OF
THE LOSS OF LIFT WAS THE CONSIDERABLE AMOUNT OF WARMING WE SAW WITH
CLOUD TOP TEMPS BETWEEN 5Z AND 7Z...IR WARMING THESE TWO HOURS
MATCHED UP WELL WITH THE LOSS OF SNOW OBSERVATIONS. THERE WILL BE
ONE MORE POTENTIAL SNOW BAND TO WATCH OUT FOR THIS MORNING FROM
SOUTH CENTRAL MN TOWARD THE EAU CLAIRE AREA. LOOKING BACK OVER THE
ERN NEB/SODAK BORDER...THERE HAS BEEN A BAND OF COOLING CLOUD TOPS
THE LAST COUPLE OF HOURS...WHICH IS ASSOCIATED A SECTION OF THE
H7-H6 FGEN THAT THE RAP SHOWS BECOMING ACTIVE ONCE AGAIN. THIS IS
BEING AIDED BY A SLIGHT LOWERING OF THE TROPOPAUSE LEVEL THAT
EMANATED FROM THE PRIMARY UPPER TROUGH OVER THE ROCKIES LAST NIGHT.
THIS BAND OF FGEN WILL SLIDE EAST THROUGH THE MORNING AND MOST
HI-RES MODELS...ALONG WITH THE 20.00/20.06 NAM12 SHOW ONE LAST BAND
OF SNOW CUTTING ACROSS OR NEAR THE SE CORNER OF THE MPX CWA BETWEEN
ABOUT 14Z AND 18Z.
THE BIGGER QUESTION FOR TODAY THOUGH IS WHAT WILL HAPPEN WITH THE
CLOUD COVER. SEEING SOME CONFLICTING TRENDS WITH THE CLOUD COVER
EARLY THIS MORNING...WHICH IS HELPING MAKE THE CLOUD FORECAST RATHER
DIFFICULT. A VERY DRY HIGH PRESSURE OF CONTINENTAL POLAR ORIGIN IS
CURRENTLY CENTERED FROM CENTRAL SODAK INTO NORTH CENTRAL MN. WITHIN
THIS HIGH WE ARE SEEING CLOUD HEIGHTS INCREASE OR EVEN CLEAR OUT
ACROSS CENTRAL MN...BUT BENEATH THE RIDGE OVER SODAK...THEY HAVE
BEEN EXPANDING THE LAST FEW HOURS. OVER SRN MN...THE CLOUDS HAVE
FINALLY BEGUN TO LOWER AS SLIGHTLY MORE MOIST AIR HAS BEEN PUSHED
NORTH OF THE STALLED OUT BOUNDARY THAT SITS FROM NE OKLAHOMA INTO
SRN MICH. THE MODELS SHOW PLENTY OF LOW LEVEL MOISTURE HANGING
AROUND THROUGH THE DAY...INDICATING A MOSTLY CLOUDY DAY IS IN
STORE...BUT SUSPECT THAT DRIER AIR OVER NRN MN WILL HELP KEEP THE
CLOUDS THINNER ACROSS NRN PORTIONS OF THE AREA. THE NAM/GFS SHOW
EVEN THE LOW LEVEL MOISTURE STARTING TO EVACUATE WRN MN
TONIGHT...WITH MOSTLY CLEAR SKIES WORKING INTO THE WEST LATE. IF
THIS HAPPENS...WE WILL PROBABLY HAVE TO TREND LOWS TONIGHT IN THE
WEST CLOSER TO THE COOL END OF GUIDANCE...WHICH SHOWS LOWS DROPPING
BACK DOWN INTO THE TEENS BELOW ZERO IN THE WEST AS IS SEEN WITH
GEM/ECMWF/NAM.
AS FOR THE MOISTURE AHEAD OF THE BOUNDARY TO OUR SOUTHEAST...IT IS
QUITE IMPRESSIVE. LOW LEVEL AIR TRAJECTORIES SHOW THAT THE AIR IN
THE WARM SECTOR OF THE SYSTEM TO OUR SOUTH CAN BE TRACED BACK TO NOT
JUST THE GULF OF MEXICO...BUT CLEAR DOWN INTO THE NRN CARIBBEAN AND
BACK EAST ACROSS CUBA INTO THE TROPICAL WRN ATLANTIC...HENCE WHY
HISTORIC RAINFALLS ARE EXPECTED IN THE COMING DAYS ACROSS THE OHIO
VALLEY.
.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 400 AM CST FRI DEC 20 2013
THE ARCTIC FRONT WILL OSCILLATE BACK AND FORTH ACROSS THE FORECAST
AREA DURING THE LONGER TERM. THIS WILL OFFER AT LEAST TWO SNOW
EVENTS AS WAVES OF LOW PRESSURE MOVE THROUGH FROM SUNDAY INTO
MONDAY AND THEN FROM TUESDAY INTO WEDNESDAY. SNOW ACCUMULATIONS OF AN
INCH OR TWO ARE POSSIBLE WITH EACH EVENT. FAIRLY STRONG HIGH
PRESSURE WILL FOLLOW EACH OF THESE WAVES. MONDAY MORNING STILL
LOOKS THE COLDEST WITH LOWS FROM NEAR 20 BELOW IN WEST CENTRAL MN
TO AROUND ZERO AT KEAU. COUPLE THIS WITH NORTHWEST WINDS NEAR 10
MPH AND WIND CHILL READINGS COME OUT TO AROUND 35 BELOW ZERO
ACROSS THE WESTERN CWA. HIGHS ON MONDAY WILL LIKELY STAY BELOW
ZERO ACROSS THE WEST WITH SINGLE DIGITS ABOVE ZERO FOR THE TWIN
CITIES AND WEST CENTRAL WI. A NON-DIURNAL TEMPERATURE TREND WAS
THEN INSERTED FOR MONDAY NIGHT ACROSS WEST CENTRAL AND SOUTHWEST
MN AS SOUTHERLY FLOW INCREASES ON THE BACK SIDE OF THE HIGH AS THE
NEXT WAVE OF LOW PRESSURE MOVES INTO THE DAKOTAS. CENTRAL AREAS OF
MN AND WEST CENTRAL WI WILL STILL HAVE A VERY COLD NIGHT WITH LOWS
MONDAY NIGHT FROM 10 BELOW TO 15 BELOW ZERO. THE WAVE OF LOW
PRESSURE ARRIVING ON TUESDAY POSES SOME PRECIP TYPE PROBLEMS FOR
SOUTHWEST MN WITH THE GFS INDICATING SOME POTENTIAL FOR FREEZING
DRIZZLE/FREEZING RAIN. THE ECMWF IS NOT AS AGGRESSIVE WITH THE LOW
LEVEL WARMING...PARTLY BECAUSE THE WHOLE UPPER WAVE IS FARTHER
SOUTH COMPARED TO THE GFS. THE ECMWF HAS DEEPER SATURATION AS
WELL. POPS FOR THE TUESDAY AND WEDNESDAY PERIOD WILL LIKELY NEED
TO BE ADJUSTED UPWARD IF THE POSITION OF THE GFS GETS CLOSER TO
THE ECMWF. POPS WERE EXPANDED AND ADJUSTED UPWARD FOR THE WAVE
FROM SUNDAY INTO MONDAY AS THE NORTHERN STREAM HAS BECOME
STRONGER. THE OTHER PROBLEM ON SUNDAY TO KEEP AN EYE ON IS THE
BLOWING SNOW FROM WEST CENTRAL INTO SOUTH CENTRAL MN. WITH MORE
WIDESPREAD SNOW FORECAST ALONG WITH INCREASING NORTHWEST WINDS AS
THE NEXT SURGE OF ARCTIC PUSHES IN...SOME PRETTY POOR VISIBILITIES
MAY RESULT ACROSS THE MN RIVER VALLEY DURING THE AFTERNOON AND NIGHT.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1209 PM CST FRI DEC 20 2013
THE POTENTIAL FOR MVFR/IFR CLOUDS IS MAKING FOR A TROUBLING
FORECAST THIS AFTERNOON. THE FORECAST MODELS ARE HAVING TROUBLE
WITH THE STAGNANT AIRMASS IN PLACE. BASED ON THE CURRENT
CONDITIONS...AND THE SPORADIC MVFR CIGS ACROSS THE REGION HAVE
TRENDED FOR A MORE PESSIMISTIC FORECAST.
KMSP...
PESKY FLURRIES WILL LINGER FOR A COUPLE OF MORE HOURS...BUT SHOULD
NOT SEE ANY ACCUMULATIONS. AS MENTIONED ABOVE...THE MAIN CONCERN
IS CLOUDS OVERNIGHT...BUT FOR NOW DID NOT HAVE THE CONFIDENCE TO
DROP MSP BELOW 1700FT.
/OUTLOOK FOR KMSP/
SUN...MVFR AND -SN WITH IFR POSSIBLE. WINDS NW AT 15G20KTS.
MON...VFR. WINDS NW AT 5-10KTS.
TUE...VFR WITH MVFR AND -SN POSSIBLE. WIND S AT 15G25KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
SHORT TERM...MPG
LONG TERM...RAH
AVIATION...JRB
AREA FORECAST DISCUSSION...UPDATED
NWS ABERDEEN SD
1138 AM CST FRI DEC 20 2013
.UPDATE...
UPDATED AVIATION DISCUSSION BELOW FOR 18Z TAFS.
MADE SOME CHANGES TO THE FORECAST THIS MORNING...MAINLY TO
INCREASE CLOUD COVER THROUGH THE REST OF THE DAY. SURPRISINGLY
TEMPERATURES HAVE BEEN ABLE WARM AS EXPECTED WITH MANY LOCATIONS
CLIMBING ABOVE ZERO. BASED ON THE RAP HAVE MADE SOME MINOR CHANGES
TO THE HIGH TEMPERATURE TODAY.
&&
.PREVIOUS DISCUSSION...
.SHORT TERM...TODAY THROUGH SUNDAY
THE MODELS SHOW VERY GOOD AGREEMENT THROUGH THE SHORT TERM WITH
COLD NORTHWEST FLOW ALOFT DOMINATING. ABR RADAR WAS SHOWING SOME
WEAK ECHOES EARLY THIS MORNING ALONG WITH FLURRIES REMAINING IN
SOME OBS. THUS...ADDED IN SOME SCATTERED FLURRIES INTO THE
FORECAST. OTHERWISE... ARCTIC HIGH PRESSURE EARLY THIS MORNING
WILL DESCEND SLOWLY SOUTHEAST ACROSS THE REGION TODAY AND THIS
EVENING. WINDS WILL TURN FROM NORTH TO LIGHT SOUTH TO SOUTHWEST
TODAY. WITH THE MOSTLY SUNNY SKIES TODAY/LOW SUN ANGLE OVER FRESH
SNOW COVER ALONG WITH LITTLE WIND...TEMPERATURES WILL STRUGGLE TO
RISE TO TODAY. EXPECT SINGLE DIGITS FOR HIGHS WITH MAYBE SOME
LOWER TEENS SOUTHWEST. WITH LITTLE RISE IN TEMPERATURES TODAY OVER
THE NEW COVER...TEMPERATURES SHOULD FALL QUICKLY THIS EVENING WITH
LITTLE IF ANY CLOUD COVER THROUGH LATE TONIGHT. COULD SEE SOME
TEENS BELOW ZERO EAST IN THE CWA WITH LIGHT SOUTH WINDS. THE
MODELS THEN SHOW GOOD AGREEMENT WITH A SHORT WAVE TROUGH FROM THE
NORTHWEST ALONG WITH ANOTHER ARCTIC BOUNDARY MOVING ACROSS THE
REGION SATURDAY THROUGH SUNDAY. SATURDAY WILL BE ANOTHER COLD DAY
AS MID AND HIGH LEVEL CLOUDS WILL BE SPREADING IN WITH THE NEXT
SYSTEM ALONG WITH A WIND CHANGE TO THE NORTH. DEPENDING ON THE
OVERNIGHT LOWS...TEMPERATURES WILL AGAIN STRUGGLE TO REACH 10 TO
15 DEGREES ACROSS MOST OF THE CWA BY LATE AFTERNOON SATURDAY.
THE MODELS THEN SHOW SOME LIGHT QPF WITH THE SHORT WAVE TROUGH AND
CAA COMING THROUGH SATURDAY NIGHT AND SUNDAY. THIS LOOKS REASONABLE
AND PUT IN SOME POPS FOR THIS TIME PERIOD FOR LIGHT SNOW. ANOTHER
ARCTIC HIGH PRESSURE AREA WILL BUILD INTO THE REGION ON SUNDAY.
AFTER ANOTHER BITTER COLD NIGHT ON SATURDAY NIGHT...TEMPERATURES
IN THE SINGLE DIGITS BELOW ZERO WILL STRUGGLE TO REACH ZERO IN
THE EASTERN CWA WITH ZERO TO 5 ABOVE WEST IN THE CWA ON SUNDAY.
925MB TEMPERATURES WILL FALL TO -18 TO -22C BY 00Z MONDAY. WITH
THE CAA AND 925MB WINDS OF 10 TO 25 KNOTS...WE COULD ALSO HAVE
SOME ADVISORY TYPE WIND CHILLS ON SUNDAY. GENERALLY LOWERED
TEMPERATURES SOME THROUGH THE ENTIRE PERIOD.
.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY
THE EXTENDED IS STILL CHARACTERIZED BY NORTHWEST FLOW AND BELOW
NORMAL COLD AIR. 00Z GLOBAL SPECTRAL MODEL SOLUTIONS WOULD HAVE
ONE BELIEVING THAT SEVERAL PIECES OF S/W ENERGY ARE STILL WORKING
THROUGH THE REGION BETWEEN TUESDAY AND THURSDAY...WITH CHANCES FOR
LIGHT SNOW /LOW ACCUM POTENTIAL/ OFF AND ON ACROSS THE REGION.
TIMING/PLACEMENT DIFFERENCES IN THE MODELS AND SLIGHT DIFFERENCES
IN THERMAL PROGS MADE ACCEPTING THE ALLBLEND GUIDANCE THIS MORNING
AN EASY CHOICE.
&&
.AVIATION...
18Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS
MVFR/IFR CIGS WILL CONTINUE TO AFFECT KABR/KATY THROUGH THE
AFTERNOON HOURS. EXPECTING TO SEE THESE CIGS ERODE/MOVE OUT OF
KABR BY LATE AFTERNOON AND OUT OF KATY BY LATER THIS EVENING.
OVERNIGHT...MOSTLY VFR CONDITIONS ARE FORECAST AT THIS TIME...BUT
UNFORTUNATELY NOT A LOT OF CONFIDENCE IN THIS. THERE ARE SOME
SUGGESTIONS THAT PATCHES OF MVFR CIGS COULD BE AFFECTING THE
AREA...AND CANNOT COMPLETELY RULE OUT FG/BR OVERNIGHT AS WELL.
WITH THE LOW CONFIDENCE...HAVE NOT INCLUDED IN TAFS AT THIS TIME
AND WILL CONTINUE TO MONITOR.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
UPDATE...SD/TMT
SHORT TERM...MOHR
LONG TERM...DORN
AVIATION...TMT
WEATHER.GOV/ABERDEEN
AREA FORECAST DISCUSSION...UPDATED
NWS ABERDEEN SD
1059 AM CST FRI DEC 20 2013
.UPDATE...
MADE SOME CHANGES TO THE FORECAST THIS MORNING...MAINLY TO
INCREASE CLOUD COVER THROUGH THE REST OF THE DAY. SURPRISINGLY
TEMPERATURES HAVE BEEN ABLE WARM AS EXPECTED WITH MANY LOCATIONS
CLIMBING ABOVE ZERO. BASED ON THE RAP HAVE MADE SOME MINOR CHANGES
TO THE HIGH TEMPERATURE TODAY.
&&
.PREVIOUS DISCUSSION...
.SHORT TERM...TODAY THROUGH SUNDAY
THE MODELS SHOW VERY GOOD AGREEMENT THROUGH THE SHORT TERM WITH
COLD NORTHWEST FLOW ALOFT DOMINATING. ABR RADAR WAS SHOWING SOME
WEAK ECHOES EARLY THIS MORNING ALONG WITH FLURRIES REMAINING IN
SOME OBS. THUS...ADDED IN SOME SCATTERED FLURRIES INTO THE
FORECAST. OTHERWISE... ARCTIC HIGH PRESSURE EARLY THIS MORNING
WILL DESCEND SLOWLY SOUTHEAST ACROSS THE REGION TODAY AND THIS
EVENING. WINDS WILL TURN FROM NORTH TO LIGHT SOUTH TO SOUTHWEST
TODAY. WITH THE MOSTLY SUNNY SKIES TODAY/LOW SUN ANGLE OVER FRESH
SNOW COVER ALONG WITH LITTLE WIND...TEMPERATURES WILL STRUGGLE TO
RISE TO TODAY. EXPECT SINGLE DIGITS FOR HIGHS WITH MAYBE SOME
LOWER TEENS SOUTHWEST. WITH LITTLE RISE IN TEMPERATURES TODAY OVER
THE NEW COVER...TEMPERATURES SHOULD FALL QUICKLY THIS EVENING WITH
LITTLE IF ANY CLOUD COVER THROUGH LATE TONIGHT. COULD SEE SOME
TEENS BELOW ZERO EAST IN THE CWA WITH LIGHT SOUTH WINDS. THE
MODELS THEN SHOW GOOD AGREEMENT WITH A SHORT WAVE TROUGH FROM THE
NORTHWEST ALONG WITH ANOTHER ARCTIC BOUNDARY MOVING ACROSS THE
REGION SATURDAY THROUGH SUNDAY. SATURDAY WILL BE ANOTHER COLD DAY
AS MID AND HIGH LEVEL CLOUDS WILL BE SPREADING IN WITH THE NEXT
SYSTEM ALONG WITH A WIND CHANGE TO THE NORTH. DEPENDING ON THE
OVERNIGHT LOWS...TEMPERATURES WILL AGAIN STRUGGLE TO REACH 10 TO
15 DEGREES ACROSS MOST OF THE CWA BY LATE AFTERNOON SATURDAY.
THE MODELS THEN SHOW SOME LIGHT QPF WITH THE SHORT WAVE TROUGH AND
CAA COMING THROUGH SATURDAY NIGHT AND SUNDAY. THIS LOOKS REASONABLE
AND PUT IN SOME POPS FOR THIS TIME PERIOD FOR LIGHT SNOW. ANOTHER
ARCTIC HIGH PRESSURE AREA WILL BUILD INTO THE REGION ON SUNDAY.
AFTER ANOTHER BITTER COLD NIGHT ON SATURDAY NIGHT...TEMPERATURES
IN THE SINGLE DIGITS BELOW ZERO WILL STRUGGLE TO REACH ZERO IN
THE EASTERN CWA WITH ZERO TO 5 ABOVE WEST IN THE CWA ON SUNDAY.
925MB TEMPERATURES WILL FALL TO -18 TO -22C BY 00Z MONDAY. WITH
THE CAA AND 925MB WINDS OF 10 TO 25 KNOTS...WE COULD ALSO HAVE
SOME ADVISORY TYPE WIND CHILLS ON SUNDAY. GENERALLY LOWERED TEMPERATURES
SOME THROUGH THE ENTIRE PERIOD.
.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY
THE EXTENDED IS STILL CHARACTERIZED BY NORTHWEST FLOW AND BELOW
NORMAL COLD AIR. 00Z GLOBAL SPECTRAL MODEL SOLUTIONS WOULD HAVE
ONE BELIEVING THAT SEVERAL PIECES OF S/W ENERGY ARE STILL WORKING
THROUGH THE REGION BETWEEN TUESDAY AND THURSDAY...WITH CHANCES FOR
LIGHT SNOW /LOW ACCUM POTENTIAL/ OFF AND ON ACROSS THE REGION.
TIMING/PLACEMENT DIFFERENCES IN THE MODELS AND SLIGHT DIFFERENCES
IN THERMAL PROGS MADE ACCEPTING THE ALLBLEND GUIDANCE THIS MORNING
AN EASY CHOICE.
&&
.AVIATION...
12Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS
WELL...THE SNOW HAS PRETTY MUCH ENDED...BUT AFTER INITIAL CLEARING
LATE LAST EVENING...A SCT-BKN MVFR DECK OF STRATUS DEVELOPED AND
HAS BEEN SLOW TO MOVE/DISSIPATE ACROSS THE FORECAST AREA. IN
FACT...SOME AREAS BENEATH THESE NEWLY DEVELOPED STRATUS CLOUDS
HAVE SEEN AN OCCASIONAL SNOW FLURRY EARLY THIS MORNING. VFR AND
MVFR SCT TO OVC STRATUS CLOUDS WILL CONTINUE TO TAKE TURNS IN
SURFACE OBS FOR THE NEXT FEW HOURS. BUT...ULTIMATELY...STRATUS
CLOUDS SHOULD SCATTER OUT BY LATE THIS MORNING LEAVING...DECENT
VFR FLYING WEATHER WITH LIGHT WINDS FOR THE REST OF FRIDAY.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
UPDATE...SD
SHORT TERM...MOHR
LONG TERM...DORN
AVIATION...DORN
WEATHER.GOV/ABERDEEN
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
411 PM CST FRI DEC 20 2013
.DISCUSSION...
21Z SUBJECTIVE SURFACE ANALYSIS SHOWED A STRONG COLD FRONT IN
PLACE ALONG A LINE FROM PARIS TO DALLAS TO HAMILTON. THE
TEMPERATURE GRADIENT ALONG THIS BOUNDARY WAS QUITE IMPRESSIVE WITH
A 70 DEGREE TEMPERATURE THAT WAS OBSERVED AT GREENVILLE...A 49
DEGREE TEMPERATURE AT MCKINNEY AND A 39 DEGREE TEMPERATURE AT
DENTON. THIS FRONT WAS STILL MOVING SOUTHEAST AT 15 MPH AT THE
TIME OF THIS DISCUSSION. A 20Z AIRPLANE SOUNDING FROM DALLAS LOVE
FIELD INDICATED THAT THE FRONT WAS SHALLOW IN NATURE...WITH THE
FRONTAL INVERSION ONLY EXTENDING UP ABOUT 1500 FEET ABOVE GROUND
LEVEL. THE FRONT IS STILL EXPECTED TO STALL OUT OVER THE FAR
SOUTHEASTERN CWA THIS EVENING...IN RESPONSE TO CYCLOGENESIS
INITIATED BY THE APPROACH OF A POWERFUL UPPER LEVEL STORM SYSTEM.
THIS UPPER LEVEL STORM SYSTEM WAS OBSERVED OVER BAJA CALIFORNIA AT
20Z BASED ON WATER VAPOR SATELLITE IMAGERY. OUT AHEAD OF THIS
UPPER LEVEL STORM SYSTEM...WATER VAPOR SATELLITE IMAGERY SHOWED A
NICE CONTINUOUS BAND OF SUB-TROPICAL PACIFIC MOISTURE STREAMING
NORTHEAST OVER NORTHERN MEXICO AND THE SOUTH PLAINS. THE HIGH
TERRAIN OF NORTHERN MEXICO WILL SCOUR OUT ALL OF THE LOW TO MID-
TROPOSPHERIC MOISTURE ASSOCIATED WITH THIS SUBTROPICAL PLUME...BUT
THE MID TO UPPER LEVEL MOISTURE WILL CONTRIBUTE TO MOISTURE DEPTH
OVER THE REGION AS THE UPPER LEVEL STORM SYSTEM MOVES ACROSS THE
AREA TONIGHT INTO TOMORROW MORNING.
THROUGH TONIGHT...THE MOST TROUBLESOME FORECAST PROBLEM IN THE
SHORT TERM FORECAST IS THAT ALL FORECAST GUIDANCE IS DOING A
REMARKABLY POOR JOB RESOLVING THE STRENGTH OF THE SHALLOW COLD AIR
ASSOCIATED WITH/BEHIND THE COLD FRONT. WHILE ALL GUIDANCE IS DOING
A POOR JOB RESOLVING SURFACE TEMPERATURES NORTH OF THE COLD
FRONT...THE RAP IN PARTICULAR IS DIFFICULT TO PROCESS BECAUSE IT
CONTINUES TO INITIALIZE THE COLD AIR...BUT PERSISTENTLY BRINGS
SURFACE TEMPERATURES UP 5-7 DEGREES AT FORECAST HOUR 1 DESPITE
PERSISTENT COLD AIR ADVECTION AND CLOUD COVER. THIS WOULD BE MORE
OR LESS A NUISANCE IF THE TEMPERATURES HAD NO POTENTIAL TO HAVE AN
IMPACT ON PRECIPITATION TYPE IN THIS FORECAST. FOR INSTANCE...AT
BOWIE...THE 21Z OBSERVATION HAD A TEMPERATURE OF 32 DEG F. THE RAP
INITIALIZES THIS AT 34 DEGREES...WHICH IS NOT TOO FAR OFF...BUT
THEN GOES AHEAD TO FORECAST A TEMPERATURE OF 40 DEGREES BY 22Z.
WITH WIDESPREAD RAINFALL DEVELOPING OVER THE REGION RIGHT
NOW...AND EXPECTED TO PERSIST THIS EVENING INTO THE OVERNIGHT
HOURS...THIS ERROR IN RESOLVING NEAR SURFACE TEMPERATURES IS QUITE
PROBLEMATIC. THEREFORE...AT THIS TIME...WITH NO GUIDANCE AVAILABLE
ACTUALLY RESOLVING THE STRENGTH OF THIS COLD AIR...THE
PRECIPITATION TYPE FORECAST FOR TONIGHT WAS COMPLETED USING
OBSERVATIONAL TRENDS...RECENT FORECAST EVENTS AND INTUITION.
AT THIS TIME EXPECT THAT TEMPERATURES ALONG AND NORTHWEST OF A
GAINESVILLE TO GRAHAM LINE ARE MOST LIKELY TO FALL TO 32 DEGREES
THIS EVENING...LIKELY HOLDING STEADY THROUGH MUCH OF THE OVERNIGHT
HOURS. AS A RESULT...EVEN IF WE SEE RAIN AT 31 TO 32 DEGREES FOR
SEVERAL HOURS...THE CURRENT THINKING IS THAT WE WILL NOT SEE ANY
ICE ACCUMULATION...EXCEPT PERHAPS ON TREE TOPS OR THE TOPS OF
EXPOSED METAL SURFACES. THE REASONS FOR THIS ARE AS FOLLOWS:
1. BEFORE THE FRONT...WE HAVE EXPERIENCED A FEW DAYS OF ABOVE
NORMAL TEMPERATURES. GROUND/ROAD TEMPERATURES ARE WELL ABOVE
FREEZING WHICH WILL NOT ALLOW FOR ICE ACCUMULATION.
2. THE DEPTH OF THE ELEVATED WARM LAYER IS ALMOST 8 TIMES AS DEEP
AS THE DEPTH OF THE COLD/SUB-FREEZING LAYER. RAIN FALLING IN THIS
ENVIRONMENT WILL LIKELY HAVE A TEMPERATURE ABOVE FREEZING WHEN IT
REACHES THE SURFACE. THAT IS THE TEMPERATURE OF THE FALLING RAIN
DROPS ARE LIKELY TO BE ABOVE FREEZING...THIS IS ALSO NOT CONDUCIVE
TO ICE ACCUMULATION.
3. ALL GUIDANCE INDICATES PERSISTENT WARM AIR ADVECTION THROUGH
12Z SATURDAY ABOVE THE COLD FRONTAL INVERSION. THE WARM LAYER IS
VERY LIKELY TO MAINTAIN ITS DEPTH AND STRENGTH...WHILE RELATIVELY
WARM RAIN DROPS MAY ACTUALLY SHRINK THE DEPTH OF THE SHALLOW COLD
AIR OVERNIGHT.
AS A RESULT...WILL NOT BE HIGHLIGHTING FREEZING RAIN IN THE
FORECAST AT THIS TIME...DESPITE THE SURFACE OBSERVATION AT BOWIE
AT 32 DEGREES SEEMINGLY SHOWING AN ICE STORM ON OUR DOORSTEP. IT
LOOKS LIKE THE DEPTH OF THE COLD AIR WILL ONLY SUPPORT ICE
ACCUMULATION FARTHER NORTH...WELL INTO OKLAHOMA BASED ON
OBSERVATIONAL ANALYSIS AND DFW AREA AIRCRAFT SOUNDINGS.
DESPITE ALL THAT HAS BEEN DISCUSSED ABOUT THE SHALLOW COLD AIR
PROBLEM...THERE WERE ACTUALLY NO SIGNIFICANT CHANGES MADE TO THE
PREVIOUS FORECAST WHICH REMAINS LARGELY ON TRACK. THE BAJA UPPER
LEVEL LOW IS STILL EXPECTED TO MOVE OVER THE SOUTH PLAINS TOMORROW
MORNING...SPREADING STRONG LARGE SCALE FORCING FOR ASCENT OVER THE
REGION TONIGHT THROUGH TOMORROW MORNING. NEARLY ALL GUIDANCE
INDICATES THAT THE UPPER LOW WILL BECOME INCREASINGLY NEGATIVELY
TILTED AS IT MOVES OUT OVER TEXAS...DEEPENING AS IT MOVES OVER THE
CWA. THE STRONGEST FORCING FOR ASCENT LOOKS TO MOVE OVER THE CWA
IN THE 09 TO 15Z TIME FRAME...WHICH SHOULD ALSO REPRESENT OUR
WINDOW FOR THE BEST COVERAGE AND HEAVIEST PRECIPITATION RATES
DURING THIS EVENT.
FOR THIS EVENING...THE COLD FRONT PUSHING SOUTH THROUGH MOST OF
THE CWA WILL SIMPLY HELP TO STEEPEN LOW-LEVEL ISENTROPIC SURFACES
AS CYCLOGENESIS RAMPS UP NEAR DEL RIO RESULTING IN AN INCREASE OF
THE STRENGTH OF THE LOW TO MID-LEVEL WIND FIELD. THIS SHOULD
RESULT IN A SPREAD OF THE COVERAGE OF ONGOING RAIN SHOWER
ACTIVITY FROM WEST TO EAST ACROSS THE CWA. AS THE UPPER LEVEL LOW
APPROACHES...ASSUMING IT BECOMES MORE NEGATIVELY TILTED AS
ADVERTISED...WE SHOULD SEE AN ENHANCEMENT OF MID-LEVEL LAPSE RATES
WITH SOME UPPER-LEVEL COLD AIR ADVECTION OVER THE PERSISTENT LOW-
LEVEL WARM AIR ADVECTION REGIME. THIS WILL RESULT IN AN INCREASED
CHANCE OF ISOLATED THUNDERSTORMS EMBEDDED IN THE RAIN SHOWER
ACTIVITY FROM SUNSET TO MIDNIGHT. ALL OF THIS ACTIVITY SHOULD
REMAIN ELEVATED IN NATURE...AND POSES VERY LITTLE SEVERE WEATHER
THREAT AS A RESULT. RAINFALL RATES WILL BE ENHANCED...AND
THEREFORE SOME LOCALIZED HEAVY RAINFALL IS POSSIBLE.
AFTER MIDNIGHT...AS MENTIONED ABOVE...THE BEST LARGE SCALE FORCING
FOR ASCENT IS EXPECTED TO BUILD ACROSS THE CWA FROM WEST TO EAST
DURING THIS TIME RESULTING IN THE STRONGEST AND MOST WIDESPREAD
CONVECTION AND PRECIPITATION FOR THE REGION. BASED ON THE POSITION
OF THE COLD FRONT AT THAT TIME...WE DO HAVE A WINDOW FOR SURFACE
BASED SEVERE STORMS BASED ON CONVECTIVE PARAMETERS ADVERTISED IN
THE MAJORITY OF GUIDANCE. LOCATIONS ALONG AND SOUTHEAST OF
WHEREVER THE COLD FRONT STALLS OUT WOULD BE THE ONLY LOCATIONS
WHERE SURFACE BASED SEVERE STORMS WOULD BE POSSIBLE. FORECAST
CONVECTIVE PARAMETERS INDICATED SURFACE BASED CAPE VALUES OF
AROUND 1000 J/KG WITH 0-3 KM CAPE VALUES OF AROUND 100 J/KG AND
DEEP LAYER SHEAR VALUES IN EXCESS OF 50 KTS.
THESE VALUES ARE SUPPORTIVE OF A LOW-TOPPED SUPER CELLULAR STORM
MODE...WHICH COULD RESULT IN LARGE HAIL...DAMAGING WIND OR
ISOLATED TORNADOES. THIS THREAT IS MODERATED BY STRONG FORCING
WHICH MAY MAKE AN ISOLATED STORM MODE DIFFICULT TO REALIZE...AND
STRONG CLOUD LEVEL WINDS THAT WILL LIKELY TAKE STORMS THAT DEVELOP
ALONG THE FRONT...OVER/NORTH OF THE FRONT SHORTLY AFTER
INITIATION. REGARDLESS...WILL BE WATCHING FOR WHERE THE FRONT
STALLS OUT TONIGHT AS LOCATIONS NEAR AND TO THE SOUTHEAST OF THE
BOUNDARY ARE THE MOST LIKELY TO SEE SEVERE WEATHER. FURTHER
NORTHWEST...STRONG STORMS REMAIN POSSIBLE...HOWEVER EVEN ELEVATED
SUPERCELLS ARE ONLY GOING TO PROVIDE A THREAT FOR MARGINALLY
SEVERE HAIL...SO THE OVERALL SEVERE WEATHER THREAT NORTHWEST OF
THE FRONT DIMINISHES GREATLY.
FOR ANYWHERE ACROSS NORTH TEXAS...LOCALLY HEAVY RAINFALL IS
POSSIBLE WHICH MAY RESULT IN SOME LOCALIZED FLASH FLOODING ISSUES
OVER THE NEXT 24 HRS. WITH THE SUB-TROPICAL PACIFIC MOISTURE FEED
IN PLACE...AND LOW-LEVEL WARM MOIST ADVECTION EXPECTED TO RAMP UP
IN INTENSITY OVER THE SHALLOW COLD FRONT...NEARLY ALL GUIDANCE
INDICATES THAT PWAT VALUES WILL BE UP AROUND 1.5 INCHES ACROSS
NORTH AND CENTRAL TEXAS AS THE UPPER LOW SPREADS STRONG FORCING
OVER THE REGION. 1.5 INCH PRECIPITABLE WATER VALUES RANK AS PLUS 3
STANDARD DEVIATION FOR NORTH TEXAS AT THIS TIME OF YEAR. THIS
EXCEPTIONALLY DEEP MOISTURE COMBINED WITH FAVORABLE DYNAMICS FOR
WIDESPREAD PRECIPITATION SUPPORT A LOCALIZED HEAVY RAINFALL THREAT
WITH AN ATTENDANT LOCALIZED FLOODING THREAT TONIGHT INTO TOMORROW
MORNING. DID NOT ISSUE A FLASH FLOOD WATCH AT THIS TIME BECAUSE
OUR PRIMARY WINDOW FOR HEAVY RAINFALL IS ONLY EXPECTED TO BE ON
THE ORDER OF 6 HOURS OR SO. IF STRONG FORCING WAS EXPECTED TO BE
IN PLACE FOR A LONGER PERIOD OF TIME...THE THREAT OF WIDESPREAD
FLOODING WOULD BE MUCH GREATER AND A WATCH WOULD HAVE BEEN ISSUED.
AT THIS TIME THE THREAT OF FLOODING IS EXPECTED TO REMAIN
LOCALIZED AND MAINLY CONFINED TO LOW LYING/COMMONLY FLOODED AREAS.
HEAVY PRECIPITATION IS EXPECTED TO COME TO AN END FROM SOUTHWEST
TO NORTHEAST SATURDAY AFTERNOON AS A STRONG MID-LEVEL DRY SLOT
PUNCHES OVER THE REGION. LIGHT RAIN MAY PERSIST ACROSS THE AREA
SATURDAY AFTERNOON...BUT EVEN THIS WILL BE SCOURED OUT BY SUNSET.
REMAINDER OF THE FORECAST...NO SIGNIFICANT CHANGES WERE MADE TO
THE PREVIOUS FORECAST AS MOST OF THE ACTIVITY IN THE FORECAST IS
IN THE FIRST 24 HOURS. HIGHLIGHTS OF THE REMAINDER OF THE FORECAST
INCLUDE:
1. ADDED A MENTION OF SPRINKLES/LIGHT RAIN TO THE FORECAST ALONG
THE COLD FRONT THAT IS EXPECTED TO PUSH SOUTH THROUGH THE CWA ON
SUNDAY MORNING. WILL HAVE TO WATCH TEMPERATURES CLOSELY SUNDAY
MORNING AS THIS FRONT ROLLS THROUGH...HOWEVER ALL GUIDANCE
INDICATES TEMPERATURES JUST ABOVE FREEZING WITH THIS VERY LIGHT
PRECIPITATION.
2. WE SHOULD BE DRY EARLY NEXT WEEK...LEADING UP TO CHRISTMAS DAY.
TEMPERATURES WILL SLOWLY WARM THROUGH CHRISTMAS...ALTHOUGH HIGHS
ARE EXPECTED TO REMAIN BELOW NORMAL THROUGH THE WEEK AHEAD.
3. AN UPPER LEVEL STORM SYSTEM MAY RESULT IN SCATTERED RAIN
SHOWERS ACROSS THE REGION ON CHRISTMAS DAY. AT THIS TIME
TEMPERATURES ARE EXPECTED TO BE WELL ABOVE FREEZING...SO NO
SIGNIFICANT IMPACTS ARE EXPECTED AT THIS TIME.
CAVANAUGH
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 37 47 36 48 29 / 100 100 10 10 5
WACO, TX 42 62 37 50 30 / 80 100 10 10 5
PARIS, TX 41 45 36 47 26 / 100 100 10 10 10
DENTON, TX 37 44 34 47 26 / 100 100 10 10 5
MCKINNEY, TX 38 44 35 46 25 / 100 100 10 10 5
DALLAS, TX 38 46 38 48 30 / 100 100 10 10 5
TERRELL, TX 41 47 37 47 28 / 100 100 10 10 5
CORSICANA, TX 46 54 39 48 30 / 80 100 10 10 5
TEMPLE, TX 46 63 39 52 31 / 80 100 10 10 5
MINERAL WELLS, TX 36 49 34 48 24 / 100 90 10 10 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
/
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
305 PM CST FRI DEC 20 2013
.SHORT TERM...(TONIGHT THROUGH SATURDAY NIGHT)
ISSUED AT 305 PM CST FRI DEC 20 2013
MAIN FORECAST CONCERNS THIS PACKAGE...-FZDZ/-SN LATE THIS
AFTERNOON...IMPENDING WINTER STORM MOVING IN SATURDAY NIGHT.
18Z DATA ANALYSIS HAD LOW PRESSURE OVER CENTRAL IL/NORTHERN INDIANA
ALONG THE FRONTAL BOUNDARY...WITH A TROUGH BACK TO NEAR KFSD. WEAK
SHORTWAVES CONTINUED TO RIPPLE THRU THE WEST-SOUTHWEST FLOW ALOFT
OVER THE REGION. THIS COMBINED WITH SOME WEAK 925-700MB WARM
ADVECTION/ISENTROPIC LIFT CONTINUED TO PRODUCE SOME LIGHT RADAR
REFLECTIVITY RETURNS AND SCATTERED SFC OBS WITH VERY LIGHT SNOW.
SOME MIXED/FREEZING PRECIP TYPES OVER EASTERN IA INTO FAR SOUTHERN
WI/NORTHERN IL WHERE THERE WAS ABOVE 0C AIR ALOFT OR LOWER MOISTURE
WAS TOO SHALLOW FOR ICE IN THE CLOUDS.
NO SIGNIFICANT ERRORS NOTED WITH 20.12Z MODEL INITIALIZATIONS.
SOLUTIONS VERY SIMILAR FOR THE AREA TONIGHT/SAT...THEN DIVERGE WITH
THE ARRIVE/AMOUNT OF SNOW SAT NIGHT. NAM NOW FASTEST/MOST ROBUST/
FURTHEST NORTHWEST WITH THE SYSTEM...GFS SLOWER/DRIER WITH CAN
GEM/ECMWF IN THE MIDDLE. ENOUGH DIFFERENCES THAT GFS KEEPS THE FCST
AREA DRY THRU 06Z SUN WHILE NAM SPREADS SNOW ACROSS NEARLY THE
ENTIRE FCST AREA BY THAT TIME. CHECK OF OBS VS. MODEL DATA AT 18Z
SHOWED ALL TO BE REASONABLE WITH THE CENTRAL CONUS MASS FIELDS.
MODELS ALSO DOING A DECENT JOB WITH THE LIGHT PRECIP ACROSS THE
REGION. PER WV IMAGERY...MODELS ALL APPEAR GOOD WITH THE SHORTWAVE
FEATURES OVER NOAM/EASTERN PAC. NO ONE REASON TO FAVOR ONE MODEL
OVER THE OTHER AND FAVORED THE MODEL/COMPROMISE...WHICH IS SIMILAR
TO THE ECMWF/CAN GEM THIS CYCLE. SHORT TERM FCST CONFIDENCE GOOD
TONIGHT/SAT THEN AVERAGE SAT NIGHT GIVEN THE MODEL DIFFERENCES.
IN THE SHORT TERM...WEAK LOWER LEVEL WARM ADVECTION/ISENTROPIC LIFT
MOVES EAST/SOUTH OF THE FCST AREA LATE THIS AFTERNOON WITH WHAT
SHOULD BE A QUICK END TO THE LIGHT PRECIP THIS EVENING. HOWEVER...
DID CONTINUE WITH SOME SMALL -ZL/-SN CHANCES OVER MAINLY THE EAST
HALF OF THE FCST AREA INTO THE EARLY EVENING AS A COUPLE OF THE HI-
RES MODELS PRODUCE SOME SPOTTY/LIGHT QPF IN THE 00-03Z PERIOD. SHORT-
TERM FORECASTER HAS ALREADY EXTENDED THE FREEZING RAIN ADVISORY TO
00Z ACROSS THE SOUTHEAST END OF THE FCST AREA WHERE REPORTS INDICATE
FREEZING DRIZZLE CONTINUES TO BE AN ISSUE. SFC-850MB GRADIENT
REMAINS ON THE LIGHT SIDE TONIGHT...WITH LITTLE IN THE WAY OF
ADVECTION TO MOVE THE LOWER LEVEL MOISTURE/CLOUDS OUT OF THE AREA.
CLOUDS REMAIN STUCK OVER THE ARE THRU SAT...AND WILL HAVE A MUTING
EFFECT ON THE DIURNAL TEMP RANGE TONIGHT/SAT.
MODEL DIFFERENCES SAT NIGHT HAVE AN IMPACT ON THE SENSIBLE WEATHER.
12Z NAM WAS FASTEST FURTHEST NORTHWEST WITH THE QPF/SNOW AS THE MID
LEVEL TROUGH/SHORTWAVE LIFTS INTO THE REGION SAT NIGHT...AS IT IS
FURTHER NORTHWEST WITH THE WAVE AND 500-300MB PV ADVECTION AHEAD OF
IT. 20.18Z NAM HAS COME MORE IN LINE WITH ECMWF/CAN-GEM CONSENSUS.
MAIN LOWER LEVEL THERMO-DYNAMIC FORCING/DEFORMATION BAND OF LIFT IS
ACTUALLY RATHER CONSISTENT AMONG THE MODELS...MAINLY CLIPPING THE
SOUTHWEST END OF THE FCST AREA. DEEPEST LIFT PASSES MAINLY ACROSS
AREAS SOUTH OF A KOLZ-KPDC-KDLL LINE. NORTH OF THIS LINE...FORCING/
LIFT PROGGED TO MAINLY AT/ABOVE 700MB...NOT CONDUCIVE TO HIGH SNOW-
WATER RATIOS AND HEAVY SNOW. WHERE CONFIDENCE REMAINS HIGHEST AND
MODELS PAINT 1/4 TO 1/2 INCH PLUS OF QPF...WITH SNOW-WATER RATIOS IN
THE 15 TO 1 RANGE AND 4 TO 8 INCHES OF SNOW POSSIBLE...WILL UPGRADE
THE WATCH TO WARNING FOR GRANT/ CRAWFORD/RICHLAND AND CLAYTON
COUNTIES. WILL LEAVE WATCH FOR THE REMAINING COUNTIES FOR NOW DUE
SOME UNCERTAINTY WITH THE SFC-MID LEVEL TROUGH TRACK AND QPF IS
MAINLY 1/4 INCH OR LESS. IN TIME THESE WATCH COUNTIES PLUS A FEW
MORE ALONG/SOUTHEAST OF A TOMAH WI TO DECORAH AND NEW HAMPTON IA
LINE LIKELY TO NEED A WINTER WEATHER ADVISORY. STILL PLENTY OF TIME
FOR THAT AND CHANCE TO LOOK AT A COUPLE MORE MODEL RUNS...WHICH
HOPEFULLY CONVERGE ON A TIGHTER CONSENSUS. GENERALLY MADE ONLY MINOR
CHANGES TO THE FCST GRIDS FOR TONIGHT THRU SAT NIGHT. MODEL/ENSEMBLE
CONSENSUS LOWS/HIGHS FOR THESE PERIODS QUITE REASONABLE.
.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 305 PM CST FRI DEC 20 2013
MAIN FORECAST CONCERNS FOR SUNDAY THRU MONDAY NIGHT...WINTER STORM
CONTINUING SUNDAY...LINGERING -SN/FLURRY CHANCES SUN NIGHT THRU MON
NIGHT.
20.12Z MODELS IN RATHER GOOD AGREEMENT FOR THE SHORTWAVE OVER
IA/IL/MO AT 12Z SUN TO BE IN QUEBEC BY 00Z MONDAY AND RATHER
SHARP/DEEP COLD CORE TROUGHING TO BE OVER THE REGION SUN NIGHT INTO
MON NIGHT. SOME MODEL DIFFERENCES ON HOW QUICKLY THIS TROUGH MOVES
EAST OF THE REGION MON NIGHT BUT MODEL CONSENSUS IS IMPROVING AND
FAVORS A COMPROMISE OF THE PREVIOUS RUNS. FCST CONFIDENCE THIS
PERIOD IS AVERAGE TO GOOD.
WITH THE FAST MOVEMENT OF THE MID LEVEL TROUGH SUNDAY...LOWER LEVEL
THERMO-DYNAMIC FORCING AND DYNAMIC LIFT/DIVERGENCE ALOFT MOVES
QUICKLY EAST OF THE AREA. CARRIED HIGHEST SNOW CHANCES SUN MORNING
OVER THE SOUTHEAST HALF OF THE FCST AREA. THE NORTHERN STREAM
SHORTWAVE DROPS TOWARD THE AREA FOR THE AFTERNOON...WITH ANOTHER
ROUND OF 500-300MB PV ADVECTION OVER THE TOP OF DEEP CYCLONIC
FLOW...AN INVERTED SFC TROUGH AND PLENTY OF SFC-700MB MOISTURE.
RAISED -SN CHANCES INTO THE 40-60 PERCENT RANGE...HIGHEST OVER THE
NORTHEAST SIDE OF THE FCST AREA. NOT EXPECTING MUCH FOR SNOW
ACCUMULATIONS SUN AFTERNOON...BUT APPEARS THERE WILL BE SOME SNOW IN
THE AIR ALONG WITH NORTHWEST WINDS OF 10-20MPH GUSTING 20-30 MPH FOR
SOME BLOWING/DRIFTING SNOW. WINTER STORM WATCH/WARNING HEADLINES TO
00Z MON STILL LOOK GOOD.
THE SFC THRU MID LEVEL TROUGH PIVOTS OVER THE AREA SUN NIGHT...WITH
DEEP CYCLONIC FLOW AND COLD ADVECTION TO PUT THE SQUEEZE ON THE
MOISTURE IN THE COLUMN. -SN/FLURRIES TO CONTINUE OVER MUCH OF THE
AREA SUN NIGHT AND RAISED PRECIP CHANCES MOSTLY INTO THE 15-40
PERCENT RANGE...AGAIN HIGHEST OVER THE NORTHEAST SIDE OF THE FCST
AREA. WITH THE DEEP/COLD MID LEVEL TROUGH OVER THE AREA YET
MON...CONTINUED SMALL -SN CHANCES FOR MUCH OF THE AREA MON. TROUGH
AXIS MOVES EAST OF THE AREA MON NIGHT WITH COLD SFC HIGH PRESSURE
BUILDING IN. A COUPLE OF COLDER NIGHTS SUN/MON WITH 925MB TEMPS IN
THE -14C TO -20C RANGE AT 12Z MON/TUE. CLOUDS/BOUNDARY LAYER WINDS
SHOULD KEEP LOWS FROM BOTTOMING OUT TOO FAR SUN NIGHT. HOWEVER SOME
CLEARING EXPECTED MON NIGHT WITH LIGHT WINDS UNDER THE SFC RIDGE
AXIS. LOWS MON NIGHT TRENDING TO THE -10F TO -15F RANGE. USED A
MODEL/ENSEMBLE BLEND FOR HIGHS/LOWS IN THE SUN-MON NIGHT PERIOD.
FOR TUESDAY THRU FRIDAY.../DAYS 4 TO 7/...
20.00Z AND 20.12Z MEDIUM RANGE MODELS IN REASONABLE AGREEMENT FOR
LONGWAVE RIDGING TO PERSIST ALONG THE WEST COAST AND LONGWAVE
TROUGHING TO REMAIN OVER CENTRAL/EASTERN NOAM THRU THE CHRISTMAS
HOLIDAY PERIOD. MODELS TRENDING TOWARD A ROUGH COMPROMISE OF THE
EARLIER RUNS WITH THE LONGER WAVE/MORE TRACKABLE FEATURES. THIS
LEAVES THE NORTH-CENTRAL CONUS UNDER NORTHWEST FLOW ALOFT...BUT
FOR SOME TRANSIENT SHORTWAVE RIDGING TUE...WITH PLENTY OF
INHERENTLY DIFFICULT TO TIME AND TRACK SHORTWAVES MOVING THRU THAT
FLOW LATER TUE THRU FRI. DECENT CONSISTENCY FOR THE SHORTWAVE
RIDGING TO BE MOVING ACROSS TUE...AHEAD OF A STRONGER SHORTWAVE
TROUGH TO DROP INTO/ACROSS THE NORTH-CENTRAL CONUS TUE NIGHT/WED.
RATHER DEEP/COLD MID LEVEL TROUGHING TO THEN REMAIN OVER THE UPPER
MIDWEST FOR THU/FRI. DAY 4-7 FCST CONFIDENCE IS AVERAGE THIS
CYCLE.
SHORTWAVE RIDGING ALOFT MOVES QUICKLY EAST ACROSS THE AREA TUE.
MDT/STRONG LOWER LEVEL WARM ADVECTION AND 280K-300K ISENTROPIC LIFT
SPREADS ACROSS THE AREA ON THE BACK SIDE OF THE SFC-MID LEVEL RIDGE
AXIS...ALONG WITH PW VALUES QUICKLY INCREASING TO 0.4 TO 0.5 INCH
FOR TUE AFTERNOON/EVENING AHEAD OF THE SFC-MID LEVEL TROUGH AXIS.
COLUMN LOOKS TO REMAIN COLD ENOUGH FOR ANY PRECIP TUE/TUE NIGHT AS
SNOW. IF PRESENT MODEL TRENDS CONTINUE/CONSENSUS TIGHTENS...APPEARS
SNOW CHANCES TUE AFTERNOON/EVENING WILL NEED TO BE RAISED WITH
PERHAPS 1 TO 2 INCHES OF SNOW CHRISTMAS EVE. THIS SHORTWAVE TROUGH
PASSES...BUT ANOTHER DEEP COLD CORE TROUGH SETS UP SHOP OVER THE
UPPER MIDWEST FOR WED-FRI. AGAIN PLENTY OF SHORTWAVE TIMING/STRENGTH
DETAIL DIFFERENCES FOR FEATURES TO BE ROTATING THRU THIS TROUGH IN
THE DAY 5-7 PERIOD. GIVEN THE COLD COLUMN...DEEP CYCLONIC FLOW AND
THE FCST AREA ON THE CYCLONIC SIDE OF THE 500-300MB JET...THERE IS
AN ARGUMENT FOR SMALL -SN CHANCES THRU MUCH OF THE WED-FRI PERIOD.
GIVEN THE TIMING/DETAIL DIFFERENCES... STAYED WITH THE MODEL/
ENSEMBLE CONSENSUS -SN CHANCES FOR NOW. GIVEN AVERAGE AT BEST
CONFIDENCE IN THE DETAILS...MODEL/ENSEMBLE CONSENSUS FOR TUE-FRI
HIGHS/LOWS APPEARS WELL TRENDED.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1146 AM CST FRI DEC 20 2013
THE LIGHT PRECIPITATION HAS MOVED OFF TO THE EAST OF BOTH TAF SITES.
CONDITIONS HAVE TEMPORARILY IMPROVED TO VFR BUT DO NOT EXPECT THIS
TO LAST LONG. LOTS OF MVFR WITH SOME IFR JUST OFF TO THE SOUTHWEST
AND THE CURRENT FLOW PATTERN SHOULD BRING THIS BACK OVER BOTH
AIRPORTS THIS AFTERNOON AND WILL SHOW MVFR BY THE MIDDLE OF THE
AFTERNOON. SOME POTENTIAL FOR ADDITIONAL PRECIPITATION TO DEVELOP
THIS AFTERNOON BUT IF THE 20.15Z RAP IS CORRECT...THIS SHOULD STAY
TO THE SOUTH. WITH THE BROAD SOUTHWEST FLOW...LOOKS LIKE ONCE THE
MVFR CONDITIONS MOVE BACK IN...THEY SHOULD PERSIST THROUGH THE
REMAINDER OF THE PERIOD AND COULD EVEN GO DOWN TO IFR OVERNIGHT AT
KRST.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 6 PM CST THIS EVENING FOR WIZ054-
055-061.
WINTER STORM WARNING FROM 6 PM SATURDAY TO 6 PM CST SUNDAY FOR
WIZ054-055-061.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ043-044-053.
MN...NONE.
IA...FREEZING RAIN ADVISORY UNTIL 6 PM CST THIS EVENING FOR IAZ011-
029-030.
WINTER STORM WARNING FROM 6 PM SATURDAY TO 6 PM CST SUNDAY FOR
IAZ030.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR IAZ011-029.
&&
$$
SHORT TERM...RRS
LONG TERM....RRS
AVIATION.....04
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1146 AM CST FRI DEC 20 2013
.UPDATE...
ISSUED AT 1146 AM CST FRI DEC 20 2013
THE BULK OF THE PRECIPITATION HAS SHIFTED OFF TO THE EAST OF THE
AREA BY LATE THIS MORNING. STILL SOME LIGHT SNOW OVER CENTRAL
WISCONSIN WITH SOME SLEET OR FREEZING DRIZZLE ACROSS THE SOUTH.
EXPECT THAT MOST OF THIS WILL END EARLY THIS AFTERNOON BUT COULD
SEE SOME MORE GENERATE BY MID AFTERNOON ACROSS THE SOUTH. THE RAP
SHOWS THE WEAK SHORT WAVE TROUGH COMING OUT OF EASTERN NEBRASKA TO
TRACK TOWARD THE AREA TO POSSIBLY PRODUCE THE AFTERNOON
PRECIPITATION. IF INDEED THIS DOES OCCUR...THE RAP BUFKIT
SOUNDINGS WOULD SUGGEST THERE WOULD BE LITTLE TO NO ICE IN THE
CLOUDS FOR THE POTENTIAL OF MORE FREEZING DRIZZLE. WILL LET THE
FREEZING RAIN ADVISORY ALONG INTERSTATE 90 EXPIRE AT 18Z AND
CONTINUE THROUGH THE MIDDLE OF THE AFTERNOON FARTHER SOUTH. MAY BE
NECESSARY TO EXTEND THE ADVISORY ACROSS THE SOUTH IF ADDITIONAL
FREEZING DRIZZLE DEVELOPS.
&&
.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 405 AM CST FRI DEC 20 2013
FREEZING DRIZZLE/RAIN HAVE CAUSED SOME PROBLEMS FROM SLIGHTLY
NORTH OF I-90 IN WI...WEST TO JUST OUTSIDE OF ROCHESTER DOWNTOWN
AREA...THEN SOUTH. ACCIDENTS WERE PLENTIFUL...ROAD CREWS HAVE
BEEN OUT WORKING. THE CHALLENGE NOW IS WHAT WILL TODAY LOOK LIKE
AND WHAT TO DO WITH THE IMPACT AND ADVISORY.
GOES WATER VAPOR SHOWING SHORTWAVE TROUGH ENERGY ON A NW-SE AXIS
CENTERED NEAR ABOUT TOPEKA...RIDING NORTHEAST AT THE AREA.
PRESSURES HAVE BEEN RISING OVER THE FORECAST AREA AND COLD AIR
ADVECTION IS DECREASING TEMPERATURES /ABOUT 1F PER HOUR/ DESPITE
SOME PRECIPITATION. TO THE SOUTH ALONG THE FRONTAL BOUNDARY...FROM
THE QUAD CITIES TO SOUTH OF CHICAGO...SURFACE PRESSURES HAVE BEEN
WEAKLY FALLING WITH UPPER WAVE FORCING. SURFACE LOW CENTER IS
CLOSER TO WICHITA AT 08Z. WEAK 700-600MB-CENTERED FRONTOGENETIC
FORCING IS LOCATED ACROSS THE NORTHERN FORECAST ARE YIELDING THE
LINEAR SNOW BAND. THIS HAS SEEDED THE LOW-LEVEL 3-4KFT SUPERCOOLED
LIQUID LAYER /FINALLY/ TO CHANGE THE FZDZ/FZRA TO SNOW.
THE TREND TODAY IN THE RAP FRONTOGENESIS IS TO SHIFT
EASTWARD FROM ABOUT WHERE IT IS NOW...WITHOUT MUCH MORE SOUTHWARD
PROGRESSION...EXITING BY 15Z. 20.06Z NAM HAS VERY SIMILAR
GUIDANCE...HOWEVER THE BAND WOULD SHIFT A BIT FURTHER SOUTH. SINCE
THIS IS THE SEEDER CLOUD...IT DETERMINES THE NORTHERN EXTENT OF
THE FZRA/FZDZ AREA. TO THE SOUTH...ABOUT A 2KM DEEP SUPERCOOLED
LIQUID LAYER EXISTS. RADAR HAS SHOWN SOME DECREASE IN EITHER THE
DEPTH OR LIQUID DROP SIZE OVER THE PAST HOURS IN THE DRIZZLE LAYER
WITH LESS REFLECTIVITY. THIS MAKES FOR PAUSE ON THE ADVISORY. BUT ANOTHER
AREA OF FZRA SHOWERS ARE HEADING IN FROM ERN IOWA...WITH MORE INTO
NRN MO...SO NO SHORTAGE OF INSTABILITY SHOWERS HEADING THIS WAY.
WITH UPSTREAM ENERGY AND LIFT SHIFTING INTO THE AREA...FELT THE
NEED TO EXTEND /IN TIME/ THE FREEZING RAIN ADVISORY...SOUTH OF
THE SNOW BAND...WHERE MORE ICE CAN BE EXPECTED THIS MORNING. WHILE
THE LIFT IS NOTHING LIKE LAST EVENING...THE SURFACE LOW SHIFTING
TO THE SOUTH OF THE AREA WITH DEFORMATION IN THE LOW-LEVELS OVER
NERN IA AND SRN WI MEAN FZRA/FZDZ COULD CONTINUE. MODEL GUIDANCE
ALSO SUGGESTS A WEAK INVERTED TROUGH EMANATING NW FROM THE
SURFACE LOW TO ENHANCE LOW-LEVEL VERTICAL MOTION...ENHANCING CLOUD
DROP GROWTH FOR DRIZZLE. THE LATEST HRRR RUNS HAVE THIS
SUGGESTION...ESPECIALLY LATER ACROSS THE SOUTHERN COUNTIES. THE
SNOW BAND SHOULD ONLY MOVE ABOUT ONE MORE COUNTY SOUTH BEFORE
SHIFTING EAST...AND AGAIN ALLOWING FOR AN ALL LIQUID PRECIPITATION
TYPE. HOWEVER...BEING FURTHER NORTH...THE LIFT IS SOMEWHAT MORE
LIMITED AND THE THREAT ALSO MORE LIMITED /I-90 ROUGHLY/.
THEREFORE...THINK THERE IS ADDITIONAL THREAT FOR FREEZING
PRECIPITATION...ESPECIALLY ACROSS THE SOUTH...THROUGH THE DAY.
WILL EXTENDED THE FREEZING RAIN ADVISORY IN EXTREME NERN IA AND
SWRN WI UNTIL 3PM...AND AREAS NORTH UNTIL 18Z. WILL CANCEL THE
FREEZING RAIN ADVISORY IN AREAS IT IS NOW SNOWING. CONFIDENCE IS
LOW IN THAT NORTHERN AREA...IF THERE WILL BE ENOUGH VERTICAL
MOTION TO CAUSE FZDZ TODAY...BUT IF NEEDED IT CAN BE CANCELLED
EARLY. ICING LOOKS TO BE ABOUT ANOTHER 0.05 INCHES ACROSS THE
SOUTHERN AREA...BEFORE DIMINISHING LATER.
.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 405 AM CST FRI DEC 20 2013
SATURDAY SEEMS TO BE AN IN BETWEEN DAY BEFORE THE STRONG CYCLONE
OVER THE SWRN U.S. CURRENTLY...SHIFTS TOWARD THE GREAT LAKES.
CLOUD TO GROUND LIGHTNING STRIKES WERE SEEN OVERNIGHT IN AZ WHICH
IN THE WEST...USUALLY HAPPENS ONLY WITH THE STRONGEST IMPULSES. SO
THIS IS A NICE SHORTWAVE TROUGH. THERE ARE A NUMBER OF FAVORABLE
DYNAMICS WITH THIS SYSTEM THAT SHIFT IN...INCLUDING AN INTENSE
160KT+ JET THAT DEVELOPS OVER SRN CANADA AS THE RIDGE BUILDS
DOWNSTREAM OF THE SHORTWAVE EJECTING INTO THE PLAINS. THIS IS
CLASSIC FOR MIDWESTERN HEAVY SNOWFALL CLIMATOLOGY. THIS PLACES A
VERY FAVORABLE ENTRANCE REGION OVER IL/SRN WI SAT NIGHT AND
SUNDAY. A VERY WARM AND MOIST SECTOR /SPC MDT RISK/ WILL BE RIDING
NORTH OUT OF THE GULF ON 50-60KT LOW-LEVEL WINDS AS INFLOW TO THE
FORCING...WHICH IS STRONG QVECTOR CONVERGENCE ALOFT AS
EXPECTED...TO THE SOUTHEAST. THIS STORM WILL PRODUCE HEAVY
SNOWFALL...THE QUESTION IS LOCATION.
WHILE THE WPC WINTER WEATHER DESK CONFIDENCE IS LOWER...IT SEEMS
THE MODELS ARE DRAWING IN ON A SOLUTION THAT WOULD PLACE THE HEAVY
SNOW BAND JUST INTO GRANT COUNTY. THIS WAS VERY CLOSE TO THE
ONGOING FORECAST SO REALLY ONLY MINOR CHANGES WERE MADE. THE NAM
SOLUTIONS STILL SEEM OUT TO LUNCH COMPARED TO THE OTHER
DETERMINISTIC MODELS...A DRY AND EAST OUTLIER. OVERALL...WILL
KEEP THE WATCH UNTIL CONFIDENCE GROWS ON THE LOCATION...BUT THE
REGION WILL SEE A 7-10 INCH SNOW BAND FROM THIS SYSTEM.
WILL BE MONITORING FOR POSSIBLE CHRISTMAS DAY WEATHER ON THE WARM
AIR ADVECTION SHIFTING IN...AFTER THE MONDAY AND MONDAY NIGHT
COOL DOWN POST STORM. THE 20.00Z ECMWF IS A BIT MORE AGGRESSIVE ON
HOLIDAY WEATHER...WE WILL SEE.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1146 AM CST FRI DEC 20 2013
THE LIGHT PRECIPITATION HAS MOVED OFF TO THE EAST OF BOTH TAF
SITES. CONDITIONS HAVE TEMPORARILY IMPROVED TO VFR BUT DO NOT
EXPECT THIS TO LAST LONG. LOTS OF MVFR WITH SOME IFR JUST OFF TO
THE SOUTHWEST AND THE CURRENT FLOW PATTERN SHOULD BRING THIS BACK
OVER BOTH AIRPORTS THIS AFTERNOON AND WILL SHOW MVFR BY THE MIDDLE
OF THE AFTERNOON. SOME POTENTIAL FOR ADDITIONAL PRECIPITATION TO
DEVELOP THIS AFTERNOON BUT IF THE 20.15Z RAP IS CORRECT...THIS
SHOULD STAY TO THE SOUTH. WITH THE BROAD SOUTHWEST FLOW...LOOKS
LIKE ONCE THE MVFR CONDITIONS MOVE BACK IN...THEY SHOULD PERSIST
THROUGH THE REMAINDER OF THE PERIOD AND COULD EVEN GO DOWN TO IFR
OVERNIGHT AT KRST.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR WIZ054-
055-061.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ043-044-053>055-061.
MN...NONE.
IA...FREEZING RAIN ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR IAZ011-
029-030.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR IAZ011-029-030.
&&
$$
UPDATE...04
SHORT TERM...BAUMGARDT
LONG TERM...BAUMGARDT
AVIATION...04
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
1117 AM CST FRI DEC 20 2013
.UPDATE...KEEPING FREEZING RAIN ADVISORY HEADLINES AS IS. WILL LET
NORTH EXPIRE AT NOON AS COLDER AIR MORE FIRMLY IN PLACE THERE.
STILL CONCERNED THAT MID LEVEL DRYING MAY RESULT IN SOME SPOTTY
FREEZING DRIZZLE THERE...BUT BY AND LARGE CAN RELEASE THE ADVISORY
AT THE GOING NOON END TIME. ADDITIONAL ICING EXPECTED IN THE
SOUTHERN CWA WITH NEXT SURGE RIDING NORTH FROM ILLINOIS. SOME
AREAS HAVE GONE ABOVE IN THE FAR SOUTHEAST AND CLOSE TO THE LAKE.
WINTER STORM STILL LOOKING ON TRACK FOR SATURDAY NIGHT AND SUNDAY.
THE 12Z NAM CAME IN WITH A MORE WESTWARD TRACK PLACING HEAVIER
SNOW A BIT FURTHER WEST IN THE CWA. BUT WE SAW THIS TREND WITH THE
ECMWF AND IT REVERTED BACK TO THE MORE CONSISTENT LOOK OF THE GFS.
RIGHT NOW A GFS/ECMWF TRACK IS PREFERRED. 12Z GFS HAS STAYED THE
SAME AND WILL AWAIT THE ECMWF TO RAISE CONFIDENCE FURTHER IN THIS
SCENARIO. BUT ALL IN ALL LIKE THE PLACEMENT OF THE AMOUNTS AT THIS
TIME.
PC
&&
.AVIATION/18Z TAFS/...MAIN ISSUE WILL BE AFTERNOON AND EARLY
EVENING ICING WITH NEXT SURGE OF PRECIP COMING UP FROM ILLINOIS.
WILL KEEP CIGS AT IFR LEVELS THIS FORECAST PERIOD. QUIETER
CONDITIONS TAKE HOLD LATER TONIGHT INTO SATURDAY WITH BRIEF
RIDGING. WINTER STORM STILL ON TRACK FOR SATURDAY NIGHT INTO
SUNDAY.
PC
&&
.MARINE...SUSTAINED NORTHEAST WINDS ARE AT TIMES GUSTING TO 25
KNOTS WITH SOME HIGHER WAVES OVER 4 FEET. SO WILL MAINTAIN
SMALL CRAFT ADVISORY.
PC
&&
.PREV DISCUSSION... /ISSUED 351 AM CST FRI DEC 20 2013/
TODAY AND TONIGHT...FORECAST CONFIDENCE...MEDIUM TO HIGH
SURFACE LOW PRESSURE WILL SLOWLY MOVE ACROSS CENTRAL IL AND IN
TODAY. THE 850MB BAROCLINIC ZONE WILL REMAIN STATIONARY OVER
SOUTHERN WI...WITH THE SURFACE AND 925MB FRONT OVER NORTHERN IL.
SURFACE TEMPS WILL REMAIN BELOW FREEZING TODAY EXCEPT FOR RIGHT
ALONG THE SHORELINE.
A PERSISTENT DRY LAYER FROM 10-15 KFT IS EXPECTED TO HANG IN THERE
THROUGH THE DAY...POSSIBLY MOISTENING UP LATE THIS AFTERNOON. THIS
MEANS THAT SATURATED...SUB-FREEZING CONDITIONS FROM THE GROUND UP TO
AROUND 8KFT TODAY WILL CONTINUE TO PRODUCE LIGHT FREEZING
DRIZZLE. IF THE DEEPER SATURATION CAN OCCUR TO GET SOME SNOW
PRODUCTION...THEN SNOW COULD MIX IN WITH THE FREEZING DRIZZLE/RAIN
THIS AFTERNOON.
AS FOR FORCING...THE STRONGER 850-700MB WARM AIR ADVECTION THAT
PRODUCED SHOWERY PRECIP IN THE EVENING THROUGH AROUND 2 AM IS EASING
UP THIS MORNING...BUT EXPECTED TO RAMP UP AGAIN EARLY THIS AFTERNOON
WITH A PASSING WEAK SHORTWAVE. THE NAM AND HRRR MODELS SHOW A LULL
IN PRECIP FOR ABOUT 3 HOURS MID MORNING...THEN ANOTHER ROUND OF
SHOWERY PRECIP THIS AFTERNOON.
THUS...EXTENDED THE FREEZING RAIN ADVISORY UNTIL 21Z FOR MOST OF MKX
FORECAST AREA. ONLY EXTENDED THE NORTHERN TIER OF COUNTIES UNTIL 18Z
SINCE DEEPER SATURATION SHOULD LEAD TO MORE SNOW THAN FREEZING
RAIN/DRIZZLE THERE. AGAIN...LAKESHORE AREAS WILL BE MARGINAL FOR THE
BELOW-FREEZING TEMPS TODAY TO MAINTAIN THE FREEZING RAIN
THREAT...BUT INLAND PORTIONS OF THE LAKE COUNTIES ARE EXPECTED TO
REMAIN BELOW FREEZING SO KEPT ALL COUNTIES IN THE ADVISORY.
LIGHT FREEZING DRIZZLE COULD PERSIST INTO THE EVENING...BUT DRYING
IS EXPECTED TO WORK INTO THE LOWER LEVELS AS THE SURFACE LOW SLIDES
EAST. WITH CLOUDS LINGERING OVER SOUTHERN WI...TEMPS WILL REMAIN
MODERATE...WITH LOWS DROPPING INTO THE UPPER TEENS TOWARD CENTRAL WI
AND THE UPPER 20S IN SOUTHEAST WI.
SATURDAY AND SUNDAY...FORECAST CONFIDENCE...MEDIUM TO HIGH
NOT MUCH HAS CHANGED WITH WEEKEND WINTER STORM...AS LATEST MODELS
STILL TAKE AIM AT SOUTHERN WISCONSIN. MAIN NOTICEABLE CHANGES ARE
AN OVERALL CONSENSUS INCREASE IN QPF AND VERY SLIGHT SHIFT
SOUTHWARD. THIS MINOR SHIFT RESULTED IN THE 00Z GUIDANCE
SUGGESTING SNOW FOR ALL OF THE FORECAST AREA...WITH THE MILDER AIR
ALOFT STAYING SOUTH.
OVERALL...LOOKS LIKE A PRETTY SOLID WINTER STORM IF THE CURRENT
DETAILS HOLD. CONSENSUS SFC LOW TRACK FROM WEST-CENTRAL INDIANA TO
SE MICHIGAN AND 700 MB LOW TRACK ACROSS SOUTHERN WISCONSIN ARE
USUALLY GOOD INDICATORS FOR A DECENT SNOWFALL. IN ADDITION...THOUGH
THE DENDRITE GROWTH ZONE IS NOT PARTICULARLY DEEP...FORCING WITHIN
THIS REGION REMAINS STRONG. WILL ALSO GET A BIT OF UPPER SUPPORT
AT THE ONSET OF THIS SYSTEM...AS THE FORECAST AREA WILL WITHIN THE
RIGHT ENTRANCE REGION OF A VERY STRONG UPPER JET. LATEST FORECAST
HAS THE HIGHEST AMOUNTS ACROSS THE SOUTHEAST TWO-THIRDS OF THE
FORECAST AREA...TAPERING OFF QUICKLY TOWARD THE FAR NW. THE SNOW
IS CURRENTLY EXPECTED TO MOVE IN DURING THE EVENING...WITH THE
HEAVIER SNOW ARRIVING BY MIDNIGHT AND PERSISTING INTO EARLY SUNDAY
MORNING.
WILL MAINTAIN THE WINTER STORM WATCH AS IS FOR NOW...AS THE STORM
IS A BIT TOO FAR OUT FOR A WARNING. ALSO...IT WOULD NOT TAKE MUCH
OF A SHIFT NORTH OR SOUTH IN THE STORM TRACK TO IMPACT CURRENT
EXPECTED AMOUNTS. THIS IS INCREASING CONFIDENCE WITH THIS SYSTEM
THOUGH...AS MODELS SEEM TO BE SETTLING ON A SOLUTION.
LIGHT SNOW MAY LINGER INTO SUNDAY NIGHT AS THE UPPER TROUGH
APPROACHES.
MONDAY THOUGH THURSDAY...FORECAST CONFIDENCE...LOW TO MEDIUM
LOOKS LIKE BELOW NORMAL TEMPS NEXT WEEK...WITH A CHANCE FOR LIGHT
SNOW AT TIMES AS SERIES OF SHORTWAVES PUSH THROUGH THE AREA. COULD
GET PRETTY CHILLY A COUPLE OF THE NIGHTS...WITH MODELS SUGGESTING
SUB-ZERO TEMPS. MAIN ISSUE WITH THIS PERIOD IS THAT MODELS ARE NOT
AGREEING VERY WELL ON THE TIMING OF THE WAVES AND EXTENT OF COLDER
TEMPS BEHIND THE WAVES. THUS KEPT POPS ON THE LOW END FOR NOW AND
DID NOT GO QUITE AS COLD AS SOME OF THE MODELS SUGGEST.
AVIATION/12Z TAFS/ AND MARINE...THESE SECTIONS WILL BE ADDED
SHORTLY.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR
WIZ056>060-062>072.
WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR WIZ046-047-051-052-056>060-062>072.
FREEZING RAIN ADVISORY UNTIL NOON CST TODAY FOR WIZ046-047-051-
052.
LM...WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY
AFTERNOON FOR LMZ643.
SMALL CRAFT ADVISORY UNTIL 6 PM CST THIS EVENING FOR LMZ643>646.
&&
$$
TODAY/TONIGHT AND AVIATION/MARINE...MRC
SATURDAY THROUGH THURSDAY...DDV