Forecast Discussions mentioning any of
"HRRR" "RAP" "RR" "RUC13" "RUC" received at GSD on 12/29/12
AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
341 PM MST THU DEC 27 2012
.SHORT TERM...MOUNTAIN WEB CAMS SHOWING ONGOING SNOWFALL...THOUGH
BEGINNING TO SHOW SOME SIGNS OF DECREASING. LATEST RUC KEEPS
AIRMASS FAIRLY MOIST THROUGH THE EVENING WITH FLOW BECOME MORE
NORTHWEST. HOWEVER...LAPSE RATES BEGIN DECREASING ALONG WITH
INCREASING SUBSIDENCE. THUS SHOULD SEE A GRADUAL DECREASE IN
SNOWFALL THROUGH THE EVENING WITH PERHAPS ANOTHER 2 TO 4 INCHES
DUE TO THE OROGRAPHICS. WILL KEEP THE ADVISORIES GOING THROUGH
06Z. ACROSS PLAINS...RADAR SHOWING LIGHT SNOW DEVELOPING ACROSS
PALMER DIVIDE AS WELL AS ACROSS PORTIONS OF EASTERN LARIMER AND
WESTERN WELD COUNTIES. LATEST MODELS SHOW THE SNOW PERSISTING
ACROSS THE PALMER DIVIDE AND SOUTHERN FOOTHILLS THROUGH THE
EVENING...SPREADING NORTH ALONG THE FOOTHILLS AND WESTERN SECTIONS
OF THE URBAN CORRIDOR AND EAST INTO LINCOLN COUNTY BY 05Z. WILL
CONTINUE THIS TREND FOR THE EVENING WITH THE HIGHER POPS IN THIS
AREA AS WELL AS IN EASTERN LARIMER COUNTY. ELSEWHERE ALONG THE
URBAN CORRIDOR...WILL CONTINUE WITH CHANCE POPS AS IT STILL
APPEARS MOST OF SNOW SHOULD OCCUR CLOSER TO THE FOOTHILLS. LOWER
POPS EASTWARD AWAY FROM THE FRONT RANGE. THE EASTERLY UPSLOPE
STILL LOOKING FAIRLY WEAK...STILL THINKING ACCUMULATIONS WILL BE
BELOW AN INCH THOUGH A FEW AREAS ALONG THE PALMER DIVIDE AND NEAR
THE FOOTHILLS COUND SEE A BIT MORE. AS LAPSE RATES DECREASE AFTER
06Z...SHOULD SEE SNOW CHANCES DECREASE AS WELL. WILL KEEP A
SLIGHT CHANCE OF LIGHT SNOW IN AND NEAR THE FOOTHILLS AS WELL AS
ALONG THE PALMER DIVIDE INTO LINCOLN COUNTY. ON FRIDAY...NORTHWEST
FLOW ALOFT TO CONTINUE WITH UPPER TROUGH OVER NORTHERN PLAINS.
MODEL CROSS SECTIONS SHOW FAIRLY DECENT MOISTURE ACROSS THE
MOUNTAINS...GRADUALLY DECREASING DURING THE AFTERNOON. THUS THERE
SHOULD BE AT LEAST A CHANCE OF SNOW DUE TO THE FAVORED
OROGRAPHICS. HOWEVER...QG VERTICAL VELOCITIES SHOW DOWNWARD
MOTION...WHICH WILL LIMIT THE SNOW CHANCES AS WELL AS
ACCUMULATIONS. ACROSS PLAINS...DRY CONDITIONS TO PREVAIL WITH A
DECREASE IN CLOUD COVER BY THE AFTERNOON. TEMPERATURES ONLY
EXPECTED TO WARM A FEW DEGREES FROM TODAY`S READINGS DUE TO SNOW
COVER AND INVERSIONS.
.LONG TERM...DRIER AIR WILL BE MOVING OVER COLORADO FRIDAY NIGHT. IF
ANY SNOW SHOWERS LINGER INTO THE EVENING HOURS...THEY WILL BE LIGHT
AND SHORT LIVED. SKIES WILL CLEAR BY MIDNIGHT...IF NOT EARLIER. THE
CLEAR SKIES WILL ALLOW TEMPERATURES IN LOW LYING AREAS TO PLUMMET.
EXPECT THE MOUNTAIN VALLEYS TO DROP BELOW ZERO. COLD LOCATIONS LIKE
KREMMLING WILL DROP TO AROUND -20 BY SATURDAY MORNING. WEAK
DOWNSLOPE WINDS WILL DEVELOP ALONG THE FRONT RANGE. THIS WILL KEEP
THE FOOTHILLS AND AREAS CLOSE TO FOOTHILLS WARMER WITH LOWS IN THE
SINGLE DIGITS TO TEENS.
UPPER LEVEL RIDGE WILL MOVE ACROSS COLORADO SATURDAY. AIRMASS UNDER
IT WILL BE DRY RESULTING IN MOSTLY CLEAR SKIES. HIGHS WILL CLIMB
INTO THE 30S FOR MOST OF NORTHEAST COLORADO. LOW LYING AREAS MAY BE
STUCK UNDER AN INVERSION AND WILL STRUGGLE TO REACH THE 30S.
CLOUDS WILL INCREASE SUNDAY AS AN UPPER LEVEL TROUGH MOVES OVER THE
GREAT BASIN. THE MOISTURE WILL BE AT THE MID AND UPPER LEVELS OF THE
ATMOSPHERE...SO NOT EXPECTING ANY SNOW UNTIL THE TROUGH NEARS WHICH
WILL BE LATE SUNDAY NIGHT. THE UPPER LEVEL TROUGH WILL DIG SOUTHEAST
AND MOVE ACROSS THE SOUTHERN ROCKIES MONDAY. A COLD FRONT ASSOCIATED
WITH THE TROUGH WILL PUSH THROUGH THE AREA MONDAY. APPEARS THE
TROUGH WILL BE TOO FAR SOUTH TO BRING THE AREA MUCH PRECIPITATION.
WILL KEEP LOW POPS...10 TO 30 PERCENT...IN THE FORECAST FOR MONDAY
AND TUESDAY. HIGHEST POPS BEING IN THE MOUNTAINS. COOL AIR WILL MOVE
BACK INTO THE AREA FOR MONDAY AND TUESDAY.
FOR WEDNESDAY AND THURSDAY...APPEARS THERE WILL BE SOME SORT OF
RIDGE OVER THE WESTERN STATES. THIS WILL PRODUCE A DRY BUT COOL
NORTHWEST FLOW ALOFT OVER COLORADO. WILL KEEP THE FORECAST DRY WITH
TEMPERATURES AT OR SLIGHTLY BELOW NORMAL.
&&
.AVIATION...LIGHT SNOW DEVELOPING ALONG PALMER DIVIDE AS WELL AS
WESTERN AND SOUTHERN SECTIONS OF THE DENVER AREA. LATEST RUC AND
HRRR KEEPS THE BEST CHANCE FOR SNOW AT APA AND BJC THROUGH 06Z...
WILL CONTINUE THE TEMPO FOR MVFR/IFR CONDITIONS. STILL SOME CHANCE
THAT SNOW COULD SPREAD INTO DIA WITH POSSIBLE MVFR/IFR CONDITIONS.
FOR NOW WILL CONTINUE VCSH AND SEE HOW THINGS DEVELOP. SNOW
CHANCES TO DECREASE AFTER 06Z WITH VFR CONDITIONS AND IMPROVING
CEILINGS. EASTERLY WINDS TO DECREASE AFTER MIDNIGHT AND BECOME
SOUTHERLY AS DRAINAGE PATTERN DEVELOPS. WINDS TO REMAIN LIGHT
SOUTHERLY THROUGH FRIDAY AS DRY CONDITIONS PREVAIL.
&&
.PREV DISCUSSION... /ISSUED 1007 AM MST THU DEC 27 2012/
UPDATE...
SHORT TERM...MOUNTAIN WEB CAMS SHOWING SNOW ACROSS MUCH OF THE
REGION. WITH MOIST WEST NORTHWEST FLOW ALONG TO PERSIST THROUGH
MUCH OF THE DAY ALONG WITH LAPSE RATES AROUND 6 C/KM WEAK MID
LEVEL QG ASCENT...SNOW SHOULD CONTINUE INTO THE EVENING WITH
ANOTHER 3-6 INCHES. CURRENT ADVISORIES TO CONTINUE. SOME DECREASE
IN THE SNOW STILL EXPECTED OVERNIGHT AS ASCENT WEAKENS AND
SUBSIDENCE PREVAILS. ACROSS PLAINS...THE LIGHT SNOW OVER THE
NORTHEAST CORNER HAS ENDED WITH MOSTLY CLOUDY CONDITIONS
PREVAILING. LATEST MODELS CONTINUE TO SHOW WEAK DISTURBANCE MOVING
ACROSS THE CENTRAL PLAINS WITH WEAK UPSLOPE LOW DEVELOPING ALONG
THE FRONT RANGE. RAP/RUC SHOW SOME LIGHT PRECIP/QPF DEVELOPING
ACROSS THE NORTHERN FRONT RANGE AND PALMER DIVIDE AREA DURING THE
AFTERNOON WITH THE NORTHERN BATCH GRADUALLY SPREADING SOUTHWARD
BY EVENING. THERE STILL IS THE POTENTIAL FOR SOME LIGHT SNOW IN
AND NEAR THE FRONT RANGE. LATEST MODELS SEEM TO FAVOR THE NORTHERN
PORTIONS OF THE FRONT RANGE AS WELL AS NEAR THE FOOTHILLS AND
PALMER DIVIDE FOR THE MAIN AREA OF PRECIP. CONFIDENCE HAS IMPROVED
ENOUGH TO GO WITH LIKELY POPS ACROSS PORTIONS OF ZONE 38 AND
41...INCLUDING FOOTHILL LOCATIONS BETWEEN 21Z AND 03Z.
ACCUMULATIONS STILL LOOK TO BE LESS THAN AN INCH. REST OF
FORECASTS SEEM ON TRACK FOR NOW.
AVIATION...STILL SOME STRATUS ALONG LOW LYING AREAS OF SOUTHERN
WELD COUNTY...SHOULD REMAIN IN THAT AREA AND NOT AFFECT THE
AIRPORTS. WINDS SHOWING MORE OF A SOUTHEAST COMPONENT. STILL SOME
CHANCE OF LIGHT SNOW BETWEEN 23Z AND 06Z. HOWEVER HAVE A LOW
CONFIDENCE IN A TEMPO GROUP AT THIS TIME AND WILL KEEP THE VCSH
WITH PERHAPS A PROB030 AFTER 03Z. WILL CONTINUE THE TREND OF THE
CURRENT TAFS AT THIS POINT. IF SNOW DOES AFFECT THE AREA
AIRPORTS...ACCUMULATIONS SHOULD BE LESS THAN AN INCH.
PREV DISCUSSION... /ISSUED 259 AM MST THU DEC 27 2012/
SHORT TERM...A BROAD CIRCULATION CENTER WAS LOCATED FM ERN WY
INTO WRN NE EARLY THIS MORNING AND WILL MOVE SLOWLY EASTWARD THRU
TONIGHT. OVERALL THE FLOW ALOFT IN THE MTNS WILL BE WNW WITH
FAVORABLE OROGRAPHICS THRU TONIGHT. LAPSE RATES WILL AVERAGE
AROUND 7 C/KM WITH MOISTURE DEPTH AROUND 300 MB SO SHOULD SEE
PERIODS OF SNOW WITH ACCUMULATIONS MEETING ADVISORY CRITERIA. OVER
NERN CO IT APPEARS ANY PCPN THRU LATE AFTN WILL BE CONFINED TO
THE FAR NERN CORNER MAINLY THIS MORNING. HOWEVER BY THIS EVENING A
DISTURBANCE WILL MOVE SSE ACROSS THE AREA WITH WEAK UPSLOPE FLOW
DEVELOPING ALONG THE FRONT RANGE. THUS COULD SEE A BREIF PERIOD OF
LIGHT SNOW IN AND NR THE FOOTHILLS AND OVER THE PALMER DIVIDE IN
THE 00Z-06Z TIMEFRAME. HAVE INCREASED POPS TO CHC CATEGORY HOWEVER
CONFIDENCE IS NOT HIGH ENOUGH AT THIS POINT TO GO LIKELY. AS FAR
AS HIGHS THIS AFTN READINGS ACROSS NERN CO WILL BE MAINLY IN THE
20S. AROUND DENVER COULD SEE A 10 DEGREE SPREAD IN HIGHS AS
INVERSION MAY BREAK OVER THE SRN SUBURBS ALLOWING FOR HIGHS IN
THE LOWER TO MID 30S WHILE OTHER AREAS AROUND DENVER STAY IN THE
MID TO UPPER 20S.
LONG TERM...ZONAL FLOW IS PROGGED OVER THE CWA FRIDAY...THEN
NORTHWESTERLY FLOW ALOFT IS PROGGED FOR FRIDAY NIGHT. AN UPPER
RIDGE IS PROGGED TO MOVE ACROSS COLORADO SATURDAY. THE FLOW ALOFT
IS ZONAL ON SATURDAY...THEN SOUTHWESTERLY SATURDAY NIGHT. THE QG
VERTICAL VELOCITY FIELDS HAVE DOWNWARD SYNOPTIC SCALE ENERGY OVER
THE CWA FRIDAY INTO SATURDAY MORNING. THE REST OF SATURDAY AND
SATURDAY NIGHT HAS WEAK UPWARD MOTION PROGGED. THE BOUNDARY LAYER
FLOW LOOKS TO BE DOMINATED BY DOWNSLOPING FRIDAY INTO SATURDAY
MORNING...THEN MORE NORMAL DUIRNAL PATTERNS ARE PROGGED FOR THE
REST OF SATURDAY AND SATURDAY NIGHT. FOR MOISTURE...THERE IS SOME
AROUND ON FRIDAY...ACTUALLY PRETTY DEEP OVER THE MOUNTAINS IN THE
MORNING. DRYING KICKS IN BY AFTERNOON...CONTINUING FRIDAY
EVENING. THE REST OF FRIDAY NIGHT AND SATURDAY LOOK PRETTY DRY FOR
ALL AREAS...MAYBE SOME HIGH CLOUDS. MOISTURE INCREASES SATURDAY
NIGHT...MOSTLY THE UPPER LEVEL TYPE. THE QPF FIELDS SHOW SMALL
AMOUNTS OF MEASURABLE PRECIPITATION ON FRIDAY IN THE MOUNTAINS
ONLY. FRIDAY NIGHT THROUGH SATURDAY NIGHT ARE DRY. SO FOR POPS
.WILL GO WITH 30-60%S IN THE MOUNTAINS ON FRIDAY. THERE IS
FAIRLY DECENT MOISTURE AND SOME HELP FROM OROGRAPHICS. JUST MINOR
POPS IN THE MOUNTAINS FRIDAY EVENING. NO POPS ELSEWHERE THROUGH
THE PERIODS. FOR TEMPERATURES...FRIDAY`S HIGHS ARE A TAD WARMER
THAN TODAY`S. SATURDAY`S WARM UP 2-4 C FROM FIRDAY`S HIGHS. FOR
THE LATER DAYS...SUNDAY THROUGH WEDNESDAY...SOUTHWESTERLY FLOW
ALOFT IS PROGGED SUNDAY INTO MONDAY. MODELS SHOW AN UPPER TROUGH
TO MOVE ACROSS THE FORECAST AREA LATE MONDAY INTO TUESDAY MORNING.
THE ECMWF AND GFS SHOW THE TROUGH IN PRETTY FAIR AGREEMENT.
HOWEVER...THE ECMWF HAS A CLOSED CIRCULATION AT IT`S BASE...THE
GFS DOES NOT HAVE THIS. SO BY TUESDAY...THE GFS HAS THE TROUGH
THROUGH THE CWA...WHILE THE ECMWF HAS A CLOSED CIRCULATION SOUTH
OF COLORADO. THIS UPPER LOW IS CENTERED NEAR EL PASO TEXAS LATE
WEDNESDAY. MOISTURE IS WAY DIFFERENT ON THE TWO MODELS....THE GFS
SHOWS QUITE A BIT OF MOISTURE FOR SUNDAY NIGHT AND MONDAY. THE
ECMWF DOWSN`T GET MOISTURE INTO THE CWA UNTIL MONDAY NIGHT AND
TUESDAY. POOR AGREEMENT HERE. LATER TUESDAY THROUGH WEDNESDAY LOOK
DRY ON BOTH MODELS. WILL KEEP POPS SOMEWHAT AT BAY DUE TO THE
UNCERTAINTIES.
AVIATION...STRATUS HAS REMAINED JUST TO THE NORTH OF THE AIRPORT OVER
SRN WELD COUNTY THE ENTIRE NIGHT AND SO FAR HAS SHOWN NO SIGNS OF
SPREADING SOUTH AT THIS POINT. BOTH THE RAP AND THE HRRR KEEP SHOW
SFC WINDS BECOMING MORE SLY BY SUNRISE SO IF THAT OCCURS THEN
STRATUS MAY NOT AFFECT THE AIRPORT. COULD SEE SOME PATCHY FOG
HOWEVER VISBILITIES LOOK TO BE AOA 5 MILES AT THIS POINT. BY
MIDDAY SFC WINDS WILL BECOME MORE ELY AND STAY THAT WAY THRU EARLY
EVENING. AS TALKED ABOUT ABV THERE COULD BE SOME LIGHT SNOW FOR A
FEW HOURS BETWEEN 00Z AND 06Z AS DISTURBANCE MOVES SSE ACROSS THE
AREA. AT THIS POINT ANY ACCUMULATION SHOULD BE LESS THAN AN INCH
IF SNOW DEVELOPS.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR COZ031-
033-034.
&&
$$
SHORT TERM...D-L
LONG TERM....MEIER
AVIATION...D-L
AREA FORECAST DISCUSSION
NWS PUEBLO CO
303 PM MST THU DEC 27 2012
.SHORT TERM...
(TONIGHT AND FRIDAY)
TRAILING TROF ACROSS THE GREAT BASIN/NRN U.S. ROCKIES WILL SHIFT
SOUTHEASTWARD ACROSS CO TONIGHT WITH ANOTHER LOBE OF ENERGY WITHIN THE
TRAILING TROF MOVING ACROSS THE REGION DURING THE EVENING HOURS.
SFC HIGH WILL CONTINUE TO SINK SOUTHWARD ACROSS THE PLAINS WITH
SHALLOW EASTERLY UPSLOPE FLOW DEVELOPING ACROSS EL PASO COUNTY.
ALTHOUGH FORCING ALOFT IS NOT TERRIBLY STRONG...12Z MODEL RUNS
DEEPLY SATURATE THE ATMOS FAIRLY QUICKLY THIS AFTERNOON AS MOISTURE
MOVES IN FROM THE NW AND UPSLOPE HELPS SATURATE THE LOW LEVELS.
GFS...NAM12...RAP13...AND SREF ALL SPREAD LIGHT SNOW EASTWARD ACROSS
NRN SECTIONS OF THE SE MTNS/PLAINS THIS EVENING...NAMELY THE PIKES
PEAK REGION. THERE IS SOME INSTABILITY TO WORK WITH AS WELL
ESPECIALLY THIS AFTERNOON/EARLY EVENING. SO AS WEAK FORCING MOVES IN
AND SHALLOW UPSLOPE DEVELOPS...EXPECT -SHSN BANDS TO BREAK OUT
ACROSS PIKES PEAK AND EL PASO COUNTY DURING THE LATE AFTN/EARLY
EVENING AND STREAK OFF TO THE SOUTHEAST. COULD SEE LOCAL SNOW
ACCUMS OF AN INCH OR TWO FROM SOME OF THESE BANDS...AND RECENT
RUNS OF THE HRRR AND LOCAL 4 KM WRF HAVE STARTED TO TREND TOWARDS
THE OTHER MODELS IN DEPICTING THIS. THUS HAVE INCREASED POPS INTO
THE SCATTERED AND EVEN LOW LIKELY CATEGORY FOR TELLER/NRN EL PASO
COUNTIES THIS EVENING. RUC13 AND LOCAL 4 KM WRF SPREAD PCPN EASTWARD
ACROSS NRN PORTIONS OF THE SE PLAINS OUT TOWARDS KIOWA COUNTY DURING
THE OVERNIGHT HOURS. THUS WILL SPREAD AT LEAST SOME ISOLATED POPS
TO THE SOUTH AND EAST WITH TIME. NOT MUCH ACCUMULATION IS EXPECTED
FARTHER TO THE SOUTH AND EAST.
SYSTEM CLEARS THE AREA BY FRIDAY MORNING WITH DRIER AIR MOVING
IN...THOUGH THERE IS STILL ENOUGH MOISTURE IN NW FLOW TO KEEP SOME
OROGRAPHIC SNOW SHOWERS CONTINUING ALONG THE WESTERN SLOPES OF THE
MOSQUITO AND SAWATCH RANGES THROUGH THE DAY. OTHERWISE...COLD NW
FLOW REMAINS ACROSS THE AREA FOR FRIDAY...TEMPS WILL PROBABLY ONLY
WARM INTO THE 20S ACROSS THE PLAINS...WITH SFC INVERSIONS HOLDING
STRONG IN THE SAN LUIS VALLEY WHERE HIGHS WILL ONLY CLIMB INTO THE
TEENS. -KT
.LONG TERM...
(SATURDAY - THURSDAY)
...ANOTHER SYSTEM FOR MONDAY...
SATURDAY INTO SUNDAY...
A SHARP SHORT WAVE RIDGE WILL MOVE ACROSS THE REGION DURING THE
WEEKEND. ANY SNOW SHOWERS OVER THE C MTNS FRIDAY EVENING WILL
QUICKLY END...AND DRY WEATHER WILL BE OVER THE REGION LATER FRIDAY
NIGHT THROUGH SUNDAY DAY. MAX TEMPERATURES SAT AND SUN WILL BE
SEASONABLE WITH TEMPS AROUND 40F PLAINS AND 20S AND 30S MTNS/VALLEYS.
LATE SUNDAY INTO TUESDAY...
ANOTHER PACIFIC NW WX SYSTEM WILL MOVE ACROSS THE REGION THROUGH
THIS PERIOD. THERE IS DISAGREEMENT AMONGST THE LONGER RANGE
GUIDANCE...BUT IT IS LIKELY THAT ANOTHER TROUGH WILL MOVE ACROSS THE
REGION DURING THIS PERIOD. THE EC IS MOST PROMISING FOR OVERALL
PRECIP ACROSS THE AREA...WITH THE GFS SHOWING MOST OF THE PRECIP
MAINLY OVER THE MTNS. COOLER WEATHER WILL ONCE AGAIN MOVE INTO THE
REGION WITH HIGHS LIKELY NOT GETTING ABOVE FREEZING MONDAY AND
TUESDAY. FOR NOW...PAINTED HIGH END SCATTERED AMOUNTS ACROSS THE
CONTDVD...SCATTERED POPS ACROSS THE REST OF THE MTNS AND ISOLD POPS
IN THE VALLEYS. ACROSS THE PLAINS...PAINTED ISOLD POPS MAINLY ACROSS
THE FAR E PLAINS AND THE RATON MESA.
AT THIS TIME...SNOWFALL AMOUNTS SHOULD BE ON THE LIGHTER SIDE...WITH
LOW END ADVISORY AMOUNTS POSSIBLE ALONG THE CONTDVD.
WED AND THU...
IT SHOULD BE DRY ACROSS THE REGION WITH TEMPS RISING INTO THE L40S
ONCE AGAIN ACROSS THE PLAINS AND 20S MTNS/VALLEYS.
&&
.AVIATION...
LOWERING CLOUD LAYER WILL AFFECT THE TAF SITES WITH MVFR CIGS
DEVELOPING IN KCOS BY 23Z. CIGS COULD EVEN FALL INTO THE IFR
CATEGORY AFTER 00Z IF -SHSN MOVES ACROSS THE TERMINAL. SNOWFALL
ACCUMULATIONS OF UP TO 1 INCH WILL BE POSSIBLE AT KCOS. KPUB WILL ALSO
SEE LOWERING CIGS IN THE EVENING...WITH MVFR TO POSSIBLY IFR CIGS
DEVELOPING AFTER 06Z WITH SOME PATCHY FOG. MAIN THREAT FOR -SHSN
LOOKS TO STAY TO THE NORTH OF THE TERMINAL...SO WILL NOT INCLUDE IT
INTO THE KPUB TAF JUST YET. ONCE SYSTEM PASSES OFF TO THE
EAST...WINDS WILL SHIFT OUT OF THE NW TO N WITH CIGS/VIS RISING INTO
THE VFR CATEGORY FOR KCOS AND KPUB AROUND/AFTER 09Z.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR COZ058-
060-066-068.
&&
$$
31/34
AREA FORECAST DISCUSSION
NWS GRAND JUNCTION CO
1208 PM MST THU DEC 27 2012
.UPDATE...
ISSUED AT 1208 PM MST THU DEC 27 2012
DEFORMATION AXIS ALONG THE SRN WY BORDER WAS EVIDIENT ON INFRARED
SATELLITE THIS MORNING...BUT WARMING CLOUD TOPS INDICATIVE OF THIS
FEATURE BEGINNING TO WEAKEN. RAP40 MODEL SHOWS THIS WEAKENING
TREND FOR THE AFTERNOON AS THE AXIS DRIFTS SLOWLY SOUTH. STILL EXPECT
IT PLUS WEAK OROGRAPHIC FORCING AS FLOW BECOMES MORE NORTHWEST TO
KEEP OCCASIONAL SNOW ACROSS NW CO THROUGH THIS EVENING.
MID-MORNING SPOTTER AND SNOTEL REPORTS INDICATED ROUGHLY 4-8 INCHES
OF NEW SNOW ACROSS THE ELKHEAD/PARK/GORE RANGES AND FLATTOPS.
LOCATIONS SUCH AS TOWER SNOTEL AND STEAMBOAT SKI REPORTED 15-17
INCHES...BUT THESE APPEAR TO BE THE EXCEPTIONS RATHER THAN THE NORM.
THUS...WILL NOT UPGRADE THE CURRENT ADVISORIES FOR THE NRN CO MTNS
BUT WILL INCREASE TOTAL ACCUMS TO 7-14 INCHES WITH LOCALLY HIGHER
AMOUNTS IN A MIDDAY UPDATE TO THE ADVISORY STATEMENT.
MID-MORNING SPOTTER REPORTS INDICATED ROUGHLY 2-4 INCHES ACROSS THE
NW CO PLATEAU WITH LOCALLY HIGHER AMOUNTS AROUND 6 INCHES IN THE
MEEKER AND RANGELY AREAS. ABOUT 8 INCHES REPORTED FOR STEAMBOAT
TOWN. WILL CONTINUE WITH THE CURRENT ADVISORIES FOR THESE AREAS.
SNOW AND CLOUDS ARE EXPECTED TO SPREAD BACK ACROSS THE CENTRALA ND
SOUTHWESTERN CO MTNS THIS AFTERNOON AS THE COLD AND MOIST AIRMASS
SLOWLY ROTATES THROUGH THE TROUGH AND AROUND AN UPPER LOW OVER
NE/SD. SOME MORNING SUNSHINE LIKLEY ADDED SOME LOW LEVEL INSTABILITY.
UPDATE ISSUED AT 904 AM MST THU DEC 27 2012
ALLOWED THE WINTER WEATHER ADVISORIES FOR THE ERN UINTA BASIN AS
WELL AS THE CENTRAL AND SOUTHERN VALLEYS TO EXPIRE NORMALLY AT 9
AM THIS MORNING. COLD AND MOIST AIRMASS REMAINING OVER THE AREA
UNDER A BROAD TROUGH OVERHEAD AND WILL STILL KEEP SOME LIGHT SNOW
OR SNOW SHOWERS IN THE VALLEYS...BUT DO NOT EXPECT MUCH MORE
ACCUMULATION...ALTHOUGH MAY STILL SEE SOME LOCALIZED ACCUMS IN THE
ERN UINTA BASIN WHICH APPEARS TO BE UNDER A WEAK DEFORMATION AXIS
THAT EXTENDS ACROSS NW CO TO AN UPPER LOW OVER WRN NEBRASKA.
OCCASIONAL SNOW WILL CONTINUE OVER THE MOUNTAINS AND THE NW CO
PLATEAU AS FLOW SHIFTS FROM WEST THIS MORNING TO NORTHWEST THIS
AFTERNOON...AND WILL KEEP THOSE ADVISORIES IN FORCE. WEBCAMS
SHOWED BREAKS IN THE CLOUDS ACROSS THE SAN JUANS AND THE SOUTH
THIS MORNING...BUT HI-RESOLUTION HRRR MODEL INDICATES THIS TO FILL
BACK IN THIS AFTERNOON AS THE NEXT DISTURBANCE ROTATES THROUGH.
HAVE UPDATED THE WORDED AND FORECAST GRIDS TO REFLECT THIS
THINKING.
&&
.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 346 AM MST THU DEC 27 2012
A MESSY DISORGANIZED COLD WINTER STORM CONTINUES TO PRODUCE
WIDESPREAD BUT LIGHT SNOWFALL ACROSS THE FORECAST AREA. KEY TO THE
SNOW PRODUCTION IS A MOIST DENDRITIC GROWTH LAYER AT 700 TO 600MB
OR THE MTN TOP LAYER. DEVELOPING MID LEVEL CYCLONIC FLOW AND A
SHOT OF COLD ADVECTION TODAY WILL ALSO KEEP SNOW PRODUCTION
WIDESPREAD.
THE MAIN SYNOPTIC FEATURE IS THE CLOSED LOW OVER EASTERN WYOMING
THAT IS ROTATING SPOKES OF ENERGY MAINLY ACROSS THE NORTHERN
ZONES. THIS LOW WILL SHIFT EAST THIS MORNING WITH THE LAST
TRAILING DISTURBANCE AND SHOT OF COLD AIR ROTATING OVER THE
NORTHERN COLORADO MTNS. IN ADDITION THE 500-300MB SHEAR AXIS
REMAINS OVER THE SW SAN JUAN REGION THROUGH THE MORNING HOURS.
SANDWICHED BETWEEN THESE TWO LARGER SCALE FEATURES...THE CENTRAL
ZONES ARE ACCUMULATING THE LEAST SNOW AMOUNTS. IT WILL BE
DIFFICULT FOR GRAND JUNCTION AND MONTROSE TO ACCUMULATE 3 INCHES
OF SNOW...BUT WITH SNOWFALL CONTINUING WILL KEEP THE ADVISORIES
ACTIVE. OTHERWISE THE VEERING WINDS ALOFT FROM WEST TO NORTH WILL
PRODUCE SNOWFALL MAINLY ON NORTH FACING SLOPES WHERE SKI SLOPES
ARE LOCATED. THE CENTRAL VALLEYS COULD ALSO SEE A QUICK FEW INCHES
OF SNOWFALL IN THE LATE AFTERNOON INTO THE EARLY EVENING.
TONIGHT...NORTH FLOW CONTINUES WITH WEAK TRANSIENT RIDGING
BUILDING AFTER MIDNIGHT. IN SPITE OF THIS...LIGHT OROGRAPHIC
SNOWFALL IS EXPECTED FAVORING THE NORTHERN MTNS. FRIDAY...A DRIER
AIR MASS WORKS IN FROM WEST TO EAST WITH LIGHT SNOWFALL CONTINUING
ONLY IN THE EASTERN MTNS. WARM ADVECTION ALOFT BEGINS IN THE
AFTERNOON STRONGLY CAPPING THE COLD AIR IN THE VALLEYS.
.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 346 AM MST THU DEC 27 2012
SNOW COMES TO AN END OVER THE ENTIRE FORECAST AREA FRIDAY NIGHT AS
SHRTWV RIDGE WORKS EAST. THIS WILL BRING DRY CONDITIONS THROUGH
EARLY SUNDAY...BEFORE NEXT LONG WAVE TROUGH WORKS INTO THE WESTERN
U.S. MEDIUM RANGE MODELS STILL ON DIFFERENT PATHS IN REGARDS TO
THIS SPLITTING SYSTEM WITH THE ECMWF CONTINUING TO DRIVE THE
SOUTHERN EXTENT OF THE TROUGH SOUTH INTO THE BAJA REGION BY
SUNDAY...WITH SPLITTING NORTHERN ENERGY SLOWLY DROPPING SOUTHWEST
ACROSS THE WESTERN GREAT BASIN AND EVENTUALLY PHASING WITH THE
SOUTHERN STREAM...THEN EJECTING OUT BY MIDWEEK. THIS KEEPS PRECIP
OUT OF OUR REGION UNTIL LATER MONDAY WITH MAIN IMPACT ACROSS THE
SOUTHERN ZONES.
THE GFS ON THE OTHER HAND SPLITS THE TROUGH AS WELL...BUT FOCUS IS
ON THE NORTHERN STREAM WHICH DRIVES THROUGH THE FORECAST AREA AS A
POSITIVELY TILTED TROUGH SUNDAY NIGHT AND MONDAY...WHICH WOULD
BRING A GOOD CHANCE OF SNOW TO MUCH OF THE FORECAST AREA.
WITH THESE TWO OUT OF PHASE...DECIDED TO TAKE A CLOSER LOOK AT THE
CANADIAN AND OTHER ENSEMBLES AVAILABLE WHICH OFFERING MORE OF A
COMPROMISE BETWEEN THE TWO. SO WILL KEEP LOW POPS IN THE FORECAST
BEGINNING AS EARLY AS SUNDAY AFTERNOON AND PEAKING ON MONDAY. THE
GFS HAS MAINTAINED SOME CONSISTENCY OVER THE PAST FEW RUNS...SO
SOME INCREASE IN CONFIDENCE TOWARD THAT SOLUTION...BUT NOT ENOUGH
TO DRIVE POPS INTO THE LIKELY THRESHOLD.
BEYOND THIS EVENT...THE FORECAST REMAINS RATHER UNSETTLED WITH
ANOTHER FAST MOVING SYSTEM RUNNING THROUGH TUESDAY
AFTERNOON...FOLLOWED BY TRANSITORY RIDGING AT MIDWEEK WITH YET
ANOTHER SYSTEM POSSIBLE BY THE END OF THE WEEK.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 955 AM MST THU DEC 27 2012
SNOWFALL WILL RESULT IN MOUNTAIN OBSCURATIONS...AND MVFR CIGS AND
VSBY FOR THE NORTHERN AIRPORTS. IFR VSBY WILL BE POSSIBLE AT TIMES
IN HEAVIER SNOW. ALONG AND SOUTH OF I-70 SNOWFALL WILL GENERALLY
BE LIGHTER AND MORE SPORADIC. EXPECT PERIODS OF MVFR/ISOLD IFR
CONDITIONS THROUGH TODAY. WHILE CLOUD DECKS AT KEGE AND KRIL HAVE
OPENED UP THIS MORNING...CLOUDS WILL AGAIN INCREASE AND THICKEN
THIS AFTERNOON WITH SNOW SHOWERS DEVELOPING. THE FLOW TURNS TO
COLD NW THIS AFTERNOON AND EVENING WITH WIDESPREAD SNOWFALL ALONG
NORTH AND NORTHWEST FACING SLOPES THROUGH TONIGHT. OTHERWISE
IMPROVING CONDITIONS ARE EXPECTED. THESE OROGRAPHIC SNOW SHOWERS
WILL DIMINISH EARLY FRIDAY. AREAS OF FOG MAY RESULT IN MVFR OR IFR
CONDITIONS AT AREA AIRPORTS LATE TONIGHT AND FRIDAY MORNING.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR COZ001-
002-005.
WINTER WEATHER ADVISORY UNTIL 6 AM MST FRIDAY FOR COZ003-004-009-
010-012-013-017>019.
UT...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR UTZ023-
025-028.
&&
$$
UPDATE...JAD
SHORT TERM...JOE
LONG TERM...JDC
AVIATION...EH
AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
1007 AM MST THU DEC 27 2012
.UPDATE...
&&
.SHORT TERM...MOUNTAIN WEB CAMS SHOWING SNOW ACROSS MUCH OF THE
REGION. WITH MOIST WEST NORTHWEST FLOW ALONG TO PERSIST THROUGH
MUCH OF THE DAY ALONG WITH LAPSE RATES AROUND 6 C/KM WEAK MID
LEVEL QG ASCENT...SNOW SHOULD CONTINUE INTO THE EVENING WITH
ANOTHER 3-6 INCHES. CURRENT ADVISORIES TO CONTINUE. SOME DECREASE
IN THE SNOW STILL EXPECTED OVERNIGHT AS ASCENT WEAKENS AND
SUBSIDENCE PREVAILS. ACROSS PLAINS...THE LIGHT SNOW OVER THE
NORTHEAST CORNER HAS ENDED WITH MOSTLY CLOUDY CONDITIONS
PREVAILING. LATEST MODELS CONTINUE TO SHOW WEAK DISTURBANCE MOVING
ACROSS THE CENTRAL PLAINS WITH WEAK UPSLOPE LOW DEVELOPING ALONG
THE FRONT RANGE. RAP/RUC SHOW SOME LIGHT PRECIP/QPF DEVELOPING
ACROSS THE NORTHERN FRONT RANGE AND PALMER DIVIDE AREA DURING THE
AFTERNOON WITH THE NORTHERN BATCH GRADUALLY SPREADING SOUTHWARD
BY EVENING. THERE STILL IS THE POTENTIAL FOR SOME LIGHT SNOW IN
AND NEAR THE FRONT RANGE. LATEST MODELS SEEM TO FAVOR THE NORTHERN
PORTIONS OF THE FRONT RANGE AS WELL AS NEAR THE FOOTHILLS AND
PALMER DIVIDE FOR THE MAIN AREA OF PRECIP. CONFIDENCE HAS IMPROVED
ENOUGH TO GO WITH LIKELY POPS ACROSS PORTIONS OF ZONE 38 AND
41...INCLUDING FOOTHILL LOCATIONS BETWEEN 21Z AND 03Z.
ACCUMULATIONS STILL LOOK TO BE LESS THAN AN INCH. REST OF
FORECASTS SEEM ON TRACK FOR NOW.
.AVIATION...STILL SOME STRATUS ALONG LOW LYING AREAS OF SOUTHERN
WELD COUNTY...SHOULD REMAIN IN THAT AREA AND NOT AFFECT THE
AIRPORTS. WINDS SHOWING MORE OF A SOUTHEAST COMPONENT. STILL SOME
CHANCE OF LIGHT SNOW BETWEEN 23Z AND 06Z. HOWEVER HAVE A LOW
CONFIDENCE IN A TEMPO GROUP AT THIS TIME AND WILL KEEP THE VCSH
WITH PERHAPS A PROB030 AFTER 03Z. WILL CONTINUE THE TREND OF THE
CURRENT TAFS AT THIS POINT. IF SNOW DOES AFFECT THE AREA
AIRPORTS...ACCUMULATIONS SHOULD BE LESS THAN AN INCH.
&&
.PREV DISCUSSION... /ISSUED 259 AM MST THU DEC 27 2012/
SHORT TERM...A BROAD CIRCULATION CENTER WAS LOCATED FM ERN WY
INTO WRN NE EARLY THIS MORNING AND WILL MOVE SLOWLY EASTWARD THRU
TONIGHT. OVERALL THE FLOW ALOFT IN THE MTNS WILL BE WNW WITH
FAVORABLE OROGRAPHICS THRU TONIGHT. LAPSE RATES WILL AVERAGE
AROUND 7 C/KM WITH MOISTURE DEPTH AROUND 300 MB SO SHOULD SEE
PERIODS OF SNOW WITH ACCUMULATIONS MEETING ADVISORY CRITERIA. OVER
NERN CO IT APPEARS ANY PCPN THRU LATE AFTN WILL BE CONFINED TO
THE FAR NERN CORNER MAINLY THIS MORNING. HOWEVER BY THIS EVENING A
DISTURBANCE WILL MOVE SSE ACROSS THE AREA WITH WEAK UPSLOPE FLOW
DEVELOPING ALONG THE FRONT RANGE. THUS COULD SEE A BREIF PERIOD OF
LIGHT SNOW IN AND NR THE FOOTHILLS AND OVER THE PALMER DIVIDE IN
THE 00Z-06Z TIMEFRAME. HAVE INCREASED POPS TO CHC CATEGORY HOWEVER
CONFIDENCE IS NOT HIGH ENOUGH AT THIS POINT TO GO LIKELY. AS FAR
AS HIGHS THIS AFTN READINGS ACROSS NERN CO WILL BE MAINLY IN THE
20S. AROUND DENVER COULD SEE A 10 DEGREE SPREAD IN HIGHS AS
INVERSION MAY BREAK OVER THE SRN SUBURBS ALLOWING FOR HIGHS IN
THE LOWER TO MID 30S WHILE OTHER AREAS AROUND DENVER STAY IN THE
MID TO UPPER 20S.
LONG TERM...ZONAL FLOW IS PROGGED OVER THE CWA FRIDAY...THEN
NORTHWESTERLY FLOW ALOFT IS PROGGED FOR FRIDAY NIGHT. AN UPPER
RIDGE IS PROGGED TO MOVE ACROSS COLORADO SATURDAY. THE FLOW ALOFT
IS ZONAL ON SATURDAY...THEN SOUTHWESTERLY SATURDAY NIGHT. THE QG
VERTICAL VELOCITY FIELDS HAVE DOWNWARD SYNOPTIC SCALE ENERGY OVER
THE CWA FRIDAY INTO SATURDAY MORNING. THE REST OF SATURDAY AND
SATURDAY NIGHT HAS WEAK UPWARD MOTION PROGGED. THE BOUNDARY LAYER
FLOW LOOKS TO BE DOMINATED BY DOWNSLOPING FRIDAY INTO SATURDAY
MORNING...THEN MORE NORMAL DUIRNAL PATTERNS ARE PROGGED FOR THE
REST OF SATURDAY AND SATURDAY NIGHT. FOR MOISTURE...THERE IS SOME
AROUND ON FRIDAY...ACTUALLY PRETTY DEEP OVER THE MOUNTAINS IN THE
MORNING. DRYING KICKS IN BY AFTERNOON...CONTINUING FRIDAY
EVENING. THE REST OF FRIDAY NIGHT AND SATURDAY LOOK PRETTY DRY FOR
ALL AREAS...MAYBE SOME HIGH CLOUDS. MOISTURE INCREASES SATURDAY
NIGHT...MOSTLY THE UPPER LEVEL TYPE. THE QPF FIELDS SHOW SMALL
AMOUNTS OF MEASURABLE PRECIPITATION ON FRIDAY IN THE MOUNTAINS
ONLY. FRIDAY NIGHT THROUGH SATURDAY NIGHT ARE DRY. SO FOR POPS
..WILL GO WITH 30-60%S IN THE MOUNTAINS ON FRIDAY. THERE IS
FAIRLY DECENT MOISTURE AND SOME HELP FROM OROGRAPHICS. JUST MINOR
POPS IN THE MOUNTAINS FRIDAY EVENING. NO POPS ELSEWHERE THROUGH
THE PERIODS. FOR TEMPERATURES...FRIDAY`S HIGHS ARE A TAD WARMER
THAN TODAY`S. SATURDAY`S WARM UP 2-4 C FROM FIRDAY`S HIGHS. FOR
THE LATER DAYS...SUNDAY THROUGH WEDNESDAY...SOUTHWESTERLY FLOW
ALOFT IS PROGGED SUNDAY INTO MONDAY. MODELS SHOW AN UPPER TROUGH
TO MOVE ACROSS THE FORECAST AREA LATE MONDAY INTO TUESDAY MORNING.
THE ECMWF AND GFS SHOW THE TROUGH IN PRETTY FAIR AGREEMENT.
HOWEVER...THE ECMWF HAS A CLOSED CIRCULATION AT IT`S BASE...THE
GFS DOES NOT HAVE THIS. SO BY TUESDAY...THE GFS HAS THE TROUGH
THROUGH THE CWA...WHILE THE ECMWF HAS A CLOSED CIRCULATION SOUTH
OF COLORADO. THIS UPPER LOW IS CENTERED NEAR EL PASO TEXAS LATE
WEDNESDAY. MOISTURE IS WAY DIFFERENT ON THE TWO MODELS....THE GFS
SHOWS QUITE A BIT OF MOISTURE FOR SUNDAY NIGHT AND MONDAY. THE
ECMWF DOWSN`T GET MOISTURE INTO THE CWA UNTIL MONDAY NIGHT AND
TUESDAY. POOR AGREEMENT HERE. LATER TUESDAY THROUGH WEDNESDAY LOOK
DRY ON BOTH MODELS. WILL KEEP POPS SOMEWHAT AT BAY DUE TO THE
UNCERTAINTIES.
AVIATION...STRATUS HAS REMAINED JUST TO THE NORTH OF THE AIRPORT OVER
SRN WELD COUNTY THE ENTIRE NIGHT AND SO FAR HAS SHOWN NO SIGNS OF
SPREADING SOUTH AT THIS POINT. BOTH THE RAP AND THE HRRR KEEP SHOW
SFC WINDS BECOMING MORE SLY BY SUNRISE SO IF THAT OCCURS THEN
STRATUS MAY NOT AFFECT THE AIRPORT. COULD SEE SOME PATCHY FOG
HOWEVER VISBILITIES LOOK TO BE AOA 5 MILES AT THIS POINT. BY
MIDDAY SFC WINDS WILL BECOME MORE ELY AND STAY THAT WAY THRU EARLY
EVENING. AS TALKED ABOUT ABV THERE COULD BE SOME LIGHT SNOW FOR A
FEW HOURS BETWEEN 00Z AND 06Z AS DISTURBANCE MOVES SSE ACROSS THE
AREA. AT THIS POINT ANY ACCUMULATION SHOULD BE LESS THAN AN INCH
IF SNOW DEVELOPS.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR COZ031-
033-034.
&&
$$
SHORT TERM...D-L
LONG TERM....RJK
AVIATION...D-L
AREA FORECAST DISCUSSION
NWS GRAND JUNCTION CO
955 AM MST THU DEC 27 2012
.UPDATE...
ISSUED AT 904 AM MST THU DEC 27 2012
ALLOWED THE WINTER WEATHER ADVISORIES FOR THE ERN UINTA BASIN AS
WELL AS THE CENTRAL AND SOUTHERN VALLEYS TO EXPIRE NORMALLY AT 9
AM THIS MORNING. COLD AND MOIST AIRMASS REMAINING OVER THE AREA
UNDER A BROAD TROUGH OVERHEAD AND WILL STILL KEEP SOME LIGHT SNOW
OR SNOW SHOWERS IN THE VALLEYS...BUT DO NOT EXPECT MUCH MORE
ACCUMULATION...ALTHOUGH MAY STILL SEE SOME LOCALIZED ACCUMS IN THE
ERN UINTA BASIN WHICH APPEARS TO BE UNDER A WEAK DEFORMATION AXIS
THAT EXTENDS ACROSS NW CO TO AN UPPER LOW OVER WRN NEBRASKA.
OCCASIONAL SNOW WILL CONTINUE OVER THE MOUNTAINS AND THE NW CO
PLATEAU AS FLOW SHIFTS FROM WEST THIS MORNING TO NORTHWEST THIS
AFTERNOON...AND WILL KEEP THOSE ADVISORIES IN FORCE. WEBCAMS
SHOWED BREAKS IN THE CLOUDS ACROSS THE SAN JUANS AND THE SOUTH
THIS MORNING...BUT HI-RESOLUTION HRRR MODEL INDICATES THIS TO FILL
BACK IN THIS AFTERNOON AS THE NEXT DISTURBANCE ROTATES THROUGH.
HAVE UPDATED THE WORDED AND FORECAST GRIDS TO REFLECT THIS
THINKING.
&&
.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 346 AM MST THU DEC 27 2012
A MESSY DISORGANIZED COLD WINTER STORM CONTINUES TO PRODUCE
WIDESPREAD BUT LIGHT SNOWFALL ACROSS THE FORECAST AREA. KEY TO THE
SNOW PRODUCTION IS A MOIST DENDRITIC GROWTH LAYER AT 700 TO 600MB
OR THE MTN TOP LAYER. DEVELOPING MID LEVEL CYCLONIC FLOW AND A
SHOT OF COLD ADVECTION TODAY WILL ALSO KEEP SNOW PRODUCTION
WIDESPREAD.
THE MAIN SYNOPTIC FEATURE IS THE CLOSED LOW OVER EASTERN WYOMING
THAT IS ROTATING SPOKES OF ENERGY MAINLY ACROSS THE NORTHERN
ZONES. THIS LOW WILL SHIFT EAST THIS MORNING WITH THE LAST
TRAILING DISTURBANCE AND SHOT OF COLD AIR ROTATING OVER THE
NORTHERN COLORADO MTNS. IN ADDITION THE 500-300MB SHEAR AXIS
REMAINS OVER THE SW SAN JUAN REGION THROUGH THE MORNING HOURS.
SANDWICHED BETWEEN THESE TWO LARGER SCALE FEATURES...THE CENTRAL
ZONES ARE ACCUMULATING THE LEAST SNOW AMOUNTS. IT WILL BE
DIFFICULT FOR GRAND JUNCTION AND MONTROSE TO ACCUMULATE 3 INCHES
OF SNOW...BUT WITH SNOWFALL CONTINUING WILL KEEP THE ADVISORIES
ACTIVE. OTHERWISE THE VEERING WINDS ALOFT FROM WEST TO NORTH WILL
PRODUCE SNOWFALL MAINLY ON NORTH FACING SLOPES WHERE SKI SLOPES
ARE LOCATED. THE CENTRAL VALLEYS COULD ALSO SEE A QUICK FEW INCHES
OF SNOWFALL IN THE LATE AFTERNOON INTO THE EARLY EVENING.
TONIGHT...NORTH FLOW CONTINUES WITH WEAK TRANSIENT RIDGING
BUILDING AFTER MIDNIGHT. IN SPITE OF THIS...LIGHT OROGRAPHIC
SNOWFALL IS EXPECTED FAVORING THE NORTHERN MTNS. FRIDAY...A DRIER
AIR MASS WORKS IN FROM WEST TO EAST WITH LIGHT SNOWFALL CONTINUING
ONLY IN THE EASTERN MTNS. WARM ADVECTION ALOFT BEGINS IN THE
AFTERNOON STRONGLY CAPPING THE COLD AIR IN THE VALLEYS.
.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 346 AM MST THU DEC 27 2012
SNOW COMES TO AN END OVER THE ENTIRE FORECAST AREA FRIDAY NIGHT AS
SHRTWV RIDGE WORKS EAST. THIS WILL BRING DRY CONDITIONS THROUGH
EARLY SUNDAY...BEFORE NEXT LONG WAVE TROUGH WORKS INTO THE WESTERN
U.S. MEDIUM RANGE MODELS STILL ON DIFFERENT PATHS IN REGARDS TO
THIS SPLITTING SYSTEM WITH THE ECMWF CONTINUING TO DRIVE THE
SOUTHERN EXTENT OF THE TROUGH SOUTH INTO THE BAJA REGION BY
SUNDAY...WITH SPLITTING NORTHERN ENERGY SLOWLY DROPPING SOUTHWEST
ACROSS THE WESTERN GREAT BASIN AND EVENTUALLY PHASING WITH THE
SOUTHERN STREAM...THEN EJECTING OUT BY MIDWEEK. THIS KEEPS PRECIP
OUT OF OUR REGION UNTIL LATER MONDAY WITH MAIN IMPACT ACROSS THE
SOUTHERN ZONES.
THE GFS ON THE OTHER HAND SPLITS THE TROUGH AS WELL...BUT FOCUS IS
ON THE NORTHERN STREAM WHICH DRIVES THROUGH THE FORECAST AREA AS A
POSITIVELY TILTED TROUGH SUNDAY NIGHT AND MONDAY...WHICH WOULD
BRING A GOOD CHANCE OF SNOW TO MUCH OF THE FORECAST AREA.
WITH THESE TWO OUT OF PHASE...DECIDED TO TAKE A CLOSER LOOK AT THE
CANADIAN AND OTHER ENSEMBLES AVAILABLE WHICH OFFERING MORE OF A
COMPROMISE BETWEEN THE TWO. SO WILL KEEP LOW POPS IN THE FORECAST
BEGINNING AS EARLY AS SUNDAY AFTERNOON AND PEAKING ON MONDAY. THE
GFS HAS MAINTAINED SOME CONSISTENCY OVER THE PAST FEW RUNS...SO
SOME INCREASE IN CONFIDENCE TOWARD THAT SOLUTION...BUT NOT ENOUGH
TO DRIVE POPS INTO THE LIKELY THRESHOLD.
BEYOND THIS EVENT...THE FORECAST REMAINS RATHER UNSETTLED WITH
ANOTHER FAST MOVING SYSTEM RUNNING THROUGH TUESDAY
AFTERNOON...FOLLOWED BY TRANSITORY RIDGING AT MIDWEEK WITH YET
ANOTHER SYSTEM POSSIBLE BY THE END OF THE WEEK.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 955 AM MST THU DEC 27 2012
SNOWFALL WILL RESULT IN MOUNTAIN OBSCURATIONS...AND MVFR CIGS AND
VSBY FOR THE NORTHERN AIRPORTS. IFR VSBY WILL BE POSSIBLE AT TIMES
IN HEAVIER SNOW. ALONG AND SOUTH OF I-70 SNOWFALL WILL GENERALLY
BE LIGHTER AND MORE SPORADIC. EXPECT PERIODS OF MVFR/ISOLD IFR
CONDITIONS THROUGH TODAY. WHILE CLOUD DECKS AT KEGE AND KRIL HAVE
OPENED UP THIS MORNING...CLOUDS WILL AGAIN INCREASE AND THICKEN
THIS AFTERNOON WITH SNOW SHOWERS DEVELOPING. THE FLOW TURNS TO
COLD NW THIS AFTERNOON AND EVENING WITH WIDESPREAD SNOWFALL ALONG
NORTH AND NORTHWEST FACING SLOPES THROUGH TONIGHT. OTHERWISE
IMPROVING CONDITIONS ARE EXPECTED. THESE OROGRAPHIC SNOW SHOWERS
WILL DIMINISH EARLY FRIDAY. AREAS OF FOG MAY RESULT IN MVFR OR IFR
CONDITIONS AT AREA AIRPORTS LATE TONIGHT AND FRIDAY MORNING.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR COZ001-
002-005.
WINTER WEATHER ADVISORY UNTIL 6 AM MST FRIDAY FOR COZ003-004-009-
010-012-013-017>019.
UT...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR UTZ023-
025-028.
&&
$$
UPDATE...JAD
SHORT TERM...JOE
LONG TERM...JDC
AVIATION...EH
AREA FORECAST DISCUSSION
NWS GRAND JUNCTION CO
906 AM MST THU DEC 27 2012
.UPDATE...
ISSUED AT 904 AM MST THU DEC 27 2012
ALLOWED THE WINTER WEATHER ADVISORIES FOR THE ERN UINTA BASIN AS WELL
AS THE CENTRAL AND SOUTHERN VALLEYS TO EXPIRE NORMALLY AT 9 AM
THIS MORNING. COLD AND MOIST AIRMASS REMAINING OVER THE AREA UNDER
A BROAD TROUGH OVERHEAD AND WILL STILL KEEP SOME LIGHT SNOW OR
SNOW SHOWERS IN THE VALLEYS...BUT DO NOT EXPECT MUCH MORE
ACCUMULATION...ALTHOUGH MAY STILL SEE SOME LOCALIZED ACCUMS IN
THE ERN UINTA BASIN WHICH APPEARS TO BE UNDER A WEAK DEFORMATION
AXIS THAT EXTENDS ACROSS NW CO TO AN UPPER LOW OVER WRN NEBRASKA.
OCCASIONAL SNOW WILL CONTINUE OVER THE MOUNTAINS AND THE NW CO
PLATEAU AS FLOW SHIFTS FROM WEST THIS MORNING TO NORTHWEST THIS
AFTERNOON...AND WILL KEEP THOSE ADVISORIES IN FORCE. WEBCAMS
SHOWED BREAKS IN THE CLOUDS ACROSS THE SAN JUANS AND THE SOUTH
THIS MORNING...BUT HI-RESOLUTION HRRR MODEL INDICATES THIS TO
FILL BACK IN THIS AFTERNOON AS THE NEXT DISTURBANCE ROTATES
THROUGH. HAVE UPDATED THE WORDED AND FORECAST GRIDS TO REFLECT
THIS THINKING.
&&
.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 346 AM MST THU DEC 27 2012
A MESSY DISORGANIZED COLD WINTER STORM CONTINUES TO PRODUCE
WIDESPREAD BUT LIGHT SNOWFALL ACROSS THE FORECAST AREA. KEY TO THE
SNOW PRODUCTION IS A MOIST DENDRITIC GROWTH LAYER AT 700 TO 600MB
OR THE MTN TOP LAYER. DEVELOPING MID LEVEL CYCLONIC FLOW AND A
SHOT OF COLD ADVECTION TODAY WILL ALSO KEEP SNOW PRODUCTION
WIDESPREAD.
THE MAIN SYNOPTIC FEATURE IS THE CLOSED LOW OVER EASTERN WYOMING
THAT IS ROTATING SPOKES OF ENERGY MAINLY ACROSS THE NORTHERN
ZONES. THIS LOW WILL SHIFT EAST THIS MORNING WITH THE LAST
TRAILING DISTURBANCE AND SHOT OF COLD AIR ROTATING OVER THE NORTHERN
COLORADO MTNS. IN ADDITION THE 500-300MB SHEAR AXIS REMAINS OVER
THE SW SAN JUAN REGION THROUGH THE MORNING HOURS. SANDWICHED
BETWEEN THESE TWO LARGER SCALE FEATURES...THE CENTRAL ZONES ARE
ACCUMULATING THE LEAST SNOW AMOUNTS. IT WILL BE DIFFICULT FOR
GRAND JUNCTION AND MONTROSE TO ACCUMULATE 3 INCHES OF SNOW...BUT
WITH SNOWFALL CONTINUING WILL KEEP THE ADVISORIES ACTIVE.
OTHERWISE THE VEERING WINDS ALOFT FROM WEST TO NORTH WILL PRODUCE
SNOWFALL MAINLY ON NORTH FACING SLOPES WHERE SKI SLOPES ARE
LOCATED. THE CENTRAL VALLEYS COULD ALSO SEE A QUICK FEW INCHES OF
SNOWFALL IN THE LATE AFTERNOON INTO THE EARLY EVENING.
TONIGHT...NORTH FLOW CONTINUES WITH WEAK TRANSIENT RIDGING
BUILDING AFTER MIDNIGHT. IN SPITE OF THIS...LIGHT OROGRAPHIC
SNOWFALL IS EXPECTED FAVORING THE NORTHERN MTNS. FRIDAY...A DRIER
AIR MASS WORKS IN FROM WEST TO EAST WITH LIGHT SNOWFALL CONTINUING
ONLY IN THE EASTERN MTNS. WARM ADVECTION ALOFT BEGINS IN THE
AFTERNOON STRONGLY CAPPING THE COLD AIR IN THE VALLEYS.
.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 346 AM MST THU DEC 27 2012
SNOW COMES TO AN END OVER THE ENTIRE FORECAST AREA FRIDAY NIGHT AS
SHRTWV RIDGE WORKS EAST. THIS WILL BRING DRY CONDITIONS THROUGH
EARLY SUNDAY...BEFORE NEXT LONG WAVE TROUGH WORKS INTO THE WESTERN
U.S. MEDIUM RANGE MODELS STILL ON DIFFERENT PATHS IN REGARDS TO
THIS SPLITTING SYSTEM WITH THE ECMWF CONTINUING TO DRIVE THE
SOUTHERN EXTENT OF THE TROUGH SOUTH INTO THE BAJA REGION BY
SUNDAY...WITH SPLITTING NORTHERN ENERGY SLOWLY DROPPING SOUTHWEST
ACROSS THE WESTERN GREAT BASIN AND EVENTUALLY PHASING WITH THE
SOUTHERN STREAM...THEN EJECTING OUT BY MIDWEEK. THIS KEEPS PRECIP
OUT OF OUR REGION UNTIL LATER MONDAY WITH MAIN IMPACT ACROSS THE
SOUTHERN ZONES.
THE GFS ON THE OTHER HAND SPLITS THE TROUGH AS WELL...BUT FOCUS IS
ON THE NORTHERN STREAM WHICH DRIVES THROUGH THE FORECAST AREA AS A
POSITIVELY TILTED TROUGH SUNDAY NIGHT AND MONDAY...WHICH WOULD
BRING A GOOD CHANCE OF SNOW TO MUCH OF THE FORECAST
AREA.
WITH THESE TWO OUT OF PHASE...DECIDED TO TAKE A CLOSER LOOK AT THE
CANADIAN AND OTHER ENSEMBLES AVAILABLE WHICH OFFERING MORE OF A
COMPROMISE BETWEEN THE TWO. SO WILL KEEP LOW POPS IN THE FORECAST
BEGINNING AS EARLY AS SUNDAY AFTERNOON AND PEAKING ON MONDAY. THE
GFS HAS MAINTAINED SOME CONSISTENCY OVER THE PAST FEW RUNS...SO
SOME INCREASE IN CONFIDENCE TOWARD THAT SOLUTION...BUT NOT ENOUGH
TO DRIVE POPS INTO THE LIKELY THRESHOLD.
BEYOND THIS EVENT...THE FORECAST REMAINS RATHER UNSETTLED WITH
ANOTHER FAST MOVING SYSTEM RUNNING THROUGH TUESDAY
AFTERNOON...FOLLOWED BY TRANSITORY RIDGING AT MIDWEEK WITH YET
ANOTHER SYSTEM POSSIBLE BY THE END OF THE WEEK.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 346 AM MST THU DEC 27 2012
PERIODS OF MODERATE SNOWFALL WILL CONTINUE NORTH OF THE I-70
CORRIDOR THROUGH 18Z THEN DIMINISH IN COVERAGE. SNOWFALL WILL
RESULT IN MOUNTAIN OBSCURATIONS AND MVFR CIGS AND VSBY FOR KVEL
KCAG KSBS. SOUTH OF I-70 SNOWFALL WILL GENERALLY BE LIGHTER AND
MORE SPORADIC. EXPECT PERIODS OF MVFR/ISOLD IFR CONDITIONS THROUGH
TODAY. THE FLOW TURNS TO COLD NW THIS AFTERNOON AND EVENING
WITH WIDESPREAD SNOWFALL ALONG NORTH AND NORTHWEST FACING SLOPES.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR COZ001-
002-005.
WINTER WEATHER ADVISORY UNTIL 6 AM MST FRIDAY FOR COZ003-004-009-
010-012-013-017>019.
UT...WINTER WEATHER ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR UTZ023-
025-028.
&&
$$
UPDATE...JAD
SHORT TERM...JOE
LONG TERM...JDC
AVIATION...JOE+EH
AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
259 AM MST THU DEC 27 2012
.SHORT TERM...A BROAD CIRCULATION CENTER WAS LOCATED FM ERN WY
INTO WRN NE EARLY THIS MORNING AND WILL MOVE SLOWLY EASTWARD THRU
TONIGHT. OVERALL THE FLOW ALOFT IN THE MTNS WILL BE WNW WITH
FAVORABLE OROGRAPHICS THRU TONIGHT. LAPSE RATES WILL AVERAGE
AROUND 7 C/KM WITH MOISTURE DEPTH AROUND 300 MB SO SHOULD SEE
PERIODS OF SNOW WITH ACCUMULATIONS MEETING ADVISORY CRITERIA. OVER
NERN CO IT APPEARS ANY PCPN THRU LATE AFTN WILL BE CONFINED TO
THE FAR NERN CORNER MAINLY THIS MORNING. HOWEVER BY THIS EVENING A
DISTURBANCE WILL MOVE SSE ACROSS THE AREA WITH WEAK UPSLOPE FLOW
DEVELOPING ALONG THE FRONT RANGE. THUS COULD SEE A BREIF PERIOD OF
LIGHT SNOW IN AND NR THE FOOTHILLS AND OVER THE PALMER DIVIDE IN
THE 00Z-06Z TIMEFRAME. HAVE INCREASED POPS TO CHC CATEGORY HOWEVER
CONFIDENCE IS NOT HIGH ENOUGH AT THIS POINT TO GO LIKELY. AS FAR
AS HIGHS THIS AFTN READINGS ACROSS NERN CO WILL BE MAINLY IN THE
20S. AROUND DENVER COULD SEE A 10 DEGREE SPREAD IN HIGHS AS
INVERSION MAY BREAK OVER THE SRN SUBURBS ALLOWING FOR HIGHS IN
THE LOWER TO MID 30S WHILE OTHER AREAS AROUND DENVER STAY IN THE
MID TO UPPER 20S.
.LONG TERM...ZONAL FLOW IS PROGGED OVER THE CWA FRIDAY...THEN
NORTHWESTERLY FLOW ALOFT IS PROGGED FOR FRIDAY NIGHT. AN UPPER
RIDGE IS PROGGED TO MOVE ACROSS COLORADO SATURDAY. THE FLOW ALOFT
IS ZONAL ON SATURDAY...THEN SOUTHWESTERLY SATURDAY NIGHT. THE QG
VERTICAL VELOCITY FIELDS HAVE DOWNWARD SYNOPTIC SCALE ENERGY OVER
THE CWA FRIDAY INTO SATURDAY MORNING. THE REST OF SATURDAY AND
SATURDAY NIGHT HAS WEAK UPWARD MOTION PROGGED. THE BOUNDARY LAYER
FLOW LOOKS TO BE DOMINATED BY DOWNSLOPING FRIDAY INTO SATURDAY
MORNING...THEN MORE NORMAL DUIRNAL PATTERNS ARE PROGGED FOR THE
REST OF SATURDAY AND SATURDAY NIGHT. FOR MOISTURE...THERE IS SOME
AROUND ON FRIDAY...ACTUALLY PRETTY DEEP OVER THE MOUNTAINS IN THE
MORNING. DRYING KICKS IN BY AFTERNOON...CONTINUING FRIDAY
EVENING. THE REST OF FRIDAY NIGHT AND SATURDAY LOOK PRETTY DRY FOR
ALL AREAS...MAYBE SOME HIGH CLOUDS. MOISTURE INCREASES SATURDAY
NIGHT...MOSTLY THE UPPER LEVEL TYPE. THE QPF FIELDS SHOW SMALL
AMOUNTS OF MEASURABLE PRECIPITATION ON FRIDAY IN THE MOUNTAINS
ONLY. FRIDAY NIGHT THROUGH SATURDAY NIGHT ARE DRY. SO FOR POPS
...WILL GO WITH 30-60%S IN THE MOUNTAINS ON FRIDAY. THERE IS
FAIRLY DECENT MOISTURE AND SOME HELP FROM OROGRAPHICS. JUST MINOR
POPS IN THE MOUNTAINS FRIDAY EVENING. NO POPS ELSEWHERE THROUGH
THE PERIODS. FOR TEMPERATURES...FRIDAY`S HIGHS ARE A TAD WARMER
THAN TODAY`S. SATURDAY`S WARM UP 2-4 C FROM FIRDAY`S HIGHS. FOR
THE LATER DAYS...SUNDAY THROUGH WEDNESDAY...SOUTHWESTERLY FLOW
ALOFT IS PROGGED SUNDAY INTO MONDAY. MODELS SHOW AN UPPER TROUGH
TO MOVE ACROSS THE FORECAST AREA LATE MONDAY INTO TUESDAY MORNING.
THE ECMWF AND GFS SHOW THE TROUGH IN PRETTY FAIR AGREEMENT.
HOWEVER...THE ECMWF HAS A CLOSED CIRCULATION AT IT`S BASE...THE
GFS DOES NOT HAVE THIS. SO BY TUESDAY...THE GFS HAS THE TROUGH
THROUGH THE CWA...WHILE THE ECMWF HAS A CLOSED CIRCULATION SOUTH
OF COLORADO. THIS UPPER LOW IS CENTERED NEAR EL PASO TEXAS LATE
WEDNESDAY. MOISTURE IS WAY DIFFERENT ON THE TWO MODELS....THE GFS
SHOWS QUITE A BIT OF MOISTURE FOR SUNDAY NIGHT AND MONDAY. THE
ECMWF DOWSN`T GET MOISTURE INTO THE CWA UNTIL MONDAY NIGHT AND
TUESDAY. POOR AGREEMENT HERE. LATER TUESDAY THROUGH WEDNESDAY LOOK
DRY ON BOTH MODELS. WILL KEEP POPS SOMEWHAT AT BAY DUE TO THE
UNCERTAINTIES.
&&
.AVIATION...STRATUS HAS REMAINED JUST TO THE NORTH OF THE AIRPORT OVER
SRN WELD COUNTY THE ENTIRE NIGHT AND SO FAR HAS SHOWN NO SIGNS OF
SPREADING SOUTH AT THIS POINT. BOTH THE RAP AND THE HRRR KEEP SHOW
SFC WINDS BECOMING MORE SLY BY SUNRISE SO IF THAT OCCURS THEN
STRATUS MAY NOT AFFECT THE AIRPORT. COULD SEE SOME PATCHY FOG
HOWEVER VISBILITIES LOOK TO BE AOA 5 MILES AT THIS POINT. BY
MIDDAY SFC WINDS WILL BECOME MORE ELY AND STAY THAT WAY THRU EARLY
EVENING. AS TALKED ABOUT ABV THERE COULD BE SOME LIGHT SNOW FOR A
FEW HOURS BETWEEN 00Z AND 06Z AS DISTURBANCE MOVES SSE ACROSS THE
AREA. AT THIS POINT ANY ACCUMULATION SHOULD BE LESS THAN AN INCH
IF SNOW DEVELOPS.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR COZ031-
033-034.
&&
$$
SHORT TERM...RPK
LONG TERM....RJK
AVIATION...RPK
AREA FORECAST DISCUSSION
NWS ALBANY NY
804 AM EST THU DEC 27 2012
.SYNOPSIS...
A WINTER STORM WILL PASS SOUTH OF LONG ISLAND TODAY AND INTO THE
GULF OF MAINE TONIGHT. WEAK HIGH PRESSURE WILL BUILD INTO THE
REGION FOR FRIDAY. SATURDAY ANOTHER LOW WILL ORGANIZE ALONG THE
CAROLINA COAST...AND MOVE NORTHEAST INTO THE ATLANTIC. IT WILL
BRING THE THREAT OF SOME LIGHT SNOW. COLDER AIR WILL SURGE INTO
THE REGION TO END THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS OF 8 AM...
MESOSCALE BANDING FEATURES ARE BECOMING MORE APPARENT PER THE
LATEST SCANS OF THE RADAR AND THE RUC13 LOW LEVEL CONVERGENCE
FIELDS SHOW AN INCREASING ACROSS THE HUDSON RIVER VALLEY. THIS
WILL ENHANCE THE SNOWFALL RATES THIS MORNING. FURTHERMORE...PER
CSTAR RESEARCH...MOHAWK VALLEY CONVERGENCE MAY ALSO CONTRIBUTE TO
ENHANCED LIFT WITHIN THE CAPITAL REGION. 989MB SURFACE LOW WAS
JUST SOUTH OF LONG ISLAND AS THIS IS A FAVORED TRACK FOR MODERATE
TO HEAVY PRECIPITATION WITH ENHANCED CONVERGENCE ACROSS THE HUDSON
RIVER VALLEY. WE WILL CONTINUE TO MONITOR CLOSELY.
PER DUAL POL RADAR DATA...THERE APPEARS TO BE A MIX
DEVELOPING/ONGOING ACROSS THE BERKSHIRES AND LITCHFIELD COUNTY.
THIS WILL HAVE AN IMPACT ON SNOW ACCUMULATIONS AS WELL...
PREV DISC..
...MAJOR WINTER STORM CONTINUES TO IMPACT EASTERN NEW YORK AND
WESTERN NEW ENGLAND...
AS OF 630 AM EST...SNOWFALL HAS BECOME QUITE PATCHY...WITH LARGE
AREAS WITHIN THE IMMEDIATE HUDSON VALLEY AND TACONICS EXPERIENCING
VERY LIGHT PRECIPITATION. ANOTHER MORE ORGANIZED BAND OF MODERATE
TO LOCALLY HEAVY PRECIPITATION IS NOW PIVOTING NORTHWEST FROM THE
MID HUDSON VALLEY...NW CT AND SOUTHERN BERKSHIRE CO. THIS BAND
WILL LIKELY CONTINUE SLOWLY ADVANCING NORTHWEST...AND MAY TAKE ON
A MORE NORTH-SOUTH ORIENTATION SHORTLY AFTER SUNRISE THROUGH MID
MORNING. WE WILL HAVE TO WATCH FOR THIS IN CASE IT STALLS...AND
PRODUCES LOCALLY HEAVY SNOWFALL ONCE AGAIN WITHIN THE HUDSON RIVER
VALLEY. WE DO EXPECT ANOTHER 3-6 INCHES IN MOST AREAS FROM THE
CAPITAL REGION NORTH AND WEST...AS WELL AS INTO THE BERKSHIRES AND
SOUTHERN GREENS...AND EASTERN CATSKILLS/HELDERBERGS...WITH LOCALLY
HIGHER AMTS POSSIBLE...ESP ACROSS HIGHER ELEVATIONS. FURTHER SOUTH
AND EAST...ACROSS THE SOUTHERN BERKSHIRES...TACONICS...NW CT...AND
MID HUDSON VALLEY REGION...A FEW MORE BURSTS OF MIXED
PRECIPITATION...SOME SNOW...SLEET AND FREEZING RAIN...WILL OCCUR
OVER THE NEXT 3 HOURS...BEFORE GRADUALLY TAPERING OFF. IN THESE
AREAS...AN ADDITIONAL COATING TO ONE TENTH OF AN INCH OF ICE
ACCRETION...ALONG WITH UP TO AN INCH OF SNOWFALL IS POSSIBLE.
NOON THROUGH SUNSET...THE DEFORMATION AREA SHOULD CONTINUE
TRANSLATING EASTWARD INTO NEW ENGLAND. HOWEVER...THERE IS A
POSSIBILITY THAT HUDSON-MOHAWK CONVERGENCE...WHICH IS LOW LEVEL
CONVERGENCE THAT OCCURS IN THE WAKE OF DEPARTING COASTAL LOWS FROM
THE COMBINATION OF A DEVELOPING WEST/NORTHWEST WIND DOWN THE
MOHAWK VALLEY...AND A LINGERING N/NE FLOW DOWN THE HUDSON RIVER
VALLEY...MAY LEAD TO ANOTHER 1-2 INCHES OF SNOWFALL IN THE
IMMEDIATE CAPITAL REGION.
OTHERWISE...FOR TEMPS...HAVE GONE COOLER THAN BOTH THE MAV AND MET
MOS...WITH MAXES ONLY REACHING 30-35 IN VALLEY REGIONS...WITH 20S
ACROSS HIGHER ELEVATIONS. IT WILL BE WARMER INITIALLY ACROSS S/E
AREAS THIS MORNING...FROM PORTIONS OF WESTERN MA INTO NW CT AND
THE MID HUDSON VALLEY...WITH TEMPS POSSIBLY FALLING THEREAFTER.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
DEPARTING STORM IS VERTICALLY STACKED AND LIFTING ENE INTO GULF
OF MAINE TNGT. BRISK N GRADIENT WILL GRADUALLY DIMINISH OVRNT.
RESIDUAL LLVL MOISTURE WILL KEEP -SHSN GOING MAINLY N...BUT WITH
LITTLE ADDITIONAL ACCUMULATION.
FRIDAY 500HPA RIDGE BUILDS ACROSS RGN ALONG WITH WK SFC HIGH. WITH
WK FLOW CONSIDERABLE LLVL MOISTURE AND LOW SUN ANGLE AND INVERSION
DEGREE OF SUN WILL BE IN QUESTION. MET IS MC AND MAV PS. IN ANY
CASE FRI WILL BE A SHORT REPRIEVE WITH NR NORMAL TEMPS.
FRIDAY NIGHT THE RIDGE AT 500HPA AND SFC SLIDES OFFSHORE AND 500HPA
TROF MOVES EAST INTO MIDWEST AND GRTLKS. IN RESPONSE SFC LOW PRESSURE
ORGANIZES ALONG THE CAROLINA COAST. THERE REMAINS SOME SPREAD IN
HOW THE MODELS DEVELOP THIS TROF. THE NAM IS FLAT...THE GEM THE
SHARPEST THE GFS BTWN THEM. THE ECMWF IS SIMILAR TO GFS...BUT HAS
SFC LOW BOMBING CLOSER TO THE COAST. THE END RESULT IS DIFFERENCES
IN THE EVOLVING WX SYSTEMS. THE NAM RESULTS IN A RATHER NON
DISCRIPT SOLUTION WITH BULK OF IMPACTS OF THE TROF PASSING SOUTH
OF RGN AS IT NEVER REALLY ORGANIZES. THE GEM/GFS/ECMWF DVLP A COASTAL
LOW THAT ALONG WITH THE 500 HPA TROF DEVELOP A WIDESPREAD AREA OF
OVERRUNNING LT SNOW DURING THE DAY SAT. WITH HALF THE GFS ENSEMBLE
MEMBERS SUPPORTING THE COUPLE OF TENTHS OF QPF AND LT SNOW...WILL
POPULATE WITH PERIOD WITH GMOS. THIS EVENT HAS BEEN SUBJECT TO
CONSIDERABLE SPREAD OVER THE PAST FEW DAYS...AND THIS CONTINUES.
THE MAIN CHANGE IS THE SIGNAL THAT SOMETHING WILL HAPPEN IS
STRONGER.
THIS SFC LOW PASSES WELL SOUTH OF RGN SO PTYPE IS NOT A CONCERN IT
WILL BE SNOW WHERE IT PRECIPITATES. AMOUNTS WILL BE GREATER
SOUTH...BUT AT THIS TIME THIS EVENT WILL BE A FEW INCHES OF SNOW AT
MOST AND SUB FLAG LEVEL. SAT NT THE SFC LOW WILL DEPART...BUT THE
500 HPA TROF WILL LINGER ALONG THE SEABOARD. THE COMBINATION WILL
ALLOW COLDER AIR OVER ONTARIO AND QUEBEC TO BE DRAWN S INTO FCA AS
SFC GRADIENT STRENGTHEN IN WAKE OF DEPARTING STORM.
CAA...RESIDUAL LLVL MOISTURE...TRRN AND AND SOME FORCING FROM TROF
ALOFT WILL KEEP THREAT OF -SHSN MAINLY N & W OF ALB SAT NT. SFC
FLOW FM N WILL MINIMIZE IMPACT OF LKS IN THIS. WHILE MAIN SFC HIGH
WILL BE OVER THE MISS/OHIO VLYS SUNDAY A SECONDARY COLDER CORE SFC
HIGH WILL BE OVER ONT WITH WK CDFNT DRAPED INTO RGN SUNDAY. SUNDAY
WILL BE A COLD DAY WITH BLO NORMAL TEMPS LOWS SINGLE DIGITS TO
TEENS HIGHS 20S. WITH MILDER AIR MASS OVER SE USA AND COLD AIR
MASS OVER S TIER OF CANADA...A 170KT 250HPA JET WILL DEVELOP FM
GRTKLS INTO MID ATLC STATES.
&&
.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
THERE CONTINUES TO BE SPREAD AS TO HOW COLD THIS PERIOD WILL BE
THE PAST FEW RUNS. THE GFS IS MILDER THAN THE REST OF THE GUID
SUITE. HWVR THE SOLUTIONS ARE CONVERGING FM PAST FEW DAYS.
COASTAL LOW DEPARTS SUNDAY NIGHT WITH ANOTHER WEAK SFC HIGH
PRESSURE AREA CRESTING OVR RGN MON. MON NT AND EARLY TUES YET
ANOTHER 500HPA TROF PUSHES ACROSS THE RGN DRAGGING AN ARCTIC CDFNT
THROUGH FCA. PASSAGE EITHER MON NT AND TUES....FOLLOWED BY ANOTHER
BURST OF CAA. AGAIN THIS PERIOD FEATURES MAINLY N-NNW WINDS...SO
SCT -SHSN WILL BE RESULT OF 500HPA TROF...LLVL MOISTURE AND
FOCUSED ALONG CDFNT. LKS WILL AGAIN NOT BE MUCH IN THE PICTURE
FOR OUR FCA. DETAILS GET KINDA MUDDIED BYND MONDAY...BUT IT WILL
BE A COLD...VRBL CLOUDS WITH SCT-BKN -SHSN. TEMPS WILL BE BLO
NORMAL MON AND FALLING OFF THE CLIFF THRU THE PERIOD TO 10-15 DEG
BLO NORMALS. WILL POPULATE WITH HPC MIDNIGHT GRIDS. THE GFS
CONTINUES TO BE THE MILDER OF THE MODELS FOR THIS PERIOD BUT WITH
BOTH THE ECMWF/GEM AND HPC FAVORING A COLDER SOLUTION WILL ELAN
TWRD THAT AND MAINTAIN CONSISTENCY WITH CURRENT FCST.
&&
.AVIATION /13Z THURSDAY THROUGH MONDAY/...
DESPITE THE RELATIVE STRENGTH OF THE SURFACE LOW MOVING OFF THE MID
ATLANTIC COAST...THE PCPN SHIELD ASSOCIATED WITH THIS LOW HAS NOT
BEEN VERY UNIFORM WITH CONDITIONS RANGING FROM AREAS OF HEAVY SNOW
TO LITTLE OR NO PCPN FALLING DURING THE NIGHT. THIS PATTERN PERSISTS
THIS MORNING...MAKING AVIATION FORECASTING DIFFICULT. WILL FORECAST
MVFR TO OCCASIONALLY IFR CONDITIONS AT THE KGFL/KALB/KPOU/KPSF TAF
SITES THROUGH EARLY OR MID AFTERNOON. BUT CONDITIONS COULD ALSO
BRIEFLY BE VFR AT ANY OF THE TAF SITES DUE TO HOLES IN THE PCPN
SHIELD. PCPN WILL BE FORECAST AS JUST SNOW AT THE KALB/KGFL TAF
SITES...ALTHOUGH SOME SLEET COULD MIX IN AT KALB. AT KPOU MAINLY
RAIN IS FORECAST WITH OCCASIONAL PERIOD OF FREEZING RAIN/SLEET/SNOW.
SNOW OR SLEET IS FORECAST AT KPSF.
BY MID OR LATE AFTN EXPECT PCPN TO BE SCT TO NUMEROUS SNOW SHOWERS
WITH MAINLY MVFR CONDITIONS. MVFR/VFR CIGS AT THE TAF SITES AFTER
28/00Z WITH LITTLE OR NO ADDITIONAL PCPN EXPECTED...AND AFTER 06Z
VFR CONDITIONS EXPECTED AT ALL THE TAF SITES THROUGH THE END OF THE
TAF PERIOD (28/12Z).
SURFACE WINDS WILL BE NORTHERLY AT KGFL/KALB/KPOU THROUGH THIS
SUNDAY MORNING AT 10 TO 12 KTS WITH GUSTS UP TO 20 KTS. AT KPSF
WINDS WILL BE NORTHEAST AT 10 TO 15 KTS WITH GUSTS UP TO AROUND 25
KTS POSSIBLE. DURING THE DAY WINDS WILL GRADUALLY SHIFT TO NORTHWEST
AT 10 TO 15 KTS WITH GUSTS TO 20 TO 25 KTS AT ALL THE TAF
SITES...AND CONTINUE THAT WAY INTO SUNDAY EVENING...GRADUALLY
DIMINISHING SOMEWHAT OVERNIGHT.
OUTLOOK...
FRI-FRI NT...VFR. NO SIG WX.
SAT-MON...VFR/MVFR. CHC -SHSN.
&&
.HYDROLOGY...
A MAJOR WINTER STORM IMPACTING THE REGION INTO TODAY WITH MAINLY
MODERATE TO HEAVY SNOW. SLEET...FREEZING RAIN...AND RAIN ARE
EXPECTED MAINLY SOUTH AND EAST OF ALBANY...WHERE PRECIPITATION
TYPE WILL BE MOST VARIED. WITH THE BULK OF PRECIPITATION IN THE
HYDRO SERVICE AREA /HSA/ SNOW...OR FROZEN...THERE SHOULD BE
MINIMAL HYDROLOGIC RESPONSE...EXCEPT SOME MODEST WITHIN BANK RISES
IN SOUTHEASTERN NEW YORK AND LITCHFIELD COUNTY CONNECTICUT.
WE WILL HAVE TO MONITOR THE FLOOD STAGE AT POUN6..AS IT IS FORECAST
TO NICK IT WITH THE E/SE WINDS LATE THIS MORNING. IT MAY FALL
SHORT.
THURSDAY NIGHT INTO SATURDAY WILL HAVE SOME SCATTERED SNOW
SHOWERS MAINLY NORTH AND WEST OF THE CAPITAL REGION. SOME LIGHT
SNOW IS POSSIBLE LATE SATURDAY INTO SUNDAY. THE NEW WEEK WILL BE
MUCH COLDER...AND ICE MAY BEGIN TO FORM ON RIVERS AND LAKES OVER
THE HSA.
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...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR CTZ001-
013.
NY...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR NYZ032-
033-038>043-047>054-058>061-063-082>084.
WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
NYZ064>066.
MA...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MAZ001-
025.
VT...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR
VTZ013>015.
&&
$$
SYNOPSIS...SNYDER
NEAR TERM...KL/BGM/WASULA
SHORT TERM...SNYDER
LONG TERM...SNYDER
AVIATION...GJM
HYDROLOGY...SNYDER
AREA FORECAST DISCUSSION
NWS TALLAHASSEE FL
439 AM EST Thu Dec 27 2012
.NEAR TERM [Through Tonight]...
Quiet weather is shaping up for today as cool high pressure builds
into the area. Morning cloud cover should gradually erode during
the day with skies expected to be mostly clear areawide by
tonight. The cool airmass is expected to keep high temperatures
below average this afternoon.
Heading into tonight, as the surface ridge moves closer to the
area, decent radiational cooling conditions are expected. Lows are
expected to bottom out near freezing over a large portion of the
area away from the coast with the coldest readings over the
southeast big bend. Areas of frost look likely away from the coast
and are mentioned in the forecast.
&&
.SHORT TERM [Friday Through Saturday]...
The pattern is expected to remain progressive through the short
term with the next shortwave arriving late Friday into Saturday
morning. An area of low pressure is expected to develop near the
Gulf coast and move eastward through the area. Model agreement is
fairly good on the timing of this system, so PoPs were bumped up
to 70-80 percent on Friday night. A warm front is expected to
straddle the coast with the greatest surface based instability
remaining just offshore. However, there appears to be enough
elevated instability to keep some chances of thunder over most of
the area. In fact, if the 00z NAM instability forecast verifies,
then there could be some stronger storms over the coastal waters
with favorable shear for organized convection. It is worth keeping
an eye on this to make sure there doesn`t end up being a low end
threat for a stronger storm along the coastline, but right now the
threat seems limited.
&&
.LONG TERM [Saturday Night through next Thursday]...
The period will begin with another Sfc Low exiting our region
quickly to the NE with a strong and cold Ridge of High Pressure
building in from the NW. This Ridge is expected to strengthen to
between 1030 and 1035mb and will be situated right over the CWA on
Sunday and Monday. This will set the stage for a possible short
duration light freeze on Sunday morning, with a likely long
duration light freeze (with a poss. Hard Freeze in some colder
locations) for Monday morning. Daytime highs on Sun. and Mon. will
also be held down several degrees below climo. For the remainder
of the period, however, an extended period of unsettled conditions
appears likely, as a series of weak waves of low pressure ride
E-NE along an elongated boundary. This boundary will be fairly
close to stationary over our CWA Mon. Night through Wed. Night, as
it will be essentially trapped between a strong Upper Ridge over
the SE Gulf of Mexico, and a weak Upper Trof swinging in from the
NW. At this time, this setup would favor periods of beneficial
rain over our area, with any Tstms appearing unlikely. It should
be noted, however, that the GFS and CMC are in good agreement with
this scenario (which we are fcsting), while the past 2 runs of the
ECMWF are much slower with moisture advection, holding off the
next batch of rain until Wed. Night and Thurs.
&&
.AVIATION...
[Through 06Z Friday] A rather large area of MVFR level Cigs have
overtaken all of the terminals except ECP early this morning, but it
will only a matter of time before these low clouds envelop ECP as
well. This setup is shown very well on the NARRE and HRRR Hi-Res
Models, while the numerical guidance from the large scale models is
way off base once again. These Cigs should begin to break and
scatter out by 14Z this morning, with VFR conditions and light winds
expected to prevail at all of the Taf Sites for the remainder of the
period.
&&
MARINE...
Winds and seas will continue diminishing today as high pressure
builds south toward the marine area. The next storm system will
begin to develop across the Gulf on Friday evening with winds and
seas expected to reach advisory levels this weekend.
&&
.FIRE WEATHER...
Although afternoon relative humidities will be noticeably lower
today and Friday, they are not expected to be low enough (and ERCs
will not be high enough) to cause any concerns. With another
wetting rainfall expected on Friday night and Saturday, no Red
Flag concerns are expected for the next several days.
&&
.HYDROLOGY...
Area rivers are expected to remain below flood stage for the next
several days. A general half inch to one inch of rain is expected on
Friday night into Saturday with the highest amounts expected to be
near the coast.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 56 32 62 53 67 / 0 0 10 80 40
Panama City 55 41 62 56 65 / 0 0 20 80 30
Dothan 52 35 60 50 61 / 0 0 10 70 30
Albany 54 32 60 46 64 / 0 0 10 70 40
Valdosta 55 32 62 51 64 / 0 0 10 80 60
Cross City 58 31 63 53 70 / 0 0 0 80 60
Apalachicola 54 40 61 57 68 / 0 0 20 80 40
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...FREEZE WATCH from late tonight through Friday morning for
Inland Dixie-Inland Taylor-Lafayette-Madison.
GA...None.
AL...None.
GM...None.
&&
$$
Near Term/Short Term/Marine/Hydrology...DVD
Long Term/Aviation/Fire Wx...Gould
AREA FORECAST DISCUSSION
NWS TAMPA BAY RUSKIN FL
415 AM EST THU DEC 27 2012
...MODERATE RISK OF RIP CURRENTS THROUGH THIS AFTERNOON FOR SUNCOAST
BEACHES...
...FREEZE WATCH LATE TONIGHT THROUGH EARLY FRIDAY MORNING FOR LEVY
AND CITRUS COUNTIES...
.SYNOPSIS...
08Z WATER VAPOR AND H4 RAP ANALYSIS SHOWING AN ACTIVE UPPER LEVEL
PATTERN IN PLACE ACROSS THE CONUS EARLY THIS MORNING. FROM WEST TO
EAST...NORTHERN STREAM FLOW CARVES OUT LONGWAVE TROUGHING FROM THE
PACIFIC COAST THROUGH THE INTERMOUNTAIN WEST BEFORE RIDGING BACK TO
THE NORTH OVER THE CENTRAL PLAINS/UPPER MIDWEST. THE FLOW THEN
SHARPLY TURNS BACK TO THE SOUTH INTO A NEGATIVELY TILTED LONGWAVE
TROUGH PIVOTING UP THE EASTERN SEABOARD. THIS IMPRESSIVE ENERGY IS
SUPPORTING AN ORGANIZED SURFACE LOW NEAR THE SOUTHERN NEW ENGLAND
COAST AND A WIDE SWATH OF COASTAL RAIN/INLAND SNOW. CLOSER TO
HOME...EASTERN U.S. TROUGH HAS EXITED OUR REGION WITH A ZONAL FLOW
NOW IN PLACE OVER THE GULF / FL PENINSULA. THIS ZONAL FLOW WILL HOLD
FOR THE NEXT 24/36 HOURS...AND EVEN RIDGE UP SLIGHTLY IN RESPONSE TO
HEIGHT FALLS EXPANDING ACROSS THE SOUTHERN PLAINS TOWARD THE LOWER
MS VALLEY.
AT THE SURFACE...WEDNESDAYS COLD FRONT IS NOW WELL TO THE EAST AND
SOUTH OF THE FORECAST AREA...AND A DRIER AND COOLER AIRMASS HAS
ARRIVED IN ITS WAKE. TIGHT GRADIENT THAT HAS BEEN IN PLACE SINCE THE
FRONTAL PASSAGE IS BEGINNING TO WEAKEN AS CONTINENTAL HIGH PRESSURE
CURRENTLY CENTERED OVER THE LOWER MS VALLEY BEGINS TO RIDGE IN FROM
THE NORTHWEST. SEASONABLY COOL TEMPERATURES OUT THERE THIS
MORNING...BUT NOT COLD...AS THE TIGHTER GRADIENT HAS HELPED KEEP
READINGS UP. ONLY EXCEPTION IS UP TOWARD CITRUS/LEVY/SUMTER WHERE
WINDS HAVE ALREADY SLACKENED AND COLDER LOCATIONS ARE IN THE 30S.
&&
.SHORT TERM (TODAY THROUGH SATURDAY)...
TODAY/TONIGHT...FAIR AND GENERALLY COOL CONDITIONS EXPECTED. A DRY
LOW/MID LEVEL COLUMN AND LACK OF ANY SYNOPTIC FORCING WILL KEEP RAIN
CHANCES NEAR ZERO INTO FRIDAY MORNING. SEEING AN INTERESTING THERMAL
STRUCTURE IN THE WAKE OF WEDNESDAYS COLD FRONT. MOST IMPRESSIVE CAA
HAS OCCURRED IN THE LOWER LEVELS AND IN FACT THE 850MB TEMPS WILL BE
WARMER FOR MOST OF US TODAY THAN THE READINGS AT 925-950MB. THIS IS
A THERMAL PROFILE WHICH IS MORE REPRESENTATIVE OF THE AIRMASS BEHIND
AN ARCTIC FRONT...EVEN THOUGH THIS ONE CERTAINLY WAS NOT. LESS
EFFICIENT MIXING AS THE RIDGE BUILDS IN AND THE COOLER TEMPS JUST
ABOVE THE SURFACE WILL KEEP OUR TEMPS BELOW NORMAL. AFTERNOON HIGHS
WILL STRUGGLE TO REACH THE LOWER 60S ALONG AND NORTH OF THE I-4
CORRIDOR AND MID 60S TO PERHAPS 70 FURTHER SOUTH. RIDGE AXIS WILL BE
ALIGNED DOWN THE PENINSULA TONIGHT SETTING UP DECENT RADIATIONAL
COOLING CONDITIONS. TEMPERATURES SHOULD DROP QUICKLY THIS
EVENING...SO BUNDLE UP IF HEADED OUT. BY MORNING...UPPER 30S TO
LOWER 40S WILL BE COMMON AWAY FROM THE COAST...AND EVEN SOME
SUB-FREEZING TEMPS FOR NORMALLY COLDER LOCATIONS FROM BROOKSVILLE
NORTHWARD. WILL BE WATCHING A SLOW INCREASE IN HIGH LEVEL MOISTURE
AFTER MIDNIGHT. AT THIS POINT...THIS MOISTURE IS NOT ANTICIPATED TO
HAVE MUCH IMPACT ON THE TEMP DROP...BUT WILL NEED TO BE WATCHED
CLOSELY IN CASE IT ARRIVES SOONER THAN CURRENTLY THOUGHT. HAVE
ISSUED A FREEZE WATCH FOR LEVY AND CITRUS COUNTIES FOR LATE
TONIGHT...AS THESE ZONES STAND THE BEST CHANCES AT ANY DURATION OF
SUB-FREEZING TEMPS. ELSEWHERE...WITH SMALL DEWPOINT DEPRESSION AND
LIGHT WINDS...HAVE ADDED PATCHY/AREAS OF FROST TO THE GRIDS FOR
LOCATIONS FORECAST TO REACH 36 DEGREES OR LOWER.
FRIDAY/FRIDAY NIGHT...FAIR AND DRY CONDITIONS EXPECTED FOR THE
DAYLIGHT HOURS. NOT QUITE AS MUCH SUNSHINE THOUGH AS HIGH LEVEL
CLOUDS WILL BE ON THE INCREASE. UPPER LEVEL TROUGH TO OUR WEST WILL
BE APPROACHING THE NORTHERN GULF COAST WITH WEAK CYCLOGENESIS
COMMENCING ALONG THE UPPER TX/LA COAST. A WARM FRONTAL FEATURE WILL
BE DEVELOPING EASTWARD FROM THIS SURFACE REFLECTION TO THE NE GULF.
LATE IN THE DAY / EVENING HOURS...LOW LEVEL UPGLIDE ALONG THE
290-300K SURFACES ASSOCIATED WITH THIS FRONT WILL QUICKLY MOISTEN
THE LOWER LEVELS. THIS UPGLIDE / WAA (WARM AIR ADVECTION) PATTERN
SHOULD BEGIN TO DEVELOP SHOWERS ACROSS THE COASTAL WATERS EARLY IN
THE EVENING...AND THEN TOWARD LAND LATE EVENING. NUMERICAL GUIDANCE
IS OFTEN TOO SLOW TO MOISTEN AND DEVELOP QPF DURING UPGLIDE EVENTS
AND HAVE BROUGHT IN SHOWER CHANCES A BIT EARLIER WITH THIS FORECAST
PACKAGE. BEST COVERAGE OF SHOWERS FRIDAY NIGHT IS LIKELY TO BE OVER
THE NORTHERN HALF OF THE AREA WHERE WAA WILL BE MAXIMIZED. SHOWALTER
INDICES OFF THE GFS/ECMWF ARE AROUND ZERO FRIDAY NIGHT...SUGGESTING
SOME THUNDER POTENTIAL. LOW TEMPERATURES FRIDAY NIGHT WILL LIKELY BE
IN THE LATE EVENING...AND THEN RISE AFTER MIDNIGHT IN RESPONSE TO
THE NORTHWARD TRANSLATION OF THE WARM FRONT.
SATURDAY...SURFACE LOW PRESSURE TRACKS FROM THE FL PANHANDLE TO OFF
THE GA/SC COASTLINE DURING THE DAY. TRAILING COLD FRONT WILL SWING
ACROSS THE FORECAST AREA DURING THE DAYLIGHT HOURS. BROAD SWATH OF
WEAK SYNOPTIC SUPPORT AHEAD OF THE UPPER TROUGH AND LOW LEVEL FOCUS
ALONG THE FRONT SHOULD SUPPORT A BAND OF SHOWERS AND STORMS TO
ACCOMPANY THE FRONT. BAND OF CONVECTION SHOULD BE MOST ORGANIZED
FROM THE TAMPA BAY / SARASOTA REGION NORTHWARD WHERE SYNOPTIC
FORCING WILL BE GREATEST. ALTHOUGH STILL EXPECT SHOWERS AND STORMS
FURTHER SOUTH AND EAST...THE BAND SHOULD BE THINNING OUT WITH LESS
FORCING AND AVAILABLE MOISTURE. A STRONGER THUNDERSTORM CAN NOT BE
RULED OUT ON SATURDAY...HOWEVER INSTABILITY AND WIND FIELDS SUGGEST
THE THREAT OF ORGANIZED SEVERE WEATHER IS LOW.
&&
.LONG TERM (SATURDAY NIGHT THROUGH NEXT WEDNESDAY)...
MODELS ARE IN GOOD AGREEMENT THROUGH TUESDAY SO FORECAST CONFIDENCE
THROUGH THEN IS HIGHER THAN NORMAL. AFTER THAT...THE GFS AND ECMWF
PART WAYS IN THE HANDLING OF A CUTOFF LOW OVER THE SOUTHWESTERN
STATES. THE GFS IS LESS CUTOFF AND THEREFORE MORE PROGRESSIVE...
BRINGING A POTENT UPPER-LEVEL TROUGH AND ASSOCIATED FRONTAL BOUNDARY
INTO THE REGION ON WEDNESDAY. THE ECMWF HAS MORE OF A SPLIT
FLOW...LEAVING THE CUTOFF LOW TO MEANDER UNTIL LATE NEXT WEEK.
EITHER SOLUTION IS POSSIBLE SINCE THE TROUGH THAT WILL BE PARENTING
THE CUT-OFF LOW WILL ONLY BE REACHING THE WEST COAST OF THE U.S. ON
FRIDAY. SINCE WE HAVE BEEN IN A FAIRLY PROGRESSIVE PATTERN FOR A
WHILE NOW...WILL INITIALLY SIDE WITH THE FASTER GFS. I WOULD NOT BE
SURPRISED IF WE NEED TO SLOW THE FRONT DOWN IN LATER FORECASTS.
AS FAR AS THE DETAILS GO...THE WEEKEND COLD FRONT WILL BE THROUGH
THE AREA SUNDAY NIGHT WITH COOLER AND DRIER AIR MOVING IN BEHIND IT.
EXPERIMENTAL ECMWF MOS GUIDANCE AND THE MEX HAVE POPS BELOW 15
PERCENT FOR OUR AREA SATURDAY NIGHT...SO REMOVED THE LINGERING
SHOWERS IN OUR SOUTHERN ZONES. AFTER THAT...IT STAYS DRY THROUGH
TUESDAY WITH JUST A SLIGHT CHANCE OF SHOWERS ENTERING OUR NORTHERN
ZONES ON WEDNESDAY.
WE WILL START OFF A BIT ON THE CHILLY SIDE BEHIND THE COLD FRONT ON
SUNDAY WITH HIGHS ONLY NEAR 60 NORTH...MID 60S AROUND TAMPA BAY AND
UPPER 60S SOUTH. THIS WILL BE FOLLOWED BY A COOL NIGHT WITH SOME 30S
OVER THE NATURE COAST SUNDAY NIGHT INTO EARLY MONDAY MORNING.
OTHERWISE WE ARE LOOKING FOR FAIRLY TYPICAL TEMPERATURES FOR LATE
DECEMBER AND EARLY JANUARY WITH HIGHS IN THE 60S AND 70S AND LOWS IN
THE 40S AND 50S.
&&
.AVIATION...
SOME STRATOCUMULUS CLOUDS WITH BASES BETWEEN 2000 AND 3000 FEET
CONTINUES RIGHT ALONG THE COAST. THIS COULD BRING OCCASIONAL MVFR
CEILINGS MAINLY TO PIE THROUGH THE MORNING HOURS TODAY.
OTHERWISE...VFR CONDITIONS EXPECTED.
&&
.MARINE...
LINGERING ADVISORY LEVEL CONDITIONS EARLY THIS MORNING WILL
GRADUALLY DIMINISH THROUGH THE DAY AS HIGH PRESSURE RIDGES DOWN INTO
THE EASTERN GULF OF MEXICO. WINDS AND SEAS WILL BUILD AGAIN LATER
FRIDAY INTO FRIDAY NIGHT AHEAD OF OUR NEXT COLD FRONT. THIS FRONT
WILL CROSS THE EASTERN GULF OF MEXICO DURING SATURDAY. WINDS WILL
SHIFT TO THE NORTHWEST AND NORTH BEHIND THIS FRONT AND ONCE AGAIN
INCREASE TO ADVISORY LEVELS FOR THE SECOND HALF OF THE UPCOMING
WEEKEND.
&&
.FIRE WEATHER...
SURFACE HIGH PRESSURE WILL KEEP CONDITIONS DRY THROUGH FRIDAY.
RELATIVE HUMIDITY VALUES WILL DROP INTO THE LOWER/MID 30S AWAY FROM
THE COAST THIS AFTERNOON. A FIRE DANGER STATEMENT HAS BEEN ISSUED
FOR POLK AND LEE COUNTIES WHERE THE COMBINATION OF LOW RELATIVE
HUMIDITY AND ERC VALUES ABOVE 30 ARE MET. A SLOW MOISTENING OF THE
LOW LEVELS WILL BEGIN FRIDAY...ALTHOUGH INLAND AREAS OF THE NATURE
COAST ZONES MAY STILL RELATIVE HUMIDITY DROP TOWARD 35 PERCENT.
SATURDAY WILL SEE RELATIVE HUMIDITY WELL ABOVE CRITICAL LEVELS ALONG
WITH A GOOD CHANCE FOR SHOWERS AND STORMS AHEAD OF A COLD FRONT.
DRIER AND COOLER WEATHER WILL RETURN TO THE REGION BY SUNDAY BEHIND
THIS FRONT.
&&
.PRELIMINARY POINT TEMPS/POPS...
TPA 62 44 70 63 / 0 0 10 50
FMY 68 47 76 65 / 0 0 10 20
GIF 64 39 73 58 / 0 0 0 40
SRQ 63 44 71 63 / 0 0 10 40
BKV 61 34 70 57 / 0 0 10 60
SPG 61 50 68 64 / 0 0 10 50
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...BEACH HAZARDS STATEMENT THROUGH THIS EVENING FOR CHARLOTTE-
HILLSBOROUGH-LEE-MANATEE-PINELLAS-SARASOTA.
HIGH SURF ADVISORY UNTIL 7 AM EST THIS MORNING FOR
CHARLOTTE-HILLSBOROUGH-LEE-MANATEE-PINELLAS-SARASOTA.
FREEZE WATCH FROM LATE TONIGHT THROUGH FRIDAY MORNING FOR
CITRUS-LEVY.
GULF WATERS...SMALL CRAFT ADVISORY UNTIL 11 AM EST THIS MORNING FOR
BONITA BEACH TO ENGLEWOOD OUT 20 TO 60 NM-ENGLEWOOD
TO TARPON SPRINGS OUT 20 TO 60 NM.
SMALL CRAFT ADVISORY UNTIL 7 AM EST THIS MORNING FOR
BONITA BEACH TO ENGLEWOOD OUT 20 NM-ENGLEWOOD TO
TARPON SPRINGS OUT 20 NM-TARPON SPRINGS TO SUWANNEE
RIVER OUT 20 TO 60 NM.
&&
$$
SYNOPSIS/SHORT TERM/MARINE/FIRE WX...MROCZKA
LONG TERM/AVIATION...JILLSON
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
935 PM CST FRI DEC 28 2012
.DISCUSSION...
918 PM CST
FOR EVENING UPDATE...
HAVE MADE ONLY MINOR NEAR-TERM TWEAKS TO EARLIER UPDATE FOR TRENDS
WITH FLURRIES/PATCHY FREEZING DRIZZLE WHICH CONTINUE TO AFFECT
PORTIONS OF NORTHERN IL AT MID-EVENING. HAVE ALSO BEEFED UP POPS
ALONG THE IL/IN LAKE MICHIGAN SHORE AREAS SATURDAY...WITH POTENTIAL
FOR LAKE-EFFECT SNOW SHOWERS.
LOW PRESSURE WAS OVER THE LOWER MISSISSIPPI VALLEY THIS EVENING...
WITH A WEAK INVERTED SURFACE TROUGH EXTENDING NORTH THROUGH IL/WI.
THIS TROUGH IS ASSOCIATED WITH RATHER COMPLEX MID/UPPER LEVEL TROUGH
ACROSS THE MIDWEST...WHICH WILL CONTINUE TO MOVE EAST ACROSS THE
REGION OVERNIGHT. 00Z RAOBS FROM DVN/ILX INDICATE THE NATURE OF OUR
FLURRY/FREEZING DRIZZLE ISSUE THIS EVENING...WITH SATURATED LOW
LEVELS UP TO ABOUT 800 MB...WITH COLDEST TEMPS ONLY ABOUT -8 C TO
-10 C WITHIN THAT MOIST LAYER. THIS WAS RESULTING IN MORE
SUPERCOOLED DROPLETS THAN ICE CRYSTALS...AND DRIZZLE/FREEZING
DRIZZLE AT THE SURFACE WITH OCCASIONAL FINE SNOW GRAINS/FLURRIES. AS
MENTIONED IN EARLIER UPDATE...MAIN UPPER TROUGH AXIS AND STRONGER
VORT OVER IA IS EXPECTED TO PROPAGATE EASTWARD ACROSS NORTHERN IL
AFTER MIDNIGHT...WITH GREATER POTENTIAL TO INTRODUCE ICE CRYSTALS
AND THUS A GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN
THE DRIZZLE EXPERIENCED THIS EVENING. HOWEVER...GUIDANCE IS
CONSISTENT IN WEAKENING THIS WAVE AS IT MOVES EAST AND DRYING UP
MODEL GENERATED QPF AS IT REACHES OUR CWA. THUS HAVE CUT BACK POPS A
BIT AND MENTIONED LIGHT SNOW/FLURRIES WITH NO REAL ACCUMULATION FOR
THE OVERNIGHT ACROSS THE AREA.
ON SATURDAY...INVERTED TROUGH/CONVERGENCE AXIS ENDS UP LINGERING
ALONG THE WESTERN SHORE OF LAKE MICHIGAN AS LOW LEVEL WINDS BACK TO
THE NORTH-NORTHWEST THROUGH AFTERNOON. LAKE-INDUCED THERMODYNAMIC
PROFILES IMPROVE THROUGH LATE SATURDAY...WITH SFC-850 DELTA T
INCREASING TO ABOUT 17 C...AND EQUILIBRIUM LEVELS INCREASING TO
NEARLY 10 KFT LATER IN THE DAY/EVENING. THIS SUPPORTS SCENARIO OF
LAKE EFFECT SNOW SHOWER DEVELOPMENT ALONG THE IL SHORE AND INTO
NORTHWEST INDIANA SATURDAY MORNING/AFTERNOON...WITH THE BAND
EVENTUALLY MOVING EAST OF THE IL SHORE AND AFFECTING MAINLY PORTER
COUNTY SATURDAY EVENING. WHILE DAYTIME TEMPS IN THE LOW/MID 30S
ESPECIALLY DOWNWIND OF THE LAKE ARE A LIMITING FACTOR...THE
POTENTIAL FOR SOME MINOR ACCUMULATION APPEARS TO EXIST ALONG THE IL
SHORE...WITH PERHAPS 2-4 INCHES POSSIBLE OVER NORTHERN/NORTHEASTERN
PORTER COUNTY WHERE THE BAND MAY BE MORE FOCUSED LATE IN THE
DAY/EARLY EVENING HOURS. THUS HAVE BUMPED POPS TO LIKELY IN THESE
AREAS AND INCREASED QPF/SNOW AMOUNTS A BIT. WINDS CONTINUE TO BACK
MORE NORTHWEST-WEST AFTER ABOUT 03Z...WHICH SHOULD SHIFT THE FOCUS
FOR LES EAST OF PORTER COUNTY BY LATE SATURDAY EVENING.
RATZER
//PREV DISCUSSION...
644 PM CST
FOR EARLY EVENING UPDATE...
HAVE ADDED A MENTION OF PATCHY FREEZING DRIZZLE TO FORECAST EARLY
THIS EVENING BASED ON CURRENT OBS/REPORT OF DZ/FZDZ ACROSS PARTS OF
NORTHERN IL.
AREA OF VERY LIGHT REFLECTIVITY...<10 DBZ...OVER NORTHERN IL PER
KLOT 88D DATA WAS PRODUCING LIGHT FREEZING DRIZZLE/FLURRIES PER
REGIONAL AWOS REPORTS AS OF 00Z. THIS APPEARS VERY REASONABLE
BASED ON FORECAST SOUNDINGS FROM 18Z NAM/23Z RAP WHICH DEPICT
SATURATED LOW LEVELS UP TO ABOUT 5000-6000 FT OR ABOUT 800
MB...WITH TEMPS ONLY -9/-10C. THIS SUGGESTS WHILE THERE MAY BE ICE
CRYSTALS PRESENT...SUPERCOOLED LIQUID DROPLETS ARE MORE PREVALENT
WHICH IS SUPPORTED BY THE SURFACE REPORTS OF FREEZING DRIZZLE. HAD
A REPORT FROM THE SOUTHEAST CORNER OF LASALLE COUNTY AROUND 6 PM
INDICATING FOG/DRIZZLE AT 30 DEGREES WITH SOME LIGHT ICING ON
OBJECTS. TEMPS GENERALLY RUNNING 30-32 F ACROSS THE AREA SO CANT
RULE OUT SOME TRACE AMOUNTS OF ICE THOUGH WOULD EXPECT MOST WELL-
TRAVELED AND TREATED ROADS WILL BE OK. SIDEWALKS...PARKING
LOTS...WINDSHIELDS OF PARKED CARS MAY SEE A LITTLE LIGHT GLAZING.
HERE AT THE WFO...VERY LIGHT DRIZZLE MORE LIKE A MIST OCCURRING
WITH NO REAL ACCUMULATION OR ICING. BASED ON THIS HAVE ISSUED AN
SPS HIGHLIGHTING THIS...BUT AT THIS TIME HAVE REFRAINED FROM A
WINTER WX ADVISORY.
STRONGER MID-LEVEL WAVE OVER CENTRAL/SOUTHWEST IA IS EXPECTED TO
APPROACH THE AREA LATER THIS EVENING/OVERNIGHT WITH A LITTLE MORE
MID-LEVEL MOISTURE WHICH SHOULD FAVOR MORE NUMEROUS ICE NUCLEI AND A
GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN FREEZING
DRIZZLE.
WITH MOIST LOW LEVELS AND LIGHT WINDS...AREAS OF FOG ALSO NOTED WITH
VISIBILITY GENERALLY 1-3 MILES. SAME REPORT FROM LASALLE COUNTY
INDICATED VIS AS LOW AS 1/2 MILE...THOUGH WITH CLOUD COVER AM NOT
EXPECTING WIDESPREAD VIS UNDER 1 MILE.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 03Z...
* PATCHY LIGHT SNOW OR FLURRIES WITH LITTLE TO NO ACCUMULATION.
* LIGHT FOG PERSISTING INTO SATURDAY MORNING.
* MVFR CIGS POSSIBLY LOWERING TO IFR FOR A PERIOD...THEN
IMPROVING TO MVFR AROUND DAYBREAK.
* WINDS LIGHT AND VARIABLE OVERNIGHT...BECOMING NORTHWESTERLY
AROUND DAYBREAK.
ED F
//DISCUSSION...UPDATED 00Z...
AREA OF CIGS AND VSBYS LOWERING TO IFR FROM RPJ TO DKB TO ARR TO
C09 TO VYS IN AREA OF WEAK GRADIENT FLOW AND HIGH LOW LEVEL
MOISTURE. AREA FORECAST SOUNDINGS SHOWING SATURATED LAYER
EXTENDING UP TO ABOUT 5500 FT WITH DRY LAYER ALOFT. WITH LOWEST
TEMP IN THE SATURATED LAYER AROUND -8 DEG C MAY SEE PATCHY
DRIZZLE MIXING IN WITH FLURRIES AS CYCLONIC FLOW TIGHTENS IN
ADVANCE OF AN UPPER LEVEL DISTURBANCE OVER IOWA AS OF OO UTC.
AS THIS UPPER LEVEL DISTURBANCE MOVES EAST INTO NRN ILLINOIS
OVERNIGHT EXPECT BRIEF DURATION LIGHT SNOW OR FLURRY EVENT TO
MOVE FROM WEST TO EAST ACROSS THE AREA. EXPECT LITTLE TO NO
ACCUMULATION WITH A FEW AREAS SEEING UP TO A HALF INCH. THE BEST
TIME PERIOD FOR ORD AND MDW TO SEE ANY ACCUMULATION SNOW WOULD
BE BETWEEN 2 AND 5 AM CST.
INCREASING SINKING AIR BEHIND THE DISTURBANCE WILL HELP END ANY
PRECIPITATION WHILE CIGS ONLY RAISE SLIGHTLY BACK TO ABOVE 1000 FT
BY DAYBREAK. WITH COLDER AIR WRAPPING IN BEHIND THE SYSTEM EXPECT
LAKE EFFECT SNOW TO REDEVELOP OFF LAKE MICHIGAN BUT PRIMARILY ONLY
IMPACT THE GYY TERMINAL SAT MORNING.
ED F
//ORD AND MDW CONFIDENCE...UPDATED 03Z...
* MEDIUM CONFIDENCE IN CIG AND VSBY TRENDS OVERNIGHT.
* LOW CONFIDENCE IN WHETHER AND HOW LONG CIGS DROP TO IFR AT ORD AND
MDW.
* HIGH CONFIDENCE IN LIGHT FOG PERSISTING TILL ABOUT MID MORNING SATURDAY.
* HIGH CONFIDENCE IN WIND FORECAST.
ED F
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
* SUNDAY...DRY/VFR.
* MONDAY...DRY. MVFR POSSIBLE.
* TUESDAY AND WEDNESDAY...DRY/VFR.
* WEDNESDAY NIGHT AND THURSDAY...SLIGHT CHANCE OF SNOW SHOWERS/MVFR.
ED F
&&
.MARINE...
200 PM CST
RELATIVELY LIGHTER WINDS IN PLACE ACROSS THE LAKE EARLY THIS
AFTERNOON AS A FAIRLY WEAK SURFACE PATTERN IS IN PLACE. THE
EXCEPTION IS FOR AREAS NEAR THE MIDDLE PORTIONS OF THE LAKE WHERE
A TIGHTER PRESSURE GRADIENT RESIDES...AND WHERE 10 TO 20 KT WINDS
ARE BEING OBSERVED. WIND DIRECTION REMAINS VARIABLE WITH NORTHERLY
WINDS BEING REPORTED ACROSS THE NORTHERN HALF OF THE LAKE AND
SOUTHERLY WINDS OVER THE SOUTHERN HALF OF THE LAKE. WINDS WILL BE
TURNING TO MORE OF A NORTHERLY DIRECTION TONIGHT AS A WEAK SURFACE
TROUGH SHIFTS EAST ACROSS THE REGION. EXPECT NORTH TO NORTHWEST
WINDS ON SATURDAY WITH AN INCREASE IN SPEEDS...WITH WINDS THEN
TURNING MORE WESTERLY AND DIMINISHING SOME AS HIGH PRESSURE TO THE
WEST SHIFTS EAST THROUGH THE CENTRAL GREAT LAKES SATURDAY NIGHT.
SOUTHWESTERLY WINDS WILL THEN PICK UP SUNDAY THROUGH SUNDAY NIGHT
AS THE NEXT SYSTEM APPROACHES FROM THE WEST.
RODRIGUEZ
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
919 PM CST FRI DEC 28 2012
.DISCUSSION...
918 PM CST
FOR EVENING UPDATE...
HAVE MADE ONLY MINOR NEAR-TERM TWEAKS TO EARLIER UPDATE FOR TRENDS
WITH FLURRIES/PATCHY FREEZING DRIZZLE WHICH CONTINUE TO AFFECT
PORTIONS OF NORTHERN IL AT MID-EVENING. HAVE ALSO BEEFED UP POPS
ALONG THE IL/IN LAKE MICHIGAN SHORE AREAS SATURDAY...WITH POTENTIAL
FOR LAKE-EFFECT SNOW SHOWERS.
LOW PRESSURE WAS OVER THE LOWER MISSISSIPPI VALLEY THIS EVENING...
WITH A WEAK INVERTED SURFACE TROUGH EXTENDING NORTH THROUGH IL/WI.
THIS TROUGH IS ASSOCIATED WITH RATHER COMPLEX MID/UPPER LEVEL TROUGH
ACROSS THE MIDWEST...WHICH WILL CONTINUE TO MOVE EAST ACROSS THE
REGION OVERNIGHT. 00Z RAOBS FROM DVN/ILX INDICATE THE NATURE OF OUR
FLURRY/FREEZING DRIZZLE ISSUE THIS EVENING...WITH SATURATED LOW
LEVELS UP TO ABOUT 800 MB...WITH COLDEST TEMPS ONLY ABOUT -8 C TO
-10 C WITHIN THAT MOIST LAYER. THIS WAS RESULTING IN MORE
SUPERCOOLED DROPLETS THAN ICE CRYSTALS...AND DRIZZLE/FREEZING
DRIZZLE AT THE SURFACE WITH OCCASIONAL FINE SNOW GRAINS/FLURRIES. AS
MENTIONED IN EARLIER UPDATE...MAIN UPPER TROUGH AXIS AND STRONGER
VORT OVER IA IS EXPECTED TO PROPAGATE EASTWARD ACROSS NORTHERN IL
AFTER MIDNIGHT...WITH GREATER POTENTIAL TO INTRODUCE ICE CRYSTALS
AND THUS A GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN
THE DRIZZLE EXPERIENCED THIS EVENING. HOWEVER...GUIDANCE IS
CONSISTENT IN WEAKENING THIS WAVE AS IT MOVES EAST AND DRYING UP
MODEL GENERATED QPF AS IT REACHES OUR CWA. THUS HAVE CUT BACK POPS A
BIT AND MENTIONED LIGHT SNOW/FLURRIES WITH NO REAL ACCUMULATION FOR
THE OVERNIGHT ACROSS THE AREA.
ON SATURDAY...INVERTED TROUGH/CONVERGENCE AXIS ENDS UP LINGERING
ALONG THE WESTERN SHORE OF LAKE MICHIGAN AS LOW LEVEL WINDS BACK TO
THE NORTH-NORTHWEST THROUGH AFTERNOON. LAKE-INDUCED THERMODYNAMIC
PROFILES IMPROVE THROUGH LATE SATURDAY...WITH SFC-850 DELTA T
INCREASING TO ABOUT 17 C...AND EQUILIBRIUM LEVELS INCREASING TO
NEARLY 10 KFT LATER IN THE DAY/EVENING. THIS SUPPORTS SCENARIO OF
LAKE EFFECT SNOW SHOWER DEVELOPMENT ALONG THE IL SHORE AND INTO
NORTHWEST INDIANA SATURDAY MORNING/AFTERNOON...WITH THE BAND
EVENTUALLY MOVING EAST OF THE IL SHORE AND AFFECTING MAINLY PORTER
COUNTY SATURDAY EVENING. WHILE DAYTIME TEMPS IN THE LOW/MID 30S
ESPECIALLY DOWNWIND OF THE LAKE ARE A LIMITING FACTOR...THE
POTENTIAL FOR SOME MINOR ACCUMULATION APPEARS TO EXIST ALONG THE IL
SHORE...WITH PERHAPS 2-4 INCHES POSSIBLE OVER NORTHERN/NORTHEASTERN
PORTER COUNTY WHERE THE BAND MAY BE MORE FOCUSED LATE IN THE
DAY/EARLY EVENING HOURS. THUS HAVE BUMPED POPS TO LIKELY IN THESE
AREAS AND INCREASED QPF/SNOW AMOUNTS A BIT. WINDS CONTINUE TO BACK
MORE NORTHWEST-WEST AFTER ABOUT 03Z...WHICH SHOULD SHIFT THE FOCUS
FOR LES EAST OF PORTER COUNTY BY LATE SATURDAY EVENING.
RATZER
&&
.PREV DISCUSSION...
644 PM CST
FOR EARLY EVENING UPDATE...
HAVE ADDED A MENTION OF PATCHY FREEZING DRIZZLE TO FORECAST EARLY
THIS EVENING BASED ON CURRENT OBS/REPORT OF DZ/FZDZ ACROSS PARTS OF
NORTHERN IL.
AREA OF VERY LIGHT REFLECTIVITY...<10 DBZ...OVER NORTHERN IL PER
KLOT 88D DATA WAS PRODUCING LIGHT FREEZING DRIZZLE/FLURRIES PER
REGIONAL AWOS REPORTS AS OF 00Z. THIS APPEARS VERY REASONABLE
BASED ON FORECAST SOUNDINGS FROM 18Z NAM/23Z RAP WHICH DEPICT
SATURATED LOW LEVELS UP TO ABOUT 5000-6000 FT OR ABOUT 800
MB...WITH TEMPS ONLY -9/-10C. THIS SUGGESTS WHILE THERE MAY BE ICE
CRYSTALS PRESENT...SUPERCOOLED LIQUID DROPLETS ARE MORE PREVALENT
WHICH IS SUPPORTED BY THE SURFACE REPORTS OF FREEZING DRIZZLE. HAD
A REPORT FROM THE SOUTHEAST CORNER OF LASALLE COUNTY AROUND 6 PM
INDICATING FOG/DRIZZLE AT 30 DEGREES WITH SOME LIGHT ICING ON
OBJECTS. TEMPS GENERALLY RUNNING 30-32 F ACROSS THE AREA SO CANT
RULE OUT SOME TRACE AMOUNTS OF ICE THOUGH WOULD EXPECT MOST WELL-
TRAVELED AND TREATED ROADS WILL BE OK. SIDEWALKS...PARKING
LOTS...WINDSHIELDS OF PARKED CARS MAY SEE A LITTLE LIGHT GLAZING.
HERE AT THE WFO...VERY LIGHT DRIZZLE MORE LIKE A MIST OCCURRING
WITH NO REAL ACCUMULATION OR ICING. BASED ON THIS HAVE ISSUED AN
SPS HIGHLIGHTING THIS...BUT AT THIS TIME HAVE REFRAINED FROM A
WINTER WX ADVISORY.
STRONGER MID-LEVEL WAVE OVER CENTRAL/SOUTHWEST IA IS EXPECTED TO
APPROACH THE AREA LATER THIS EVENING/OVERNIGHT WITH A LITTLE MORE
MID-LEVEL MOISTURE WHICH SHOULD FAVOR MORE NUMEROUS ICE NUCLEI AND A
GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN FREEZING
DRIZZLE.
WITH MOIST LOW LEVELS AND LIGHT WINDS...AREAS OF FOG ALSO NOTED WITH
VISIBILITY GENERALLY 1-3 MILES. SAME REPORT FROM LASALLE COUNTY
INDICATED VIS AS LOW AS 1/2 MILE...THOUGH WITH CLOUD COVER AM NOT
EXPECTING WIDESPREAD VIS UNDER 1 MILE.
RATZER
&&
.AVIATION...
621 PM CST
//ORD AND MDW CONCERNS...UPDATED 00Z...
* AREA OF LOWERING CIGS AND VSBYS TO IFR CONDITIONS WEST OF
CHICAGO EXPANDING SLOWLY. PATCHY DRIZZLE WITHIN THIS AREA.
* MVFR CIGS EXPECTED INTO THIS EVENING...LOWERING TO IFR
OVERNIGHT...THEN IMPROVING TO MVFR TOMORROW MORNING.
* A PERIOD OF -SN OR FLURRIES OVERNIGHT...PERIOD OF IFR VIS
POSSIBLE. PATCHY DRIZZLE POSSIBLE THIS EVENING.
* LIGHT S-SE WINDS AROUND 5-7 KTS BECOMING LGT/VRBL OVERNIGHT.
ED F
//DISCUSSION...UPDATED 00Z...
AREA OF CIGS AND VSBYS LOWERING TO IFR FROM RPJ TO DKB TO ARR TO
C09 TO VYS IN AREA OF WEAK GRADIENT FLOW AND HIGH LOW LEVEL
MOISTURE. AREA FORECAST SOUNDINGS SHOWING SATURATED LAYER
EXTENDING UP TO ABOUT 5500 FT WITH DRY LAYER ALOFT. WITH LOWEST
TEMP IN THE SATURATED LAYER AROUND -8 DEG C MAY SEE PATCHY
DRIZZLE MIXING IN WITH FLURRIES AS CYCLONIC FLOW TIGHTENS IN
ADVANCE OF AN UPPER LEVEL DISTURBANCE OVER IOWA AS OF OO UTC.
AS THIS UPPER LEVEL DISTURBANCE MOVES EAST INTO NRN ILLINOIS
OVERNIGHT EXPECT BRIEF DURATION LIGHT SNOW OR FLURRY EVENT TO
MOVE FROM WEST TO EAST ACROSS THE AREA. EXPECT LITTLE TO NO
ACCUMULATION WITH A FEW AREAS SEEING UP TO A HALF INCH. THE BEST
TIME PERIOD FOR ORD AND MDW TO SEE ANY ACCUMULATION SNOW WOULD
BE BETWEEN 2 AND 5 AM CST.
INCREASING SINKING AIR BEHIND THE DISTURBANCE WILL HELP END ANY
PRECIPITATION WHILE CIGS ONLY RAISE SLIGHTLY BACK TO ABOVE 1000 FT
BY DAYBREAK. WITH COLDER AIR WRAPPING IN BEHIND THE SYSTEM EXPECT
LAKE EFFECT SNOW TO REDEVELOP OFF LAKE MICHIGAN BUT PRIMARILY ONLY
IMPACT THE GYY TERMINAL SAT MORNING.
ED F
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* MEDIUM CONFIDENCE IN THE CIGS/VIS TRENDS INTO THIS EVENING.
* LOW CONFIDENCE IN TIMING OF ONSET OF IFR CONDITIONS TONIGHT
AND IMPROVEMENT BACK TO MVFR SATURDAY MORNING.
* LOW CONFIDENCE IN TIMING AND DURATION OF REDUCED VIS WITH -SN TONIGHT.
* HIGH CONFIDENCE IN WIND FORECAST.
ED F
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
* SUNDAY...DRY/VFR.
* MONDAY...DRY. MVFR POSSIBLE.
* TUESDAY AND WEDNESDAY...DRY/VFR.
* WEDNESDAY NIGHT AND THURSDAY...SLIGHT CHANCE OF SNOW SHOWERS/MVFR.
ED F
&&
.MARINE...
200 PM CST
RELATIVELY LIGHTER WINDS IN PLACE ACROSS THE LAKE EARLY THIS
AFTERNOON AS A FAIRLY WEAK SURFACE PATTERN IS IN PLACE. THE
EXCEPTION IS FOR AREAS NEAR THE MIDDLE PORTIONS OF THE LAKE WHERE
A TIGHTER PRESSURE GRADIENT RESIDES...AND WHERE 10 TO 20 KT WINDS
ARE BEING OBSERVED. WIND DIRECTION REMAINS VARIABLE WITH NORTHERLY
WINDS BEING REPORTED ACROSS THE NORTHERN HALF OF THE LAKE AND
SOUTHERLY WINDS OVER THE SOUTHERN HALF OF THE LAKE. WINDS WILL BE
TURNING TO MORE OF A NORTHERLY DIRECTION TONIGHT AS A WEAK SURFACE
TROUGH SHIFTS EAST ACROSS THE REGION. EXPECT NORTH TO NORTHWEST
WINDS ON SATURDAY WITH AN INCREASE IN SPEEDS...WITH WINDS THEN
TURNING MORE WESTERLY AND DIMINISHING SOME AS HIGH PRESSURE TO THE
WEST SHIFTS EAST THROUGH THE CENTRAL GREAT LAKES SATURDAY NIGHT.
SOUTHWESTERLY WINDS WILL THEN PICK UP SUNDAY THROUGH SUNDAY NIGHT
AS THE NEXT SYSTEM APPROACHES FROM THE WEST.
RODRIGUEZ
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
644 PM CST FRI DEC 28 2012
.DISCUSSION...
644 PM CST
FOR EARLY EVENING UPDATE...
HAVE ADDED A MENTION OF PATCHY FREEZING DRIZZLE TO FORECAST EARLY
THIS EVENING BASED ON CURRENT OBS/REPORT OF DZ/FZDZ ACROSS PARTS OF
NORTHERN IL.
AREA OF VERY LIGHT REFLECTIVITY...<10 DBZ...OVER NORTHERN IL PER
KLOT 88D DATA WAS PRODUCING LIGHT FREEZING DRIZZLE/FLURRIES PER
REGIONAL AWOS REPORTS AS OF 00Z. THIS APPEARS VERY REASONABLE
BASED ON FORECAST SOUNDINGS FROM 18Z NAM/23Z RAP WHICH DEPICT
SATURATED LOW LEVELS UP TO ABOUT 5000-6000 FT OR ABOUT 800
MB...WITH TEMPS ONLY -9/-10C. THIS SUGGESTS WHILE THERE MAY BE ICE
CRYSTALS PRESENT...SUPERCOOLED LIQUID DROPLETS ARE MORE PREVALENT
WHICH IS SUPPORTED BY THE SURFACE REPORTS OF FREEZING DRIZZLE. HAD
A REPORT FROM THE SOUTHEAST CORNER OF LASALLE COUNTY AROUND 6 PM
INDICATING FOG/DRIZZLE AT 30 DEGREES WITH SOME LIGHT ICING ON
OBJECTS. TEMPS GENERALLY RUNNING 30-32 F ACROSS THE AREA SO CANT
RULE OUT SOME TRACE AMOUNTS OF ICE THOUGH WOULD EXPECT MOST WELL-
TRAVELED AND TREATED ROADS WILL BE OK. SIDEWALKS...PARKING
LOTS...WINDSHIELDS OF PARKED CARS MAY SEE A LITTLE LIGHT GLAZING.
HERE AT THE WFO...VERY LIGHT DRIZZLE MORE LIKE A MIST OCCURRING
WITH NO REAL ACCUMULATION OR ICING. BASED ON THIS HAVE ISSUED AN
SPS HIGHLIGHTING THIS...BUT AT THIS TIME HAVE REFRAINED FROM A
WINTER WX ADVISORY.
STRONGER MID-LEVEL WAVE OVER CENTRAL/SOUTHWEST IA IS EXPECTED TO
APPROACH THE AREA LATER THIS EVENING/OVERNIGHT WITH A LITTLE MORE
MID-LEVEL MOISTURE WHICH SHOULD FAVOR MORE NUMEROUS ICE NUCLEI AND A
GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN FREEZING
DRIZZLE.
WITH MOIST LOW LEVELS AND LIGHT WINDS...AREAS OF FOG ALSO NOTED WITH
VISIBILITY GENERALLY 1-3 MILES. SAME REPORT FROM LASALLE COUNTY
INDICATED VIS AS LOW AS 1/2 MILE...THOUGH WITH CLOUD COVER AM NOT
EXPECTING WIDESPREAD VIS UNDER 1 MILE.
RATZER
&&
.PREV DISCUSSION...
318 PM CST
SYNOPSIS...FORECAST LOOKS RELATIVELY QUIET WITH SYSTEMS PASSING TO
THE NORTH AND SOUTH OF THE CWA. LAKE EFFECT SNOW IS POSSIBLE
TONIGHT THROUGH SATURDAY EVENING WITH LITTLE TO NO ACCUMULATION
EXPECTED AT THIS TIME. THE NEXT CHANCE OF SNOW FOR AREAS ALONG AND
SOUTH OF I-80 ARRIVES EARLY NEXT WEEK...WITH ANOTHER CHANCE OF LAKE
EFFECT SNOW MID TO LATE NEXT WEEK.
REST OF TODAY AND TONIGHT...
WEAK LOW PRESSURE OVER NORTHERN MISSOURI/SOUTHERN IOWA WILL DRIFT
EAST WHILE DEEPER LOW PRESSURE OVER LOUISIANA ALSO MOVES EAST. THE
UPPER LEVEL DISTURBANCE FROM THIS MORNING REMAINS OVER NORTHERN IL
THROUGH CENTRAL MICHIGAN AND THE STRONGER REFLECTIVITIES ON RADAR
ARE NORTH OF THE DISTURBANCE. LIGHT SNOW SHOWERS OVER IOWA WILL
DRIFT EAST WITH THE LOW THAT IS PROGGED TO TRAVEL ACROSS THE WI/IL
STATE LINE...THEREFORE PUT THE BEST CHANCE FOR LIGHT SNOW ALONG THE
IL/WI BORDER. OCCASIONAL FLURRIES ARE POSSIBLE ELSEWHERE. IN FACT
MAY HAVE GONE A BIT ON THE HIGH END WITH CHANCE POPS FOR TONIGHT AND
TOMORROW SINCE THE SYSTEM LOOKS VERY WEAK. A POSITIVELY TILTED
UPPER LEVEL TROUGH WILL NOT HELP THE SYSTEM DEEPEN AND THE JET IS
TO OUR SOUTH FROM TEXAS THROUGH VIRGINIA SUPPORTING THE LOW OVER
LOUISIANA. CONFIDENCE IS MEDIUM IN REGARDS TO WHERE AND IF THE
LIGHT SNOW DEVELOPS...BUT HIGH FOR OCCASIONAL FLURRIES ELSEWHERE.
SNOW TOTALS TONIGHT WILL BE UP TO A FEW TENTHS ALONG THE IL/WI
BORDER WITH LITTLE TO NO ACCUMULATION ELSEWHERE.
ONLY MADE MINOR ADJUSTMENTS TO TEMPS TONIGHT AS THICK CLOUD COVER
AND GENERALLY LITTLE TO NO SNOW COVER WILL LIMIT COOLING TONIGHT.
SATURDAY THROUGH SUNDAY...
THE SOUTHERN LOW INTENSIFIES TONIGHT AND MOVES INTO WEST VIRGINIA BY
TOMORROW MORNING. PRECIP FROM THIS SYSTEM MAY CLIP BENTON COUNTY
BUT THINKING MAJORITY OF PRECIP WILL REMAIN SOUTH AND EAST OF THE
CWA. AN UPPER LEVEL VORTICITY STREAMER WRAPS AROUND THE BACKSIDE OF
THE UPPER LEVEL RIDGE AND STRONG CYCLONIC VORTICITY ADVECTION PUSHES
IT THROUGH THE CWA TOMORROW. THE FORCING FROM THE CVA AND ADDED
MOISTURE FROM THE LOW PASSING TO THE SOUTH WILL RESULT IN OCCASIONAL
FLURRIES ACROSS THE CWA. NO SIGNIFICANT ACCUMULATION IS EXPECTED
WITH THE FLURRIES.
THE ATTENTION THEN TURNS TO LAKE EFFECT SNOW. WINDS TURN NORTHEAST
TO NORTH OFF OF THE LAKE TOMORROW WITH LIGHT SNOW SHOWERS POSSIBLE
FROM MCHENRY THROUGH NE KANKAKEE AND NORTHERN NEWTON AND JASPER
COUNTIES. THE EXTENT OF THE LAKE EFFECT WILL DEPEND ON HOW STRONG
THE FLOW IS. MODERATE SHOWERS ARE POSSIBLE CLOSER TO THE LAKE.
WINDS TURN MORE NORTHWEST BY TOMORROW AFTERNOON SO THINKING THE
LAKE EFFECT WILL TRANSITION TOWARD NORTHWEST INDIANA. DUE TO
UNCERTAINTY WITH FORCING AND LOCATION LEFT POPS AT CHANCE FOR NOW.
HOWEVER AS MENTIONED BEFORE AREAS THAT DO NOT SEE LAKE EFFECT SNOW
WILL MORE THAN LIKELY SEE ON AND OFF FLURRIES DURING THE DAY DUE
TO THE TROUGH MOVING OVERHEAD. WINDS TURN FAR ENOUGH NORTHWEST
THAT THE SNOW SHOWERS TRANSITION TOWARD MICHIGAN AND EAST OF
PORTER COUNTY SATURDAY EVENING.
ALL IN ALL THINKING AROUND A HALF OF AN INCH IS POSSIBLE FOR AREAS
NEAR THE LAKE...WITH THE TOTAL DROPPING OFF DRASTICALLY THE FARTHER
YOU GET FROM THE LAKE. OF COURSE IF AN INTENSE LAKE EFFECT BAND
SETS UP AND REMAINS OVER A PARTICULAR AREA FOR AN EXTENDED PERIOD OF
TIME...LOCALLY HIGHER AMOUNTS ARE POSSIBLE. LITTLE TO NO
ACCUMULATION IS EXPECTED WITH THE FLURRIES. MEDIUM-HIGH CONFIDENCE
IN LAKE EFFECT OCCURRING....MEDIUM CONFIDENCE IN WHERE...AND MEDIUM
CONFIDENCE IN SNOWFALL TOTALS. HIGH CONFIDENCE IN FLURRIES OUTSIDE
OF LAKE EFFECT SNOW.
AN UPPER LEVEL RIDGE MOVES OVER THE REGION SUNDAY WITH A BROAD AREA
OF HIGH PRESSURE MOVING IN EARLY SUNDAY MORNING.
WENT ON THE HIGH SIDE OF GUIDANCE FOR TEMPS YET AGAIN WITH TEMPS
AROUND FREEZING OVER THE WEEKEND. SATURDAY NIGHT LOOKS ESPECIALLY
CHILLY WITH CLOUDS CLEARING OUT. MAX TEMPS AT OR AROUND FREEZING
ON SUNDAY BUT SOUTHEAST WINDS AND WARM AIR ADVECTION WILL LEAD TO
SLIGHTLY WARMER TEMPS SUNDAY NIGHT.
EXTENDED...MONDAY THROUGH FRIDAY...
A BROAD TROUGH SETS UP OVER THE WESTERN TWO THIRDS OF THE US THROUGH
THE EXTENDED WITH THE UPPER LEVEL JET OVER THE CWA EARLY NEXT WEEK.
LOW PRESSURE PASSES TO THE NORTH SUNDAY NIGHT THROUGH MONDAY WITH A
STRONGER LOW TO OUR SOUTH. THE LATEST MODEL RUNS SUGGEST THE LOW
MAY BE FURTHER NORTH AND IMPACT THE CWA...BUT FOR NOW WENT WITH THE
ALLBLEND SOLUTION THAT KEEPS SNOW ALONG AND SOUTH OF I-80 MONDAY.
ANOTHER LOW PRESSURE SYSTEM PASSES TO THE NORTH MID WEEK AS THE
UPPER LEVEL TROUGH SWINGS THROUGH THE REGION WITH ANOTHER ROUND OF
LAKE EFFECT SNOW POSSIBLE. WINDS TURN NORTH TO NORTHWEST LATE NEXT
WEEK WITH THE BEST CHANCE OF LAKE EFFECT SNOW OVER NORTHWEST INDIANA
RIGHT NOW.
WENT WITH TEMPS A BIT HIGHER THAN ALLBLEND AGAIN THROUGH THE
EXTENDED. THE GENERAL TREND IS MAX TEMPS AROUND FREEZING THROUGH THE
EXTENDED. WILL MENTION THAT TEMPS COULD BE WARMER IF THE GROUND
REMAINS SNOW-FREE. CLOUD COVER IS PLENTIFUL IN THE EXTENDED WITH
LOW TEMPS AROUND NORMAL.
JEE
&&
.AVIATION...
621 PM CST
//ORD AND MDW CONCERNS...UPDATED 00Z...
* AREA OF LOWERING CIGS AND VSBYS TO IFR CONDITIONS WEST OF
CHICAGO EXPANDING SLOWLY. PATCHY DRIZZLE WITHIN THIS AREA.
* MVFR CIGS EXPECTED INTO THIS EVENING...LOWERING TO IFR
OVERNIGHT...THEN IMPROVING TO MVFR TOMORROW MORNING.
* A PERIOD OF -SN OR FLURRIES OVERNIGHT...PERIOD OF IFR VIS
POSSIBLE. PATCHY DRIZZLE POSSIBLE THIS EVENING.
* LIGHT S-SE WINDS AROUND 5-7 KTS BECOMING LGT/VRBL OVERNIGHT.
ED F
//DISCUSSION...UPDATED 00Z...
AREA OF CIGS AND VSBYS LOWERING TO IFR FROM RPJ TO DKB TO ARR TO
C09 TO VYS IN AREA OF WEAK GRADIENT FLOW AND HIGH LOW LEVEL
MOISTURE. AREA FORECAST SOUNDINGS SHOWING SATURATED LAYER
EXTENDING UP TO ABOUT 5500 FT WITH DRY LAYER ALOFT. WITH LOWEST
TEMP IN THE SATURATED LAYER AROUND -8 DEG C MAY SEE PATCHY
DRIZZLE MIXING IN WITH FLURRIES AS CYCLONIC FLOW TIGHTENS IN
ADVANCE OF AN UPPER LEVEL DISTURBANCE OVER IOWA AS OF OO UTC.
AS THIS UPPER LEVEL DISTURBANCE MOVES EAST INTO NRN ILLINOIS
OVERNIGHT EXPECT BRIEF DURATION LIGHT SNOW OR FLURRY EVENT TO
MOVE FROM WEST TO EAST ACROSS THE AREA. EXPECT LITTLE TO NO
ACCUMULATION WITH A FEW AREAS SEEING UP TO A HALF INCH. THE BEST
TIME PERIOD FOR ORD AND MDW TO SEE ANY ACCUMULATION SNOW WOULD
BE BETWEEN 2 AND 5 AM CST.
INCREASING SINKING AIR BEHIND THE DISTURBANCE WILL HELP END ANY
PRECIPITATION WHILE CIGS ONLY RAISE SLIGHTLY BACK TO ABOVE 1000 FT
BY DAYBREAK. WITH COLDER AIR WRAPPING IN BEHIND THE SYSTEM EXPECT
LAKE EFFECT SNOW TO REDEVELOP OFF LAKE MICHIGAN BUT PRIMARILY ONLY
IMPACT THE GYY TERMINAL SAT MORNING.
ED F
//ORD AND MDW CONFIDENCE...UPDATED 00Z...
* MEDIUM CONFIDENCE IN THE CIGS/VIS TRENDS INTO THIS EVENING.
* LOW CONFIDENCE IN TIMING OF ONSET OF IFR CONDITIONS TONIGHT
AND IMPROVEMENT BACK TO MVFR SATURDAY MORNING.
* LOW CONFIDENCE IN TIMING AND DURATION OF REDUCED VIS WITH -SN TONIGHT.
* HIGH CONFIDENCE IN WIND FORECAST.
ED F
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
* SUNDAY...DRY/VFR.
* MONDAY...DRY. MVFR POSSIBLE.
* TUESDAY AND WEDNESDAY...DRY/VFR.
* WEDNESDAY NIGHT AND THURSDAY...SLIGHT CHANCE OF SNOW SHOWERS/MVFR.
ED F
&&
.MARINE...
200 PM CST
RELATIVELY LIGHTER WINDS IN PLACE ACROSS THE LAKE EARLY THIS
AFTERNOON AS A FAIRLY WEAK SURFACE PATTERN IS IN PLACE. THE
EXCEPTION IS FOR AREAS NEAR THE MIDDLE PORTIONS OF THE LAKE WHERE
A TIGHTER PRESSURE GRADIENT RESIDES...AND WHERE 10 TO 20 KT WINDS
ARE BEING OBSERVED. WIND DIRECTION REMAINS VARIABLE WITH NORTHERLY
WINDS BEING REPORTED ACROSS THE NORTHERN HALF OF THE LAKE AND
SOUTHERLY WINDS OVER THE SOUTHERN HALF OF THE LAKE. WINDS WILL BE
TURNING TO MORE OF A NORTHERLY DIRECTION TONIGHT AS A WEAK SURFACE
TROUGH SHIFTS EAST ACROSS THE REGION. EXPECT NORTH TO NORTHWEST
WINDS ON SATURDAY WITH AN INCREASE IN SPEEDS...WITH WINDS THEN
TURNING MORE WESTERLY AND DIMINISHING SOME AS HIGH PRESSURE TO THE
WEST SHIFTS EAST THROUGH THE CENTRAL GREAT LAKES SATURDAY NIGHT.
SOUTHWESTERLY WINDS WILL THEN PICK UP SUNDAY THROUGH SUNDAY NIGHT
AS THE NEXT SYSTEM APPROACHES FROM THE WEST.
RODRIGUEZ
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
NWS DULUTH MN
1113 AM CST THU DEC 27 2012
.UPDATE...
GOING FORECAST WAS PRETTY GOOD WITH NAILING THE SNOW BANDS STREAMING
ONTO THE NORTH SHORE. WITH REPORT OF 4.5 INCHES OF SNOW AT WOLF
RIDGE ENVIRONMENTAL LEARNING CENTER SINCE LAST NIGHT DECIDED TO
ISSUE ADVISORY. ESPECIALY SINCE THE SNOW WILL FALL OFF AND ON
THROUGH THIS AFTERNOON AND TONIGHT. THE LATEST 15Z RAP MODEL SHOWS
A BIT OF A SLOWDOWN THIS AFTERNOON THEN MORE SNOW TONIGHT...IN THE
SAME AREAS...FROM TWO HARBORS THORUGH LITTLE MARAIS. GREATEST
AMUNTS WILL BE IN THE HIGHER TERRAIN INLAND FROM THE LAKE.
&&
.PREV DISCUSSION... /ISSUED 521 AM CST THU DEC 27 2012/
AVIATION.../12Z TAF ISSUANCE/
VFR CONDITIONS ARE MOST LIKELY ACROSS NE MINNESOTA AND NW
WISCONSIN THIS MORNING. HOWEVER...MVFR CIGS WILL BRIEFLY AFFECT
KHYR THIS MORNING...AND COULD ALSO AFFECT KDLH. EXPECT THE BKN/OVC
HIGH CLOUDS MOVING INTO THE REGION FROM THE W AND SW TO LOWER INTO
THIS AFTERNOON AND EVENING. THIS WILL BEGIN TO RESULT IN MVFR
CIGS FOR THE REGION LATE THIS AFTERNOON AND TONIGHT. THERE COULD
BE LIGHT SNOW TONIGHT THAT COULD RESULT IN REDUCED VISIBILITY. IFR
VSBYS ARE NOT OUT OF THE QUESTION WITH THE SNOW...BUT VSBY WILL
PROBABLY NOT GET MUCH LOWER THAN MVFR. THE WINDS WILL BE LIGHT AND
VARIABLE THROUGH TONIGHT.
PREV DISCUSSION... /ISSUED 403 AM CST THU DEC 27 2012/
SHORT TERM...TODAY THROUGH FRIDAY.
MAIN FOCUS IN SHORT RANGE ON PERIODIC MESO-LOW
DEVELOPMENT...PRODUCING LOCALIZED SNOWFALL...THAT WILL TRACK OVER
THE WATERS OF WRN LAKE SUPERIOR...OCCASIONALLY MAKING LANDFALL.
GENERALLY HAVE BROADBRUSH CHC/LIKELY POPS FOR AREAS ADJACENT TO
LAKE SUPERIOR THROUGH FRIDAY TO ACCOUNT FOR THESE FEATURES.
CURRENT RADAR IMAGERY AND MARINE OBSERVATIONS ARE SHOWING A WELL
DEFINED LOW CURRENTLY SITUATED BETWEEN SILVER BAY AND THE WESTERN
APOSTLE ISLANDS. THE LATEST HIGH- RES DLHWRF/HRRR/RAW ARE
INITIALIZING WELL WITH THE PLACEMENT OF THIS MESO-LOW...ALTHOUGH
THESE VERY SMALL SCALE PHENOMENON ARE EXTREMELY DIFFICULT FOR
EVEN HIGH RES MODELS TO CAPTURE. MODELS ARE SUGGESTING THE MESO-
LOW TRANSLATES EAST THROUGH THE REMAINDER OF THE NIGHT...CENTERING
OVER THE APOSTLE ISLANDS/BAYFIELD PENINSULA BY DAY BREAK. HAVE
INCREASED POPS/SNOW AMOUNTS ACROSS THIS AREA REGION WITH
HIGHER CONFIDENCE IN VERY NEAR TERM. THERE IS ALSO AGREEMENT THAT
VERY LOCALIZED SNOW ACCUMULATIONS OF UP TO 3 INCHES WILL BE FOUND
UNDER THE SNOW BANDS NEAR THE LOW TODAY. AT THIS TIME...THE
GREATEST CHANCE TO SEE A FEW INCHES OF ACCUMULATING SNOW TODAY
WILL BE FROM DEVILS ISLAND...TO SAND BAY...TO PORT WING.
HOWEVER...THIS IS HIGHLY DEPENDENT ON THE SPEED AND TRACK OF THE
MESO-LOW. THERE IS REASONABLE MODEL AGREEMENT THAT THE LOW EXITS
THE APOSTLE ISLANDS AREA BY MID-DAY...THEN ROTATES
ANTI-CYCLONICALLY BACK AROUND TO THE NORTH SHORE...MAKING LANDFALL
IN THE VIN CITY OF TWO HARBORS TO SILVER BAY. IF THIS TRACK IS
CORRECT THEN AN INCH OR TWO OF VERY LOCALIZED SNOWFALL WILL BE
POSSIBLE IN THIS REGION THIS AFTERNOON AS WELL.
ELSEWHERE...A SHORT WAVE TRANSLATING EAST OVER SOUTH DAKOTA TODAY
WILL DROP SE ACROSS IOWA TONIGHT. THIS WAVE WILL SPREAD CLOUDS
OVER THE REGION...AS WELL AS BRING A CHANCE FOR LIGHT SNOW
ACCUMULATION OVERNIGHT THROUGH FRIDAY. AMOUNTS OF GENERALLY A HALF
INCH OR LESS ARE ANTICIPATED ATTM...WITH THE EXCEPTION OF AREAS
ADJACENT TO LAKE SUPERIOR WHERE HIGHER AMOUNTS MAY BE FOUND.
LONG TERM [FRIDAY NIGHT - THURSDAY]...
A MID/UPPER LEVEL TROUGH WILL MOVE THROUGH THE NORTHLAND EARLY THIS
WEEKEND AND PROVIDE LOW CHANCES OF LIGHT SNOW FOR MUCH OF THE FA
INTO SATURDAY. THE WNW FLOW THAT WILL DEVELOP IN THE WAKE OF THE
TROUGH COULD DEVELOP SOME LAKE EFFECT SNOW SHOWERS LATE SATURDAY AND
INTO EARLY SUNDAY IN IRON COUNTY IN NW WISCONSIN. THE MODELS ARE IN
REASONABLE AGREEMENT THAT A CLIPPER LIKE SYSTEM WILL PASS NEAR OR
NORTH OF THE MINNESOTA/CANADA BORDER SUNDAY AND EARLY NEXT WORK
WEEK...WHICH WILL PROVIDE MORE LOW CHANCES OF LIGHT SNOW. AN
ASSOCIATED COLD FRONT WILL PASS THROUGH THE NORTHLAND SUNDAY NIGHT.
THE NNW TO NW WINDS IN THE WAKE OF THE COLD FRONT COULD RESULT IN
LAKE EFFECT SNOW SHOWERS NEAR THE GOGEBIC RANGE IN NW WISCONSIN
MONDAY AND MONDAY NIGHT. TEMPERATURES THROUGH THE PERIOD SHOULD BE
NEAR NORMAL.
PREV DISCUSSION... /ISSUED 1146 PM CST WED DEC 26 2012/
AVIATION.../06Z TAF ISSUANCE/
CLOUD FORECASTS WILL BE A BIT TRICKY OVER THE DURATION OF THIS TAF
PERIOD. IT LOOKS LIKE THE LOWEST CIGS WILL BE NEAR LAKE
SUPERIOR...AS BANDS OF SNOW SHOWERS MOVE OFF THE LAKE INTO COASTAL
AREAS. INLAND...VFR CONDITIONS SHOULD BE MORE COMMON...WITH CLOUD
BASES GRADUALLY LOWERING DURING THE DAY AND INTO THURSDAY EVENING.
LOW PRESSURE WILL GRADUALLY MOVE EASTWARD INTO THE
REGION...BRINGING SOME LIGHT SNOW DURING THE DAY AND EVENING.
&&
.POINT TEMPS/POPS...
DLH 22 13 24 9 / 20 50 50 20
INL 10 4 20 4 / 10 20 20 30
BRD 19 11 22 7 / 10 50 30 20
HYR 23 11 26 10 / 10 40 40 20
ASX 25 13 26 15 / 20 40 40 30
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...WINTER WEATHER ADVISORY UNTIL NOON CST FRIDAY FOR MNZ020.
WI...NONE.
LS...NONE.
&&
$$
SHORT TERM...CLC
LONG TERM....KK
AREA FORECAST DISCUSSION
NWS GREAT FALLS MT
855 PM MST Fri Dec 28 2012
.DISCUSSION...
Update forthcoming. Have made a few adjustments to the pop and
weather grids this evening. Weak instability associated with a
passing shortwave has resulted in a little light snow in the West
Yellowstone area. This was depicted well on the 18z GFS run and also
with the HRRR analysis. The GFS decreases precipitation chances
after midnight as upper ridging develops over the area. Southwest
winds will continue overnight and keep temperatures generally above
zero. Emanuel
&&
.AVIATION...
Updated 0000Z.
VFR conditions will prevail at all TAF sites through the next 24
hours. Some upper-level clouds will move over the area tonight and
thicken during the day on Saturday ahead of the next disturbance.
Winds will remain breezy along the Rocky Mountain Front this evening
and then become lighter to around 10kts by midnight. Westerly winds
will increase again along the Rocky Mountain Front and adjacent
plains on Saturday. Some mountain obscuration is expected tonight
with widespread mountain obscuration by Saturday afternoon. MLV
&&
.PREV DISCUSSION...ISSUED 255 PM MST Fri Dec 28 2012
Tonight through Sunday...Current radar shows quiet conditions
throughout the area and will remain quiet through Saturday
evening. A shortwave will move across the area Saturday night
bringing light snow to most locations. Expect one inch or less in
the valleys and adjacent plains and generally 1 to 3 inches in the
mountains. Impacts with this system are expected to be minimal.
Light snow will taper off during the day on Sunday and will push out
of the area by Sunday evening. Main change to the forecast package
was to raise pops on Sunday...by using a model blend of the NAM and
SREF. Temperatures remain cool...and near seasonal averages on
Saturday...then dropping about 10 degrees on Sunday in the wake of
the shortwave. Mercer
Sunday Night through Thursday...Generally good agreement among
models through period. An upper level ridge of high pressure will
slowly build into Pacific Northwest. Daytime high temperatures will
warm to above normal for much of the forecast area Tuesday and will
remain through Friday. In the far northeast, cold air may remain
trapped in the Milk River Valley so have lowered temperatures a bit
in this area. With higher pressure over the Continental Divide,
breezy downslope winds will be common during the period. This ridge
will be quite dry, too, with downslope winds there will be little or
no chance of snow even over the mountains. Only possible exception
to this will be during the Wednesday time frame. Models diverge a
bit at this time with the GFS dropping shortwave energy and a weak
surface cold front through eastern Montana. Have tweaked pops up a
bit over my far eastern zones but am expecting the remainder of the
forecast area to remain dry. Models keep the ridge in place over the
northern Rockies through the end of the week so have dried out
precipitation for the entire area during this period. Britton/mpj
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 18 34 20 25 / 0 0 70 50
CTB 17 32 7 24 / 0 30 50 0
HLN 11 27 16 24 / 0 0 50 40
BZN 7 23 13 21 / 0 0 70 50
WEY 2 19 8 19 / 10 10 60 40
DLN 7 27 16 23 / 0 10 70 40
HVR 9 28 11 23 / 0 10 60 20
LWT 14 33 16 24 / 0 0 40 60
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
1234 PM CST THU DEC 27 2012
.AVIATION...
FOR THE 18Z TAF...-SN ASSOCIATED WITH AN UPPER LEVEL LOW CONTINUES
TO FALL ACROSS MUCH OF WESTERN AND NORTH CENTRAL NEBRASKA EARLY THIS
AFTERNOON...WITH VISIBILITIES LOWERING TO 1 1/2 UNDER THE HEAVIEST
OF BANDS. EXPECT PERIODS OF IFR AND MVFR TO CONTINUE ACROSS NORTH
CENTRAL NEBRASKA TERMINALS...SUCH AS KANW AND KONL THROUGH LATE
AFTERNOON AS THE UPPER LOW EJECTS ACROSS NORTHEASTERN NEBRASKA. FOR
SOUTHWEST AREA TERMINALS...STEADILY IMPROVING FLIGHT CONDITIONS WILL
BE EXPECTED THROUGH THE AFTERNOON...WITH THE POSSIBILITY OF VFR
RETURNING AT KIML AND KOGA BEFORE 20Z. OTHERWISE...SHORT TERM
GUIDANCE INDICATES CLEARING FROM SOUTHWEST TO NORTHEAST THROUGH THE
OVERNIGHT...GUIDANCE IS SPLIT ON WHETHER KLBF COMPLETELY CLEARS
OVERNIGHT TO VFR...WITH HALF OF THE SOLUTIONS INDICATING A RETURN TO
MVFR CEILINGS. THE GENERAL TREND OF THE FORECAST AT KLBF IS TO
GRADUALLY IMPROVE CEILINGS THROUGH THE OVERNIGHT...BUT SHORT-FUSED
UPDATES MAY BE NEEDED TO INCLUDE MVFR BACK INTO THE FORECAST. AT
KVTN...CONFIDENCE IS HIGHER IN MVFR CEILINGS HANGING ON THROUGH
SUNRISE...BUT GRADUALLY BREAKING FROM 12-18Z...WILL TREND THE
FORECAST IN THAT DIRECTION.
&&
.PREV DISCUSSION... /ISSUED 1037 AM CST THU DEC 27 2012/
UPDATE...
WIDESPREAD SNOW CONTINUES ACROSS MUCH OF THE FORECAST AREA...WITH
KLNX WSR-88D SHOWING THE HEAVIEST BAND NOW ACROSS NORTH CENTRAL
NEBRASKA. THIS BAND...ASSOCIATED WITH THE MAIN PV ANOMALY/UPPER
LOW WILL CONTINUE EAST...SPREADING THE HEAVIEST SNOW INTO
NORTHEASTERN PORTIONS OF THE CWA EARLY THIS AFTERNOON. FORECAST IS
ON TRACK...WITH ONLY MINOR REVISIONS IMPLEMENTED. PROXIMITY
SOUNDINGS ACROSS NORTH CENTRAL REVEAL A DEEP DENDRITIC LAYER CO-
LOCATED WITHIN A LAYER OF OMEGA. QPF AMOUNTS THUS FAR HAVE BEEN
LIGHT...GENERALLY 0.01 INCH OR LESS PER HR...WHICH THE SOUNDINGS
HAVE PICKED UP ON. HOWEVER DRY SNOW PRODUCTION HAS BEEN
EFFICIENT...WITH ACCUMULATIONS AMOUNTING TO OVER AN INCH OF DRY
FLUFFY SNOW AT KLBF OVER THE PAST 6 HOURS. TRENDED THE OVERALL QPF
AMOUNTS ACROSS THE CWA DOWNWARD...BUT INCREASED SNOW TO LIQUID
WATER RATIOS TO 25:1 AS OBSERVATIONS ARE SUGGESTING. THESE SMALL
REVISIONS DID LITTLE TO THE OVERALL EXPECTED STORM TOTAL SNOW
ACCUMULATIONS...WITH GENERALLY 2-4 INCHES OF FLUFFY SNOW EXPECTED
ACROSS NORTH CENTRAL NEBRASKA...1-2 INCHES ELSEWHERE.
PREV DISCUSSION... /ISSUED 354 AM CST THU DEC 27 2012/
SHORT TERM...TODAY THROUGH SATURDAY NIGHT
FORECAST CONCERNS THROUGH THIS PERIOD ARE SNOWFALL CHANCES AND
AMOUNTS FOR TODAY AND TONIGHT...THEN TEMPERATURES INTO THE
WEEKEND.
AT 08Z...WATER VAPOR IMAGERY SHOWED THE STRONG LOW PRESSURE SYSTEM
IMPACTING THE EAST COAST CENTERED OVER EASTERN VIRGINIA. RIDGING
WAS SITUATED OVER THE MISSISSIPPI RIVER VALLEY AS A FAIRLY LARGE
TROUGH COVERING THE WESTERN HALF OF THE CONUS. COMING OUT OF THE
TROUGH WAS AN UPPER LOW OVER EASTERN WYOMING...WHILE A PV ANOMALY
WAS SEEN OVER EASTERN COLORADO MOVING TOWARDS WESTERN NEBRASKA.
LOCALLY...RADAR ECHOES SPANNED ACROSS THE EASTERN PANHANDLE INTO
NORTHWEST NEBRASKA...WITH MORE CONVECTIVE LOOKING ECHOES OVER
CENTRAL NEBRASKA. NO PRECIPITATION WAS BEING REPORTED WITH THE
EASTERN ACTIVITY WHILE KAIA AND KSNY IN THE PANHANDLE HAD REPORTED
LIGHT SNOW BEING JUST OUTSIDE OF THE MAIN SNOW BAND. MODELS WOULD
INDICATE THE 700MB LOW OVER THE WESTERN PANHANDLE. THERE WAS A
GOOD MOISTURE FEED JUST TO THE EAST OF THE LOW WHICH HAD ITS
PRIMARY FOCUS INTO NORTHWEST NEBRASKA. THE RAP MODEL ALSO WAS
INDICATING SOME FRONTOGENETICAL FORCING AT 700 TO 600MB IN THIS SAME
AREA...WHICH WOULD FIT WITH WHAT IS ONGOING.
AS THE MORNING PROGRESSES...THE UPPER LOW OVER WYOMING WILL SHIFT
EAST INTO NORTH CENTRAL NEBRASKA AROUND MID-DAY THEN CONTINUE EAST
ALONG THE SOUTH DAKOTA/NEBRASKA BORDER INTO TONIGHT. ISENTROPIC
SURFACES FROM ROUGHLY 275K TO 290K ALL SHOWING DECENT LIFT AS WELL
AS MOISTURE TRANSPORT THROUGH THE MORNING /MAINLY OVER NORTHERN
NEBRASKA/...WHICH THEN SHIFTS EAST THIS AFTERNOON. HAVE ADJUSTED
PRECIPITATION CHANCES IN THIS FORECAST TO INCLUDE THE HIGHEST
CHANCES OVER THE PANHANDLE AND NORTHWEST NEBRASKA THIS
MORNING...THEN INTO NORTH CENTRAL NEBRASKA THIS AFTERNOON AS THE
WHOLE SYSTEM MOVES EAST. CONTINUED THE CHANCES OVER SOUTHWEST
NEBRASKA TODAY...BUT CONFIDENCE IS MUCH LESS IN THESE AREAS AND
DID BACK OFF ON CHANCES A BIT. REASONING FOR THIS IS THAT THIS
AREA WILL BE IN A FAVORABLE LOCATION FOR DRY AIR TO COME INTO THE
SYSTEM AROUND THE UPPER LOW...ALSO THE PV ANOMALY OVER COLORADO
HAS GOOD DARKENING IN THE WATER VAPOR IMAGERY INDICATING GOOD DRY
AIR ASSOCIATED WITH IT. AS THIS MOVES INTO SOUTHWEST NEBRASKA...IT
SHOULD LIMIT THE SNOWFALL. WILL PROBABLY SEE SOME SNOW IN THESE
AREAS THROUGH THE DAY...BUT BELIEVE IT WILL BE QUITE LIGHT AND
WILL NOT LAST LONG SO VERY LITTLE IF ANY ACCUMULATION IS EXPECTED.
IF IN FACT THIS OCCURS...THE FORECAST WILL LIKELY NEED TO BE
UPDATED TO REFLECT THE LOWER CHANCES FOR MEASURABLE SNOWFALL IN
THESE AREAS.
THE SYSTEM WILL NOT BE REAL FAST MOVING OUT OF THE LOCAL
AREA...WHICH WILL KEEP SNOW FALLING ACROSS NORTH CENTRAL NEBRASKA
TONIGHT BEFORE EXITING COMPLETELY ON FRIDAY. THERE HAS BEEN GOOD
MODEL AGREEMENT WITH KEEPING THE HIGHER SNOWFALL AMOUNTS JUST EAST
OF THE FORECAST AREA...MAINLY ALONG AND EAST OF HIGHWAY 14.
SOUNDINGS CONTINUE TO SHOW THE ENTIRE SATURATED LAYER /SURFACE
THROUGH 600MB/ IN THE DENTRITIC GROWTH ZONE...SO USED HIGH SNOW
RATIOS VARYING FROM 18:1 TO 23:1. EVEN WITH THIS...STORM TOTAL
SNOW AMOUNTS ACROSS HOLT AND BOYD COUNTIES ONLY SHOWING 2 TO 3
INCHES WITH A FEW LOCALIZED AREAS ABOVE 3 INCHES. GOING EAST OF
THE AREA AMOUNTS IN EXCESS OF 3 INCHES ARE LIKELY. WINDS SHOULD BE
FAIRLY LIGHT TODAY UNDER 15 MPH SO EVEN WITH THE HIGH SNOW
RATIOS GIVING HIGHER SNOW AMOUNTS DON/T FEEL THE IMPACTS WILL BE
HIGH SO WILL NOT PUT OUT AN ADVISORY FOR TODAY AND TONIGHT.
COLD AIR WILL REMAIN IN PLACE OVER THE FORECAST AREA TODAY...AND
WITH THE CLOUD COVER DON/T EXPECT HIGHS TO GET OUT OF THE TEENS.
TONIGHT AND FRIDAY...THE PRIMARY TROUGH WILL EXTEND FROM THE NORTHERN
PLANS THROUGH THE FOUR CORNERS. MEANWHILE...SEVERAL WEAK IMPULSES
OF SHORTWAVE ENERGY WILL QUICKLY PUSH SOUTH OUT OF CANADA INTO THE
CENTRAL PLAINS. THIS SHOULD KEEP AT LEAST SOME HIGH CLOUDS...BUT
MAY NOT BE TOO THICK. DID DROP LOWS ACROSS THE WESTERN PARTS OF
THE FORECAST AREA NEAR ZERO OR SLIGHTLY BELOW ZERO. IF CLOUDS
CLEAR...COULD CERTAINLY BE TOO WARM.
THE TROUGH DOES MOVE EAST INTO THE MISSISSIPPI RIVER VALLEY FRIDAY
NIGHT AND SATURDAY ALLOWING RIDGING TO START TO BUILD IN FOR THE
WEEKEND. THIS WILL BE THE START TO A SLOW WARMING TREND INTO NEXT
WEEK. NOT LOOKING FOR TEMPERATURES TO WARM DRAMATICALLY AS
SATURDAY HAS HIGHS NEAR THE FREEZING POINT. AREAS WITH SNOW COVER
WILL SEE A GREATER IMPACT IN TEMPERATURES SO IT IS LIKELY THAT
THERE WILL BE ADJUSTMENTS AFTER THE SNOW FIELD IS SAMPLED AFTER
TONIGHT.
LONG TERM...SUNDAY THROUGH WEDNESDAY
THIS PERIOD BEGINS WITH RIDGING ACROSS THE PLAINS...HOWEVER THERE
IS GOOD CONSENSUS FROM THE MODEL OUTPUT BRINGING THE NEXT STRONG
TROUGH INTO THE WEST COAST ON SUNDAY. ALSO...SEVERAL STRONG
SHORTWAVE TROUGHS ARE BEING SHOWN IN THE NORTHERN STREAM WHICH
COULD COME SOUTH FAR ENOUGH TO KEEP THE RIDGE FROM BUILDING TOO
FAR NORTH. THIS WILL KEEP TEMPERATURES FROM MODERATING TOO MUCH
THROUGH THE FIRST PART OF NEXT WEEK. THE FIRST OF THESE SYSTEMS
COMES THROUGH SUNDAY NIGHT...WHICH SHOULDN/T HAVE ANY OTHER IMPACT
BUT TO BRING SOME COOLER AIR SOUTH INTO NEBRASKA. FOR MONDAY AND
BEYOND...THE MODELS BEGIN TO DIVERGE WITH THE EASTERN MOVEMENT OF
THE WEST COAST TROUGH. THE ECMWF IS SLOWER...WHICH THEN ALLOWS A
STRONG NORTHERN STREAM SYSTEM TO PENETRATE INTO NEBRASKA TUESDAY
NIGHT. THE GFS IS QUICKER AND KEEPS THIS SYSTEM UP OVER MINNESOTA
AND THE GREAT LAKES. EITHER WAY...MOISTURE LOOKS TO BE HELD TO THE
THE MAIN UPPER LOW WHICH STAYS WELL SOUTH SO NO FURTHER
PRECIPITATION CHANCES ARE IN THE FORECAST BEYOND FRIDAY MORNING.
HYDROLOGY...
ICE JAMS ARE LIKELY TO CONTINUE AT VARIOUS LOCATIONS IN CENTRAL
AND WESTERN NEBRASKA. EXCEPT FOR STRETCHES ALONG THE NORTH PLATTE
RIVER...THERE ARE NO INDICATIONS OF FLOODING. BE AWARE THAT THE
FORMATION AND BREAK-UP OF ICE JAMS ARE NOTORIOUSLY DIFFICULT TO
FORECAST...SO RIVERS AND STREAMS IN THE AREA MAY RISE AND FALL
ERRATICALLY. WE DO HAVE FAIRLY HIGH CONFIDENCE THAT...WITH
TEMPERATURES MODERATING SOME...THE LEVELS ARE NOT LIKELY TO HAVE
NEW SHARP RISES ABOVE CURRENT LEVELS.
THE NORTH PLATTE RIVER AT LEWELLEN CONTINUES TO FALL
SLOWLY...POSSIBLY BECAUSE THE RIVER HAS BECOME COMPLETELY FROZEN
AND THE ICE IS NO LONGER BEING CARRIED TOWARD THE INLET OF LAKE
MCCONAUGHY. AT THE NORTH PLATTE GAGE...THE LEVEL CONTINUES ABOVE
FLOOD STAGE AND IS LIKELY TO CONTINUE FOR AT LEAST THIS WEEKEND.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM/EXTENDED...BROOKS
AVIATION/UPDATE...JACOBS
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
1207 PM CST THU DEC 27 2012
.AVIATION...
18Z TAFS FOR KOFK...KOMA AND KLNK.
MID LEVEL SPEED MAX EXTENDING INTO NORTHWEST MISSOURI
THIS MORNING HAS HELPED TO ENHANCE SNOWFALL OVER NORTHEAST
NEBRASKA AND WEST CENTRAL IOWA. AS MAX SHIFTS EAST EXPECT SNOWFALL
RATES TO DIMINISH THIS AFTERNOON. UPPER LOW TRACKS SLOWLY EAST
ACROSS THE AREA THROUGH THE PERIOD WITH MVFR CIGS AND/OR VSBY
EXPECTED AT KOMA AND KLNK THROUGH 00Z THEN IFR CIGS AND MVFR VSBY
DEVELOPING THROUGH 06Z. SOME POTENTIAL FOR FZDZ AT KLNK YET. KOFK
LIKELY TO KEEP IFR OR LIFR CONDITIONS THROUGH MUCH OF THE PERIOD
BUT VSBY IMPROVING AS BETTER FORCING MOVES EAST AND SNOWFALL
BECOMES LIGHTER.
&&
.PREV DISCUSSION... /ISSUED 302 AM CST THU DEC 27 2012/
DISCUSSION...
.SNOW AMOUNTS AND CHANCES FOR FREEZING DRIZZLE THE MAIN
CONCERNS...
FOR THIS FORECAST THE MAIN FEATURE OF INTEREST WILL BE THE POTENT
SHORTWAVE THAT IS CURRENTLY SPINNING ALONG THE WYOMING-COLORADO
BORDER PER WATER VAPOR LOOP AND THE PRECIPITATION IT WILL PRODUCE
TODAY AND FRIDAY. THE MORE THIS SYSTEM DEVELOPS THE MORE
IMPRESSIVE IT APPEARS TO BE...ESPECIALLY FOR NORTHEAST NEBRASKA.
500 MB HEIGHT FALLS ON THE 00Z RAOBS WERE 100-120 METERS IN THE
BASE OF THE TROF...WITH DENVER SHOWING A 130 METER FALL AT 300 MB.
150 KNOT JET STREAK WAS NOTED AT 25O MB OVER ARIZONA. REGIONAL
RADAR MOSAIC SHOWS SNOW RAPIDLY DEVELOPING/EXPANDING FROM WESTERN
KANSAS INTO WESTERN AND CENTRAL NEBRASKA IN RESPONSE TO THE
SYSTEMS VERTICAL MOTION AND MOISTURE AROUND 850 MB AS SEEN ON
DODGE CITY AND NORTH PLATTE SOUNDINGS. 08Z SURFACE ANALYSIS SHOWED
EARLY STAGES OF INVERTED TROF TAKING SHAPE WITH 1003MB PRESSURES
OBSERVED IN SOUTHEAST COLORADO.
THE DODGE CITY AND NORTH PLATTE SOUNDINGS DID HAVE A FEW DRY
LAYERS AS WELL...AND THESE DRY LAYERS DO COMPLICATE THE
PRECIPITATION FORECAST. GENERALLY THE NAM/GFS/RAP ARE IN DECENT
AGREEMENT ON THE PRECIPITATION FORECAST AND THE MOIST AND DRY
LAYERS. HOWEVER THERE IS CONCERN FOR A LIGHT FREEZING DRIZZLE
SCENARIO MAINLY IN THE SOUTHERN HALF OF THE FORECAST AREA DUE TO A
LOW LEVEL SATURATED LAYER THAT IS WARMER THAN -10C AND THEREFORE
WOULD PRIMARILY CONTAIN SUPERCOOLED DRIZZLE AS OPPOSED TO
SNOWFLAKES. THE MODELS SHOW LITTLE OR NO QPF OVER SOUTHEAST
NEBRASKA THROUGH 12Z FRIDAY...HOWEVER THE MODELS OFTEN POORLY HANDLE
THESE VERY LIGHT ICING EVENTS BECAUSE THE QPF IS QUITE LIGHT BUT
ALSO BECAUSE THE LAYERS ARE SHALLOW. THE FORECAST SOUNDINGS FROM
THE NAM AND ESPECIALLY THE RAP SUPPORT AT LEAST SOME LIGHT
FREEZING DRIZZLE MAINLY ALONG AND SOUTH OF INTERSTATE 80 AT
VARIOUS TIMES FROM LATE THIS AFTERNOON INTO TONIGHT...THEREFORE
WE HAVE ADDED PATCHY FREEZING DRIZZLE...OR AREAS OF FREEZING
DRIZZLE...TO THE SNOW CHANCES IN THOSE LOCATIONS. CONFIDENCE IN
THIS LIGHT ICING SCENARIO IS NOT HIGH ENOUGH TO ISSUE A WINTER
WEATHER ADVISORY FOR THE ABOVE MENTIONED AREAS. HOWEVER IF NEW
OBSERVATIONS AND MODEL RUNS SUGGEST A HIGHER LIKELIHOOD OF
FREEZING DRIZZLE AN ADVISORY MAY BE CONSIDERED LATER TODAY.
OTHERWISE THE TRACK OF THE LOW FAVORS THE HEAVIER SNOWS TO FALL IN
NORTHEAST NEBRASKA WHERE THE GOING WINTER WEATHER ADVISORY IS AT.
WE DID ADD ONE MORE TIER OF COUNTIES TO THE ADVISORY INCLUDING
ALBION AND NORFOLK. THIS SYSTEM IS UNIQUE IN THAT IT HAS A VERY
DEEP SATURATED LAYER THAT IS IN THE DENDRITIC GROWTH ZONE...AROUND
250 MB OR ABOUT 10000 FEET DEEP...YIELDING SNOW-LIQUID RATIOS AS
HIGH AS 20-1. BECAUSE OF THIS WE ALSO INCREASED SNOW AMOUNTS IN
NORTHEAST NEBRASKA ABOUT 1 MORE INCH. FORTUNATELY THERE WILL NOT
BE A LOT OF WIND WITH THIS SYSTEM SO LITTLE BLOWING AND DRIFTING
IS EXPECTED. SOME LOCATIONS IN THE ADVISORY AREA SHOULD SEE 4-5
INCHES OF DRY/FLUFFY SNOW STARTING TODAY AND ENDING FRIDAY
MORNING.
CONFIDENCE IN THE EXACT SNOW AMOUNTS IS MUCH LOWER TO THE SOUTH
OF THE ADVISORY AREA...MAINLY FROM THE LINCOLN TO OMAHA METRO
AREAS. HOWEVER...THERE IS LITTLE SUPPORT FOR MORE THAN 2 INCHES
GIVEN THE DRY LAYERS THAT WILL NEED TO BE SATURATED AND THE
WEAKER FORCING JUST SOUTH OF THE 700 MB LOW TRACK. CURRENTLY WE
ARE KEEPING THE 1-2 INCH AMOUNTS FOR LINCOLN-OMAHA AND THIS LOOKS
REASONABLE BY NOON FRIDAY WHEN ANY LIGHT SNOW ON THE BACK SIDE OF
THE LOW FINALLY ENDS. STARTED THE CHANCES FOR SNOW A BIT LATER
EAST OF A LINE FROM LINCOLN TO FREMONT...MAINLY CLOSER TO 18Z
TODAY...PRIMARILY DUE TO THE TIME IT WILL TAKE TO SATURATE THE
DRY LOW LEVELS IN THAT AREA.
TEMPERATURE AND WIND FORECASTS WERE ONLY SLIGHTLY ADJUSTED AS THE
PATTERN REMAINS FAIRLY COLD BUT DRY AFTER FRIDAY.
NIETFELD
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER WEATHER ADVISORY UNTIL 6 AM CST FRIDAY FOR NEZ011-012-
015>018-030>034.
IA...WINTER WEATHER ADVISORY UNTIL 6 AM CST FRIDAY FOR IAZ043-055.
&&
$$
FOBERT
AREA FORECAST DISCUSSION
NWS HASTINGS NE
1155 AM CST THU DEC 27 2012
.AVIATION...18Z KGRI TAF. MAIN ISSUES WILL BE WITH VISIBILITY
RESTRICTIONS WITH SNOW...AND STRATUS. VISIBILITY SHOULD IMPROVE
WITH TIME AS SNOW EVENTUALLY TAPERS AND MOVES OUT THIS
EVENING...BUT STRATUS WILL PROBABLY LOWER AS THE NIGHT WEARS ON
INTO THE EARLY MORNING ON FRIDAY...BEFORE RAISING AGAIN LATE
FRIDAY MORNING. WIND COULD GET A BIT MORE OF A GUST BY LATE
MORNING FRIDAY.
&&
PREV DISCUSSION... /ISSUED 243 AM CST THU DEC 27 2012/
SHORT TERM...THE MAIN ISSUE TO DEAL WITH IS TODAY/S LIGHT SNOW
EVENT.
WATER VAPOR AND INFRARED SATELLITE IMAGERY SUGGEST THE UPPER LEVEL
CIRCULATION SET TO IMPACT OUR AREA IS CENTERED IN THE TRI-STATE
CONFLUENCE OF WY/CO/NE. SPOKE OF ENERGY ALONG WITH WARM ADVECTION
PUSHING THROUGH THE FORECAST AT THIS TIME. RETURNS FROM NEARBY
RADARS SUGGEST PRECIPITATION IS DEVELOPING ALOFT IN THIS WARM
ADVECTION. NOTHING HAS REPORTEDLY MADE IT TO THE GROUND WITH DRY
AIR IN LOWER LEVELS OF THE ATMOSPHERE. THAT ALL SHOULD CHANGE
EARLY THIS MORNING...SAY AROUND DAWN...WITH LIGHT SNOWFALL STARTING
TO REACH THE SURFACE. SHORT TERM MODEL DATA /HRRR AND WRF/ POINT
TOWARD A BAND OF SNOW DEVELOPING IN THE VICINITY OF HIGHWAY 281
NAM QUICKLY LIFTING NORTH/NORTHEAST. THESE FINER DETAILS FIT WITH
THE NAM/GFS/SREF OUTPUT...WHICH EVENTUALLY PUT THE GREATEST
PRECIPITATION IN NORTHEAST NEBRASKA OF ABOUT 0.30". MEANWHILE...
THE NORTH/EAST FORECAST AREA MAY PICK UP A TENTH OR TWO OF LIQUID
EQUIVALENT MOISTURE...EQUATING INTO 1 TO 2 INCHES...MAYBE LOCALLY
3 INCHES OF SNOW. THE AREA AT MOST RISK FOR 3 INCHES...AND IT MAY
NOT BE THAT MUCH RISK...WOULD BE NORTHERN NANCE COUNTY...OR NORTHEAST
GREELEY COUNTY. THE VAST MAJORITY OF OUR NEBRASKA FORECAST IS IN
THE 1 TO 2 INCH RANGE...WITH LESS THAN 1 INCH IN NORTHERN KANSAS.
AT THIS TIME...WITH LIMITED WIND INFLUENCES...AND ONLY A SMALL PART
OF THE FORECAST AREA IN LINE FOR MARGINAL ADVISORY LEVEL SNOW
AMOUNTS...WILL NOT ISSUE ANY HEADLINES. IN FACT...IF YOU BUY INTO
THE 05Z HRRR OUTPUT...ONLY THE FAR NORTHEAST FORECAST AREA WOULD
CATCH 1 TO 2 INCHES OF SNOW...AND THE REST OF THE AREA AN INCH OR
LESS. AT THIS POINT...THERE SEEMS TO BE ENOUGH REASON NOT TO ISSUE
ANY ADVISORIES FOR THIS EVENT.
SHOULD MENTION...NAM SOUNDINGS IN THE SOUTHEAST PART OF THE FORECAST
AREA...ALONG WITH FUZZY NATURE OF PRECIPITATION OUTLOOK...SUGGEST A
BIT OF FREEZING DRIZZLE COULD DEVELOP DURING THE EVENING HOURS. LIFT
IS THE QUESTION...MEANING IS THERE ENOUGH? THINK THERE COULD BE A
COUPLE OF HOURS OF FREEZING DRIZZLE TYPE PRECIPITATION IN THIS AREA
AND HAVE ADDED THAT TO THE FORECAST GRIDS. NOT A HUGE DEAL...AND MAY
NOT MATERIALIZE...BUT WOULDN/T BE SHOCKED IF IT DID PAN OUT.
ON FRIDAY...THE MEANDERING NATURE OF THE UPPER LEVEL LOW TO THE
SOUTHEAST WILL KEEP CLOUDS AROUND FOR A GOOD PART OF THE DAY. FAR
EASTERN FORECAST AREA MAY EVEN SEE A LINGERING FLURRY EARLY IN THE
MORNING. ASIDE FROM THAT...NORTHWEST WINDS WILL DEVELOP...AND MAY
EVEN TURN SNEAKY BREEZY IF CLEARING DEVELOPS MORE RAPIDLY. FRIDAY
IS STILL A PART OF THE CURRENT COLD SPELL WITH HIGHS STRUGGLING FOR
ABOUT 20 MOST AREAS. THAT ALL STARTS TO CHANGE FRIDAY NIGHT...AS
DOWN-SLOPING WESTERLY WINDS SET UP AND LASTS INTO THE DAY SATURDAY.
THIS WILL RESULT IN SATURDAY BEING MUCH WARMER...RELATIVE TO RECENT
DAYS...WITH HIGHS IN THE UPPER 20S AND LOWER 30S AND PLENTY OF
SUNSHINE. THAT WON/T NECESSARILY MELT A WHOLE LOT...AND ITS STILL
BELOW NORMAL SOME 5 TO 7 DEGREES...BUT ITS AT LEAST A START.
LONG TERM...STARTING SUNDAY MORNING...SUNDAY IS SHAPING UP TO BE
THE WARMEST DAY IN JUST OVER A WEEK AS THE COMBINATION OF WARMER AIR
SURGING NORTHWARD AHEAD OF AN APPROACHING LOW LEVEL TROUGH/FRONT AND
MOSTLY SUNNY SKIES UNDER THE INFLUENCE OF A BUILDING UPPER LEVEL
RIDGE...WILL RESULT IN A RETURN TO NEAR SEASONAL TEMPERATURES FOR
THE END OF DECEMBER. AS A RESULT...EXPECT TO SEE AFTERNOON
TEMPERATURES ACROSS SOUTH CENTRAL NEBRASKA APPROACH THE FREEZING
MARK...WITH UPPER 30S TO NEAR 40 DEGREES CURRENTLY FORECAST FOR
PORTIONS OF NORTH CENTRAL KANSAS. WHILE THIS LIKELY WILL NOT BE WARM
ENOUGH TO RESULT IN ANY SIGNIFICANT MELTING OF SNOW/ICE ON THE
GROUND...IT WILL LIKELY BE THE FIRST DAY SINCE DECEMBER 22ND THAT
TEMPERATURES WILL CLIMB ABOVE THE FREEZING MARK ACROSS THE MAJORITY
OF THE FORECAST AREA. THIS BRIEF WARM UP...HOWEVER...IS EXPECTED TO
BE FAIRLY SHORT LIVED...AS GLOBAL MODELS ARE INDICATING COOLER AIR
BEHIND THE APPROACHING TROUGH/FRONT...WHICH WILL BEGIN TO FILTER IN
ACROSS THE LOCAL AREA TO START THE NEW WORK WEEK. AS A
RESULT...EXPECT A RETURN TO SUBFREEZING AFTERNOON TEMPERATURES
MONDAY AFTERNOON WITH LITTLE EVIDENCE FOR ENOUGH LOW LEVEL MOISTURE
OR FORCING TO JUSTIFY ANYTHING OTHER THAN AN INCREASE IN CLOUDS
ACROSS THE LOCAL AREA MONDAY.
THEREAFTER...THE GLOBAL MODELS BEGIN TO DIVERGE SOME WITH THEIR
HANDLING OF AN UPPER LEVEL LOW ACROSS THE DESERT SOUTHWEST...WITH
THE GFS MAINTAINING A MUCH MORE PROGRESSIVE FLOW PATTERN THAN THE
EC...WHICH HAS BEEN TRYING TO CUT OFF THE UPPER LEVEL LOW ACROSS
NORTHERN MEXICO. HOWEVER...IN BOTH SCENARIOS...THE NORTHERN JET IS
FORECAST TO STEER AN UPPER LEVEL DISTURBANCE ACROSS NEBRASKA TUESDAY
NIGHT/WEDNESDAY...WHICH ONCE AGAIN IS EXPECTED TO HAVE A LACK IN
APPRECIABLE LOW LEVEL MOISTURE...WITH LITTLE MORE THAN A FEW HIGH
CLOUDS AND A CONTINUATION OF SUB FREEZING TEMPERATURES EXPECTED TO
PERSIST AS A RESULT. JUST BEYOND THE CURRENT SCOPE OF THE
FORECAST...THERE ARE SOME INDICATIONS THAT ANOTHER UPPER LEVEL RIDGE
OF HIGH PRESSURE WILL BUILD ACROSS THE CENTRAL PLAINS IN CONCERT
WITH A MORE SIGNIFICANT DOWN-SLOPING LOW LEVEL FLOW...WHICH MAY
RESULT IN TEMPERATURES WARMING ABOVE CLIMO TOWARDS THE END OF NEXT
WEEK.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
AVIATION...HEINLEIN
SHORT TERM...NOAA/NWS/MORITZ
LONG TERM...SAR
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
1037 AM CST THU DEC 27 2012
.UPDATE...
WIDESPREAD SNOW CONTINUES ACROSS MUCH OF THE FORECAST AREA...WITH
KLNX WSR-88D SHOWING THE HEAVIEST BAND NOW ACROSS NORTH CENTRAL
NEBRASKA. THIS BAND...ASSOCIATED WITH THE MAIN PV ANOMALY/UPPER
LOW WILL CONTINUE EAST...SPREADING THE HEAVIEST SNOW INTO
NORTHEASTERN PORTIONS OF THE CWA EARLY THIS AFTERNOON. FORECAST IS
ON TRACK...WITH ONLY MINOR REVISIONS IMPLEMENTED. PROXIMITY
SOUNDINGS ACROSS NORTH CENTRAL REVEAL A DEEP DENDRITIC LAYER CO-
LOCATED WITHIN A LAYER OF OMEGA. QPF AMOUNTS THUS FAR HAVE BEEN
LIGHT...GENERALLY 0.01 INCH OR LESS PER HR...WHICH THE SOUNDINGS
HAVE PICKED UP ON. HOWEVER DRY SNOW PRODUCTION HAS BEEN
EFFICIENT...WITH ACCUMULATIONS AMOUNTING TO OVER AN INCH OF DRY
FLUFFY SNOW AT KLBF OVER THE PAST 6 HOURS. TRENDED THE OVERALL QPF
AMOUNTS ACROSS THE CWA DOWNWARD...BUT INCREASED SNOW TO LIQUID
WATER RATIOS TO 25:1 AS OBSERVATIONS ARE SUGGESTING. THESE SMALL
REVISIONS DID LITTLE TO THE OVERALL EXPECTED STORM TOTAL SNOW
ACCUMULATIONS...WITH GENERALLY 2-4 INCHES OF FLUFFY SNOW EXPECTED
ACROSS NORTH CENTRAL NEBRASKA...1-2 INCHES ELSEWHERE.
&&
.PREV DISCUSSION... /ISSUED 542 AM CST THU DEC 27 2012/
AVIATION...
LIGHT SNOW IS EXPECTED TO CONTINUE NORTH AND WEST OF AN
ANW-TIF-MHN-OGA LINE THROUGH 21Z WITH THE HEAVIEST FROM 14-18Z.
CEILINGS BELOW 3000 FEET AGL ARE LIKELY WITH A FAIRLY STRONG
PROBABILITY OF 1000-2000 FEET AGL. IN ADDITION...WIDESPREAD
VISIBILITY BELOW 3SM CAN BE EXPECTED IN THE HEAVIER SNOW WITH LESS
THAN 1SM POSSIBLE. LOW CEILING AND VISIBILITY MAY CONTINUE UNTIL AT
LEAST THIS EVENING 03Z...ESPECIALLY IN NORTH CENTRAL NEBRASKA.
PREV DISCUSSION... /ISSUED 354 AM CST THU DEC 27 2012/
SHORT TERM...TODAY THROUGH SATURDAY NIGHT
FORECAST CONCERNS THROUGH THIS PERIOD ARE SNOWFALL CHANCES AND
AMOUNTS FOR TODAY AND TONIGHT...THEN TEMPERATURES INTO THE
WEEKEND.
AT 08Z...WATER VAPOR IMAGERY SHOWED THE STRONG LOW PRESSURE SYSTEM
IMPACTING THE EAST COAST CENTERED OVER EASTERN VIRGINIA. RIDGING
WAS SITUATED OVER THE MISSISSIPPI RIVER VALLEY AS A FAIRLY LARGE
TROUGH COVERING THE WESTERN HALF OF THE CONUS. COMING OUT OF THE
TROUGH WAS AN UPPER LOW OVER EASTERN WYOMING...WHILE A PV ANOMALY
WAS SEEN OVER EASTERN COLORADO MOVING TOWARDS WESTERN NEBRASKA.
LOCALLY...RADAR ECHOES SPANNED ACROSS THE EASTERN PANHANDLE INTO
NORTHWEST NEBRASKA...WITH MORE CONVECTIVE LOOKING ECHOES OVER
CENTRAL NEBRASKA. NO PRECIPITATION WAS BEING REPORTED WITH THE
EASTERN ACTIVITY WHILE KAIA AND KSNY IN THE PANHANDLE HAD REPORTED
LIGHT SNOW BEING JUST OUTSIDE OF THE MAIN SNOW BAND. MODELS WOULD
INDICATE THE 700MB LOW OVER THE WESTERN PANHANDLE. THERE WAS A
GOOD MOISTURE FEED JUST TO THE EAST OF THE LOW WHICH HAD ITS
PRIMARY FOCUS INTO NORTHWEST NEBRASKA. THE RAP MODEL ALSO WAS
INDICATING SOME FRONTOGENETICAL FORCING AT 700 TO 600MB IN THIS SAME
AREA...WHICH WOULD FIT WITH WHAT IS ONGOING.
AS THE MORNING PROGRESSES...THE UPPER LOW OVER WYOMING WILL SHIFT
EAST INTO NORTH CENTRAL NEBRASKA AROUND MID-DAY THEN CONTINUE EAST
ALONG THE SOUTH DAKOTA/NEBRASKA BORDER INTO TONIGHT. ISENTROPIC
SURFACES FROM ROUGHLY 275K TO 290K ALL SHOWING DECENT LIFT AS WELL
AS MOISTURE TRANSPORT THROUGH THE MORNING /MAINLY OVER NORTHERN
NEBRASKA/...WHICH THEN SHIFTS EAST THIS AFTERNOON. HAVE ADJUSTED
PRECIPITATION CHANCES IN THIS FORECAST TO INCLUDE THE HIGHEST
CHANCES OVER THE PANHANDLE AND NORTHWEST NEBRASKA THIS
MORNING...THEN INTO NORTH CENTRAL NEBRASKA THIS AFTERNOON AS THE
WHOLE SYSTEM MOVES EAST. CONTINUED THE CHANCES OVER SOUTHWEST
NEBRASKA TODAY...BUT CONFIDENCE IS MUCH LESS IN THESE AREAS AND
DID BACK OFF ON CHANCES A BIT. REASONING FOR THIS IS THAT THIS
AREA WILL BE IN A FAVORABLE LOCATION FOR DRY AIR TO COME INTO THE
SYSTEM AROUND THE UPPER LOW...ALSO THE PV ANOMALY OVER COLORADO
HAS GOOD DARKENING IN THE WATER VAPOR IMAGERY INDICATING GOOD DRY
AIR ASSOCIATED WITH IT. AS THIS MOVES INTO SOUTHWEST NEBRASKA...IT
SHOULD LIMIT THE SNOWFALL. WILL PROBABLY SEE SOME SNOW IN THESE
AREAS THROUGH THE DAY...BUT BELIEVE IT WILL BE QUITE LIGHT AND
WILL NOT LAST LONG SO VERY LITTLE IF ANY ACCUMULATION IS EXPECTED.
IF IN FACT THIS OCCURS...THE FORECAST WILL LIKELY NEED TO BE
UPDATED TO REFLECT THE LOWER CHANCES FOR MEASURABLE SNOWFALL IN
THESE AREAS.
THE SYSTEM WILL NOT BE REAL FAST MOVING OUT OF THE LOCAL
AREA...WHICH WILL KEEP SNOW FALLING ACROSS NORTH CENTRAL NEBRASKA
TONIGHT BEFORE EXITING COMPLETELY ON FRIDAY. THERE HAS BEEN GOOD
MODEL AGREEMENT WITH KEEPING THE HIGHER SNOWFALL AMOUNTS JUST EAST
OF THE FORECAST AREA...MAINLY ALONG AND EAST OF HIGHWAY 14.
SOUNDINGS CONTINUE TO SHOW THE ENTIRE SATURATED LAYER /SURFACE
THROUGH 600MB/ IN THE DENTRITIC GROWTH ZONE...SO USED HIGH SNOW
RATIOS VARYING FROM 18:1 TO 23:1. EVEN WITH THIS...STORM TOTAL
SNOW AMOUNTS ACROSS HOLT AND BOYD COUNTIES ONLY SHOWING 2 TO 3
INCHES WITH A FEW LOCALIZED AREAS ABOVE 3 INCHES. GOING EAST OF
THE AREA AMOUNTS IN EXCESS OF 3 INCHES ARE LIKELY. WINDS SHOULD BE
FAIRLY LIGHT TODAY UNDER 15 MPH SO EVEN WITH THE HIGH SNOW
RATIOS GIVING HIGHER SNOW AMOUNTS DON/T FEEL THE IMPACTS WILL BE
HIGH SO WILL NOT PUT OUT AN ADVISORY FOR TODAY AND TONIGHT.
COLD AIR WILL REMAIN IN PLACE OVER THE FORECAST AREA TODAY...AND
WITH THE CLOUD COVER DON/T EXPECT HIGHS TO GET OUT OF THE TEENS.
TONIGHT AND FRIDAY...THE PRIMARY TROUGH WILL EXTEND FROM THE NORTHERN
PLANS THROUGH THE FOUR CORNERS. MEANWHILE...SEVERAL WEAK IMPULSES
OF SHORTWAVE ENERGY WILL QUICKLY PUSH SOUTH OUT OF CANADA INTO THE
CENTRAL PLAINS. THIS SHOULD KEEP AT LEAST SOME HIGH CLOUDS...BUT
MAY NOT BE TOO THICK. DID DROP LOWS ACROSS THE WESTERN PARTS OF
THE FORECAST AREA NEAR ZERO OR SLIGHTLY BELOW ZERO. IF CLOUDS
CLEAR...COULD CERTAINLY BE TOO WARM.
THE TROUGH DOES MOVE EAST INTO THE MISSISSIPPI RIVER VALLEY FRIDAY
NIGHT AND SATURDAY ALLOWING RIDGING TO START TO BUILD IN FOR THE
WEEKEND. THIS WILL BE THE START TO A SLOW WARMING TREND INTO NEXT
WEEK. NOT LOOKING FOR TEMPERATURES TO WARM DRAMATICALLY AS
SATURDAY HAS HIGHS NEAR THE FREEZING POINT. AREAS WITH SNOW COVER
WILL SEE A GREATER IMPACT IN TEMPERATURES SO IT IS LIKELY THAT
THERE WILL BE ADJUSTMENTS AFTER THE SNOW FIELD IS SAMPLED AFTER
TONIGHT.
LONG TERM...SUNDAY THROUGH WEDNESDAY
THIS PERIOD BEGINS WITH RIDGING ACROSS THE PLAINS...HOWEVER THERE
IS GOOD CONSENSUS FROM THE MODEL OUTPUT BRINGING THE NEXT STRONG
TROUGH INTO THE WEST COAST ON SUNDAY. ALSO...SEVERAL STRONG
SHORTWAVE TROUGHS ARE BEING SHOWN IN THE NORTHERN STREAM WHICH
COULD COME SOUTH FAR ENOUGH TO KEEP THE RIDGE FROM BUILDING TOO
FAR NORTH. THIS WILL KEEP TEMPERATURES FROM MODERATING TOO MUCH
THROUGH THE FIRST PART OF NEXT WEEK. THE FIRST OF THESE SYSTEMS
COMES THROUGH SUNDAY NIGHT...WHICH SHOULDN/T HAVE ANY OTHER IMPACT
BUT TO BRING SOME COOLER AIR SOUTH INTO NEBRASKA. FOR MONDAY AND
BEYOND...THE MODELS BEGIN TO DIVERGE WITH THE EASTERN MOVEMENT OF
THE WEST COAST TROUGH. THE ECMWF IS SLOWER...WHICH THEN ALLOWS A
STRONG NORTHERN STREAM SYSTEM TO PENETRATE INTO NEBRASKA TUESDAY
NIGHT. THE GFS IS QUICKER AND KEEPS THIS SYSTEM UP OVER MINNESOTA
AND THE GREAT LAKES. EITHER WAY...MOISTURE LOOKS TO BE HELD TO THE
THE MAIN UPPER LOW WHICH STAYS WELL SOUTH SO NO FURTHER
PRECIPITATION CHANCES ARE IN THE FORECAST BEYOND FRIDAY MORNING.
HYDROLOGY...
ICE JAMS ARE LIKELY TO CONTINUE AT VARIOUS LOCATIONS IN CENTRAL
AND WESTERN NEBRASKA. EXCEPT FOR STRETCHES ALONG THE NORTH PLATTE
RIVER...THERE ARE NO INDICATIONS OF FLOODING. BE AWARE THAT THE
FORMATION AND BREAK-UP OF ICE JAMS ARE NOTORIOUSLY DIFFICULT TO
FORECAST...SO RIVERS AND STREAMS IN THE AREA MAY RISE AND FALL
ERRATICALLY. WE DO HAVE FAIRLY HIGH CONFIDENCE THAT...WITH
TEMPERATURES MODERATING SOME...THE LEVELS ARE NOT LIKELY TO HAVE
NEW SHARP RISES ABOVE CURRENT LEVELS.
THE NORTH PLATTE RIVER AT LEWELLEN CONTINUES TO FALL
SLOWLY...POSSIBLY BECAUSE THE RIVER HAS BECOME COMPLETELY FROZEN
AND THE ICE IS NO LONGER BEING CARRIED TOWARD THE INLET OF LAKE
MCCONAUGHY. AT THE NORTH PLATTE GAGE...THE LEVEL CONTINUES ABOVE
FLOOD STAGE AND IS LIKELY TO CONTINUE FOR AT LEAST THIS WEEKEND.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM/EXTENDED...BROOKS
UPDATE/AVIATION...JACOBS
AREA FORECAST DISCUSSION
NWS HASTINGS NE
547 AM CST THU DEC 27 2012
.AVIATION...12Z KGRI TAF...DETERIORATING CONDS EXPECTED AT KGRI
OVER THE NEXT FEW HOURS AS AN APPROACHING WINTER STORM SPREADS
SOME -SN AND REDUCED CIGS/VSBYS ACROSS THE AREA. WHILE PREVAILING
VFR CONDS ARE EXPECTED THROUGH ABOUT 27/14Z...WITH A SMALL CHANCE
OF A MVFR CIG/VSBY IN A PASSING BAND OF -SN...EXPECT PREVAILING
MVFR CIGS TO DEVELOP BY 27/14Z...WITH TEMPO IFR CIG/VSBY AS THE
BRUNT OF THE DISTURBANCE MOVES ACROSS SOUTH CENTRAL NEBRASKA
BETWEEN 27/14Z-27/18Z. THEREAFTER...CIGS WILL LIFT AND BECOME
MVFR...BUT PERSIST THROUGH THE END OF THE TAF PERIOD. OTHERWISE...
SOUTHEASTERLY WINDS THIS MORNING WILL REMAIN AROUND 10KTS THROUGH
27/23Z...BEFORE WINDS SLACKEN AND BECOME MORE VARIABLE THIS
EVENING.
&&
.PREV DISCUSSION... /ISSUED 243 AM CST THU DEC 27 2012/
SHORT TERM...THE MAIN ISSUE TO DEAL WITH IS TODAY/S LIGHT SNOW
EVENT.
WATER VAPOR AND INFRARED SATELLITE IMAGERY SUGGEST THE UPPER LEVEL
CIRCULATION SET TO IMPACT OUR AREA IS CENTERED IN THE TRI-STATE
CONFLUENCE OF WY/CO/NE. SPOKE OF ENERGY ALONG WITH WARM ADVECTION
PUSHING THROUGH THE FORECAST AT THIS TIME. RETURNS FROM NEARBY
RADARS SUGGEST PRECIPITATION IS DEVELOPING ALOFT IN THIS WARM
ADVECTION. NOTHING HAS REPORTEDLY MADE IT TO THE GROUND WITH DRY
AIR IN LOWER LEVELS OF THE ATMOSPHERE. THAT ALL SHOULD CHANGE
EARLY THIS MORNING...SAY AROUND DAWN...WITH LIGHT SNOWFALL STARTING
TO REACH THE SURFACE. SHORT TERM MODEL DATA /HRRR AND WRF/ POINT
TOWARD A BAND OF SNOW DEVELOPING IN THE VICINITY OF HIGHWAY 281
NAM QUICKLY LIFTING NORTH/NORTHEAST. THESE FINER DETAILS FIT WITH
THE NAM/GFS/SREF OUTPUT...WHICH EVENTUALLY PUT THE GREATEST
PRECIPITATION IN NORTHEAST NEBRASKA OF ABOUT 0.30". MEANWHILE...
THE NORTH/EAST FORECAST AREA MAY PICK UP A TENTH OR TWO OF LIQUID
EQUIVALENT MOISTURE...EQUATING INTO 1 TO 2 INCHES...MAYBE LOCALLY
3 INCHES OF SNOW. THE AREA AT MOST RISK FOR 3 INCHES...AND IT MAY
NOT BE THAT MUCH RISK...WOULD BE NORTHERN NANCE COUNTY...OR NORTHEAST
GREELEY COUNTY. THE VAST MAJORITY OF OUR NEBRASKA FORECAST IS IN
THE 1 TO 2 INCH RANGE...WITH LESS THAN 1 INCH IN NORTHERN KANSAS.
AT THIS TIME...WITH LIMITED WIND INFLUENCES...AND ONLY A SMALL PART
OF THE FORECAST AREA IN LINE FOR MARGINAL ADVISORY LEVEL SNOW
AMOUNTS...WILL NOT ISSUE ANY HEADLINES. IN FACT...IF YOU BUY INTO
THE 05Z HRRR OUTPUT...ONLY THE FAR NORTHEAST FORECAST AREA WOULD
CATCH 1 TO 2 INCHES OF SNOW...AND THE REST OF THE AREA AN INCH OR
LESS. AT THIS POINT...THERE SEEMS TO BE ENOUGH REASON NOT TO ISSUE
ANY ADVISORIES FOR THIS EVENT.
SHOULD MENTION...NAM SOUNDINGS IN THE SOUTHEAST PART OF THE FORECAST
AREA...ALONG WITH FUZZY NATURE OF PRECIPITATION OUTLOOK...SUGGEST A
BIT OF FREEZING DRIZZLE COULD DEVELOP DURING THE EVENING HOURS. LIFT
IS THE QUESTION...MEANING IS THERE ENOUGH? THINK THERE COULD BE A
COUPLE OF HOURS OF FREEZING DRIZZLE TYPE PRECIPITATION IN THIS AREA
AND HAVE ADDED THAT TO THE FORECAST GRIDS. NOT A HUGE DEAL...AND MAY
NOT MATERIALIZE...BUT WOULDN/T BE SHOCKED IF IT DID PAN OUT.
ON FRIDAY...THE MEANDERING NATURE OF THE UPPER LEVEL LOW TO THE
SOUTHEAST WILL KEEP CLOUDS AROUND FOR A GOOD PART OF THE DAY. FAR
EASTERN FORECAST AREA MAY EVEN SEE A LINGERING FLURRY EARLY IN THE
MORNING. ASIDE FROM THAT...NORTHWEST WINDS WILL DEVELOP...AND MAY
EVEN TURN SNEAKY BREEZY IF CLEARING DEVELOPS MORE RAPIDLY. FRIDAY
IS STILL A PART OF THE CURRENT COLD SPELL WITH HIGHS STRUGGLING FOR
ABOUT 20 MOST AREAS. THAT ALL STARTS TO CHANGE FRIDAY NIGHT...AS
DOWN-SLOPING WESTERLY WINDS SET UP AND LASTS INTO THE DAY SATURDAY.
THIS WILL RESULT IN SATURDAY BEING MUCH WARMER...RELATIVE TO RECENT
DAYS...WITH HIGHS IN THE UPPER 20S AND LOWER 30S AND PLENTY OF
SUNSHINE. THAT WON/T NECESSARILY MELT A WHOLE LOT...AND ITS STILL
BELOW NORMAL SOME 5 TO 7 DEGREES...BUT ITS AT LEAST A START.
LONG TERM...STARTING SUNDAY MORNING...SUNDAY IS SHAPING UP TO BE
THE WARMEST DAY IN JUST OVER A WEEK AS THE COMBINATION OF WARMER AIR
SURGING NORTHWARD AHEAD OF AN APPROACHING LOW LEVEL TROUGH/FRONT AND
MOSTLY SUNNY SKIES UNDER THE INFLUENCE OF A BUILDING UPPER LEVEL
RIDGE...WILL RESULT IN A RETURN TO NEAR SEASONAL TEMPERATURES FOR
THE END OF DECEMBER. AS A RESULT...EXPECT TO SEE AFTERNOON
TEMPERATURES ACROSS SOUTH CENTRAL NEBRASKA APPROACH THE FREEZING
MARK...WITH UPPER 30S TO NEAR 40 DEGREES CURRENTLY FORECAST FOR
PORTIONS OF NORTH CENTRAL KANSAS. WHILE THIS LIKELY WILL NOT BE WARM
ENOUGH TO RESULT IN ANY SIGNIFICANT MELTING OF SNOW/ICE ON THE
GROUND...IT WILL LIKELY BE THE FIRST DAY SINCE DECEMBER 22ND THAT
TEMPERATURES WILL CLIMB ABOVE THE FREEZING MARK ACROSS THE MAJORITY
OF THE FORECAST AREA. THIS BRIEF WARM UP...HOWEVER...IS EXPECTED TO
BE FAIRLY SHORT LIVED...AS GLOBAL MODELS ARE INDICATING COOLER AIR
BEHIND THE APPROACHING TROUGH/FRONT...WHICH WILL BEGIN TO FILTER IN
ACROSS THE LOCAL AREA TO START THE NEW WORK WEEK. AS A
RESULT...EXPECT A RETURN TO SUBFREEZING AFTERNOON TEMPERATURES
MONDAY AFTERNOON WITH LITTLE EVIDENCE FOR ENOUGH LOW LEVEL MOISTURE
OR FORCING TO JUSTIFY ANYTHING OTHER THAN AN INCREASE IN CLOUDS
ACROSS THE LOCAL AREA MONDAY.
THEREAFTER...THE GLOBAL MODELS BEGIN TO DIVERGE SOME WITH THEIR
HANDLING OF AN UPPER LEVEL LOW ACROSS THE DESERT SOUTHWEST...WITH
THE GFS MAINTAINING A MUCH MORE PROGRESSIVE FLOW PATTERN THAN THE
EC...WHICH HAS BEEN TRYING TO CUT OFF THE UPPER LEVEL LOW ACROSS
NORTHERN MEXICO. HOWEVER...IN BOTH SCENARIOS...THE NORTHERN JET IS
FORECAST TO STEER AN UPPER LEVEL DISTURBANCE ACROSS NEBRASKA TUESDAY
NIGHT/WEDNESDAY...WHICH ONCE AGAIN IS EXPECTED TO HAVE A LACK IN
APPRECIABLE LOW LEVEL MOISTURE...WITH LITTLE MORE THAN A FEW HIGH
CLOUDS AND A CONTINUATION OF SUB FREEZING TEMPERATURES EXPECTED TO
PERSIST AS A RESULT. JUST BEYOND THE CURRENT SCOPE OF THE
FORECAST...THERE ARE SOME INDICATIONS THAT ANOTHER UPPER LEVEL RIDGE
OF HIGH PRESSURE WILL BUILD ACROSS THE CENTRAL PLAINS IN CONCERT
WITH A MORE SIGNIFICANT DOWN-SLOPING LOW LEVEL FLOW...WHICH MAY
RESULT IN TEMPERATURES WARMING ABOVE CLIMO TOWARDS THE END OF NEXT
WEEK.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
542 AM CST THU DEC 27 2012
.AVIATION...
LIGHT SNOW IS EXPECTED TO CONTINUE NORTH AND WEST OF AN
ANW-TIF-MHN-OGA LINE THROUGH 21Z WITH THE HEAVIEST FROM 14-18Z.
CEILINGS BELOW 3000 FEET AGL ARE LIKELY WITH A FAIRLY STRONG
PROBABILITY OF 1000-2000 FEET AGL. IN ADDITION...WIDESPREAD
VISIBILITY BELOW 3SM CAN BE EXPECTED IN THE HEAVIER SNOW WITH LESS
THAN 1SM POSSIBLE. LOW CEILING AND VISIBILITY MAY CONTINUE UNTIL AT
LEAST THIS EVENING 03Z...ESPECIALLY IN NORTH CENTRAL NEBRASKA.
&&
.PREV DISCUSSION... /ISSUED 354 AM CST THU DEC 27 2012/
SHORT TERM...TODAY THROUGH SATURDAY NIGHT
FORECAST CONCERNS THROUGH THIS PERIOD ARE SNOWFALL CHANCES AND
AMOUNTS FOR TODAY AND TONIGHT...THEN TEMPERATURES INTO THE
WEEKEND.
AT 08Z...WATER VAPOR IMAGERY SHOWED THE STRONG LOW PRESSURE SYSTEM
IMPACTING THE EAST COAST CENTERED OVER EASTERN VIRGINIA. RIDGING
WAS SITUATED OVER THE MISSISSIPPI RIVER VALLEY AS A FAIRLY LARGE
TROUGH COVERING THE WESTERN HALF OF THE CONUS. COMING OUT OF THE
TROUGH WAS AN UPPER LOW OVER EASTERN WYOMING...WHILE A PV ANOMALY
WAS SEEN OVER EASTERN COLORADO MOVING TOWARDS WESTERN NEBRASKA.
LOCALLY...RADAR ECHOES SPANNED ACROSS THE EASTERN PANHANDLE INTO
NORTHWEST NEBRASKA...WITH MORE CONVECTIVE LOOKING ECHOES OVER
CENTRAL NEBRASKA. NO PRECIPITATION WAS BEING REPORTED WITH THE
EASTERN ACTIVITY WHILE KAIA AND KSNY IN THE PANHANDLE HAD REPORTED
LIGHT SNOW BEING JUST OUTSIDE OF THE MAIN SNOW BAND. MODELS WOULD
INDICATE THE 700MB LOW OVER THE WESTERN PANHANDLE. THERE WAS A
GOOD MOISTURE FEED JUST TO THE EAST OF THE LOW WHICH HAD ITS
PRIMARY FOCUS INTO NORTHWEST NEBRASKA. THE RAP MODEL ALSO WAS
INDICATING SOME FRONTOGENETICAL FORCING AT 700 TO 600MB IN THIS SAME
AREA...WHICH WOULD FIT WITH WHAT IS ONGOING.
AS THE MORNING PROGRESSES...THE UPPER LOW OVER WYOMING WILL SHIFT
EAST INTO NORTH CENTRAL NEBRASKA AROUND MID-DAY THEN CONTINUE EAST
ALONG THE SOUTH DAKOTA/NEBRASKA BORDER INTO TONIGHT. ISENTROPIC
SURFACES FROM ROUGHLY 275K TO 290K ALL SHOWING DECENT LIFT AS WELL
AS MOISTURE TRANSPORT THROUGH THE MORNING /MAINLY OVER NORTHERN
NEBRASKA/...WHICH THEN SHIFTS EAST THIS AFTERNOON. HAVE ADJUSTED
PRECIPITATION CHANCES IN THIS FORECAST TO INCLUDE THE HIGHEST
CHANCES OVER THE PANHANDLE AND NORTHWEST NEBRASKA THIS
MORNING...THEN INTO NORTH CENTRAL NEBRASKA THIS AFTERNOON AS THE
WHOLE SYSTEM MOVES EAST. CONTINUED THE CHANCES OVER SOUTHWEST
NEBRASKA TODAY...BUT CONFIDENCE IS MUCH LESS IN THESE AREAS AND
DID BACK OFF ON CHANCES A BIT. REASONING FOR THIS IS THAT THIS
AREA WILL BE IN A FAVORABLE LOCATION FOR DRY AIR TO COME INTO THE
SYSTEM AROUND THE UPPER LOW...ALSO THE PV ANOMALY OVER COLORADO
HAS GOOD DARKENING IN THE WATER VAPOR IMAGERY INDICATING GOOD DRY
AIR ASSOCIATED WITH IT. AS THIS MOVES INTO SOUTHWEST NEBRASKA...IT
SHOULD LIMIT THE SNOWFALL. WILL PROBABLY SEE SOME SNOW IN THESE
AREAS THROUGH THE DAY...BUT BELIEVE IT WILL BE QUITE LIGHT AND
WILL NOT LAST LONG SO VERY LITTLE IF ANY ACCUMULATION IS EXPECTED.
IF IN FACT THIS OCCURS...THE FORECAST WILL LIKELY NEED TO BE
UPDATED TO REFLECT THE LOWER CHANCES FOR MEASURABLE SNOWFALL IN
THESE AREAS.
THE SYSTEM WILL NOT BE REAL FAST MOVING OUT OF THE LOCAL
AREA...WHICH WILL KEEP SNOW FALLING ACROSS NORTH CENTRAL NEBRASKA
TONIGHT BEFORE EXITING COMPLETELY ON FRIDAY. THERE HAS BEEN GOOD
MODEL AGREEMENT WITH KEEPING THE HIGHER SNOWFALL AMOUNTS JUST EAST
OF THE FORECAST AREA...MAINLY ALONG AND EAST OF HIGHWAY 14.
SOUNDINGS CONTINUE TO SHOW THE ENTIRE SATURATED LAYER /SURFACE
THROUGH 600MB/ IN THE DENTRITIC GROWTH ZONE...SO USED HIGH SNOW
RATIOS VARYING FROM 18:1 TO 23:1. EVEN WITH THIS...STORM TOTAL
SNOW AMOUNTS ACROSS HOLT AND BOYD COUNTIES ONLY SHOWING 2 TO 3
INCHES WITH A FEW LOCALIZED AREAS ABOVE 3 INCHES. GOING EAST OF
THE AREA AMOUNTS IN EXCESS OF 3 INCHES ARE LIKELY. WINDS SHOULD BE
FAIRLY LIGHT TODAY UNDER 15 MPH SO EVEN WITH THE HIGH SNOW
RATIOS GIVING HIGHER SNOW AMOUNTS DON/T FEEL THE IMPACTS WILL BE
HIGH SO WILL NOT PUT OUT AN ADVISORY FOR TODAY AND TONIGHT.
COLD AIR WILL REMAIN IN PLACE OVER THE FORECAST AREA TODAY...AND
WITH THE CLOUD COVER DON/T EXPECT HIGHS TO GET OUT OF THE TEENS.
TONIGHT AND FRIDAY...THE PRIMARY TROUGH WILL EXTEND FROM THE NORTHERN
PLANS THROUGH THE FOUR CORNERS. MEANWHILE...SEVERAL WEAK IMPULSES
OF SHORTWAVE ENERGY WILL QUICKLY PUSH SOUTH OUT OF CANADA INTO THE
CENTRAL PLAINS. THIS SHOULD KEEP AT LEAST SOME HIGH CLOUDS...BUT
MAY NOT BE TOO THICK. DID DROP LOWS ACROSS THE WESTERN PARTS OF
THE FORECAST AREA NEAR ZERO OR SLIGHTLY BELOW ZERO. IF CLOUDS
CLEAR...COULD CERTAINLY BE TOO WARM.
THE TROUGH DOES MOVE EAST INTO THE MISSISSIPPI RIVER VALLEY FRIDAY
NIGHT AND SATURDAY ALLOWING RIDGING TO START TO BUILD IN FOR THE
WEEKEND. THIS WILL BE THE START TO A SLOW WARMING TREND INTO NEXT
WEEK. NOT LOOKING FOR TEMPERATURES TO WARM DRAMATICALLY AS
SATURDAY HAS HIGHS NEAR THE FREEZING POINT. AREAS WITH SNOW COVER
WILL SEE A GREATER IMPACT IN TEMPERATURES SO IT IS LIKELY THAT
THERE WILL BE ADJUSTMENTS AFTER THE SNOW FIELD IS SAMPLED AFTER
TONIGHT.
LONG TERM...SUNDAY THROUGH WEDNESDAY
THIS PERIOD BEGINS WITH RIDGING ACROSS THE PLAINS...HOWEVER THERE
IS GOOD CONSENSUS FROM THE MODEL OUTPUT BRINGING THE NEXT STRONG
TROUGH INTO THE WEST COAST ON SUNDAY. ALSO...SEVERAL STRONG
SHORTWAVE TROUGHS ARE BEING SHOWN IN THE NORTHERN STREAM WHICH
COULD COME SOUTH FAR ENOUGH TO KEEP THE RIDGE FROM BUILDING TOO
FAR NORTH. THIS WILL KEEP TEMPERATURES FROM MODERATING TOO MUCH
THROUGH THE FIRST PART OF NEXT WEEK. THE FIRST OF THESE SYSTEMS
COMES THROUGH SUNDAY NIGHT...WHICH SHOULDN/T HAVE ANY OTHER IMPACT
BUT TO BRING SOME COOLER AIR SOUTH INTO NEBRASKA. FOR MONDAY AND
BEYOND...THE MODELS BEGIN TO DIVERGE WITH THE EASTERN MOVEMENT OF
THE WEST COAST TROUGH. THE ECMWF IS SLOWER...WHICH THEN ALLOWS A
STRONG NORTHERN STREAM SYSTEM TO PENETRATE INTO NEBRASKA TUESDAY
NIGHT. THE GFS IS QUICKER AND KEEPS THIS SYSTEM UP OVER MINNESOTA
AND THE GREAT LAKES. EITHER WAY...MOISTURE LOOKS TO BE HELD TO THE
THE MAIN UPPER LOW WHICH STAYS WELL SOUTH SO NO FURTHER
PRECIPITATION CHANCES ARE IN THE FORECAST BEYOND FRIDAY MORNING.
HYDROLOGY...
ICE JAMS ARE LIKELY TO CONTINUE AT VARIOUS LOCATIONS IN CENTRAL
AND WESTERN NEBRASKA. EXCEPT FOR STRETCHES ALONG THE NORTH PLATTE
RIVER...THERE ARE NO INDICATIONS OF FLOODING. BE AWARE THAT THE
FORMATION AND BREAK-UP OF ICE JAMS ARE NOTORIOUSLY DIFFICULT TO
FORECAST...SO RIVERS AND STREAMS IN THE AREA MAY RISE AND FALL
ERRATICALLY. WE DO HAVE FAIRLY HIGH CONFIDENCE THAT...WITH
TEMPERATURES MODERATING SOME...THE LEVELS ARE NOT LIKELY TO HAVE
NEW SHARP RISES ABOVE CURRENT LEVELS.
THE NORTH PLATTE RIVER AT LEWELLEN CONTINUES TO FALL
SLOWLY...POSSIBLY BECAUSE THE RIVER HAS BECOME COMPLETELY FROZEN
AND THE ICE IS NO LONGER BEING CARRIED TOWARD THE INLET OF LAKE
MCCONAUGHY. AT THE NORTH PLATTE GAGE...THE LEVEL CONTINUES ABOVE
FLOOD STAGE AND IS LIKELY TO CONTINUE FOR AT LEAST THIS WEEKEND.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM/EXTENDED...BROOKS
AVIATION/HYDROLOGY...SPRINGER
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
525 AM CST THU DEC 27 2012
.AVIATION...
12Z TAFS FOR KOFK...KOMA AND KLNK.
ONE BAND OF SNOW MOVING ACROSS EASTERN NEBRASKA THIS MORNING WILL
BRING LOWERING CIGS AND SNOW CHANCES TO TAF SITES. KOFK SHOULD BE
ESPECIALLY IMPACTED BY THIS FIRST ROUND AND TEMPO IFR CONDITIONS
WERE FORECAST THERE. A LULL IS THEN EXPECTED LATER THIS MORNING
INTO THIS AFTERNOON AT KOMA/KLNK...ALTHOUGH SNOW SHOULD PERSIST
AT KOFK. A PERIOD OF FREEZING DRIZZLE WAS MENTIONED AT KOMA/KLNK
LATE THIS AFTERNOON OR EARLY THIS EVENING AS LOW LEVELS SATURATE
BUT LIFT/MOISTURE NOT ESPECIALLY SUPPORTIVE FOR SNOW. CONFIDENCE
IN VSBY/PRECIP EVOLUTION...HOWEVER...NOT VERY HIGH AND ADJUSTMENTS
IN FORECAST LIKELY.
CHERMOK
&&
.PREV DISCUSSION... /ISSUED 302 AM CST THU DEC 27 2012/
DISCUSSION...
..SNOW AMOUNTS AND CHANCES FOR FREEZING DRIZZLE THE MAIN
CONCERNS...
FOR THIS FORECAST THE MAIN FEATURE OF INTEREST WILL BE THE POTENT
SHORTWAVE THAT IS CURRENTLY SPINNING ALONG THE WYOMING-COLORADO
BORDER PER WATER VAPOR LOOP AND THE PRECIPITATION IT WILL PRODUCE
TODAY AND FRIDAY. THE MORE THIS SYSTEM DEVELOPS THE MORE
IMPRESSIVE IT APPEARS TO BE...ESPECIALLY FOR NORTHEAST NEBRASKA.
500 MB HEIGHT FALLS ON THE 00Z RAOBS WERE 100-120 METERS IN THE
BASE OF THE TROF...WITH DENVER SHOWING A 130 METER FALL AT 300 MB.
150 KNOT JET STREAK WAS NOTED AT 25O MB OVER ARIZONA. REGIONAL
RADAR MOSAIC SHOWS SNOW RAPIDLY DEVELOPING/EXPANDING FROM WESTERN
KANSAS INTO WESTERN AND CENTRAL NEBRASKA IN RESPONSE TO THE
SYSTEMS VERTICAL MOTION AND MOISTURE AROUND 850 MB AS SEEN ON
DODGE CITY AND NORTH PLATTE SOUNDINGS. 08Z SURFACE ANALYSIS SHOWED
EARLY STAGES OF INVERTED TROF TAKING SHAPE WITH 1003MB PRESSURES
OBSERVED IN SOUTHEAST COLORADO.
THE DODGE CITY AND NORTH PLATTE SOUNDINGS DID HAVE A FEW DRY
LAYERS AS WELL...AND THESE DRY LAYERS DO COMPLICATE THE
PRECIPITATION FORECAST. GENERALLY THE NAM/GFS/RAP ARE IN DECENT
AGREEMENT ON THE PRECIPITATION FORECAST AND THE MOIST AND DRY
LAYERS. HOWEVER THERE IS CONCERN FOR A LIGHT FREEZING DRIZZLE
SCENARIO MAINLY IN THE SOUTHERN HALF OF THE FORECAST AREA DUE TO A
LOW LEVEL SATURATED LAYER THAT IS WARMER THAN -10C AND THEREFORE
WOULD PRIMARILY CONTAIN SUPERCOOLED DRIZZLE AS OPPOSED TO
SNOWFLAKES. THE MODELS SHOW LITTLE OR NO QPF OVER SOUTHEAST
NEBRASKA THROUGH 12Z FRIDAY...HOWEVER THE MODELS OFTEN POORLY HANDLE
THESE VERY LIGHT ICING EVENTS BECAUSE THE QPF IS QUITE LIGHT BUT
ALSO BECAUSE THE LAYERS ARE SHALLOW. THE FORECAST SOUNDINGS FROM
THE NAM AND ESPECIALLY THE RAP SUPPORT AT LEAST SOME LIGHT
FREEZING DRIZZLE MAINLY ALONG AND SOUTH OF INTERSTATE 80 AT
VARIOUS TIMES FROM LATE THIS AFTERNOON INTO TONIGHT...THEREFORE
WE HAVE ADDED PATCHY FREEZING DRIZZLE...OR AREAS OF FREEZING
DRIZZLE...TO THE SNOW CHANCES IN THOSE LOCATIONS. CONFIDENCE IN
THIS LIGHT ICING SCENARIO IS NOT HIGH ENOUGH TO ISSUE A WINTER
WEATHER ADVISORY FOR THE ABOVE MENTIONED AREAS. HOWEVER IF NEW
OBSERVATIONS AND MODEL RUNS SUGGEST A HIGHER LIKELIHOOD OF
FREEZING DRIZZLE AN ADVISORY MAY BE CONSIDERED LATER TODAY.
OTHERWISE THE TRACK OF THE LOW FAVORS THE HEAVIER SNOWS TO FALL IN
NORTHEAST NEBRASKA WHERE THE GOING WINTER WEATHER ADVISORY IS AT.
WE DID ADD ONE MORE TIER OF COUNTIES TO THE ADVISORY INCLUDING
ALBION AND NORFOLK. THIS SYSTEM IS UNIQUE IN THAT IT HAS A VERY
DEEP SATURATED LAYER THAT IS IN THE DENDRITIC GROWTH ZONE...AROUND
250 MB OR ABOUT 10000 FEET DEEP...YIELDING SNOW-LIQUID RATIOS AS
HIGH AS 20-1. BECAUSE OF THIS WE ALSO INCREASED SNOW AMOUNTS IN
NORTHEAST NEBRASKA ABOUT 1 MORE INCH. FORTUNATELY THERE WILL NOT
BE A LOT OF WIND WITH THIS SYSTEM SO LITTLE BLOWING AND DRIFTING
IS EXPECTED. SOME LOCATIONS IN THE ADVISORY AREA SHOULD SEE 4-5
INCHES OF DRY/FLUFFY SNOW STARTING TODAY AND ENDING FRIDAY
MORNING.
CONFIDENCE IN THE EXACT SNOW AMOUNTS IS MUCH LOWER TO THE SOUTH
OF THE ADVISORY AREA...MAINLY FROM THE LINCOLN TO OMAHA METRO
AREAS. HOWEVER...THERE IS LITTLE SUPPORT FOR MORE THAN 2 INCHES
GIVEN THE DRY LAYERS THAT WILL NEED TO BE SATURATED AND THE
WEAKER FORCING JUST SOUTH OF THE 700 MB LOW TRACK. CURRENTLY WE
ARE KEEPING THE 1-2 INCH AMOUNTS FOR LINCOLN-OMAHA AND THIS LOOKS
REASONABLE BY NOON FRIDAY WHEN ANY LIGHT SNOW ON THE BACK SIDE OF
THE LOW FINALLY ENDS. STARTED THE CHANCES FOR SNOW A BIT LATER
EAST OF A LINE FROM LINCOLN TO FREMONT...MAINLY CLOSER TO 18Z
TODAY...PRIMARILY DUE TO THE TIME IT WILL TAKE TO SATURATE THE
DRY LOW LEVELS IN THAT AREA.
TEMPERATURE AND WIND FORECASTS WERE ONLY SLIGHTLY ADJUSTED AS THE
PATTERN REMAINS FAIRLY COLD BUT DRY AFTER FRIDAY.
NIETFELD
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER WEATHER ADVISORY FROM NOON TODAY TO 6 AM CST FRIDAY FOR
NEZ011-012-015>018-030>033.
IA...WINTER WEATHER ADVISORY FROM NOON TODAY TO 6 AM CST FRIDAY FOR
IAZ043.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTH PLATTE NE
354 AM CST THU DEC 27 2012
.SHORT TERM...TODAY THROUGH SATURDAY NIGHT
FORECAST CONCERNS THROUGH THIS PERIOD ARE SNOWFALL CHANCES AND
AMOUNTS FOR TODAY AND TONIGHT...THEN TEMPERATURES INTO THE
WEEKEND.
AT 08Z...WATER VAPOR IMAGERY SHOWED THE STRONG LOW PRESSURE SYSTEM
IMPACTING THE EAST COAST CENTERED OVER EASTERN VIRGINIA. RIDGING
WAS SITUATED OVER THE MISSISSIPPI RIVER VALLEY AS A FAIRLY LARGE
TROUGH COVERING THE WESTERN HALF OF THE CONUS. COMING OUT OF THE
TROUGH WAS AN UPPER LOW OVER EASTERN WYOMING...WHILE A PV ANOMALY
WAS SEEN OVER EASTERN COLORADO MOVING TOWARDS WESTERN NEBRASKA.
LOCALLY...RADAR ECHOES SPANNED ACROSS THE EASTERN PANHANDLE INTO
NORTHWEST NEBRASKA...WITH MORE CONVECTIVE LOOKING ECHOES OVER
CENTRAL NEBRASKA. NO PRECIPITATION WAS BEING REPORTED WITH THE
EASTERN ACTIVITY WHILE KAIA AND KSNY IN THE PANHANDLE HAD REPORTED
LIGHT SNOW BEING JUST OUTSIDE OF THE MAIN SNOW BAND. MODELS WOULD
INDICATE THE 700MB LOW OVER THE WESTERN PANHANDLE. THERE WAS A
GOOD MOISTURE FEED JUST TO THE EAST OF THE LOW WHICH HAD ITS
PRIMARY FOCUS INTO NORTHWEST NEBRASKA. THE RAP MODEL ALSO WAS
INDICATING SOME FRONTOGENETICAL FORCING AT 700 TO 600MB IN THIS SAME
AREA...WHICH WOULD FIT WITH WHAT IS ONGOING.
AS THE MORNING PROGRESSES...THE UPPER LOW OVER WYOMING WILL SHIFT
EAST INTO NORTH CENTRAL NEBRASKA AROUND MID-DAY THEN CONTINUE EAST
ALONG THE SOUTH DAKOTA/NEBRASKA BORDER INTO TONIGHT. ISENTROPIC
SURFACES FROM ROUGHLY 275K TO 290K ALL SHOWING DECENT LIFT AS WELL
AS MOISTURE TRANSPORT THROUGH THE MORNING /MAINLY OVER NORTHERN
NEBRASKA/...WHICH THEN SHIFTS EAST THIS AFTERNOON. HAVE ADJUSTED
PRECIPITATION CHANCES IN THIS FORECAST TO INCLUDE THE HIGHEST
CHANCES OVER THE PANHANDLE AND NORTHWEST NEBRASKA THIS
MORNING...THEN INTO NORTH CENTRAL NEBRASKA THIS AFTERNOON AS THE
WHOLE SYSTEM MOVES EAST. CONTINUED THE CHANCES OVER SOUTHWEST
NEBRASKA TODAY...BUT CONFIDENCE IS MUCH LESS IN THESE AREAS AND
DID BACK OFF ON CHANCES A BIT. REASONING FOR THIS IS THAT THIS
AREA WILL BE IN A FAVORABLE LOCATION FOR DRY AIR TO COME INTO THE
SYSTEM AROUND THE UPPER LOW...ALSO THE PV ANOMALY OVER COLORADO
HAS GOOD DARKENING IN THE WATER VAPOR IMAGERY INDICATING GOOD DRY
AIR ASSOCIATED WITH IT. AS THIS MOVES INTO SOUTHWEST NEBRASKA...IT
SHOULD LIMIT THE SNOWFALL. WILL PROBABLY SEE SOME SNOW IN THESE
AREAS THROUGH THE DAY...BUT BELIEVE IT WILL BE QUITE LIGHT AND
WILL NOT LAST LONG SO VERY LITTLE IF ANY ACCUMULATION IS EXPECTED.
IF IN FACT THIS OCCURS...THE FORECAST WILL LIKELY NEED TO BE
UPDATED TO REFLECT THE LOWER CHANCES FOR MEASURABLE SNOWFALL IN
THESE AREAS.
THE SYSTEM WILL NOT BE REAL FAST MOVING OUT OF THE LOCAL
AREA...WHICH WILL KEEP SNOW FALLING ACROSS NORTH CENTRAL NEBRASKA
TONIGHT BEFORE EXITING COMPLETELY ON FRIDAY. THERE HAS BEEN GOOD
MODEL AGREEMENT WITH KEEPING THE HIGHER SNOWFALL AMOUNTS JUST EAST
OF THE FORECAST AREA...MAINLY ALONG AND EAST OF HIGHWAY 14.
SOUNDINGS CONTINUE TO SHOW THE ENTIRE SATURATED LAYER /SURFACE
THROUGH 600MB/ IN THE DENTRITIC GROWTH ZONE...SO USED HIGH SNOW
RATIOS VARYING FROM 18:1 TO 23:1. EVEN WITH THIS...STORM TOTAL
SNOW AMOUNTS ACROSS HOLT AND BOYD COUNTIES ONLY SHOWING 2 TO 3
INCHES WITH A FEW LOCALIZED AREAS ABOVE 3 INCHES. GOING EAST OF
THE AREA AMOUNTS IN EXCESS OF 3 INCHES ARE LIKELY. WINDS SHOULD BE
FAIRLY LIGHT TODAY UNDER 15 MPH SO EVEN WITH THE HIGH SNOW
RATIOS GIVING HIGHER SNOW AMOUNTS DON/T FEEL THE IMPACTS WILL BE
HIGH SO WILL NOT PUT OUT AN ADVISORY FOR TODAY AND TONIGHT.
COLD AIR WILL REMAIN IN PLACE OVER THE FORECAST AREA TODAY...AND
WITH THE CLOUD COVER DON/T EXPECT HIGHS TO GET OUT OF THE TEENS.
TONIGHT AND FRIDAY...THE PRIMARY TROUGH WILL EXTEND FROM THE NORTHERN
PLANS THROUGH THE FOUR CORNERS. MEANWHILE...SEVERAL WEAK IMPULSES
OF SHORTWAVE ENERGY WILL QUICKLY PUSH SOUTH OUT OF CANADA INTO THE
CENTRAL PLAINS. THIS SHOULD KEEP AT LEAST SOME HIGH CLOUDS...BUT
MAY NOT BE TOO THICK. DID DROP LOWS ACROSS THE WESTERN PARTS OF
THE FORECAST AREA NEAR ZERO OR SLIGHTLY BELOW ZERO. IF CLOUDS
CLEAR...COULD CERTAINLY BE TOO WARM.
THE TROUGH DOES MOVE EAST INTO THE MISSISSIPPI RIVER VALLEY FRIDAY
NIGHT AND SATURDAY ALLOWING RIDGING TO START TO BUILD IN FOR THE
WEEKEND. THIS WILL BE THE START TO A SLOW WARMING TREND INTO NEXT
WEEK. NOT LOOKING FOR TEMPERATURES TO WARM DRAMATICALLY AS
SATURDAY HAS HIGHS NEAR THE FREEZING POINT. AREAS WITH SNOW COVER
WILL SEE A GREATER IMPACT IN TEMPERATURES SO IT IS LIKELY THAT
THERE WILL BE ADJUSTMENTS AFTER THE SNOW FIELD IS SAMPLED AFTER
TONIGHT.
.LONG TERM...SUNDAY THROUGH WEDNESDAY
THIS PERIOD BEGINS WITH RIDGING ACROSS THE PLAINS...HOWEVER THERE
IS GOOD CONSENSUS FROM THE MODEL OUTPUT BRINGING THE NEXT STRONG
TROUGH INTO THE WEST COAST ON SUNDAY. ALSO...SEVERAL STRONG
SHORTWAVE TROUGHS ARE BEING SHOWN IN THE NORTHERN STREAM WHICH
COULD COME SOUTH FAR ENOUGH TO KEEP THE RIDGE FROM BUILDING TOO
FAR NORTH. THIS WILL KEEP TEMPERATURES FROM MODERATING TOO MUCH
THROUGH THE FIRST PART OF NEXT WEEK. THE FIRST OF THESE SYSTEMS
COMES THROUGH SUNDAY NIGHT...WHICH SHOULDN/T HAVE ANY OTHER IMPACT
BUT TO BRING SOME COOLER AIR SOUTH INTO NEBRASKA. FOR MONDAY AND
BEYOND...THE MODELS BEGIN TO DIVERGE WITH THE EASTERN MOVEMENT OF
THE WEST COAST TROUGH. THE ECMWF IS SLOWER...WHICH THEN ALLOWS A
STRONG NORTHERN STREAM SYSTEM TO PENETRATE INTO NEBRASKA TUESDAY
NIGHT. THE GFS IS QUICKER AND KEEPS THIS SYSTEM UP OVER MINNESOTA
AND THE GREAT LAKES. EITHER WAY...MOISTURE LOOKS TO BE HELD TO THE
THE MAIN UPPER LOW WHICH STAYS WELL SOUTH SO NO FURTHER
PRECIPITATION CHANCES ARE IN THE FORECAST BEYOND FRIDAY MORNING.
&&
.AVIATION...
LIGHT SNOW IS EXPECTED TO CONTINUE NORTH AND WEST OF AN
ANW-TIF-MHN-OGA LINE THROUGH 21Z WITH THE HEAVIEST FROM 10-12Z.
CEILINGS BELOW 3000 FEET AGL ARE LIKELY WITH A FAIRLY STRONG
PROBABILITY OF 1000-2000 FEET AGL. IN ADDITION...WIDESPREAD
VISIBILITY BELOW 3SM IS LIKELY IN LIGHT SNOW UNTIL ABOUT 12Z WITH
LESS THAN 1SM POSSIBLE. LOW CEILING AND VISIBILITY MAY CONTINUE
UNTIL AT LEAST THIS EVENING 03Z...ESPECIALLY IN NORTH CENTRAL AND
NORTHWEST NEBRASKA.
&&
.HYDROLOGY...
ICE JAMS ARE LIKELY TO CONTINUE AT VARIOUS LOCATIONS IN CENTRAL
AND WESTERN NEBRASKA. EXCEPT FOR STRETCHES ALONG THE NORTH PLATTE
RIVER...THERE ARE NO INDICATIONS OF FLOODING. BE AWARE THAT THE
FORMATION AND BREAK-UP OF ICE JAMS ARE NOTORIOUSLY DIFFICULT TO
FORECAST...SO RIVERS AND STREAMS IN THE AREA MAY RISE AND FALL
ERRATICALLY. WE DO HAVE FAIRLY HIGH CONFIDENCE THAT...WITH
TEMPERATURES MODERATING SOME...THE LEVELS ARE NOT LIKELY TO HAVE
NEW SHARP RISES ABOVE CURRENT LEVELS.
THE NORTH PLATTE RIVER AT LEWELLEN CONTINUES TO FALL
SLOWLY...POSSIBLY BECAUSE THE RIVER HAS BECOME COMPLETELY FROZEN
AND THE ICE IS NO LONGER BEING CARRIED TOWARD THE INLET OF LAKE
MCCONAUGHY. AT THE NORTH PLATTE GAGE...THE LEVEL CONTINUES ABOVE
FLOOD STAGE AND IS LIKELY TO CONTINUE FOR AT LEAST THIS WEEKEND.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT/LONG TERM...BROOKS
AVIATION/HYDROLOGY...SPRINGER
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
302 AM CST THU DEC 27 2012
.DISCUSSION...
...SNOW AMOUNTS AND CHANCES FOR FREEZING DRIZZLE THE MAIN
CONCERNS...
FOR THIS FORECAST THE MAIN FEATURE OF INTEREST WILL BE THE POTENT
SHORTWAVE THAT IS CURRENTLY SPINNING ALONG THE WYOMING-COLORADO
BORDER PER WATER VAPOR LOOP AND THE PRECIPITATION IT WILL PRODUCE
TODAY AND FRIDAY. THE MORE THIS SYSTEM DEVELOPS THE MORE
IMPRESSIVE IT APPEARS TO BE...ESPECIALLY FOR NORTHEAST NEBRASKA.
500 MB HEIGHT FALLS ON THE 00Z RAOBS WERE 100-120 METERS IN THE
BASE OF THE TROF...WITH DENVER SHOWING A 130 METER FALL AT 300 MB.
150 KNOT JET STREAK WAS NOTED AT 25O MB OVER ARIZONA. REGIONAL
RADAR MOSAIC SHOWS SNOW RAPIDLY DEVELOPING/EXPANDING FROM WESTERN
KANSAS INTO WESTERN AND CENTRAL NEBRASKA IN RESPONSE TO THE
SYSTEMS VERTICAL MOTION AND MOISTURE AROUND 850 MB AS SEEN ON
DODGE CITY AND NORTH PLATTE SOUNDINGS. 08Z SURFACE ANALYSIS SHOWED
EARLY STAGES OF INVERTED TROF TAKING SHAPE WITH 1003MB PRESSURES
OBSERVED IN SOUTHEAST COLORADO.
THE DODGE CITY AND NORTH PLATTE SOUNDINGS DID HAVE A FEW DRY
LAYERS AS WELL...AND THESE DRY LAYERS DO COMPLICATE THE
PRECIPITATION FORECAST. GENERALLY THE NAM/GFS/RAP ARE IN DECENT
AGREEMENT ON THE PRECIPITATION FORECAST AND THE MOIST AND DRY
LAYERS. HOWEVER THERE IS CONCERN FOR A LIGHT FREEZING DRIZZLE
SCENARIO MAINLY IN THE SOUTHERN HALF OF THE FORECAST AREA DUE TO A
LOW LEVEL SATURATED LAYER THAT IS WARMER THAN -10C AND THEREFORE
WOULD PRIMARILY CONTAIN SUPERCOOLED DRIZZLE AS OPPOSED TO
SNOWFLAKES. THE MODELS SHOW LITTLE OR NO QPF OVER SOUTHEAST
NEBRASKA THROUGH 12Z FRIDAY...HOWEVER THE MODELS OFTEN POORLY HANDLE
THESE VERY LIGHT ICING EVENTS BECAUSE THE QPF IS QUITE LIGHT BUT
ALSO BECAUSE THE LAYERS ARE SHALLOW. THE FORECAST SOUNDINGS FROM
THE NAM AND ESPECIALLY THE RAP SUPPORT AT LEAST SOME LIGHT
FREEZING DRIZZLE MAINLY ALONG AND SOUTH OF INTERSTATE 80 AT
VARIOUS TIMES FROM LATE THIS AFTERNOON INTO TONIGHT...THEREFORE
WE HAVE ADDED PATCHY FREEZING DRIZZLE...OR AREAS OF FREEZING
DRIZZLE...TO THE SNOW CHANCES IN THOSE LOCATIONS. CONFIDENCE IN
THIS LIGHT ICING SCENARIO IS NOT HIGH ENOUGH TO ISSUE A WINTER
WEATHER ADVISORY FOR THE ABOVE MENTIONED AREAS. HOWEVER IF NEW
OBSERVATIONS AND MODEL RUNS SUGGEST A HIGHER LIKELIHOOD OF
FREEZING DRIZZLE AN ADVISORY MAY BE CONSIDERED LATER TODAY.
OTHERWISE THE TRACK OF THE LOW FAVORS THE HEAVIER SNOWS TO FALL IN
NORTHEAST NEBRASKA WHERE THE GOING WINTER WEATHER ADVISORY IS AT.
WE DID ADD ONE MORE TIER OF COUNTIES TO THE ADVISORY INCLUDING
ALBION AND NORFOLK. THIS SYSTEM IS UNIQUE IN THAT IT HAS A VERY
DEEP SATURATED LAYER THAT IS IN THE DENDRITIC GROWTH ZONE...AROUND
250 MB OR ABOUT 10000 FEET DEEP...YIELDING SNOW-LIQUID RATIOS AS
HIGH AS 20-1. BECAUSE OF THIS WE ALSO INCREASED SNOW AMOUNTS IN
NORTHEAST NEBRASKA ABOUT 1 MORE INCH. FORTUNATELY THERE WILL NOT
BE A LOT OF WIND WITH THIS SYSTEM SO LITTLE BLOWING AND DRIFTING
IS EXPECTED. SOME LOCATIONS IN THE ADVISORY AREA SHOULD SEE 4-5
INCHES OF DRY/FLUFFY SNOW STARTING TODAY AND ENDING FRIDAY
MORNING.
CONFIDENCE IN THE EXACT SNOW AMOUNTS IS MUCH LOWER TO THE SOUTH
OF THE ADVISORY AREA...MAINLY FROM THE LINCOLN TO OMAHA METRO
AREAS. HOWEVER...THERE IS LITTLE SUPPORT FOR MORE THAN 2 INCHES
GIVEN THE DRY LAYERS THAT WILL NEED TO BE SATURATED AND THE
WEAKER FORCING JUST SOUTH OF THE 700 MB LOW TRACK. CURRENTLY WE
ARE KEEPING THE 1-2 INCH AMOUNTS FOR LINCOLN-OMAHA AND THIS LOOKS
REASONABLE BY NOON FRIDAY WHEN ANY LIGHT SNOW ON THE BACK SIDE OF
THE LOW FINALLY ENDS. STARTED THE CHANCES FOR SNOW A BIT LATER
EAST OF A LINE FROM LINCOLN TO FREMONT...MAINLY CLOSER TO 18Z
TODAY...PRIMARILY DUE TO THE TIME IT WILL TAKE TO SATURATE THE
DRY LOW LEVELS IN THAT AREA.
TEMPERATURE AND WIND FORECASTS WERE ONLY SLIGHTLY ADJUSTED AS THE
PATTERN REMAINS FAIRLY COLD BUT DRY AFTER FRIDAY.
NIETFELD
&&
.AVIATION...
06Z TAFS FOR KOMA...KLNK AND KOFK.
DETERIORATING CONDITIONS ARE EXPECTED THROUGH THE 24 HOUR PERIOD
AT ALL TAF SITES. VFR CONDITIONS AT ALL TAF SITES INITIALLY WITH
LIGHT EAST SOUTHEAST WINDS. MID CLOUDS WILL INCREASE IN COVERAGE
AS A STORM SYSTEM BEGINS TO MOVE OFF THE HIGH PLAINS...BY 08-09Z
AT KOFK AND KLNK...AND KOMA BY 11Z. LIGHT SNOW AND MVFR CONDITIONS
WILL DEVELOP AT KOFK BY 13Z BECOMING PREVAILING BY 15Z WITH IFR
CONDITIONS DEVELOPING THEREAFTER. ONCE THE SNOW MOVES INTO THE
KOFK AREA...IT WILL LIKELY REMAIN THROUGH THE REST OF THE FORECAST
PERIOD WITH 2 TO 3 INCHES POSSIBLE THROUGH EARLY FRIDAY. AT
KOMA/KLNK...DRY AIR IN THE LOWER TO MID LEVELS SHOULD LIMIT
DEVELOPMENT EARLY IN THE TAF PERIOD...AND POSSIBLY DELAY ANY
FLURRY ACTIVITY UNTIL LATE AFTERNOON...OR MORE LIKELY UNTIL TOWARD
THE END OF THE PERIOD BY 28/02-06Z. COLD SEE MVFR FOG DEVELOP AT
KLNK/KOMA BY 15-19Z AS WELL.
DEWALD
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER WEATHER ADVISORY FROM NOON TODAY TO 6 AM CST FRIDAY FOR
NEZ011-012-015>018.
IA...WINTER WEATHER ADVISORY FROM NOON TODAY TO 6 AM CST FRIDAY FOR
IAZ043.
&&
$$
NIETFELD
AREA FORECAST DISCUSSION
NWS HASTINGS NE
243 AM CST THU DEC 27 2012
.SHORT TERM...THE MAIN ISSUE TO DEAL WITH IS TODAY/S LIGHT SNOW
EVENT.
WATER VAPOR AND INFRARED SATELLITE IMAGERY SUGGEST THE UPPER LEVEL
CIRCULATION SET TO IMPACT OUR AREA IS CENTERED IN THE TRI-STATE
CONFLUENCE OF WY/CO/NE. SPOKE OF ENERGY ALONG WITH WARM ADVECTION
PUSHING THROUGH THE FORECAST AT THIS TIME. RETURNS FROM NEARBY
RADARS SUGGEST PRECIPITATION IS DEVELOPING ALOFT IN THIS WARM
ADVECTION. NOTHING HAS REPORTEDLY MADE IT TO THE GROUND WITH DRY
AIR IN LOWER LEVELS OF THE ATMOSPHERE. THAT ALL SHOULD CHANGE
EARLY THIS MORNING...SAY AROUND DAWN...WITH LIGHT SNOWFALL STARTING
TO REACH THE SURFACE. SHORT TERM MODEL DATA /HRRR AND WRF/ POINT
TOWARD A BAND OF SNOW DEVELOPING IN THE VICINITY OF HIGHWAY 281
NAM QUICKLY LIFTING NORTH/NORTHEAST. THESE FINER DETAILS FIT WITH
THE NAM/GFS/SREF OUTPUT...WHICH EVENTUALLY PUT THE GREATEST
PRECIPITATION IN NORTHEAST NEBRASKA OF ABOUT 0.30". MEANWHILE...
THE NORTH/EAST FORECAST AREA MAY PICK UP A TENTH OR TWO OF LIQUID
EQUIVALENT MOISTURE...EQUATING INTO 1 TO 2 INCHES...MAYBE LOCALLY
3 INCHES OF SNOW. THE AREA AT MOST RISK FOR 3 INCHES...AND IT MAY
NOT BE THAT MUCH RISK...WOULD BE NORTHERN NANCE COUNTY...OR NORTHEAST
GREELEY COUNTY. THE VAST MAJORITY OF OUR NEBRASKA FORECAST IS IN
THE 1 TO 2 INCH RANGE...WITH LESS THAN 1 INCH IN NORTHERN KANSAS.
AT THIS TIME...WITH LIMITED WIND INFLUENCES...AND ONLY A SMALL PART
OF THE FORECAST AREA IN LINE FOR MARGINAL ADVISORY LEVEL SNOW
AMOUNTS...WILL NOT ISSUE ANY HEADLINES. IN FACT...IF YOU BUY INTO
THE 05Z HRRR OUTPUT...ONLY THE FAR NORTHEAST FORECAST AREA WOULD
CATCH 1 TO 2 INCHES OF SNOW...AND THE REST OF THE AREA AN INCH OR
LESS. AT THIS POINT...THERE SEEMS TO BE ENOUGH REASON NOT TO ISSUE
ANY ADVISORIES FOR THIS EVENT.
SHOULD MENTION...NAM SOUNDINGS IN THE SOUTHEAST PART OF THE FORECAST
AREA...ALONG WITH FUZZY NATURE OF PRECIPITATION OUTLOOK...SUGGEST A
BIT OF FREEZING DRIZZLE COULD DEVELOP DURING THE EVENING HOURS. LIFT
IS THE QUESTION...MEANING IS THERE ENOUGH? THINK THERE COULD BE A
COUPLE OF HOURS OF FREEZING DRIZZLE TYPE PRECIPITATION IN THIS AREA
AND HAVE ADDED THAT TO THE FORECAST GRIDS. NOT A HUGE DEAL...AND MAY
NOT MATERIALIZE...BUT WOULDN/T BE SHOCKED IF IT DID PAN OUT.
ON FRIDAY...THE MEANDERING NATURE OF THE UPPER LEVEL LOW TO THE
SOUTHEAST WILL KEEP CLOUDS AROUND FOR A GOOD PART OF THE DAY. FAR
EASTERN FORECAST AREA MAY EVEN SEE A LINGERING FLURRY EARLY IN THE
MORNING. ASIDE FROM THAT...NORTHWEST WINDS WILL DEVELOP...AND MAY
EVEN TURN SNEAKY BREEZY IF CLEARING DEVELOPS MORE RAPIDLY. FRIDAY
IS STILL A PART OF THE CURRENT COLD SPELL WITH HIGHS STRUGGLING FOR
ABOUT 20 MOST AREAS. THAT ALL STARTS TO CHANGE FRIDAY NIGHT...AS
DOWN-SLOPING WESTERLY WINDS SET UP AND LASTS INTO THE DAY SATURDAY.
THIS WILL RESULT IN SATURDAY BEING MUCH WARMER...RELATIVE TO RECENT
DAYS...WITH HIGHS IN THE UPPER 20S AND LOWER 30S AND PLENTY OF
SUNSHINE. THAT WON/T NECESSARILY MELT A WHOLE LOT...AND ITS STILL
BELOW NORMAL SOME 5 TO 7 DEGREES...BUT ITS AT LEAST A START.
.LONG TERM...STARTING SUNDAY MORNING...SUNDAY IS SHAPING UP TO BE
THE WARMEST DAY IN JUST OVER A WEEK AS THE COMBINATION OF WARMER AIR
SURGING NORTHWARD AHEAD OF AN APPROACHING LOW LEVEL TROUGH/FRONT AND
MOSTLY SUNNY SKIES UNDER THE INFLUENCE OF A BUILDING UPPER LEVEL
RIDGE...WILL RESULT IN A RETURN TO NEAR SEASONAL TEMPERATURES FOR
THE END OF DECEMBER. AS A RESULT...EXPECT TO SEE AFTERNOON
TEMPERATURES ACROSS SOUTH CENTRAL NEBRASKA APPROACH THE FREEZING
MARK...WITH UPPER 30S TO NEAR 40 DEGREES CURRENTLY FORECAST FOR
PORTIONS OF NORTH CENTRAL KANSAS. WHILE THIS LIKELY WILL NOT BE WARM
ENOUGH TO RESULT IN ANY SIGNIFICANT MELTING OF SNOW/ICE ON THE
GROUND...IT WILL LIKELY BE THE FIRST DAY SINCE DECEMBER 22ND THAT
TEMPERATURES WILL CLIMB ABOVE THE FREEZING MARK ACROSS THE MAJORITY
OF THE FORECAST AREA. THIS BRIEF WARM UP...HOWEVER...IS EXPECTED TO
BE FAIRLY SHORT LIVED...AS GLOBAL MODELS ARE INDICATING COOLER AIR
BEHIND THE APPROACHING TROUGH/FRONT...WHICH WILL BEGIN TO FILTER IN
ACROSS THE LOCAL AREA TO START THE NEW WORK WEEK. AS A
RESULT...EXPECT A RETURN TO SUBFREEZING AFTERNOON TEMPERATURES
MONDAY AFTERNOON WITH LITTLE EVIDENCE FOR ENOUGH LOW LEVEL MOISTURE
OR FORCING TO JUSTIFY ANYTHING OTHER THAN AN INCREASE IN CLOUDS
ACROSS THE LOCAL AREA MONDAY.
THEREAFTER...THE GLOBAL MODELS BEGIN TO DIVERGE SOME WITH THEIR
HANDLING OF AN UPPER LEVEL LOW ACROSS THE DESERT SOUTHWEST...WITH
THE GFS MAINTAINING A MUCH MORE PROGRESSIVE FLOW PATTERN THAN THE
EC...WHICH HAS BEEN TRYING TO CUT OFF THE UPPER LEVEL LOW ACROSS
NORTHERN MEXICO. HOWEVER...IN BOTH SCENARIOS...THE NORTHERN JET IS
FORECAST TO STEER AN UPPER LEVEL DISTURBANCE ACROSS NEBRASKA TUESDAY
NIGHT/WEDNESDAY...WHICH ONCE AGAIN IS EXPECTED TO HAVE A LACK IN
APPRECIABLE LOW LEVEL MOISTURE...WITH LITTLE MORE THAN A FEW HIGH
CLOUDS AND A CONTINUATION OF SUB FREEZING TEMPERATURES EXPECTED TO
PERSIST AS A RESULT. JUST BEYOND THE CURRENT SCOPE OF THE
FORECAST...THERE ARE SOME INDICATIONS THAT ANOTHER UPPER LEVEL RIDGE
OF HIGH PRESSURE WILL BUILD ACROSS THE CENTRAL PLAINS IN CONCERT
WITH A MORE SIGNIFICANT DOWN-SLOPING LOW LEVEL FLOW...WHICH MAY
RESULT IN TEMPERATURES WARMING ABOVE CLIMO TOWARDS THE END OF NEXT
WEEK.
&&
.PREV DISCUSSION... /ISSUED 1050 PM CST WED DEC 26 2012/
AVIATION...06Z KGRI TAF. VFR CONDITIONS EXPECTED THROUGH
11Z...WITH DETERIORATING CONDITIONS THEREAFTER. THE APPROACH OF A
STORM SYSTEM WILL BRING LOWERING CEILINGS AND SNOW TO THE AREA
DURING THE DAY THURSDAY. MVFR CONDITIONS ARE CURRENTLY EXPECTED
11-14Z...WITH IFR CONDITIONS 14-22Z. MVFR CONDITIONS ARE THEN
FORECAST 22Z ONWARD. THE SURFACE WIND WILL REMAIN FROM THE
EAST/SOUTHEAST AT AROUND 11KTS THROUGH MUCH OF THE TAF PERIOD.
VISIBILITY RESTRICTIONS WILL ALSO BE POSSIBLE IN -SN DURING THE
TAF PERIOD.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
AVIATION...SAR
SHORT TERM...NOAA/NWS/MORITZ
LONG TERM...SAR
$$
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
318 AM EST THU DEC 27 2012
.SYNOPSIS...
A POTENT WINTER STORM WILL IMPACT THE ENTIRE REGION TONIGHT
THROUGH THURSDAY NIGHT PRODUCING WIDESPREAD HEAVY SNOWS WITH
AMOUNTS OVER A FOOT. GUSTY WINDS WILL ALSO OCCUR ALONG THE WESTERN
SLOPES OF THE GREEN MOUNTAINS AND IN THE SAINT LAWRENCE VALLEY,
AND THIS MAY CAUSE AREAS OF BLOWING SNOW. SNOW SHOWERS WILL
CONTINUE ACROSS THE NORTHERN MOUNTAINS ON FRIDAY AS THE STORM
MOVES AWAY FROM THE REGION. THE WEEKEND WILL BE SEASONABLY COLD,
WITH A CONTINUED CHANCE OF LIGHT SNOW IN THE MOUNTAINS.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 1227 AM EST THURSDAY...EVERYTHING STILL ON TRACK WITH ONLY
MINOR ADJUSTMENTS MADE TO GOING FORECAST. LOW PRESSURE IS LOCATED
NEAR TIP OF SOUTHERN NEW JERSEY AT 992 MB. GREATEST PRESSURE FALLS
ARE ALONG THE NEW JERSEY COASTLINE...CONTINUING TO SUGGEST A TRACK
TOWARDS LONG ISLAND OVERNIGHT. SNOW HAS MADE IT AS FAR NORTH AS
BURLINGTON AND MASSENA AND WILL OVERSPREAD REST OF NORTHERN
VERMONT OVER NEXT COUPLE OF HOURS. INTENSITY OF SNOW INCREASES
QUICKLY AFTER ONSET. HAVE SEEN WIDESPREAD 1-2" PER HOUR RATES
ACROSS NEW YORK AND SOUTHERN VERMONT AS WELL AS POINTS FURTHER
SOUTH. LATEST HRRR CONTINUES TO SHOW THIS HEAVY BAND MOVING
NORTHWARD...WITH HEAVIEST PRECIP THROUGH 8Z IN SOUTHERN
AREAS...5-10Z IN THE CHAMPLAIN VALLEY AND NORTHERN VERMONT...AND
7-13Z ACROSS NORTHERN NEW YORK. ALSO OF NOTE...DOWNSLOPE WINDS
GUSTING INTO THE 20S ACROSS SOUTHWEST VERMONT.
EARLIER DISCUSSION FROM 642 PM EST...
EVERYTHING REMAINS ON TRACK...AND ONLY MINOR ADJUSTMENTS WERE
MADE. HAD TO DROP TEMPERATURES SLIGHTLY THIS EVENING...WITH
WIDESPREAD TEENS ACROSS THE REGION. LOWS WILL BE REACHED OVER THE
NEXT COUPLE OF HOURS...AND THEN SLOWLY RISE OVERNIGHT.
OTHERWISE...TRIED TO NARROW DOWN THE START TIME FOR SNOW ACROSS
THE AREA. PRIMARY LOW NOW LOCATED OVER WEST VIRGINIA WITH A
SECONDARY LOW DEVELOPING NEAR WAKEFIELD VIRGINIA. SECONDARY LOW
WILL TAKE OVER DURING THE REST OF THE EVENING AND PROGRESS TO NEAR
DELAWARE BY 03Z...NEW YORK CITY BY 09Z....AND THEN LONG ISLAND BY
12Z. JUDGING BY CURRENT OBSERVATIONS...SNOW HAS NOW REACHED AS FAR
NORTH AS THE MID-HUDSON VALLEY...THE CENTRAL MOHAWK VALLEY...AND
THE SHORES OF LAKE ONTARIO IN NEW YORK...WITH A SLOW NORTHWARD
PROGRESSION. SHOULD BE INTO THE ADIRONDACKS AND SOUTHERN VERMONT
AROUND 02Z (9 PM)...THE CHAMPLAIN VALLEY AROUND 04Z (11 PM)...AND
THE NORTHEAST KINGDOM AROUND 05Z (MIDNIGHT). HEAVIEST SNOW WITH
INITIAL BAND OF WARM AIR ADVECTION PRECIPITATION WILL LIKELY OCCUR
BETWEEN 07Z AND 10Z (2 AM AND 5 AM) WHERE RATES OF 1-2 INCHES PER
HOUR ARE POSSIBLE...ESPECIALLY IN THE SOUTHEAST- UPSLOPE FAVORED
LOCATIONS. DOWNSLOPE WINDS WILL ALSO BE INCREASING ACROSS THE
SOUTHERN GREENS WITH GUSTS UP TO 40 MPH POSSIBLE IN EASTERN
ADDISON AND RUTLAND COUNTIES BETWEEN 06Z AND 10Z (1 AM AND 5 AM).
THIS WILL CREATE SOME WARMING AND DRYING IN THOSE AREAS...AND
COMBINED WITH SOME WARMING ALOFT (750-800 MB) AS INDICATED BY
LATEST RAP AND NAM...WILL LIKELY SEE SOME SLEET MIX IN ACROSS
RUTLAND AND WINDSOR COUNTIES AFTER 07Z...AND ESPECIALLY AFTER 10Z.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY/...
AS OF 325 PM EST WEDNESDAY...GONNA BE A BUSY DAY THURSDAY. LOTS OF
SNOW. THE STORM WILL TRACK NORTHEAST AND CUT ACROSS CAPE COD (OR
VERY NEAR IT) BY LATE IN THE AFTERNOON. THIS PUTS THE NORTH
COUNTRY INTO A SWEET SPOT FOR THE HEAVIEST QPF. THE DRY SLOT JUST
WONT GET THIS FAR NORTH, AND AS THE LOW MOVES OFF TO THE EAST,
WE`LL BE IN THE PIVOT ZONE INTO THE AFTERNOON.
EXCELLENT DYNAMICS AND SNOW GROWTH MAXED WITH UPWARD MOTION
SHOULD RESULT IN A PERIOD OF HEAVY SNOW MOST EVERYWHERE. THINKING
THE PRIMARY TIME WILL BE 6AM TO NOON, WITH RATES OF 1-2" PER HOUR.
CAN`T RULE OUT LOCALIZED MESOSCALE BAND WITH EVEN A LITTLE BIT
MORE. LIQUID QPF WILL BE QUITE IMPRESSIVE. SPENT A GOOD DEAL OF
TIME TRYING TO ACCOUNT FOR OROGRAPHIC EFFECTS AS WELL. BY THE TIME
WE GET TO THURSDAY NIGHT, MOST OF US WILL SEE ON THE ORDER OF 1 TO
1.5" OF LIQUID EQUIVALENT. SHADOWING WILL MAKE THE NUMBER A LITTLE
LOWER IN THE NORTHEAST KINGDOM AND WESTERN SLOPES OF THE SOUTHERN
GREENS, BUT THEN THAT ON THE FLIP SIDE, OROGRAPHICS WILL HELP ON
THE EASTERN SIDES OF THE GREENS AND DACKS. HAVE INCREASED THE SNOW
TOTALS A FEW INCHES ACROSS THE BOARD -- THINKING 12 TO 17 INCHES,
WITH THE JACKPOT LOCATIONS SEEING ABOUT 20". EVEN THOSE WHO SEE
THE LEAST WILL GET ABOUT 8", WHICH IS NOT SHABBY.
WINDS WILL CONTINUE TO BE GUSTY THE FIRST HALF OF THURSDAY ALONG
THE WESTERN SLOPES. ALSO HAVE TO WATCH FOR STRONG NORTHEAST WINDS
FUNNELING DOWN THE ST LAWRENCE VALLEY. DONT THINK THEY`LL HIT
WIND ADVISORY CRITERIA, BUT STILL THEY`LL HAVE SUSTAINED WINDS 15
TO 25 MPH WITH HIGHER GUSTS -- AND THAT WILL CAUSE A CONSIDERABLE
AMOUNT OF DRIFTING/BLOWING SNOW OUT THERE. HAVE ADDED THAT WORDING
TO THE FORECAST.
SNOW WILL BEGIN TO TAPER OFF IN THE EVENING, THOUGH LIGHT SNOWS
WILL CONTINUE ALL NIGHT. AS THE LOW PUSHES EAST OF HERE, WINDS
WILL CLOCK AROUND TO NORTHWEST. MOISTURE WILL BE SLOW TO LEAVE, SO
THE NORTHWEST WINDS AND THAT MOISTURE WILL RESULT IN A GOOD AMOUNT
OF OROGRAPHICS, SO THE HIGHER TERRAIN WILL PICK UP A FEW
ADDITIONAL INCHES OF SNOW (AT LEAST) ON FRIDAY.
FINALLY TAPER POPS DOWN TO CHANCE LEVELS BY FRIDAY NIGHT, THOUGH A
WEAK SYSTEM APPROACHING FROM THE WEST MAY SPARK A LITTLE BIT OF
LIGHT SNOW/FLURRIES.
QUICK NOTE ON TEMPERATURES -- PRIMARILY KEPT TO THE COOLER SIDE OF
GUIDANCE FOR THE ENTIRE TIME.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 317 AM EST THURSDAY...LITTLE OVERALL CHANGE IN PREVIOUS DAYS
FORECAST THINKING FOR THE LONG TERM FORECAST AS MEDIUM RANGE
MODELS REMAIN CONSISTENT WITH THEIR RESPECTIVE SOLUTIONS...ALBEIT
WITH A FEW MINOR DIFFERENCES.
LOW PRESSURE DEVELOPING OFF THE CAROLINA/VIRGINIA COASTLINE LATE
SATURDAY AFTERNOON STILL ON TRACK TO MOVE NORTHEAST JUST OUTSIDE THE
BENCHMARK SATURDAY NIGHT INTO SUNDAY MORNING. LATEST TRENDS OF THE
GFS/ECMWF HAVE THE LOW TRACK EVER SO SLIGHTLY WEST COMPARED TO
PREVIOUS RUNS...WHICH BRINGS A LITTLE MORE LIGHT SNOW TO THE NORTH
COUNTRY...THOUGH REALLY NOTHING TO GET TOO WORKED UP ABOUT. WILL
CONTINUE TO PLAY SOME MIDDLE OF THE ROAD POPS (30-50%) ACROSS MAINLY
CENTRAL AND SOUTHERN PORTIONS OF THE AREA SATURDAY NIGHT AND SUNDAY
MORNING...WITH THE POSSIBILITY OF A COUPLE OF INCHES OF SNOW.
BRIEF RIDGE OF HIGH PRESSURE BUILDS IN FOR LATE SUNDAY NIGHT INTO
MONDAY WITH GENERALLY DRY CONDITIONS EXPECTED...ALBEIT CLOUDY AS
UPPER FLOW REMAINS FAIRLY ZONAL. MONDAY NIGHT INTO TUESDAY MORNING A
WEAK CLIPPER WILL BRING THE POSSIBILITY OF A FEW LIGHT SNOW SHOWERS
TO MAINLY NORTHERN SECTIONS OF THE CWA...FOLLOWED BY A WELL DEFINED
ARCTIC AIRMASS/BOUNDARY WHICH LOOKS TO AFFECT THE REGION THROUGH THE
REMAINDER OF THE FORECAST PERIOD. SOME DIFFERENCES STILL EXIST
BETWEEN THE GFS AND ECMWF IN REGARDS TO THE STRENGTH OF THIS
AIRMASS...WITH THE ECMWF ON THE COLDER SIDE OF NWP GUIDANCE. AS I
DID YESTERDAY...HAVE GONE WITH A BLEND FOR NOW WITH THE MAIN
HIGHLIGHTS FOR THE MIDDLE OF NEXT WEEK BEING BELOW NORMAL TEMPS AND
LOW CHANCES FOR A FEW LIGHT SNOW SHOWERS.
&&
.AVIATION /08Z THURSDAY THROUGH MONDAY/...
THROUGH 06Z FRIDAY...IFR TO VLIFR CONDITIONS IN HEAVY SNOW WILL
CONTINUE THROUGH THE MAJORITY OF THE TAF PERIOD AT ALL SITES. MAY
SEE A BRIEF PERIOD OF SLEET AT KRUT IN THE PRE-DAWN HOURS DUE TO
DOWNSLOPING WINDS AND WARMING ALOFT. IN ADDITION TO LOW FLIGHT
CATEGORIES...WINDS WILL BE AN ISSUE AT VARYING TIMES THROUGH THE
PERIOD. EAST TO SOUTHEAST LOW LEVEL JET MOVES ACROSS THE REGION
OVERNIGHT...WITH KRUT LIKELY TO EXPERIENCE STRONGEST WIND GUSTS
20-35 KTS THROUGH 12Z. ALSO...VALLEY CHANNELING AT KMSS WILL
PRODUCE GUSTS TO 20-25 KTS THROUGH THE PERIOD. ELSEWHERE STRONG
WINDS ARE LESS FAVORABLE...BUT SHOULD STILL TO SEE GUSTS TO 15-20
KTS MAINLY AFTER 12Z. THIS WILL CREATE AREAS OF BLOWING SNOW AND
NEAR WHITE-OUT CONDITIONS.
OUTLOOK 06Z FRIDAY THROUGH MONDAY...
06Z FRIDAY THROUGH 00Z SATURDAY...MVFR/IFR CONDITIONS TRENDING TO
VFR IN THE VALLEYS AS LOW PRESSURE MOVES INTO THE GULF OF MAINE.
IN ADDITION...FRESH SNOW AND GUSTY WINDS WILL PRODUCE SOME AREAS
OF BLOWING/DRIFTING SNOW.
00Z SATURDAY THROUGH 00Z SUNDAY...MAINLY VFR CONDITIONS AS HIGH
PRESSURE BUILDS INTO THE REGION. LINGERING MVFR SNOW SHOWERS
POSSIBLE AT MPV/SLK THRU 06Z SATURDAY.
00Z SUNDAY THROUGH MONDAY...MAINLY VFR CONDITIONS WITH A CHANCE OF
MVFR SNOW SHOWERS ACROSS CENTRAL AND SOUTHERN AREAS SATURDAY NIGHT
AS LOW PRESSURE PASSES SOUTH AND EAST OF THE REGION.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...WINTER STORM WARNING UNTIL 7 AM EST FRIDAY FOR VTZ001>012-
016>019.
NY...WINTER STORM WARNING UNTIL 7 AM EST FRIDAY FOR NYZ026>031-034-
035-087.
&&
$$
SYNOPSIS...NASH
NEAR TERM...RJS/MUCCILLI
SHORT TERM...NASH
LONG TERM...LAHIFF
AVIATION...LAHIFF
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
1254 AM EST THU DEC 27 2012
.SYNOPSIS...
A POTENT WINTER STORM WILL IMPACT THE ENTIRE REGION TONIGHT
THROUGH THURSDAY NIGHT PRODUCING WIDESPREAD HEAVY SNOWS WITH
AMOUNTS OVER A FOOT. GUSTY WINDS WILL ALSO OCCUR ALONG THE WESTERN
SLOPES OF THE GREEN MOUNTAINS AND IN THE SAINT LAWRENCE VALLEY,
AND THIS MAY CAUSE AREAS OF BLOWING SNOW. SNOW SHOWERS WILL
CONTINUE ACROSS THE NORTHERN MOUNTAINS ON FRIDAY AS THE STORM
MOVES AWAY FROM THE REGION. THE WEEKEND WILL BE SEASONABLY COLD,
WITH A CONTINUED CHANCE OF LIGHT SNOW IN THE MOUNTAINS.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 1227 AM EST THURSDAY...EVERYTHING STILL ON TRACK WITH ONLY
MINOR ADJUSTMENTS MADE TO GOING FORECAST. LOW PRESSURE IS LOCATED
NEAR TIP OF SOUTHERN NEW JERSEY AT 992 MB. GREATEST PRESSURE FALLS
ARE ALONG THE NEW JERSEY COASTLINE...CONTINUING TO SUGGEST A TRACK
TOWARDS LONG ISLAND OVERNIGHT. SNOW HAS MADE IT AS FAR NORTH AS
BURLINGTON AND MASSENA AND WILL OVERSPREAD REST OF NORTHERN
VERMONT OVER NEXT COUPLE OF HOURS. INTENSITY OF SNOW INCREASES
QUICKLY AFTER ONSET. HAVE SEEN WIDESPREAD 1-2" PER HOUR RATES
ACROSS NEW YORK AND SOUTHERN VERMONT AS WELL AS POINTS FURTHER
SOUTH. LATEST HRRR CONTINUES TO SHOW THIS HEAVY BAND MOVING
NORTHWARD...WITH HEAVIEST PRECIP THROUGH 8Z IN SOUTHERN
AREAS...5-10Z IN THE CHAMPLAIN VALLEY AND NORTHERN VERMONT...AND
7-13Z ACROSS NORTHERN NEW YORK. ALSO OF NOTE...DOWNSLOPE WINDS
GUSTING INTO THE 20S ACROSS SOUTHWEST VERMONT.
EARLIER DISCUSSION FROM 642 PM EST...
EVERYTHING REMAINS ON TRACK...AND ONLY MINOR ADJUSTMENTS WERE
MADE. HAD TO DROP TEMPERATURES SLIGHTLY THIS EVENING...WITH
WIDESPREAD TEENS ACROSS THE REGION. LOWS WILL BE REACHED OVER THE
NEXT COUPLE OF HOURS...AND THEN SLOWLY RISE OVERNIGHT.
OTHERWISE...TRIED TO NARROW DOWN THE START TIME FOR SNOW ACROSS
THE AREA. PRIMARY LOW NOW LOCATED OVER WEST VIRGINIA WITH A
SECONDARY LOW DEVELOPING NEAR WAKEFIELD VIRGINIA. SECONDARY LOW
WILL TAKE OVER DURING THE REST OF THE EVENING AND PROGRESS TO NEAR
DELAWARE BY 03Z...NEW YORK CITY BY 09Z....AND THEN LONG ISLAND BY
12Z. JUDGING BY CURRENT OBSERVATIONS...SNOW HAS NOW REACHED AS FAR
NORTH AS THE MID-HUDSON VALLEY...THE CENTRAL MOHAWK VALLEY...AND
THE SHORES OF LAKE ONTARIO IN NEW YORK...WITH A SLOW NORTHWARD
PROGRESSION. SHOULD BE INTO THE ADIRONDACKS AND SOUTHERN VERMONT
AROUND 02Z (9 PM)...THE CHAMPLAIN VALLEY AROUND 04Z (11 PM)...AND
THE NORTHEAST KINGDOM AROUND 05Z (MIDNIGHT). HEAVIEST SNOW WITH
INITIAL BAND OF WARM AIR ADVECTION PRECIPITATION WILL LIKELY OCCUR
BETWEEN 07Z AND 10Z (2 AM AND 5 AM) WHERE RATES OF 1-2 INCHES PER
HOUR ARE POSSIBLE...ESPECIALLY IN THE SOUTHEAST- UPSLOPE FAVORED
LOCATIONS. DOWNSLOPE WINDS WILL ALSO BE INCREASING ACROSS THE
SOUTHERN GREENS WITH GUSTS UP TO 40 MPH POSSIBLE IN EASTERN
ADDISON AND RUTLAND COUNTIES BETWEEN 06Z AND 10Z (1 AM AND 5 AM).
THIS WILL CREATE SOME WARMING AND DRYING IN THOSE AREAS...AND
COMBINED WITH SOME WARMING ALOFT (750-800 MB) AS INDICATED BY
LATEST RAP AND NAM...WILL LIKELY SEE SOME SLEET MIX IN ACROSS
RUTLAND AND WINDSOR COUNTIES AFTER 07Z...AND ESPECIALLY AFTER 10Z.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/...
AS OF 325 PM EST WEDNESDAY...GONNA BE A BUSY DAY THURSDAY. LOTS OF
SNOW. THE STORM WILL TRACK NORTHEAST AND CUT ACROSS CAPE COD (OR
VERY NEAR IT) BY LATE IN THE AFTERNOON. THIS PUTS THE NORTH
COUNTRY INTO A SWEET SPOT FOR THE HEAVIEST QPF. THE DRY SLOT JUST
WONT GET THIS FAR NORTH, AND AS THE LOW MOVES OFF TO THE EAST,
WE`LL BE IN THE PIVOT ZONE INTO THE AFTERNOON.
EXCELLENT DYNAMICS AND SNOW GROWTH MAXED WITH UPWARD MOTION
SHOULD RESULT IN A PERIOD OF HEAVY SNOW MOST EVERYWHERE. THINKING
THE PRIMARY TIME WILL BE 6AM TO NOON, WITH RATES OF 1-2" PER HOUR.
CAN`T RULE OUT LOCALIZED MESOSCALE BAND WITH EVEN A LITTLE BIT
MORE. LIQUID QPF WILL BE QUITE IMPRESSIVE. SPENT A GOOD DEAL OF
TIME TRYING TO ACCOUNT FOR OROGRAPHIC EFFECTS AS WELL. BY THE TIME
WE GET TO THURSDAY NIGHT, MOST OF US WILL SEE ON THE ORDER OF 1 TO
1.5" OF LIQUID EQUIVALENT. SHADOWING WILL MAKE THE NUMBER A LITTLE
LOWER IN THE NORTHEAST KINGDOM AND WESTERN SLOPES OF THE SOUTHERN
GREENS, BUT THEN THAT ON THE FLIP SIDE, OROGRAPHICS WILL HELP ON
THE EASTERN SIDES OF THE GREENS AND DACKS. HAVE INCREASED THE SNOW
TOTALS A FEW INCHES ACROSS THE BOARD -- THINKING 12 TO 17 INCHES,
WITH THE JACKPOT LOCATIONS SEEING ABOUT 20". EVEN THOSE WHO SEE
THE LEAST WILL GET ABOUT 8", WHICH IS NOT SHABBY.
WINDS WILL CONTINUE TO BE GUSTY THE FIRST HALF OF THURSDAY ALONG
THE WESTERN SLOPES. ALSO HAVE TO WATCH FOR STRONG NORTHEAST WINDS
FUNNELING DOWN THE ST LAWRENCE VALLEY. DONT THINK THEY`LL HIT
WIND ADVISORY CRITERIA, BUT STILL THEY`LL HAVE SUSTAINED WINDS 15
TO 25 MPH WITH HIGHER GUSTS -- AND THAT WILL CAUSE A CONSIDERABLE
AMOUNT OF DRIFTING/BLOWING SNOW OUT THERE. HAVE ADDED THAT WORDING
TO THE FORECAST.
SNOW WILL BEGIN TO TAPER OFF IN THE EVENING, THOUGH LIGHT SNOWS
WILL CONTINUE ALL NIGHT. AS THE LOW PUSHES EAST OF HERE, WINDS
WILL CLOCK AROUND TO NORTHWEST. MOISTURE WILL BE SLOW TO LEAVE, SO
THE NORTHWEST WINDS AND THAT MOISTURE WILL RESULT IN A GOOD AMOUNT
OF OROGRAPHICS, SO THE HIGHER TERRAIN WILL PICK UP A FEW
ADDITIONAL INCHES OF SNOW (AT LEAST) ON FRIDAY.
FINALLY TAPER POPS DOWN TO CHANCE LEVELS BY FRIDAY NIGHT, THOUGH A
WEAK SYSTEM APPROACHING FROM THE WEST MAY SPARK A LITTLE BIT OF
LIGHT SNOW/FLURRIES.
QUICK NOTE ON TEMPERATURES -- PRIMARILY KEPT TO THE COOLER SIDE OF
GUIDANCE FOR THE ENTIRE TIME.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 342 PM EST WEDNESDAY...OVERALL LITTLE CHANGE FROM PREVIOUS
COUPLE OF FCSTS...WITH BLW NORMAL TEMPS AND PRECIP EXPECTED FOR
DAYS 4 THRU 7. THE EXTENDED FCST CHALLENGE WL BE TIMING/MAGNITUDE
OF ARCTIC AIRMASS ACRS OUR CWA EARLY NEXT WK. WL CONT TO MENTION
LOW CHC POPS FOR LATE SAT INTO SUNDAY ASSOCIATED WITH MID/UPPER
LVL TROF AND SOME 850 TO 500MB RH. LATEST TRENDS HAVE BEEN FOR
LESS RH AND QPF ACRS OUR CWA...BUT ECMWF IS A BIT CLOSER TO THE
COAST WITH SFC LOW PRES AND ENOUGH MOISTURE MAY MOVE BACK INTO OUR
CWA FOR SOME LIGHT SNOW. OTHERWISE...ECMWF/GEM SHOW MID/UPPER LVL
TROF DEVELOPING ACRS EASTERN CANADA WITH A MAINLY DRY NW FLW
ALOFT. HOWEVER...A WELL DEFINED ARCTIC BOUNDARY WL PUSH ACRS OUR
CWA EARLY NEXT WEEK...ALONG WITH A RIBBON OF ENHANCED MOISTURE.
THIS MOISTURE...ALONG WITH SOME ADDITIONAL MOISTURE FROM THE GREAT
LAKES WL HELP IN PRODUCING SOME SNOW SHOWERS ACRS OUR CWA ON
MONDAY INTO TUES. IN ADDITION...MUCH COLDER TEMPS WL ADVECT BACK
INTO OUR CWA FOR NEXT WK. STILL SOME UNCERTAINTY WITH REGARDS TO
TIMING OF THIS FEATURE...AS GFS IS 6 TO 12 HRS SLOWER AND SHOWS
THE COLDEST TEMPS ACRS OUR CWA ON WEDS. TIMING OF BOUNDARY WL MAKE
A HUGE DIFFERENCE IN TEMPS FROM NEAR 30F AT BTV IF THE GFS IS
RIGHT TO LOWER TEENS IF THE ECMWF/GEM ARE CORRECT ON TUES. GIVEN THE
DEVELOPMENT OF A LARGE SCALE TROF AND DEEP CYCLONIC FLW ACRS THE
NE CONUS...WL TREND TWD THE COLDER ECMWF/GEM FOR NEXT WEEK...AND
MENTION HIGHS ONLY IN THE TEENS/L20S WITH LOWS MAINLY IN THE
SINGLE DIGITS/LOWER TEENS. IF SFC HIGH PRES BUILDS INTO THE
REGION...FASTER THAN PROGGED...THEN WINDS WL DECREASE AND
OVERNIGHT LOWS WL NEED TO BE ADJUSTED DOWN BY 5 TO 10 DEGREES. ITS
ALWAYS DIFFICULT TO DETERMINE AMOUNT OF CAA AND IMPACTS ACRS OUR
CWA IN THE DAY 5 TO 7 RANGE. TODAY IS A GREAT EXAMPLE OF TRYING TO
PREDICT THE COLD AIR...AS TEMPS STRUGGLED MAINLY IN THE TEENS.
&&
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
THROUGH 06Z FRIDAY...IFR TO VLIFR CONDITIONS IN HEAVY SNOW WILL
CONTINUE THROUGH THE MAJORITY OF THE TAF PERIOD AT ALL SITES. MAY
SEE A BRIEF PERIOD OF SLEET AT KRUT IN THE PRE-DAWN HOURS DUE TO
DOWNSLOPING WINDS AND WARMING ALOFT. IN ADDITION TO LOW FLIGHT
CATEGORIES...WINDS WILL BE AN ISSUE AT VARYING TIMES THROUGH THE
PERIOD. EAST TO SOUTHEAST LOW LEVEL JET MOVES ACROSS THE REGION
OVERNIGHT...WITH KRUT LIKELY TO EXPERIENCE STRONGEST WIND GUSTS
20-35 KTS THROUGH 12Z. ALSO...VALLEY CHANNELING AT KMSS WILL
PRODUCE GUSTS TO 20-25 KTS THROUGH THE PERIOD. ELSEWHERE STRONG
WINDS ARE LESS FAVORABLE...BUT SHOULD STILL TO SEE GUSTS TO 15-20
KTS MAINLY AFTER 12Z. THIS WILL CREATE AREAS OF BLOWING SNOW AND
NEAR WHITE-OUT CONDITIONS.
OUTLOOK 06Z FRIDAY THROUGH MONDAY...
06Z FRIDAY THROUGH 00Z SATURDAY...MVFR/IFR CONDITIONS TRENDING TO
VFR IN THE VALLEYS AS LOW PRESSURE MOVES INTO THE GULF OF MAINE.
IN ADDITION...FRESH SNOW AND GUSTY WINDS WILL PRODUCE SOME AREAS
OF BLOWING/DRIFTING SNOW.
00Z SATURDAY THROUGH 00Z SUNDAY...MAINLY VFR CONDITIONS AS HIGH
PRESSURE BUILDS INTO THE REGION. LINGERING MVFR SNOW SHOWERS
POSSIBLE AT MPV/SLK THRU 06Z SATURDAY.
00Z SUNDAY THROUGH MONDAY...MAINLY VFR CONDITIONS WITH A CHANCE OF
MVFR SNOW SHOWERS ACROSS CENTRAL AND SOUTHERN AREAS SATURDAY NIGHT
AS LOW PRESSURE PASSES SOUTH AND EAST OF THE REGION.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...WINTER STORM WARNING UNTIL 7 AM EST FRIDAY FOR VTZ001>012-
016>019.
NY...WINTER STORM WARNING UNTIL 7 AM EST FRIDAY FOR NYZ026>031-034-
035-087.
&&
$$
SYNOPSIS...NASH
NEAR TERM...RJS/MUCCILLI
SHORT TERM...NASH
LONG TERM...TABER
AVIATION...LAHIFF
AREA FORECAST DISCUSSION
NWS BINGHAMTON NY
1252 AM EST THU DEC 27 2012
.SYNOPSIS...
A STRONG WINTER STORM WILL IMPACT THE AREA TONIGHT LEADING TO
HEAVY SNOW ACCUMULATIONS ACROSS THE ENTIRE FORECAST AREA. WRAP
AROUND MOISTURE WILL THEN RESULT IN CONTINUED SNOWS FOR MUCH OF
CENTRAL NEW YORK ON THURSDAY BEFORE HIGH PRESSURE SLOWLY BUILDS
INTO THE AREA TOWARDS THE CONCLUSION OF THE WEEK.
&&
.NEAR TERM /THROUGH TODAY/...
10 PM UPDATE... WELL DEFINED AND NARROW DRY SLOT CONTS ITS NWD
CHARGE ATTM...ALG THE I-81 CORRIDOR. THUS...PCPN HAS AT LEAST
TEMPORARILY TAPERED OFF...AND ALSO MIXED WITH SLEET/-FZRA...FROM
ABT KBGM SWD TWDS W-B/SCRANTON. MEANWHILE...INTERESTINGLY...HVYR
PCPN (MAINLY SNOW) CONTS ACRS THE WRN CATSKILLS AND
POCONOS...LIKELY IN RESPONSE TO INCRD FGEN FORCING...ASSOCD WITH
DVLPG SFC/MID-LVL CYCLONES ACRS THE DELMARVA RGN. ALSO...HVY SNOW
PERSISTS TO OUR W AND N...TIED TO ORIGINAL BAND OF STG ISEN LIFT.
WHAT HAPPENS FROM HERE ON IN?? WELL...THE LATEST RAPID REFRESH
DATA...ALG WITH INCOMING 00Z NAM/GFS OUTPUT...HAS COME INTO LINE
PRETTY WELL...SUGGESTING THAT HVYR PCPN WILL BE MOST SUSTAINED
JUST W OF THE I-81 CORRIDOR IN THE 06-10Z TIME FRAME...AS THE BEST
FORCED LIFT TENDS TO CONSOLIDATE IN THIS RGN. HVYR PCPN NOW ACRS
OUR SERN ZNS...SHOULD HAVE A TENDENCY TO BECOME LGTR AND MORE
SPOTTY AFTER MIDNIGHT...UNDERNEATH EXPANDING DRY SLOT ALOFT.
AS LOW-LVL CAA/VEERING BLYR WINDS START TO KICK IN TWDS
DAYBREAK...AS THE MAIN STORM BCMS MORE VERTICALLY STACKED NEAR
NYC...A GENERAL AND LGTR WRAP-ARND SNOW PATN SHOULD BEGIN TO
BECOME ESTABLISHED.
AGN...BOTTOM LN...NOT MUCH CHG MADE TO OVERNIGHT SNOW ACCUMS/STORM
TOTALS. HVYR AMTS...AS EXPECTED...WILL LIKELY END UP OVER WRN AND NRN
PTNS OF THE FA. SOME 6"+ SNOW TOTALS ALSO SEEN AS FAR SEWD AS SXNS
OF THE TWIN TIERS/CHENANGO/OTSEGO CNTYS...AND SULLIVAN/PIKE/WAYNE
CNTYS IN THE POCONOS/WRN CATSK.
PREV UPDATE... 8 PM UPDATE... RADAR/SAT LOOPS SHOW A WELL DEFINED
DRY SLOT HEADING NWD THROUGH ERN PA ATTM. THE LATEST RAPID REFRESH
MODEL RUNS...AND ALSO THE 18Z NWP GUIDANCE SHOW THIS FEATURE...BUT
HAVE NOT QUITE CAUGHT ON TO ITS QUICK NWD MOVEMENT. THUS...WE`VE
SPED UP THE TRANSITION FROM STEADY HVY SNOW...TO LGTR SNOW...OR A
LGT MIX...GENERALLY OCCURRING FROM 00-03Z...ALG AND JUST E OF THE
I-81 CORRIDOR.
ALSO...THE CHARACTER OF THE RADAR ECHOES...PLUS
PLENTIFUL SPOTTER/PUBLIC REPORTS...SHOW A HODGE-PODGE OF
SNOW...SLEET...FZRA BASICALLY ALG AND S OF ROUTE 6 IN NRN PA ATTM.
THIS AREA OF MIXED PCPN WILL PROBABLY EXTEND TO ABT THE I-88
CORRIDOR IN SRN NY TWDS 03-04Z...BUT WE DON`T EXPECT IT TO MOVE
ANY FARTHER TO THE N OR W.
AT THIS JUNCTURE...WE DON`T SEE A LOT OF EVIDENCE THAT THE ERLY
FLOW/TERRAIN INDUCED PCPN SHADOWING...CONSISTENTLY SHOWN BY MANY
OF OUR HI-RES MODELS FOR THIS EVE...HAS DVLPD...OR WILL DVLP.
WE`LL SEE HOW THE DRY SLOT ADVANCING ACRS PA DVLPS LTR THIS
EVE...IN THIS REGARD.
BOTTOM LN...WE`RE NOT MAKING ANY SUBSTANTIVE CHGS TO OUR SNOW
TOTALS. INITIAL BURST OF VERY HVY SNOW IN OUR FAR SRN ZNS IN THE MID TO
LATE AFTN HRS...HAVE BROUGHT SNOW TOTALS INTO THE 3-6" RANGE ATTM.
GIVEN MIXED PCPN THESE AREAS CURRENTLY...TOTALS WILL LIKELY NOT GO
A GREAT DEAL HIGHER. ACRS THE TWIN TIERS...VERY HVY SNOW THE LAST
SVRL HRS...IS LIKELY TO SLOW DOWN A BIT THROUGH ABT
06Z...ESPECIALLY S AND E OF A TOWANDA TO KBGM TO ONEONTA LN. SNOW
TOTALS HAVE RANGED FROM 4-8" IN MANY LOCALES THROUGHOUT THESE
AREAS SO FAR.
FOR MANY OF OUR NRN AND WRN ZNS...HVY SNOW BANDS WILL CONTINUE TO
ROTATE ACRS THROUGH AT LEAST 06Z...AS MID-LVL FGEN MAXIMIZES...AND
THETA-E LR`S ALOFT DECREASE ON THE LEADING EDGE OF THE DRY SLOT.
ISOLD THUNDER-SNOW NOT OUT OF THE QUESTION...AND IN FACT...SOME
OF THIS HAS ALREADY BEEN REPORTED IN CHENANGO CNTY. STORM TOTALS
OF A FOOT OR MORE WILL BE MOST PROBABLE THESE PTNS OF THE FA.
OVERALL...ONLY MINOR TWEAKS MADE...TO BEST REFLECT THE LATEST
RADAR/TEMP TRENDS. NEAR-TERM SPS`S AND FREQUENT WSW UPDATES WILL
CONTINUE TO BE ISSUED.
EARLIER DISC... CONDITIONS RAPIDLY DETERIORATING ACROSS THE AREA THIS
AFTERNOON AS LONG ADVERTISED WINTER STORM GETS UNDERWAY. REGIONAL
WATER VAPOR IMAGERY SHOWING MAIN MID-LEVEL CIRCULATION SLIDING
ACROSS THE EASTERN TN/KY BORDER THIS AFTERNOON...WITH NOTABLE DRY
SLOT BEGINNING TO WORK NORTH TOWARDS PIT AS SYSTEM CONTINUES THE
OCCLUSION PROCESS. LATEST RUC TROP PRESSURE FIELD SHOWS MAIN WAVE
NOW TAKING ON A NEGATIVE TILT WHICH SUGGEST UPPER FEATURE IS
REACHING MATURITY. MEANWHILE ALONG THE SURFACE...SECONDARY LOW
PRESSURE DEVELOPMENT NOW TAKING SHAPE ACROSS THE NORTH CAROLINA
PIEDMONT REGION...WITH SFC PRESSURE FIELDS REVEALING A NOTABLE
COLD AIR DAMMING SIGNATURE ALONG THE EASTERN SPIN OF THE
APPALACHIANS. IF NOTHING LESS...THE PRESENCE OF THIS SIGNATURE
WILL HELP ENSURE CONDITIONS ARE PRE-CONDITIONED FOR A ROUND OF
HEAVY SNOWFALL ACROSS THE FCST AREA TONIGHT AS WARM AIR ADVECTION
FORCING INCREASES IN ADVANCE OF THE SECONDARY LOW PRESSURE
SYSTEM/S MOVEMENT UP THE EAST COAST.
THE ABOVE SAID...LATEST RADAR TRENDS SHOWING SNOW MAKING STEADY
PROGRESS NORTHWARD THIS AFTERNOON WITH SNOW ALREADY BEING
REPORTED AT BOTH ELM AND AVP. QUICK INSPECTION OF RUC LAYERED
THETA-E LAPSE RATES SUGGEST A FAIR AMOUNT OF CONDITIONAL
INSTABILITY EXISTS ALOFT WHICH WILL LEAD TO SNOWFALL RATES ON THE
ORDER OF 2-3`/HR UNDER THE HEAVIEST ACTIVITY. DESPITE THE FACT THE
STORM IS ALREADY ONGOING ACROSS THE AREA...A FAIR AMOUNT OF MODEL
UNCERTAINTY STILL EXISTS WITH EXPECTED CONDITIONS OVERNIGHT AS THE
SECONDARY LOW PASSES TO OUR SOUTH AND EAST. WHAT DOES APPEAR FOR
CERTAIN IS THAT THE HEAVIEST SNOWFALL WILL OCCUR BETWEEN NOW AND
06Z AS THE MAIN AREA OF FRONTOGENESIS AND WARM AIR ADVECTION
FORCING LIFTS THROUGH THE FCST AREA. UNFORTUNATELY THIS WILL OCCUR
DURING THE AFTERNOON COMMUTE WHICH WILL UNDOUBTEDLY MAKE THINGS
DICEY FOR THOSE HEADING HOME THIS EVENING. MODELS CONTINUE TO
INSIST ON THE PREVIOUSLY MENTIONED DRY SLOT MOVING NORTH INTO OUR
AREA AFTER 06Z WHICH WILL LEAD TO A FAIR AMOUNT OF DRYING WITHIN
THE DENDRITIC SNOW GROWTH REGION. AS A RESULT...WE EXPECT TO SEE
THE HEAVY SNOW ZONE GRADUALLY ROTATE TO THE WEST WITH TIME AS A
POORLY DEFINED DEFORMATION AXIS ATTEMPTS TO FORM AFTER 06Z.
FURTHER TO THE EAST...PRONOUNCED DRY AIR ALOFT WILL LIKELY LEAD TO
A GRADUAL DECREASE IN SNOWFALL INTENSITY FOR THE SUSQUEHANNA
VALLEY REGION OF CENTRAL NY AND POINTS SOUTH TO INCLUDE THE TWIN
TIERS...POCONOS...AND LOWER WYOMING VALLEY. DESPITE THE PRESENCE
OF THE DRY SLOT...FORECAST MODELS CONTINUE TO PRODUCE LIGHT QPF
ACROSS THESE REGIONS WHICH LEADS US TO BELIEVE THAT FREEZING RAIN
AND PERHAPS SOME SLEET WILL BEGIN FOR THESE AREAS TOWARDS THE
EARLY MORNING HRS. IF THIS WERE TO OCCUR AS ADVERTISED...A FAIRLY
HEALTHY ICING EVENT MAY HAPPEN FOR THOSE LOCATIONS. FOR NOW WE
EXPECT THE HEAVIEST ICING TO OCCUR ACROSS THE WYOMING VALLEY AND
SOUTHERN POCONOS WHERE A QUARTER INCH OR MORE OF ICE WILL BE POSSIBLE.
ANOTHER INTRIGUING ASPECT OF THIS STORM IS THAT ALL MODELS TO
INCLUDE THE LOWER RESOLUTION ECMWF SHOW A SHADOWING EFFECT JUST
WEST OF THE CATSKILLS AFTER 06Z THIS EVENING. THIS SEEMS PLAUSIBLE
TO SOME DEGREE AS A STRONG EASTERLY LOW-LEVEL JET OF 70+KTS
IMPINGES ON THE MOUNTAIN RANGE. FOR NOREASTER TYPE EVENTS THIS
SEEMS VERY UNUSUAL HOWEVER WITH ALL SHORT TERM MODEL PROGS
CONTINUING TO INSIST THIS WILL OCCUR...HAVE ELECTED TO LOWER
SNOWFALL TOTALS ACROSS THE WESTERN CATSKILLS JUST A TAD.
SO TO SUM THINGS UP...THE HEAVIEST SNOWS ARE EXPECTED FROM THE
CHEMUNG RVR VLY NORTHEAST TROUGH THE FINGER LAKES AND WESTERN
MOHAWK VALLEY. ACROSS THESE LOCATIONS...ANYWHERE BETWEEN 10-14"
WILL BE POSSIBLE. FURTHER SOUTH AND EAST...8-10" ARE FORECAST
ACROSS THE TWIN TIERS AND WESTERN CATSKILLS...WITH 4-6" EXPECTED
FOR THE SOUTHERN CATSKILLS...POCONOS AND LOWER WYOMING VLY. NO
CHANGES MADE TO INHERITED HAZARDS WITH THE EXCEPTION OF BEEFING UP
THE WORDING FOR POTENTIAL ICE ACCUMULATIONS ACROSS THE SOUTH.
FOR THURSDAY...EXPECT SOME LINGERING WRAP AROUND MOISTURE TO LEAD
TO CONTINUED SNOW ACROSS PORTIONS OF UPSTATE NY. H85 TEMPS LOOK A
TAD TOO WARM TO RESULT IN ANY SIGNIFICANT LAKE ENHANCEMENT. WILL
CONTINUE TO CARRY LIKELY POPS ACROSS THE NORTH WITH SLGT CHC-CHC
TO THE SOUTH.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM FRIDAY/...
STORM MOVES AWAY FROM THE AREA THURSDAY NIGHT. EXPECT SOME LIGHT
LAKE EFFECT SNOW SOUTH-SOUTHEAST OF LAKE ONTARIO WITH A 320 TO 325
DEGREE FLOW AND SOME LINGERING MOISTURE. HOWEVER WITH MARGINAL
TEMPERATURES AROUND -8 TO -10 DEGREES C AT 850 MB AND INVERSION HGTS
GENERALLY BELOW 5000 FEET EXPECT ONLY LIGHT ACCUMULATIONS... MAYBE
AROUND 2 INCHES ACROSS CENTRAL NY DOWN THROUGH AREAS SOUTHEAST OF
THE FINGER LAKES. DRYING MOVES IN WITH A WEAK RIDGE OF HIGH PRESSURE
ON FRIDAY PUTTING AN END TO ANY LINGERING LIGHT SNOW SHOWERS OR
FLURRIES DURING THE DAY.
NEXT SYSTEM APPROACHES THE AREA LATER FRIDAY NIGHT INTO SATURDAY.
MODEL CONSENSUS WITH THIS NEXT SYSTEM INDICATES A WEAK INVERTED
SURFACE TROUGH TRACKING ACROSS THE AREA WITH SOME LIGHT SNOW... BUT
SIGNIFICANT DEVELOPMENT OF THE SURFACE LOW DOES NOT OCCUR UNTIL THE
STORM IS WELL EAST OF THE MID-ATLANTIC COAST. THEREFORE HEAVY SNOW
DOES NOT APPEAR LIKELY AT THIS TIME.
.LONG TERM /SUNDAY THROUGH TUESDAY...
GFS AND ECMWF ARE IN REASONABLY GOOD AGREEMENT WITH THE OVERALL
PATTERN DURING THIS PERIOD INDICATING NORTHWEST FLOW WITH A SERIES
OF WEAKLY ORGANIZED CLIPPER SYSTEMS LIKELY ALONG WITH SOME LAKE EFFECT
SNOW. HOWEVER AT THIS POINT THERE IS NO INDICATION FOR ANY MAJOR
SYNOPTIC SCALE SYSTEMS THAT WOULD TAP GULF MOISTURE. TIMING OF THESE
INDIVIDUAL SYSTEMS WILL BE DIFFICULT BEYOND SUNDAY... BUT RIGHT NOW
THE BEST CHC FOR A WEAKLY ORGANIZED CLIPPER-LIKE SYSTEM COULD BE NEW
YEAR`S EVE INTO NEW YEAR`S DAY... WHICH WOULD BE FOLLOWED BY AN
ENHANCED PERIOD OF LAKE EFFECT SNOW. TEMPERATURES THROUGH THE PERIOD
WILL AVERAGE NEAR TO BELOW NORMAL... WITH HIGHS MAINLY IN THE MID
20S TO LOWER 30S AND LOWS IN THE TEENS. HAVE GONE WITH HPC GUIDANCE
THROUGH THE PERIOD INDICATING BEST CHANCES FOR SNOW WILL BE OVER
CENTRAL NY WITH SMALLER CHANCES TOWARD NORTHEAST PA.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
GFS AND ECMWF ARE IN REASONABLY GOOD AGREEMENT WITH THE OVERALL
PATTERN DURING THIS PERIOD INDICATING NORTHWEST FLOW WITH A SERIES
OF WEAKLY ORGANIZED CLIPPER SYSTEMS LIKELY ALONG WITH SOME LAKE EFFECT
SNOW. HOWEVER AT THIS POINT THERE IS NO INDICATION FOR ANY MAJOR
SYNOPTIC SCALE SYSTEMS THAT WOULD TAP GULF MOISTURE. TIMING OF THESE
INDIVIDUAL SYSTEMS WILL BE DIFFICULT BEYOND SUNDAY... BUT RIGHT NOW
THE BEST CHC FOR A WEAKLY ORGANIZED CLIPPER-LIKE SYSTEM COULD BE NEW
YEAR`S EVE INTO NEW YEAR`S DAY... WHICH WOULD BE FOLLOWED BY AN
ENHANCED PERIOD OF LAKE EFFECT SNOW. TEMPERATURES THROUGH THE PERIOD
WILL AVERAGE NEAR TO BELOW NORMAL... WITH HIGHS MAINLY IN THE MID
20S TO LOWER 30S AND LOWS IN THE TEENS. HAVE GONE WITH HPC GUIDANCE
THROUGH THE PERIOD INDICATING BEST CHANCES FOR SNOW WILL BE OVER
CENTRAL NY WITH SMALLER CHANCES TOWARD NORTHEAST PA.
&&
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
LRG STORM STILL DEEPENING AS IT MVES UP THE NJ CST. THIS WILL KEEP
SNOW OVER THE AREA...AND SOME MIXED PCPN AT AVP...THRU AT LEAST
12Z. CIGS AND VSBYS WILLVARY WIDELY AS BANDS OF HEAVIER PCPN MVE
THRU...BUT WILL BE IFR ON BALANCE...WITH OCNL PDS OF BOTH LIFR AND
MVFR. CONDS WILL IMPROVE A BIT AFT 12Z AS THE UPR LOW AXIS MVES BY
AND THE AREA IS ON THE BACKSIDE OF THE STORM. HWVR...PERSISTENT
LGT SNOW WILL KEEP CIGS AND VSBY AT LEAST IN THE MVFR CAT THRU THE
END OF THE PD.
OUTLOOK...
THUR NGT...MVFR/IFR IN SNOW SHOWERS ESPECIALLY OVER CENTRAL NY.
FRI...MAINLY VFR...MVFR/IFR POSSIBLE NORTHERN TERMINALS IN LAKE
EFFECT SNOW.
SAT...ANOTHER POSSIBLE WINTER SYSTEM AND THUS POSSIBLE IFR/MVFR.
SUN/MON...MVFR/IFR POSSIBLE AT FOR CNY TERMINALS IN DEVELOPING LAKE
EFFECT SN.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...WINTER STORM WARNING UNTIL 1 PM EST THIS AFTERNOON FOR
PAZ038>040-043-044-047-048-072.
NY...WINTER STORM WARNING UNTIL 1 PM EST THIS AFTERNOON FOR NYZ009-
015>018-022>025-036-037-044>046-055>057-062.
&&
$$
SYNOPSIS...CMG
NEAR TERM...CMG/MLJ
SHORT TERM...DGM
LONG TERM...PVN
AVIATION...DGM
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
1236 AM EST THU DEC 27 2012
.SYNOPSIS...
A POTENT WINTER STORM WILL IMPACT THE ENTIRE REGION TONIGHT
THROUGH THURSDAY NIGHT PRODUCING WIDESPREAD HEAVY SNOWS WITH
AMOUNTS OVER A FOOT. GUSTY WINDS WILL ALSO OCCUR ALONG THE WESTERN
SLOPES OF THE GREEN MOUNTAINS AND IN THE SAINT LAWRENCE VALLEY,
AND THIS MAY CAUSE AREAS OF BLOWING SNOW. SNOW SHOWERS WILL
CONTINUE ACROSS THE NORTHERN MOUNTAINS ON FRIDAY AS THE STORM
MOVES AWAY FROM THE REGION. THE WEEKEND WILL BE SEASONABLY COLD,
WITH A CONTINUED CHANCE OF LIGHT SNOW IN THE MOUNTAINS.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 1227 AM EST THURSDAY...EVERYTHING STILL ON TRACK WITH ONLY
MINOR ADJUSTMENTS MADE TO GOING FORECAST. LOW PRESSURE IS LOCATED
NEAR TIP OF SOUTHERN NEW JERSEY AT 992 MB. GREATEST PRESSURE FALLS
ARE ALONG THE NEW JERSEY COASTLINE...CONTINUING TO SUGGEST A TRACK
TOWARDS LONG ISLAND OVERNIGHT. SNOW HAS MADE IT AS FAR NORTH AS
BURLINGTON AND MASSENA AND WILL OVERSPREAD REST OF NORTHERN
VERMONT OVER NEXT COUPLE OF HOURS. INTENSITY OF SNOW INCREASES
QUICKLY AFTER ONSET. HAVE SEEN WIDESPREAD 1-2" PER HOUR RATES
ACROSS NEW YORK AND SOUTHERN VERMONT AS WELL AS POINTS FURTHER
SOUTH. LATEST HRRR CONTINUES TO SHOW THIS HEAVY BAND MOVING
NORTHWARD...WITH HEAVIEST PRECIP THROUGH 8Z IN SOUTHERN
AREAS...5-10Z IN THE CHAMPLAIN VALLEY AND NORTHERN VERMONT...AND
7-13Z ACROSS NORTHERN NEW YORK. ALSO OF NOTE...DOWNSLOPE WINDS
GUSTING INTO THE 20S ACROSS SOUTHWEST VERMONT.
EARLIER DISCUSSION FROM 642 PM EST...
EVERYTHING REMAINS ON TRACK...AND ONLY MINOR ADJUSTMENTS WERE
MADE. HAD TO DROP TEMPERATURES SLIGHTLY THIS EVENING...WITH
WIDESPREAD TEENS ACROSS THE REGION. LOWS WILL BE REACHED OVER THE
NEXT COUPLE OF HOURS...AND THEN SLOWLY RISE OVERNIGHT.
OTHERWISE...TRIED TO NARROW DOWN THE START TIME FOR SNOW ACROSS
THE AREA. PRIMARY LOW NOW LOCATED OVER WEST VIRGINIA WITH A
SECONDARY LOW DEVELOPING NEAR WAKEFIELD VIRGINIA. SECONDARY LOW
WILL TAKE OVER DURING THE REST OF THE EVENING AND PROGRESS TO NEAR
DELAWARE BY 03Z...NEW YORK CITY BY 09Z....AND THEN LONG ISLAND BY
12Z. JUDGING BY CURRENT OBSERVATIONS...SNOW HAS NOW REACHED AS FAR
NORTH AS THE MID-HUDSON VALLEY...THE CENTRAL MOHAWK VALLEY...AND
THE SHORES OF LAKE ONTARIO IN NEW YORK...WITH A SLOW NORTHWARD
PROGRESSION. SHOULD BE INTO THE ADIRONDACKS AND SOUTHERN VERMONT
AROUND 02Z (9 PM)...THE CHAMPLAIN VALLEY AROUND 04Z (11 PM)...AND
THE NORTHEAST KINGDOM AROUND 05Z (MIDNIGHT). HEAVIEST SNOW WITH
INITIAL BAND OF WARM AIR ADVECTION PRECIPITATION WILL LIKELY OCCUR
BETWEEN 07Z AND 10Z (2 AM AND 5 AM) WHERE RATES OF 1-2 INCHES PER
HOUR ARE POSSIBLE...ESPECIALLY IN THE SOUTHEAST- UPSLOPE FAVORED
LOCATIONS. DOWNSLOPE WINDS WILL ALSO BE INCREASING ACROSS THE
SOUTHERN GREENS WITH GUSTS UP TO 40 MPH POSSIBLE IN EASTERN
ADDISON AND RUTLAND COUNTIES BETWEEN 06Z AND 10Z (1 AM AND 5 AM).
THIS WILL CREATE SOME WARMING AND DRYING IN THOSE AREAS...AND
COMBINED WITH SOME WARMING ALOFT (750-800 MB) AS INDICATED BY
LATEST RAP AND NAM...WILL LIKELY SEE SOME SLEET MIX IN ACROSS
RUTLAND AND WINDSOR COUNTIES AFTER 07Z...AND ESPECIALLY AFTER 10Z.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/...
AS OF 325 PM EST WEDNESDAY...GONNA BE A BUSY DAY THURSDAY. LOTS OF
SNOW. THE STORM WILL TRACK NORTHEAST AND CUT ACROSS CAPE COD (OR
VERY NEAR IT) BY LATE IN THE AFTERNOON. THIS PUTS THE NORTH
COUNTRY INTO A SWEET SPOT FOR THE HEAVIEST QPF. THE DRY SLOT JUST
WONT GET THIS FAR NORTH, AND AS THE LOW MOVES OFF TO THE EAST,
WE`LL BE IN THE PIVOT ZONE INTO THE AFTERNOON.
EXCELLENT DYNAMICS AND SNOW GROWTH MAXED WITH UPWARD MOTION
SHOULD RESULT IN A PERIOD OF HEAVY SNOW MOST EVERYWHERE. THINKING
THE PRIMARY TIME WILL BE 6AM TO NOON, WITH RATES OF 1-2" PER HOUR.
CAN`T RULE OUT LOCALIZED MESOSCALE BAND WITH EVEN A LITTLE BIT
MORE. LIQUID QPF WILL BE QUITE IMPRESSIVE. SPENT A GOOD DEAL OF
TIME TRYING TO ACCOUNT FOR OROGRAPHIC EFFECTS AS WELL. BY THE TIME
WE GET TO THURSDAY NIGHT, MOST OF US WILL SEE ON THE ORDER OF 1 TO
1.5" OF LIQUID EQUIVALENT. SHADOWING WILL MAKE THE NUMBER A LITTLE
LOWER IN THE NORTHEAST KINGDOM AND WESTERN SLOPES OF THE SOUTHERN
GREENS, BUT THEN THAT ON THE FLIP SIDE, ORGRAPHICS WILL HELP ON
THE EASTERN SIDES OF THE GREENS AND DACKS. HAVE INCREASED THE SNOW
TOTALS A FEW INCHES ACROSS THE BOARD -- THINKING 12 TO 17 INCHES,
WITH THE JACKPOT LOCATIONS SEEING ABOUT 20". EVEN THOSE WHO SEE
THE LEAST WILL GET ABOUT 8", WHICH IS NOT SHABBY.
WINDS WILL CONTINUE TO BE GUSTY THE FIRST HALF OF THURSDAY ALONG
THE WESTERN SLOPES. ALSO HAVE TO WATCH FOR STRONG NORTHEAST WINDS
FUNNELLING DOWN THE ST LAWRENCE VALLEY. DONT THINK THEY`LL HIT
WIND ADVISORY CRITERIA, BUT STILL THEY`LL HAVE SUSTAINED WINDS 15
TO 25 MPH WITH HIGHER GUSTS -- AND THAT WILL CAUSE A CONSIDERABLE
AMOUNT OF DRIFTING/BLOWING SNOW OUT THERE. HAVE ADDED THAT WORDING
TO THE FORECAST.
SNOW WILL BEGIN TO TAPER OFF IN THE EVENING, THOUGH LIGHT SNOWS
WILL CONTINUE ALL NIGHT. AS THE LOW PUSHES EAST OF HERE, WINDS
WILL CLOCK AROUND TO NORTHWEST. MOISTURE WILL BE SLOW TO LEAVE, SO
THE NORTHWEST WINDS AND THAT MOISTURE WILL RESULT IN A GOOD AMOUNT
OF OROGRAPHICS, SO THE HIGHER TERRAIN WILL PICK UP A FEW
ADDITIONAL INCHES OF SNOW (AT LEAST) ON FRIDAY.
FINALLY TAPER POPS DOWN TO CHANCE LEVELS BY FRIDAY NIGHT, THOUGH A
WEAK SYSTEM APPROACHING FROM THE WEST MAY SPARK A LITTLE BIT OF
LIGHT SNOW/FLURRIES.
QUICK NOTE ON TEMPERATURES -- PRIMARILY KEPT TO THE COOLER SIDE OF
GUIDANCE FOR THE ENTIRE TIME.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 342 PM EST WEDNESDAY...OVERALL LITTLE CHANGE FROM PREVIOUS
COUPLE OF FCSTS...WITH BLW NORMAL TEMPS AND PRECIP EXPECTED FOR
DAYS 4 THRU 7. THE EXTENDED FCST CHALLENGE WL BE TIMING/MAGNITUDE
OF ARCTIC AIRMASS ACRS OUR CWA EARLY NEXT WK. WL CONT TO MENTION
LOW CHC POPS FOR LATE SAT INTO SUNDAY ASSOCIATED WITH MID/UPPER
LVL TROF AND SOME 850 TO 500MB RH. LATEST TRENDS HAVE BEEN FOR
LESS RH AND QPF ACRS OUR CWA...BUT ECMWF IS A BIT CLOSER TO THE
COAST WITH SFC LOW PRES AND ENOUGH MOISTURE MAY MOVE BACK INTO OUR
CWA FOR SOME LIGHT SNOW. OTHERWISE...ECMWF/GEM SHOW MID/UPPER LVL
TROF DEVELOPING ACRS EASTERN CANADA WITH A MAINLY DRY NW FLW
ALOFT. HOWEVER...A WELL DEFINED ARCTIC BOUNDARY WL PUSH ACRS OUR
CWA EARLY NEXT WEEK...ALONG WITH A RIBBON OF ENHANCED MOISTURE.
THIS MOISTURE...ALONG WITH SOME ADDITIONAL MOISTURE FROM THE GREAT
LAKES WL HELP IN PRODUCING SOME SNOW SHOWERS ACRS OUR CWA ON
MONDAY INTO TUES. IN ADDITION...MUCH COLDER TEMPS WL ADVECT BACK
INTO OUR CWA FOR NEXT WK. STILL SOME UNCERTAINTY WITH REGARDS TO
TIMING OF THIS FEATURE...AS GFS IS 6 TO 12 HRS SLOWER AND SHOWS
THE COLDEST TEMPS ACRS OUR CWA ON WEDS. TIMING OF BOUNDARY WL MAKE
A HUGE DIFFERENCE IN TEMPS FROM NEAR 30F AT BTV IF THE GFS IS
RIGHT TO LOWER TEENS IF THE ECMWF/GEM ARE CORRECT ON TUES. GIVEN THE
DEVELOPMENT OF A LARGE SCALE TROF AND DEEP CYCLONIC FLW ACRS THE
NE CONUS...WL TREND TWD THE COLDER ECMWF/GEM FOR NEXT WEEK...AND
MENTION HIGHS ONLY IN THE TEENS/L20S WITH LOWS MAINLY IN THE
SINGLE DIGITS/LOWER TEENS. IF SFC HIGH PRES BUILDS INTO THE
REGION...FASTER THAN PROGGED...THEN WINDS WL DECREASE AND
OVERNIGHT LOWS WL NEED TO BE ADJUSTED DOWN BY 5 TO 10 DEGREES. ITS
ALWAYS DIFFICULT TO DETERMINE AMOUNT OF CAA AND IMPACTS ACRS OUR
CWA IN THE DAY 5 TO 7 RANGE. TODAY IS A GREAT EXAMPLE OF TRYING TO
PREDICT THE COLD AIR...AS TEMPS STRUGGLED MAINLY IN THE TEENS.
&&
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
THROUGH 00Z FRIDAY...SNOW TO MOVE IN TO ALL TAF SITES 03-05Z,
LOWERING CONDITIONS TO LIFR TO IFR FOR ALL OF TAF PERIOD. HEAVIER BURSTS
POSSIBLE 09-14Z AT HEIGHT OF STORM. AFTER 14Z WILL BEGIN TO SEE
SLOW IMPROVEMENT...BUT STILL IFR. POTENTIAL FOR LAYER OF NEAR TO
ABOVE FREEZING AIR TO MOVE IN TO SOUTHERN VERMONT 10-15Z...AND
PRODUCE SLEET AT KRUT. TEMPERATURE PROFILE RIGHT ON THE EDGE...AND
COULD EASILY STAY ALL SNOW IF TEMPERATURES REMAIN COOL ENOUGH.
EAST TO SOUTHEAST LOW LEVEL JET TO MOVE INTO AREA OVERNIGHT...WITH
KRUT LIKELY TO EXPERIENCE STRONGEST WIND GUSTS 20-35 KTS. VALLEY
CHANNELING AT KMSS WILL PRODUCE GUSTS TO 20-25 KTS. ELSEWHERE
STRONGER WINDS LESS FAVORABLE... REMAINING SITES STILL TO SEE
15-20 KTS.
OUTLOOK 00Z FRIDAY THROUGH MONDAY...
00Z FRIDAY-00Z SATURDAY...LOW WILL MOVE INTO THE GULF OF
MAINE...SHIFTING SURFACE WINDS TO NORTHWEST. SNOW SHOWERS TO
CONTINUE ESPECIALLY IN FAVORED UPSLOPE AREAS...AND HIGHER
ELEVATION SITES KMPV/KSLK LIKELY WILL SEE CONTINUED MVFR TO IFR
CIG/VIS. MOSTLY VFR ELSEWHERE...ALTHOUGH FRESH SNOW AND GUSTY
WINDS WILL PRODUCE SOME BLOWING/DRIFTING.
00Z SATURDAY THROUGH 00Z SUNDAY...SFC HIGH PRES SLOWLY BUILDS INTO
OUR TAF SITES BY 12Z SATURDAY. SOME LEFTOVER MTN SNOW SHOWERS AT
MPV/SLK WL CREATE OCCASIONAL MVFR CONDITIONS THRU 06Z SAT...BEFORE
DISSIPATING WITH VFR CONDITIONS DEVELOPING AFT 06Z SATURDAY.
00Z SUNDAY THROUGH MONDAY...MAINLY VFR CONDITIONS WITH A CHANCE OF
MVFR SNOW SHOWERS ACROSS CENTRAL AND SOUTHERN AREAS SATURDAY NIGHT
AS LOW PRESSURE MOVES EAST ACROSS THE MID-ATLANTIC STATES.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...WINTER STORM WARNING UNTIL 7 AM EST FRIDAY FOR VTZ001>012-
016>019.
NY...WINTER STORM WARNING UNTIL 7 AM EST FRIDAY FOR NYZ026>031-034-
035-087.
&&
$$
SYNOPSIS...NASH
NEAR TERM...RJS/MUCCILLI
SHORT TERM...NASH
LONG TERM...TABER
AVIATION...HANSON
AREA FORECAST DISCUSSION
NWS GRAND FORKS ND
914 PM CST FRI DEC 28 2012
.DISCUSSION...
MAIN ADJUSTMENTS THIS EVENING WERE TO LOWER TEMPS IN THE NORTHWEST
AND PUT IN A WIND CHILL ADVISORY. SAT LOOP SHOWS CLOUDS HAVE
CONTINUED OVER MUCH OF THE CWA FOR THE EARLY PART OF THE
EVENING...AND THERE HAVE EVEN BEEN A FEW ISOLATED FLURRIES.
HOWEVER...CLEARING IS ALREADY STARTING IN THE FAR NORTHWESTERN
CWA...WITH WESTERN BENSON COUNTY ALREADY DROPPING BELOW ZERO AND
TEMPS IN THE TEENS BELOW ZERO ALREADY OVER NORTHWESTERN ND AND
SOUTHEASTERN SASKATCHEWAN. THE 00Z NAM AND 01Z RAP BOTH BRING
TEMPS INTO THE TEENS BELOW ZERO IN AT LEAST PART OF THE
NORTHWESTERN CWA BY MORNING. THINK THAT THE RAP IS BRINGING THE
BITTER COLD AIR A BIT TOO FAR SOUTH GIVEN THE MORE WESTERLY
COMPONENT TO THE WIND SO LEANED TOWARDS THE NAM WHICH DOES NOT
BRING THE SUPER COLD AIR AS FAR SOUTH AS VALLEY CITY.
HOWEVER...THINK THAT DEVILS LAKE BASIN SHOULD CLEAR OUT AS THE
NIGHT GOES ON AND DROP INTO THE TEENS BELOW ZERO. RUGBY ALREADY
HAS A 25 BELOW WIND CHILL...AND WITH LOWER TEMPS AND WINDS IN THE
4 TO 8 KT RANGE...THINK THAT ADVISORY CRITERIA WILL BE REACHED IN
THE DEVILS LAKE BASIN LATE TONIGHT INTO TOMORROW MORNING. WILL PUT
OUT AN ADVISORY SHORTLY.
&&
.AVIATION...
CEILINGS HAVE BEEN ALL OVER THE PLACE BUT THE WESTERN TAF SITES
HAVE IMPROVED TO VFR AND KTVF SHOULD GO UP SHORTLY. THINK THAT ALL
BUT KBJI WILL BE VFR FOR THE REST OF THE NIGHT AS A WEAK SFC
BOUNDARY MOVES THROUGH AND HIGH PRESSURE BUILDS IN. WINDS WILL BE
WESTERLY BUT UNDER 12 KTS.
&&
.PREV DISCUSSION... /ISSUED 307 PM CST FRI DEC 28 2012/
SHORT TERM...
MODELS IN GOOD AGREEMENT AND WENT WITH A BLENDED SOLN FOR THIS FCST
PACKAGE.
MAIN CHALLENGES EARLY IN THE PERIOD REMAIN CLOUD COVER AND
TEMPERATURES. SATELLITE IMAGERY SHOWS CLOUD COVER OVER MOST OF THE
AREA WITH SOME CLEAR POCKETS IN NW MINNESOTA. LOW CONFIDENCE IN RUC
MODEL REGARDING CLOUD TRENDS THRU TONIGHT AND FORECAST SOUNDINGS A
BETTER INDICATOR OF TRENDS SO CONTINUED MOSTLY CLOUDY
SKIES...ESPECIALLY IN THE NORTH. GUIDANCE REASONABLE WITH TEMP
TRENDS CONSIDERING WEAK HIGH PRESSURE MOVING IN OVERNIGHT...AND WILL
SEE LOWS APCHING -10F IN NW ZONES WITH COLD ADVECTION AND CLEARING
SKIES. OTHERWISE...RETURN FLOW LATE SAT INTO EARLY SUN WILL HELP
BOOST TEMPS AHEAD OF NEXT SYSTEM.
SFC LOW PRESSURE IS FCST TO DEVELOP ACROSS WRN ND...AND A TRAILING
COLD FRONT IS EXPECTED TO IMPACT THE AREA SUN AND MON. COOLER AIR
BEHIND SYSTEM WILL REMAIN IN PLACE THRU THE END OF THE PERIOD...WITH
ONLY LIGHT PCPN EXPECTED WITH THE SYSTEM.
LONG TERM (TUE NIGHT THROUGH FRI)...
ALL LONG RANGE MODELS AGREE IN KEEPING AREA IN NORTH-NORTHWESTERLY
FLOW ALOFT THROUGH NEXT WEEK WITH PERIODIC SURGES OF COLD AIR. HIGH
PRESSURE WILL BE OVER THE AREA MON NIGHT...THEN BRIEF WARM UP TUES
AHEAD OF NEXT SHORT WAVE TO DROP SOUTH FOR WED. EXPECT A LITTLE
LIGHT SNOW WITH MID WEEK WAVE TUES NIGHT-WED BEFORE HIGH SETTLES IN
WED NIGHT-THU. TEMPS AT NIGHT HIGHLY DEPENDENT ON CLOUD COVER SO
STUCK WITH ALL BLEND TEMPS THRU THE PD...EXCEPT KEPT A TAD COLDER
PER PREV FCST ON WED NIGHT AS 850 MB TEMPS DROP TO -16 TO -22C
ACROSS THE REGION. SOMEWHAT MILDER AIR FCST TO MOVE IN FRIDAY AHD OF
NEXT SHORT WAVE WITH 12Z ECMWF/12Z GFS SHOWING 850 MB TEMPS RISING
TO AROUND ZERO. ANY PRECIP THRU THE PD AND EVEN BEYOND LOOKS VERY
LIGHT.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...WIND CHILL ADVISORY UNTIL 11 AM CST SATURDAY FOR NDZ006>008-014-
015-024-026-054.
MN...NONE.
&&
$$
JR
AREA FORECAST DISCUSSION
NWS BISMARCK ND
820 PM CST FRI DEC 28 2012
.DISCUSSION...UPDATE THIS EVENING TO ISSUE A WIND CHILL ADVISORY
ACROSS THE NORTH...AND INTO THE EAST CENTRAL COUNTIES TONIGHT INTO
MID MORNING SATURDAY.
HIGH PRESSURE OVER SOUTHEAST SASKATCHEWAN IS FORECAST TO MOVE TO
NEAR BOTTINEAU BY 12Z SATURDAY. CURRENT WIND CHILL TEMPS BETWEEN
20 AND 24 BELOW. THE RUC13 CONTINUES TO TREND COLDER WITH
TEMPERATURES OVERNIGHT...BETWEEN 10 AND 18 BELOW ZERO WITH WINDS
OF AROUND 5 TO 8 MPH. GIVEN THE TRENDS SINCE 00Z..CONCUR WITH THIS
IDEA...ESPECIALLY WITH MOSTLY CLEAR SKIES OVER MUCH OF SOUTHERN
SASKATCHEWAN AND NORTHERN NORTH DAKOTA. THUS HAVE ISSUED A WIND
CHILL ADVISORY FOR THE NORTHERN COUNTIES FROM NOW THROUGH 16Z
SATURDAY. WARM AIR ADVECTION BEGINS IN THE WEST LATE TONIGHT...AND
WARMING TEMPS SHOULD LEAD TO A WEST TO EAST CANCELLATION SATURDAY
MORNING.
FURTHERMORE...HAVE FOLLOWED THE TRENDS AFTER MIDNIGHT AND WIND
CHILL TEMPS TO 30 BELOW MOVE SOUTHEAST INTO EAST CENTRAL NORTH
DAKOTA. HAVE ISSUED A WIND CHILL ADVISORY HERE FROM 08Z THROUGH
16Z.
UPDATES TO ALL TEXT PRODUCTS FORTHCOMING.
&&
.AVIATION...AT 02Z...MOSTLY CLEAR SKIES AND VFR CONDITIONS AT ALL
AERODROMES. OVERALL...EXPECT SCT TO ISOLATED BKN VFR CIGS NEXT
24HR. WILL MONITOR SATELLITE FOR AREAS OF ANY MVFR CIGS OVERNIGHT...BUT
NOT EXPECTING ANYTHING MORE THAN AN ISOLATED AREAS PASSING THROUGH
FROM TIME TO TIME.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY FROM 2 AM TO 10 AM CST SATURDAY FOR
NDZ021>023-025-036-037.
WIND CHILL ADVISORY UNTIL 10 AM CST SATURDAY FOR NDZ001>005-
009>013.
&&
$$
DISCUSSION/AVIATION...KS
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
509 PM EST THU DEC 27 2012
.SYNOPSIS...
A WEAK AREA OF HIGH PRESSURE WILL SLOWLY PUSH TO THE EAST
OVERNIGHT. AN UPPER LEVEL DISTURBANCE AND ITS ASSOCIATED SURFACE
BOUNDARIES WILL BRING A MIX OF PRECIPITATION TO THE REGION FRIDAY
NIGHT AND EARLY SATURDAY.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
SATELLITE SHOWING THAT INCREASING CLOUD BREAKS NOW BEGINNING TO
FILL BACK IN. CURRENT THINKING IS THAT THE RETURN FLOW BEHIND THE
DEPARTING SURFACE HIGH WILL ALLOW ADDITIONAL MOISTURE AHEAD OF THE
NEXT SYSTEM APPROACHING FROM THE SOUTHERN PLAINS AND THAT BREAKS
WILL CONTINUE TO FILL IN. CURRENTLY HAVE A TIGHT GRADIENT OF
OVERNIGHT LOWS FROM THE MID 20S SOUTH TO THE UPPER TEENS NEAR
WAPAKONETA. WILL HAVE TO MONITOR THE CLOUDS IN THE NORTH...AS IF
BREAKS WORK IN...TEMPS WILL PLUMMET WITH CLOUD COVER AND VERY
LIGHT WINDS. GENERALLY WENT ON THE LOWER END OF MOS GUIDANCE
SOLUTIONS.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
WHILE A FAIR AMOUNT OF MID AND HIGH CLOUDS THROUGH THE DAY ON
FRIDAY...WARMER AIR BEGINST TO WORK ESPECIALLY INTO THE SOUTHERN
FCST AREA...WHICH WILL ALLOW LOW 40S IN THE SOUTH...BUT HIGHS
STILL BELOW OR JUST AT FREEZING IN THE NORTH.
THE NEXT WEATHER MAKER WILL COME ON FRIDAY NIGHT...AS A DEVELOPING
UPR LEVEL TROUGH WILL ADVANCE FROM THE MS VALLEY AND PIVOT ENE
THROUGH THE UPPR OH VALLEY. GFS IS FURTHER NORTH AND A LITTLE
SLOWER AND DEEPER WITH THE LOW THAN THE 12Z ECMWF...WTH THE NAM
THE OUTLIER IN POSITIONING AND TIMING. SOLUTION IS A BLEND BETWEEN
THE GFS/ECMWF...SLIGHTLY FAVORING THE 12Z ECMWF. GFS QPF HAS SOME HEAVIER
PRECIP AMOUNTS TO THE NW OF THE SFC LOW...WHEREAS THE ECMWF HAS
THE HEAVIEST PRECIPITATION IN THE WARMER AIR NEAR AND SOUTH OF THE
LOW. HAVE ALSO SIDED CLOSER TO ECMWF FOR QPF. THE TRICKY PART IS
THE TIMING OF THE PRECIP WITH SOME WAA EXPECTED NEAR THE OHIO
RIVER AND A WARM NOSE PUSHING INTO THE PORTSMOUTH AREA...WHERE THE
HEAVIEST QPF IS EXPECTED TO BE. THE HEAVIEST PRECIP APPEARS TO BE
JUST ON EITHER SIDE OF THE 06Z TIMEFRAME...SO IF LOW LEVELS AND
SFC ARE COLD ENOUGH...ADVISORY CRITERIA FOR SNOW MAY BE MET
ESPECIALLY NEAR THE I-71 CORRIDOR AND POSSIBLY TO THE SOUTHEAST.
NEED MORE CONFIDENCE FOR SUCH ISSUANCE...SO NO PRODUCT ISSUANCES
AT THIS TIME.
SYSTEM FAIRLY QUICK TO PUSH EAST OF FCST AREA...WITH SFC BOUNDARY
AND COLDER AIR TO WORK IN DURING THE DAY ON SATURDAY WITH
LINGERING SNOW SHOWERS.
SKIES WILL BE SLOW TO CLEAR FOR SAT NIGHT...SO WHILE CAA WORKING
IN...WON`T BE COMBINED WITH RADIATIONAL COOLING OVER ANY NEW SNOW
COVER. GENERALLY NER 20 TO LOW 20S FOR LOWS.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
SURFACE HIGH PRESSURE WILL BEGIN TO BUILD INTO THE OHIO VALLEY
SUNDAY MORNING BEHIND A DEPARTING UPPER LEVEL TROUGH. CLOUDS WILL
SLOWLY DIMINISH FROM WEST TO EAST THROUGH THE DAY GIVING WAY FOR A
BRIEF PERIOD OF SOME SUNSHINE. WITH A COLDER AIRMASS OVER THE
REGION...TEMPERATURES WILL REMAIN BELOW NORMAL WITH HIGHS IN THE
UPPER 20S TO LOWER 30S AND LOWS SUNDAY NIGHT IN THE TEENS TO LOWER
20S. RETURN FLOW AROUND THE BACKSIDE OF THE HIGH WILL ALLOW FOR A
RETURN TO MORE SEASONAL TEMPERATURES BY MONDAY.
LAST FEW MODEL RUNS HAVE SLIGHTLY SPED UP THE APPROACH OF A COLD
FRONT FOR MONDAY EVENING/OVERNIGHT. SOUTHWESTERLY FLOW WILL DRAW
INCREASING MOISTURE IN FROM THE SOUTH DURING THE DAY. MODELS HAVE
BEEN TRENDING FURTHER NORTH AND EAST WITH PRECIPITATION OUT AHEAD OF
THE FRONT...SO INTRODUCED POPS FOR OUR CWA EARLIER IN THE DAY.
CHANCE POPS WILL CONTINUE MONDAY NIGHT INTO TUESDAY AS THE FRONT
MOVES THROUGH THE AREA AND AN UPPER TROUGH APPROACHES. EXPECT
MAINLY LIGHT SNOW FROM THIS SYSTEM BUT THERE MAY BE SOME LIGHT RAIN
MIXED IN MONDAY AFTERNOON IN THE SOUTH.
HIGH PRESSURE AND ANOTHER COLD AIRMASS WILL SETTLE INTO THE REGION
BY THE MIDDLE OF THE WEEK. WEAK SYSTEM OVER THE GREAT LAKES COULD
PRODUCE SOME SNOW SHOWERS LATE IN THE PERIOD...SO WENT WITH SLIGHT
POPS LATE WED NIGHT INTO THURSDAY.
&&
.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
MVFR CLOUDS ARE PERSISTING ACROSS OUR AREA THIS AFTERNOON ALTHOUGH
SOME PARTIAL CLEARING AND SOME VFR CIGS ARE JUST OFF TO THE WEST.
SOME OF THIS PARTIAL CLEARING COULD AFFECT THE WESTERN TAF SITES
THROUGH THIS AFTERNOON...BUT GIVEN THE NORTHERLY LOW LEVEL
FLOW...WILL HANG ON TO THE MVFR CIGS THROUGH THE DAY. BETTER
CLEARING PUSHING DOWN INTO NORTHWEST OHIO IS BEING PICKED UP
FAIRLY WELL BY THE 12Z NAM...AND THIS IS FORECAST TO WORK ITS WAY
DOWN TOWARD CENTRAL OHIO THROUGH LATE AFTERNOON AND EARLY EVENING.
HOWEVER...BY THEN THE LOW LEVEL FLOW BEGINS TO SWING AROUND TO THE
SOUTHEAST AND THEN SOUTH OVERNIGHT SO NOT SURE EXACTLY HOW FAR
THE CLEARING WILL MAKE IT. ON THE OTHER HAND...AS THE LOW LEVEL
FLOW DOES BECOME MORE SOUTHERLY...WE COULD ALSO SEE SOME EROSION
OF THE LOW LEVEL CLOUDS ACROSS THE AREA. ALL OF THIS MAKES FOR A
FAIRLY LOW CONFIDENCE CLOUD FORECAST TONIGHT. WITH BOTH THE NAM
AND LATEST RAP HANGING ON TO SOME LOW LEVEL MOISTURE THROUGH MUCH
OF THE NIGHT...HAVE OPTED TO KEEP THINGS PESSIMISTIC AND HOLD ON
TO SOME MVFR CIGS THROUGH THE NIGHT. ON THE FLIP OF THAT...IF WE
DO GET SOME CLEARING...WE COULD SEE SOME MVFR BR DEVELOP LATER
TONIGHT GIVEN THE LIGHT WINDS.
OUTLOOK...MVFR/IFR CEILINGS AND VISIBILITIES POSSIBLE FRIDAY
NIGHT INTO SATURDAY NIGHT AND THEN AGAIN MONDAY AFTERNOON INTO
TUESDAY.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.
&&
$$
SYNOPSIS...JDR
NEAR TERM...JDR
SHORT TERM...JDR
LONG TERM...KURZ
AVIATION...JGL
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
154 PM EST THU DEC 27 2012
.SYNOPSIS...
LOW PRESSURE SYSTEM EXITS EAST TODAY. ANOTHER LOW PRESSURE SYSTEM
FRIDAY NIGHT AND SATURDAY...WITH MORE MIXED PRECIPITATION...CHANGING
TO SNOW OVERNIGHT SATURDAY AND SUNDAY.
&&
.NEAR TERM /THROUGH FRIDAY/...
UPDATE...
NO CHANGES THIS AFTERNOON TO PREVIOUS GRIDS.
PREVIOUS DISCUSSION...
RADAR AND MODELS SHOWING LIGHT SNOW OR FREEZING DRIZZLE MOVING INTO
THE EASTERN MOUNTAINS WHILE DIMINISHING ACROSS THE WESTERN HALF OF
THE AREA THIS MORNING. LOW CLOUDS WILL PERSIST OVER A SHALLOW
SATURATED LAYER TODAY...LIFTING TONIGHT. HOWEVER...HIGH LEVEL
CLOUDS ASSOCIATED WITH A FAR AWAY SYSTEM WILL COVER PORTIONS OF OUR
SKIES THROUGH THIS EVENING.
VERY COLD AIR CONTINUES TO FILTER IN UNDER WEST NORTHWEST FLOW WITH
H850 TEMPS WARMING FROM MINUS 9C TO MINUS 5C BY 18Z THIS AFTERNOON
AND TONIGHT. THEREFORE...WITH CLOUDS EXPECTED AND VERY COLD AIR MASS
IN PLACE...TODAYS TEMPERATURES WILL REMAIN AT OR BELOW
FREEZING...EXCEPT FOR POCKETS JUST ABOVE OVER THE LOWLANDS. THESE
LOW TEMPERATURES WILL KEEP ANY WET SURFACE FROZEN...TO PRODUCE BLACK
ICE WHERE WATER USUALLY DRAINS FROM SLOPES...AND ON EXPOSED BRIDGES
AND OVERPASSES. DRIVERS SHOULD EXERCISE CAUTION WHEN TRAVELING
TODAY.
FOR TONIGHT...DRIER CONDITIONS WITH LESS CLOUDS. LOWS GENERALLY IN
THE MID 20S LOWLANDS...RANGING TO THE TEENS HIGHER ELEVATIONS.
HOWEVER...WINDS WILL DIMINISH TONIGHT...KEEPING SIMILAR WINDCHILL AS
TODAY.
GUSTY WINDS WILL PRODUCE WINDCHILL IN THE 20S LOWLANDS...RANGING
INTO NEAR ZERO AT THE HIGHEST PEAKS NORTHEAST MOUNTAINS.
A WIND WIND ADVISORY REMAINS IN EFFECT FOR POCAHONTAS COUNTY THROUGH
AT LEAST 1 PM THIS AFTERNOON.
WENT WITH A BLEND OF THE GMOS AND RUC MODELS FOR TEMPERATURES
THROUGH THE PERIOD.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AN UPPER LEVEL TROUGH WILL USHER IN THE NEXT SNOW PRODUCING SYSTEM
EARLY ON SATURDAY MORNING. PRECIPITATION WILL START OUT AS RAIN IN
THE SOUTH AND PERHAPS SNOW IN THE NORTH SATURDAY MORNING BUT
TEMPERATURES WILL REBOUND ABOVE FREEZING DURING THE DAY SATURDAY
AS SNOW IN THE NORTH CHANGES OVER TO RAIN BEFORE SWITCHING BACK TO
ALL SNOW AGAIN SATURDAY NIGHT. A COLD AIR MASS WILL THEN SETTLE
OVER THE AREA WITH UPSLOPE WINDS HELPING TO ENHANCE ACCUMULATIONS
OVERNIGHT SATURDAY. ALL SAID AND DONE...WE MAY SEE 1 TO 3 INCHES
IN MOST LOCATIONS MAYBE A TAD MORE OR LESS WHILE THE MOUNTAINS
WILL SEE 2 TO 4 INCHES. AS ALWAYS...FOR ACCUMULATING SNOW...WE
WILL HAVE TO WATCH THE BOUNDARY LAYER THERMODYNAMICS TO SEE IF
ENOUGH COLD AIR MAKES IT IN EARLY ENOUGH TO COINCIDE WITH THE
HEAVIER PRECIPITATION.
BY SUNDAY...MOST OF THE MOISTURE EXITS THE FORECAST AREA AND
SKIES WILL BEGIN TO CLEAR SETTING THE STAGE FOR A COLD NIGHT WHERE
TEMPERATURES WILL DIP INTO THE TEENS IN MANY LOCATIONS AND LOWER
TEENS IN THE MOUNTAINS.
&&
.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
MODELS SHOWING AN UPSLOPE EVENT DEVELOPING SATURDAY NIGHT AND
CONTINUING ON SUNDAY BEHIND A LOW PRESSURE SYSTEM. HIGH PRESSURE
THEN BUILDS IN SUNDAY NIGHT. MODELS THEN DIVERGE CONSIDERABLY ON
SOLUTIONS FOR MONDAY THROUGH WEDNESDAY. USED A BLEND OF THE GEFS AND
ECMWF ENSEMBLE MEANS DURING THIS PERIOD...WITH SLIGHTLY MORE
EMPHASIS ON THE ECMWF ENSEMBLE MEAN.
&&
.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
MVFR CEILINGS WILL BE SLOW TO DISSOLVE AS THE WEAK NORTHWEST FLOW
EVENT WINDS DOWN INTO TONIGHT. CKB AND EKN WILL LIKELY BE THE LAST
TERMINALS TO EMERGE INTO VFR CEILINGS. CARRYING BRIEF IFR IN THE
NORTHEAST MOUNTAINS...WHICH WILL IMPROVE ACCORDINGLY WITH
DECREASING POPS.
NORTHWEST WINDS ALSO SUBSIDE INTO THIS EVENING...AND WILL GET ALL
SITES BELOW 12KTS BY LATER THIS EVENING. LOWLAND AREAS TO GO CALM
BEFORE DAWN.
VFR EXPECTED THURSDAY AS HIGH PRESSURE SETTLES IN. CLOUD COVER
WILL VARY. SURFACE FLOW WILL BE LIGHT AND VARIABLE DUE TO THE HIGH
PRESSURE SYSTEM PASSING THROUGH THE AREA.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z FRIDAY...
FORECAST CONFIDENCE: MEDIUM.
ALTERNATE SCENARIOS: DURATION OF MVFR CEILINGS MAY VARY BY A
COUPLE OF HOURS EITHER WAY.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
UTC 1HRLY 18 19 20 21 22 23 00 01 02 03 04 05
EST 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00
CRW CONSISTENCY L L L L L L L L L L L M
HTS CONSISTENCY H H H M M M H H H H H H
BKW CONSISTENCY L L L L L L L L L L M M
EKN CONSISTENCY L L L L L L M L L M L L
PKB CONSISTENCY H H H M L L L L L L L L
CKB CONSISTENCY L L L L L L L L L L L L
AFTER 18Z FRIDAY...
IFR POSSIBLE IN SNOW SATURDAY INTO SUNDAY...ESPECIALLY IN THE
MOUNTAINS.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WIND ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR WVZ046.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...ARJ/50
NEAR TERM...ARJ/26
SHORT TERM...JW
LONG TERM...RPY
AVIATION...26
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
1256 PM EST THU DEC 27 2012
.SYNOPSIS...
LOW PRESSURE SYSTEM EXITS EAST TODAY. ANOTHER LOW PRESSURE SYSTEM
FRIDAY NIGHT AND SATURDAY...WITH MORE MIXED PRECIPITATION...CHANGING
TO SNOW OVERNIGHT SATURDAY AND SUNDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
UPDATE...
NO CHANGES THIS AFTERNOON TO PREVIOUS GRIDS.
PREVIOUS DISCUSSION...
RADAR AND MODELS SHOWING LIGHT SNOW OR FREEZING DRIZZLE MOVING INTO
THE EASTERN MOUNTAINS WHILE DIMINISHING ACROSS THE WESTERN HALF OF
THE AREA THIS MORNING. LOW CLOUDS WILL PERSIST OVER A SHALLOW
SATURATED LAYER TODAY...LIFTING TONIGHT. HOWEVER...HIGH LEVEL
CLOUDS ASSOCIATED WITH A FAR AWAY SYSTEM WILL COVER PORTIONS OF OUR
SKIES THROUGH THIS EVENING.
VERY COLD AIR CONTINUES TO FILTER IN UNDER WEST NORTHWEST FLOW WITH
H850 TEMPS WARMING FROM MINUS 9C TO MINUS 5C BY 18Z THIS AFTERNOON
AND TONIGHT. THEREFORE...WITH CLOUDS EXPECTED AND VERY COLD AIR MASS
IN PLACE...TODAYS TEMPERATURES WILL REMAIN AT OR BELOW
FREEZING...EXCEPT FOR POCKETS JUST ABOVE OVER THE LOWLANDS. THESE
LOW TEMPERATURES WILL KEEP ANY WET SURFACE FROZEN...TO PRODUCE BLACK
ICE WHERE WATER USUALLY DRAINS FROM SLOPES...AND ON EXPOSED BRIDGES
AND OVERPASSES. DRIVERS SHOULD EXERCISE CAUTION WHEN TRAVELING
TODAY.
FOR TONIGHT...DRIER CONDITIONS WITH LESS CLOUDS. LOWS GENERALLY IN
THE MID 20S LOWLANDS...RANGING TO THE TEENS HIGHER ELEVATIONS.
HOWEVER...WINDS WILL DIMINISH TONIGHT...KEEPING SIMILAR WINDCHILL AS
TODAY.
GUSTY WINDS WILL PRODUCE WINDCHILL IN THE 20S LOWLANDS...RANGING
INTO NEAR ZERO AT THE HIGHEST PEAKS NORTHEAST MOUNTAINS.
A WIND WIND ADVISORY REMAINS IN EFFECT FOR POCAHONTAS COUNTY THROUGH
AT LEAST 1 PM THIS AFTERNOON.
WENT WITH A BLEND OF THE GMOS AND RUC MODELS FOR TEMPERATURES
THROUGH THE PERIOD.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
FRIDAY A SHORT BREAK IN THE ACTIVE WEATHER PATTERN TAKES PLACE WITH
S/W RIDGE OVERHEAD AT 12Z QUICKLY MOVING EAST WITH UPPER FLOW
TURNING SOUTHWESTERLY IN ADVANCE OF THE NEXT RAPIDLY-APPROACHING
UPPER LEVEL TROUGH MOVING ACROSS THE CENTRAL MISS VALLEY AREA. SFC
HIGH PRESSURE SLIDES OFF TO THE EAST WITH RETURN SOUTHERLY FLOW.
OVERALL A PARTLY CLOUDY DAY GENERALLY SPEAKING WITH MORE CLOUDS TO
START THE DAY AND CLOUDS INCREASING ACROSS THE WEST BY END OF DAY.
LOOKS LIKE A DECENT TEMPERATURE GRADIENT FORMS ACROSS THE AREA AS A
WARM FRONTAL FEATURE SETS UP ROUGHLY FROM POCAHONTAS COUNTY WSW-WARD
TOWARDS HTS BY FRI MID-AFTERNOON. FAR NW ZONES WHERE RESIDUAL SNOW
COVER REMAINS WILL ONLY REACH THE MID/UPPER 30S WHEREAS FAR SOUTHERN
ZONES...WHERE 925MB TEMPS ARE PROGGED TO REACH AROUND 5.5C TO
6C...WILL PUSH 50 DEGREES AND POTENTIALLY INTO THE LOWER 50S. FRIDAY
NIGHT...LARGE SCALE ASCENT OVERSPREADS THE FORECAST AREA FROM WEST
TO EAST AS AFOREMENTIONED TROUGH CONTINUES TOWARD THE AREA WITH AXIS
ENTERING THE CWA AROUND 12Z SAT WITH SFC COLD FRONT MOVING INTO CWA
WITH IT. BEST DEEP LAYER MOISTURE WILL BE ALONG AND AHEAD OF SFC
FRONT SO WILL HAVE BEST OVERALL POPS DURING THE OVERNIGHT PERIOD.
MEANWHILE OVERNIGHT THE WARM FRONT QUICKLY LIFTS NORTHWARD WITH
DEVELOPING SFC LOW ACROSS NORTH OF LAKE ERIE IN SW ONTARIO. RAISED
MINS A BIT TO ACCOUNT FOR LLVL WARM ADVECTION AT 850MB...ALBEIT IT
IS RELATIVELY WEAK. AS A RESULT...WILL KEEP THE RAIN/SNOW MIX LINE
NORTH OF THE INTERSTATE 64 CORRIDOR FRI NIGHT/SAT MORNING AND ALL
SNOW ALONG AND NORTH OF A LINE ROUGHLY FROM PKB TO CKB AND ACROSS
THE HIGHER ELEVATIONS. SATURDAY AS THE INITIAL TROUGH AND COLD FRONT
CONTINUE EASTWARD...DEEP LAYER MOISTURE WANES AS DO THE HIGHER POPS.
A SOLID 3-5KFT LLVL OF SATURATION WILL REMAIN...AND AS SUCH SATURDAY
STAYS CLOUDY. MEANWHILE THE UPPER TROUGH DIGS TO THE WEST AGAIN AS
COLD ADVECTION CONTINUES BEHIND FRONT. LONG STORY SHORT...CHANCES
FOR PRECIP DWINDLE SOMEWHAT DURING THE DAY BUT RAMP BACK UP ONCE
AGAIN PARTICULARLY AFTER 21Z SAT AS SECONDARY UPPER TROUGH AXIS
APPROACHES FROM THE WEST AND MEAGER LLVL MOISTURE DEEPENS A BIT.
AIDING IN PRECIP PRODUCTION WILL BE THE STEEPENING LLVL LAPSE RATES
WITH THE UPPER TROUGH APPROACH WHICH MAY ADD A LEVEL OF CONVECTIVE
ENHANCEMENT. BY SATURDAY EVENING AND SATURDAY NIGHT A SECONDARY PUSH
OF COLD ADVECTION INTO THE AREA SHOULD RESULT IN A CHANGEOVER TO ALL
SNOW FOR THE ENTIRE AREA BY 03Z-06Z SUN. SNOW ACCUMULATIONS ARE
EXPECTED TO REMAIN LIGHT HOWEVER...WITH A DUSTING TO PERHAPS AROUND
A HALF INCH FOR MOST LOWLAND LOCATIONS AND ONE TO TWO INCHES FOR
ELEVATIONS ABOVE ABOUT 2.5KFT.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
MODELS SHOWING AN UPSLOPE EVENT DEVELOPING SATURDAY NIGHT AND
CONTINUING ON SUNDAY BEHIND A LOW PRESSURE SYSTEM. HIGH PRESSURE
THEN BUILDS IN SUNDAY NIGHT. MODELS THEN DIVERGE CONSIDERABLY ON
SOLUTIONS FOR MONDAY THROUGH WEDNESDAY. USED A BLEND OF THE GEFS AND
ECMWF ENSEMBLE MEANS DURING THIS PERIOD...WITH SLIGHTLY MORE
EMPHASIS ON THE ECMWF ENSEMBLE MEAN.
&&
.AVIATION /17Z THURSDAY THROUGH MONDAY/...
MVFR CEILINGS WILL BE SLOW TO DISSOLVE AS THE WEAK NORTHWEST FLOW
EVENT WINDS DOWN INTO TONIGHT. CKB AND EKN WILL LIKELY BE THE LAST
TERMINALS TO EMERGE INTO VFR CEILINGS. CARRYING BRIEF IFR IN THE
NORTHEAST MOUNTAINS...WHICH WILL IMPROVE ACCORDINGLY WITH
DECREASING POPS.
NORTHWEST WINDS ALSO SUBSIDE INTO THIS EVENING...AND WILL GET ALL
SITES BELOW 12KTS BY LATER THIS EVENING. LOWLAND AREAS TO GO CALM
BEFORE DAWN.
VFR EXPECTED THURSDAY AS HIGH PRESSURE SETTLES IN. CLOUD COVER
WILL VARY. SURFACE FLOW WILL BE LIGHT AND VARIABLE DUE TO THE HIGH
PRESSURE SYSTEM PASSING THROUGH THE AREA.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z FRIDAY...
FORECAST CONFIDENCE: MEDIUM.
ALTERNATE SCENARIOS: DURATION OF MVFR CEILINGS MAY VARY BY A
COUPLE OF HOURS EITHER WAY.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
UTC 1HRLY 18 19 20 21 22 23 00 01 02 03 04 05
EST 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00
CRW CONSISTENCY L L L L L L L L L L L M
HTS CONSISTENCY H H H M M M H H H H H H
BKW CONSISTENCY L L L L L L L L L L M M
EKN CONSISTENCY L L L L L L M L L M L L
PKB CONSISTENCY H H H M L L L L L L L L
CKB CONSISTENCY L L L L L L L L L L L L
AFTER 18Z FRIDAY...
IFR POSSIBLE IN SNOW SATURDAY INTO SUNDAY...ESPECIALLY IN THE
MOUNTAINS.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WIND ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR WVZ046.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...ARJ/50
NEAR TERM...ARJ/26
SHORT TERM...50
LONG TERM...RPY
AVIATION...26
AREA FORECAST DISCUSSION
NWS WILMINGTON OH
1251 PM EST THU DEC 27 2012
.SYNOPSIS...
WEAK HIGH PRESSURE WILL BUILD INTO THE OHIO VALLEY FROM THE GREAT
LAKES TODAY. AHEAD OF AN UPPER LEVEL TROUGH...LOW PRESSURE WILL
NOSE INTO THE OHIO VALLEY FRIDAY NIGHT FROM THE LOWER MISSISSIPPI
VALLEY. THE LOW WILL EXIT ON SATURDAY BUT LINGERING FLURRIES
UNDERNEATH A LARGE UPPER LEVEL TROUGH WILL PERSIST INTO THE
WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SATELLITE IMAGES SHOWING A FEW THIN SPOTS OR POSSIBLE BREAKS
ACROSS PARTS OF EASTERN INDIANA/FAR WESTERN OHIO...BUT IN GENERAL
CLOUDS REMAIN WIDESPREAD ACROSS THE REGION. THE 12Z ILN SOUNDING IS
INDICATING A FAIRLY DEEP MOIST LAYER IN THE LOW LEVELS AND WITH
CONTINUED CYCLONIC LOW LEVEL FLOW THROUGH AT LEAST MID
AFTERNOON...WOULD EXPECT A FAIR AMOUNT OF CLOUDS TO HANG IN
THROUGH THE DAY. DESPITE THE NORTHERLY LOW LEVEL FLOW...TEMPERATURE
ADVECTION REMAINS MOSTLY NEUTRAL TODAY BUT WITH THE CLOUDS AND
SOME SNOW PACK...DO NOT EXPECT MUCH TEMPERATURE RECOVERY TODAY.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
CLOUD COVER WILL SEE SOME BREAKS TONIGHT AS HIGH PRESSURE SETTLES
OVER SOUTHWEST OHIO. COMBINED WITH THE FRESH SNOW PACK AND THE
LIGHTER WINDS FROM AFOREMENTIONED HIGH...TEMPERATURES TONIGHT WILL
BOTTOM OUT IN THE TEENS FOR MUCH OF THE REGION. IF SKIES WERE TO
CLEAR OUT ENTIRELY...TEMPERATURES WILL NEED TO BE ADJUSTED
DOWNWARDS.
LOW PRESSURE FROM THE GULF WILL SKIM SOUTHEAST OF THE REGION AGAIN
ON FRIDAY NIGHT AND EARLY SATURDAY. ENOUGH WARM AIR MAY BE PULLED
IN WITH IT TO HAVE A RAIN/SNOW MIX AT THE ONSET OVER PORTIONS OF
KENTUCKY. OTHERWISE THE PREDOMINANT WEATHER TYPE FOR THIS SYSTEM
WILL BE SNOW. THE SYSTEM WILL BE WELL AHEAD OF THE UPPER LEVEL
TROUGH AND NOT NEARLY AS ENERGETIC AS LAST NIGHTS SYSTEM. ANY
BRIEF SHOT OF SNOW EARLY ON SATURDAY WILL TAPER TO FLURRIES BY THE
AFTERNOON. THESE FLURRIES AND LIGHT SNOW SHOWERS WILL REMAIN
POSSIBLE FOR THE REMAINDER OF THE WEEKEND AS A LARGE UPPER LEVEL
TROUGH PROVIDES SUFFICIENT LIFT WITH AMPLE CLOUD COVER ALREADY IN
PLACE.
TEMPERATURES WILL TRY TO MAKE A REBOUND BUT BE HAMPERED BY CLOUDS
AND SNOW PACK. OVERNIGHT LOWS WILL BE HARD PRESSED TO SEE RUNAWAY
COLD TEMPERATURES DUE TO EXPECTED CLOUD COVER.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
CLOUDS WILL BEGIN TO DECREASE A BIT ON SUNDAY AS HIGH PRESSURE
OVER THE LOWER MS VALLEY MOVES NORTHEAST INTO THE REGION. THIS
SYSTEM WILL PROVIDE QUIET WEATHER THROUGH MONDAY MORNING. THE GFS
AND ECMWF THEN BEGIN TO DIVERGE SIGNIFICANTLY FOR THE REMAINDER OF
THE EXTENDED PERIOD...AND GEFS ENSEMBLE CLUSTERS SHOW CONSIDERABLE
SPREAD. A COLD FRONT IS PROGGED TO PUSH THROUGH THE AREA LATE
MONDAY NIGHT INTO TUESDAY...BRINGING THE NEXT CHANCE FOR SOME
PRECIP. FORECAST SOUNDINGS INDICATE THE ONSLAUGHT OF PRECIPITATION
MONDAY EVENING MAY BEGIN AS RAIN...SNOW...OR A MIX SOUTH OF THE
OHIO RIVER BEFORE COLDER TEMPERATURES CHANGE IT TO LIGHT SNOW.
ELSEWHERE... EXPECT JUST CHANCE/SLIGHT CHANCE FOR LIGHT SNOW AT
TIMES THROUGH WEDNESDAY.
&&
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
MVFR CLOUDS ARE PERSISTING ACROSS OUR AREA THIS AFTERNOON ALTHOUGH
SOME PARTIAL CLEARING AND SOME VFR CIGS ARE JUST OFF TO THE WEST.
SOME OF THIS PARTIAL CLEARING COULD AFFECT THE WESTERN TAF SITES
THROUGH THIS AFTERNOON...BUT GIVEN THE NORTHERLY LOW LEVEL
FLOW...WILL HANG ON TO THE MVFR CIGS THROUGH THE DAY. BETTER
CLEARING PUSHING DOWN INTO NORTHWEST OHIO IS BEING PICKED UP
FAIRLY WELL BY THE 12Z NAM...AND THIS IS FORECAST TO WORK ITS WAY
DOWN TOWARD CENTRAL OHIO THROUGH LATE AFTERNOON AND EARLY EVENING.
HOWEVER...BY THEN THE LOW LEVEL FLOW BEGINS TO SWING AROUND TO THE
SOUTHEAST AND THEN SOUTH OVERNIGHT SO NOT SURE EXACTLY HOW FAR
THE CLEARING WILL MAKE IT. ON THE OTHER HAND...AS THE LOW LEVEL
FLOW DOES BECOME MORE SOUTHERLY...WE COULD ALSO SEE SOME EROSION
OF THE LOW LEVEL CLOUDS ACROSS THE AREA. ALL OF THIS MAKES FOR A
FAIRLY LOW CONFIDENCE CLOUD FORECAST TONIGHT. WITH BOTH THE NAM
AND LATEST RAP HANGING ON TO SOME LOW LEVEL MOISTURE THROUGH MUCH
OF THE NIGHT...HAVE OPTED TO KEEP THINGS PESSIMISTIC AND HOLD ON
TO SOME MVFR CIGS THROUGH THE NIGHT. ON THE FLIP OF THAT...IF WE
DO GET SOME CLEARING...WE COULD SEE SOME MVFR BR DEVELOP LATER
TONIGHT GIVEN THE LIGHT WINDS.
OUTLOOK...MVFR/IFR CEILINGS AND VISIBILITIES POSSIBLE FRIDAY
NIGHT INTO SATURDAY NIGHT AND THEN AGAIN MONDAY AFTERNOON INTO
TUESDAY.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.
&&
$$
SYNOPSIS...FRANKS
NEAR TERM...JGL
SHORT TERM...FRANKS
LONG TERM...KURZ
AVIATION...JGL
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
540 AM EST THU DEC 27 2012
.SYNOPSIS...
LOW PRESSURE SYSTEM EXITS EAST TODAY. ANOTHER LOW PRESSURE SYSTEM
FRIDAY NIGHT AND SATURDAY...WITH MORE MIXED PRECIPITATION...CHANGING
TO SNOW OVERNIGHT SATURDAY AND SUNDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
RADAR AND MODELS SHOWING LIGHT SNOW OR FREEZING DRIZZLE MOVING INTO
THE EASTERN MOUNTAINS WHILE DIMINISHING ACROSS THE WESTERN HALF OF
THE AREA THIS MORNING. LOW CLOUDS WILL PERSIST OVER A SHALLOW
SATURATED LAYER TODAY...LIFTING TONIGHT. HOWEVER...HIGH LEVEL
CLOUDS ASSOCIATED WITH A FAR AWAY SYSTEM WILL COVER PORTIONS OF OUR
SKIES THROUGH THIS EVENING.
VERY COLD AIR CONTINUES TO FILTER IN UNDER WEST NORTHWEST FLOW WITH
H850 TEMPS WARMING FROM MINUS 9C TO MINUS 5C BY 18Z THIS AFTERNOON
AND TONIGHT. THEREFORE...WITH CLOUDS EXPECTED AND VERY COLD AIR MASS
IN PLACE...TODAYS TEMPERATURES WILL REMAIN AT OR BELOW
FREEZING...EXCEPT FOR POCKETS JUST ABOVE OVER THE LOWLANDS. THESE
LOW TEMPERATURES WILL KEEP ANY WET SURFACE FROZEN...TO PRODUCE BLACK
ICE WHERE WATER USUALLY DRAINS FROM SLOPES...AND ON EXPOSED BRIDGES
AND OVERPASSES. DRIVERS SHOULD EXERCISE CAUTION WHEN TRAVELING
TODAY.
FOR TONIGHT...DRIER CONDITIONS WITH LESS CLOUDS. LOWS GENERALLY IN
THE MID 20S LOWLANDS...RANGING TO THE TEENS HIGHER ELEVATIONS.
HOWEVER...WINDS WILL DIMINISH TONIGHT...KEEPING SIMILAR WINDCHILL AS
TODAY.
GUSTY WINDS WILL PRODUCE WINDCHILL IN THE 20S LOWLANDS...RANGING
INTO NEAR ZERO AT THE HIGHEST PEAKS NORTHEAST MOUNTAINS.
A WIND WIND ADVISORY REMAINS IN EFFECT FOR POCAHONTAS COUNTY THROUGH
AT LEAST 1 PM THIS AFTERNOON.
WENT WITH A BLEND OF THE GMOS AND RUC MODELS FOR TEMPERATURES
THROUGH THE PERIOD.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
FRIDAY A SHORT BREAK IN THE ACTIVE WEATHER PATTERN TAKES PLACE WITH
S/W RIDGE OVERHEAD AT 12Z QUICKLY MOVING EAST WITH UPPER FLOW
TURNING SOUTHWESTERLY IN ADVANCE OF THE NEXT RAPIDLY-APPROACHING
UPPER LEVEL TROUGH MOVING ACROSS THE CENTRAL MISS VALLEY AREA. SFC
HIGH PRESSURE SLIDES OFF TO THE EAST WITH RETURN SOUTHERLY FLOW.
OVERALL A PARTLY CLOUDY DAY GENERALLY SPEAKING WITH MORE CLOUDS TO
START THE DAY AND CLOUDS INCREASING ACROSS THE WEST BY END OF DAY.
LOOKS LIKE A DECENT TEMPERATURE GRADIENT FORMS ACROSS THE AREA AS A
WARM FRONTAL FEATURE SETS UP ROUGHLY FROM POCAHONTAS COUNTY WSW-WARD
TOWARDS HTS BY FRI MID-AFTERNOON. FAR NW ZONES WHERE RESIDUAL SNOW
COVER REMAINS WILL ONLY REACH THE MID/UPPER 30S WHEREAS FAR SOUTHERN
ZONES...WHERE 925MB TEMPS ARE PROGGED TO REACH AROUND 5.5C TO
6C...WILL PUSH 50 DEGREES AND POTENTIALLY INTO THE LOWER 50S. FRIDAY
NIGHT...LARGE SCALE ASCENT OVERSPREADS THE FORECAST AREA FROM WEST
TO EAST AS AFOREMENTIONED TROUGH CONTINUES TOWARD THE AREA WITH AXIS
ENTERING THE CWA AROUND 12Z SAT WITH SFC COLD FRONT MOVING INTO CWA
WITH IT. BEST DEEP LAYER MOISTURE WILL BE ALONG AND AHEAD OF SFC
FRONT SO WILL HAVE BEST OVERALL POPS DURING THE OVERNIGHT PERIOD.
MEANWHILE OVERNIGHT THE WARM FRONT QUICKLY LIFTS NORTHWARD WITH
DEVELOPING SFC LOW ACROSS NORTH OF LAKE ERIE IN SW ONTARIO. RAISED
MINS A BIT TO ACCOUNT FOR LLVL WARM ADVECTION AT 850MB...ALBEIT IT
IS RELATIVELY WEAK. AS A RESULT...WILL KEEP THE RAIN/SNOW MIX LINE
NORTH OF THE INTERSTATE 64 CORRIDOR FRI NIGHT/SAT MORNING AND ALL
SNOW ALONG AND NORTH OF A LINE ROUGHLY FROM PKB TO CKB AND ACROSS
THE HIGHER ELEVATIONS. SATURDAY AS THE INITIAL TROUGH AND COLD FRONT
CONTINUE EASTWARD...DEEP LAYER MOISTURE WANES AS DO THE HIGHER POPS.
A SOLID 3-5KFT LLVL OF SATURATION WILL REMAIN...AND AS SUCH SATURDAY
STAYS CLOUDY. MEANWHILE THE UPPER TROUGH DIGS TO THE WEST AGAIN AS
COLD ADVECTION CONTINUES BEHIND FRONT. LONG STORY SHORT...CHANCES
FOR PRECIP DWINDLE SOMEWHAT DURING THE DAY BUT RAMP BACK UP ONCE
AGAIN PARTICULARLY AFTER 21Z SAT AS SECONDARY UPPER TROUGH AXIS
APPROACHES FROM THE WEST AND MEAGER LLVL MOISTURE DEEPENS A BIT.
AIDING IN PRECIP PRODUCTION WILL BE THE STEEPENING LLVL LAPSE RATES
WITH THE UPPER TROUGH APPROACH WHICH MAY ADD A LEVEL OF CONVECTIVE
ENHANCEMENT. BY SATURDAY EVENING AND SATURDAY NIGHT A SECONDARY PUSH
OF COLD ADVECTION INTO THE AREA SHOULD RESULT IN A CHANGEOVER TO ALL
SNOW FOR THE ENTIRE AREA BY 03Z-06Z SUN. SNOW ACCUMULATIONS ARE
EXPECTED TO REMAIN LIGHT HOWEVER...WITH A DUSTING TO PERHAPS AROUND
A HALF INCH FOR MOST LOWLAND LOCATIONS AND ONE TO TWO INCHES FOR
ELEVATIONS ABOVE ABOUT 2.5KFT.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
MODELS SHOWING AN UPSLOPE EVENT DEVELOPING SATURDAY NIGHT AND
CONTINUING ON SUNDAY BEHIND A LOW PRESSURE SYSTEM. HIGH PRESSURE
THEN BUILDS IN SUNDAY NIGHT. MODELS THEN DIVERGE CONSIDERABLY ON
SOLUTIONS FOR MONDAY THROUGH WEDNESDAY. USED A BLEND OF THE GEFS AND
ECMWF ENSEMBLE MEANS DURING THIS PERIOD...WITH SLIGHTLY MORE
EMPHASIS ON THE ECMWF ENSEMBLE MEAN.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
RADAR IMAGES SHOW ROTATING ECHOS JUST EAST OF PA AND NORTHERN OH.
SHALLOW MOISTURE LAYER STILL PRODUCING LIGHT FREEZING DRIZZLE UNDER
STRONG GUSTY WINDS PEAKING JUST BELOW 40 KNOTS AT HIGHER
ELEVATIONS. THEREFORE...EXPECT MVFR/IFR CONDITIONS IN LOW STRATUS
OR LIGHT PCPN THIS MORNING. CONDITIONS IMPROVING BY NOON TIME FROM
WEST TO EAST...WITH EKN AND BKW THE LATEST TO IMPROVE AROUND
18-21Z THIS AFTERNOON.
NORTHWEST FLOW PREVAILS THROUGH TONIGHT...DECREASING LATER
OVERNIGHT.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z FRIDAY...
FORECAST CONFIDENCE: MEDIUM.
ALTERNATE SCENARIOS: DURATION AND EXTENT OF LOWER CIGS AND VSBYS
IN PRECIPITATION COULD VARY.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
UTC 1HRLY 11 12 13 14 15 16 17 18 19 20 21 22
EST 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17
CRW CONSISTENCY L L L L L L L L L L L L
HTS CONSISTENCY H H H L L L L H H H M H
BKW CONSISTENCY H M M L L L L L L L L L
EKN CONSISTENCY M M M L L L L L L L L L
PKB CONSISTENCY L L L L L L L H H H M L
CKB CONSISTENCY M M L L L L L L L L L L
AFTER 12Z FRIDAY...
IFR POSSIBLE IN SNOW SATURDAY INTO SUNDAY...ESPECIALLY IN THE
MOUNTAINS.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WIND ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR WVZ046.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...ARJ/50
NEAR TERM...ARJ
SHORT TERM...50
LONG TERM...RPY
AVIATION...ARJ
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
436 AM EST THU DEC 27 2012
.SYNOPSIS...
LOW PRESSURE SYSTEM EXITS EAST TODAY. ANOTHER LOW PRESSURE SYSTEM
FRIDAY NIGHT AND SATURDAY...WITH MORE MIXED PRECIPITATION...CHANGING
TO SNOW OVERNIGHT SATURDAY AND SUNDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
RADAR AND MODELS SHOWING LIGHT SNOW OR FREEZING DRIZZLE MOVING INTO
THE EASTERN MOUNTAINS WHILE DIMINISHING ACROSS THE WESTERN HALF OF
THE AREA THIS MORNING. LOW CLOUDS WILL PERSIST OVER A SHALLOW
SATURATED LAYER TODAY...LIFTING TONIGHT. HOWEVER...HIGH LEVEL
CLOUDS ASSOCIATED WITH A FAR AWAY SYSTEM WILL COVER PORTIONS OF OUR
SKIES THROUGH THIS EVENING.
VERY COLD AIR CONTINUES TO FILTER IN UNDER WEST NORTHWEST FLOW WITH
H850 TEMPS WARMING FROM MINUS 9C TO MINUS 5C BY 18Z THIS AFTERNOON
AND TONIGHT. THEREFORE...WITH CLOUDS EXPECTED AND VERY COLD AIR MASS
IN PLACE...TODAYS TEMPERATURES WILL REMAIN AT OR BELOW
FREEZING...EXCEPT FOR POCKETS JUST ABOVE OVER THE LOWLANDS. THESE
LOW TEMPERATURES WILL KEEP ANY WET SURFACE FROZEN...TO PRODUCE BLACK
ICE WHERE WATER USUALLY DRAINS FROM SLOPES...AND ON EXPOSED BRIDGES
AND OVERPASSES. DRIVERS SHOULD EXERCISE CAUTION WHEN TRAVELING
TODAY.
FOR TONIGHT...DRIER CONDITIONS WITH LESS CLOUDS. LOWS GENERALLY IN
THE MID 20S LOWLANDS...RANGING TO THE TEENS HIGHER ELEVATIONS.
HOWEVER...WINDS WILL DIMINISH TONIGHT...KEEPING SIMILAR WINDCHILL AS
TODAY.
GUSTY WINDS WILL PRODUCE WINDCHILL IN THE 20S LOWLANDS...RANGING
INTO NEAR ZERO AT THE HIGHEST PEAKS NORTHEAST MOUNTAINS.
A WIND WIND ADVISORY REMAINS IN EFFECT FOR POCAHONTAS COUNTY THROUGH
AT LEAST 1 PM THIS AFTERNOON.
WENT WITH A BLEND OF THE GMOS AND RUC MODELS FOR TEMPERATURES
THROUGH THE PERIOD.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
FRIDAY A SHORT BREAK IN THE ACTIVE WEATHER PATTERN TAKES PLACE WITH
S/W RIDGE OVERHEAD AT 12Z QUICKLY MOVING EAST WITH UPPER FLOW
TURNING SOUTHWESTERLY IN ADVANCE OF THE NEXT RAPIDLY-APPROACHING
UPPER LEVEL TROUGH MOVING ACROSS THE CENTRAL MISS VALLEY AREA. SFC
HIGH PRESSURE SLIDES OFF TO THE EAST WITH RETURN SOUTHERLY FLOW.
OVERALL A PARTLY CLOUDY DAY GENERALLY SPEAKING WITH MORE CLOUDS TO
START THE DAY AND CLOUDS INCREASING ACROSS THE WEST BY END OF DAY.
LOOKS LIKE A DECENT TEMPERATURE GRADIENT FORMS ACROSS THE AREA AS A
WARM FRONTAL FEATURE SETS UP ROUGHLY FROM POCAHONTAS COUNTY WSW-WARD
TOWARDS HTS BY FRI MID-AFTERNOON. FAR NW ZONES WHERE RESIDUAL SNOW
COVER REMAINS WILL ONLY REACH THE MID/UPPER 30S WHEREAS FAR SOUTHERN
ZONES...WHERE 925MB TEMPS ARE PROGGED TO REACH AROUND 5.5C TO
6C...WILL PUSH 50 DEGREES AND POTENTIALLY INTO THE LOWER 50S. FRIDAY
NIGHT...LARGE SCALE ASCENT OVERSPREADS THE FORECAST AREA FROM WEST
TO EAST AS AFOREMENTIONED TROUGH CONTINUES TOWARD THE AREA WITH AXIS
ENTERING THE CWA AROUND 12Z SAT WITH SFC COLD FRONT MOVING INTO CWA
WITH IT. BEST DEEP LAYER MOISTURE WILL BE ALONG AND AHEAD OF SFC
FRONT SO WILL HAVE BEST OVERALL POPS DURING THE OVERNIGHT PERIOD.
MEANWHILE OVERNIGHT THE WARM FRONT QUICKLY LIFTS NORTHWARD WITH
DEVELOPING SFC LOW ACROSS NORTH OF LAKE ERIE IN SW ONTARIO. RAISED
MINS A BIT TO ACCOUNT FOR LLVL WARM ADVECTION AT 850MB...ALBEIT IT
IS RELATIVELY WEAK. AS A RESULT...WILL KEEP THE RAIN/SNOW MIX LINE
NORTH OF THE INTERSTATE 64 CORRIDOR FRI NIGHT/SAT MORNING AND ALL
SNOW ALONG AND NORTH OF A LINE ROUGHLY FROM PKB TO CKB AND ACROSS
THE HIGHER ELEVATIONS. SATURDAY AS THE INITIAL TROUGH AND COLD FRONT
CONTINUE EASTWARD...DEEP LAYER MOISTURE WANES AS DO THE HIGHER POPS.
A SOLID 3-5KFT LLVL OF SATURATION WILL REMAIN...AND AS SUCH SATURDAY
STAYS CLOUDY. MEANWHILE THE UPPER TROUGH DIGS TO THE WEST AGAIN AS
COLD ADVECTION CONTINUES BEHIND FRONT. LONG STORY SHORT...CHANCES
FOR PRECIP DWINDLE SOMEWHAT DURING THE DAY BUT RAMP BACK UP ONCE
AGAIN PARTICULARLY AFTER 21Z SAT AS SECONDARY UPPER TROUGH AXIS
APPROACHES FROM THE WEST AND MEAGER LLVL MOISTURE DEEPENS A BIT.
AIDING IN PRECIP PRODUCTION WILL BE THE STEEPENING LLVL LAPSE RATES
WITH THE UPPER TROUGH APPROACH WHICH MAY ADD A LEVEL OF CONVECTIVE
ENHANCEMENT. BY SATURDAY EVENING AND SATURDAY NIGHT A SECONDARY PUSH
OF COLD ADVECTION INTO THE AREA SHOULD RESULT IN A CHANGEOVER TO ALL
SNOW FOR THE ENTIRE AREA BY 03Z-06Z SUN. SNOW ACCUMULATIONS ARE
EXPECTED TO REMAIN LIGHT HOWEVER...WITH A DUSTING TO PERHAPS AROUND
A HALF INCH FOR MOST LOWLAND LOCATIONS AND ONE TO TWO INCHES FOR
ELEVATIONS ABOVE ABOUT 2.5KFT.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
MODELS SHOWING AN UPSLOPE EVENT DEVELOPING SATURDAY NIGHT AND
CONTINUING ON SUNDAY BEHIND A LOW PRESSURE SYSTEM. HIGH PRESSURE
THEN BUILDS IN SUNDAY NIGHT. MODELS THEN DIVERGE CONSIDERABLY ON
SOLUTIONS FOR MONDAY THROUGH WEDNESDAY. USED A BLEND OF THE GEFS AND
ECMWF ENSEMBLE MEANS DURING THIS PERIOD...WITH SLIGHTLY MORE
EMPHASIS ON THE ECMWF ENSEMBLE MEAN.
&&
.AVIATION /10Z THURSDAY THROUGH MONDAY/...
RADAR IMAGES SHOW ROTATING ECHOS JUST EAST OF PA AND NORTHERN OH.
SHALLOW MOISTURE LAYER STILL PRODUCING LIGHT FREEZING DRIZZLE OR
LIGHT SNOW UNDER STRONG GUSTY WINDS PEAKING JUST BELOW 30 KNOTS AT
HIGHER ELEVATIONS. THEREFORE...EXPECT MVFR/IFR CONDITIONS IN LOW
STRATUS OR LIGHT PCPN OVERNIGHT. CONDITIONS IMPROVING AFTER SUNSET
FROM WEST TO EAST...WITH EKN AND BKW THE LATEST TO IMPROVE AROUND
18-21Z FRIDAY.
POSSIBLE PATCHY FREEZING DRIZZLE INTO TOMORROW HIGHER ELEVATIONS.
WIND DIRECTION WILL SHIFT AROUND TO THE NORTHWEST TONIGHT INTO
TOMORROW.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z FRIDAY...
FORECAST CONFIDENCE: MEDIUM.
ALTERNATE SCENARIOS: TIMING OF PRECIPITATION TYPE TRANSITION COULD
VARY. DURATION AND EXTENT OF POSSIBLE ICE COULD VARY. DURATION AND
EXTENT OF LOWER CIGS AND VSBYS IN PRECIPITATION COULD ALSO VARY.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE THU 12/27/12
UTC 1HRLY 08 09 10 11 12 13 14 15 16 17 18 19
EST 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14
CRW CONSISTENCY L L L L L L L L L L L H
HTS CONSISTENCY L L L L L L L L L L H H
BKW CONSISTENCY H H H M M M L L L L L L
EKN CONSISTENCY M M M M M M L L L L L L
PKB CONSISTENCY L L L L L L L L L L L L
CKB CONSISTENCY M M H H M L L L L L L L
AFTER 12Z FRIDAY...
IFR POSSIBLE IN SNOW SATURDAY INTO SUNDAY...ESPECIALLY IN THE
MOUNTAINS.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WIND ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR WVZ046.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...ARJ/50
NEAR TERM...ARJ
SHORT TERM...50
LONG TERM...RPY
AVIATION...ARJ
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NWS RAPID CITY SD
1051 AM MST THU DEC 27 2012
.DISCUSSION...UPPER LEVEL ANALYSIS HAS LARGE TROF OVER THE WESTERN
AND CENTRAL CONUS WITH CLOSED UPPER LOW IN NORTHERN NEBRASKA.
REGIONAL RADARS HAVE WIDESPREAD AREA OF SNOW ACROSS SOUTH DAKOTA
AND NEBRASKA ASSOCIATED WITH THIS LOW. SNOWFALL RATES HAVE BEEN
LIGHT...WITH GENERALLY 1 TO 2 INCHES OF SNOW ACCUMULATION SO FAR.
CURRENT SURFACE ANALYSIS HAS ARCTIC HIGH OVER THE GREAT LAKES AREA
WITH LOW PRESSURE OVER THE CENTRAL ROCKIES. WEAK INVERTED TROF
EXTENDS FROM THE COLORADO ROCKIES INTO NORTHEAST WYOMING. TEMPS
ARE MAINLY IN THE SINGLE DIGITS TO LOW TEENS. EAST TO SOUTHEAST
WINDS HAVE SWITCHED TO NORTH FROM FAR WESTERN SOUTH DAKOTA INTO
NORTHEAST WYOMING.
ACCUMULATING SNOWS HAVE ENDED ACROSS NORTHEAST WYOMING AND FAR
WESTERN SOUTH DAKOTA...WITH LIGHT SNOW CONTINUING FURTHER EAST.
UPPER LOW IS STARTING TO TAKE A JOG TO THE NORTHEAST...WHICH THE
LATEST RAP GUIDANCE IS NOW SHOWING. NOT MUCH CHANGE TO GOING
FORECAST THOUGH...AS DRIER AIR IS INVADING WESTERN PORTIONS OF THE
FORECAST AREA PRETTY QUICKLY. RADAR ECHOES HAVE SHOWN A MARKED
DECREASE OVER THE LAST COUPLE HOURS IN FAR WESTERN SOUTH DAKOTA.
STILL EXPECT ANOTHER INCH OR TWO OF SNOW ACROSS FAR SOUTH CENTRAL
SOUTH DAKOTA THIS AFTERNOON AND EVENING BEFORE SYSTEM FINALLY
SHIFTS EAST. UPDATES HAVE BEEN SENT.
&&
.AVIATION...18Z TAFS
-SN OVER WESTERN SD WILL SLOWLY MOVE EAST AND WANE THROUGH EARLY
THIS EVENING...BUT EXPECT IFR/MVFR CIGS/VSBYS WITH THE -SN. VFR
CONDITIONS WILL SLOWLY WORK ACROSS THE AREA FROM WEST TO EAST
TONIGHT...BUT POCKETS OF MVFR CIGS WILL LINGER OVER MUCH OF THE AREA
DUE TO BOUNDARY LAYER MOISTURE.
&&
.PREV DISCUSSION... /ISSUED 230 AM MST THU DEC 27 2012/
DISCUSSION...WATER VAPOR IMAGERY SHOWS BROAD CYCLONIC FLOW ACROSS
THE WESTERN HALF OF THE CONUS...WITH AN UPPER LOW CROSSING EASTERN
WYOMING INTO THE NEBRASKA PANHANDLE. SURFACE ANALYSIS SHOWS LOW
PRESSURE OVER THE COLORADO PLAINS WITH THE STRONG TEMP GRADIENT OF A
DRIFTING FRONT BOUNDARY STRETCHING FROM THE COLORADO LOW THROUGH
EASTERN WYOMING INTO CENTRAL MONTANA. KUDX RADAR SHOWS SNOW PUSHING
ACROSS THE AREA WITH THE STRONGEST RETURNS OVER THE BLACK HILLS AREA
THROUGH BUTTE COUNTY.
SNOW WILL CONTINUE TODAY AS THE SYSTEM PUSHES THROUGH. THE NEBRASKA
UPPER LOW WILL MOVE TO NEAR THE SOUTH CENTRAL SD BORDER EARLY THIS
MORNING...WITH A HEAVIER BAND OF SNOW CROSSING THE AREA AND THEN
EAST OF THE CWA TOWARD LATE MORNING. IT STILL LOOKS LIKE THE
FORECAST AREA WILL GENERALLY SEE ONE TO THREE INCHES OF
ACCUMULATION. SOME OF THE LOCATIONS NEAR THE SOUTHERN BLACK HILLS
MAY SEE ACCUMULATIONS CLOSER TO THE ONE INCH RANGE.
QUIETER WEATHER IS EXPECTED FRIDAY AND SATURDAY AS UPPER RIDGING
BUILDS ACROSS THE AREA. CLOUDY SKIES WILL PERSIST INTO FRIDAY...BUT
GRADUALLY DECREASING THROUGH THE DAY AS DRIER AIR PUSHES IN FROM THE
WEST. WARM AIR ADVECTION WILL BEGIN LATE FRIDAY...WITH HIGHS IN THE
UPPER TEENS TO MID 20S. CLOUDS WILL CLEAR OUT BY SUNRISE SATURDAY
MORNING...WITH PLENTY OF SUNSHINE IN STORE FOR THE DAY. WARM AIR
ADVECTION WILL STRENGTHEN WITH HIGHS REACHING THE MID 20S TO MID 30S.
EXTENDED...MODELS IN DECENT AGREEMENT WITH LONG WAVE TROF OVER THE
GREAT LAKES AND UPPER RIDGE OVER NORTHERN PLAINS WILL RESULT IN A
WARMING TREND ACROSS THE NORTHERN PLAINS. A FEW GEFS MEMBERS STILL
SHOW SHALLOW ARCTIC INTRUSION INTO WESTERN SOUTH DAKOTA EARLY NEXT
WEEK...BUT A MAJORITY OF THE MEMBERS HAVE BEEN TRENDING WARMER WITH
EACH MODEL RUN. WILL MAINTAIN DRY FORECAST WITH TEMPERATURES WARMING
TO NEAR AVERAGE.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
SHORT TERM...15
LONG TERM....WFO UNR
AVIATION...HELGESON
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NWS RAPID CITY SD
1046 PM MST WED DEC 26 2012
.AVIATION...06Z TAF UPDATE
CONDITIONS CONTINUE TO DETERIORATE ACROSS NORTHEAST WYOMING AND
WESTERN SOUTH DAKOTA THIS EVENING. AN UPPER LOW IS CROSSING THE
NORTHERN ROCKIES AND REDEVELOPING OVER NORTHEAST WYOMING...
PRODUCING A BROAD AREA OF LIGHT SNOW. WIDESPREAD IFR WITH LOCAL
LIFR CIGS AND VSBYS ARE FORECAST TO CONTINUE SPREADING EASTWARD. LITTLE
OR NO IMPROVEMENT IS EXPECTED UNTIL AT LEAST MIDDAY THURSDAY AS
THE WRAP AROUND CONVEYOR OF MOIST AIR MOVES LEISURELY ACROSS THE
AREA.
&&
.PREV DISCUSSION... /ISSUED 804 PM MST WED DEC 26 2012/
UPDATE...MINOR UPDATES WERE MADE TO INCREASE POPS OVER PARTS OF
NORTHEAST WYOMING AND NORTHWEST SOUTH DAKOTA WHERE PERSISTENT SNOW
BANDS HAVE DEVELOPED THIS EVENING. HRRR GUIDANCE INDICATES THESE
FEATURES WILL CONTINUE INTO THE OVERNIGHT HOURS.
&&
PREV DISCUSSION... /ISSUED 258 PM MST WED DEC 26 2012/
DISCUSSION...UPPER LEVEL ANALYSIS HAS WEAK RIDGE OVER THE SOUTH
CENTRAL PLAINS WITH LARGE TROF ACROSS THE WESTERN CONUS.
DEVELOPING SHORTWAVE OVER NORTHERN UTAH/SW WYOMING IS LIFTING OUT
OF THE TROF AT THE MOMENT. CLOUD COVER IS ON THE INCREASE ACROSS
THE FORECAST AREA. AT THE SURFACE...ARCTIC HIGH PRESSURE STILL
DOMINATES THE NORTHERN PLAINS. WEAK SURFACE LOW PRESSURE IS
STRENGTHENING ACROSS SOUTH CENTRAL WYOMING...WITH AN INVERTED TROF
EXTENDING INTO NORTHEAST WYOMING. TEMPERATURES ARE MAINLY IN THE
TEENS TO LOWER 20S ACROSS THE AREA...WITH LIGHT SOUTH TO SOUTHEAST
WINDS.
FOR TONIGHT...UPPER TROUGH WILL DIG INTO THE FOUR CORNERS AS WEAK
SHORTWAVE EJECTS INTO THE NORTHERN PLAINS. BEST DYNAMICS WILL SKIRT
JUST TO THE SOUTH OF THE FORECAST AREA...BUT WEAK ENERGY AND FORCING
ASSOCIATED WITH MAIN TROF WILL BRING ANOTHER ROUND OF SNOW TO THE
AREA. SNOW WILL BEGIN THIS EVENING ACROSS NORTHEAST WYOMING AND
FAR WESTERN SOUTH DAKOTA...AND SPREAD EASTWARD LATER TONIGHT. SNOW
ACCUMULATIONS OF AROUND AN INCH WILL BE POSSIBLE ACROSS WESTERN
AREAS OVERNIGHT. TEMPERATURES WILL FALL INTO THE SINGLE DIGITS FOR
MOST LOCATIONS.
ON THURSDAY...UPPER TROF CROSSES THE AREA AS MID LEVEL CLOSED LOW
SLIDES THROUGH NEBRASKA. SURFACE LOW REMAINS WELL SOUTH OF THE
AREA AS ARCTIC HIGH DOMINATES. INVERTED SURFACE TROF SLIDES ACROSS
THE DAKOTAS...SWITCHING WINDS FROM EAST SOUTHEAST TO THE NORTH.
BEST ENERGY/SNOWFALL WILL REMAIN OVER NORTHEAST WYOMING...THE
NORTHERN BLACK HILLS...AND NORTHWEST SOUTH DAKOTA WITH THIS SYSTEM.
LATER IN THE DAY...CLOSED MID LEVEL LOW OVER NEBRASKA WILL
ORGANIZE...AND PRODUCE A MODERATE BAND OF SNOW OVER SOUTH CENTRAL
SOUTH DAKOTA THROUGH THURSDAY NIGHT. SNOWFALL TOTALS SHOULD BE
AROUND 2 TO 3 INCHES FROM NORTHEAST WYOMING...THE NORTHERN
HILLS...INTO NORTHWEST SOUTH DAKOTA BY THURSDAY EVENING. SOUTH
CENTRAL SOUTH DAKOTA SHOULD ALSO SEE ABOUT 2 TO 3 INCHES. IN
BETWEEN...1 TO 2 INCHES WILL BE POSSIBLE. WITH ABUNDANT CLOUDS AND
SNOW...HIGH TEMPERATURES WILL STRUGGLE INTO THE TEENS.
FOR FRIDAY...UPPER LEVEL CYCLONIC FLOW WILL CONTINUE THROUGH
FRIDAY...HOWEVER NO PRECIPITATION IS EXPECTED. PLENTY OF
CLOUDINESS IS EXPECTED FRIDAY MORNING...BUT WITH DRIER AIR MOVING
IN FROM THE WEST...NORTHEAST WYOMING AND SOUTHWESTERN SOUTH DAKOTA
MAY SEE SOME SUNSHINE BEFORE THE END OF THE DAY. HIGHS WILL BE IN
THE UPPER TEENS TO MID 20S.
EXTENDED...LONG WAVE TROF OVER THE GREAT LAKES AND UPPER RIDGE OVER
NORTHERN PLAINS WILL GIVE THE FORECAST AREA WARMER TEMPERATURES FOR
THE WEEKEND...WITH HIGHS NEAR NORMAL. AS RIDGE SHIFTS TO THE
EAST...NEXT TROF DEEPENS ACROSS THE WESTERN US...WITH CUT-OFF LOW
OVER THE SOUTHWESTERN US AND NORTHWEST FLOW OVER NORTHERN PLAINS
THROUGH MIDWEEK. DIFFERENCES IN MODEL TIMING OF SEVERAL SHORT WAVES
RESULTS IN LOW POPS...BUT WOULD EXPECT OCCASIONAL CHANCES OF PRECIP
TO INCREASE IN THE SHORT TERM. ARCTIC AIR PROGGED TO REMAIN NORTH
AND EAST OF THE FORECAST AREA...SO WILL MAINTAIN GRADUAL WARMING
TREND.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
SHORT TERM...WFO UNR
LONG TERM....WFO UNR
AVIATION...CARPENTER
AREA FORECAST DISCUSSION...UPDATED
NWS MILWAUKEE/SULLIVAN WI
1144 AM CST THU DEC 27 2012
.UPDATE...ADDED SCATTERED FLURRIES FOR THE LAKESHORE COUNTIES
THROUGH THIS EVENING...GIVEN VERY LIGHT REFLECTIVITY RETURNS ON
RADARS. NORTHEAST FETCH AND DELTA T VALUES REMAIN FAVORABLE AS
THEY HAVE BEEN THE PAST FEW DAYS. HOWEVER...THE ISSUE ONCE AGAIN
IS THE LACK OF MOISTURE IN THE DENDRITE GROWTH ZONE.
MESOSCALE MODELS DO SHOW A CONVERGENCE ZONE WITH BROKEN LIGHT QPF
EXTENDING FROM DOWNTOWN CHICAGO NORTHWARD AND OFF SHORE OF THE
LAKESHORE COUNTIES...AND THEN NORTHEAST FROM THERE. THIS AREA
REMAINS OVER THE WATER THROUGH THE REST OF TODAY...WITH SOME
INDICATIONS OF IT COMING ONSHORE IN THE FAR SOUTHEAST COUNTIES
THIS EVENING.
THUS...NOTHING MORE THAN FLURRIES ARE EXPECTED. CLOUDY SKIES WILL
REMAIN THROUGH THE DAY AND EVENING...WITH TEMPERATURES REMAINING
IN THE MID 20S TO AROUND 30.
&&
.AVIATION/18Z TAFS/...EXPECT MVFR/VFR CEILINGS TO REMAIN ACROSS
TAF SITES THIS AFTERNOON AND TONIGHT. WINDS WILL CONTINUE TO
GRADUALLY WEAKEN AS WELL.
LIGHT SNOW WITH MVFR VISIBILITIES/CEILINGS WILL MOVE WEST TO EAST
INTO KMSN BY 11Z FRIDAY...AND THE EASTERN SITES BY 15Z
FRIDAY. MORE STEADY SNOW/VISIBILITIES BELOW ALTERNATE MINIMUMS
WILL REACH KMSN BY 13Z FRIDAY...AND THE EASTERN SITES BY 17Z
FRIDAY. CEILINGS WILL BE IFR CATEGORY.
EXPECT A GENERAL 2 TO 3 INCH ACCUMULATION BY LATE FRIDAY...WITH A
TOTAL OF 3 TO 4 INCHES BY LATER FRIDAY NIGHT.
&&
.MARINE...SMALL CRAFT ADVISORY REMAINS IN EFFECT UNTIL 00Z FRIDAY
ACROSS THE NEARSHORE WATERS. PRESSURE GRADIENT AND SUBSEQUENT
WINDS CONTINUE TO WEAKEN...AS THE STRONG LOW MOVES INTO COASTAL
NEW ENGLAND. WAVES WILL SUBSIDE AS WELL...FALLING BELOW SMALL
CRAFT ADVISORY LEVELS BY 00Z FRIDAY.
&&
.PREV DISCUSSION... /ISSUED 400 AM CST THU DEC 27 2012/
SHORT TERM...
TODAY-FORECAST CONFIDENCE HIGH
SECONDARY LOW OFF SOUTHERN NEW ENGLAND TAKING OVER ON EAST COAST
STORM AND FLOW OVER LAKE MICHIGAN TURNING MORE NORTHERLY WITH TIME.
WEAK LAKE EFFECT BAND RIGHT ALONG THE RACINE/KENOSHA SHORE HAS YET
TO TRIGGER A FLURRY AT THE KRAC OBSERVATION...AND SEEMS TO BE
SHIFTING OFFSHORE. 4KM MODELS SEEM TO HAVE A BIT OF A STRONG BIAS
ON THIS FEATURE AND HAVE IT TOO FAR WEST.
LATEST LOCAL WSWRF AND HRRR ARE NOT TOO IMPRESSIVE WITH THIS FEATURE
AND KEEP IT MOSTLY OFFSHORE. IT SHOULD BE NOTED THAT THE MODELS
TURN THE FLOW IN THE LOWEST 1-2KM MORE AND MORE NORTHERLY AND
ACTUALLY INCREASE 850 MB TEMPS A BIT THIS MORNING...DECREASING THE
LAKE INSTABILITY AND DELTA TS A BIT FROM ROUGHLY 15 TO ABOUT 13.
THE LAKE EFFECT STRUGGLED THROUGHOUT THE EVENT DUE TO RELATIVELY DRY
AIR IN 850 TO 700 MB LAYER AND A LOW INVERSION HEIGHT THAT WAS OFTEN
DOWN TO 4000 FEET. WILL KEEP SOME LOW POPS NEAR THE KENOSHA/RACINE
LAKE SHORE BUT DO NOT EXPECT MUCH TO HAPPEN.
OTHERWISE EXPECT THE GRADIENT TO WEAKEN TODAY WITH WEAK SURFACE
RIDGE MOVING OVER WISCONSIN. STRATUS STATUS APPEARS TO BE PRIMARY
MESSAGE...AS FOG PRODUCT SHOWS A WESTWARD TREND IN LOW CLOUDS. THIS
IS OPPOSED TO THE TREND THAT I FORECAST LAST NIGHT...WHICH SHOULD
NOT BE SURPRISING FOR THOSE WHO KNOW ME.
PER COORDINATION WITH SURROUNDING OFFICES...WENT WITH MUCH CLOUDIER
FORECAST TODAY AS TIME SECTIONS INDICATE LOW CLOUDS WILL BE TOUGH TO
SCOUR OUT TODAY WITH WEAK FORCING AND DECREASING GRADIENT.
TONIGHT-FORECAST CONFIDENCE HIGH
SATELLITE SHOWS IMPRESSIVE VORTICITY MAXIMUM EMERGING ON THE HIGH
PLAINS IN WESTERN NEBRASKA CURRENTLY. MODELS IN GOOD AGREEMENT IN
MOVING 500 MB CLOSED LOW TO NORTH CENTRAL NEBRASKA THIS AFTERNOON
AND THEN CLOSE TO THE SD/IA/NE BORDER AREA NEAR SIOUX CITY TONIGHT.
WEAK BUT DEEP WARM ADVECTION EXPECTED AHEAD OF THIS FEATURE AND
SHOULD SPREAD ACROSS IOWA TOWARD WISCONSIN LATE TONIGHT. DESPITE
FAIRLY WEAK LIFT THERE IS A RATHER DEEP AND NEARLY SATURATED LAYER
IN THE DENDRITE GROWTH ZONE (-12 TO -18C) WITH THIS SYSTEM WHICH
WOULD ENHANCE SNOW POTENTIAL AND ESPECIALLY SNOW TO LIQUID RATIOS.
THEREFORE WENT WAY ABOVE GUIDANCE IN THE WEST LATE TONIGHT...WHICH
IS SURPRISINGLY LOW GIVEN CONSISTENT HANDLING OF THIS FEATURE BY
GUIDANCE. APPEARS THAT MOS IS LEANING TOWARD THE TENDENCY FOR ASOS
TO STRUGGLE TO MEASURE LIGHT SNOWFALL IN EVENTS LIKE THIS.
FRIDAY AND FRIDAY NIGHT...FORECAST CONFIDENCE HIGH.
SNOW WILL OVERSPREAD ALL OF SOUTHERN WI FRI MORNING AND TAPER OFF
FROM WEST TO EAST FRIDAY EVENING. STORM TOTAL SNOW AMOUNTS FROM LATE
THU NIGHT THROUGH FRIDAY EVENING SHOULD BE IN THE 2 TO 4 INCH
RANGE...POSSIBLY HIGHER FROM THE DELLS TO MADISON TO RACINE AND THE
OTHER LAKESHORE COUNTIES IF LAKE ENHANCEMENT OCCURS. MAJORITY OF THE
SNOW SHOULD FALL IN AN 8-HOUR PERIOD ON FRIDAY...AFFECTING THE
MORNING RUSH IN MADISON AND THE EVENING RUSH IN BOTH MADISON AND
MILWAUKEE. A LOW-END WINTER WEATHER ADVISORY WILL NEED TO BE
CONSIDERED...BUT WILL HIGHLIGHT THE RUSH HOUR HEADACHE WITH A
SPECIAL WEATHER STATEMENT FOR NOW.
OVERALL THE SYSTEM DYNAMICS ARE NOT OVERLY IMPRESSIVE...BUT THE
SLOW-MOVING NATURE OF THE UPPER TROUGH AND THE SUBTLE AND PERSISTENT
FORCING WILL BE ENOUGH TO PRODUCE SEVERAL INCHES OF FLUFFY SNOW OVER
ROUGHLY AN 18-HR PERIOD. WINDS WILL BE LIGHT OUT OF THE EAST ON
FRIDAY. THE STRONGEST FORCING WILL BE ASSOCIATED WITH A VORT MAX
ROLLING ACROSS IOWA AND SOUTHERN WI FRI. BEST OMEGA VALUES WILL
GENERALLY BE JUST BELOW THE DENDRITIC GROWTH ZONE /DGZ/ FOR MOST OF
THE PERIOD. HOWEVER... THE DGZ WILL BE FAIRLY DEEP AT AROUND 5K TO
7K FT. THERE SHOULD BE AT LEAST A FEW-HOUR PERIOD OF TIME WHERE
THERE IS DECENT OMEGA WITHIN THE DEEP DGZ LEADING TO EFFICIENT SNOW
ACCUMULATION. THE NAM SHOWS THIS OCCURRING AROUND 18Z AT MSN AND 20Z
AT MKE.
SEVERAL OF THE MESOSCALE MODELS ARE SHOWING A MID-LAKE LAKE EFFECT
BAND MOVE ONSHORE WITH THE EASTERLY WINDS...WITH A FEW OF THEM
DEVELOPING A MESO-LOW OVER SOUTHERN LAKE MICHIGAN. AS A
RESULT...THESE MODELS SEEM TO BE OVER-DOING THE QPF AND SNOW AMOUNTS
NEAR THE LAKESHORE. BUT IT NEEDS TO BE NOTED THAT SOME SUBTLE LAKE
ENHANCEMENT WILL BE POSSIBLE WITH THE 13C-18C DELTA T FOR THE
LAKESHORE COUNTIES.
SATURDAY...FORECAST CONFIDENCE MEDIUM.
THE UPPER TROUGH WILL STILL BE OVER THE GREAT LAKES REGION AND THE
LOW LEVEL MOISTURE WILL LINGER SO KEPT MENTION OF FLURRIES THROUGH
THE DAY AND CLOUDS THROUGH THE DAY AND NIGHT. WEAK COLD AIR
ADVECTION DURING THIS TIME...BUT CLOUD COVER WILL KEEP TEMPS
MODERATED...WITH HIGHS IN THE UPPER 20S.
LONG TERM...
SUNDAY THROUGH THURSDAY...FORECAST CONFIDENCE...MEDIUM.
SOME SUNSHINE IS EXPECTED ON SUNDAY. LOW PRESSURE WILL TRACK ACROSS
LAKE SUPERIOR SUN NIGHT AND THE ASSOCIATED COLD FRONT WILL CROSS
SOUTHERN WI MON MORNING...USHERING COLDER AIR INTO THE AREA. A
PERIOD OF CLOUDS WILL BE LIKELY WITH THIS FRONTAL PASSAGE.
ANOTHER WEAK WAVE WILL MOVE THROUGH THE UPPER GREAT LAKES AREA WED
MORNING WHICH MAY PRODUCE SOME LIGHT SNOW OR FLURRIES. THE ECMWF IS
DRY AND THE GFS SHOWS VERY LIGHT QPF.
AVIATION/12Z TAFS/...
TIME HEIGHT SECTIONS FROM BOTH GFS AND NAM NOW SHOW STRATUS
REMAINING IN PLACE IN SOUTHEAST THROUGH TONIGHT. SHOULD BE NO WORSE
THAN MVFR AND LIKELY TO IMPROVE A TAD TO LOWER END VFR CEILINGS
LATER TODAY INTO TONIGHT. MOST UNCERTAINTY IS KMSN...WHERE THE
GUIDANCE SHOWS THE STRATUS DECK VANISHING WITHIN THE NEXT FEW
HOURS.
FOG PRODUCT TRENDS AND SURFACE OBSERVATIONS DO NOT SUPPORT THIS
TREND. THUS...WILL EXTEND THE VFR CEILING A BIT LONGER INTO THE
MIDDAY HOURS BEFORE GOING WITH SCATTERED LOWER DECK.
REGARDLESS OF WHAT HAPPENS TO LOWER DECK EXPECT MID LEVEL CLOUDS TO
MOVE IN QUICKLY AROUND 00Z AND GRADUALLY LOWER WITH A GOOD THREAT
FOR VIRGA/SNOW ALOFT IN THE 06Z TO 12Z PERIOD...ESPECIALLY IN KMSN.
SNOW SHOULD START AROUND 12Z IN KMSN AND THEN SPREAD TO SOUTHEAST
WI STAFFS AROUND 18Z. PROLONGED IFR CONDITIONS LIKELY WITH THE
LIGHT SNOW.
MARINE...
NORTH TO NORTHWEST WINDS ARE NEAR SMALL CRAFT LEVELS NOW BUT SHOULD
GRADUALLY DIMINISH TODAY. WITH OFFSHORE FLOW THE WAVES ARE ALREADY
DIMINISHING BUT SHOULD REMAIN ABOVE 4 FEET UNTIL LATE AFTERNOON.
PER COORDINATION WITH GRB AND LOT WILL END SMALL CRAFT ADVISORY
ABOUT 9 HOURS EARLIER THAN PREVIOUS FORECASTS...AT 00Z TODAY.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 6 PM CST THIS EVENING FOR LMZ643>646.
&&
$$
UPDATE...WOOD
TODAY/TONIGHT AND AVIATION/MARINE...CRAVEN
FRIDAY THROUGH WEDNESDAY...MRC
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
400 AM CST THU DEC 27 2012
.SHORT TERM...
TODAY-FORECAST CONFIDENCE HIGH
SECONDARY LOW OFF SOUTHERN NEW ENGLAND TAKING OVER ON EAST COAST
STORM AND FLOW OVER LAKE MICHIGAN TURNING MORE NORTHERLY WITH TIME.
WEAK LAKE EFFECT BAND RIGHT ALONG THE RACINE/KENOSHA SHORE HAS YET
TO TRIGGER A FLURRY AT THE KRAC OBSERVATION...AND SEEMS TO BE
SHIFTING OFFSHORE. 4KM MODELS SEEM TO HAVE A BIT OF A STRONG BIAS
ON THIS FEATURE AND HAVE IT TOO FAR WEST.
LATEST LOCAL WSWRF AND HRRR ARE NOT TOO IMPRESSIVE WITH THIS FEATURE
AND KEEP IT MOSTLY OFFSHORE. IT SHOULD BE NOTED THAT THE MODELS
TURN THE FLOW IN THE LOWEST 1-2KM MORE AND MORE NORTHERLY AND
ACTUALLY INCREASE 850 MB TEMPS A BIT THIS MORNING...DECREASING THE
LAKE INSTABILITY AND DELTA TS A BIT FROM ROUGHLY 15 TO ABOUT 13.
THE LAKE EFFECT STRUGGLED THROUGHOUT THE EVENT DUE TO RELATIVELY DRY
AIR IN 850 TO 700 MB LAYER AND A LOW INVERSION HEIGHT THAT WAS OFTEN
DOWN TO 4000 FEET. WILL KEEP SOME LOW POPS NEAR THE KENOSHA/RACINE
LAKE SHORE BUT DONT EXPECT MUCH TO HAPPEN.
OTHERWISE EXPECT THE GRADIENT TO WEAKEN TODAY WITH WEAK SURFACE
RIDGE MOVING OVER WISCONSIN. STRATUS STATUS APPEARS TO BE PRIMARY
MESSAGE...AS FOG PRODUCT SHOWS A WESTWARD TREND IN LOW CLOUDS. THIS
IS OPPOSED TO THE TREND THAT I FORECAST LAST NIGHT...WHICH SHOULD
NOT BE SURPRISING FOR THOSE WHO KNOW ME.
PER COORDINATION WITH SURROUNDING OFFICES...WENT WITH MUCH CLOUDIER
FORECAST TODAY AS TIME SECTIONS INDICATE LOW CLOUDS WILL BE TOUGH TO
SCOUR OUT TODAY WITH WEAK FORCING AND DECREASING GRADIENT.
TONIGHT-FORECAST CONFIDENCE HIGH
SATELLITE SHOWS IMPRESSIVE VORTICITY MAXIMUM EMERGING ON THE HIGH
PLAINS IN WESTERN NEBRASKA CURRENTLY. MODELS IN GOOD AGREEMENT IN
MOVING 500 MB CLOSED LOW TO NORTH CENTRAL NEBRASKA THIS AFTERNOON
AND THEN CLOSE TO THE SD/IA/NE BORDER AREA NEAR SIOUX CITY TONIGHT.
WEAK BUT DEEP WARM ADVECTION EXPECTED AHEAD OF THIS FEATURE AND
SHOULD SPREAD ACROSS IOWA TOWARD WISCONSIN LATE TONIGHT. DESPITE
FAIRLY WEAK LIFT THERE IS A RATHER DEEP AND NEARLY SATURATED LAYER
IN THE DENDRITE GROWTH ZONE (-12 TO -18C) WITH THIS SYSTEM WHICH
WOULD ENHANCE SNOW POTENTIAL AND ESPECIALLY SNOW TO LIQUID RATIOS.
THEREFORE WENT WAY ABOVE GUIDANCE IN THE WEST LATE TONIGHT...WHICH
IS SURPRISINGLY LOW GIVEN CONSISTENT HANDLING OF THIS FEATURE BY
GUIDANCE. APPEARS THAT MOS IS LEANING TOWARD THE TENDENCY FOR ASOS
TO STRUGGLE TO MEASURE LIGHT SNOWFALL IN EVENTS LIKE THIS.
FRIDAY AND FRIDAY NIGHT...FORECAST CONFIDENCE HIGH.
SNOW WILL OVERSPREAD ALL OF SOUTHERN WI FRI MORNING AND TAPER OFF
FROM WEST TO EAST FRIDAY EVENING. STORM TOTAL SNOW AMOUNTS FROM LATE
THU NIGHT THROUGH FRIDAY EVENING SHOULD BE IN THE 2 TO 4 INCH
RANGE...POSSIBLY HIGHER FROM THE DELLS TO MADISON TO RACINE AND THE
OTHER LAKESHORE COUNTIES IF LAKE ENHANCEMENT OCCURS. MAJORITY OF THE
SNOW SHOULD FALL IN AN 8-HOUR PERIOD ON FRIDAY...AFFECTING THE
MORNING RUSH IN MADISON AND THE EVENING RUSH IN BOTH MADISON AND
MILWAUKEE. A LOW-END WINTER WEATHER ADVISORY WILL NEED TO BE
CONSIDERED...BUT WILL HIGHLIGHT THE RUSH HOUR HEADACHE WITH A
SPECIAL WEATHER STATEMENT FOR NOW.
OVERALL THE SYSTEM DYNAMICS ARE NOT OVERLY IMPRESSIVE...BUT THE
SLOW-MOVING NATURE OF THE UPPER TROUGH AND THE SUBTLE AND PERSISTENT
FORCING WILL BE ENOUGH TO PRODUCE SEVERAL INCHES OF FLUFFY SNOW OVER
ROUGHLY AN 18-HR PERIOD. WINDS WILL BE LIGHT OUT OF THE EAST ON
FRIDAY. THE STRONGEST FORCING WILL BE ASSOCIATED WITH A VORT MAX
ROLLING ACROSS IOWA AND SOUTHERN WI FRI. BEST OMEGA VALUES WILL
GENERALLY BE JUST BELOW THE DENDRITIC GROWTH ZONE /DGZ/ FOR MOST OF
THE PERIOD. HOWEVER... THE DGZ WILL BE FAIRLY DEEP AT AROUND 5K TO
7K FT. THERE SHOULD BE AT LEAST A FEW-HOUR PERIOD OF TIME WHERE
THERE IS DECENT OMEGA WITHIN THE DEEP DGZ LEADING TO EFFICIENT SNOW
ACCUMULATION. THE NAM SHOWS THIS OCCURRING AROUND 18Z AT MSN AND 20Z
AT MKE.
SEVERAL OF THE MESOSCALE MODELS ARE SHOWING A MID-LAKE LAKE EFFECT
BAND MOVE ONSHORE WITH THE EASTERLY WINDS...WITH A FEW OF THEM
DEVELOPING A MESO-LOW OVER SOUTHERN LAKE MICHIGAN. AS A
RESULT...THESE MODELS SEEM TO BE OVER-DOING THE QPF AND SNOW AMOUNTS
NEAR THE LAKESHORE. BUT IT NEEDS TO BE NOTED THAT SOME SUBTLE LAKE
ENHANCEMENT WILL BE POSSIBLE WITH THE 13C-18C DELTA T FOR THE
LAKESHORE COUNTIES.
SATURDAY...FORECAST CONFIDENCE MEDIUM.
THE UPPER TROUGH WILL STILL BE OVER THE GREAT LAKES REGION AND THE
LOW LEVEL MOISTURE WILL LINGER SO KEPT MENTION OF FLURRIES THROUGH
THE DAY AND CLOUDS THROUGH THE DAY AND NIGHT. WEAK COLD AIR
ADVECTION DURING THIS TIME...BUT CLOUD COVER WILL KEEP TEMPS
MODERATED...WITH HIGHS IN THE UPPER 20S.
.LONG TERM...
SUNDAY THROUGH THURSDAY...FORECAST CONFIDENCE...MEDIUM.
SOME SUNSHINE IS EXPECTED ON SUNDAY. LOW PRESSURE WILL TRACK ACROSS
LAKE SUPERIOR SUN NIGHT AND THE ASSOCIATED COLD FRONT WILL CROSS
SOUTHERN WI MON MORNING...USHERING COLDER AIR INTO THE AREA. A
PERIOD OF CLOUDS WILL BE LIKELY WITH THIS FRONTAL PASSAGE.
ANOTHER WEAK WAVE WILL MOVE THROUGH THE UPPER GREAT LAKES AREA WED
MORNING WHICH MAY PRODUCE SOME LIGHT SNOW OR FLURRIES. THE ECMWF IS
DRY AND THE GFS SHOWS VERY LIGHT QPF.
&&
.AVIATION/12Z TAFS/...
TIME HEIGHT SECTIONS FROM BOTH GFS AND NAM NOW SHOW STRATUS
REMAINING IN PLACE IN SOUTHEAST THROUGH TONIGHT. SHOULD BE NO WORSE
THAN MVFR AND LIKELY TO IMPROVE A TAD TO LOWER END VFR CEILINGS
LATER TODAY INTO TONIGHT. MOST UNCERTAINTY IS KMSN...WHERE THE
GUIDANCE SHOWS THE STRATUS DECK VANISHING WITHIN THE NEXT FEW
HOURS.
FOG PRODUCT TRENDS AND SURFACE OBSERVATIONS DO NOT SUPPORT THIS
TREND. THUS...WILL EXTEND THE VFR CEILING A BIT LONGER INTO THE
MIDDAY HOURS BEFORE GOING WITH SCATTERED LOWER DECK.
REGARDLESS OF WHAT HAPPENS TO LOWER DECK EXPECT MID LEVEL CLOUDS TO
MOVE IN QUICKLY AROUND 00Z AND GRADUALLY LOWER WITH A GOOD THREAT
FOR VIRGA/SNOW ALOFT IN THE 06Z TO 12Z PERIOD...ESPECIALLY IN KMSN.
SNOW SHOULD START AROUND 12Z IN KMASN AND THEN SPREAD TO SOUTHEAST
WI STAFFS AROUND 18Z. PROLONGED IFR CONDITIONS LIKELY WITH THE
LIGHT SNOW.
&&
.MARINE...
NORTH TO NORTHWEST WINDS ARE NEAR SMALL CRAFT LEVELS NOW BUT SHOULD
GRADUALLY DIMINISH TODAY. WITH OFFSHORE FLOW THE WAVES ARE ALREADY
DIMINISHING BUT SHOULD REMAIN ABOVE 4 FEET UNTIL LATE AFTERNOON.
PER COORDINATION WITH GRB AND LOT WILL END SMALL CRAFT ADVISORY
ABOUT 9 HOURS EARLIER THAN PREVIOUS FORECASTS...AT 00Z TODAY.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 6 PM CST THIS EVENING FOR LMZ643>646.
&&
$$
TODAY/TONIGHT AND AVIATION/MARINE...MRC
FRIDAY THROUGH WEDNESDAY...CRAVEN
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
209 AM CST THU DEC 27 2012
.SHORT TERM...
209 AM CST THU DEC 27 2012
FORECAST FOCUS PRIMARILY ON SNOW AMOUNTS TONIGHT INTO FRIDAY
AND THE NEED FOR AN ADVISORY.
07Z SURFACE ANALYSIS SHOWS THE HIGH PRESSURE RIDGE RUNNING FROM
WESTERN ONTARIO DOWN THROUGH MN/IA/MO. AIR MASS IS RATHER `DIRTY`
UNDER THE RIDGE...WITH VARIOUS PATCHES OF LOW/MID/HIGH CLOUD.
SATELLITE WATER VAPOR IMAGERY SHOWS THE NEXT CLOSED CIRCULATION
AND LONG WAVE TROUGH MOVING ALONG THE WY/CO BORDER TOWARD THE
NE PANHANDLE. THE CIRCULATION IS ALSO EVIDENT ON THE FOG
ENHANCEMENT IMAGERY NEAR CHEYENNE. LOW CLOUDS WERE ALREADY
DEVELOPING AHEAD OF THIS NEXT SYSTEM AND HAVE REACHED AS FAR
EAST AS NORTHWEST IA. OTHER ITEM OF NOTE IS ALL OF THE STRATUS
ACROSS WI/IL BEHIND THE WINTER STORM MOVING THROUGH THE NORTHEAST.
THE WESTERN EDGE OF THE CLOUD SHIELD HAD BEEN MAKING GOOD WESTWARD
PROGRESS TONIGHT...BUT HAS SLOWED THE LAST FEW HOURS AS IT NEARED
THE RIDGE AXIS.
MODEL SOLUTIONS ARE IN GOOD AGREEMENT IN TRACKING THE DISTURBANCE
ACROSS NE TODAY AND THROUGH NORTHERN IA LATE TONIGHT AND FRIDAY.
AIR MASS IN PLACE OVER OUR REGION IS VERY COLD...AND THIS WILL HELP
THE SYSTEM TO MAKE GOOD USE OF WHATEVER MOISTURE IT HAS. ALSO...
THE SLOW MOVEMENT AND STORM TRACK WILL KEEP THE FORECAST AREA IN
THE BEST POSITION FOR A LONGER DURATION OF SNOWFALL STARTING LATE
TODAY AND PERSISTING WELL INTO THE DAYLIGHT HOURS ON FRIDAY. MODEL
SOUNDINGS INDICATE THERE WILL BE SOME DRY AIR TO OVERCOME AS THE
SNOW BEGINS...BUT FEEL THIS IS OVERDONE. MODELS HAVE BEEN HAVING A
TERRIBLE TIME WITH THE LOW CLOUDS/MOISTURE OF LATE...AND DO NOT
FEEL IT WILL SLOW DOWN THE SNOW TOO MUCH. SO...EXPECTING A
PROTRACTED 18-24 HOUR PERIOD OF LIGHT SNOW...AND WITH THE COOL
TEMPS PROVIDING RATIOS AROUND 15:1 OR PERHAPS AS HIGH AS
18:1...EXPECT A GENERAL 1-3 INCHES OF SNOW...WITH A FEW SPOTS
PERHAPS SEEING 4 INCHES. WITH THESE AMOUNTS WAS CONSIDERING THE
NEED FOR A WINTER WEATHER ADVISORY FOR LOCATIONS MAINLY ALONG AND
SOUTH OF INTERSTATE 90. BUT THE FACT THAT THE SNOW DOES NOT APPEAR
TO BE FALLING AT A HIGH RATE FOR ANY LENGTH OF TIME LEADS ME TO
HOLD OFF ON THE ADVISORY AT THIS POINT. WILL OPT INSTEAD TO
ENHANCE THE WORDING IN THE HAZARDOUS OUTLOOK AND ISSUE A SPECIAL
WEATHER STATEMENT.
THE DISTURBANCE EXITS THE AREA LATE FRIDAY...BUT A FEW WEAKER
SHORT WAVE TROUGHS LOOK TO DROP INTO THE BACK SIDE OF THE MAIN
UPPER LONG WAVE TROUGH...AND THESE WILL CROSS OUR AREA ON
SATURDAY. THIS COULD RESULT IN SOME SCATTERED FLURRIES...SO WILL
LEAVE MENTION IN THE FORECAST PER YESTERDAY.
.LONG TERM...
209 AM CST THU DEC 27 2012
THE LATEST MEDIUM RANGE MODELS CONTINUE TO POINT TO A PROGRESSIVE
WEATHER PATTERN INTO EARLY NEXT WEEK. BEHIND OUR DEPARTING
TROUGH A BRIEF PERIOD OF RIDGING WILL PREVAIL ON SUNDAY...ONLY TO
BE REPLACED BY ANOTHER TROUGH MOVING FROM SASKATCHEWAN DOWN
INTO LAKE SUPERIOR BY MONDAY. THE MAIN FORCING AND MOISTURE FROM
THIS SYSTEM LOOK TO REMAIN TOO FAR NORTH FOR ANY SNOW IN OUR AREA.
MEANWHILE A LARGER LONG WAVE TROUGH SETS UP ALONG THE WEST COAST.
THE MODELS CONTINUE TO STRUGGLE WITH HOW TO EVOLVE THIS FEATURE...
ALTHOUGH THEY ARE BEGINNING TO CONVERGE SOMEWHAT. ONE CAMP OF
MODEL SOLUTIONS LED BY THE ECMWF KEEP A SLOW-MOVING CLOSED
CIRCULATION OVER AZ/NM TUE INTO WED...WHILE ANOTHER GROUP OF
SOLUTIONS KEEP THE TROUGH OPEN AND MOVE IT EAST THROUGH THE
SOUTHERN PLAINS BY MID-WEEK. EITHER WAY...THE BULK OF THAT FEATURE
LOOKS TO REMAIN WELL SOUTH OF THE FORECAST AREA. OUR WEATHER WILL
COME FROM THE NORTHWEST FLOW REGIME OVER THE UPPER MIDWEST AND
GREAT LAKES REGION. THE NEXT DISTURBANCE LOOKS TO ARRIVE LATE
TUESDAY INTO WEDNESDAY. BUT ONCE AGAIN...THE BULK OF THE MOISTURE
AND SUPPORT LOOK TO PASS TO THE NORTH. THE OVERALL EVOLUTION OF
THE SOUTHERN STREAM MAY ALTER THIS SLIGHTLY...SO WILL NEED TO
MONITOR. BUT MEANWHILE...ANTICIPATE COOL AND MAINLY SNOW FREE
CONDITIONS TO PREVAIL.
&&
.AVIATION...THROUGH 06Z FRIDAY
1119 PM CST WED DEC 26 2012
LARGE AREA OF MVFR STRATUS CLOUDS OVER EASTERN WISCONSIN HAS BEEN
WORKING STEADILY WEST THIS EVENING. NONE OF THE MODELS HAVE A REAL
GOOD HANDLE ON THIS CLOUD FIELD BUT THE 27.03Z RAP AT LEAST HAS AN
IDEA IT IS THERE. GIVEN THE CURRENT MOVEMENT OF THE CLOUD
FIELD...THE RAP LOOKS TO BE TOO SLOW MOVING THE CLOUDS WEST...BUT
IT DOES INDICATE THAT THE CLOUDS SHOULD MAKE IT INTO BOTH TAF
SITES. HAVE ALREADY UPDATED THE KLSE TAF TO BRING THESE CLOUDS IN
AND WILL SHOW THEM ARRIVING IN KRST BEFORE 12Z. THE RAP WOULD
SUGGEST THAT ONCE THE CLOUDS ARE IN PLACE THEY SHOULD REMAIN
THROUGH THURSDAY AND WILL SHOW THIS TREND. THE FORCING FROM THE
SHORT WAVE TROUGH MOVING OUT OF THE CENTRAL ROCKIES WILL START TO
MOVE IN EARLY THURSDAY EVENING. THE MVFR CLOUD DECK WILL HELP TO
AID IN THE LOW LEVEL SATURATION SO EXPECT THIS WAVE TO BE ABLE TO
START PRODUCING LIGHT SNOW FAIRLY QUICKLY. WILL SHOW THE LIGHT
SNOW AT KRST STARTING AT 28.00Z WITH THE VISIBILITY GOING DOWN TO
IFR IN THE SNOW BY THE MIDDLE OF THE EVENING. WILL BRING THE LIGHT
SNOW IN KLSE BY THE MIDDLE OF THE EVENING AND WILL HOLD ONTO A VFR
VISIBILITY BUT COULD SEE THIS GO DOWN TO MVFR OR IFR BEFORE 28.06Z.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
209 AM CST THU DEC 27 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...MW
LONG TERM...MW
AVIATION...04
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1119 PM CST WED DEC 26 2012
.SHORT TERM...TODAY THROUGH SATURDAY
315 PM CST WED DEC 26 2012
MAIN FORECAST CONCERNS ARE ON SNOW ACCUMULATIONS THURSDAY NIGHT
THROUGH FRIDAY.
LATEST WATER VAPOR IMAGERY SHOWED A VIGOROUS UPPER LOW LIFTING
NORTHEAST THROUGH THE MID APPALACHIANS. A SHORTWAVE WAS MOVING
ACROSS CENTRAL CALIFORNIA HEADING EAST TOWARDS THE CENTRAL ROCKIES.
SURFACE OBSERVATIONS SHOWED HIGH PRESSURE CENTERED OVER SOUTHEAST
MANITOBA WITH THE RIDGE AXIS EXTENDING SOUTH THROUGH THE UPPER
MISSISSIPPI RIVE VALLEY. THE PRESSURE GRADIENT WAS TIGHTENING ACROSS
SOUTHEAST WISCONSIN AS THE VIGOROUS LOW MOVES THROUGH THE
APPALACHIANS.
THE HIGH WILL REMAIN IN CONTROL TONIGHT THROUGH THURSDAY MORNING
PROVIDING QUIET WEATHER. LOW TEMPERATURES TONIGHT WILL BE A LITTLE
TRICKY WITH THE CLOUDS STREAMING IN FROM THE SOUTHEAST. LOW
TEMPERATURES TONIGHT ARE EXPECTED TO FALL INTO THE SINGLE
DIGITS...WITH FAVORED COLD SPOTS SUCH AS BLACK RIVER
FALLS...SPARTA...AND DIAMOND LAKE FALLING INTO THE SINGLE DIGITS
BELOW ZERO. IF CLOUDS HOLD ON ACROSS CENTRAL INTO FAR SOUTHWEST
WISCONSIN HIGHS COULD POSSIBLY END UP A FEW DEGREES WARMER THAN
FORECAST. CLOUDS WILL BE ON THE INCREASE ACROSS THE AREA ON
THURSDAY AS THE SHORTWAVE EJECTS OUT OF THE CENTRAL ROCKIES AND
MOVES ACROSS SOUTH DAKOTA AND NEBRASKA. PLAN ON HIGHS ON THURSDAY
RANGING FROM LOWER 20S OVER NORTH CENTRAL WISCONSIN TO THE MID 20S
OVER FAR SOUTHWEST WISCONSIN INTO NORTHEAST IOWA.
THE SHORTWAVE IS EXPECTED TO TRACK ACROSS SOUTHERN
MINNESOTA/NORTHERN IOWA THURSDAY NIGHT AND EAST INTO SOUTHERN
WISCONSIN/NORTHERN ILLINOIS EARLY FRIDAY MORNING INTO FRIDAY
AFTERNOON. ISENTROPIC LIFT INCREASES ACROSS THE FORECAST AREA LATE
THURSDAY AFTERNOON INTO THURSDAY EVENING...ON THE 280-305 K
SURFACES. ALSO...MODEST FRONTOGENESIS...ON THE 700-500MB LAYER
INCREASES ACROSS NORTHEAST IOWA AND FAR SOUTHEAST WISCONSIN THURSDAY
EVENING INTO FRIDAY MORNING. NAM/GFS/ARW ARE ALL SHOWING AN ENHANCED
SNOW BAND ACROSS NORTHEAST IOWA INTO FAR SOUTHWEST WISCONSIN. OMEGA
IN THE DENDRITIC GROWTH ZONE INCREASES INTO THE -4 TO -6.9 UBAR/S
RANGE THURSDAY EVENING THEN CONTINUES OVERNIGHT. IT ALSO APPEARS
THAT THE DENDRITIC GROWTH ZONE WILL BE AROUND 100 TO 150 MB DEEP.
THINKING SNOW RATIOS WILL BE RATHER HIGH...RANGING FROM 15:1 TO
20:1. SNOW WILL DEVELOP ACROSS LOCATIONS WEST OF THE MISSISSIPPI
RIVER EARLY THURSDAY EVENING AND WILL THEN SPREAD EAST OF THE
MISSISSIPPI LATE THURSDAY EVENING INTO THE OVERNIGHT HOURS. AT THIS
TIME 1 TO 3 INCHES LOOKS LIKELY ALONG AND SOUTH OF THE INTERSTATE 90
CORRIDOR BY LATE FRIDAY MORNING. LOCALLY HIGHER AMOUNTS UP TO 4
INCHES ARE POSSIBLE ACROSS NORTHEAST IOWA INTO FAR SOUTHWEST
WISCONSIN WHERE THE STRONGER FRONTOGENESIS BAND WILL BE IN PLACE.
LOCATIONS NORTH OF INTERSTATE 90 CORRIDOR TO AROUND WISCONSIN
HIGHWAY 10 WILL SEE ACCUMULATIONS OF 1 TO 2 INCHES. NORTH OF HIGHWAY
10 PLAN ON SNOWFALL AMOUNTS OF AROUND AN INCH. A WINTER WEATHER
ADVISORY WILL LIKELY BE NEEDED FOR LOCATIONS ALONG AND SOUTH OF THE
INTERSTATE 90 CORRIDOR THURSDAY NIGHT THROUGH EARLY FRIDAY
AFTERNOON.
THE SHORTWAVE WILL PUSH INTO EASTERN WISCONSIN FRIDAY NIGHT BUT LOW
LEVEL MOISTURE WILL LINGER OVER THE FORECAST AREA. A SECONDARY WAVE
WILL IS EXPECTED TO MOVE ACROSS THE REGION SATURDAY NIGHT PRODUCING
FLURRIES OVER MUCH OF THE AREA. THE FLURRIES WILL PERSIST THROUGH
SATURDAY MAINLY EAST OF THE MISSISSIPPI RIVER. PLAN ON LOWS FALLING
INTO THE TEENS FRIDAY NIGHT. LOOK FOR HIGHS ON SATURDAY TO RANGE
FROM THE LOWER 20S OVER SOUTHEAST MINNESOTA TO THE MID TO UPPER 20S
ACROSS CENTRAL WISCONSIN.
.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY
315 PM CST WED DEC 26 2012
26.12 MEDIUM RANGE MODELS ARE IN AGREEMENT SATURDAY NIGHT THROUGH
SUNDAY SHOWING HIGH PRESSURE BUILDING ACROSS THE UPPER MISSISSIPPI
RIVER WITH DRY AND QUIET CONDITIONS EXPECTED. MEANWHILE A TROUGH
WILL DIG INTO THE DESERT SOUTHWEST. A NORTHERN STREAM TROUGH LOOKS TO
DROP SOUTH OUT OF SOUTHERN MANITOBA SASKATCHEWAN SUNDAY NIGHT. THE
TROUGH IS EXPECTED TO MOVE ACROSS LAKE SUPERIOR AND NORTHERN
WISCONSIN ON MONDAY. THE ECMWF AND GFS START TO DIVERGE MONDAY INTO
WEDNESDAY. THE ECMWF CUTS THE LOW OFF OVER THE DESERT SOUTHWEST
WHILE THE GFS IS PROGRESSIVE AND TAKES THE LOW EAST THROUGH THE
SOUTHERN PLAINS. WILL LEAN TOWARD A MODEL CONSENSUS BLEND MONDAY
THROUGH WEDNESDAY. KEEPING A CLOSE WATCH ON THE WAVE MOVING THROUGH
THE AREA ON MONDAY OTHERWISE PLAN ON QUIET CONDITIONS WITH HIGHS IN
THE 20S AND LOWS IN THE SINGLE DIGITS.
&&
.AVIATION...THROUGH 06Z FRIDAY
1119 PM CST WED DEC 26 2012
LARGE AREA OF MVFR STRATUS CLOUDS OVER EASTERN WISCONSIN HAS BEEN
WORKING STEADILY WEST THIS EVENING. NONE OF THE MODELS HAVE A REAL
GOOD HANDLE ON THIS CLOUD FIELD BUT THE 27.03Z RAP AT LEAST HAS AN
IDEA IT IS THERE. GIVEN THE CURRENT MOVEMENT OF THE CLOUD
FIELD...THE RAP LOOKS TO BE TOO SLOW MOVING THE CLOUDS WEST...BUT
IT DOES INDICATE THAT THE CLOUDS SHOULD MAKE IT INTO BOTH TAF
SITES. HAVE ALREADY UPDATED THE KLSE TAF TO BRING THESE CLOUDS IN
AND WILL SHOW THEM ARRIVING IN KRST BEFORE 12Z. THE RAP WOULD
SUGGEST THAT ONCE THE CLOUDS ARE IN PLACE THEY SHOULD REMAIN
THROUGH THURSDAY AND WILL SHOW THIS TREND. THE FORCING FROM THE
SHORT WAVE TROUGH MOVING OUT OF THE CENTRAL ROCKIES WILL START TO
MOVE IN EARLY THURSDAY EVENING. THE MVFR CLOUD DECK WILL HELP TO
AID IN THE LOW LEVEL SATURATION SO EXPECT THIS WAVE TO BE ABLE TO
START PRODUCING LIGHT SNOW FAIRLY QUICKLY. WILL SHOW THE LIGHT
SNOW AT KRST STARTING AT 28.00Z WITH THE VISIBILITY GOING DOWN TO
IFR IN THE SNOW BY THE MIDDLE OF THE EVENING. WILL BRING THE LIGHT
SNOW IN KLSE BY THE MIDDLE OF THE EVENING AND WILL HOLD ONTO A VFR
VISIBILITY BUT COULD SEE THIS GO DOWN TO MVFR OR IFR BEFORE 28.06Z.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
315 PM CST WED DEC 26 2012
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...WETENKAMP
LONG TERM...WETENKAMP
AVIATION...04
AREA FORECAST DISCUSSION
NWS DENVER/BOULDER CO
913 PM MST FRI DEC 28 2012
.UPDATE...
NO BIG CHANGES THIS EVENING FOR THE FORECAST. GUSTY WINDS OVER THE
HIGH MOUNTAIN PASSES OF THE FRONT RANGE MOUNTAINS ARE COMBINING
WITH COLD TEMPERATURES TO CREATE WIND CHILL READINGS OF AROUND 30
DEGREES BELOW ZERO. ADDED THESE TO THE GRIDS...THOUGH THESE
CONDITIONS ARE NOT EXPECTED TO LAST MUCH PAST MIDNIGHT AS THE
WINDS WILL BE DECREASING.
&&
.AVIATION...NO BIG CHANGES EXPECTED FOR THE ONGOING TAFS WITH VFR
CONDITIONS THROUGH SATURDAY. DRAINAGE WINDS STILL EXPECTED FOR
THE AIRPORTS TONIGHT WITH SOME WESTERLY GUSTS AT KBJC. ON
SATURDAY...MODELS CONTINUE TO HINT AT A WEAK CYCLONE DEVELOPING
AROUND OR NORTH OF THE DENVER AREA BY 18Z. THUS...LIGHT SOUTH TO
SOUTHEASTERLY WINDS SHOULD PREVAIL AT THE AREA AIRPORTS THROUGH
THE DAY... PERHAPS MORE EAST TO NORTHEAST AT KDEN DEPENDING ON
WHERE THE CYCLONE SETS UP. VFR TO CONTINUE WITH UNLIMITED
CEILINGS.
&&
.PREV DISCUSSION... /ISSUED 255 PM MST FRI DEC 28 2012/
SHORT TERM...LATEST WATER VAPOR AND IR LOOPS SUGGESTING A WEAK
SHORTWAVE CURRENTLY MOVING ACROSS AREA AS NOTED BY SOME CLOUD
ENHANCEMENT. HOWEVER...WEB CAMS SHOW THE LIGHT SNOW CONFINED TO
AREAS ALONG THE CONTINENTAL DIVIDE AS WELL AS ACROSS THE PARK
RANGE IN WESTERN JACKSON COUNTY. SOME GUSTY WINDS ACROSS THE
HIGHER MOUNTAINS AND OVER THE NORTHERN FOOTHILLS WITH A FEW GUSTS
AROUND 35 MPH. LATEST MODELS SHOW THE SHORTWAVE MOVING EAST OF THE
AREA DURING THE EVENING WITH THE FLOW ALOFT BECOMING MORE NORTH
NORTHWEST. CROSS SECTIONS INDICATE A DECREASE IN MOISTURE WITH
INCREASING SUBSIDENCE. SHOULD SEE MOUNTAIN SNOW COMING TO AN END
BY MIDNIGHT WITH CLEARING SKIES. WINDS TO REMAIN A BIT GUSTY INTO
THE EVENING...BEFORE DECREASING AROUND MIDNIGHT. CLEARING SKIES...
LIGHT WINDS AND SNOW COVER WILL ALLOW FOR THE DEVELOPMENT OF
INVERSIONS IN THE MOUNTAIN VALLEYS AS WELL AS LOW LYING AREAS
ACROSS THE PLAINS. THUS...SHOULD GET QUITE COLD IN THESE AREAS
OVERNIGHT WITH TEMPERATURES BELOW ZERO ESPECIALLY THE KREMMLING
AREA IN GRAND COUNTY. ON SATURDAY...UPPER LEVEL RIDGE BUILDS OVER
COLORADO WITH FLOW ALOFT BECOMING MORE WESTERLY. 7H TEMPERATURES
WARM ABOUT 6-8 DEGREES CELSIUS FROM TODAY`S READINGS. THUS SHOULD
SEE WARMER TEMPERATURES ACROSS MUCH OF THE AREA WITH MAINLY CLEAR
SKIES. HOWEVER...INVERSIONS WILL LIMIT THE WARMUP...ESPECIALLY IN
THE MOUNTAIN VALLEYS. TEMPERATURES ACROSS THE PLAINS TO BE MAINLY
IN THE 30S...WITH MID TO UPPER 20S IN THE GREELEY AREA. WINDS
ALOFT TO BE FAIRLY LIGHT...WITH SOME GUSTY WINDS POSSIBLE ACROSS
THE HIGHER RIDGES.
LONG TERM...SOUTHWEST FLOW ALOFT WILL PREVAIL SATURDAY NIGHT AND
SUNDAY AS AN UPPER LEVEL TROUGH MOVES ONTO THE WEST COAST. THE
TROUGH WILL CONTINUE TO DIG SOUTHEAST AND BE CENTERED OVER THE
SOUTHWESTERN STATES SUNDAY NIGHT. EXPECT A COLD NIGHT IN THE
MOUNTAIN VALLEYS SATURDAY NIGHT UNDER MOSTLY CLEAR SKIES. LOWS
SHOULD DROP BELOW ZERO IN THE MOUNTAIN VALLEYS. CLOUDS WILL INCREASE
DURING THE DAY SUNDAY AS MID AND HIGH LEVEL MOISTURE INCREASE WITH
THE APPROACH OF THE UPPER LEVEL TROUGH.
STILL A LOT OF DIFFERENCES AMONG THE MODELS ON THE TRACK OF THE
UPPER LEVEL TROUGH. THE LATEST ECMWF AND NAM ARE STARTING TO NUDGE
THE TRACK MORE NORTHERLY. MEANWHILE THE GFS CONTINUES TO FAVOR A
SOUTHERLY TRACK ACROSS THE SOUTHERN ROCKIES. BECAUSE OF THIS
NORTHERLY SHIFT...WILL INCREASE POPS ACROSS THE AREA FOR SUNDAY
NIGHT AND MONDAY. WILL HAVE LIKELY POPS FOR THE MOUNTAINS NEAR AND
SOUTH OF I-70. EVEN THE SOUTHERLY TRACK OF GFS SHOWS SNOW FOR THE
CENTRAL AND SOUTHERN MOUNTAINS OF COLORADO. WILL HAVE CHANCE TO
SLIGHT CHANCE ELSEWHERE. AS THIS SYSTEM NEARS...LATER SHIFTS CAN
TREND UP OR DOWN AS THE TRACK OF THE TROUGH BECOMES MORE CLEAR.
EXPECT HIGH TEMPERATURES TO BE COOL MONDAY AND TUESDAY UNDERNEATH
THIS SYSTEM.
ONCE THE TROUGH EXITS THE REGION...QUIET WEATHER WILL PREVAIL. EVEN
THOUGH MODELS ARE SHOWING DIFFERENT UPPER LEVEL PATTERN...ALL OF THE
DIFFERENT SOLUTIONS WOULD RESULT IN COOL AND DRY CONDITIONS.
THEREFORE WILL CONTINUE WITH THE COOL AND DRY CONDITIONS CURRENTLY
IN THE FORECAST.
AVIATION...WINDS HAVE TRENDED TOWARD LIGHT EASTERLY ACROSS THE
AREA AIRPORTS. LATEST RUC AND HRRR INDICATING WINDS TO BECOME
NORTHWEST BY 00Z...THEN SOUTHWESTERLY BY 03Z AS DRAINAGE FLOW
DEVELOPS. THIS TREND SEEMS REASONABLE THOUGH THE DIRECTION WILL BE
MORE WESTERLY AT BJC. ON SATURDAY...MODELS HINT AT A WEAK CYCLONE
DEVELOPING NORTH OF THE DENVER AREA BY 18Z. THUS...LIGHT SOUTHERLY
WINDS SHOULD PREVAIL AT THE AREA AIRPORTS THROUGH THE DAY...
PERHAPS MORE SOUTHEAST AT DEN. VFR TO CONTINUE WITH UNLIMITED
CEILINGS.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...D-L
LONG TERM....MEIER
AVIATION...KRIEDERMAN
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
434 AM EST SAT DEC 29 2012
.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE AREA BEHIND A COLD FRONT TODAY.
ANOTHER FRONTAL SYSTEM WILL DROP INTO THE SOUTHEAST UNITED STATES
TUESDAY AND PERSIST IN THE VICINITY THROUGH THURSDAY NIGHT. HIGH
PRESSURE WILL BUILD BACK IN FOR LATE NEXT WEEK INTO THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
PRE-DAWN...RAINFALL WASTED NO TIME DEVELOPING AFTER MIDNIGHT AS THE
SYNOPTIC SYSTEM MOVING THROUGH THE REGION IS QUITE DYNAMIC WITH A
110 KT JET AT 500 MM BLASTING THROUGH THE LOWER GULF COAST AREA.
THE RUC HAS A GOOD HANDLE ON THE POCKET OF BEST MID LEVEL INSTABILITY
OVER THE NORTHERN HALF OF FLORIDA AND FAIRLY UNSTABLE MID LEVELS
ARE PROGGED TO SHIFT NE OVER THE EASTERN PART OF OUR FORECAST AREA
AROUND DAYBREAK. WE WILL CONTINUE TO MENTION ISOLATED THUNDER AT
FORECAST INITIALIZATION TIME BUT THE WINDOW IS VERY SMALL. WAVES
OF LOW PRES MOVING THROUGH...BUT RISK FOR ANY SURFACE BASED INSTABILITY
LOOKS TO STAY TO OUR S ANCHORED BY THE WIDESPREAD RAIN CURRENTLY
FALLING IN OUR AREA.
TODAY...SECONDARY LOW PRES DEVELOPING OVER FORECAST AREA IS FORECAST
TO RACE NE ALONG THE SOUTH CAROLINA COAST NEAR DAYBREAK THEN DEEPEN
ALONG THE NORTH CAROLINA OUTER BANKS AT MIDDAY. WIDESPREAD RAINFALL
IS FORECAST TO QUICKLY END BETWEEN 7 AM AND 10 AM AS THE ATTENDANT
COLD FRONT RACES OFF OUR COAST AND A STRONG DRY SLOT BLASTS IN FROM
THE W TO SW OVER GEORGIA AND SOUTH CAROLINA. WE THINK RAIN WILL BE
OVER FOR ALL OF OUR REGION PRIOR TO NOON AT THE RATE THE BACK EDGE
OF THE PCPN SHIELD IS ADVANCING. DOWNSLOPING POST-FRONTAL LOW
LEVEL FLOW AND BUILDING MID LEVEL SUBSIDENCE SHOULD RESULT IN
RAPID CLEARING BY THIS AFTERNOON. TEMPS LATER TODAY SHOULD RANGE
FROM THE MID 50S CLOSE TO THE CSRA AND SE MIDLANDS TO THE LOWER
60S CLOSE TO THE COAST...MAX READINGS A COUPLE OF DEGREES WARMER.
IT WILL BECOME BREEZY TODAY ESPECIALLY AFTER THE SUNSHINE COMMENCES
AND MIXING IMPROVES.
WE HAVE ISSUED A LAKE WIND ADVISORY FOR GUSTY W WINDS 15 TO 25 KT
THIS AFTERNOON...MOST PREVALENT ALONG LAKE SHORES.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
A MODIFYING CONTINENTAL POLAR AIR MASS WILL BEGIN TO TAKE HOLD TONIGHT
AS SURFACE HIGH PRES WORKS IN FROM THE W. MAINLY CLEAR SKIES AND
STIRRING W TO NW SURFACE WINDS WILL DRIVE IN COLDER AIR WITH TIME.
MANY INLAND AREAS LIKELY TO BE NEAR OR EVEN SLIGHTLY BELOW FREEZING
BY DAYBREAK SUNDAY.
LAKE WIND ADVISORY TO CONTINUE THROUGH THE EVENING OVER LAKE MOULTRIE
AS WINDS AND WAVES PEAK IN THE EVENING AS COLD AIR ADVECTION AND
MIXING PARAMETERS SUGGEST FREQUENT GUSTS OVER OPEN LAKE WATERS
REACHING 25 KT.
A PRONOUNCED MID-LEVEL RIDGE WILL BUILD ACROSS THE AREA SUNDAY AND
MONDAY WITH SURFACE HIGH PRESSURE MODIFYING AS IT SHIFTS EAST. COLD
ADVECTION ON SUNDAY WILL KEEP HIGH TEMPS IN THE LOWER 50S. HOWEVER
BY MONDAY AS THE SURFACE RIDGE SHIFTS EAST...THE COLD ADVECTION WILL
ABATE. A WEAK COASTAL TROUGH MAY DEVELOP OFF THE GA COAST LATE
MONDAY AFTERNOON...PRODUCING ISOLATED RAIN SHOWERS OVER THE ADJACENT
WATERS. WE WILL ALSO SEE AN INCREASE IN HIGH CLOUDS AS THE DAY WEARS
ON. TEMPS SHOULD REBOUND NICELY WITH HIGHS REACHING 60-63F.
MONDAY NIGHT INTO TUESDAY THE UPPER PATTERN TRANSITIONS TO A BROAD
TROUGH ACROSS THE EASTERN UNITED STATES. SOME ELONGATED VORTICITY
ENERGY LIFTING ACROSS THE CAROLINAS WILL PUSH A SPRAWLING FRONT INTO
THE AREA FROM THE NORTHWEST ON TUESDAY. THE LATEST PROGS SHOW A
SLOWER PROGRESSION FOR THE ASSOCIATED RAIN SHOWERS SO WE BACKED OFF
ON POPS A BIT MONDAY NIGHT AND TUESDAY MORNING. WE NOW SHOW CHANCE
POPS SPREADING INTO INLAND AREAS TUESDAY AFTERNOON. HIGH TEMPS COULD
REALLY VARY BASED ON THE SPEED OF THE FRONT AND HOW EARLY THE RAIN
MAKES IT IN. GUIDANCE INDICATES FAIRLY STRONG LOW-LEVEL WARM
ADVECTION IN ADVANCE OF THE FRONT SO WE BUMPED HIGHS INTO THE
MID/UPPER 60S ACROSS THE SOUTHERN TWO-THIRDS OF THE AREA WITH LOWER
60S FARTHER NORTH.
&&
.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
TUESDAY NIGHT THROUGH THURSDAY NIGHT LOOK FAIRLY ACTIVE DUE TO A
PLETHORA OF UPPER DISTURBANCES RIPPLING THROUGH THE BROAD EASTERN
UNITED STATES TROUGH. A WEAK FRONT SHOULD REMAIN DRAPED ACROSS THE
FORECAST AREA WITH NUMEROUS SURFACE WAVES RIDING ALONG IT. WE KEPT
CHANCE POPS IN THE FORECAST THROUGH THURSDAY...TAPERING OFF THURSDAY
NIGHT. COOL...DRY HIGH PRESSURE WILL BUILD IN FRIDAY THROUGH
SATURDAY.
&&
.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
CONDITIONS THEN DETERIORATING THIS MORNING AS RAINS QUICKLY BREAKING
OUT AND SWEEPING ENE. A WARM FRONT WILL LIFT NORTH THROUGH THE
TERMINALS WITH A 40-50 KT LOW-LEVEL JET INITIATING LOW-LEVEL WIND
SHEAR /LLWS/ AT BOTH TERMINALS AFTER 08-09Z. THE RISK FOR LLWS
WILL LINGER UNTIL THE PASSAGE OF A COLD FRONT ROUGHLY AROUND
14-15Z. A WELL DEFINED RAIN BAND WILL ACCOMPANY THE FRONT WITH
RAIN REACHING THE TERMINALS AS EARLY AS 08-09Z. EXPECT MVFR
CEILINGS TO PREVAIL WITH OCCASIONAL REDUCTIONS IN VISIBILITIES DUE
TO THE RAIN GENERALLY IN THE 08-15Z TIME FRAME. HAVE MAINTAINED
TEMPORARY IFR CEILINGS AT BOTH TERMINALS ANYWHERE FROM ABOUT
09-13Z. EXPECT RAPID CLEARING TO ENSUE ONCE THE FRONT SHIFTS
OFFSHORE AND DOWNSLOPE TRAJECTORIES TAKE HOLD.
EXTENDED AVIATION OUTLOOK...INCREASING CHANCES FOR SUB-VFR
CONDITIONS LATE TUESDAY AND WEDNESDAY AS A COLD FRONT DROPS SOUTH
INTO THE AREA.
&&
.MARINE...
A POTENT WARM FRONT IS FORECAST TO PUNCH THROUGH THE WATERS PRIOR
TO DAWN WITH A STRONG SW LOW LEVEL JET SHIFTING OVERHEAD. IT IS
A VERY COMPLEX COASTAL WATERS FORECAST THIS MORNING DUE TO VARYING
SEA SURFACE TEMPS FROM THE COAST TO 60 NM OFFSHORE. THIS EFFECTS
THE MIXING POTENTIAL OF THESE STRONG WINDS AND OUR FORECAST APPEARS
TO HAVE A REASONABLE HANDLE ON TIMING AND TRENDS. WATCHING STRONG
CONVECTION MOVING OUT OF NE FLORIDA EARLY THIS MORNING AND THERE
COULD BE A RISK FOR STRONG GUSTY WINDS WITH STORMS OVER WATERS
PRIOR TO DAYBREAK. CLOSE TO THE GULF STEAM WELL SE OF SAVANNAH
THERE COULD BE A VERY BRIEF PERIOD OF SOUTHERLY GALES AS WELL.
AFTER MID MORNING...THERE WILL PROBABLY BE A BIT OF A POST-FRONTAL
LULL AS DIRECTIONS SHIFT W. SPEEDS WILL BE RAMPING UP AGAIN THIS
AFTERNOON AS COOLER AND DRIER AIR ADVECTS INTO THE REGION. TONIGHT
WE HAVE ISSUED SMALL CRAFT ADVISORIES ALL WATERS AS W TO NW SURGING
LOOKS STRONG ENOUGH TO PRODUCE FREQUENT GUSTS OVER 25 KT WITH THE
STRONGEST FLOW OFF THE GEORGIA COAST DUE TO FAVORABLE JETTING
PROFILES. SEA HEIGHTS THROUGH TONIGHT DIFFICULT TO PIN DOWN AS
MIXING PROFILES START OFF VERY POOR THIS MORNING AND THEN BECOME
QUITE FAVORABLE TONIGHT. WE HAVE MADE SOME ADJUSTMENTS TO WAVE
WATCH OUTPUT OVER GEORGIA WATERS THIS EVENING AS FORECAST HEIGHTS
AROUND GRAYS REEF APPEAR TOO LOW FOR THE CHOPPY WIND WAVE POTENTIAL.
CONDITIONS WILL IMPROVE QUICKLY ON SUNDAY WITH TRANQUIL CONDITIONS
THROUGH MONDAY NIGHT. INCREASING SOUTHWEST FLOW AHEAD OF THE NEXT
FRONT MAY PUSH WINDS AS HIGH AS 15-20 KT WITH SEAS REACHING 5 FT
OVER THE OUTER PORTIONS. A STRONGER SURGE WILL OCCUR LATE NEXT WEEK
WHEN COLD HIGH PRESSURE BUILDS OVER THE WATERS.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY FROM 11 AM THIS MORNING TO 1 AM EST SUNDAY
FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 9 AM EST SUNDAY
FOR AMZ350-352-354.
SMALL CRAFT ADVISORY UNTIL 11 AM EST SUNDAY FOR AMZ374.
&&
$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...JRL
LONG TERM...JRL
AVIATION...
MARINE...JRL
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
313 AM CST SAT DEC 29 2012
.DISCUSSION...
918 PM CST
FOR EVENING UPDATE...
HAVE MADE ONLY MINOR NEAR-TERM TWEAKS TO EARLIER UPDATE FOR TRENDS
WITH FLURRIES/PATCHY FREEZING DRIZZLE WHICH CONTINUE TO AFFECT
PORTIONS OF NORTHERN IL AT MID-EVENING. HAVE ALSO BEEFED UP POPS
ALONG THE IL/IN LAKE MICHIGAN SHORE AREAS SATURDAY...WITH POTENTIAL
FOR LAKE-EFFECT SNOW SHOWERS.
LOW PRESSURE WAS OVER THE LOWER MISSISSIPPI VALLEY THIS EVENING...
WITH A WEAK INVERTED SURFACE TROUGH EXTENDING NORTH THROUGH IL/WI.
THIS TROUGH IS ASSOCIATED WITH RATHER COMPLEX MID/UPPER LEVEL TROUGH
ACROSS THE MIDWEST...WHICH WILL CONTINUE TO MOVE EAST ACROSS THE
REGION OVERNIGHT. 00Z RAOBS FROM DVN/ILX INDICATE THE NATURE OF OUR
FLURRY/FREEZING DRIZZLE ISSUE THIS EVENING...WITH SATURATED LOW
LEVELS UP TO ABOUT 800 MB...WITH COLDEST TEMPS ONLY ABOUT -8 C TO
-10 C WITHIN THAT MOIST LAYER. THIS WAS RESULTING IN MORE
SUPERCOOLED DROPLETS THAN ICE CRYSTALS...AND DRIZZLE/FREEZING
DRIZZLE AT THE SURFACE WITH OCCASIONAL FINE SNOW GRAINS/FLURRIES. AS
MENTIONED IN EARLIER UPDATE...MAIN UPPER TROUGH AXIS AND STRONGER
VORT OVER IA IS EXPECTED TO PROPAGATE EASTWARD ACROSS NORTHERN IL
AFTER MIDNIGHT...WITH GREATER POTENTIAL TO INTRODUCE ICE CRYSTALS
AND THUS A GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN
THE DRIZZLE EXPERIENCED THIS EVENING. HOWEVER...GUIDANCE IS
CONSISTENT IN WEAKENING THIS WAVE AS IT MOVES EAST AND DRYING UP
MODEL GENERATED QPF AS IT REACHES OUR CWA. THUS HAVE CUT BACK POPS A
BIT AND MENTIONED LIGHT SNOW/FLURRIES WITH NO REAL ACCUMULATION FOR
THE OVERNIGHT ACROSS THE AREA.
ON SATURDAY...INVERTED TROUGH/CONVERGENCE AXIS ENDS UP LINGERING
ALONG THE WESTERN SHORE OF LAKE MICHIGAN AS LOW LEVEL WINDS BACK TO
THE NORTH-NORTHWEST THROUGH AFTERNOON. LAKE-INDUCED THERMODYNAMIC
PROFILES IMPROVE THROUGH LATE SATURDAY...WITH SFC-850 DELTA T
INCREASING TO ABOUT 17 C...AND EQUILIBRIUM LEVELS INCREASING TO
NEARLY 10 KFT LATER IN THE DAY/EVENING. THIS SUPPORTS SCENARIO OF
LAKE EFFECT SNOW SHOWER DEVELOPMENT ALONG THE IL SHORE AND INTO
NORTHWEST INDIANA SATURDAY MORNING/AFTERNOON...WITH THE BAND
EVENTUALLY MOVING EAST OF THE IL SHORE AND AFFECTING MAINLY PORTER
COUNTY SATURDAY EVENING. WHILE DAYTIME TEMPS IN THE LOW/MID 30S
ESPECIALLY DOWNWIND OF THE LAKE ARE A LIMITING FACTOR...THE
POTENTIAL FOR SOME MINOR ACCUMULATION APPEARS TO EXIST ALONG THE IL
SHORE...WITH PERHAPS 2-4 INCHES POSSIBLE OVER NORTHERN/NORTHEASTERN
PORTER COUNTY WHERE THE BAND MAY BE MORE FOCUSED LATE IN THE
DAY/EARLY EVENING HOURS. THUS HAVE BUMPED POPS TO LIKELY IN THESE
AREAS AND INCREASED QPF/SNOW AMOUNTS A BIT. WINDS CONTINUE TO BACK
MORE NORTHWEST-WEST AFTER ABOUT 03Z...WHICH SHOULD SHIFT THE FOCUS
FOR LES EAST OF PORTER COUNTY BY LATE SATURDAY EVENING.
RATZER
//PREV DISCUSSION...
644 PM CST
FOR EARLY EVENING UPDATE...
HAVE ADDED A MENTION OF PATCHY FREEZING DRIZZLE TO FORECAST EARLY
THIS EVENING BASED ON CURRENT OBS/REPORT OF DZ/FZDZ ACROSS PARTS OF
NORTHERN IL.
AREA OF VERY LIGHT REFLECTIVITY...<10 DBZ...OVER NORTHERN IL PER
KLOT 88D DATA WAS PRODUCING LIGHT FREEZING DRIZZLE/FLURRIES PER
REGIONAL AWOS REPORTS AS OF 00Z. THIS APPEARS VERY REASONABLE
BASED ON FORECAST SOUNDINGS FROM 18Z NAM/23Z RAP WHICH DEPICT
SATURATED LOW LEVELS UP TO ABOUT 5000-6000 FT OR ABOUT 800
MB...WITH TEMPS ONLY -9/-10C. THIS SUGGESTS WHILE THERE MAY BE ICE
CRYSTALS PRESENT...SUPERCOOLED LIQUID DROPLETS ARE MORE PREVALENT
WHICH IS SUPPORTED BY THE SURFACE REPORTS OF FREEZING DRIZZLE. HAD
A REPORT FROM THE SOUTHEAST CORNER OF LASALLE COUNTY AROUND 6 PM
INDICATING FOG/DRIZZLE AT 30 DEGREES WITH SOME LIGHT ICING ON
OBJECTS. TEMPS GENERALLY RUNNING 30-32 F ACROSS THE AREA SO CANT
RULE OUT SOME TRACE AMOUNTS OF ICE THOUGH WOULD EXPECT MOST WELL-
TRAVELED AND TREATED ROADS WILL BE OK. SIDEWALKS...PARKING
LOTS...WINDSHIELDS OF PARKED CARS MAY SEE A LITTLE LIGHT GLAZING.
HERE AT THE WFO...VERY LIGHT DRIZZLE MORE LIKE A MIST OCCURRING
WITH NO REAL ACCUMULATION OR ICING. BASED ON THIS HAVE ISSUED AN
SPS HIGHLIGHTING THIS...BUT AT THIS TIME HAVE REFRAINED FROM A
WINTER WX ADVISORY.
STRONGER MID-LEVEL WAVE OVER CENTRAL/SOUTHWEST IA IS EXPECTED TO
APPROACH THE AREA LATER THIS EVENING/OVERNIGHT WITH A LITTLE MORE
MID-LEVEL MOISTURE WHICH SHOULD FAVOR MORE NUMEROUS ICE NUCLEI AND A
GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN FREEZING
DRIZZLE.
WITH MOIST LOW LEVELS AND LIGHT WINDS...AREAS OF FOG ALSO NOTED WITH
VISIBILITY GENERALLY 1-3 MILES. SAME REPORT FROM LASALLE COUNTY
INDICATED VIS AS LOW AS 1/2 MILE...THOUGH WITH CLOUD COVER AM NOT
EXPECTING WIDESPREAD VIS UNDER 1 MILE.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* AREAS OF LGT SN WILL PERSIST.
* LOW CIGS/VSBYS WILL LINGER...WITH CIGS LOWERING TO IFR. WEST OF
ORD/MDW PATCHY LIFR IS POSSIBLE THRU DAYBREAK. SOME BRIEF
IMPROVEMENT WILL OCCUR...HOWEVER FOR A SMALL WINDOW OF TIME.
* WINDS HAVE SHIFTED TO 300-320 DEG AND SPEEDS HAVE INCREASED TO
ARND 6 TO 8 KT. WINDS WILL INCREASE TO ARND 10 KT LATER THIS
MORNING.
BEACHLER
//DISCUSSION...UPDATED 09Z...
SOME BETTER MIXING WAS NOTED ACROSS FAR NORTHEAST IL...MAINLY IN
THE UGN/ORD/MDW/GYY AREAS. THIS HAS RESULTED IN CIGS PUSHING TO
VFR AT TIMES. FEEL THAT THIS WILL REMAIN SHORT LIVED FOR A PERIOD
OF TIME EARLY THIS MORNING...HOWEVER CIGS JUST TO THE WEST OF THIS
AREA REMAIN LOW OR ARND 500-900FT AGL. HAVE OPTED TO INCLUDE THIS
MENTION OF IMPROVED CIGS AS A TEMPO GROUP AS THE DOMINATE CIG WILL
BE THE LOWER CONDS.
WITH THE BETTER MIXING PRECIP HAS CHANGED OVER TO LGT SN ACROSS
THE AIRFIELDS THIS MORNING. VSBYS REMAIN REDUCED FROM THE VERY
MOIST ATMOSPHERE...HOWEVER NOT AS LOW AS PREVIOUSLY ANTICIPATED.
HAVE BUMPED VSBYS UP SLIGHTLY AS WELL AS CIGS TO REFLECT THIS
TREND.
PREV DISCUSSION UPDATED 06Z...
VERY MOIST LOW LEVELS WILL REMAIN ACROSS NORTHERN IL/NORTHWEST IN
AIRFIELDS. THIS NORMALLY IS NOT A PROBLEM...HOWEVER WITH THE LACK
OF LIFT OR MIXING...THIS HAS RESULTED IN VERY LOW CIGS ARND
1200-1400FT AGL TO IN SOME LOCATIONS ARND 1000FT AGL. IN ADDITION
WITH A VERY MOIST NEAR SFC ENVIRONMENT AND TEMPS ARND FREEZING TO
JUST BELOW...THE DZ THAT HAS BEEN FALLING WAS BECOMING FZDZ.
GUIDANCE CONTINUES TO INDICATE THAT SOME LIFT WILL BEGIN TO OCCUR
SHORTLY AND SHOULD BE ENOUGH TO CHANGE ANY FZDZ OVER TO LGT SNOW.
IN ADDITION TO THE REDUCED CIGS...VSBYS WILL ALSO BE REDUCED TO
ARND 2-3SM. FURTHER WEST AWAY FROM THE SLIGHTLY WARMER ORD/MDW
AIRFIELDS...VSBYS COULD DIP TO ARND 1SM OVERNIGHT.
AS THE WEAK SYSTEM CONTINUES TO DRIFT EAST...WINDS WILL BEGIN TO
SHIFT W/NW. THIS WILL AID IN SLIGHTLY DRIER AIR FILTERING INTO THE
REGION FROM THE NW. IT DOES NOT APPEAR THAT THIS DRY AIR WILL BE
ENOUGH TO ERODE THE STRATUS LAYER INITIALLY...OVER TIME CIGS/VSBYS
WILL IMPROVE. GUIDANCE CONTINUES TO INDICATE THAT AFT 15Z CIGS
WILL FINALLY PUSH BACK TO LOW END MVFR. HAVE BACKED OFF ONLY A
COUPLE HOURS FROM EARLIER THINKING WITH RESPECT TO VFR CONDS
RETURNING. FEEL TAHT THIS MAY NOT OCCUR UNTIL AFT 00Z SUN.
MEANWHILE THE OTHER ATTENTION IS TO THE POTENTIAL FOR A LAKE
EFFECT SNOW BAND TO DEVELOP. GUIDANCE AND CURRENT THINKING IS THAT
WITH THE EXPECTED WIND FORECAST FROM THE W/NW...THAT ANY LAKE
EFFECT SNOW WOULD BE CONFINED TO GYY OR AIRFIELDS TO THE EAST OF
THIS. THE CONFIDENCE IN ANY IMPACT ON GYY HAS LOWERED SLIGHTLY
FROM EARLIER THINKING...HOWEVER THIS COULD COME BACK INTO PLAY IF
THE WINDS TURN MORE NORTHERLY. IN WHICH CASE GYY COULD BE IMPACTED
SIGNIFICANTLY WITH LGT TO MOD SNOW AND VSBYS DOWN ARND 1SM OR AT
TIMES LOWER.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* MEDIUM CONFIDENCE IN CIGS LOWERING TO IFR CONDS.
* MEDIUM CONFIDENCE IN VSBYS FORECAST.
* HIGH CONFIDENCE IN WIND DIR/SPEED FORECAST.
* MEDIUM/HIGH CONFIDENCE IN PRECIP REMAINING AS LGT SN.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
* SUNDAY...DRY/VFR.
* MONDAY...DRY. MVFR POSSIBLE.
* TUESDAY AND WEDNESDAY...DRY/VFR.
* WEDNESDAY NIGHT AND THURSDAY...SLIGHT CHANCE OF SNOW SHOWERS/MVFR.
ED F
&&
.MARINE...
300 AM CST
RATHER QUIET PERIOD FOR LAKE MICHIGAN WILL CONTINUE...OUTSIDE OF
THE POTENTIAL FOR SMALL CRAFT CONDS ALONG THE NORTHWEST INDIANA
NEARSHORE WATERS. OTHERWISE WINDS WILL REMAIN SUB-GALE CRITERIA
FOR THE OPEN WATERS.
A TROUGH OF LOW PRESSURE CONTINUES TO LIFT OFF TO THE NORTHEAST...AS
A BROAD RIDGE OF HIGH PRESSURE OVER THE CENTRAL PLAINS STRETCHES
TO THE WESTERN GULF OF MEXICO. THIS HIGH PRESSURE WILL DRIFT EAST
AND BECOME CENTERED ACROSS THE TENNESSEE VALLEY SUNDAY. THIS WILL
PROVIDE AN INFLUENCE ON THE WEATHER OVER LAKE MICHIGAN WITH A
GRADIENT SETTING THE STAGE FOR WINDS TO INCREASE TO 15 TO 25 KT
FROM THE NW/W. A FEW GUSTS TO 30 KT LATE TONIGHT MAY OCCUR...HOWEVER
NOT EXPECTING A WIDESPREAD SITUATION. AS A RESULT OF THE INCREASED
WINDS AND FETCH...WAVES WILL BUILD TO SMALL CRAFT CONDS OR 4 TO 7
FT ALONG THE INDIANA NEARSHORE WATERS THIS AFTERNOON THROUGH
SUNDAY MORNING.
THEN WINDS SLOWLY SHIFT TO THE SW MIDDAY SUN AND SHOULD AID IN
LOWERING WAVES TO ARND 3 TO 5 FT. THEN THE SOUTHWEST FLOW WILL
CONTINUE THROUGH MON AS YET ANOTHER LOW PRESSURE SYSTEM IS
EXPECTED TO LIFT NORTHEAST ACROSS THE UPPER MIDWEST TO NORTH OF
LAKE SUPERIOR MON. A TRAILING FRONTAL BOUNDARY WILL REACH LAKE
MICHIGAN LATER MON. THEN ANOTHER TIGHT PRESSURE GRADIENT DEVELOPS
TUE...HOWEVER GUIDANCE DOES NOT INDICATE THAT WINDS WOULD GUSTS
ABOVE 30 KT.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ744-LMZ745...3 PM SATURDAY TO 9 AM
SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1202 AM CST SAT DEC 29 2012
.DISCUSSION...
918 PM CST
FOR EVENING UPDATE...
HAVE MADE ONLY MINOR NEAR-TERM TWEAKS TO EARLIER UPDATE FOR TRENDS
WITH FLURRIES/PATCHY FREEZING DRIZZLE WHICH CONTINUE TO AFFECT
PORTIONS OF NORTHERN IL AT MID-EVENING. HAVE ALSO BEEFED UP POPS
ALONG THE IL/IN LAKE MICHIGAN SHORE AREAS SATURDAY...WITH POTENTIAL
FOR LAKE-EFFECT SNOW SHOWERS.
LOW PRESSURE WAS OVER THE LOWER MISSISSIPPI VALLEY THIS EVENING...
WITH A WEAK INVERTED SURFACE TROUGH EXTENDING NORTH THROUGH IL/WI.
THIS TROUGH IS ASSOCIATED WITH RATHER COMPLEX MID/UPPER LEVEL TROUGH
ACROSS THE MIDWEST...WHICH WILL CONTINUE TO MOVE EAST ACROSS THE
REGION OVERNIGHT. 00Z RAOBS FROM DVN/ILX INDICATE THE NATURE OF OUR
FLURRY/FREEZING DRIZZLE ISSUE THIS EVENING...WITH SATURATED LOW
LEVELS UP TO ABOUT 800 MB...WITH COLDEST TEMPS ONLY ABOUT -8 C TO
-10 C WITHIN THAT MOIST LAYER. THIS WAS RESULTING IN MORE
SUPERCOOLED DROPLETS THAN ICE CRYSTALS...AND DRIZZLE/FREEZING
DRIZZLE AT THE SURFACE WITH OCCASIONAL FINE SNOW GRAINS/FLURRIES. AS
MENTIONED IN EARLIER UPDATE...MAIN UPPER TROUGH AXIS AND STRONGER
VORT OVER IA IS EXPECTED TO PROPAGATE EASTWARD ACROSS NORTHERN IL
AFTER MIDNIGHT...WITH GREATER POTENTIAL TO INTRODUCE ICE CRYSTALS
AND THUS A GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN
THE DRIZZLE EXPERIENCED THIS EVENING. HOWEVER...GUIDANCE IS
CONSISTENT IN WEAKENING THIS WAVE AS IT MOVES EAST AND DRYING UP
MODEL GENERATED QPF AS IT REACHES OUR CWA. THUS HAVE CUT BACK POPS A
BIT AND MENTIONED LIGHT SNOW/FLURRIES WITH NO REAL ACCUMULATION FOR
THE OVERNIGHT ACROSS THE AREA.
ON SATURDAY...INVERTED TROUGH/CONVERGENCE AXIS ENDS UP LINGERING
ALONG THE WESTERN SHORE OF LAKE MICHIGAN AS LOW LEVEL WINDS BACK TO
THE NORTH-NORTHWEST THROUGH AFTERNOON. LAKE-INDUCED THERMODYNAMIC
PROFILES IMPROVE THROUGH LATE SATURDAY...WITH SFC-850 DELTA T
INCREASING TO ABOUT 17 C...AND EQUILIBRIUM LEVELS INCREASING TO
NEARLY 10 KFT LATER IN THE DAY/EVENING. THIS SUPPORTS SCENARIO OF
LAKE EFFECT SNOW SHOWER DEVELOPMENT ALONG THE IL SHORE AND INTO
NORTHWEST INDIANA SATURDAY MORNING/AFTERNOON...WITH THE BAND
EVENTUALLY MOVING EAST OF THE IL SHORE AND AFFECTING MAINLY PORTER
COUNTY SATURDAY EVENING. WHILE DAYTIME TEMPS IN THE LOW/MID 30S
ESPECIALLY DOWNWIND OF THE LAKE ARE A LIMITING FACTOR...THE
POTENTIAL FOR SOME MINOR ACCUMULATION APPEARS TO EXIST ALONG THE IL
SHORE...WITH PERHAPS 2-4 INCHES POSSIBLE OVER NORTHERN/NORTHEASTERN
PORTER COUNTY WHERE THE BAND MAY BE MORE FOCUSED LATE IN THE
DAY/EARLY EVENING HOURS. THUS HAVE BUMPED POPS TO LIKELY IN THESE
AREAS AND INCREASED QPF/SNOW AMOUNTS A BIT. WINDS CONTINUE TO BACK
MORE NORTHWEST-WEST AFTER ABOUT 03Z...WHICH SHOULD SHIFT THE FOCUS
FOR LES EAST OF PORTER COUNTY BY LATE SATURDAY EVENING.
RATZER
//PREV DISCUSSION...
644 PM CST
FOR EARLY EVENING UPDATE...
HAVE ADDED A MENTION OF PATCHY FREEZING DRIZZLE TO FORECAST EARLY
THIS EVENING BASED ON CURRENT OBS/REPORT OF DZ/FZDZ ACROSS PARTS OF
NORTHERN IL.
AREA OF VERY LIGHT REFLECTIVITY...<10 DBZ...OVER NORTHERN IL PER
KLOT 88D DATA WAS PRODUCING LIGHT FREEZING DRIZZLE/FLURRIES PER
REGIONAL AWOS REPORTS AS OF 00Z. THIS APPEARS VERY REASONABLE
BASED ON FORECAST SOUNDINGS FROM 18Z NAM/23Z RAP WHICH DEPICT
SATURATED LOW LEVELS UP TO ABOUT 5000-6000 FT OR ABOUT 800
MB...WITH TEMPS ONLY -9/-10C. THIS SUGGESTS WHILE THERE MAY BE ICE
CRYSTALS PRESENT...SUPERCOOLED LIQUID DROPLETS ARE MORE PREVALENT
WHICH IS SUPPORTED BY THE SURFACE REPORTS OF FREEZING DRIZZLE. HAD
A REPORT FROM THE SOUTHEAST CORNER OF LASALLE COUNTY AROUND 6 PM
INDICATING FOG/DRIZZLE AT 30 DEGREES WITH SOME LIGHT ICING ON
OBJECTS. TEMPS GENERALLY RUNNING 30-32 F ACROSS THE AREA SO CANT
RULE OUT SOME TRACE AMOUNTS OF ICE THOUGH WOULD EXPECT MOST WELL-
TRAVELED AND TREATED ROADS WILL BE OK. SIDEWALKS...PARKING
LOTS...WINDSHIELDS OF PARKED CARS MAY SEE A LITTLE LIGHT GLAZING.
HERE AT THE WFO...VERY LIGHT DRIZZLE MORE LIKE A MIST OCCURRING
WITH NO REAL ACCUMULATION OR ICING. BASED ON THIS HAVE ISSUED AN
SPS HIGHLIGHTING THIS...BUT AT THIS TIME HAVE REFRAINED FROM A
WINTER WX ADVISORY.
STRONGER MID-LEVEL WAVE OVER CENTRAL/SOUTHWEST IA IS EXPECTED TO
APPROACH THE AREA LATER THIS EVENING/OVERNIGHT WITH A LITTLE MORE
MID-LEVEL MOISTURE WHICH SHOULD FAVOR MORE NUMEROUS ICE NUCLEI AND A
GREATER PROBABILITY OF LIGHT SNOW/FLURRIES RATHER THAN FREEZING
DRIZZLE.
WITH MOIST LOW LEVELS AND LIGHT WINDS...AREAS OF FOG ALSO NOTED WITH
VISIBILITY GENERALLY 1-3 MILES. SAME REPORT FROM LASALLE COUNTY
INDICATED VIS AS LOW AS 1/2 MILE...THOUGH WITH CLOUD COVER AM NOT
EXPECTING WIDESPREAD VIS UNDER 1 MILE.
RATZER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* PATCHY DZ/FZDZ WILL TRANSITION TO LGT SN.
* LOW CIGS/VSBYS WILL LINGER THRU OVERNIGHT...WITH CIGS LOWERING
TO IFR. WEST OF ORD/MDW PATCHY LIFR IS POSSIBLE THRU DAYBREAK.
* WINDS WILL REMAIN LGT FROM THE SW AT 5 KT...BECOMING NW ARND
DAYBREAK AND INCREASING TO ARND 10 KT.
BEACHLER
//DISCUSSION...UPDATED 06Z...
VERY MOIST LOW LEVELS WILL REMAIN ACROSS NORTHERN IL/NORTHWEST IN
AIRFIELDS. THIS NORMALLY IS NOT A PROBLEM...HOWEVER WITH THE LACK
OF LIFT OR MIXING...THIS HAS RESULTED IN VERY LOW CIGS ARND
1200-1400FT AGL TO IN SOME LOCATIONS ARND 1000FT AGL. IN ADDITION
WITH A VERY MOIST NEAR SFC ENVIRONMENT AND TEMPS ARND FREEZING TO
JUST BELOW...THE DZ THAT HAS BEEN FALLING WAS BECOMING FZDZ.
GUIDANCE CONTINUES TO INDICATE THAT SOME LIFT WILL BEGIN TO OCCUR
SHORTLY AND SHOULD BE ENOUGH TO CHANGE ANY FZDZ OVER TO LGT SNOW.
IN ADDITION TO THE REDUCED CIGS...VSBYS WILL ALSO BE REDUCED TO
ARND 2-3SM. FURTHER WEST AWAY FROM THE SLIGHTLY WARMER ORD/MDW
AIRFIELDS...VSBYS COULD DIP TO ARND 1SM OVERNIGHT.
AS THE WEAK SYSTEM CONTINUES TO DRIFT EAST...WINDS WILL BEGIN TO
SHIFT W/NW. THIS WILL AID IN SLIGHTLY DRIER AIR FILTERING INTO THE
REGION FROM THE NW. IT DOES NOT APPEAR THAT THIS DRY AIR WILL BE
ENOUGH TO ERODE THE STRATUS LAYER INITIALLY...OVER TIME CIGS/VSBYS
WILL IMPROVE. GUIDANCE CONTINUES TO INDICATE THAT AFT 15Z CIGS
WILL FINALLY PUSH BACK TO LOW END MVFR. HAVE BACKED OFF ONLY A
COUPLE HOURS FROM EARLIER THINKING WITH RESPECT TO VFR CONDS
RETURNING. FEEL TAHT THIS MAY NOT OCCUR UNTIL AFT 00Z SUN.
MEANWHILE THE OTHER ATTENTION IS TO THE POTENTIAL FOR A LAKE
EFFECT SNOW BAND TO DEVELOP. GUIDANCE AND CURRENT THINKING IS THAT
WITH THE EXPECTED WIND FORECAST FROM THE W/NW...THAT ANY LAKE
EFFECT SNOW WOULD BE CONFINED TO GYY OR AIRFIELDS TO THE EAST OF
THIS. THE CONFIDENCE IN ANY IMPACT ON GYY HAS LOWERED SLIGHTLY
FROM EARLIER THINKING...HOWEVER THIS COULD COME BACK INTO PLAY IF
THE WINDS TURN MORE NORTHERLY. IN WHICH CASE GYY COULD BE IMPACTED
SIGNIFICANTLY WITH LGT TO MOD SNOW AND VSBYS DOWN ARND 1SM OR AT
TIMES LOWER.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN CIGS LOWERING TO IFR CONDS.
* MEDIUM CONFIDENCE IN VSBYS FORECAST.
* HIGH CONFIDENCE IN WIND DIR/SPEED FORECAST.
* MEDIUM/HIGH CONFIDENCE IN PRECIP REMAINING AS LGT SN.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 12Z SUNDAY-12Z FRIDAY...UPDATED 00Z...
* SUNDAY...DRY/VFR.
* MONDAY...DRY. MVFR POSSIBLE.
* TUESDAY AND WEDNESDAY...DRY/VFR.
* WEDNESDAY NIGHT AND THURSDAY...SLIGHT CHANCE OF SNOW SHOWERS/MVFR.
ED F
&&
.MARINE...
200 PM CST
RELATIVELY LIGHTER WINDS IN PLACE ACROSS THE LAKE EARLY THIS
AFTERNOON AS A FAIRLY WEAK SURFACE PATTERN IS IN PLACE. THE
EXCEPTION IS FOR AREAS NEAR THE MIDDLE PORTIONS OF THE LAKE WHERE
A TIGHTER PRESSURE GRADIENT RESIDES...AND WHERE 10 TO 20 KT WINDS
ARE BEING OBSERVED. WIND DIRECTION REMAINS VARIABLE WITH NORTHERLY
WINDS BEING REPORTED ACROSS THE NORTHERN HALF OF THE LAKE AND
SOUTHERLY WINDS OVER THE SOUTHERN HALF OF THE LAKE. WINDS WILL BE
TURNING TO MORE OF A NORTHERLY DIRECTION TONIGHT AS A WEAK SURFACE
TROUGH SHIFTS EAST ACROSS THE REGION. EXPECT NORTH TO NORTHWEST
WINDS ON SATURDAY WITH AN INCREASE IN SPEEDS...WITH WINDS THEN
TURNING MORE WESTERLY AND DIMINISHING SOME AS HIGH PRESSURE TO THE
WEST SHIFTS EAST THROUGH THE CENTRAL GREAT LAKES SATURDAY NIGHT.
SOUTHWESTERLY WINDS WILL THEN PICK UP SUNDAY THROUGH SUNDAY NIGHT
AS THE NEXT SYSTEM APPROACHES FROM THE WEST.
RODRIGUEZ
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
433 AM EST SAT DEC 29 2012
.SHORT TERM...
TODAY THROUGH SUNDAY NIGHT...KEPT THE WINTER WEATHER ADVISORY FOR
FAR SOUTHEAST AREAS GOING UNTIL 7 AM GIVEN THE LATEST SATELLITE AND
RADAR TRENDS. SURFACE OBS AND SURFACE REPORTS OF SNOWFALL
APPROACHING 4 INCHES IN VAN WERT COUNTY SUPPORT TOTAL SNOWFALL
AMOUNTS UP TO 5 INCHES. THE LATEST HRRR SUGGESTS THE SNOW MAY
LINGER A LITTLE LONGER THAN 7 AM THIS MORNING...BUT FOR NOW WILL
KEEP THE EXPIRATION TIME AT 7 AM AND EXTEND LATER IF NEEDED. BACK TO
THE NORTHWEST...LAKE EFFECT SNOW SHOWERS WERE JUST BEGINNING TO
DEVELOP OVER SOUTHERN LAKE MICHIGAN AND SHOULD CONTINUE TO EXPAND IN
COVERAGE. LAKE PARAMETERS NOT IMPRESSIVE...BUT SHOULD SUPPORT LAKE
EFFECT SNOW WITH LIGHT SNOW ACCUMULATIONS. MADE SOME ADJUSTMENTS
ACCORDING TO THE LATEST HIGH RES MODEL DATA TO LAKE EFFECT
TRAJECTORIES AND COVERAGE TODAY AND TONIGHT. OTHERWISE...AS FOR
TEMPERATURES...WENT WITH THE WARMER MET FOR LOWS TONIGHT AND HIGHS
SUNDAY.
&&
.LONG TERM...
PROGRESSIVE SPLIT FLW PATTN CONTS UNABATED YET REMAINS POTENTIALLY
PROBLEMATIC AS EVIDENT W/CURRENT SYS OVR THE TN VALLEY THIS MORNING.
GIVEN WORRISOME TREND TWD NEWD PLACEMENT OF DEEPER SRN STREAM WV AND
NWD POSITIONING OF DOWNSTREAM MID LVL CONFLUENCE ZONE SEEN IN ECMWF
AND IN TANDEM W/00Z NAM/UKMET WILL CAUTIOUSLY BREAK FM PRIOR
CONTINUITY WRT POPS MON-MON NIGHT W/CONSENSUS INDICATIONS OF AT
LEAST PARTIAL STREAM PHASING POSSIBLE.
HWVR GRADUAL BLDG OF NEG HGT ANOMALIES CNTRD OVR SE CANADA UPSTREAM
OF BLDG DOWNSTREAM BLOCK OVR GREENLAND AGAIN POINT TO INCREASING
POLAR WEDGING DVLPG MID-LATE PD. IN FACT MULTIDAY MEANS OF GFS MOS
GUIDANCE CONT W/A DOWNWARD TREND ESP THU-FRI PD IN WAKE OF POLAR
FNTL PASSAGE. SOME LK RESPONSE XPCD GIVEN DEGREE/DEPTH OF CAA WING
WED NIGHT AND THU. HWVR SWD CONSENSUS PLACEMENT OF SFC RIDGE CNTR
ACRS THE CNTRL PLAINS WOULD SUGGEST LIMITED RESPONSE IN FACE OF
GENERAL WRLY LL FETCH AND EXTREMELY DRY BNDRY LYR FEED OUT OF RIDGE.
THUS WILL KEEP W/TEMPERED POPS FOR THE TIME BEING. REGARDLESS GIVEN
CORRESPONDING AGREEMENT BTWN GFS/ECMWF WILL UNDERCUT THU/FRI TEMPS
FURTHER IN LIGHT OF BLDG LL THERMAL TROUGH ACRS THE NERN US.
&&
.AVIATION...
AN IMPRESSIVE BAND OF SNOW CONTINUES FROM SOUTHERN INDIANA INTO
NORTHEAST INDIANA...EXTENDING INTO THE FWA TERMINAL SITE. THE
HEAVIER SNOW SHOULD STAY SE OF FWA...GIVEN CURRENT TRENDS AND
OBS...WENT WITH A 4 HOUR TEMPO GROUP DOWN TO 3/4 MILE. CURRENT
THINKING IS SNOW SHOULD END BY 15Z...WITH WINDS BECOMING WEST.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...WINTER WEATHER ADVISORY UNTIL 7 AM EST THIS MORNING FOR INZ026-
027-032>034.
MI...NONE.
OH...WINTER WEATHER ADVISORY UNTIL 7 AM EST THIS MORNING FOR OHZ016-
024-025.
LM...NONE.
&&
$$
SHORT TERM...SKIPPER
LONG TERM...T
AVIATION...SKIPPER
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
300 AM CST SAT DEC 29 2012
.SYNOPSIS...
06Z SFC ANALYSIS HAS SEVERAL LOWS IN THE OHIO AND TENNESSEE VALLEYS.
INVERTED TROFS RAN FROM A LOW NEAR KSDF INTO LAKE MICHIGAN AND OHIO.
DEW POINTS WERE IN THE 20S AND 30S OVER THE GREAT LAKES AND
SOUTHEAST WITH SINGLE DIGITS AND TEENS IN THE PLAINS.
&&
.SHORT TERM...TODAY AND TONIGHT...
CLEARING TRENDS AND PRECIPITATION POTENTIAL ARE THE IMMEDIATE CONCERNS.
SATELLITE CONTINUES TO SHOW PLENTY OF ST TRAPPED BELOW THE INVERSION.
WHAT APPEARS TO REPRESENT THE BACK EDGE OF THE CLOUDS REASONABLY WELL IS
THE 0.5KM AGL CONDENSATION PRESSURE DEFICITS FROM THE RAP MODEL WITH
SOME LOOSE AGREEMENT WITH THE WRF/GFS AT THE SAME LEVEL. ASSUMING THAT
THIS IS CORRECT...CLOUDS WILL CONTINUE ACROSS THE AREA THROUGH THE
MORNING FOLLOWED BY FAIRLY SIGNIFICANT CLEARING DURING THE AFTERNOON
HOURS AS STRONGER SUBSIDENCE DEVELOPS BEHIND A DEPARTING SHORTWAVE. THE
FAR EASTERN PARTS OF THE CWFA MAY NOT CLEAR UNTIL SHORTLY AFTER SUNSET.
RAP MODEL TRENDS ALSO SHOW NEUTRAL TO WEAK F VECTOR CONVERGENCE ACROSS
MOST THE THE CWFA DURING THE MORNING HOURS WITH LOW CONDENSATION
PRESSURE DEFICITS. THUS SCATTERED FLURRIES SHOULD CONTINUE ACROSS MOST
OF THE CWFA DURING THE MORNING WITH FLURRIES ENDING OVER THE EASTERN
HALF OF THE CWFA DURING THE AFTERNOON.
BASED ON CURRENT TEMPERATURES ACROSS THE AREA...CAA SHOULD ALLOW A
DROP OF ABOUT 1-2 DEGREES PRIOR TO SUNRISE ACROSS THE AREA. CAA
CONTINUES THROUGH THE DAY SO TEMPERATURES WILL REMAIN EITHER STEADY
OR ONLY RISE A FEW DEGREES DURING THE DAY.
TONIGHT...CLEAR OR NEARLY CLEAR SKIES SHOULD BE SEEN ACROSS THE AREA.
THE SNOW FIELD COMBINED WITH LIGHT WINDS ARE EXPECTED TO CREATE A WIDE
RANGE IN TEMPERATURES. SINGLE DIGITS SHOULD BE SEEN ACROSS A MAJORITY OF
THE CWFA. IT IS CONCEIVABLE THAT SUB ZERO READINGS MAY BE SEEN OVER THE
RELATIVELY DEEPER SNOW PACK ACROSS THE NORTHWEST PART OF THE CWFA.
08
.LONG TERM...SUNDAY THROUGH NEXT FRIDAY...
MOSTLY DRY TO DRY CONDITIONS WITH WELL BELOW NORMAL TEMPERATURES.
OVERVIEW...INITIALIZATION GOOD WITH LITTLE SENSIBLE WEATHER ISSUES
BESIDES NORMAL WINTER COLD AIR BL MOISTURE ISSUES OVER SNOW PACK.
RUN TO RUN CONTINUITY SUPPORTS A 70/30 BLEND OF GFS/HI-RES ECMWF WITH
NAM TOO FAR NORTH ON MONDAY SYSTEM. PERSISTENCE SUPPORTS WHEN SKIES
ARE FAIR FOR SLIGHTLY LARGER DIURNAL RANGES THAN GUIDANCE.
SUNDAY...LITTLE CHANGE WITH INCREASING HIGH CLOUDS LATE AND OVERNIGHT
WITH MID 20S NORTH TO LOWER TO MIDDLE 30S SOUTHWEST. SUNDAY NIGHT...
SW WINDS OF 5 TO 15 MPH AND MID/HIGH CLOUDS SUPPORT NEARLY STEADY
TEMPERATURES CENTRAL AND SOUTHEAST SECTIONS WITH FALLING TEMPS FAR
NW AS NEXT ARCTIC FRONT ARRIVES.
MONDAY...KEPT LOW POPS SOUTHEAST SECTIONS AS ARCTIC FRONT WITH NW
UPPER FLOW TO CUT OFF MOISTURE TRANSPORT OVER NW SECTIONS.
TEMPERATURES NEARLY STEADY BEHIND FRONT AND FALLING LATE PM IN SE
SECTIONS. LATEST ANALYSIS AND TOOLS SUGGEST ANY SNOW AMOUNTS IN SOUTH
TO BE LESS THAN IN INCH. MONDAY NIGHT...SKIES TO CLEAR WITH
TEMPERATURES CRASHING TO COLDEST READINGS YET THIS WINTER WITH BELOW
ZERO READINGS NW TO LOWER TEENS FAR SE SECTIONS.
TUESDAY THROUGH FRIDAY...COLD NORTHERLY UPPER LEVEL FLOW WITH NEXT
UPPER TROUGH AND ARCTIC FRONT TO ARRIVE LATE WEDNESDAY. THIS SYSTEM
IS TAILORED FOR LATER SHIFTS TO ADD FLURRIES DUE TO VERY COLD AIR
ALOFT AND CYCLONIC CONVERGENT TURNING. MINS FRIDAY AM MAY STILL BE
A CATEGORY OR TWO TOO MILD WITH HI/S STRUGGLING TO MAKE DOUBLE DIGITS
NW SECTIONS THURSDAY AND FRIDAY...15-20 DEGREES BELOW NORMAL.
NICHOLS
&&
.AVIATION...
CONDITIONS ARE RANGING FROM VFR TO MVFR WITH FLURRIES. LOCALIZED IFR
CIGS ARE POSSIBLE. MVFR CONDITIONS WITH BORDERLINE IFR CIGS WILL BE
SEEN THROUGH 18Z/29 WITH SCATTERED FLURRIES. SUBSIDENCE DEVELOPING
AFT 18Z/29 IS EXPECTED TO BREAK UP THE 1-2KFT AGL CIGS. VFR
CONDITIONS ARE EXPECTED AFT 00Z/30.
08
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
08/NICHOLS
AREA FORECAST DISCUSSION
NWS GREAT FALLS MT
1025 PM MST Fri Dec 28 2012
Updated Aviation
.DISCUSSION...
Update forthcoming. Have made a few adjustments to the pop and
weather grids this evening. Weak instability associated with a
passing shortwave has resulted in a little light snow in the West
Yellowstone area. This was depicted well on the 18z GFS run and also
with the HRRR analysis. The GFS decreases precipitation chances
after midnight as upper ridging develops over the area. Southwest
winds will continue overnight and keep temperatures generally above
zero. Emanuel
&&
.AVIATION...
Updated 0600Z.
VFR conditions will prevail at all TAF sites through Saturday
afternoon. Some mid- and upper-level clouds will move over the area
tonight and thicken during the day on Saturday ahead of the next
disturbance. Winds will remain light around 10 to 15 kts tonight
along the Rocky Mountain Front and then increase again by midday
Saturday. As the next disturbance moves into the forecast area by
Saturday afternoon for areas along the Continental Divide and
southwest Montana including KBZN and KHLN, light snow and MVFR
conditions may develop though any snow amounts will be light. Light
snow may spread into the plains later Saturday evening and Saturday
night and have added VCSH to all TAFs though confidence is low. Some
mountain obscuration is expected tonight with widespread mountain
obscuration by Saturday afternoon. MLV
&&
.PREV DISCUSSION...ISSUED 255 PM MST Fri Dec 28 2012
Tonight through Sunday...Current radar shows quiet conditions
throughout the area and will remain quiet through Saturday
evening. A shortwave will move across the area Saturday night
bringing light snow to most locations. Expect one inch or less in
the valleys and adjacent plains and generally 1 to 3 inches in the
mountains. Impacts with this system are expected to be minimal.
Light snow will taper off during the day on Sunday and will push out
of the area by Sunday evening. Main change to the forecast package
was to raise pops on Sunday...by using a model blend of the NAM and
SREF. Temperatures remain cool...and near seasonal averages on
Saturday...then dropping about 10 degrees on Sunday in the wake of
the shortwave. Mercer
Sunday Night through Thursday...Generally good agreement among
models through period. An upper level ridge of high pressure will
slowly build into Pacific Northwest. Daytime high temperatures will
warm to above normal for much of the forecast area Tuesday and will
remain through Friday. In the far northeast, cold air may remain
trapped in the Milk River Valley so have lowered temperatures a bit
in this area. With higher pressure over the Continental Divide,
breezy downslope winds will be common during the period. This ridge
will be quite dry, too, with downslope winds there will be little or
no chance of snow even over the mountains. Only possible exception
to this will be during the Wednesday time frame. Models diverge a
bit at this time with the GFS dropping shortwave energy and a weak
surface cold front through eastern Montana. Have tweaked pops up a
bit over my far eastern zones but am expecting the remainder of the
forecast area to remain dry. Models keep the ridge in place over the
northern Rockies through the end of the week so have dried out
precipitation for the entire area during this period. Britton/mpj
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 18 34 20 25 / 0 0 70 50
CTB 17 32 7 24 / 0 30 50 0
HLN 11 27 16 24 / 0 0 50 40
BZN 7 23 13 21 / 0 0 70 50
WEY 2 19 8 19 / 10 10 60 40
DLN 7 27 16 23 / 0 10 70 40
HVR 9 28 11 23 / 0 10 60 20
LWT 14 33 16 24 / 0 0 40 60
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
AREA FORECAST DISCUSSION
NWS NEWPORT/MOREHEAD CITY NC
340 AM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE WILL APPROACH FROM THE SOUTHWEST TONIGHT AND MOVE
ALONG THE COAST SATURDAY. STRONG HIGH PRESSURE WILL BUILD IN FROM
THE WEST SUNDAY AND EXTEND OVER THE AREA MONDAY. A COLD FRONT WITH
LIMITED MOISTURE WILL MOVE THROUGH THE AREA TUESDAY THEN STALL TO
THE SOUTH WEDNESDAY AND THURSDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AS OF 1245 AM SAT...MINOR ADJUSTMENTS WITH UPDATE. PATCHY -RA WILL
CONTINUE NEXT COUPLE OF HOURS WITH MORE WDSPRD ACTIVITY DEVELOPING
AFTER 3AM.
PREV DISC...SHORTWAVE RIDGING AND HIGH PRES MOVE EWD TONIGHT AS A
ROBUST SHORTWAVE TROUGH AND SFC LOW REFLECTION PUSH ACROSS THE
SOUTHEAST. CLOUDS WILL CONTINUE TO LOWER THROUGH THE EVENING WITH
ISENTROPIC LIFT INCREASING AFTER MIDNIGHT WITH LITTLE COND PRES
DEFICITS AFTER 09Z. WINDS WILL CONTINUE TO BE LIGHT MOST OF THE
OVERNIGHT BUT INCREASING OUT OF THE S/SE TO AROUND 10-15 MPH LATE
COASTAL SECTIONS AS A WARM FRONT STRENGTHENS ALONG THE IMMEDIATE
COAST. CLOUDS AND EVENTUALLY PCPN WILL KEEP DIURNAL TEMPS RANGE TO
A MINIMUM WITH LOWS AROUND 40 INLAND AND L/M 40S COAST.
&&
.SHORT TERM /TODAY/...
AS OF 330 PM FRIDAY...ISENTROPIC LIFT STRONGEST THROUGH THE
MORNING HOURS SAT AS DEEPENING LOW PRES LIFTS NE ALONG THE FRONTAL
BOUNDARY PROGGED TO BE ALIGNED ALONG THE COAST. GENERALLY
STRATIFORM RAIN INLAND BUT COULD SEE ISOLATED CONVECTION ALONG THE
COAST WHERE WEAK MU CAPE AND HIGHER DEWPOINTS WILL RESIDE. MODEL
QPF AROUND A QUARTER TO HALF INCH WITH UP TO AN INCH NEAR THE
COAST IN WETTER MODEL SOLUTIONS. WINDS CONTINUE LIGHT INLAND
THROUGH THE MORNING HOURS BUT ARE EXPECTED TO INCREASE OUT OF THE
S/SW TO 15-25 MPH MID TO LATE MORNING ALONG THE COAST. ONCE THE
LOW PUSHES OFF THE COAST AROUND MID DAY AND DEEPENS AS IT LIFTS
AWAY FROM THE AREA...WINDS SHIFT TO WLY AND INCREASE TO AROUND
15-20 MPH WITH GUSTS TO 25 MPH INLAND AND 20-30 MPH WITH GUSTS TO
AROUND 35 MPH ALONG THE COAST. MAX TEMPS EXPECTED IN THE L/M50S
INLAND TO U50S TO AROUND 60 COAST.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
AS OF 310 AM SAT...SURFACE RIDGE ACROSS THE MID MISSISSIPPI VALLEY
WILL CONTINUE TO PUSH EAST OVER THE REGION SUN INTO MON. WEAK UPPER
LEVEL RIDGE WILL PASS WELL SOUTH OF THE REGION SUN INTO MON WHICH
WILL SHIFT NW FLOW ALOFT TO ZONAL WESTERLY FLOW BY MON. TEMPS WILL
BE SEVERAL DEGREES BELOW CLIMO SUN AND MON WITH LOW LEVEL THICKNESSES
RANGING 1290-1300 METERS SUN TO AROUND 1320 METERS MON. THESE VALUES
WILL YIELD TEMPS IN THE MID 40S SUN TO LOWER 50S MON...UNDER FULL
INSOLATION BOTH DAY. COLDEST NIGHT OF THE EXTENDED WILL BE SUN
NIGHT WITH LIGHT CAA/NW FLOW WHICH WILL DROP TEMPS INTO THE MID
20S INLAND TO LOW 30S ALONG THE OBX.
SURFACE RIDGE MOVES OFFSHORE MON EVENING/NIGHT AHEAD OF AN APPROACHING
LOW PRESSURE SYSTEM DEVELOPING ACROSS DEEP SOUTH AL/MS. SURFACE
WINDS WILL BECOME SW MON EVENING ALLOWING WEAK WAA TO INITIATE
AHEAD OF THE FRONTAL SYSTEM. LIGHT PRECIP SHOULD BEGIN NEW YEARS
DAY MORNING AND CONTINUE CLOUDY/LIGHT RAIN THROUGH TUES NIGHT WHEN
THE WEAK FRONT BECOMES SHUNTED SOUTH OF EASTERN NC. MINOR ADJUSTMENTS
TO POPS/WX WITH FAIRLY GOOD AGREEMENT BETWEEN LATEST MEDIUM GUIDANCE.
BEST FORCING FOR LARGE SCALE ASCENT WILL REMAIN NORTH OF THE REGION
SO EXPECT LOW QPF...RANGING 0.15-0.25 INCHES TUES/TUES NIGHT. WITH
THE SURFACE BOUNDARY SOUTH OF EASTERN NC ON WED...EXPECT MOSTLY DRY
CONDITIONS WITH N/NE CAA HOLDING TEMPS 50-55 DEGREES.
THE SOUTHERN STREAM REMAINS ACTIVE WITH ANOTHER LOW PRESSURE SYSTEM
PASSING SOUTHEAST OFF THE COAST ON THURS INTO THURS NIGHT. HIGH
PRESSURE ACROSS THE OHIO RIVER VALLEY WILL PUSH SE ACROSS EASTERN NC
FRI INTO THE WEEKEND WITH TEMPS FALLING BACK BELOW CLIMO.
&&
.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
SHORT TERM /THROUGH 06Z SUNDAY/...
AS OF 1230 AM SAT...MVFR CIGS HAVE DEVELOPED AT KPGV AND KISO AND
EXPECTED MVFR KEWN AND KOAJ BY AROUND 09Z WAS RAIN CONTINUES TO
SPREAD IN FROM SW. ALL MOS GDNC SUPPORTS IFR CIGS DEVELOPING AROUND
12Z AS RAIN BECOMES WDSPRD...AND CONTINUING THROUGH MORNING WITH LOW
PRES MOVING ALONG COAST. RAIN WILL END BY EARLY AFTN WITH CONDITIONS
IMPROVING TO VFR BY LATE AFTN AS DRIER AIR MOVES IN BEHIND DEPARTING
LOW...WITH WINDS BECOMING GUSTY FROM WEST.
LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 320 AM SAT...PREDOMINANT VFR CONDITIONS EXPECTED SUN AND MON
AS HIGH PRESSURE TRAVERSES THE REGION. WINDS SHIFT SW LATE MON AS
HIGH PRESSURE SHIFTS OFFSHORE AHEAD OF AN APPROACHING FRONTAL
SYSTEM TUES INTO WED. EXPECT SUB-VFR CONDITIONS MAINLY IN LOWERED
CEILINGS TUES AFTERNOON THROUGH EARLY WED...THEN RETURN TO VFR WED
MIDDAY AS THE FRONT SHIFTS WELL SE OF THE TERMINALS.
&&
.MARINE...
SHORT TERM /THROUGH SATURDAY/...
AS OF 1245 AM SAT...DEVELOPING WARM FRONT BNDRY IS REMAINING A BIT
FARTHER OFFSHORE...RESULTING IN WINDS REMAINING NE OVER CENTRAL AND
SRN WATERS. LATEST NAM12 AND HRRR HAVE BEST HANDLE ON THIS AND
UPDATED FOR OVERNIGHT INTO SAT MORNING WITH BLEND OF THESE MODELS.
INITIAL WEAK SFC WAVE DEVELOPMENT ALONG BNDRY WILL LIKELY KEEP WINDS
NE UNTIL STRONGER LOW MOVES UP DURING MORNING HOURS.
PREV DISC...LOW PRES WILL TRACK ALONG THE SOUTHEAST WITH A WARM
FRONT STRENGTHENING ALONG THE COAST TONIGHT. THE DEEPENING LOW PRES
SYSTEM WILL LIFT NE ACROSS ERN NC SAT MORNING AND OFFSHORE DURING
THE AFTERNOON. S/SELY WINDS WILL INCREASE AFTER MIDNIGHT TONIGHT AND
ARE EXPECTED TO REACH SMALL CRAFT ADVISORY CRITERIA SHORTLY AFTER 8
AM ACROSS THE COASTAL WATERS SOUTH OF OREGON INLET. THE LOW PUSHES
OFF THE COAST AROUND MID DAY WITH WINDS SHIFTING TO WESTERLY AND
INCREASING AS PRES GRADIENTS TIGHTEN AND EXPECT WINDS ACROSS THE
REST OF THE WATERS TO REACH SMALL CRAFT CRITERIA IN THE AFTERNOON.
FOLLOWED WAVEWATCH CLOSELY FOR SEAS WHICH BUILD QUICKLY SAT MORNING
AND APPROACHING THEIR PEAK AROUND 5-8 FT SRN WATERS AND 4-6 FT NRN
WATERS LATE AFTERNOON.
LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 330 AM SAT...SCA CONDITIONS WILL CONTINUE ACROSS ALL COASTAL
WATERS AND SOUNDS SUN AS STRONG PRESSURE GRADIENT WILL PRODUCE NW
WINDS GUSTING TO 30 KTS AND ELEVATED SEAS ACROSS THE COASTAL
WATERS. SURFACE RIDGE BUILDS EAST OVER THE WATERS LATE SUN INTO
MON WHICH WILL REDUCE THE PRESSURE GRADIENT AND ALLOW SCAS TO END
BY MON MORNING. WINDS SHIFT SW MON NIGHT WITH SEAS RANGING 2-4
FT. SW/WSW WINDS INCREASE 15-20 KT MON NIGHT INTO TUES BUT EXPECT
CONDITIONS TO REMAIN BELOW SCA CRITERIA. WEAK COLD FRONT WILL SAG
SOUTHEAST THROUGH THE WATERS TUES NIGHT INTO WED WITH WINDS
SHIFTING NW BY WED MORNING. GRADIENT WILL REMAIN MODERATE AND VOID
OF STRONG CAA...SO EXPECT NW WINDS 10-15 KTS WED AND SEAS 3-5 FT.
GENERALLY USED WAVEWATCH III GUIDANCE FOR THE EXTENDED THROUGH
TUES HOWEVER WWIII WINDS WERE TOO LOW ON WED SO MANUALLY ADJUSTED
FOR THAT TIME PERIOD. OVERALL MINOR TWEAKS TO SEAS FROM PREVIOUS
FORECAST PACKAGE.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 10 PM EST SUNDAY FOR
AMZ135.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 10 PM EST
SUNDAY FOR AMZ130.
SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 6 AM EST MONDAY
FOR AMZ152-154.
SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 6 PM EST SUNDAY
FOR AMZ156-158.
SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 AM EST MONDAY FOR
AMZ150.
&&
$$
SYNOPSIS...SK
NEAR TERM...JBM/SK
SHORT TERM...SK
LONG TERM...DAG
AVIATION...JBM/DAG
MARINE...JBM/SK/DAG
AREA FORECAST DISCUSSION
NWS NEWPORT/MOREHEAD CITY NC
120 AM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE WILL APPROACH FROM THE SOUTHWEST TONIGHT AND MOVE
ALONG THE COAST SATURDAY. STRONG HIGH PRESSURE WILL BUILD IN FROM
THE WEST SUNDAY AND EXTEND OVER THE AREA MONDAY. A COLD FRONT WITH
LIMITED MOISTURE WILL MOVE THROUGH THE AREA TUESDAY THEN STALL TO
THE SOUTH WEDNESDAY AND THURSDAY.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
AS OF 1245 AM SAT...MINOR ADJUSTMENTS WITH UPDATE. PATCHY -RA WILL
CONTINUE NEXT COUPLE OF HOURS WITH MORE WDSPRD ACTIVITY DEVELOPING
AFTER 3AM.
PREV DISC...SHORTWAVE RIDGING AND HIGH PRES MOVE EWD TONIGHT AS A
ROBUST SHORTWAVE TROUGH AND SFC LOW REFLECTION PUSH ACROSS THE
SOUTHEAST. CLOUDS WILL CONTINUE TO LOWER THROUGH THE EVENING WITH
ISENTROPIC LIFT INCREASING AFTER MIDNIGHT WITH LITTLE COND PRES
DEFICITS AFTER 09Z. WINDS WILL CONTINUE TO BE LIGHT MOST OF THE
OVERNIGHT BUT INCREASING OUT OF THE S/SE TO AROUND 10-15 MPH LATE
COASTAL SECTIONS AS A WARM FRONT STRENGTHENS ALONG THE IMMEDIATE
COAST. CLOUDS AND EVENTUALLY PCPN WILL KEEP DIURNAL TEMPS RANGE TO
A MINIMUM WITH LOWS AROUND 40 INLAND AND L/M 40S COAST.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
AS OF 330 PM FRIDAY...ISENTROPIC LIFT STRONGEST THROUGH THE
MORNING HOURS SAT AS DEEPENING LOW PRES LIFTS NE ALONG THE FRONTAL
BOUNDARY PROGGED TO BE ALIGNED ALONG THE COAST. GENERALLY
STRATIFORM RAIN INLAND BUT COULD SEE ISOLATED CONVECTION ALONG THE
COAST WHERE WEAK MU CAPE AND HIGHER DEWPOINTS WILL RESIDE. MODEL
QPF AROUND A QUARTER TO HALF INCH WITH UP TO AN INCH NEAR THE
COAST IN WETTER MODEL SOLUTIONS. WINDS CONTINUE LIGHT INLAND
THROUGH THE MORNING HOURS BUT ARE EXPECTED TO INCREASE OUT OF THE
S/SW TO 15-25 MPH MID TO LATE MORNING ALONG THE COAST. ONCE THE
LOW PUSHES OFF THE COAST AROUND MID DAY AND DEEPENS AS IT LIFTS
AWAY FROM THE AREA...WINDS SHIFT TO WLY AND INCREASE TO AROUND
15-20 MPH WITH GUSTS TO 25 MPH INLAND AND 20-30 MPH WITH GUSTS TO
AROUND 35 MPH ALONG THE COAST. MAX TEMPS EXPECTED IN THE L/M50S
INLAND TO U50S TO AROUND 60 COAST.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
AS OF 245 PM FRIDAY...AT THE BEGINNING OF THE PERIOD...COLD FRONT
WILL BE MOVING OFFSHORE TAKING ANY PRECIPITATION WITH IT SATURDAY
EVENING. UPPER HEIGHTS BUILD AS SURFACE HIGH PRESSURE SETTLES OVER
THE CAROLINAS SUNDAY AND MONDAY. SUNDAY WILL BE CHILLY WITH
MAXIMUM TEMPERATURES MAINLY IN THE MIDDLE AND UPPER 40S WITH LOWS
BY MONDAY MORNING IN THE 20S EXCEPT LOWER TO MIDDLE 30S ALONG THE
IMMEDIATE COAST. SOME SLIGHT MODERATION IN TEMPERATURES ON MONDAY
AS LOW-LEVEL FLOW VEERS BACK TO THE SOUTHWEST AS LOW-LEVEL WARM
AIR ADVECTION PUSHES MAXIMUM TEMPERATURES INTO THE LOWER 50S. BOTH
SUNDAY AND MONDAY SHOULD BE DRY WITH A GOOD AMOUNT OF SUNSHINE.
A SOUTHERN STREAM SYSTEM BRINGS A RETURN OF RAIN TO THE AREA FOR
TUESDAY AFTERNOON THROUGH TUESDAY NIGHT. THE SOUTHERN STREAM
REMAINS ACTIVE WITH ANOTHER SYSTEM ON THURSDAY INTO THURSDAY
NIGHT. MODELS STILL AGREE THAT THIS SYSTEM WILL BE SUPPRESSED TO
THE SOUTH...BUT THERMAL PROFILES KEEP THE COLUMN WELL ABOVE
CRITICAL THICKNESS VALUES...SO EXPECT ONLY RAIN. BOTH THE GFS AND
ECMWF KEEP CONDITIONS DRY BUT RATHER COLD FOR NEXT WEEKEND.
&&
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
SHORT TERM /THROUGH 06Z SUNDAY/...
AS OF 1230 AM SAT...MVFR CIGS HAVE DEVELOPED AT KPGV AND KISO AND
EXPECTED MVFR KEWN AND KOAJ BY AROUND 09Z WAS RAIN CONTINUES TO
SPREAD IN FROM SW. ALL MOS GDNC SUPPORTS IFR CIGS DEVELOPING AROUND
12Z AS RAIN BECOMES WDSPRD...AND CONTINUING THROUGH MORNING WITH LOW
PRES MOVING ALONG COAST. RAIN WILL END BY EARLY AFTN WITH CONDITIONS
IMPROVING TO VFR BY LATE AFTN AS DRIER AIR MOVES IN BEHIND DEPARTING
LOW...WITH WINDS BECOMING GUSTY FROM WEST.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 245 PM FRIDAY...SUB VFR CONDITIONS ARE EXPECTED EARLY
SATURDAY AS LOW PRESSURE MOVES THRU THE AREA WITH WIDESPREAD
PRECIP. CONDITIONS WILL BE IMPROVING AS THE LOW MOVES NE SAT AFTN.
MOSTLY VFR CONDITIONS ARE ANTICIPATED SUNDAY AND MONDAY AS HIGH
PRESSURE INFLUENCES THE WEATHER. PRECIP MAY BREAK OUT AHEAD OF A
FRONTAL SYSTEM LATE TUESDAY WITH SOME SUB VFR CONDITIONS POSSIBLE
ATTM.
&&
.MARINE...
SHORT TERM /THROUGH SATURDAY/...
AS OF 1245 AM SAT...DEVELOPING WARM FRONT BNDRY IS REMAINING A BIT
FARTHER OFFSHORE...RESULTING IN WINDS REMAINING NE OVER CENTRAL AND
SRN WATERS. LATEST NAM12 AND HRRR HAVE BEST HANDLE ON THIS AND
UPDATED FOR OVERNIGHT INTO SAT MORNING WITH BLEND OF THESE MODELS.
INITIAL WEAK SFC WAVE DEVELOPMENT ALONG BNDRY WILL LIKELY KEEP WINDS
NE UNTIL STRONGER LOW MOVES UP DURING MORNING HOURS.
PREV DISC...LOW PRES WILL TRACK ALONG THE SOUTHEAST WITH A WARM
FRONT STRENGTHENING ALONG THE COAST TONIGHT. THE DEEPENING LOW PRES
SYSTEM WILL LIFT NE ACROSS ERN NC SAT MORNING AND OFFSHORE DURING
THE AFTERNOON. S/SELY WINDS WILL INCREASE AFTER MIDNIGHT TONIGHT AND
ARE EXPECTED TO REACH SMALL CRAFT ADVISORY CRITERIA SHORTLY AFTER 8
AM ACROSS THE COASTAL WATERS SOUTH OF OREGON INLET. THE LOW PUSHES
OFF THE COAST AROUND MID DAY WITH WINDS SHIFTING TO WESTERLY AND
INCREASING AS PRES GRADIENTS TIGHTEN AND EXPECT WINDS ACROSS THE
REST OF THE WATERS TO REACH SMALL CRAFT CRITERIA IN THE AFTERNOON.
FOLLOWED WAVEWATCH CLOSELY FOR SEAS WHICH BUILD QUICKLY SAT MORNING
AND APPROACHING THEIR PEAK AROUND 5-8 FT SRN WATERS AND 4-6 FT NRN
WATERS LATE AFTERNOON.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 245 PM FRIDAY...STRONG COLD AIR ADVECTION BEHIND COLD FRONT
WILL LEAD TO STRONG CRAFT ADVISORY WINDS AND SEAS SATURDAY NIGHT
INTO SUNDAY NIGHT AS THE NORTH CAROLINA COAST WILL LIE IN THE
GRADIENT BETWEEN 1032 MB HIGH OVER KENTUCKY AND STRONG EXITING LOW
PRESSURE OVER THE NORTH ATLANTIC. WIND AND SEAS SUBSIDE MONDAY
INTO TUESDAY AS AXIS OF HIGH PRESSURE SETTLES OVER THE NORTH
CAROLINA COASTAL WATERS AND SOUNDS. A BRIEF PERIOD OF SMALL CRAFT
SEAS AND NEAR SMALL CRAFT LEVEL WINDS WILL LIKELY OCCUR ON THE
BACKSIDE OF ANOTHER SOUTHERN STREAM LOW TUESDAY NIGHT INTO
WEDNESDAY PER LATEST WAVEWATCH 4 GUIDANCE.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 6 PM EST SUNDAY FOR
AMZ135.
SMALL CRAFT ADVISORY FROM 4 PM SATURDAY TO 6 PM EST SUNDAY FOR
AMZ130.
SMALL CRAFT ADVISORY FROM 8 AM SATURDAY TO 6 AM EST MONDAY FOR
AMZ152-154.
SMALL CRAFT ADVISORY FROM 8 AM SATURDAY TO 3 PM EST SUNDAY FOR
AMZ156-158.
SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 6 AM EST MONDAY FOR
AMZ150.
&&
$$
SYNOPSIS...SK
NEAR TERM...JBM/SK
SHORT TERM...SK
LONG TERM...CTC
AVIATION...JBM/CTC
MARINE...JBM/SK/CTC
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
1243 AM EST SAT DEC 29 2012
.SYNOPSIS...
RAIN WILL MOVE INTO THE AREA LATE TONIGHT...PREVAILING THROUGH
SATURDAY MORNING AS LOW PRESSURE SCOOTS NORTHEAST FROM THE GULF
COAST STATES. THE LOW WILL INTENSIFY AS IT MOVES AWAY FROM THE
REGION SATURDAY AFTERNOON AND NIGHT...BRINGING BRISK WEST AND
NORTHWEST WINDS. BUILDING HIGH PRESSURE WILL IMPORT DRIER AND
COLDER AIR SUNDAY AND MONDAY...FOLLOWED BY A WEAK COLD FRONTAL
PASSAGE ON TUESDAY. A STORM SYSTEM OFFSHORE MAY BRING MORE RAIN
TO THE EASTERN CAROLINAS LATE NEXT WEEK.
&&
.NEAR TERM /THROUGH SATURDAY/...
AS OF 1230 AM SATURDAY...I HAVE DELAYED THE ONSET OF PRECIPITATION
BY A FEW HOURS PER RADAR TRENDS AND LATEST HRRR MODEL RUNS. ALSO
SHUT DOWN PRECIP MUCH FASTER SATURDAY AFTERNOON THAN WAS ORIGINALLY
FORECAST. VIRTUALLY NO MODEL GUIDANCE I CAN FIND KEEPS PRECIP
ANYWHERE AFTER 18Z SATURDAY. OTHERWISE NO SIGNIFICANT CHANGES TO
TEMPS/DEWPOINTS/WINDS ARE NEEDED. PREVIOUS DISCUSSION FROM 900 PM
FOLLOWS...
CLOUD COVER AND WEAK WARM SECTOR ADVECTION HAVE NEARLY LEVELED OFF
NOCTURNAL TEMPERATURE CURVES AND SEVERAL SITES POTENTIALLY MAY HAVE
ALREADY REALIZED MINIMUM TEMPERATURES FOR THE NIGHT. SURFACE LOW
NEAR MOBILE ALABAMA WILL MOVE QUICKLY NE OVERNIGHT...BRINGING A
DECENT OVER-RUNNING STRATIFORM TYPE RAINFALL. MOST-USABLE CAPE
ANALYSIS FROM NEAR TERM MODEL SUITES INDICATE ELEVATED INSTABILITY
WILL EXIST ALONG OUR VERY SOUTHERN COAST AT 12Z WITH THE BULK OF
INSTABILITY ALOFT REMAINING NEAR THE COAST AND OFFSHORE MAINLY AFTER
12Z SATURDAY...AND NO THUNDER WILL BE ADVERTISED...AT LEAST FOR THE
OVERNIGHT HOURS.
LIGHT E-NE WINDS OVERNIGHT WILL BECOME S-SE AND INTENSIFY INTO
THE PRE-DAWN HOURS OF SATURDAY...AS AN INVERTED SURFACE TROUGH
POSITIONED JUST OFFSHORE...IS DRAWN CLOSER TO THE COAST. THIS
SHOULD ENSURE RISING T/TD VALUES ACROSS THE EASTERN ZONES INTO
DAYBREAK...WHILE CONCURRENTLY INCREASING THE SURFACE CONVERGENCE
COMPONENT...LOCALLY BOOSTING OMEGA AND THE POTENTIAL FOR EMBEDDED
HEAVIER SHOWERS EARLY SATURDAY MORNING FROM MYR TO SUT TO ILM
TO HAMPSTEAD TO TOPSAIL ISLAND TO SURF CITY.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
AS OF 3 PM FRIDAY...A QUICK SHOT OF WARM AND MOIST AIR AS LOW
PRESSURE RACES ACROSS THE FORECAST AREA SAT MORNING. THIS AREA OF
LOW PRESSURE WILL BE WEAK AND RATHER BROAD AS IT MOVES OVERHEAD.
EXPECT THE MORNING WILL BE WET WITH A MODERATE RAIN FALLING. A
COASTAL TROUGH/WARM FRONT WILL LIE ACROSS THE COASTAL WATERS AND
MAY BRIEFLY SNEAK ONTO LAND DURING SAT MORNING. EXAMINATION OF
STABILITY PARAMETERS SUGGESTS THERE IS A RISK FOR ELEVATED
CONVECTION. THE INSTABILITY IS SMALL AND LIMITED TO AROUND 850
MB...WITH CAPE VALUES UP TO ABOUT 300 J/KG THUS...CAN NOT RULE
OUT A THUNDERSTORM/RUMBLE OF THUNDER...WITH PERHAPS A SLIGHTLY
HIGHER PROBABILITY ON THE COAST. THERE WILL HOWEVER BE NO SEVERE
WEATHER AS THE LOW LEVELS SHOULD REMAIN STABLE ENOUGH EVEN IN THE
VICINITY OF THE COASTAL TROUGH.
LOW PRESSURE WILL CONSOLIDATE AND STRENGTHEN RAPIDLY AS IT MOVES
OFF THE VIRGINIA CAPES SAT AFTERNOON AND THEN OFF THE NEW ENGLAND
COAST SAT NIGHT. THUS THE RAIN WILL SHUTOFF QUICKLY LATE MORNING
THROUGH MIDDAY. AS LOW PRESSURE DEEPENS...WEST TO NORTHWEST WINDS
ON THE BACKSIDE OF THE LOW WILL STRENGTHEN AS THE PRESSURE
GRADIENT TIGHTENS UP ACROSS THE EASTERN CAROLINAS. WINDS ARE
EXPECTED TO GUST TO 25 TO 30 MPH SAT AFTERNOON. THESE WINDS WILL
QUICKLY BRING DRIER AIR INTO THE AREA AND SO THICK MORNING CLOUDS
ARE EXPECTED TO ERODE...GIVING WAY TO PARTLY TO AT TIMES MOSTLY
SUNNY SKIES.
TEMPS WILL BE TRICKY...AND THE BUST POTENTIAL IS HIGH...ESPECIALLY
AT THE COAST WHERE SOUTHERLY WINDS MAY DEVELOP FOR A TIME EARLY
ON. COLDER AND DRIER AIR WILL BE ARRIVING IN THE WAKE OF LOW
PRESSURE...BUT THIS WILL BE MITIGATED BY AFTERNOON SUNSHINE AND
DOWNSLOPING WINDS. AT THIS TIME...WILL FORECAST COOLEST READINGS
ACROSS THE NORTHERN PEE DEE UP THROUGH LBT AND EYF...MID AND UPPER
50S. THERE IS A CHANCE FOR LOWER TO MID 60S FOR PORTIONS OF THE
SOUTHERN PEE DEE TO THE GRAND STRAND AND THEN UP THROUGH THE CAPE
FEAR REGION.
WINDS WILL BE SLOW TO DIMINISH SAT NIGHT AS THE GRADIENT WILL
REMAIN RATHER TIGHT...THUS TEMPS SHOULD BE RATHER UNIFORM ACROSS
THE AREA...LOWER TO MID 30S. SHOULD WINDS GO LIGHT EARLY SUN
MORNING...THERE MAY BE A FEW UPPER 20S WELL INLAND.
CHILLY HIGH PRESSURE WILL BUILD SOLIDLY ACROSS THE AREA SUN AND
SUN NIGHT. EVEN WITH CLOUDLESS SKIES...TEMPS WILL STRUGGLE TO GAIN
ANY UPWARD MOMENTUM. GIVEN 850 MB TEMPS WILL BE MINUS 1 TO MINUS 2
DEG C...EXPECT HIGHS IN THE MID 40S IN MOST LOCATIONS. THE BOTTOM
SHOULD QUICKLY DROP OUT OF THE THERMOMETER SUN NIGHT AS TEMPS FALL
SHARPLY DURING THE EVE. IDEAL RADIATIONAL COOLING IS EXPECTED WITH
LOWS BY MON MORNING IN THE 20S AND AS LOW AS THE LOWER 20S.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 3 PM FRIDAY...SURFACE HIGH PRESSURE AND LOW AMPLITUDE MID
LEVEL RIDGING BOTH GRADUALLY MOVE OFF THE COAST LATER MONDAY.
SHALLOW COOL SFC AIR MASS TO KEEP TEMPS CHILLY ESPECIALLY WITH
LATER DAY INC IN CLOUD COVER. MOISTURE ADVECTION GETS STRONGER
MONDAY NIGHT INTO TUESDAY. APPROACHING COLD FRONT TO ADD LIFT TO
THE ONGOING WARM/MOIST ADVECTION AND SOME LIGHT RAIN SHOULD BREAK
OUT DESPITE MID LEVEL FORCING BEING WEAK IN ZONAL FLOW. WEDNESDAY
WILL BRING A WEAK PUSH OF DRY AIR BEHIND THE BOUNDARY AS IT STALLS
NOT TOO FAR TO OUR SOUTH. MEANWHILE THE NEXT SYSTEMS ALOFT TAKE
SHAPE OVER THE PLAINS AND MEXICO (SPLIT FLOW). THE LATTER SHEARS
OUT AND STREAKS BY RAPIDLY CAUSING A FLAT WAVE OF LOW PRESSURE TO
DEVELOP ALONG THE OFFSHORE BOUNDARY. RAIN MAY ONCE AGAIN
OVERSPREAD THE REGION ON THURSDAY, THIS TIME FROM THE SOUTH. THE
NORTHERN BRANCH FEATURE ENDS UP BECOMING A BROAD POSITIVELY TILTED
TROUGH IN THE EAST THAT WILL HELP KEEP THE AREA VERY CHILLY.
&&
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
AS OF 06Z...HAVE PUSHED BACK THE ONSET OF PCPN ACROSS THE TERMINALS
AS PER THE LOCAL MODELS THAT SHOW RAIN OVERSPREADING THE REGION FROM
WEST TO EAST AFTER 08Z-10Z. SURFACE LOW TO MOVE RAPIDLY TO THE NE
WITH THE GFS BRINGING THE LOW RIGHT OVER THE CAPE FEAR REGION AND
ITS ASSOCIATED HEAVIER RAIN AS WELL. WILL MENTION A TEMPO GROUP FROM
12Z-15Z FOR THE COASTAL TAFS FOR CHANCE TSRA. SYSTEM MOVES RAPIDLY
TO THE NE WITH PCPN ENDING BY 15-16Z. WINDS SHIFT TO THE W AND PICK
UP TO AROUND 15KTS WITH GUSTS 20-25KTS AFTER 16-18ZZ. MODERATE
DEGREE OF CONFIDENCE IN EXPECTING IFR CEILINGS BETWEEN 12Z-15Z WITH
MAINLY MVFR CONDITIONS BETWEEN 09Z-12Z. VFR CONDITIONS EXPECTED
AFTER 16Z WITH ISOLATED MVFR IN CEILINGS AT THE COASTAL TERMINALS.
EXTENDED OUTLOOK...VFR CONDITIONS EXPECTED SUNDAY AND MONDAY. CHANCE
FOR RAIN TUESDAY. VFR EXPECTED WEDNESDAY.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 1230 AM SATURDAY...RAIN WILL NOT BEGIN UNTIL JUST A FEW HOURS
BEFORE DAYBREAK...BUT THUNDERSTORM CHANCES APPEAR TO BE INCREASING
AS A SLUG OF MODERATELY UNSTABLE AIR WILL DEVELOP JUST A FEW
THOUSAND FEET OVER THE OCEAN SURFACE BETWEEN 6 AM AND 11 AM SATURDAY
MORNING. THE SURFACE WARM FRONT HAS PUSHED ACROSS THE FRYING PAN
SHOALS BUOY LOCATION WHERE SFC WINDS ARE NOW SOUTHEAST. LOOK FOR
WINDS TO SHIFT EVEN NEARSHORE OVER THE NEXT FEW HOURS. THE BIGGEST
CHANGE TO THE FORECAST IS TO DELAY INCREASING SEA HEIGHTS BY SEVERAL
HOURS AS IT WILL TAKE TIME FOR STRONGER WINDS OFFSHORE TO TRANSLATE
INTO LARGER SEAS. THE FRYING PAN SHOALS BUOY IS STILL ONLY 2 FEET AT
LATEST REPORT. PREVIOUS DISCUSSION FROM 900 PM FOLLOWS...
INCREASING WINDS WILL BRING WORSENING MARINE CONDITIONS LATE TONIGHT
INTO EARLY SATURDAY AS AN APPROACHING SFC LOW OVER THE NORTHERN GULF
OF MEXICO MOVES SWIFTLY NE...RAMPING UP SOUTH WINDS OVER THE WATERS.
SEAS OF 2-3 FEET LATE THIS EVENING WILL APPROACH 5-6 FEET NEAR
DAYBREAK WITH POTENTIAL WIND GUSTS TO 25 KT TOWARD 12Z OR 7AM
SATURDAY. DEVELOPING RAIN COULD REDUCE VISIBILITIES TO LESS THAN 2
MILES IN RAIN AND MIST BY SUNRISE.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 3 PM FRIDAY...A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR
ALL WATERS SAT THROUGH MIDDAY ON SUN. WEAK LOW PRESSURE WILL MOVE
OVERHEAD SAT MORNING. A COASTAL TROUGH WILL LIKELY LIE ACROSS THE
WATERS SAT MORNING. LOW PRESSURE WILL INTENSIFY OFF THE VIRGINIA
CAPES...RESULTING IN A TIGHT PRESSURE GRADIENT BY SAT AFTERNOON
AND THIS GRADIENT WILL PERSIST THROUGH SAT NIGHT BEFORE BEGINNING
TO RELAX ON SUN. WILL INITIALIZE WITH A SOUTH WIND...BUT WINDS
WILL SHIFT QUICKLY TO THE W AROUND MIDDAY SAT AND THEN TO THE NW
SAT NIGHT. NNW WINDS SUN WILL BECOME NNE TO NE BY MON MORNING.
WINDS WILL BE AS HIGH AS AROUND 25 KT SAT AFTERNOON AND SAT
NIGHT...FALLING BELOW ADVISORY CRITERIA DURING SUN. SEAS WILL
QUICKLY BUILD SAT MORNING...AS HIGH AS 6 TO 8 FT ACROSS THE OUTER
WATERS. THE WESTERLY WINDS WILL HELP TO KNOCK WAVE HEIGHTS DOWN
ACROSS THE NEAR SHORE WATERS SAT AFTERNOON AND EVE. SEAS SAT NIGHT
WILL BE UP TO 4 TO 6 FT ACROSS THE OUTERMOST WATERS. SEAS WILL
DROP STEADILY DURING THE DAY SUN AND SUN NIGHT.
LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 3 PM FRIDAY...LIGHT WINDS AND DIMINUTIVE SEAS EXPECTED ON
MONDAY AS HIGH PRESSURE MAKES A SLOW EASTWARD TREK FROM THE
LANDMASS TO AN OFFSHORE POSITION. SO WHILE WIND SPEEDS WILL REMAIN
VERY LIGHT THERE SHOULD BE CONSIDERABLE CHANGES IN WIND DIRECTION
THROUGH THE DAY AND EVENING. A SOUTHERLY COMPONENT BECOMES
DOMINANT HOWEVER BY MONDAY NIGHT IN THE RETURN FLOW REGIME ON THE
WESTERN PERIPHERY OF THE ANTICYCLONE. BY TUESDAY THE APPROACH OF A
COLD FRONT WILL TIGHTEN THE GRADIENT SLIGHTLY AND A SMALL INCREASE
IN SEAS WILL BE NOTED. AS THE FRONT PUSHES THROUGH TUESDAY NIGHT A
SHARP VEER TO A NORTHERLY WIND WILL TAKE PLACE. THE BOUNDARY WILL
NOT TRAVEL VERY FAR TO THE SOUTH WHICH SHOULD PRECLUDE ANY BIG
POST-FRONTAL COLD SURGE OF HIGHER WINDS. NEVERTHELESS GUIDANCE
RAMPING UP TO WHERE ADVISORY WOULD BE NEEDED. NOT SURE IF THIS IS
CORRECT SO WILL CAP SEAS AT SCEC-WORTHY 5 FT FOR NOW.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 5 AM SATURDAY TO 1 PM EST
SUNDAY FOR AMZ250-252-254-256.
&&
$$
NEAR TERM...MJC/TRA
SHORT TERM...RJD
LONG TERM...MBB
AVIATION...MAC
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
330 AM CST SAT DEC 29 2012
.SHORT TERM...
TODAY-FORECAST CONFIDENCE MEDIUM
INVERTED SURFACE TROUGH AND LAKE ENHANCED BAND OF -SN TO
OCCASIONALLY MODERATE SN WILL AFFECT ERN CWA THIS MRNG AS THEY PIVOT
SOUTHWARD. BOTH NAM AND GFS SHOWING LOW LEVEL FN VECTOR RESPONSE TO
FRONTOGENETICAL FORCING TIED TO SURFACE TROUGH EARLY THIS MRNG IN
THE EAST WITH THESE FEATURES. HENCE ENOUGH CONFIDENCE THAT -SN WL
BE FALLING AFTER 12Z TO BUMP UP TO CATEGORICAL WORDING IN THE
EAST...WITH ADDITIONAL SNOWFALL MOSTLY LESS THAN AN INCH. EXTENDED
WINTER WX ADVY FOR SHEBOYGAN COUNTY TO 13Z TO ACCOUNT FOR LAKE
ENHANCED BAND MOVING THRU. CURRENT VSBY DOWN TO 3/4NM AT KSBM.
KMKX AND TMKE RADARS SHOWING 15 TO 20DBZ TIED TO THIS ENHANCED BAND
OVER NORTHEAST CWA. MORE IMPRESSIVE 25-30DBZ BAND HAS REMAINED
OFFSHORE OVER LAKE MI. NOT IMPOSSIBLE THIS COULD MOVE SOUTHWEST AND
AFFECT SOUTHERN OZAUKEE AND MILWAUKEE COUNTIES AROUND 12Z WHEN NAM12
SHOWS STRONG OMEGA AFFECTING THIS AREA. FORTUNATELY...LOW LEVEL
WINDS CONTINUE TO BACK THROUGH THE MORNING AND AFTERNOON...NOT
ALLOWING THE STRONG CONVERGENCE TO FOCUS ON ONE AREA FOR A PROLONGED
PERIOD OF TIME. BY 20Z...LAKE ENHANCED SNOWFALL AND SURFACE TROUGH
WILL HAVE SAGGED SOUTH OF THE AREA WITH LINGERING PATCHY -SN OR
FLURRIES IN ERN CWA.
TONIGHT-FORECAST CONFIDENCE MEDIUM
NORTHWEST WINDS IN THE LOW TO MID LEVELS WILL USHER DRIER AIR INTO
THE AREA OVERNIGHT AS SHORT WAVE RIDGING BUILDS UPSTREAM OVER THE
NORTHERN PLAINS. HOWEVER LINGERING LOW LEVEL MOISTURE AND THERMAL
TROUGH MAY RESULT IN STRATUS STICKING AROUND OR POSSIBLY
REDEVELOPING FOR A TIME OVERNIGHT...HENCE LOW CONFIDENCE ON AMOUNT
OF OVERNIGHT CLEARING AT THIS TIME.
SUNDAY-FORECAST CONFIDENCE HIGH
POLAR RIDGE OVERHEAD FIRST THING WITH A COLD START...BUT THEN
STRONG WARM ADVECTION OCCURRING DURING THE DAY. IN FACT...925 MB
TEMPS WARM TO ABOUT -2C...SUGGESTING TEMPERATURES APPROACHING 30.
SEEMS THAT MIXING WILL BE PRETTY MINIMAL WITH SNOW COVER SO MID
20S MORE LIKELY.
MONDAY-FORECAST CONFIDENCE MEDIUM
FRONT COMES THROUH FIRST THING WITH COLD ADVECTION DURING THE DAY.
925 MB TEMPS DROP FROM -4C TO -10C DURING THE DAY...IMPLYING THAT
READINGS MAY HOLD STEADY OR DROP IN THE MIDDAY AND EARLY
AFTERNOON. CONFIDENCE OVERALL WOULD BE HIGH BUT NAM HAS A SUBTLE
DIFFERENCE FROM OTHER MODELS. NAM KEEPS UPPER RIDGING STRONGER IN
EASTERN STATES AND IS A LITTLE SLOWER WITH NORTHERN BRANCH TROUGH
IN DAKOTAS...ALLOWING A STRONGER MOISTURE SURGE AHEAD OF
CONFLUENCE ZONE A TAD FARTHER NORTH THAN ALL OTHER MODELS. NAM
WOULD ALLOW A BIT OF SNOW IN THE SOUTHEAST BUT OTHER MODELS DRY
AND WILL KEEP IT DRY GIVEN THAT ECMWF AND GFS ARE USUALLY MORE
TRUSTWORTH BEYOND 36 HOURS THAN NAM.
.LONG TERM...
TUESDAY-FORECAST CONFIDENCE HIGH
COLD SHOT WITH 925 MB TEMPS AROUND -14C SUGGESTS NEAR ZERO MORNING
TEMPERATURES. CIPS ANALOGS HAVE 40-50% CHANCE OF BELOW ZERO LOWS
AND ABOUT 30% CHANCE OF -20C OR COLDER WIND CHILLS. CURRENTLY WE
ARE LOOKING AT ABOUT -15C WIND CHILLS IN THE WEST SO GETTING CLOSE
TO ADVISORY LEVELS.
WEDNESDAY-FORECAST CONFIDENCE MEDIUM
MODELS HAVE A CLIPPER SYSTEM MOVING THROUGH...WITH GFS FASTER AND
FARTHER NORTH WITH GEMNH AND ECMWF SLOWER AND FARTHER SOUTH. SINCE
GFS IS TYPICALLY FASTER THIS IS NOT SURPRISING. 00Z GFSE HAD HIGH
STANDARD DEVIATION OF ABOUT 10MB OVER MN...AND A COUPLE OF MEMBERS
WITH CLIPPER TRACKING SOUTH LIKE OTHER GUIDANCE. ADDED 20-30%
CHANCE OF SNOW DURING THIS PERIOD GIVEN ECMWF TRACK AND FACT THAT
COLD AIRMASS WITH DENDRITE ZONE AROUND 850 MB WILL MAKE IT EASY TO
PRODUCE SNOW.
THURSDAY-FORECAST CONFIDENCE MEDIUM
SHOULD BE COLD NO MATTER WHAT HAPPENS WITH CLIPPER WITH 925 MB
TEMPS AROUND -15C. COULD HAVE ANOTHER BELOW ZERO NIGHT AWAY FROM
THE LAKE ESPECIALLY IF THE POLAR RIDGE BUILDS IN AS FORECAST AND
SKIES CLEAR OUT. WIND CHILLS WILL AGAIN FLIRT WITH ADVISORY LEVELS
IN -10 TO -20C RANGE.
FRIDAY-FORECAST CONFIDENCE MEDIUM
BUILDING RIDGE ALOFT AND INTRUSION OF WESTERLY LOW LEVEL FLOW AND
MODIFIED PACIFIC AIRMASS INDICATES POTENTIAL FOR MODERATION.
PROBLEM IS THAT WITH EXTENSIVE SNOW COVER STRONG INVERSION COULD
LIMIT HOW MUCH MIXING DOWN OF WARM AIR OCCURS SO IT SHOULD BE
MILDER BUT MAY NOT GET MUCH ABOVE NORMAL.
&&
.AVIATION/12Z TAFS/...
AREAS OF -SN WL KEEP VSBYS AND CIGS IN MVFR OR
LOWER CATEGORY FOR A TIME THIS MRNG IN ERN TAF SITES. AREAS OF -SN
WL DIMINISH LATER THIS MRNG AND AFTER WITH IMPROVING CIGS EXPCD
TNGT. RAP GUIDANCE HAS BEEN THE BEST IN HANDLING LOW LEVEL RH LATELY
AND KEEPS LOW CLOUDS IN THRU 00Z/30. CONFIDENCE LOW ON CLEARING
TNGT AS EXTENSIVE STRATUS SHIELD/RESIDUAL MOISTURE CAUGHT IN
VICINITY OF RIDGELINE ACROSS MN/IA...WL LIKELY WORK ITS WAY EWD
TNGT.
&&
.MARINE...EXPECT WIND DIRECTION TO VARY FROM THE NORTHWEST TO NORTH
TO NORTHEAST THIS MORNING AS SURFACE TROUGH SLIPS SOUTH ACROSS
NEARSHORE AREAS. SUSTAINED WINDS AND GUSTS ARE EXPECTED TO REMAIN
BELOW 20KTS. NEXT POTENTIAL FOR STRONGER WIND GUSTS LATER SUNDAY
NIGHT AND MONDAY AHEAD OF NEXT LOW PRESSURE SYSTEM APPROACHING
WESTERN GTLAKES.
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER WEATHER ADVISORY UNTIL 7 AM CST THIS MORNING FOR WIZ052.
LM...NONE.
&&
$$
TODAY/TONIGHT AND AVIATION/MARINE...MBK
SUNDAY THROUGH FRIDAY...CRAVEN
AREA FORECAST DISCUSSION
NWS TALLAHASSEE FL
1100 AM EST Sat Dec 29 2012
.NEAR TERM [Rest of Today]...
Updated at: 1100 am EST
Not many changes were made to the forecast today. Cloud cover was
increased slightly, especially in the morning, as stratus has been
slow to break up so far. Temperatures are trending fairly close to a
blend of the 11z RAP and 12z NAM, so that is what the hourly
temperature forecast was based on for the rest of the day. There are
likely to be non-diurnal trends in the temperatures for today, with
cold air advection offsetting the typical diurnal heating. Thus, the
temperatures through the early-to-mid afternoon are likely to be
fairly stready, falling sharply around and after sunset.
&&
.SHORT TERM [Tonight Through Monday]...
For tonight, with a cold airmass and decoupling winds, there is high
confidence that all but the SE Big Bend will see a freeze. Local
confidence tool places highest probabilities (100%) across NW third
of our area down to nil chances across SE Big Bend. Guidance shows
that CAA should be strong enough to offset a slight breeze as high
remains to our NW. Freeze Watch remains in effect for all but the SE
Big Bend from 07-14z Sunday. This watch will likely be upgraded to a
warning later today. Wind chills are likely to be in the 20s across
much of the area, and perhaps isolated upper teens in SE Alabama so
a wind chill advisory may also be issued later today for this area.
On Sunday, high will build north of the region with ridge likely
extending from Appalachians down to the Nrn Gulf of Mex. So expect
another cool day with highs in the low to mid 50s to be followed by
another chilly Sunday Night, with the potential for yet another more
limited freeze as high pressure becomes centered over the
Southeast. Local confidence tool with 70% chance of freezing temps
NRN tier GA counties down to zero coastal Panhandle counties. On
Monday, next upper trough to move from Rockies EWD to MS Valley
by nightfall. this will help shift local surface high ewd with
veering winds ahead of this the next weather system. as a result,
temps will begin to rise to the low to mid 60s.
&&
.Long Term [Monday night through next Saturday]...
Not much change to the forecast since this time yesterday. The
period is forecast to begin with zonal flow on the toes of an
approaching, weak, shortwave entering the Southern Plains with high
pressure just beginning to break down at the surface. As the
shortwave grazes the Gulf coast, surface cyclogenesis will commence,
and the entire system will move into the Southeast on Wednesday. It
will take another shortwave developing in the Southern Plains early
on Thursday to completely clear out the remnants of the
aforementioned system as another surface low and attendant front
pass through the Tri-State area Thursday through early Friday.
Instability will be greatly lacking with both systems and only
showers are expected. Near average to slightly below average
temperatures are expected to dominate the extended range forecast.
&&
.AVIATION [through 12z Sunday]...
Updated at: 649 am EST
Showers have come to an end at all terminals. Ceilings will bounce
between IFR and MVFR for the next hour or so before stabilizing to
MVFR restrictions for all terminals through the first part of the
day. Thereafter, it is likely that all but KABY will scatter to VFR.
KABY will take a bit longer and will likely have at least high end
MVFR ceilings for much of the day. The only other concern will be
gusty WNW winds. Expect gusts between 25 to 30 knots early, falling
to around 20 knots later in the afternoon. VFR conditions will
prevail overnight tonight.
&&
.MARINE...
Latest forecast winds show 20-kt winds spreading across wrn legs and
beginning to impact eastern legs, so advisory remains in effect for
all the waters. A winds shift was already occurring as a cold front
crosses the marine area. Offshore winds and seas should then stay
elevated for much of the weekend with seas peaking at 8 feet at the
offshore buoys. Winds and seas will drop below headline criteria by
Sunday evening and then gradually veer to onshore once again for
early next week. The next cold front is forecast to cross the waters
Tuesday evening.
&&
.FIRE WEATHER...
Although relative humidity values will be below the "critical" 35%
mark for north Florida on Sunday, ERC values are currently forecast
to be very low (for Saturday at least). Thus if this remains
constant, Red Flag criteria will not be met. Beyond Sunday, relative
humidity values will climb above 35% relieving any Red Flag concerns.
&&
.HYDROLOGY...
No flood concerns expected from the recent rainfall. One half inch
rainfall forecast tonight will help keep flows up a bit on the
smaller creeks and streams some possibly reaching action stage in
the upper drainages. Meanwhile routed flow down stream continues
to generate minor rises on the lower Choctawhatchee, Ochlockonee
and Withlacoochee Rivers. Nothing significant is happening on the
Chattahoochee or Apalachicola Rivers from the recent rainfall and
nothing significant is expected with tonight`s rainfall. All other
drainages including the Suwannee River are pretty much flat.
Models continue to indicate a more significant rain event around
New Years that might last a day or two. Though the amounts do not
look enough to generate a flood event, this could be a welcome
rain across the drought affected areas.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 60 31 55 31 66 / 10 0 0 0 10
Panama City 55 35 55 40 65 / 0 0 0 0 10
Dothan 49 28 52 33 62 / 10 0 0 0 10
Albany 50 28 54 30 64 / 10 0 0 0 10
Valdosta 63 31 54 32 66 / 10 0 0 0 0
Cross City 70 32 57 33 70 / 10 0 0 0 0
Apalachicola 63 35 55 41 64 / 10 0 0 0 10
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...FREEZE WATCH from late tonight through Sunday morning for
Calhoun-Central Walton-Coastal Bay-Coastal Franklin-
Coastal Gulf-Coastal Wakulla-Gadsden-Holmes-Inland Bay-
Inland Franklin-Inland Gulf-Inland Jefferson-Inland
Wakulla-Inland Walton-Jackson-Leon-Liberty-South Walton-
Washington.
GA...FREEZE WATCH from late tonight through Sunday morning for
all zones.
AL...FREEZE WATCH from late tonight through Sunday morning for
Coffee-Dale-Geneva-Henry-Houston.
GM...SMALL CRAFT ADVISORY until 10 AM EST Sunday for all zones.
&&
$$
NEAR TERM...Lamers
SHORT TERM...Block
LONG TERM...Harrigan
AVIATION...Harrigan
MARINE...Block
FIRE WEATHER...Harrigan
HYDROLOGY...Lanier
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
555 AM CST SAT DEC 29 2012
.UPDATE...
RECENT RAP TRENDS ARE RAISING QUESTIONS ON HOW FAST THE CLEARING
WILL OCCUR DURING THE AFTERNOON HOURS. THE 0.5KM AGL CONDENSATION
PRESSURE DEFICITS CONTINUE TO INDICATE BREAKS DEVELOPING IN THE
STRATUS THIS AFTERNOON AS STRONGER SUBSIDENCE MOVES IN BEHIND THE
DEPARTING SHORTWAVE. HOWEVER...THE TRUE CLEARING MAY NOT OCCUR
OVER THE EASTERN 60 PERCENT OF THE CWFA UNTIL CLOSER TO SUNSET.
IF CORRECT...THEN THE CLEARING DEVELOPING THIS AFTERNOON WOULD
HAVE TO BE SLOWED DOWN. LIKEWISE...THE LONGER CLOUDS HOLD AROUND
THE SMALLER THE DIURNAL RISE IN TEMPERATURES. GIVEN THE CLOUDS AND
CAA...MOST AREAS WILL REMAIN NEARLY STEADY THROUGH THE DAY OR ONLY
SEE A FEW DEGREES RISE. THE EASTERN THIRD TO HALF OF THE CWFA
WOULD HAVE THE BEST CHANCE AT SEEING TEMPERATURES RISE A COUPLE OF
DEGREES DURING THE DAY.
PERSISTENT FLURRIES BACK INTO CENTRAL IOWA MEANS THAT SCATTERED
FLURRIES WILL BE POSSIBLE ACROSS THE ENTIRE AREA DURING THE
MORNING. BASED ON VISIBILITIES...THERE ARE ISOLD SHSN EMBEDDED
WITHIN THE FLURRIES. THE AREAL COVERAGE ON THE SHSN IS AT BEST 10
PERCENT SO WILL CONTINUE WITH ONLY THE MENTION OF FLURRIES. ..08..
&&
.AVIATION...
CONDITIONS ARE MAINLY MVFR WITH FLURRIES ACROSS IOWA/ILLINOIS BUT
THERE ARE POCKETS OF VFR AND IFR CONDITIONS. THERE ARE ISOLD SHSN
WITH LOCALLY LOWER MVFR CIGS/VSBYS. SUBSIDENCE DEVELOPING AFT
18Z/29 WILL ALLOW THE STRATUS DECK TO DEVELOP BREAKS AS CLEARING
MOVES EAST ACROSS IOWA. VFR CONDITIONS ARE EXPECTED TO DEVELOP BY
OR AFTER 00Z/30 FOR ALL TAF SITES. ..08..
&&
.PREV DISCUSSION... /ISSUED 300 AM CST SAT DEC 29 2012/
SYNOPSIS...
06Z SFC ANALYSIS HAS SEVERAL LOWS IN THE OHIO AND TENNESSEE VALLEYS.
INVERTED TROFS RAN FROM A LOW NEAR KSDF INTO LAKE MICHIGAN AND OHIO.
DEW POINTS WERE IN THE 20S AND 30S OVER THE GREAT LAKES AND
SOUTHEAST WITH SINGLE DIGITS AND TEENS IN THE PLAINS.
SHORT TERM...TODAY AND TONIGHT...
CLEARING TRENDS AND PRECIPITATION POTENTIAL ARE THE IMMEDIATE CONCERNS.
SATELLITE CONTINUES TO SHOW PLENTY OF ST TRAPPED BELOW THE INVERSION.
WHAT APPEARS TO REPRESENT THE BACK EDGE OF THE CLOUDS REASONABLY WELL IS
THE 0.5KM AGL CONDENSATION PRESSURE DEFICITS FROM THE RAP MODEL WITH
SOME LOOSE AGREEMENT WITH THE WRF/GFS AT THE SAME LEVEL. ASSUMING THAT
THIS IS CORRECT...CLOUDS WILL CONTINUE ACROSS THE AREA THROUGH THE
MORNING FOLLOWED BY FAIRLY SIGNIFICANT CLEARING DURING THE AFTERNOON
HOURS AS STRONGER SUBSIDENCE DEVELOPS BEHIND A DEPARTING SHORTWAVE. THE
FAR EASTERN PARTS OF THE CWFA MAY NOT CLEAR UNTIL SHORTLY AFTER SUNSET.
RAP MODEL TRENDS ALSO SHOW NEUTRAL TO WEAK F VECTOR CONVERGENCE ACROSS
MOST THE THE CWFA DURING THE MORNING HOURS WITH LOW CONDENSATION
PRESSURE DEFICITS. THUS SCATTERED FLURRIES SHOULD CONTINUE ACROSS MOST
OF THE CWFA DURING THE MORNING WITH FLURRIES ENDING OVER THE EASTERN
HALF OF THE CWFA DURING THE AFTERNOON.
BASED ON CURRENT TEMPERATURES ACROSS THE AREA...CAA SHOULD ALLOW A
DROP OF ABOUT 1-2 DEGREES PRIOR TO SUNRISE ACROSS THE AREA. CAA
CONTINUES THROUGH THE DAY SO TEMPERATURES WILL REMAIN EITHER STEADY
OR ONLY RISE A FEW DEGREES DURING THE DAY.
TONIGHT...CLEAR OR NEARLY CLEAR SKIES SHOULD BE SEEN ACROSS THE AREA.
THE SNOW FIELD COMBINED WITH LIGHT WINDS ARE EXPECTED TO CREATE A WIDE
RANGE IN TEMPERATURES. SINGLE DIGITS SHOULD BE SEEN ACROSS A MAJORITY OF
THE CWFA. IT IS CONCEIVABLE THAT SUB ZERO READINGS MAY BE SEEN OVER THE
RELATIVELY DEEPER SNOW PACK ACROSS THE NORTHWEST PART OF THE CWFA.
08
LONG TERM...SUNDAY THROUGH NEXT FRIDAY...
MOSTLY DRY TO DRY CONDITIONS WITH WELL BELOW NORMAL TEMPERATURES.
OVERVIEW...INITIALIZATION GOOD WITH LITTLE SENSIBLE WEATHER ISSUES
BESIDES NORMAL WINTER COLD AIR BL MOISTURE ISSUES OVER SNOW PACK.
RUN TO RUN CONTINUITY SUPPORTS A 70/30 BLEND OF GFS/HI-RES ECMWF WITH
NAM TOO FAR NORTH ON MONDAY SYSTEM. PERSISTENCE SUPPORTS WHEN SKIES
ARE FAIR FOR SLIGHTLY LARGER DIURNAL RANGES THAN GUIDANCE.
SUNDAY...LITTLE CHANGE WITH INCREASING HIGH CLOUDS LATE AND OVERNIGHT
WITH MID 20S NORTH TO LOWER TO MIDDLE 30S SOUTHWEST. SUNDAY NIGHT...
SW WINDS OF 5 TO 15 MPH AND MID/HIGH CLOUDS SUPPORT NEARLY STEADY
TEMPERATURES CENTRAL AND SOUTHEAST SECTIONS WITH FALLING TEMPS FAR
NW AS NEXT ARCTIC FRONT ARRIVES.
MONDAY...KEPT LOW POPS SOUTHEAST SECTIONS AS ARCTIC FRONT WITH NW
UPPER FLOW TO CUT OFF MOISTURE TRANSPORT OVER NW SECTIONS.
TEMPERATURES NEARLY STEADY BEHIND FRONT AND FALLING LATE PM IN SE
SECTIONS. LATEST ANALYSIS AND TOOLS SUGGEST ANY SNOW AMOUNTS IN SOUTH
TO BE LESS THAN IN INCH. MONDAY NIGHT...SKIES TO CLEAR WITH
TEMPERATURES CRASHING TO COLDEST READINGS YET THIS WINTER WITH BELOW
ZERO READINGS NW TO LOWER TEENS FAR SE SECTIONS.
TUESDAY THROUGH FRIDAY...COLD NORTHERLY UPPER LEVEL FLOW WITH NEXT
UPPER TROUGH AND ARCTIC FRONT TO ARRIVE LATE WEDNESDAY. THIS SYSTEM
IS TAILORED FOR LATER SHIFTS TO ADD FLURRIES DUE TO VERY COLD AIR
ALOFT AND CYCLONIC CONVERGENT TURNING. MINS FRIDAY AM MAY STILL BE
A CATEGORY OR TWO TOO MILD WITH HI/S STRUGGLING TO MAKE DOUBLE DIGITS
NW SECTIONS THURSDAY AND FRIDAY...15-20 DEGREES BELOW NORMAL.
NICHOLS
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
1010 AM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE RAPIDLY DEVELOPING ALONG THE CAROLINA COAST WILL
TRACK NORTHEAST OFF CAPE HATTERAS THIS AFTERNOON...AND TO INTO
THE CANADIAN MARITIMES ON SUNDAY. HIGH PRESSURE BUILDS ACROSS THE
MID-ATLANTIC THROUGH SUNDAY NIGHT BEFORE SHIFTING SOUTHEAST ON
MONDAY. THE NEXT DISTURBANCE WILL AFFECT THE REGION LATE MONDAY
NIGHT AND TUESDAY. AN UPPER TROUGH THEN LOOKS TO PERSIST OVER THE
NORTHEASTERN STATES THROUGH THE END OF THE WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 1430Z...PHASING HAS BEGUN WITH PRECIP VOID BETWEEN THE
NORTHERN UPPER LOW OVER THE MIDWEST AND THE COASTAL LOW IN THE
SOUTHERN STREAM FILLING IN QUICKLY ACROSS THE LWX CWA. THE WINTER
WEATHER ADVISORY WAS MAINTAINED FOR ALL AREAS TODAY...WITH A NOTE
THAT FOR CENTRAL MARYLAND AND NORTHERN VIRGINIA THE HIGHER SNOW
TOTALS WOULD BE AT LEAST ABOVE A FEW HUNDRED FEET. BANDS OF
PRECIP...INDICATIVE OF COASTAL CYCLOGENESIS NOW EXTEND FROM THE
MASON-DIXON TO THE OUTER BANKS. THE RAIN SNOW LINE IS OVER THE
WESTERN SUBURBS OF BALT-WASH...IN LINE WITH THE ADVISORY. PRECIP
INTENSITY WILL CONTINUE TO INCREASE AS EVERYTHING SHIFTS EAST WITH
THE COASTAL LOW BOMBING OUT /RAPID PRESSURE FALLS/. IT WOULD NOT
BE SURPRISING TO SEE A QUICK 3 OR 4 INCHES ABOVE 700 FT ALONG THE
MASON DIXON /EAST FROM HAGERSTOWN/ WHERE THE TEMPERATURE PROFILE
SUPPORTS ALL SNOW. WILL CONTINUE MONITORING REPORTS BUT CONFIDENCE
IS FOR STICKING WITH THE ADVISORY THROUGH THE EVENT.
ALREADY LOOKING AT THE BACK EDGE OF PRECIP OVER THE SHENANDOAH
VALLEY WHICH IS IN LINE WITH HRRR GUIDANCE AND SATELLITE WV
IMAGERY OF THE DRY SLOT. PLAN WAS TO CANCEL ADVISORY FOR SWRN
ZONES EAST OF THE ALLEGHENY FRONT AROUND MIDDAY AND THAT LOOKS TO
BE ON TRACK. THE RADAR COVERAGE WILL PIVOT A BIT MORE NW TO SELY
AS THE LOW MOVES NORTHEAST...SO PRECIP IS EXPECTED TO CONTINUE INTO THE
MID AFTERNOON FOR NERN ZONES /I.E. BALTIMORE REGION/.
ADVISORY EXTENDED THROUGH TONIGHT FOR WEST OF THE ALLEGHENY FRONT
WITH UPSLOPE SNOW CONTINUING IN EARNEST THROUGH TONIGHT...LIGHT
SNOW AND FLURRIES FOR SUNDAY. 5-7 INCHES OUT THERE /24 HR ADVISORY
CRITERION FOR THE WESTERN FIVE COUNTIES IS 8 INCHES/.
WIND TONIGHT...COLD AIR ADVECTION AND THE RAPIDLY DEVELOPING LOW
OFF THE MID ATLANTIC COAST WILL PRODUCE STRONG GUSTS OVERNIGHT.
NEAR WIND ADVISORY LEVELS /46 MPH GUSTS/ FOR THE RIDGELINES...BLUE
RIDGE AND WEST...WITH 30 TO 35 MPH GUSTS AT LOWER ELEVATIONS
INCLUDING THE BALT-WASH METRO. WIND CHILLS INTO THE TEENS
EVERYWHERE EXCEPT LOWER SRN MD /AND SINGLE DIGITS IN THE POTOMAC
HIGHLANDS/.
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
SUNDAY APPEARS TO BE THE NICER DAY OF THE WEEKEND...BUT ONLY IF YOU
ARE LOOKING OUTSIDE FROM INDOORS DUE TO WIND. A MOSTLY SUNNY SKY IS
EXPECTED... BUT HIGHS WILL NOT GET OUT OF THE 30S IN MOST
AREAS...AND A BITING BREEZE WILL YIELD WIND CHILLS IN THE 20S MOST
OF THE DAY. ONLY PRECIP IN PLAY IS UPSLOPE...WHICH WILL BE
TAPERING OFF BY EARLY AFTERNOON SUNDAY. WINDS SHOULD ALSO TAPER
OFF AFTER SUNSET...LEADING TO A CHILLY SUNDAY NIGHT WITH
WIDESPREAD LOWS AROUND 20 AWAY FROM THE CITIES.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
NEW YEARS EVE WILL FEATURE A BRIEF BREAK BETWEEN SYSTEMS IN
FAST-MOVING ZONAL FLOW...WITH PRECIP CHANCES RETURNING TO THE
ALLEGHENY FRONT BY LATE MONDAY AFTERNOON AND ESPECIALLY MONDAY
NIGHT. HAVE REMOVED ALL POPS EAST OF THE HIGHLANDS THOUGH.
UPPER SUPPORT DOES ARRIVE GRADUALLY ON NEW YEARS DAY. ALTHOUGH THE
OPERATIONAL MODELS ARE SHOWING THE BULK OF THE PRECIP TO THE SOUTH
OF THE AREA...ENSEMBLES LEND ENOUGH SUPPORT TO RETAIN CHANCE POPS
JUST ABOUT EVERYWHERE. BROAD BRUSHED MOST OF THE AREA WITH RAIN OR
SNOW WORDING...BUT HIGHS ARE SOLIDLY ABOVE FREEZING SO RIGHT NOW
THIS DOES NOT APPEAR TO BE A BIG DEAL. WORTH MONITORING THOUGH.
MODEL AND ENSEMBLE TRENDS ARE TO PUSH THE PRECIP OUT TUESDAY
NIGHT...AND SO HAVE FOLLOWED SUIT BY LEAVING ONLY A SLIGHT CHANCE
FOR SNOW.
THE SECOND HALF OF THE WEEK WAS LEFT UNCHANGED FOR NOW DUE TO
UNCERTAINTY IN THE DETAILS OF THE PATTERN. THERE COULD BE A WEAK
CLIPPER SYSTEM TOWARD THE END OF THE WEEK...BUT WHAT DEFINITELY
APPEARS LIKELY IS THINGS GETTING EVEN COLDER THAN THEY ARE ALREADY.
ENSEMBLES SHOW HIGH PRESSURE OVERTAKING MUCH OF THE COUNTRY...AND
THIS WILL PUMP COLD AIR INTO A LARGE PART OF THE CONUS. THE GFS
ENSEMBLE MEAN MAX TEMP FOR FRIDAY IS BELOW FREEZING OVER OUR ENTIRE
AREA. OUR FORECAST IS NOT QUITE THAT COLD YET SINCE THESE THINGS DO
SEEM TO SOMETIMES TREND WARMER OVER TIME. THE LAST COMPLETELY
SUBFREEZING DAY /HIGH BELOW 32/ AT DCA WAS NEARLY TWO YEARS
AGO...JAN 22 2011.
&&
.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
IFR CIGS AND VSBYS THROUGH THE AFTERNOON...ENDING EARLY AFTERNOON
FOR KCHO...WITH LIFR AT TIMES IN SNOW /NW OF BWI AND DCA/.
PRECIPITATION WILL END FROM SOUTHWEST TO NORTHEAST DURING THROUGH
THE REST OF THE DAY. BEHIND THE SYSTEM...VFR CONDITIONS RETURN
AND WINDS SHIFT TO THE NORTHWEST GUSTING TO 25 KT TONIGHT.
GUSTY WINDS ON SUNDAY...WITH NW WIND GUSTS 25 TO 30 KT.
PRECIPITATION... SNOW WITH SOME RAIN...POSSIBLE AT ALL TERMINALS
ON TUESDAY.
&&
.MARINE...
SOUTHEAST FLOW 10 TO 15 KT THROUGH THE EARLY AFTERNOON...SWITCHING
WLY/NWLY THIS AFTERNOON AND INCREASING AS A RAPIDLY DEVELOPING STORM
SYSTEM MOVES FROM THE CAROLINA COAST TO A POSITION OFF THE MID-
ATLANTIC COAST. GRADIENT STRENGTHENS AS THE STORM INTENSIFIES. SCA
IS ALREADY IN EFFECT FOR TONIGHT. LOCAL ENHANCEMENT DOWN THE BAY
COULD BRING WIND GUSTS CLOSE TO GALE FORCE TONIGHT.
EXTENDED SCA THROUGH SUNDAY FOR ALL THE WATERS AS GUSTY WINDS ARE
EXPECTED TO CONTINUE. THOSE WINDS MAY TAPER OFF ON THE TIDAL POTOMAC
BY EARLY AFTERNOON BUT JUST CARRIED IT FOR ALL ZONES FOR NOW. SCA
MAY NEED TO BE EXTENDED INTO SUNDAY NIGHT FOR THE LOWER MARYLAND BAY
AND PERHAPS LOWERMOST TIDAL POTOMAC.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR MDZ501.
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR
MDZ003>007-009-010.
WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
MDZ502.
VA...WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR VAZ503.
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR VAZ028-
030-031-042-501.
WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
VAZ025>027-029-038>040-504.
WV...WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR WVZ501-503-
505.
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR
WVZ051>053.
WINTER WEATHER ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
WVZ050-055-502-504-506.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 PM EST SUNDAY
FOR ANZ530>543.
&&
$$
SYNOPSIS...JCE/BPP
NEAR TERM...BAJ/BPP
SHORT TERM...JCE
LONG TERM...JCE
AVIATION...JCE/BAJ/BPP
MARINE...JCE/BAJ/BPP
AREA FORECAST DISCUSSION...UPDATED FOR 12Z TAFS
NWS TWIN CITIES/CHANHASSEN MN
540 AM CST SAT DEC 29 2012
.DISCUSSION...ISSUED 427 AM CST
.SHORT TERM...TODAY THROUGH MONDAY NIGHT.
STRATUS HAS REDEVELOPED ACROSS ALL OF MN AND WI OVERNIGHT WITH
ONLY SMALL SIGNS OF ERODING OVER FAR WRN MN EARLY THIS MORNING.
AREAS OF FREEZING FOG HAVE ALSO FORMED WITH SOME VISIBILITY
RESTRICTIONS DOWN TO 1/4 MILE. BECAUSE THE DGZ IS SO LOW AND
SATURATED...HAVE ALSO SEEN SEVERAL OBS REPORTING FLURRIES OR LIGHT
SNOW SHOWERS.
CONFIDENCE IS QUITE LOW WITH RESPECT TO TIMING THE CLOUD
DISSIPATION TODAY. NAM AND RAP ARE MOST PESSIMISTIC KEEPING LOW
CLOUDS IN THROUGH THE AFTERNOON. GFS AND LAMP ARE A LITTLE MORE
OPTIMISTIC WITH CLEARING THIS AFTERNOON. GIVEN THE TIME OF YEAR
AND HOW SOLID IT LOOKS ON SATELLITE...AM LEANING TOWARD THE MORE
PESSIMISTIC SOLUTION. AS A RESULT OF THE WIDESPREAD
STRATUS...TEMPERATURES REMAINED A BIT WARMER THAN ANTICIPATED
OVERNIGHT AND AS OF 4 AM ARE NEAR FORECAST HIGHS FOR TODAY. LITTLE
DIURNAL CLIMB EXPECTED THOUGH DUE TO SAID CLOUDS AND WEAK CAA SO
STILL FORECASTING HIGHS IN THE TEENS.
CLEARING SHOULD ARRIVE TONIGHT ACCORDING TO ALL AVAILABLE
GUIDANCE. THERE IS SOME CONCERN HOWEVER THAT IF THEY DO NOT
DISSIPATE THIS AFTERNOON THEY MAY STICK AROUND THROUGH TONIGHT AS
THE INVERSION INTENSIFIES. ASSUMING THE GUIDANCE IS RIGHT...
TONIGHT SHOULD BE A COLD ONE AS A RIDGE AXIS SETTLES OVERHEAD.
LOWS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO ARE EXPECTED.
LOW PRESSURE WILL ZIP ACROSS SOUTHERN CANADA SUNDAY WITH A COLD
FRONT ARRIVING SUNDAY EVENING. WAA AHEAD OF THIS SYSTEM WILL BRING
A QUICK REBOUND OF TEMPS BACK INTO THE 20S. COULD SEE SOME
FLURRIES ACROSS CNTRL MN AND WI WHERE MOISTURE DEPTH AND FORCING
SHOULD BE GREATER...OTHERWISE THE COLD FRONT WILL BE DRY. VERY
STRONG CAA BEHIND THE FRONT WILL BRING STEADY OR FALLING TEMPS
INTO THE SINGLE DIGITS COME MONDAY AS 925 MB TEMPS CRASH TO -18C.
A RIDGE WILL SETTLE OVERHEAD MONDAY NIGHT. CLEAR SKIES...LIGHT
WINDS...AND A VERY COLD AIRMASS SHOULD ALLOW MOST PLACES TO
PLUMMET INTO THE TEENS BELOW ZERO...AND PERHAPS TO 20 BELOW IN
SOME OF THE COLDEST LOCATIONS. THE PLACEMENT OF THE RIDGE WILL BE
CRUCIAL. GFS HAS BEEN FURTHEST EAST WITH IT AND BRINGS WAA ACROSS
WRN MN LATE MONDAY NIGHT WITH THE COLDEST TEMPS ACROSS WI.
NAM/DGEX/GEM/ECMWF HAVE BEEN A BIT FURTHER WEST WITH THE CORE OF
THE COLD AIR. INTERESTINGLY...THE 29.00Z NAM/GEM...28.18Z
DGEX...AND 28.12Z EURO HAD GOOD CONSISTENCY WITH TEMPS RANGING
FROM NEAR -22F OVER ERN CHIPPEWA CO MN...TO ABOUT -5F IN THE TWIN
CITIES METRO. LEANED TOWARD THOSE RAW SOLUTIONS FOR THIS FORECAST
AND DISCARDED THE GFS. 29.00Z EURO CAME IN A TAD WARMER. WITH
TEMPS SUCH AS THESE...IT WON/T TAKE MUCH TO BRING THE WIND CHILL
WAY DOWN. EVEN A 5 KT WIND WOULD RESULT IN -20 TO -30F.
.LONG TERM...NEW YEARS DAY THROUGH FRIDAY.
RIDGE SETTLES SOUTH WITH RETURN FLOW ALLOWING ANOTHER QUICK
REBOUND OF TEMPS BACK INTO THE TEENS ON NEW YEARS DAY.
ANOTHER SYSTEM ZIPPING ACROSS THE NORTHERN GREAT LAKES WILL BRING
A WEAK FRONT SOUTH ON TUESDAY. MEANWHILE...YET ANOTHER SYSTEM
WILL DIVE SOUTHEAST INTO THE NORTHERN PLAINS TUESDAY NIGHT AND
BRING A STRONG COLD FRONT THROUGH WEDNESDAY OR WEDNESDAY EVENING.
THIS SYSTEM MAY BRING A BIT OF LIGHT SNOW BEFORE ANOTHER SURGE OF
ARCTIC AIR SPILLS SOUTH. COULD SEE A SIMILAR SCENARIO FROM EARLIER
IN THE WEEK WITH LOWS IN THE TEENS BELOW ZERO THURSDAY MORNING AND
HIGHS IN THE SINGLE DIGITS. THIS ONE HAS A LITTLE MORE UNCERTAINTY
WITH THE POTENTIAL FOR CLOUDS TO LINGER SO DID NOT GO TOO CRAZY
WITH TEMPERATURES YET.
&&
.AVIATION.../12Z TAF ISSUANCE/
A RATHER MESSY AVIATION FORECAST WITH SOME CLEARING CURRENTLY
PUSHING INTO W MN...BUT STRATUS/FOG REFORMING UNDER SFC RIDGE IN E
SODAK. RWF WILL PRBLY GO SCT SHORTLY...BUT THINK THAT IFR CONDS WILL
REFORM FOR A FEW HRS. SIMILAR SITU FOR AXN. IFR CONDS ON THE W
DOORSTEP OF STC WILL MOVE INTO THAT TAF VERY SHORTLY AND LAST THRU
THE MRNG. REMAINING TAFS SHUD REMAIN MVFR THIS MRNG WITH IFR CONDS
LIKELY STAYING FARTHER WEST. SLO IMPRVG TREND DRNG THE AFTN...BUT
NO MUCH CONFIDENCE ON TIMING WITH SFC RIDGE ONLY PUSHING INTO W MN
BY 00Z.
KMSP...EXPECT CIGS TO REMAIN AOA OVC018 THRU THE MRNG. MAY SEE CIGS
GO BKN020 DRNG THE AFTN. SFC WNDS WNW AOB 10 KTS BCMG SW OVERNIGHT.
/OUTLOOK FOR KMSP/
SUN...VFR. WINDS SSE 5-10 KTS.
MON...MVFR. WINDS NW 15 TO 20 KTS.
TUE...VFR. WINDS WSW 10 TO 15 KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
BORGHOFF/BAP
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
427 AM CST SAT DEC 29 2012
.DISCUSSION...
.SHORT TERM...TODAY THROUGH MONDAY NIGHT.
STRATUS HAS REDEVELOPED ACROSS ALL OF MN AND WI OVERNIGHT WITH
ONLY SMALL SIGNS OF ERODING OVER FAR WRN MN EARLY THIS MORNING.
AREAS OF FREEZING FOG HAVE ALSO FORMED WITH SOME VISIBILITY
RESTRICTIONS DOWN TO 1/4 MILE. BECAUSE THE DGZ IS SO LOW AND
SATURATED...HAVE ALSO SEEN SEVERAL OBS REPORTING FLURRIES OR LIGHT
SNOW SHOWERS.
CONFIDENCE IS QUITE LOW WITH RESPECT TO TIMING THE CLOUD
DISSIPATION TODAY. NAM AND RAP ARE MOST PESSIMISTIC KEEPING LOW
CLOUDS IN THROUGH THE AFTERNOON. GFS AND LAMP ARE A LITTLE MORE
OPTIMISTIC WITH CLEARING THIS AFTERNOON. GIVEN THE TIME OF YEAR
AND HOW SOLID IT LOOKS ON SATELLITE...AM LEANING TOWARD THE MORE
PESSIMISTIC SOLUTION. AS A RESULT OF THE WIDESPREAD
STRATUS...TEMPERATURES REMAINED A BIT WARMER THAN ANTICIPATED
OVERNIGHT AND AS OF 4 AM ARE NEAR FORECAST HIGHS FOR TODAY. LITTLE
DIURNAL CLIMB EXPECTED THOUGH DUE TO SAID CLOUDS AND WEAK CAA SO
STILL FORECASTING HIGHS IN THE TEENS.
CLEARING SHOULD ARRIVE TONIGHT ACCORDING TO ALL AVAILABLE
GUIDANCE. THERE IS SOME CONCERN HOWEVER THAT IF THEY DO NOT
DISSIPATE THIS AFTERNOON THEY MAY STICK AROUND THROUGH TONIGHT AS
THE INVERSION INTENSIFIES. ASSUMING THE GUIDANCE IS RIGHT...
TONIGHT SHOULD BE A COLD ONE AS A RIDGE AXIS SETTLES OVERHEAD.
LOWS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO ARE EXPECTED.
LOW PRESSURE WILL ZIP ACROSS SOUTHERN CANADA SUNDAY WITH A COLD
FRONT ARRIVING SUNDAY EVENING. WAA AHEAD OF THIS SYSTEM WILL BRING
A QUICK REBOUND OF TEMPS BACK INTO THE 20S. COULD SEE SOME
FLURRIES ACROSS CNTRL MN AND WI WHERE MOISTURE DEPTH AND FORCING
SHOULD BE GREATER...OTHERWISE THE COLD FRONT WILL BE DRY. VERY
STRONG CAA BEHIND THE FRONT WILL BRING STEADY OR FALLING TEMPS
INTO THE SINGLE DIGITS COME MONDAY AS 925 MB TEMPS CRASH TO -18C.
A RIDGE WILL SETTLE OVERHEAD MONDAY NIGHT. CLEAR SKIES...LIGHT
WINDS...AND A VERY COLD AIRMASS SHOULD ALLOW MOST PLACES TO
PLUMMET INTO THE TEENS BELOW ZERO...AND PERHAPS TO 20 BELOW IN
SOME OF THE COLDEST LOCATIONS. THE PLACEMENT OF THE RIDGE WILL BE
CRUCIAL. GFS HAS BEEN FURTHEST EAST WITH IT AND BRINGS WAA ACROSS
WRN MN LATE MONDAY NIGHT WITH THE COLDEST TEMPS ACROSS WI.
NAM/DGEX/GEM/ECMWF HAVE BEEN A BIT FURTHER WEST WITH THE CORE OF
THE COLD AIR. INTERESTINGLY...THE 29.00Z NAM/GEM...28.18Z
DGEX...AND 28.12Z EURO HAD GOOD CONSISTENCY WITH TEMPS RANGING
FROM NEAR -22F OVER ERN CHIPPEWA CO MN...TO ABOUT -5F IN THE TWIN
CITIES METRO. LEANED TOWARD THOSE RAW SOLUTIONS FOR THIS FORECAST
AND DISCARDED THE GFS. 29.00Z EURO CAME IN A TAD WARMER. WITH
TEMPS SUCH AS THESE...IT WON/T TAKE MUCH TO BRING THE WIND CHILL
WAY DOWN. EVEN A 5 KT WIND WOULD RESULT IN -20 TO -30F.
.LONG TERM...NEW YEARS DAY THROUGH FRIDAY.
RIDGE SETTLES SOUTH WITH RETURN FLOW ALLOWING ANOTHER QUICK
REBOUND OF TEMPS BACK INTO THE TEENS ON NEW YEARS DAY.
ANOTHER SYSTEM ZIPPING ACROSS THE NORTHERN GREAT LAKES WILL BRING
A WEAK FRONT SOUTH ON TUESDAY. MEANWHILE...YET ANOTHER SYSTEM
WILL DIVE SOUTHEAST INTO THE NORTHERN PLAINS TUESDAY NIGHT AND
BRING A STRONG COLD FRONT THROUGH WEDNESDAY OR WEDNESDAY EVENING.
THIS SYSTEM MAY BRING A BIT OF LIGHT SNOW BEFORE ANOTHER SURGE OF
ARCTIC AIR SPILLS SOUTH. COULD SEE A SIMILAR SCENARIO FROM EARLIER
IN THE WEEK WITH LOWS IN THE TEENS BELOW ZERO THURSDAY MORNING AND
HIGHS IN THE SINGLE DIGITS. THIS ONE HAS A LITTLE MORE UNCERTAINTY
WITH THE POTENTIAL FOR CLOUDS TO LINGER SO DID NOT GO TOO CRAZY
WITH TEMPERATURES YET.
&&
.AVIATION.../06Z TAF ISSUANCE/
CONDITIONS VARY SIGNIFICANTLY AT TAF ISSUANCE TIME...RANGING FROM
LIFR AT AXN...RWF...RNH...TO MVFR AT STC AND VFR AT MSP AND EAU.
BREAKS IN MID LEVEL CLOUD COVER HAVE FACILITATED REDEVELOPMENT OF
LOW CLOUDS AND FREEZING FOG...MOST WIDESPREAD ACROSS WRN MN UNDER
THE SURFACE RIDGE AXIS AND MORE PATCHY FURTHER EAST. THINK THE LOW
CLOUDS WILL SPREAD EAST OVERNIGHT AND IMPACT MSP AND EAU BETWEEN
07-09Z. CONDITIONS SHOULD IMPROVE GRADUALLY ON SATURDAY...BUT
CONFIDENCE REMAINS RATHER LOW WITH RESPECT TO TIMING THE RETURN
OF VFR CONDITIONS. CLOUDS MAY PERSIST A BIT LONGER THAN CURRENTLY
ADVERTISED.
KMSP...MSP IS CURRENTLY LOCATED IN A VFR HOLE SURROUNDED BY MVFR
CIGS. SATELLITE INDICATES THIS HOLE IS BEGINNING TO FILL AND MVFR
CIGS SHOULD BEGIN IMPACTING THE TERMINAL BY 08Z. IMPROVING
CONDITIONS ARE EXPECTED SATURDAY MORNING WITH VFR BY AFTERNOON.
/OUTLOOK FOR KMSP/
SUN...VFR. WINDS SSE 5-10 KTS.
MON...VFR. WINDS NW 5-10 KTS.
TUE...VFR. WINDS WSW 5 KTS.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
BORGHOFF
AREA FORECAST DISCUSSION
NWS BINGHAMTON NY
1036 AM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE WILL TRACK ACROSS THE MID ATLANTIC REGION THIS AFTERNOON,
SPREADING 3 TO 7 INCHES OF SNOW ACROSS MUCH OF UPSTATE NY AND
NORTHEAST PA. A NORTHWEST FLOW BEHIND THIS LOW PRESSURE SYSTEM WILL
GENERATE LAKE EFFECT SNOW SHOWERS FOR UPSTATE NEW YORK FOR THE
REST OF THE WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
IR AND WATER VAPOR IMAGERY SHOW AN IMPRESSIVE UPPER LEVEL WAVE
MOVING INTO WRN PA/NY W VA. COOLING CLOUD TOPS CONTINUE ACRS NY
AND NRN PA ASSCTD WITHE STRONG MID-LEVEL ASCENT. THE TROP PRESSURE
ON THE 1.5 PV SURFACE WAS DOWN TO 560 MB AS PER THE LATEST RAP IN
THE ERN OH VLLY. THIS MATCHED VERY WELL WITH THE SATELLITE DEPICTION
OF THE CENTER OF THE UPPER LEVEL CRLCN. THIS UPPER LEVEL WAVE WILL
MOVE INTO ERN NY BY 2-3Z AS ANOTHER UPR LVL PV INTRUSION...DOWN
TO 490 MB...DEVELOPS OFF THE COAST INDICATIVE OF THE TRANSFER OF THE
MAIN ENERGY TO THE DEVELOPING COASTAL LOW. PRESENTLY THE UPPER
LEVEL WAVE IN THE ERN OH VLLY HAD A SFC REFLECTION MOVING INTO WRN PA
THAT WILL EVENTUALLY GET SWALLOWED UP BY THE DEEPENING SFC CYCLONE
OFF THE E COAST BY THIS EVENING. THIS LOW WILL BE WELL EAST OF THE NJ
COAST BY 00Z. BELIEVE THE HEAVIEST SNOW WILL TAPER DOWN BY LATE
AFTERNOON AS THE MAIN LIFTING WITH THIS UPPER LEVEL WAVE SHIFTS TO
THE EAST. LIGHTER SNOWS WILL PERSIST INTO THE EARLY EVENING.
THE SATELLITE CONTS TO REVEAL THAT THE DEEPER MOISTURE REMAINS OFF
THE EAST COAST AND WAS THE MAIN REASON WHY THIS STORM LIKELY WON/T
BECOME A MAJOR EVENT FOR OUR AREA AS THE UPPER LEVEL WAVE JUST IS
NOT TAPPING INTO THE DEEPER MOISTURE OFFSHORE FOR OUR AREA.
BELIEVE MOST OF OUR FORECAST AREA SEES BETWEEN 4 AND 7
INCHES...WITH BETWEEN 3 AND 6 INCHES IN SCRANTON/WILKES BARRE
AREA/POCONOS WHERE CURRENT SNOW REPORTS SHOW THAN LESS THAN 1
INCH HAS OCCURRED THERE SO FAR. THE BULK OF THEIR SNOW WILL COME
WITH A SIGNIFICANT BAND OF HEAVIER SNOW MOVING INTO SC PA ATTM.
WILL CONTINUE WITH WINTER WEATHER ADVISORIES ALL ZONES. IF SNOW
REPORTS APPROACH 5-6 ICNHES BY 1 PM AND RADAR TRENDS CONTINUES TO
SHOW REDEVELOPMENT TO THE SOUTHWEST MAY HAVE TO UPGRADE TO WINTER
STORM WARNING IN SOME AREAS. DON/T THINK THIS WILL BE THE
CASE...BUT IT COULD COME CLOSE SOME AREAS IN C NY/NRN PA. LATEST
12Z NAM SNOWFALL PROJECTIONS SHOW A SOLID 4-6 INCHES SUPPORTING ADVY.
MOST OF OUR SNOWFALL REPORTS IN NY AND FAR NRN PA ARE 2-3 INCHES
WITH THE SCRANTON AREA LESS THAN 1 INCH AS STATED ABOVE.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
CONTINUING WW ADVISORY TODAY. LATEST MODEL PROGS SUGGEST A VERY
WIDESPREAD SWATH OF 3 TO 5 INCHES OF SNOW ACROSS FA, WITH
POTENTIAL FOR 6-7 INCHES OVER THE VERY HIGH TERRAIN OF THE POCONOS
AND WESTERN CATSKILLS.
THERE ARE CONCERNS WHICH COULD HINDER SNOWFALL AMOUNTS, INCLUDING
RELATIVELY SHALLOW MOIST LAYER AND FAST MOVEMENT OF SYSTEM.
HOWEVER ATMOSPHERIC DYNAMICS ARE VERY STRONG AND CONFIDENCE IS NOW
HIGH FOR ADVISORY ACCUMS. OF NOTE IS IMPRESSIVE PV INTRUSION
VISIBLE DOWN TO 600-500MB ON NAM.
STORM WILL PULL OUT THIS EVENING, WITH A COLD NORTHWEST FLOW
GENERATING LAKE BANDS OFF OF ONTARIO. PRE-EXISTING LL MOIST LAYER
COMBINED WITH LAKE INDUCED INSTABILITY (850MB TEMPS -10C TO -12C)
WILL BE SOMEWHAT TEMPERED BY SHEAR IN THE LOW LAYERS. EXPECT AN
INCH OR TWO OF LAKE SNOW BY SUNDAY AFTERNOON, WHEN INVERSION
BUILDS DOWN AND HIGH PRESSURE STARTS TO LOCK IN.
SUNDAY NIGHT INTO MONDAY...HIGH PRESSURE, FAIR WEATHER, AND A
BRIEF MODERATION IN TEMPERATURES BACK TOWARD SEASONAL NORMS. SHORT
WAVE APPROACHES MONDAY NIGHT, GENERATING LIGHT SNOW SHOWERS.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
2 AM UPDATE...
VRY FEW CHGS NEEDED TO LONG TERM AS IT APPEARS TO BE A PROLONGED
PD OF LK EFFECT ACTIVITY EACH DAY UNDER COLD NW FLOW DROPPING
SOUTH OUT OF CANADA. CDFNT LOOKS TO MV THRU ON THURSDAY, THUS HV
LOWERED MIN TEMPS FOR FRI MRNG AND AGAIN FOR MAXES ON FRIDAY.
SINGLE DIGITS APPEAR LKLY FOR FRIDAY MORNING WITH PERHAPS SOME
LOCALES DROPPING BLO ZERO.
PREV DISCO BLO...
1 PM UPDATE...
FOLLOWED HPC GUIDANCE. A COLD SPELL WITH BELOW NORMAL TEMPERATURES
BUT NO MAJOR CYCLONES AND HEAVY SNOW. MOSTLY LAKE EFFECT. MONDAY
NIGHT STARTS WITH A COLD FRONT BRINGING A REINFORCING SHOT OF COLD
AIR. LIGHT SNOW WITH THE FRONT THEN LAKE EFFECT. THE REST OF THE
EXTENDED MORE OF THE SAME. ANOTHER COLD FRONT THU OR FRI BUT AGAIN
NOT TAPPING ANY ATLANTIC OR GULF MOISTURE. COLDEST DAY OF WEEK
FRIDAY WITH LOWS IN SINGLE DIGITS.
&&
.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
12Z UPDATE...
MVFR AND IFR EXPECTED MAJORITY OF THE DAY AS SNOW MOVES INTO THE
REGION. EXPECT IFR CONDS TO MOVE INTO KSYR AND KRME AFTER 14Z AND
BY 1230Z AT KBGM. ELSEWHERE REMAINDER OF TERMINALS SHOULD START
OFF THE TAF VALID TIME AT IFR. IFR CONDS CONTINUE INTO THE EVENING
HOURS AS LAKE EFFECT SNOW SHOWERS WILL KICK IN ON THE BACKSIDE OF
THE DEPARTING SYSTEM. FURTHER SOUTH AWAY FROM THE LAKES, KELM, KBGM
AND KAVP EXPECTED TO GO MVFR AFTER 06Z.
WINDS LIGHT AND VARIABLE EARLY ON THEN BECOME MORE SOUTHEASTERLY AROUND
5KTS THROUGHOUT THE MORNING HOURS THEN BECOMING NORTHWEST AFTER
22Z AND INCREASING TO NEAR 10KTS.
OUTLOOK...
SUN THROUGH TUE...MVFR/IFR POSSIBLE FOR CNY TERMINALS...IN LAKE
EFFECT SN ACTIVITY.
WED...VFR. SOME MVFR-IFR -SHSN KSYR/KRME.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...WINTER WEATHER ADVISORY UNTIL 9 PM EST THIS EVENING FOR
PAZ038>040-043-044-047-048-072.
NY...WINTER WEATHER ADVISORY UNTIL 9 PM EST THIS EVENING FOR NYZ009-
015>018-022>025-036-037-044>046-055>057-062.
&&
$$
SYNOPSIS...DJP/DJN
NEAR TERM...DJN
SHORT TERM...DJP
LONG TERM...PVN/TAC
AVIATION...PVN
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
639 AM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE MOVING NORTHEAST OFF THE COAST TODAY WILL BRING RAIN
THROUGH THE FIRST HALF OF TODAY. THIS LOW WILL INTENSIFY AS IT
MOVES AWAY SUNDAY...BRINGING GUSTY NORTHWEST WINDS AND MUCH
COOLER TEMPERATURES. HIGH PRESSURE BUILDS ACROSS THE AREA
MONDAY...BEFORE A COLD FRONT CROSSES THE CAROLINAS TUESDAY
BRINGING A CHANCE FOR SHOWERS. THIS FRONT STALLS SOUTH OF THE AREA
WEDNESDAY...AND A LOW PRESSURE MAY DEVELOP ALONG THIS AND BRING
MORE RAIN TO THE REGION LATE IN THE WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM SATURDAY...EVERY FORECAST MODEL INCLUDING THE RUC AND
HRRR ARE STRUGGLING BADLY WITH THE RAPIDLY EVOLVING LOW PRESSURE
NEAR GEORGETOWN. MESONET AND BUOY DATA HAS BEEN INVALUABLE IN
LOCATING THE COASTAL FRONT THAT EXTENDS FROM 10 MILES EAST OF
WRIGHTSVILLE BEACH...ACROSS KURE BEACH TO NEAR SOUTHPORT...TO ABOUT
15 MILES EAST OF MYRTLE BEACH...TO NEAR THE MOUTH OF THE SANTEE
RIVER SOUTH OF GEORGETOWN. THE MESONET SITE ON BALD HEAD ISLAND HAS
A SOUTH WIND WITH 61 DEGREES...WHILE BOLIVIA IN CENTRAL BRUNSWICK
COUNTY HAS A NORTH WIND AND 47 DEGREES. TEMPERATURES HAVE BEEN
FALLING IN WILMINGTON FOR THE PAST 90 MINUTES AS STRONG PRESSURE
FALLS AND FRONTOGENETIC PROCESSES ARE PACKING TEMPERATURE ISOTHERMS
TIGHTER NEAR THE FRONT. THE FEW LUCKY LOCATIONS ON THE COAST THAT
HAVE GOTTEN INTO THE SUBTROPICAL AIRMASS WILL SEE THEIR WINDS WHIP
AROUND TO THE NORTHWEST WITHIN THE NEXT 60-90 MINUTES AS THE LOW
RACES UP THE COAST AND THE COLDER AIR SURGES BACK OFFSHORE. RADAR
SHOWS THE BACK EDGE OF THE MODERATE TO OCCASIONALLY HEAVY SHOWER
ACTIVITY WILL BE APPROACHING DARLINGTON AND FLORENCE IN LESS THAN
TWO HOURS...AND MAY BE OFF THE COAST BY 10-11 AM. THIS IS EVEN
FASTER THAN MY PREVIOUS FORECAST UPDATE SHOWED.
IN ADDITION TO ALL THE MANUAL ADJUSTMENTS TO THE FORECAST MENTIONED
ABOVE...HIGH TEMPERATURES WILL PROBABLY NOT BE ABLE TO REACH THE 60S
ALONG ANY PORTION OF THE SOUTH CAROLINA COAST OR ANY NC COASTAL
LOCATIONS ASIDE FROM BALD HEAD ISLAND AND SOUTHPORT...SO I HAVE
ADJUSTED HIGHS DOWN SEVERAL DEGREES INTO THE UPPER 50S WHICH IS
ITSELF CONTINGENT ON ENOUGH SUNSHINE DEVELOPING THIS AFTERNOON TO
OFFSET THE COLD ADVECTION BEHIND THE DEPARTING LOW. PREVIOUS
DISCUSSION FROM 300 AM FOLLOWS...
A COMPLEX SURFACE PATTERN THIS MORNING CONSISTS OF LOW PRESSURE JUST
EAST OF PENSACOLA WITH A SECOND CENTER NORTH OF KNOXVILLE. A COASTAL
FRONT 30-40 MILES EAST OF THE CAROLINA COAST EXTENDS BACK INTO THE
LOW NEAR PENSACOLA. THIS FLORIDA LOW IS QUICKLY BECOMING THE
DOMINANT FEATURE AND WILL RAPIDLY MOVE NORTHEAST ALONG THE FRONT
THIS MORNING...CROSSING OUR PORTION OF THE EASTERN CAROLINAS SHORTLY
AFTER DAYBREAK. IN THE UPPER LEVELS TWO SHORTWAVES ARE ROUNDING THE
BASE OF THE LONGWAVE TROUGH IN THE PLAINS STATES. ONE DISTURBANCE
WILL PASS JUST NORTH OF THE CAROLINAS THIS MORNING...WHILE THE
SECOND WILL FOLLOW A PATH ACROSS THE CAROLINAS TONIGHT.
MOIST ISENTROPIC LIFT ALONG THE 305K-310K SURFACES (8000-14000 FT
AGL) SHOULD RESULT IN WIDESPREAD RAIN THROUGH MID-MORNING. NEAR THE
COAST LAPSE RATES ALOFT WILL STEEPEN SUFFICIENTLY TO GENERATE
200-500 J/KG OF ELEVATED CAPE WHICH MAY RESULT IN ISOLATED
THUNDERSTORMS TOO. COMPARED TO PREVIOUS FORECASTS...00Z SYNOPTIC
MODELS PLUS MORE RECENT MESOSCALE MODEL RUNS SHOW RAIN RAPIDLY
CLEARING OUT FROM WEST TO EAST THIS MORNING. PRECIPITATION MAY SHUT
DOWN WEST OF I-95 BY 930 AM...AND MAY GET OFF THE COAST BY 11 AM. I
WILL BUILD A LITTLE FUDGE FACTOR INTO MY FORECAST POPS TO ACCOUNT
FOR UNCERTAINTY BUT AM STILL INDICATING DRY CONDITIONS THIS
AFTERNOON WITH SKIES BECOMING MOSTLY CLEAR TO PARTLY CLOUDY.
POST-FRONTAL MOISTURE PLUS COLD MID-LEVEL AIR ASSOCIATED WITH THE
SECOND UPPER DISTURBANCE THIS EVENING COULD RESULT IN A TEMPORARY
INCREASE IN CLOUDINESS...BUT ISENTROPIC DOWNGLIDE THROUGH THE MOIST
LAYER ON THE 285K SURFACE SHOULD PRECLUDE ANY PRECIPITATION.
TEMPERATURES PROBABLY HAVE THE LARGEST UNCERTAINTY WITH TODAY`S
FORECAST. THE COASTAL FRONT WILL SEPARATE SUBTROPICAL AIR OFFSHORE
FROM A COOL WEDGE-LIKE AIRMASS INLAND. IF THIS BOUNDARY SNEAKS
FARTHER ONSHORE THAN EXPECTED WE SHOULD HAVE A TEMPERATURE BUST FOR
THE BEACH TOWNS PLUS WILMINGTON. (2 AM TEMPERATURES ARE ALREADY IN
THE UPPER 60S OUT AT THE FRYING PAN SHOALS BUOY!) FARTHER INLAND OUR
TEMPERATURE FORECAST CONFIDENCE IS A LITTLE BETTER SINCE THERE IS A
MUCH SMALLER CHANCE OF WARM AIR SNEAKING IN AHEAD OF THE LOW. EVEN
WITH SOME SUNSHINE THIS AFTERNOON TEMPERATURES WILL STRUGGLE INTO
THE MID TO UPPER 50S INLAND WITH A FEW LOWER 60S AT THE COAST. COLD
ADVECTION ON BREEZY WEST WINDS TONIGHT SHOULD DROP LOWS INTO THE
LOWER 30S INLAND AND MID 30S AT THE COAST.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 300 AM SATURDAY...CLEAR AND COLD SUNDAY AS HIGH PRESSURE
BUILDS ACROSS THE CAROLINAS BEHIND A DEPARTING COLD FRONT. STRONG
PRESSURE GRADIENT BETWEEN ADVANCING HIGH AND DEPARTING SYSTEM IN THE
CANADIAN MARITIMES CREATES GUSTY NW WINDS THROUGH THE DAY. ALTHOUGH
MID-LEVEL CAA PERSISTS THROUGH THE DAY...1000-850MB THICKNESSES
ACTUALLY INCREASE AS SURFACE HIGH BUILDS EASTWARD. THIS WILL HELP
MODIFY TEMPS SOMEWHAT...AND HAVE BUMPED SUNDAY`S HIGHS SLIGHTLY
ALTHOUGH REMAINING WELL BELOW CLIMO...UPPER 40S TO NEAR 50. IT WILL
FEEL EVEN COLDER THANKS TO THE BITING WINDS THOUGH...AND WIND CHILLS
WILL ECLIPSE 40 DEGREES ONLY FOR A FEW HOURS. HIGH PRESSURE SITS
OVERHEAD SUNDAY NIGHT AND WITH A VERY DRY COLUMN IN PLACE (PWATS
LESS THAN ONE-QUARTER INCH)...VERY GOOD RADIATIONAL COOLING WILL
OCCUR. EXPECT MINS SUNDAY NIGHT TO BOTTOM OUT IN THE MID 20S...LOW
20S IN THE TYPICALLY COLDEST SPOTS...BUT AROUND 30 AT THE IMMEDIATE
COAST.
HIGH PRESSURE DRIFTS OFFSHORE MONDAY AND WARMER RETURN FLOW AIR
WORKS BACK INTO THE AREA. THIS HELPS TEMPS RISE TO AROUND
CLIMO...BUT ALSO INCREASES MOISTURE AND CLOUD COVER. DO NOT
ANTICIPATE MUCH IN THE WAY OF SHOWERS MONDAY...AND WHAT DOES OCCUR
WILL BE OVERNIGHT INTO TUESDAY MORNING AHEAD OF AN ADVANCING COLD
FRONT. TIME HEIGHTS SHOW CONSIDERABLE DRY AIR PERSISTING UNTIL WELL
AFTER DARK WHICH SHOULD INHIBIT ANY RAINFALL FOR MOST OF THE
PERIOD...BUT SOME MID-LEVEL LIFT SHOULD SQUEEZE OUT A FEW
SHOWERS...MOSTLY ACROSS NW PORTIONS OF THE CWA...BEFORE DAYBREAK
TUESDAY. WILL CONTINUE INHERITED SCHC POP FOR THAT AREA OVERNIGHT.
MINS WILL BE HELD IN CHECK THANKS TO THE CLOUD COVER AND SOUTHERLY
WINDS...FALLING ONLY TO AROUND 40 MONDAY NIGHT.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 300 AM SATURDAY...TWO WEAK SYSTEMS TO AFFECT THE AREA DURING
THE EXTENDED...ALONG WITH CONTINUED BELOW-CLIMO TEMPS THROUGH THE
WEEK.
GUIDANCE HAS COME INTO MUCH BETTER AGREEMENT IN THE EVOLUTION OF THE
MID-LEVEL PATTERN THROUGH NEXT WEEK. THE WEEK WILL BE DOMINATED BY
SPLIT FLOW AT 500MB...WITH A LARGE CUTOFF LOW ANCHORED ACROSS THE
SOUTHWEST THROUGH EARLY THURSDAY. THE SPLIT FLOW KEEPS SYSTEMS WEAK
AND MOVING QUICKLY ACROSS THE NATION...WHILE MARGINAL CONFLUENCE
ACROSS THE EAST ALLOWS FOR ARCTIC AIR TO INTRUDE ACROSS THE
NORTH...MODIFYING SLIGHTLY THROUGH THE CAROLINAS.
A NORTHERN STREAM LOW DRAPES A COLD FRONT ACROSS THE AREA ON TUESDAY
BRINGING WITH IT A CHANCE FOR SHOWERS AS IT SINKS SOUTHWARD THROUGH
THE DAY. LITTLE OF ANY UPPER SUPPORT IS EVIDENT IN THE
GUIDANCE...AND MOISTURE FLUX AHEAD OF THE FRONT IS LIMITED...SO NOT
A BIG QPF MAKER FOR THE REGION. FRONT STALLS SOUTH ON WEDNESDAY AND
MUCH OF THE DAY WILL BE DRY...ALBEIT WITH CONTINUED MID/UPPER
CLOUDS. THURSDAY IS A MORE INTERESTING DAY AS THE SOUTHWEST CLOSED
LOW FINALLY OPENS AND EJECTS INTO THE FLOW...RACING EAST TO BECOME
OFFSHORE BY FRIDAY MORNING. AT THE SAME TIME...A NORTHERN STREAM
SHORTWAVE MAY TRY TO PHASE WITH THIS FEATURE TO CREATE A COASTAL LOW
ALONG THE RESIDUAL FRONT AND BRING MORE SIGNIFICANT RAINFALL TO THE
REGION. ATTM...DUE TO THE SPEED OF THE FLOW ALOFT...THINK PHASING IS
A MUCH LESS LIKELY SOLUTION...AND BEING THIS FAR OUT IN TIME WILL
SHOW CHC POP THURSDAY WITH A WEAKER AND FASTER LOW MOVING AWAY BY
FRIDAY MORNING...WITH COLD AND DRY CONDITIONS EXPECTED BEHIND IT.
TEMPS THROUGH THE PERIOD WILL BE SLIGHTLY BELOW CLIMO FOR
HIGHS...AND SLIGHTLY ABOVE FOR LOWS WITH CLOUDS/RAIN INHIBITING
GREAT NOCTURNAL COOLING.
&&
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
AS OF 12Z...PRETTY CRAZY TEMPERATURE GRADIENT BETWEEN ILM AND BALD
HEAD ISLAND...43F VERSES 63F. GOOD ISENTROPIC LIFT ALONG THE WARM
FRONT WILL GIVE US MVFR/IFR CONDITIONS IN MODERATE TO HEAVY RAIN FOR
THE NEXT FEW HOURS. A RUMBLE OF THUNDER IS POSSIBLE AT THE MYRTLES
WHERE SOME INSTABILITY WILL RESIDE. NORTHEAST WINDS WILL HANG IN AT
THE NORTHERN TERMINALS THROUGH AT LEAST 14Z...AS THE WEDGE TRIES TO
DIG IN. A BRIEF SHIFT TO THE SOUTH IS POSSIBLE IF THE WARM FRONT
MANAGES TO MOVE NORTHWARD. COLD FRONT AND APPROACHING LOW WILL
WHISKS THEIR WAY THROUGH THE REGION BY LATE MORNING...WITH A
NOTICEABLE WIND SHIFT TO THE WEST. CONDITIONS IMPROVING TO VFR THIS
AFTERNOON WITH GUSTY WEST WINDS.
EXTENDED OUTLOOK...VFR CONDITIONS EXPECTED SUNDAY AND MONDAY. CHANCE
FOR RAIN TUESDAY. VFR EXPECTED WEDNESDAY.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM SATURDAY...MESONET AND BUOY DATA HAS BEEN INVALUABLE IN
LOCATING THE FRONT THIS MORNING WHICH CURRENTLY EXTENDS FROM 10
MILES EAST OF WRIGHTSVILLE BEACH...ACROSS KURE BEACH TO NEAR
SOUTHPORT...TO ABOUT 15 MILES EAST OF MYRTLE BEACH...AND TO NEAR THE
MOUTH OF THE SANTEE RIVER SOUTH OF GEORGETOWN. EAST OF THIS BOUNDARY
WINDS ARE 25 TO 30 KNOTS FROM THE SOUTH...WHILE TO THE WEST OF THE
BOUNDARY A SLIGHTLY WEAKER NORTHERLY WIND IS BLOWING. LOW PRESSURE
HAS RACED NORTH FROM FLORIDA THIS MORNING AND IS ANALYZED NEAR THE
SANTEE RIVER CURRENTLY. THE LOW SHOULD MOVE TO NEAR CAPE FEAR BY 730
AM...AND THEN EAST OF SURF CITY SHORTLY AFTER 800 AM. AS THE LOW
PUSHES NORTH OF THE AREA THE COLDER AIR WILL SURGE BACK OUT ACROSS
THE COASTAL WATERS WITH NORTHWESTERLY WINDS REPLACING ANY REMAINING
WARM SOUTHERLY WINDS. THIS IS AN EXTREMELY DYNAMIC SITUATION THAT NO
COMPUTER MODEL IS CAPTURING VERY WELL. SHOWERS AND EMBEDDED
THUNDERSTORMS WILL CONTINUE THROUGH MID MORNING BEFORE DRIER AIR
ARRIVES FROM THE WEST AND ERODES THE PRECIPITATION. SEAS SHOULD
SPIKE UP BY SEVERAL FEET IN THE NEXT HOUR OR TWO DUE TO THE STRONG
(NEARLY GALE-FORCE) WINDS OFFSHORE. PREVIOUS DISCUSSION FROM 300 AM
FOLLOWS...
A COASTAL FRONT ABOUT 30-40 MILES OUT FROM THE COAST WILL MOVE VERY
CLOSE TO THE BEACHES THIS MORNING... POTENTIALLY MAKING IT ONSHORE
AROUND CAPE FEAR AND NEAR GEORGETOWN. LOW PRESSURE OVER NORTHERN
FLORIDA WILL RACE NORTHEAST ALONG THIS FRONT...MOVING OVER THE
CAROLINA COASTLINE ABOUT AN HOUR AFTER SUNRISE. AFTER THIS LOW MOVES
NORTH OF THE AREA THE FRONT WILL BE PUSHED BACK OFFSHORE WITH COOLER
WESTERLY WINDS EXPECTED FOR THE REMAINDER OF TODAY. WINDS WILL VEER
NORTHWESTERLY AROUND MIDNIGHT TONIGHT AS A RENEWED SURGE OF COLD AIR
BLOWS ACROSS THE CAROLINAS.
SMALL CRAFT ADVISORIES WILL REMAIN POSTED FOR WINDS AND FOR LARGE
SEAS EXPECTED TO DEVELOP. NEARSHORE WIND SPEEDS ALONE WOULD PROBABLY
NOT BUILD SEAS TO 6 FEET...BUT MUCH STRONGER WINDS BLOWING GALE
FORCE OR STRONGER OVER THE GULF STREAM WILL PRODUCE LARGE SEAS THAT
WILL SPREAD INTO THE AREA SHORTLY AFTER DAYBREAK. SEAS COULD BUILD
TO 7-9 FEET WITHIN 20 MILES OF SHORE...ESPECIALLY NEAR FRYING PAN
SHOALS. SEAS WILL SHIFT TO MORE SHORT-PERIOD WIND WAVES WITH THE
OFFSHORE WINDS EXPECTED THIS AFTERNOON INTO TONIGHT.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 300 AM SATURDAY...GUSTY NW WINDS BEHIND A DEPARTING COLD FRONT
WILL BE 20-25 KTS EARLY SUNDAY...AND A SMALL CRAFT ADVISORY WILL BE
ONGOING AT THE START OF THE PERIOD. THESE WINDS WILL EASE RATHER
QUICKLY HOWEVER...AND ANY ADVISORIES WILL EXPIRE SUNDAY AFTN. AS
HIGH PRESSURE BUILDS EAST TOWARDS...AND THEN OVER...THE WATERS
SUNDAY NIGHT AND MONDAY WINDS DROP TO 10 KTS OR LESS FROM THE
NORTH...BEFORE BACKING TO THE SW AT AROUND 10 KTS LATE MONDAY AND
THROUGH THE END OF THE PERIOD. SEAS WILL BE HIGHEST EARLY SUNDAY
WHEN THE GUSTY NW WINDS HELP DRIVE THEM TO 3-5 FT. THE COMBINATION
OF DECREASING WIND SPEEDS PLUS THE NW FETCH DIRECTION QUICKLY CAUSES
SEAS TO DROP TO 1-3 FT SUNDAY NIGHT...AND THEN PERSIST AT THESE
HEIGHTS THROUGH MONDAY.
LONG TERM /TUESDAY THROUGH WEDNESDAY/...
AS OF 300 AM SATURDAY...W/SW WINDS OF 10-15 KTS START THE PERIOD AS
THE WATERS EXIST IN A PRE-FRONTAL AIRMASS. WINDS INCREASE GRADUALLY
THROUGH TUESDAY AS COLD FRONT APPROACHES FROM THE NW...BEFORE
VEERING TO THE NW BEHIND FROPA EARLY WEDNESDAY...AGAIN AT 10-15 KTS.
FRONT STALLS SOUTH OF THE WATERS DURING WEDNESDAY...SO WINDS VEER TO
THE NORTH AND REMAIN FROM THIS DIRECTION AT AROUND 10 KTS THROUGH
WED NIGHT. SEAS OF 2-3 FT EARLY TUESDAY RISE BRIEFLY TO AS MUCH AS
3-5 FT EARLY WEDNESDAY IMMEDIATELY AHEAD OF THE COLD FRONT...BEFORE
RETURNING AGAIN TO 2-3 FT BY THE END OF THE PERIOD. SEAS WILL BE
NEARLY ENTIRELY WIND-WAVE DRIVEN THROUGH THE EXTENDED.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST SUNDAY FOR
AMZ250-252-254- 256.
&&
$$
SYNOPSIS...JDW
NEAR TERM...TRA
SHORT TERM...JDW
LONG TERM...JDW
AVIATION...DL
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
946 AM EST SAT DEC 29 2012
.SYNOPSIS...
A WIDESPREAD 3 TO 5 INCH SNOWFALL WILL OCCUR TODAY. A FEW
LOCATIONS COULD GET UP TO 6 INCHES OF SNOW FROM THIS FAST-MOVING
SYSTEM. WINDS WILL TURN TO THE NORTHWEST THIS EVENING AND BECOME
GUSTY WITH SNOW SHOWERS LIKELY DOWNSTREAM OF LAKE ERIE AND IN THE
LAUREL HIGHLANDS. NEXT WEEK LOOKS QUIET WITH ONLY A COUPLE OF WEAK
WEATHER SYSTEMS PASSING BY. THE BIG STORY LATER NEXT WEEK WITH BE
THE POSSIBILITY OF VERY COLD AIR ENTERING THE STATE.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SNOW IS FALLING BASICALLY OVER ALL OF THE REGION. VERY LIGHT SNOW
REPORTED IN EASTERN LANCASTER COUNTY. HAD CALLS ABOUT WHEN WILL IT
SNOW! ADJUSTED GRIDS WITH LATEST BLENDED GUIDANCE WHICH CLIPPED
QPF AND THUS SNOWFALL IN SOUTHERN AND EASTERN AREAS. SOME AREAS IN
NORTH-CENTRAL PA SHOW 0.50 INCHES OF QPF. WITH HIGHER RATIOS A FEW
AREAS COULD TOP 6 INCHES. STILL ANTICIPATING MOST LOCATIONS WILL
STAY IN 3-6 INCH RANGE.
SATELLITE SHOWS SHARP DRY SLOT MOVING INTO SW PA. THIS FAVORS SOME
ENHANCE BANDING TO ITS NORTH AND EAST PERHAPS NORTHERN TIER IN A
FEW HOURS. WILL MONITOR ENHANCED CSI EFFECT FROM ABOUT STATE
COLLEGE NORTHWARD THIS AM AND EARLY THIS AFTERNOON. COULD PUSH UP
SNOW TOTALS A BIT TOO. BUT ECHOES ARE WEAKENING BENEATH AND JUST
AHEAD OF IT. THIS CAN BE SEEN ON RADAR IN SW PA...BUT IN ADVANCE
OF IT IS WHERE BEST CSI POTENTIAL WILL BE.
THE RAP AND HRRR SHOW SNOW PULLING OUT OF THE REGION RAPIDLY IN
THE 1 PM TO 3 PM RANGE FROM SW TO ENE. BY ABOUT 5 PM ANY
ACCUMULATING SNOW WOULD BE CONFINED TO NORTHEASTERN AREAS. MOSTLY
LIGHT SNOW AND FLURRIES AFTER 5 PM OVER MOST OF CWA. LINGERING IN
THE MOUNTAINS.
THE BAND IN VA-MD COULD CLIP SOUTHERN YORK AND LANCASTER COUNTIES
BEFORE NOON AND GET THE SNOW FALL TO INCREASE THERE. SOMETHING TO
WATCH IN EXTREME SE. THE 14Z RAP SHOWS SLIGHT ENHANCED SNOW IN
LANCASTER COUNTY AROUND 17Z.
WE HAVE ENTERED THE BEST PERIOD OF HEAVY SNOW AND WILL TRACK IN
NOWCASTS. VISIBILITIES WILL BE LOW OVER MOST OF THE REGION THROUGH
AT LEAST 1 PM AND ROADS WITH 1 TO 2 INCH RATES AT TIMES AT THEIR WORSE.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
MONITORING SNOW SHOWER AND ACCUMULATING SNOW IN SW MOUNTAINS AND
NW PA DURING THIS PERIOD. MOST OTHER AREAS TO EAST WILL SEE LITTLE
OR NOW SNOW AFTER 9 PM GIVE OR TAKE 1-3 HOURS.
PREVIOUS DISCUSSION....THE LOW DEPARTS AND
DEEPENS OFF THE EAST COAST THIS EVENING. RESIDUAL MOISTURE FROM
THE EXITING LOW...COUPLED WITH W/NW FLOW AND UPSLOPE TOPOGRAPHIC
ENHANCEMENT WILL MAKE SNOW SHOWERS ACROSS THE SNOW BELT AND IN THE
LAUREL HIGHLANDS. THESE SHOWERS SHOULD BE MAINLY LIGHT AND SHOULD
DIE DOWN SUNDAY EVENING. THOSE FAVORED/UPSLOPE LOCATIONS IN THE
LAURELS AND DOWNWIND OF THE LAKES COULD PICK UP ANOTHER INCH OR
TWO TONIGHT AND ANOTHER INCH SUNDAY MORNING BEFORE THE FLOW
BECOMES ANTICYCLONIC. THOSE VALUES SHOULD BE JUST SUB- ADVISORY
FOR THEM. BUT ALLOWING LEEWAY...THE CURRENT ADVY FOR THOSE AREAS
COULD BE EXTENDED IF NECESSARY TO COVER THE ADDITIONAL
LAKE/UPSLOPE SNOW. OTHERWISE...SUNDAY WILL BE A BREEZY BUT FAIR
DAY FOR THE REST OF THE AREA. GUSTS COULD BE INTO THE L30S IN THE
SRN MTS AND EAST...BUT NO WORRY OF WIND ADVY. MAX TEMPS ON SUNDAY
WILL BE SIMILAR TO TODAY.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
THE FLOW WILL SHIFT TO A MORE ZONAL PATTERN AS ANOTHER SYSTEM
MAKES ITS WAY TOWARD THE REGION FOR MONDAY NIGHT/NEW YEARS EVE.
THE CURRENT MODELS ARE FAIRLY CONSISTENT AND HAVE SUFFICIENT PWATS
AND LIFT FROM A JET STREAK TO CREATE SNOW SHOWERS OVER AT LEAST
THE WESTERN HALF OF THE AREA MON NIGHT AND TUES MORNING. A FEW
NORTHERN STREAM FEATURES WILL CROSS THE LOWER GREAT LAKES AROUND
MID-WEEK AND MAKE LAKE EFFECT SHOWERS. AN ARCTIC AIR MASS BEGINS
TO MOVE THROUGH SOUTHERN CANADA AND DECREASING 850MB TEMPERATURES
WILL CONTINUE THROUGH THE LATTER HALF OF THE WEEK. CURRENT RUNS
HAVE PA UNDER M16C TEMPERATURES AT 850MB FRIDAY MORNING. THE GFS
AND EC PROPAGATE ANOTHER TROUGH THROUGH PENNSYLVANIA FRIDAY.
EXPECT HIGH TEMPERATURES THIS WEEK TO BE AT OR BELOW
FREEZING...WITH HIGHS IN THE UPPER TEENS POSSIBLE BY THE END OF
NEXT WEEK. COUPLE THE LOW TEMPS WITH THE GUSTY FLOW...AND WIND
CHILLS COULD BE AN ISSUE DURING THIS TIME FRAME. LOWS THROUGH THE
LATER HALF OF THE WEEK SHOULD BE IN THE LOW TEENS.
&&
.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
THE SNOW HAS REDUCED VISIBILITIES AND CIGS ACROSS THE ENTIRE
REGION. SNOW RATES OF 1 TO 2 INCHES PER HOUR BENEATH BANDS WILL
POSE DEICING ISSUES TOO. CONDITIONS WILL REMAIN POOR THROUGH AT
LEAST 17Z TODAY.
SNOW RATES SHOULD STEADILY DIMINISH SOUTHWEST TO NORTH EAST THIS
AFTERNOON AND EVENING. VISIBILITIES SHOULD RISE TO OVER 3 MILES
LATER THIS EVENING IN MANY SOUTHERN LOCATIONS. PERHAPS VFR A FEW
HOURS BEFORE MIDNIGHT IN THE 02 TO 03Z TIME-FRAME AS THE STORM AND
SNOW LIFTS TO OUR NORTH AND EAST.
GUSTY WINDS APPEAR LIKELY OVERNIGHT TONIGHT INTO SUNDAY WITH
SCATTERED SNOW SHOWERS DEVELOPING IN THE WESTERN AND NORTHWESTERN
MTNS. NWLRY UPSLOPE FLOW WILL LIKELY KEEP FLYING CONDS AT KJST AND
KBFD MARGINAL AFTER THE STORM WITH LOW CLOUDS AND PERIODS OF
LOWERED VISIBILITIES.
MOST OTHER LOCATIONS SHOULD HAVE GENERALLY GOOD FLYING CONDITIONS SUNDAY.
OUTLOOK...
SUN...SHSN AND REDUCED FLIGHT CONDS POSSIBLE WESTERN AND NORTHERN
MTNS.
MON...NO SIG WX EXPECTED.
TUE...CFROPA POSSIBLE. SHSN REDUCED CIGS/VI`S AND GUSTY WINDS
POSS.
WED...MAINLY VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-
049>053-056>059-063>066.
&&
$$
SYNOPSIS...DANGELO/LA CORTE
NEAR TERM...GRUMM/DANGELO
SHORT TERM...GRUMM/DANGELO
LONG TERM...DANGELO/CERU
AVIATION...GRUMM/GARTNER
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
937 AM EST SAT DEC 29 2012
.SYNOPSIS...
A WIDESPREAD 3 TO 5 INCH SNOWFALL WILL OCCUR TODAY. A FEW
LOCATIONS COULD GET UP TO 6 INCHES OF SNOW FROM THIS FAST-MOVING
SYSTEM. WINDS WILL TURN TO THE NORTHWEST THIS EVENING AND BECOME
GUSTY WITH SNOW SHOWERS LIKELY DOWNSTREAM OF LAKE ERIE AND IN THE
LAUREL HIGHLANDS. NEXT WEEK LOOKS QUIET WITH ONLY A COUPLE OF WEAK
WEATHER SYSTEMS PASSING BY. THE BIG STORY LATER NEXT WEEK WITH BE
THE POSSIBILITY OF VERY COLD AIR ENTERING THE STATE.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SNOW IS FALLING BASICALLY OVER ALL OF THE REGION. VERY LIGHT SNOW
REPORTED IN EASTERN LANCASTER COUNTY. HAD CALLS ABOUT WHEN WILL IT
SNOW! ADJUSTED GRIDS WITH LATEST BLENDED GUIDANCE WHICH CLIPPED
QPF AND THUS SNOWFALL IN SOUTHERN AND EASTERN AREAS. SOME AREAS IN
NORTH-CENTRAL PA SHOW 0.50 INCHES OF QPF. WITH HIGHER RATIOS A FEW
AREAS COULD TOP 6 INCHES. STILL ANTICIPATING MOST LOCATIONS WILL
STAY IN 3-6 INCH RANGE.
SATELLITE SHOWS SHARP DRY SLOT MOVING INTO SW PA. THIS FAVORS SOME
ENHANCE BANDING TO ITS NORTH AND EAST PERHAPS NORTHERN TIER IN A
FEW HOURS. WILL MONITOR ENHANCED CSI EFFECT FROM ABOUT STATE
COLLEGE NORTHWARD THIS AM AND EARLY THIS AFTERNOON. COULD PUSH UP
SNOW TOTALS A BIT TOO. BUT ECHOES ARE WEAKENING BENEATH AND JUST
AHEAD OF IT. THIS CAN BE SEEN ON RADAR IN SW PA...BUT IN ADVANCE
OF IT IS WHERE BEST CSI POTENTIAL WILL BE.
THE RAP AND HRRR SHOW SNOW PULLING OUT OF THE REGION RAPIDLY IN
THE 1 PM TO 3 PM RANGE FROM SW TO ENE. BY ABOUT 5 PM ANY
ACCUMULATING SNOW WOULD BE CONFINED TO NORTHEASTERN AREAS. MOSTLY
LIGHT SNOW AND FLURRIES AFTER 5 PM OVER MOST OF CWA. LINGERING IN
THE MOUNTAINS.
THE BAND IN VA-MD COULD CLIP SOUTHERN YORK AND LANCASTER COUNTIES
BEFORE NOON AND GET THE SNOW FALL TO INCREASE THERE. SOMETHING TO
WATCH IN EXTREME SE. THE 14Z RAP SHOWS SLIGHT ENHANCED SNOW IN
LANCASTER COUNTY AROUND 17Z.
WE HAVE ENTERED THE BEST PERIOD OF HEAVY SNOW AND WILL TRACK IN
NOWCASTS. VISIBILITIES WILL BE LOW OVER MOST OF THE REGION THROUGH
AT LEAST 1 PM AND ROADS WITH 1 TO 2 INCH RATES AT TIMES AT THEIR WORSE.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
MONITORING SNOW SHOWER AND ACCUMULATING SNOW IN SW MOUNTAINS AND
NW PA DURING THIS PERIOD. MOST OTHER AREAS TO EAST WILL SEE LITTLE
OR NOW SNOW AFTER 9 PM GIVE OR TAKE 1-3 HOURS.
PREVIOUS DISCUSSION....THE LOW DEPARTS AND
DEEPENS OFF THE EAST COAST THIS EVENING. RESIDUAL MOISTURE FROM
THE EXITING LOW...COUPLED WITH W/NW FLOW AND UPSLOPE TOPOGRAPHIC
ENHANCEMENT WILL MAKE SNOW SHOWERS ACROSS THE SNOW BELT AND IN THE
LAUREL HIGHLANDS. THESE SHOWERS SHOULD BE MAINLY LIGHT AND SHOULD
DIE DOWN SUNDAY EVENING. THOSE FAVORED/UPSLOPE LOCATIONS IN THE
LAURELS AND DOWNWIND OF THE LAKES COULD PICK UP ANOTHER INCH OR
TWO TONIGHT AND ANOTHER INCH SUNDAY MORNING BEFORE THE FLOW
BECOMES ANTICYCLONIC. THOSE VALUES SHOULD BE JUST SUB- ADVISORY
FOR THEM. BUT ALLOWING LEEWAY...THE CURRENT ADVY FOR THOSE AREAS
COULD BE EXTENDED IF NECESSARY TO COVER THE ADDITIONAL
LAKE/UPSLOPE SNOW. OTHERWISE...SUNDAY WILL BE A BREEZY BUT FAIR
DAY FOR THE REST OF THE AREA. GUSTS COULD BE INTO THE L30S IN THE
SRN MTS AND EAST...BUT NO WORRY OF WIND ADVY. MAX TEMPS ON SUNDAY
WILL BE SIMILAR TO TODAY.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
THE FLOW WILL SHIFT TO A MORE ZONAL PATTERN AS ANOTHER SYSTEM
MAKES ITS WAY TOWARD THE REGION FOR MONDAY NIGHT/NEW YEARS EVE.
THE CURRENT MODELS ARE FAIRLY CONSISTENT AND HAVE SUFFICIENT PWATS
AND LIFT FROM A JET STREAK TO CREATE SNOW SHOWERS OVER AT LEAST
THE WESTERN HALF OF THE AREA MON NIGHT AND TUES MORNING. A FEW
NORTHERN STREAM FEATURES WILL CROSS THE LOWER GREAT LAKES AROUND
MID-WEEK AND MAKE LAKE EFFECT SHOWERS. AN ARCTIC AIR MASS BEGINS
TO MOVE THROUGH SOUTHERN CANADA AND DECREASING 850MB TEMPERATURES
WILL CONTINUE THROUGH THE LATTER HALF OF THE WEEK. CURRENT RUNS
HAVE PA UNDER M16C TEMPERATURES AT 850MB FRIDAY MORNING. THE GFS
AND EC PROPAGATE ANOTHER TROUGH THROUGH PENNSYLVANIA FRIDAY.
EXPECT HIGH TEMPERATURES THIS WEEK TO BE AT OR BELOW
FREEZING...WITH HIGHS IN THE UPPER TEENS POSSIBLE BY THE END OF
NEXT WEEK. COUPLE THE LOW TEMPS WITH THE GUSTY FLOW...AND WIND
CHILLS COULD BE AN ISSUE DURING THIS TIME FRAME. LOWS THROUGH THE
LATER HALF OF THE WEEK SHOULD BE IN THE LOW TEENS.
&&
.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
BROAD SHIELD OF SNOW COVERING WRN TWO THIRDS OF CENTRAL PA AT THIS
TIME AS WEAK SFC LOW TRACKS INTO WRN PA. SNOW OF VARYING
INTENSITIES IS PRODUCING IFR CIGS AT ALL CENTRAL AND WESTERN
AIRFIELDS. IN THE EAST...MDT CURRENTLY HAS MVFR CIGS WHILE ARE IPT
AND LNS ARE ACTUALLY VFR. SNOW...ALONG WITH REDUCED CIGS AND VSBYS
SHOULD COME BACK INTO EASTERN SITE WITHIN THE NEXT HOUR.
EXPECT STEADY SNOW TO CONTINUE INTO THE AFTERNOON HOURS WITH
GENERALLY IFR/LIFR CONDS AT ALL TAF SITES FOR SEVERAL HOURS. CONDITIONS
WILL BEGIN TO IMPROVE FROM WEST TO EAST DURING THE LATE AFTERNOON.
GUSTY WINDS APPEAR LIKELY OVERNIGHT TONIGHT INTO SUNDAY WITH
SCATTERED SNOW SHOWERS DEVELOPING IN THE WESTERN AND NORTHWESTERN
MTNS. NWLRY UPSLOPE FLOW WILL LIKELY KEEP FLYING CONDS AT KJST AND
KBFD MARGINAL AFTER THE STORM WITH LOW CLOUDS AND PERIODS OF
LOWERED VISIBILITIES.
OUTLOOK...
SUN...SHSN AND REDUCED FLIGHT CONDS POSSIBLE WESTERN AND NORTHERN
MTNS.
MON...NO SIG WX EXPECTED.
TUE...CFROPA POSSIBLE. SHSN REDUCED CIGS/VI`S AND GUSTY WINDS
POSS.
WED...MAINLY VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-
049>053-056>059-063>066.
&&
$$
SYNOPSIS...DANGELO/LA CORTE
NEAR TERM...GRUMM/DANGELO
SHORT TERM...GRUMM/DANGELO
LONG TERM...DANGELO/CERU
AVIATION...GRUMM/GARTNER
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
900 AM PST SAT DEC 29 2012
.SYNOPSIS...
INCREASING CLOUDS AND COOLER WITH LIGHT RAIN AND MOUNTAIN SNOW LIKELY
OVER AND WEST OF THE MOUNTAINS TODAY THROUGH SUNDAY AS A COLD
FRONT MOVES THROUGH THE REGION. ISOLATED THUNDERSTORMS ARE ALSO
POSSIBLE THROUGH SUNDAY AFTERNOON. GUSTY WEST WINDS WILL DEVELOP
OVER THE MOUNTAINS AND DESERTS FOR LATE SUNDAY. WEAK TO MODERATE
OFFSHORE FLOW...FAIR WEATHER AND GRADUAL WARMING TUESDAY THROUGH
MOST OF NEXT WEEK.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
THIS MORNING...SATELLITE IMAGERY SHOWS A LOW PRESSURE SYSTEM
MOVING SOUTHEAST ALONG THE CENTRAL CALIFORNIA COAST. RADAR SHOWS
MOSTLY LIGHT SHOWERS CURRENTLY MOVING THROUGH LOS ANGELES AND
NORTHERN ORANGE COUNTIES...WITH EMBEDDED ISOLATED TSTMS OVER L.A.
COUNTY. POST-FRONTAL CONVECTION CONTINUE TO MOVE INLAND FARTHER TO
THE NORTH. TIMING OF THE PRECIP FOR EXTREME SOUTHWESTERN CA
REMAINS ON TRACK...WITH SHOWERS MOVING INTO SOUTHWEST SAN
BERNARDINO COUNTY LATER THIS MORNING AND SPREADING SOUTH AND EAST
THROUGH THE AFTERNOON. THE BULK OF THE PRECIPITATION IS EXPECTED
TO FALL LATE THIS AFTERNOON AND EVENING AS THE FRONT MOVES
THROUGH...TAPERING OFF TO SHOWERS TONIGHT. SHOWERS MAY LINGER
SUNDAY INTO EARLY MONDAY AS A SECOND SHORTWAVE TROUGH MOVES DOWN
THE BACK SIDE OF THE TROUGH AND OVER SOUTHERN CA. COLD AIR ALOFT
AND MARGINALLY UNSTABLE CONDITIONS COULD CONTINUE ISOLATED
THUNDERSTORMS DURING THE DAY SUNDAY AS WELL.
NUMERICAL MODELS ARE IN GENERALLY GOOD AGREEMENT ON THE TRACK AND
TIMING OF THIS SYSTEM BUT DIFFER SOMEWHAT IN THE DETAILS...WITH
THE GFS AND NAM MODELS HAVING THE DRIER SOLUTIONS. THE PRECIP
FORECAST IS BASED ON A BLEND OF THE ECM AND SREF. RAINFALL TOTALS
FOR THIS SYSTEM WILL RANGE FROM AROUND ONE TENTH TO ONE THIRD INCH
IN THE COASTS/VALLEYS AND ONE QUARTER TO ONE HALF INCH IN THE
MOUNTAINS. LOCALLY HIGHER AMOUNTS ARE POSSIBLE IN HEAVIER SHOWERS
AND THUNDERSTORMS. LITTLE TO NO RAINFALL IS EXPECTED IN THE
DESERTS. THE SNOW LEVEL IS AROUND 4500 FT THIS MORNING...AND IS
EXPECTED TO DROP TO AROUND 4000 FT TONIGHT. SNOWFALL TOTALS WILL
BE BETWEEN 1 TO 3 INCHES ABOVE 4500 FT...WITH ISOLATED AMOUNTS TO
UP TO 4 INCHES ON THE SOUTH SLOPES OF THE SAN BERNARDINO MTNS.
IN ADDITION TO PRECIPITATION...THIS SYSTEM WILL BRING WEST WINDS
WITH GUSTS UP TO 40 MPH IN THE MTNS AND DESERTS SUNDAY AFTERNOON
AND EVENING FOLLOWING FRONTAL PASSAGE. AS THE COLD AIR MOVES IN
FROM THE NORTHWEST...HIGH TEMPERATURES THIS WEEKEND WILL BE
ANYWHERE FROM 10 TO 20 DEGREES BELOW SEASONAL AVERAGES.
WEAK OFFSHORE FLOW WILL DEVELOP FOR MONDAY MORNING AS THE LOW
PRESSURE TROUGH MOVES EAST AND SURFACE HIGH PRESSURE MOVES INTO
THE GREAT BASIN. DESPITE THE OFFSHORE FLOW...COLD AIR MOVING IN
FROM THE NORTH WILL PREVENT MUCH WARMING FROM OCCURRING SO EXPECT
TEMPERATURES TO REMAIN BELOW SEASONAL AVERAGES. BEYOND
MONDAY...THERE IS QUITE A BIT OF UNCERTAINTY IN THE FORECAST AS
MODELS CONTINUE TO BE VERY INCONSISTENT WITH THE TRACK OF ANOTHER TROUGH
FOR TUE INTO WED. THE GFS AND EC HAVE TRENDED MUCH FURTHER WEST
WITH THIS TROUGH...BRINGING IT DOWN ALONG THE CA COAST. THIS
WOULD MEAN WEAKER UPPER SUPPORT FOR THE OFFSHORE WINDS TUESDAY AND
SLIGHTLY COOLER WEATHER. BOTH MODELS EVEN SHOW SOME RAIN OFF THE
COAST...THOUGH AT THIS TIME IT IS TOO FAR WEST TO IMPACT SOUTHERN
CA. STILL EXPECTING SOME INCREASE IN THE OFFSHORE WINDS LATE
TUESDAY INTO WED AS WINDS ALOFT TURN NORTHEAST AND SURFACE
GRADIENTS TIGHTEN. WEAK OFFSHORE WINDS AND GRADUAL WARMING WILL
CONTINUE INTO THE WEEKEND WITH TEMPS NEAR TO SLIGHTLY BELOW
NORMAL. MODELS ARE STILL HINTING AT ANOTHER LOW PRESSURE SYSTEM
FOR NEXT WEEKEND...THOUGH UNCERTAINTY IS HIGH AS THERE IS LITTLE
OR NO AGREEMENT AMONG THE MODELS AT TO WHERE THE LOW/TROUGH WILL
TRACK AND HOW STRONG IT WILL BE.
&&
.AVIATION...
291550Z...COASTAL TO MOUNTAINS AREA OF EXTREME SOUTHERN
CALIFORNIA...CLOUDS CONTINUE TO INCREASE ACROSS THE AREA AND A
FEW SHOWERS ARE BEGINNING TO SHOW UP ON RADAR AND IN OBS AT A FEW
AIRPORTS. STORM SYSTEM IS ON TRACK WITH FOCUS ON ECMWF...LOCAL
WRF AND RAP IN DECENT AGREEMENT WITH FRONTAL PASSAGE AND
SHOWERS...PER TAFS...IN THE KSNA 29/2000Z TO KSAN 30/0100Z.
CEILINGS AND WINDS NOT A MAJOR ISSUE WITH CEILINGS MAYBE TEMPO TO
015 MSL AND VSBY TO 3 MI WITH RA THE OBSCURATION. FORECAST
CONFIDENCE HIGH.
&&
.MARINE...
A HIGH SURF ADVISORY AND A SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS
WILL BEGIN THIS AFTERNOON AND CONTINUE SUNDAY. HAZARDOUS SEAS WILL
BE MAINLY SOUTH OF SAN CLEMENTE ISLAND. HIGHEST SURF WILL BE IN
SOUTHERN SAN DIEGO COUNTY. AN ISOLATED THUNDERSTORM IS POSSIBLE
TODAY AND EARLY SUNDAY. FORECAST CONFIDENCE MEDIUM TO HIGH...SURF
MIGHT BE MORE IMPRESSIVE THAN FORECAST IN NORTH SD AND ORANGE
COUNTIES.
ANOTHER LARGE SWELL ARRIVES NEW YEARS DAY AND CONTINUES INTO
THURSDAY. HIGH SURF ADVISORIES MAY BE NEEDED THEN.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...HIGH SURF ADVISORY FROM 2 PM THIS AFTERNOON TO 2 PM PST SUNDAY
FOR THE SAN DIEGO COUNTY COASTAL AREAS.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 PM THIS AFTERNOON
TO 2 PM PST SUNDAY FOR THE WATERS FROM SAN MATEO POINT TO
THE MEXICAN BORDER EXTENDING 30 TO 60 NM OUT INCLUDING SAN
CLEMENTE ISLAND.
&&
$$
PUBLIC...PG
AVIATION/MARINE...PIERCE
AREA FORECAST DISCUSSION...CORRECTED
NWS LINCOLN IL
226 PM CST SAT DEC 29 2012
.DISCUSSION...
ISSUED 220 PM CST SAT DEC 29 2012
THE MAIN CONCERN IS THE STORM SYSTEM FOR MONDAY AND NEW YEARS EVE.
MAJOR DIFFERENCES ARE STILL SHOWING UP BETWEEN THE MODELS ON THIS
ONE. THE NAM IS MUCH STRONGER AND FARTHER NORTH WITH THE BAND OF
HEAVY SNOW...INDICATING 4-7 INCHES OF SNOW ACROSS A LARGE PORTION
OF CENTRAL IL...NORTH OF I-70. PART OF THAT HAS TO DO WITH ITS
CONTINUATION OF STEADY SNOWS IN THE NORTH OVERNIGHT NEW YEARS
EVE...WHERE THE OTHER MODELS DROP PRECIP OFF IN THE EVENING. THAT
ADDITIONAL SNOW SEEMS TO BE LINKED TO THE NAM BEING THE ONLY
MODEL TO TAKE A LOW PRESSURE CENTER ACROSS SOUTHERN ILLINOIS NEW
YEARS EVE NIGHT.
THE CANADIAN GEM HAS A SIMILAR PATH FOR THE SNOW BAND AS THE
NAM...BUT HAS LESS ACCUMULATION. THE ECMWF/GFS/UKMET ARE ALL
MUCH FARTHER SOUTH AND WEAKER WITH THE DYNAMICS/PRECIP IN OUR
AREA. THEY DO INDICATE 2-3 INCHES COULD ACCUMULATE SOUTHEAST OF
I-70...WITH THE NORTHERN EDGE OF 1 INCH NEAR I-72. THAT IS THE
PATH THAT HPC HAS GENERALLY FOLLOWED...AND WE WERE PRIMARILY
INDICATING THAT IN OUR GRIDS. HOWEVER...THE NAM AND RAP WERE THE
ONLY MODELS TO SHOW THE AMOUNT OF SNOW WE PICKED UP IN OUR
SOUTHEAST COUNTIES LAST NIGHT...SO THAT LEAVES SOME UNEASY CONCERN
FOR SUCH A BUSY HOLIDAY NIGHT...IF THAT SNOW BAND DOES SHIFT
NORTH.
WE WILL GENERALLY STAY THE COURSE FOR NOW AND ADJUST AMOUNTS
SLIGHTLY TOWARD THE CURRENT SOUTHWARD CONSENSUS.
SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT
AFTER SOME LINGERING LIGHT SNOW SHOWERS/FLURRIES DEPART TO THE
EAST THIS EVENING...CLEARING SKIES APPEAR POISED TO MOVE INTO
CENTRAL ILLINOIS. NIGHT TIME MOISTURE/CLOUD TRENDS CAN BE A BIT
TRICKY WITH ADVANCING HIGH PRESSURE...SINCE THE SUBSIDENCE
INVERSION CAN SOMETIMES TRAP LOW LEVEL MOISTURE THAT THE WEAKER
LOW LEVEL WINDS ARE UNABLE TO PUSH OUT. THAT CAN LEAD TO BACK-
BUILDING LOW CLOUDS/STRATUS AT NIGHT...AFTER A STEADY CLEARING
PROGRESS IS EVIDENT BEFORE SUNSET. PILOT REPORTS CONFIRM THE THIN
LAYER OF MOISTURE OF THIS CLOUD DECK...SO THE CLEARING MAY
CONTINUE TONIGHT AS ADVERTISED IN THE MODELS. WE DID SLOW DOWN THE
PROGRESSION IN THE SKY GRIDS...BUT DO EVENTUALLY CLEAR THINGS OUT
IN THE EAST TOWARD MORNING.
THE TIMING OF THE CLEARING CAN HAVE A BIG IMPACT ON LOW
TEMPERATURES...BUT WITH CLEARING EXPECTED IN MOST AREAS BY
MORNING...WE SHOULD BE SEE LOWS DROP BELOW NORMAL ACROSS THE
BOARD...WITH SOME SINGLE DIGIT LOWS NW OF THE IL RIVER.
HIGH PRESSURE WILL PROVIDE SUNNY SKIES AND QUIET CONDITIONS ON
SUNDAY...BUT THE QUICKLY APPROACHING LOW PRESSURE SYSTEM WILL
BRING INCREASING CLOUDS SUNDAY NIGHT.
MONDAY MORNING...SNOW SHOULD BEGIN TO ADVANCE ACROSS OUR CENTRAL
COUNTIES FROM SW TO NE. LOOKING AT THE CONSENSUS MODELS
(ECMWF/GFS/UKMET) IT APPEARS THAT THE MAIN PERIOD OF STEADIER
SNOWS WILL BE MONDAY AFTERNOON AND EVENING...WHERE MOST OF THE
ACCUMULATION WILL OCCUR. SNOWFALL TOTALS UNDER THAT SCENARIO WOULD
RANGE FROM LESS THAN A HALF INCH TOWARD PEORIA...WITH THE ONE INCH
LINE AS FAR NORTH AS A LINE FROM RUSHVILLE TO LINCOLN TO
CHAMPAIGN...1-2" FROM THAT LINE SOUTH TO I-70...AND 2-3" SOUTH OF
I-70.
SOME SNOW SHOWERS MAY LINGER IN THE SOUTHEAST AFTER MIDNIGHT NEW
YEARS EVE...BUT PRECIP SHOULD COME TO AN END BY SUNRISE ON
TUESDAY. CLEARING SKIES ARE EVEN FORECAST FOR THE AFTERNOON AS
HIGH PRESSURE BUILDS INTO THE AREA FROM THE WEST. A COLD NIGHT
WILL BE ON TAP TUES NIGHT UNDER CLEAR SKIES AND LIGHT
WINDS...ALONG WITH A FRESH SNOW COVER. LOW TEMPS WOULD LIKELY DROP
BELOW GUIDANCE AND INTO THE SINGLE DIGITS IN MANY AREAS.
LONG TERM...WEDNESDAY THROUGH SATURDAY.
THE EXTENDED PERIOD WILL BE DOMINATED BY COLD AND DRY CONDITIONS
UNDER SURFACE HIGH PRESSURE. THE NORTHERN STEAM STORM TRACK LOOKS
TO REMAIN FARTHER NORTH ACROSS THE GREAT LAKES...AND THE SOUTHERN
STREAM REMAINS SOUTH...PUSHING STORM SYSTEMS ACROSS THE GULF
COAST. WE WILL KEEP HIGHS AND LOWS BELOW NORMAL...WITH THE COLDEST
NIGHT LOOKING LIKE THURSDAY NIGHT.
SHIMON
&&
.AVIATION...
ISSUED 1117 AM CST SAT DEC 29 2012
FLURRIES REMAIN SCATTERED AROUND THE AREA LATE THIS MORNING WITH
OCCASIONAL VSBYS AS LOW AS 1SM. THESE CONDITIONS SHOULD CONTINUE
THROUGH THE AFTERNOON WITH A GRADUAL DROP OFF IN COVERAGE THIS
EVENING. MIDDAY SAT IMAGERY SHOWS ONLY SLOW PROGRESS OF CLEARING
ACROSS IOWA WITH CIGS ACTUALLY LOWER ACROSS ERN IA COMPARED TO THE
FORECAST TAF SITES. AS MID-LEVEL ANTI-CYCLONIC FLOW BEGINS TO
PRODUCE SUBSIDENCE TONIGHT...PARTIAL CLEARING WILL SPREAD
SOUTHWEST TO NORTHEAST LATE TONIGHT AND CIGS SHOULD CLIMB BUT
LIKELY REMAIN MVFR UNTIL THEY SCATTER OUT SUNDAY MORNING.
BARKER
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS LINCOLN IL
220 PM CST SAT DEC 29 2012
.DISCUSSION...
ISSUED 220 PM CST SAT DEC 29 2012
THE MAIN CONCERN IS THE STORM SYSTEM FOR MONDAY AND NEW YEARS EVE.
MAJOR DIFFERENCES ARE STILL SHOWING UP BETWEEN THE MODELS ON THIS
ONE. THE NAM IS MUCH STRONGER AND FARTHER NORTH WITH THE BAND OF
HEAVY SNOW...INDICATING 4-7 INCHES OF SNOW ACROSS A LARGE PORTION
OF CENTRAL IL...NORTH OF I-70. PART OF THAT HAS TO DO WITH ITS
CONTINUATION OF STEADY SNOWS IN THE NORTH OVERNIGHT NEW YEARS
EVE...WHERE THE OTHER MODELS DROP PRECIP OFF IN THE EVENING. THAT
ADDITIONAL SNOW SEEMS TO BE LIKED TO THE NAM BEING THE ONLY
MODEL TO TAKE A LOW PRESSURE CENTER ACROSS SOUTHERN ILLINOIS NEW
YEARS EVE NIGHT.
THE CANADIAN GEM HAS A SIMILAR PATH FOR THE SNOW BAND AS THE
NAM...BUT HAS LESS ACCUMULATION. THE ECMWF/GFS/UKMET ARE ALL
MUCH FARTHER SOUTH AND WEAKER WITH THE DYNAMICS/PRECIP IN OUR
AREA. THEY DO INDICATE 2-3 INCHES COULD ACCUMULATE IN OUR AREA
SOUTHEAST OF I-70...WITH THE NORTHERN EDGE OF 1 INCH NEAR I-72.
THAT IS THE PATH THAT HPC HAS GENERALLY FOLLOWED...AND WE WERE
PRIMARILY INDICATING IN OUR GRIDS. HOWEVER...THE NAM AND RAP WERE
THE ONLY MODELS TO SHOW THE AMOUNT OF SNOW WE PICKED UP IN OUR
SOUTHEAST COUNTIES LAST NIGHT...SO THAT LEAVES SOME UNEASY CONCERN
FOR SUCH A BUSY HOLIDAY NIGHT.
WE WILL GENERALLY STAY THE COURSE FOR NOW AND ADJUST AMOUNTS
SLIGHTLY TOWARD THE CURRENT SOUTHWARD CONSENSUS.
SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT
AFTER SOME LINGERING LIGHT SNOW SHOWERS/FLURRIES DEPART TO THE
EAST THIS EVENING...CLEARING SKIES APPEAR POISED TO MOVE INTO
CENTRAL ILLINOIS. NIGHT TIME MOISTURE/CLOUD TRENDS CAN BE A BIT
TRICKY WITH ADVANCING HIGH PRESSURE...SINCE THE SUBSIDENCE
INVERSION CAN SOMETIMES TRAP LOW LEVEL MOISTURE THAT THE WEAKER
LOW LEVEL WINDS ARE UNABLE TO PUSH OUT. THAT CAN LEAD TO BACK-
BUILDING LOW CLOUDS/STRATUS AT NIGHT...AFTER A STEADY CLEARING
PROGRESS IS EVIDENT BEFORE SUNSET. PILOT REPORTS CONFIRM THE THIN
LAYER OF MOISTURE OF THIS CLOUD DECK...SO THE CLEARING MAY
CONTINUE TONIGHT AS ADVERTISED IN THE MODELS. WE DID SLOW DOWN THE
PROGRESSION IN THE SKY GRIDS...BUT DO EVENTUALLY CLEAR THINGS OUT
IN THE EAST TOWARD MORNING.
THE TIMING OF THE CLEARING CAN HAVE A BIG IMPACT ON LOW
TEMPERATURES...BUT WITH CLEARING IN MOST AREAS BY MORNING...WE
SHOULD BE SEE LOWS DROP BELOW NORMAL ACROSS THE BOARD...WITH
SOME SINGLE DIGIT LOWS NW OF THE IL RIVER.
HIGH PRESSURE WILL PROVIDE SUNNY SKIES AND QUIET CONDITIONS ON
SUNDAY...BUT THE QUICKLY APPROACHING LOW PRESSURE SYSTEM WILL
BRING INCREASING CLOUDS SUNDAY NIGHT.
MONDAY MORNING...SNOW SHOULD BEGIN TO ADVANCE ACROSS OUR CENTRAL
COUNTIES FROM SW TO NE. LOOKING AT THE CONSENSUS MODELS
(ECMWF/GFS/UKMET) IT APPEARS THAT THE MAIN PERIOD OF STEADIER
SNOWS WILL BE MONDAY AFTERNOON AND EVENING...WHERE MOST OF THE
ACCUMULATION WILL OCCUR. SNOWFALL TOTALS UNDER THAT SCENARIO WOULD
RANGE FROM LESS THAN A HALF INCH TOWARD PEORIA...WITH THE ONE INCH
LINE AS FAR NORTH AS A LINE FROM RUSHVILLE TO LINCOLN TO
CHAMPAIGN...1-2" FROM THAT LINE SOUTH TO I-70...AND 2-3" SOUTH OF
I-70.
SOME SNOW SHOWERS MAY LINGER IN THE SOUTHEAST AFTER MIDNIGHT NEW
YEARS EVE...BUT PRECIP SHOULD COME TO AN END BY SUNRISE ON
TUESDAY. CLEARING SKIES ARE EVEN FORECAST FOR THE AFTERNOON AS
HIGH PRESSURE BUILDS INTO THE AREA FROM THE WEST. A COLD NIGHT
WILL BE ON TAP TUES NIGHT UNDER CLEAR SKIES AND LIGHT
WINDS...ALONG WITH A FRESH SNOW COVER. LOW TEMPS WOULD LIKELY DROP
BELOW GUIDANCE AND INTO THE SINGLE DIGITS IN MANY AREAS.
LONG TERM...WEDNESDAY THROUGH SATURDAY.
THE EXTENDED PERIOD WILL BE DOMINATED BY COLD AND DRY CONDITIONS
UNDER SURFACE HIGH PRESSURE. THE NORTHERN STEAM STORM TRACK LOOKS
TO REMAIN FARTHER NORTH ACROSS THE GREAT LAKES...AND THE SOUTHERN
STREAM REMAINS SOUTH...PUSHING STORM SYSTEMS ACROSS THE GULF
COAST. WE WILL KEEP HIGHS AND LOWS BELOW NORMAL...WITH THE COLDEST
NIGHT LOOKING LIKE THURSDAY NIGHT.
SHIMON
&&
.AVIATION...
ISSUED 1117 AM CST SAT DEC 29 2012
FLURRIES REMAIN SCATTERED AROUND THE AREA LATE THIS MORNING WITH
OCCASIONAL VSBYS AS LOW AS 1SM. THESE CONDITIONS SHOULD CONTINUE
THROUGH THE AFTERNOON WITH A GRADUAL DROP OFF IN COVERAGE THIS
EVENING. MIDDAY SAT IMAGERY SHOWS ONLY SLOW PROGRESS OF CLEARING
ACROSS IOWA WITH CIGS ACTUALLY LOWER ACROSS ERN IA COMPARED TO THE
FORECAST TAF SITES. AS MID-LEVEL ANTI-CYCLONIC FLOW BEGINS TO
PRODUCE SUBSIDENCE TONIGHT...PARTIAL CLEARING WILL SPREAD
SOUTHWEST TO NORTHEAST LATE TONIGHT AND CIGS SHOULD CLIMB BUT
LIKELY REMAIN MVFR UNTIL THEY SCATTER OUT SUNDAY MORNING.
BARKER
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
156 PM CST SAT DEC 29 2012
.DISCUSSION...
1159 AM CST
MAIN CONCERN ARE THE ONGOING SNOW SHOWERS ACROSS NORTHEAST
ILLINOIS AND NORTHWEST INDIANA...WITH LAKE EFFECT SNOW SHOWERS TO
PERSIST ACROSS NORTHWEST INDIANA LATE THIS AFTERNOON AND EARLY
EVENING.
LATEST RADAR IMAGERY DEPICTING PERSISTENT SNOW SHOWERS EARLY THIS
AFTERNOON ACROSS THE AREA...WITH ONLY LIGHT SNOW ONGOING AT THIS
TIME. THESE SNOW SHOWERS CONTINUE TO DEVELOP NEAR SURFACE
TROUGH/MID LEVEL TROUGH AXIS SITUATED FROM EASTERN WISCONSIN
SOUTHEAST THROUGH SOUTHERN LAKE MICHIGAN...OUT AHEAD OF SEVERAL
SUBTLE SHORT WAVE TROUGHS TRAVERSING UPPER LEVEL CYCLONIC FLOW.
DESPITE THE APPROACH OF ANOTHER MID LEVEL TROUGH AXIS TO THE
WEST...DEEPER FORCING WITHIN THIS SURFACE/MID LEVEL TROUGH AXIS
WILL WEAKEN WITH TIME EARLY THIS AFTERNOON AS IT DAMPENS OUT WITH
MAIN SURFACE LOW CONTINUING TO DEPART TO THE EAST. WHAT THIS MEANS
IN THE NEAR TERM IS CURRENT LIGHT SNOW ACROSS NORTHEAST ILLINOIS
WILL SLOWLY DIMINISH THROUGH MID AFTERNOON WITH ONLY LIGHT
ACCUMULATIONS OF AT MOST A COUPLE TENTHS OF AN INCH OF SNOWFALL.
ALTHOUGH...DO EXPECT FLURRIES TO REMAIN POSSIBLE ACROSS ALL OF
NORTHERN ILLINOIS THROUGH THE REMAINDER OF THE AFTERNOON AS WEAK
ASCENT OUT AHEAD OF THE APPROACHING MID LEVEL TROUGH REMAINS.
FOCUS THEN SHIFTS TO LAKE EFFECT POTENTIAL ACROSS NORTHWEST
INDIANA. CURRENT RADAR RETURNS ACROSS SOUTHERN LAKE MICHIGAN AND
NORTHWEST INDIANA ARE INDICATING THAT BETTER LAKE EFFECT SNOW IS
ONGOING AT THIS TIME. THIS IS IN RESPONSE TO BOUNDARY LAYER WINDS
SHIFTING MORE NORTHERLY ACROSS THE LENGTH OF THE LAKE AND COLD
ADVECTION HELPING FOR BETTER THERMODYNAMIC CONDITIONS OVER THE
LAKE. WITH LATEST RAP ANALYSIS INDICATING MODERATE DELTA TS IN
PLACE AND STRONG FORCING ASSOCIATED WITH CURRENT SURFACE
CONVERGENCE ACROSS THE SOUTHERN END OF THE LAKE...EXPECT THIS LAKE
EFFECT SNOW TO CONTINUE TO INCREASE IN INTENSITY THROUGH THIS
AFTERNOON. ALTHOUGH DO EXPECT SEVERAL HOURS OF LIGHT TO MODERATE
SNOW ACROSS LAKE AND PORTER COUNTIES IN INDIANA...THIS WILL REMAIN
RATHER BRIEF AS BETTER CONVERGENCE WILL CONTINUE TO SHIFT EAST
WITH TIME. THIS WILL SHIFT BETTER SNOW DEVELOPMENT JUST EAST OF
PORTER COUNTY BY LATE THIS AFTERNOON. HIGH RES/SHORT TERM GUIDANCE
HAS BEEN INDICATING THIS LIKELY SCENARIO OVER THE LAST COUPLE OF
HOURS...AND FEEL CONFIDENT THIS WILL OCCUR AS CURRENT OBSERVATIONS
ARE ALREADY SHOWING BETTER CONVERGENCE JUST TO THE EAST OF OUR
CWA...WITH WESTERLY WINDS IN PLACE ACROSS PORTER COUNTY. SNOWFALL
THIS AFTERNOON FOR LAKE AND PORTER COUNTIES IN INDIANA WILL
CONSIST OF AROUND AN INCH OF ADDITIONAL SNOWFALL IN LAKE
COUNTY...AND WITH 1 TO 2 INCHES EXPECTED IN PORTER COUNTY. WITH
THE MAIN AXIS OF HEAVIER SNOW EXPECTED JUST TO THE EAST OF PORTER
COUNTY LINE THROUGH THIS EVENING...IT WOULD NOT BE OUT OF THE
QUESTION FOR AREAS IN AND AROUND THIS LOCATION TO POSSIBLY OBSERVE
3 INCHES BEFORE ALL THE SNOW SHIFTS COMPLETELY TO THE EAST.
RODRIGUEZ
//PREV DISCUSSION...
453 AM CST
LIGHT SNOW AND FLURRIES TO CONTINUE ACROSS THE NORTHERN 2/3RD OF
THE FORECAST AREA THIS MORNING. VAD WINDS FROM SE WI AND NE IL
88D AND TERMINAL DOPPLER RADARS ARE SHOWING A WEAK MID LEVEL LOW
OVER THE EASTERN PORTION OF THE WI-IL STATE LINE. THE 29.06Z GFS
AND 29.00Z GEM BEST DEPICT THE FEATURE BUT POSITION IT A BIT TOO
FAR TO THE N. THIS MID LEVEL LOW IS PROGGED BY THE ABOVE
MENTIONED MODELS TO FURTHER WEAKEN AS IT MOVES ESE TO FAR SW
LOWER MI AND NORTHERN IN BY 18Z. WEAK LOWER LEVEL WARM AIR
ADVECTION ASSOCIATED WITH THIS MID LEVEL LOW IS RESULTING IN
SUFFICIENT ISENTROPIC UPGLIDE FOR LIGHT SNOW AND FLURRIES TO
CONTINUE UNTIL LATER THIS MORNING WHEN THE DISTURBANCE HAS MOVED
FURTHER TO THE ESE.
WATER VAPOR SATELLITE LOOP SHOWS THE MEAN UPPER TROF AXIS FROM
NORTHWESTERN HUDSON BAY S ACROSS THE UPPER MIDWEST AND ON TO THE
LOWER MS VALLEY. WITHIN THIS TROF ARE A PAIR OF SHORT WAVES...
ONE CURRENTLY OVER SOUTHERN LAKE MI S TO SW IN GENERATING A BROAD
SWATH OF PRECIPITATION FROM THE MID OH VALLEY TO THE NORTHEASTERN
STATES. THE SECOND SHORT WAVE IS OVER EASTERN MN SSW TO IA AND
THEN SW TO EASTERN KS. NO PRECIPITATION OR COOLING CLOUD TOPS ARE
SEEN WITH THIS FEATURE WHICH IS TO CROSS OVER THE LOCAL FORECAST
AREA DURING THE EARLY AND MID AFTERNOON.
DEEPER CLOUDS HAVE BEEN MOVING TO THE E ACROSS SE WI AND NW AND
W CENTRAL IL DURING THE EARLY MORNING HOURS. LOW STRATUS STILL
EXTENDS ALL THE WAY W ACROSS IA TO THE MO RIVER AND MN TO NEAR
ITS BORDER WITH THE DAKOTAS. MODEL RH PROGS SUGGEST THIS IS TO
CONTINUE TODAY THOUGH THE LOWER CLOUD DECK WILL NOT START
CLEARING W TO E UNTIL LATE AFTERNOON AND TONIGHT. SUSPECT THAT
LACK OF MID LEVEL CLOUDS AND OF THICKER LOW LEVEL CLOUDS WILL
PRECLUDE ANY ADDITIONAL LIGHT SNOW THIS AFTERNOON.
HOWEVER...COLDER AIR SPREADING S OVER THE WESTERN GREAT LAKES IN
THE WAKE OF THE FIRST SHORT WAVE IS RESULTING IN THE DEVELOPMENT
OF A MID LAKE SNOW BAND WHICH STARTED FORMING AROUND 06Z. THE
BAND IS BECOMING WELL ORGANIZED AND E OF FAR SOUTHEASTERN WI AND
IS JUST OFFSHORE OF FAR NW IN. EARLIER MODELS SUGGESTED THAT THE
BAND WOULD FORM ALONG THE WEST SIDE OF THE LAKE AND CATCH EXTREME
NE IL BEFORE BACKING FLOW BUSHED IT OUT TO MID LAKE. IT NOW
APPEARS THAT AREAS ALONG THE IL SHORE WILL BE SPARED ANY LAKE
EFFECT SNOWS AS LATEST HI RES MODELS ARE INDICATING THE
CONVERGENCE AND RESULTING SNOW BAND WILL IMPACT PORTER AND
EASTERN LAKE COUNTIES THIS MORNING BEFORE CONTINUED BACKING OF
THE WIND FIELD SHIFTS THE TAIL END OF THE BAND FURTHER E TOWARD
FAR SW LOWER MI AND N CENTRAL IN.
NO SIGNIFICANT STORMS SEEN AFFECTING THE AREA OVER THE NEXT WEEK.
THERE IS A CHANCE OF SOME LIGHT SNOW ACROSS THE SOUTH PORTION OF
THE FORECAST AREA MON AND MON NIGHT AS A DISTURBANCE MOVING E
ACROSS THE PLAINS SENDS A RIPPLE ALONG A STATIONARY FRONT THE IS
PROGGED TO EXTEND FROM SOUTHERN MO NORTHEASTWARD ACROSS SW AND E
CENTRAL IL. THERE IS ALSO A SMALL CHANCE OF LIGHT SNOW ACROSS
MAINLY NORTHERN IL WED NIGHT INTO THU AS A SHORT WAVE DROPS OVER
THE UPPER MIDWEST AND MID MS VALLEY.
OF NOTE IS THE COLDER...MORE TYPICAL JANUARY TYPE TEMPERATURES
THAT WILL BE FELT ESPECIALLY DURING MID AND LATE NEXT WEEK. THE
COLD AIR THAT HAS BEEN CONTAINED TO THE ARCTIC AND NORTHERN
CANADA HAS GRADUALLY SPREAD S AND NOW SITS OVER MANITOBA AND
WESTERN ONTARIO. AS THE SHORT WAVE CROSSES THE REGION LATER TODAY
AND THIS EVENING THIS COLD AIR WILL BE DIRECTED ACROSS THE UPPER
MIDWEST. THIS COLDER AIR STARTS TO RETREAT OVERNIGHT SAT AND SUN
AS RIDGING BUILDS IN FROM THE W BACKING THE FLOW FORM OUT OF THE
W AND EVENTUALLY SW SO BY MONDAY TEMPERATURES AT BACK TO OR A TAD
ABOVE NORMALS FOR EARLY JANUARY.
THE COLD AIR DEPARTS FOR ONLY A SHORT PERIOD BEFORE MAKING A
STRONGER APPEARANCE DURING BUT MAKES A RETURN VISIT MONDAY AS A
COLD FRONT TRAILING SOUTHWESTWARD FROM LOW PRESSURE MOVING ACROSS
ONTARIO. THE COLD AIR WILL BE AROUND FOR A BIT LONGER THIS TIME
AS THE MEAN FLOW REMAINS FROM THE NNW AND N THROUGH THE MID AND
LATE WEEK. TEMPERATURES LOOK TO MODERATE FOR NEXT WEEKEND AS AIR
OF PACIFIC ORIGIN SPREADS ACROSS THE NORTHERN ROCKIES AND
NORTHERN PLAINS AS THE UPPER FLOW DE-AMPLIFIES.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* SNOW FLURRIES IN THE AREA. VISIBILITY SHOULD REMAIN VFR.
* WEST TO NORTHWEST WINDS. GRADUALLY TURNING TO SOUTHWEST LATE
TONIGHT INTO SUNDAY.
PAW
//DISCUSSION...UPDATED 18Z...
AVIATION CONDITIONS CONTINUE TO BE CHALLENGING FOR THE CHICAGO
AREA TERMINALS THIS AFTERNOON. THERE IS A BAND OF LIGHT SNOW
ACROSS THE AREA THAN WILL CONTINUE TO AFFECT GYY AND COULD GET
INTO ORD...MDW OR DPA AT TIMES. VISIBILITIES IN THE 3-5 MILES
RANGE WITH THE LIGHT SNOW. EVENTUALLY THE SLIGHTLY DRIER AIR AT RFD
THIS AFTERNOON WILL WORK ITS WAY EAST AND BRING THE SNOW TO AN END
THIS EVENING.
A HIGH PRESSURE RIDGE WILL MOVE ACROSS NORTHERN ILLINOIS AND
NORTHWEST INDIANA TONIGHT AND SUNDAY...WHICH WILL HELP TO BREAK UP
THE CEILINGS AND SHIFT THE WINDS TO THE WEST AND SOUTHWEST.
PAW
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* MEDIUM CONFIDENCE IN VISIBILITY REMAINING VFR.
* HIGH CONFIDENCE IN WIND TREND.
PAW
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...DRY. VFR.
* MONDAY...DRY. MVFR POSSIBLE.
* TUESDAY AND WEDNESDAY...DRY/VFR.
* WEDNESDAY NIGHT AND THURSDAY...SLIGHT CHANCE OF SNOW SHOWERS/MVFR.
* FRIDAY...DRY. VFR.
BEACHLER
&&
.MARINE...
300 AM CST
RATHER QUIET PERIOD FOR LAKE MICHIGAN WILL CONTINUE...OUTSIDE OF
THE POTENTIAL FOR SMALL CRAFT CONDS ALONG THE NORTHWEST INDIANA
NEARSHORE WATERS. OTHERWISE WINDS WILL REMAIN SUB-GALE CRITERIA
FOR THE OPEN WATERS.
A TROUGH OF LOW PRESSURE CONTINUES TO LIFT OFF TO THE NORTHEAST...AS
A BROAD RIDGE OF HIGH PRESSURE OVER THE CENTRAL PLAINS STRETCHES
TO THE WESTERN GULF OF MEXICO. THIS HIGH PRESSURE WILL DRIFT EAST
AND BECOME CENTERED ACROSS THE TENNESSEE VALLEY SUNDAY. THIS WILL
PROVIDE AN INFLUENCE ON THE WEATHER OVER LAKE MICHIGAN WITH A
GRADIENT SETTING THE STAGE FOR WINDS TO INCREASE TO 15 TO 25 KT
FROM THE NW/W. A FEW GUSTS TO 30 KT LATE TONIGHT MAY OCCUR...HOWEVER
NOT EXPECTING A WIDESPREAD SITUATION. AS A RESULT OF THE INCREASED
WINDS AND FETCH...WAVES WILL BUILD TO SMALL CRAFT CONDS OR 4 TO 7
FT ALONG THE INDIANA NEARSHORE WATERS THIS AFTERNOON THROUGH
SUNDAY MORNING.
THEN WINDS SLOWLY SHIFT TO THE SW MIDDAY SUN AND SHOULD AID IN
LOWERING WAVES TO ARND 3 TO 5 FT. THEN THE SOUTHWEST FLOW WILL
CONTINUE THROUGH MON AS YET ANOTHER LOW PRESSURE SYSTEM IS
EXPECTED TO LIFT NORTHEAST ACROSS THE UPPER MIDWEST TO NORTH OF
LAKE SUPERIOR MON. A TRAILING FRONTAL BOUNDARY WILL REACH LAKE
MICHIGAN LATER MON. THEN ANOTHER TIGHT PRESSURE GRADIENT DEVELOPS
TUE...HOWEVER GUIDANCE DOES NOT INDICATE THAT WINDS WOULD GUSTS
ABOVE 30 KT.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 9 AM SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1226 PM CST SAT DEC 29 2012
.DISCUSSION...
1159 AM CST
MAIN CONCERN ARE THE ONGOING SNOW SHOWERS ACROSS NORTHEAST
ILLINOIS AND NORTHWEST INDIANA...WITH LAKE EFFECT SNOW SHOWERS TO
PERSIST ACROSS NORTHWEST INDIANA LATE THIS AFTERNOON AND EARLY
EVENING.
LATEST RADAR IMAGERY DEPICTING PERSISTENT SNOW SHOWERS EARLY THIS
AFTERNOON ACROSS THE AREA...WITH ONLY LIGHT SNOW ONGOING AT THIS
TIME. THESE SNOW SHOWERS CONTINUE TO DEVELOP NEAR SURFACE
TROUGH/MID LEVEL TROUGH AXIS SITUATED FROM EASTERN WISCONSIN
SOUTHEAST THROUGH SOUTHERN LAKE MICHIGAN...OUT AHEAD OF SEVERAL
SUBTLE SHORT WAVE TROUGHS TRAVERSING UPPER LEVEL CYCLONIC FLOW.
DESPITE THE APPROACH OF ANOTHER MID LEVEL TROUGH AXIS TO THE
WEST...DEEPER FORCING WITHIN THIS SURFACE/MID LEVEL TROUGH AXIS
WILL WEAKEN WITH TIME EARLY THIS AFTERNOON AS IT DAMPENS OUT WITH
MAIN SURFACE LOW CONTINUING TO DEPART TO THE EAST. WHAT THIS MEANS
IN THE NEAR TERM IS CURRENT LIGHT SNOW ACROSS NORTHEAST ILLINOIS
WILL SLOWLY DIMINISH THROUGH MID AFTERNOON WITH ONLY LIGHT
ACCUMULATIONS OF AT MOST A COUPLE TENTHS OF AN INCH OF SNOWFALL.
ALTHOUGH...DO EXPECT FLURRIES TO REMAIN POSSIBLE ACROSS ALL OF
NORTHERN ILLINOIS THROUGH THE REMAINDER OF THE AFTERNOON AS WEAK
ASCENT OUT AHEAD OF THE APPROACHING MID LEVEL TROUGH REMAINS.
FOCUS THEN SHIFTS TO LAKE EFFECT POTENTIAL ACROSS NORTHWEST
INDIANA. CURRENT RADAR RETURNS ACROSS SOUTHERN LAKE MICHIGAN AND
NORTHWEST INDIANA ARE INDICATING THAT BETTER LAKE EFFECT SNOW IS
ONGOING AT THIS TIME. THIS IS IN RESPONSE TO BOUNDARY LAYER WINDS
SHIFTING MORE NORTHERLY ACROSS THE LENGTH OF THE LAKE AND COLD
ADVECTION HELPING FOR BETTER THERMODYNAMIC CONDITIONS OVER THE
LAKE. WITH LATEST RAP ANALYSIS INDICATING MODERATE DELTA TS IN
PLACE AND STRONG FORCING ASSOCIATED WITH CURRENT SURFACE
CONVERGENCE ACROSS THE SOUTHERN END OF THE LAKE...EXPECT THIS LAKE
EFFECT SNOW TO CONTINUE TO INCREASE IN INTENSITY THROUGH THIS
AFTERNOON. ALTHOUGH DO EXPECT SEVERAL HOURS OF LIGHT TO MODERATE
SNOW ACROSS LAKE AND PORTER COUNTIES IN INDIANA...THIS WILL REMAIN
RATHER BRIEF AS BETTER CONVERGENCE WILL CONTINUE TO SHIFT EAST
WITH TIME. THIS WILL SHIFT BETTER SNOW DEVELOPMENT JUST EAST OF
PORTER COUNTY BY LATE THIS AFTERNOON. HIGH RES/SHORT TERM GUIDANCE
HAS BEEN INDICATING THIS LIKELY SCENARIO OVER THE LAST COUPLE OF
HOURS...AND FEEL CONFIDENT THIS WILL OCCUR AS CURRENT OBSERVATIONS
ARE ALREADY SHOWING BETTER CONVERGENCE JUST TO THE EAST OF OUR
CWA...WITH WESTERLY WINDS IN PLACE ACROSS PORTER COUNTY. SNOWFALL
THIS AFTERNOON FOR LAKE AND PORTER COUNTIES IN INDIANA WILL
CONSIST OF AROUND AN INCH OF ADDITIONAL SNOWFALL IN LAKE
COUNTY...AND WITH 1 TO 2 INCHES EXPECTED IN PORTER COUNTY. WITH
THE MAIN AXIS OF HEAVIER SNOW EXPECTED JUST TO THE EAST OF PORTER
COUNTY LINE THROUGH THIS EVENING...IT WOULD NOT BE OUT OF THE
QUESTION FOR AREAS IN AND AROUND THIS LOCATION TO POSSIBLY OBSERVE
3 INCHES BEFORE ALL THE SNOW SHIFTS COMPLETELY TO THE EAST.
RODRIGUEZ
&&
.PREV DISCUSSION...
453 AM CST
LIGHT SNOW AND FLURRIES TO CONTINUE ACROSS THE NORTHERN 2/3RD OF
THE FORECAST AREA THIS MORNING. VAD WINDS FROM SE WI AND NE IL
88D AND TERMINAL DOPPLER RADARS ARE SHOWING A WEAK MID LEVEL LOW
OVER THE EASTERN PORTION OF THE WI-IL STATE LINE. THE 29.06Z GFS
AND 29.00Z GEM BEST DEPICT THE FEATURE BUT POSITION IT A BIT TOO
FAR TO THE N. THIS MID LEVEL LOW IS PROGGED BY THE ABOVE
MENTIONED MODELS TO FURTHER WEAKEN AS IT MOVES ESE TO FAR SW
LOWER MI AND NORTHERN IN BY 18Z. WEAK LOWER LEVEL WARM AIR
ADVECTION ASSOCIATED WITH THIS MID LEVEL LOW IS RESULTING IN
SUFFICIENT ISENTROPIC UPGLIDE FOR LIGHT SNOW AND FLURRIES TO
CONTINUE UNTIL LATER THIS MORNING WHEN THE DISTURBANCE HAS MOVED
FURTHER TO THE ESE.
WATER VAPOR SATELLITE LOOP SHOWS THE MEAN UPPER TROF AXIS FROM
NORTHWESTERN HUDSON BAY S ACROSS THE UPPER MIDWEST AND ON TO THE
LOWER MS VALLEY. WITHIN THIS TROF ARE A PAIR OF SHORT WAVES...
ONE CURRENTLY OVER SOUTHERN LAKE MI S TO SW IN GENERATING A BROAD
SWATH OF PRECIPITATION FROM THE MID OH VALLEY TO THE NORTHEASTERN
STATES. THE SECOND SHORT WAVE IS OVER EASTERN MN SSW TO IA AND
THEN SW TO EASTERN KS. NO PRECIPITATION OR COOLING CLOUD TOPS ARE
SEEN WITH THIS FEATURE WHICH IS TO CROSS OVER THE LOCAL FORECAST
AREA DURING THE EARLY AND MID AFTERNOON.
DEEPER CLOUDS HAVE BEEN MOVING TO THE E ACROSS SE WI AND NW AND
W CENTRAL IL DURING THE EARLY MORNING HOURS. LOW STRATUS STILL
EXTENDS ALL THE WAY W ACROSS IA TO THE MO RIVER AND MN TO NEAR
ITS BORDER WITH THE DAKOTAS. MODEL RH PROGS SUGGEST THIS IS TO
CONTINUE TODAY THOUGH THE LOWER CLOUD DECK WILL NOT START
CLEARING W TO E UNTIL LATE AFTERNOON AND TONIGHT. SUSPECT THAT
LACK OF MID LEVEL CLOUDS AND OF THICKER LOW LEVEL CLOUDS WILL
PRECLUDE ANY ADDITIONAL LIGHT SNOW THIS AFTERNOON.
HOWEVER...COLDER AIR SPREADING S OVER THE WESTERN GREAT LAKES IN
THE WAKE OF THE FIRST SHORT WAVE IS RESULTING IN THE DEVELOPMENT
OF A MID LAKE SNOW BAND WHICH STARTED FORMING AROUND 06Z. THE
BAND IS BECOMING WELL ORGANIZED AND E OF FAR SOUTHEASTERN WI AND
IS JUST OFFSHORE OF FAR NW IN. EARLIER MODELS SUGGESTED THAT THE
BAND WOULD FORM ALONG THE WEST SIDE OF THE LAKE AND CATCH EXTREME
NE IL BEFORE BACKING FLOW BUSHED IT OUT TO MID LAKE. IT NOW
APPEARS THAT AREAS ALONG THE IL SHORE WILL BE SPARED ANY LAKE
EFFECT SNOWS AS LATEST HI RES MODELS ARE INDICATING THE
CONVERGENCE AND RESULTING SNOW BAND WILL IMPACT PORTER AND
EASTERN LAKE COUNTIES THIS MORNING BEFORE CONTINUED BACKING OF
THE WIND FIELD SHIFTS THE TAIL END OF THE BAND FURTHER E TOWARD
FAR SW LOWER MI AND N CENTRAL IN.
NO SIGNIFICANT STORMS SEEN AFFECTING THE AREA OVER THE NEXT WEEK.
THERE IS A CHANCE OF SOME LIGHT SNOW ACROSS THE SOUTH PORTION OF
THE FORECAST AREA MON AND MON NIGHT AS A DISTURBANCE MOVING E
ACROSS THE PLAINS SENDS A RIPPLE ALONG A STATIONARY FRONT THE IS
PROGGED TO EXTEND FROM SOUTHERN MO NORTHEASTWARD ACROSS SW AND E
CENTRAL IL. THERE IS ALSO A SMALL CHANCE OF LIGHT SNOW ACROSS
MAINLY NORTHERN IL WED NIGHT INTO THU AS A SHORT WAVE DROPS OVER
THE UPPER MIDWEST AND MID MS VALLEY.
OF NOTE IS THE COLDER...MORE TYPICAL JANUARY TYPE TEMPERATURES
THAT WILL BE FELT ESPECIALLY DURING MID AND LATE NEXT WEEK. THE
COLD AIR THAT HAS BEEN CONTAINED TO THE ARCTIC AND NORTHERN
CANADA HAS GRADUALLY SPREAD S AND NOW SITS OVER MANITOBA AND
WESTERN ONTARIO. AS THE SHORT WAVE CROSSES THE REGION LATER TODAY
AND THIS EVENING THIS COLD AIR WILL BE DIRECTED ACROSS THE UPPER
MIDWEST. THIS COLDER AIR STARTS TO RETREAT OVERNIGHT SAT AND SUN
AS RIDGING BUILDS IN FROM THE W BACKING THE FLOW FORM OUT OF THE
W AND EVENTUALLY SW SO BY MONDAY TEMPERATURES AT BACK TO OR A TAD
ABOVE NORMALS FOR EARLY JANUARY.
THE COLD AIR DEPARTS FOR ONLY A SHORT PERIOD BEFORE MAKING A
STRONGER APPEARANCE DURING BUT MAKES A RETURN VISIT MONDAY AS A
COLD FRONT TRAILING SOUTHWESTWARD FROM LOW PRESSURE MOVING ACROSS
ONTARIO. THE COLD AIR WILL BE AROUND FOR A BIT LONGER THIS TIME
AS THE MEAN FLOW REMAINS FROM THE NNW AND N THROUGH THE MID AND
LATE WEEK. TEMPERATURES LOOK TO MODERATE FOR NEXT WEEKEND AS AIR
OF PACIFIC ORIGIN SPREADS ACROSS THE NORTHERN ROCKIES AND
NORTHERN PLAINS AS THE UPPER FLOW DE-AMPLIFIES.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* AREAS OF LIGHT SNOW WILL CONTINUE TO BE NEARBY INTO LATE
AFTERNOON. POSSIBILITY FOR BRIEF VISIBILITY IN THE 3-5 MILE
RANGE...BUT CONFIDENCE TOO LOW TO MENTION IN THE TAFS AT THIS
TIME.
* CEILINGS GENERALLY IN THE 1000 TO 1500 FEET RANGE THROUGH THE
AFTERNOON.
* NORTHWEST WINDS AROUND 10 KT...SLOWLY TURNING WEST/SOUTHWEST
LATE TONIGHT INTO EARLY SUNDAY.
PAW
//DISCUSSION...UPDATED 18Z...
AVIATION CONDITIONS CONTINUE TO BE CHALLENGING FOR THE CHICAGO
AREA TERMINALS THIS AFTERNOON. THERE IS A BAND OF LIGHT SNOW
ACROSS THE AREA THAN WILL CONTINUE TO AFFECT GYY AND COULD GET
INTO ORD...MDW OR DPA AT TIMES. VISIBILITIES IN THE 3-5 MILES
RANGE WITH THE LIGHT SNOW. EVENTUALLY THE SLIGHTLY DRIER AIR AT RFD
THIS AFTERNOON WILL WORK ITS WAY EAST AND BRING THE SNOW TO AN END
THIS EVENING.
A HIGH PRESSURE RIDGE WILL MOVE ACROSS NORTHERN ILLINOIS AND
NORTHWEST INDIANA TONIGHT AND SUNDAY...WHICH WILL HELP TO BREAK UP
THE CEILINGS AND SHIFT THE WINDS TO THE WEST AND SOUTHWEST.
PAW
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE IN CEILING AND VISIBILITY TREND. MEDIUM
CONFIDENCE IN EXACT VALUES AND TIMING.
* HIGH CONFIDENCE IN WIND TREND.
PAW
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...DRY. VFR.
* MONDAY...DRY. MVFR POSSIBLE.
* TUESDAY AND WEDNESDAY...DRY/VFR.
* WEDNESDAY NIGHT AND THURSDAY...SLIGHT CHANCE OF SNOW SHOWERS/MVFR.
* FRIDAY...DRY. VFR.
BEACHLER
&&
.MARINE...
300 AM CST
RATHER QUIET PERIOD FOR LAKE MICHIGAN WILL CONTINUE...OUTSIDE OF
THE POTENTIAL FOR SMALL CRAFT CONDS ALONG THE NORTHWEST INDIANA
NEARSHORE WATERS. OTHERWISE WINDS WILL REMAIN SUB-GALE CRITERIA
FOR THE OPEN WATERS.
A TROUGH OF LOW PRESSURE CONTINUES TO LIFT OFF TO THE NORTHEAST...AS
A BROAD RIDGE OF HIGH PRESSURE OVER THE CENTRAL PLAINS STRETCHES
TO THE WESTERN GULF OF MEXICO. THIS HIGH PRESSURE WILL DRIFT EAST
AND BECOME CENTERED ACROSS THE TENNESSEE VALLEY SUNDAY. THIS WILL
PROVIDE AN INFLUENCE ON THE WEATHER OVER LAKE MICHIGAN WITH A
GRADIENT SETTING THE STAGE FOR WINDS TO INCREASE TO 15 TO 25 KT
FROM THE NW/W. A FEW GUSTS TO 30 KT LATE TONIGHT MAY OCCUR...HOWEVER
NOT EXPECTING A WIDESPREAD SITUATION. AS A RESULT OF THE INCREASED
WINDS AND FETCH...WAVES WILL BUILD TO SMALL CRAFT CONDS OR 4 TO 7
FT ALONG THE INDIANA NEARSHORE WATERS THIS AFTERNOON THROUGH
SUNDAY MORNING.
THEN WINDS SLOWLY SHIFT TO THE SW MIDDAY SUN AND SHOULD AID IN
LOWERING WAVES TO ARND 3 TO 5 FT. THEN THE SOUTHWEST FLOW WILL
CONTINUE THROUGH MON AS YET ANOTHER LOW PRESSURE SYSTEM IS
EXPECTED TO LIFT NORTHEAST ACROSS THE UPPER MIDWEST TO NORTH OF
LAKE SUPERIOR MON. A TRAILING FRONTAL BOUNDARY WILL REACH LAKE
MICHIGAN LATER MON. THEN ANOTHER TIGHT PRESSURE GRADIENT DEVELOPS
TUE...HOWEVER GUIDANCE DOES NOT INDICATE THAT WINDS WOULD GUSTS
ABOVE 30 KT.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 9 AM SUNDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
1233 PM EST SAT DEC 29 2012
.AVIATION...
COLD AIR SPILLING OVER LAKE MICHIGAN COMBINED WITH A LINGERING
INVERTED SURFACE TROUGH IS HELPING TO GENERATE LIGHT SNOW OVER
THE AREA. LAKE EFFECT SNOW IS EXPECTED TO INTENSIFY LATER THIS
EVENING AS CONVECTIVE DEPTHS INCREASE DUE TO CONTINUED CAA. IFR
CONDITIONS AND ACCUMULATIONS OF 1-3 INCHES ARE POSSIBLE AT KSBN.
LOW LEVEL WINDS WILL BACK TO A MORE WESTERLY DIRECTION BY LATER
TONIGHT...QUICKLY SHUTTING OFF LAKE EFFECT PRECIP. FORECAST
SOUNDINGS SUGGEST LOW LEVEL MOISTURE WILL REMAIN TRAPPED BENEATH A
LOWERING INVERSION THOUGH. THIS WOULD SUGGEST LOW END MVFR CIGS
CONTINUING THROUGH THE PERIOD BUT CONFIDENCE IN THIS ASPECT OF THE
FORECAST REMAINS LOW.
&&
.PREV DISCUSSION... /ISSUED 433 AM EST SAT DEC 29 2012/
SHORT TERM...
TODAY THROUGH SUNDAY NIGHT...KEPT THE WINTER WEATHER ADVISORY FOR
FAR SOUTHEAST AREAS GOING UNTIL 7 AM GIVEN THE LATEST SATELLITE AND
RADAR TRENDS. SURFACE OBS AND SURFACE REPORTS OF SNOWFALL
APPROACHING 4 INCHES IN VAN WERT COUNTY SUPPORT TOTAL SNOWFALL
AMOUNTS UP TO 5 INCHES. THE LATEST HRRR SUGGESTS THE SNOW MAY
LINGER A LITTLE LONGER THAN 7 AM THIS MORNING...BUT FOR NOW WILL
KEEP THE EXPIRATION TIME AT 7 AM AND EXTEND LATER IF NEEDED. BACK TO
THE NORTHWEST...LAKE EFFECT SNOW SHOWERS WERE JUST BEGINNING TO
DEVELOP OVER SOUTHERN LAKE MICHIGAN AND SHOULD CONTINUE TO EXPAND IN
COVERAGE. LAKE PARAMETERS NOT IMPRESSIVE...BUT SHOULD SUPPORT LAKE
EFFECT SNOW WITH LIGHT SNOW ACCUMULATIONS. MADE SOME ADJUSTMENTS
ACCORDING TO THE LATEST HIGH RES MODEL DATA TO LAKE EFFECT
TRAJECTORIES AND COVERAGE TODAY AND TONIGHT. OTHERWISE...AS FOR
TEMPERATURES...WENT WITH THE WARMER MET FOR LOWS TONIGHT AND HIGHS
SUNDAY.
LONG TERM...
PROGRESSIVE SPLIT FLW PATTN CONTS UNABATED YET REMAINS POTENTIALLY
PROBLEMATIC AS EVIDENT W/CURRENT SYS OVR THE TN VALLEY THIS MORNING.
GIVEN WORRISOME TREND TWD NEWD PLACEMENT OF DEEPER SRN STREAM WV AND
NWD POSITIONING OF DOWNSTREAM MID LVL CONFLUENCE ZONE SEEN IN ECMWF
AND IN TANDEM W/00Z NAM/UKMET WILL CAUTIOUSLY BREAK FM PRIOR
CONTINUITY WRT POPS MON-MON NIGHT W/CONSENSUS INDICATIONS OF AT
LEAST PARTIAL STREAM PHASING POSSIBLE.
HWVR GRADUAL BLDG OF NEG HGT ANOMALIES CNTRD OVR SE CANADA UPSTREAM
OF BLDG DOWNSTREAM BLOCK OVR GREENLAND AGAIN POINT TO INCREASING
POLAR WEDGING DVLPG MID-LATE PD. IN FACT MULTIDAY MEANS OF GFS MOS
GUIDANCE CONT W/A DOWNWARD TREND ESP THU-FRI PD IN WAKE OF POLAR
FNTL PASSAGE. SOME LK RESPONSE XPCD GIVEN DEGREE/DEPTH OF CAA WING
WED NIGHT AND THU. HWVR SWD CONSENSUS PLACEMENT OF SFC RIDGE CNTR
ACRS THE CNTRL PLAINS WOULD SUGGEST LIMITED RESPONSE IN FACE OF
GENERAL WRLY LL FETCH AND EXTREMELY DRY BNDRY LYR FEED OUT OF RIDGE.
THUS WILL KEEP W/TEMPERED POPS FOR THE TIME BEING. REGARDLESS GIVEN
CORRESPONDING AGREEMENT BTWN GFS/ECMWF WILL UNDERCUT THU/FRI TEMPS
FURTHER IN LIGHT OF BLDG LL THERMAL TROUGH ACRS THE NERN US.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 5 AM EST MONDAY
FOR LMZ043-046.
&&
$$
SHORT TERM...SKIPPER
LONG TERM...T
AVIATION...AGD
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
307 PM CST SAT DEC 29 2012
.SYNOPSIS...
THE MORNING UA ANALYSIS SHOWED AN UPPER TROF OVER THE CENTRAL U.S.
THE MAIN TROF AXIS EXTENDED FROM LAKE MICHIGAN THROUGH THE LOWER
OHIO VALLEY WITH A SECONDARY SHORT WAVE OVER WESTERN IOWA. AT THE
SURFACE THE REGION WAS UNDER CYCLONIC FLOW ASSOCIATED WITH LOW
PRESSURE OFF THE MID ATLANTIC COAST. WIDESPREAD LOW CLOUDS OVER THE
AREA THIS MORNING WERE ACCOMPANIED BY SOME LIGHT SNOW. THE CLOUDS
HAVE BEEN STEADILY CLEARING FROM WEST TO EAST THROUGH EARLY THIS
AFTERNOON.
&&
.SHORT TERM...TONIGHT AND SUNDAY...
EXTRAPOLATION OF THE CLEARING LINE HAS THE BACK EDGE OF THE LOW
CLOUDS EAST OF THE CWFA BY 03Z. THIS LOOKS REASONABLE...EXCEPT FOR
NORTHWEST ILLINOIS WHERE MODEL PROGS HOLD HIGHER VALUES OF LOW LEVEL
RH THROUGH MIDNIGHT AS THE LOW LEVEL RIDGE BUILDS INTO THAT AREA
FIRST. HAVE SET THE GRIDS UP FOR A FASTER CLEARING TREND OVER THE
SOUTHWEST HALF OF THE AREA THIS EVENING AND A LITTLE SLOWER TREND IN
THE NORTHEAST. THERE IS ALSO SOME CONCERN FOR STRATUS AND FOG
DEVELOPING JUST EAST OF THE RIDGE AXIS LATE TONIGHT...SIMILAR TO
WHAT HAPPENED IN EASTERN SOUTH DAKOTA THIS MORNING. THE RAP AND NAM
.5KM RH PROGS WERE HINTING AT THIS OCCURRING OVER EASTERN IA AFTER
MIDNIGHT. WHILE THIS CANNOT BE RULED OUT...THERE IS NOT ENOUGH
CONFIDENCE IN ITS OCCURRENCE TO INCLUDE IN THE FORECAST JUST YET.
CLEARING SKIES AND LIGHT WINDS TONIGHT SHOULD ALLOW FOR GOOD
RADIATIONAL COOLING WITH LOWS JUST BELOW ZERO NORTHWEST TO AROUND
10 IN THE SOUTHEAST. THE SURFACE RIDGE AXIS WILL BE EAST OF THE
AREA BY 12Z SUNDAY WITH SOUTH WINDS INCREASING DURING THE DAY AS THE
RIDGE CONTINUES TO MOVE EAST AND A COLD FRONT MOVES INTO NORTHWEST
IOWA. HIGH CLOUDS WILL ALSO BE ON THE INCREASE. TEMPERATURES WILL
BE A CHALLENGE TOMORROW WITH MODELS SHOWING A SHALLOW BUT STRONG
INVERSION OVER THE AREA. HIGHS IN THE MID 20S NORTH TO LOW 30S SOUTH
WERE BASED ON THE SHALLOW MIXING. IF WINDS ARE STRONGER THAN
FORECAST THEN...MIXING WILL BE DEEPER AND THE FORECAST HIGHS WILL BE
ON THE COLD SIDE. DLF
.LONG TERM...MONDAY THROUGH SATURDAY
TWO MAIN CONCERNS IN THIS TIME FRAME ARE THE WEAK CYCLOGENESIS
EVENT WHICH COULD BRING PRECIP TO THE SOUTH LATE MONDAY AND EARLY
TUESDAY...AND THE MUDDLE AMONGST THE MODELS WITH THE UPPER AIR
PATTERN AND SUBSEQUENT DETAILS MIDWEEK.
REGARDING THE MONDAY EVENT...THE NAM IS MORE VIGOROUS AND FURTHER
NORTH WITH DEVELOPING THE LOW THAN THE GFS AND ECMWF...WHICH ARE
WEAKER AND FURTHER SOUTH. HAVE SHADED POPS TO FAVOR THE GFS/ECMWF
SOLUTIONS AND KEPT QPF/SNOW ON THE LIGHT SIDE.
AT MID WEEK...THE EXTENDED MODELS ARE INCONSISTENT AMONG
THEMSELVES AND FROM RUN TO RUN IN HANDLING THE COMPLEX SPLIT FLOW
PATTERN WHICH INCLUDES A SOUTHWEST U.S. CUTOFF AND AN ACTIVE
NORTHERN STREAM. THE 12Z ECMWF MOVES A CLIPPER SYSTEM TO OUR
NORTHEAST WEDNESDAY-THURSDAY...WHICH IS FURTHER NORTH AND EAST AT
THAN AT 00Z WHEN IT WAS PROGGED OVER OUR AREA. MEANWHILE...THE
12Z GFS PROGS THIS CLIPPER SYSTEM FASTER AND EVEN FURTHER
NORTHEAST...SO IT APPEARS THIS WOULD BE A NONEVENT FOR US.
THE GFS DOES HOLD MORE ENERGY BACK OVER THE NORTHERN ROCKIES WHICH
EVENTUALLY CUTS OFF AND DRIFTS ACROSS THE CENTRAL U.S. THROUGH
THE WEEKEND. HOWEVER...THIS GFS RUN IS AN OUTLIER RELATIVE TO THE 00Z
ENSEMBLE MEAN.
THUS FAITH IN ANY OF THESE SOLUTIONS IS LOW. HOWEVER...THE COMMON
THEME IS THAT TROUGHINESS DEVELOPS AND PROGRESSES THROUGH THE
CENTRAL U.S. LATE NEXT WEEK. THERE APPEARS TO BE NO SIGNIFICANT
PRECIP EVENT IN THIS TIME FRAME...AND INDICATIONS ARE THAT
REENFORCING COLD AIR MIGHT GIVE US OUR COLDEST TEMPS SO FAR THIS
SEASON SOMETIME LATE NEXT WEEK INTO THE WEEKEND. WOLF
&&
.AVIATION...
THE BACK EDGE OF THE MVFR CIGS HAS ALREADY CLEARED KCID AND KBRL
WITH THE CURRENT MOVEMENT SUGGESTING CLEARING AT KMLI AROUND 23Z.
MODEL RH PROGS ARE SUGGESTING KDBQ MAY CLEAR OUT SLOWER THAN THE
REST OF THE AREA...SO HELD CEILINGS IN THERE THROUGH MID EVENING.
A SURFACE RIDGE AXIS CURRENTLY OVER EASTERN NEBRASKA AND EASTERN
SOUTH DAKOTA WILL MOVE INTO EASTERN IOWA BY LATE TONIGHT. LATEST
OBSERVATIONS AND SATELLITE IMAGERY WERE SHOWING A NARROW BAND OF
LIFR CIGS AND VSBYS JUST EAST OF THE RIDGE IN EASTERN SOUTH DAKOTA.
SHORT RANGE MODEL GUIDANCE WAS HINTING THAT THESE LOW CLOUDS/FOG
COULD MOVE INTO EASTERN IA WITH THE RIDGE AXIS LATE TONIGHT. THESE
CONDITIONS WERE NOT INCLUDED IN THE TERMINAL FORECASTS JUST YET BUT
MAY BE DURING LATER UPDATES IF TRENDS SUPPORT THEIR INCLUSION.
DLF
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
DLF/WOLF
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1151 AM CST SAT DEC 29 2012
.UPDATE...
GRIDS WERE UPDATED EARLIER TO EMPHASIZE THE LIGHT SNOW MORE AND TO
DELAY CLEARING UNTIL THE OVERNIGHT HOURS. LIGHT SNOW WAS OCCURRING
WEST INTO CENTRAL IA THIS MORNING AND ALSO NORTHWEST INTO
SOUTHEAST MN WITH VISIBILITIES AT TIMES UNDER 3 MILES. BASED ON
THESE UPSTREAM CONDITIONS WE SHOULD CONTINUE TO SEE SOME
INTERMITTENT LIGHT SNOW AT MOST LOCATIONS THROUGH MOST OF THIS
AFTERNOON AND PICKING UP A TENTH OR TWO TENTHS OF INCH AT SOME
LOCATIONS IS NOT OUT OF THE QUESTION. ALSO BASED ON CURRENT TRENDS
OVER WESTERN IOWA AND THE RAP .5KM RH PROGS...HAVE SLOWED THE
CLEARING TREND DOWN WITH MOST OF THE AREA CLEARING THIS EVENING OR
JUST AFTER MIDNIGHT. AN AREA OF STRATUS/FOG OVER EASTERN SOUTH
DAKOTA AND JUST EAST OF THE SURFACE RIDGE AXIS WILL HAVE HAVE TO
BE WATCHED AS A SPOILER TO THE CLEARING. THESE CLOUDS WERE
EXPANDING TO THE SOUTHEAST THIS MORNING AND THE RAP CLOUD BASE
PRODUCT WAS HINTING AT LOW CEILINGS OVER EASTERN IOWA LATE TONIGHT
AS THE RIDGE AXIS MOVES IN. DLF
&&
.AVIATION...
MVFR CIGS WITH SNOW SHOWERS DROPPING VISIBILITIES TO AROUND 3
MILES AT TIMES CAN BE EXPECTED THROUGH THIS AFTERNOON. TIMING OF THE
BACK EDGE OF THE MVFR CLOUDS SUGGESTS CLEARING AT MOST TAFS SITES
THIS EVENING. HOWEVER...KDBQ MAY BE THE EXCEPTION WITH MODEL LOW
LEVEL RH FIELDS KEEPING HIGHER RH VALUES OVER NORTHEAST
IOWA/NORTHWEST ILLINOIS INTO THE OVERNIGHT HOURS. A SURFACE RIDGE
AXIS CURRENTLY OVER EASTERN NEBRASKA AND EASTERN SOUTH DAKOTA WILL
MOVE INTO EASTERN IOWA BY LATE TONIGHT. LATEST OBSERVATIONS AND
SATELLITE IMAGERY WERE SHOWING A NARROW BAND OF LIFR CIGS AND
VSBYS JUST EAST OF THE RIDGE IN EASTERN SOUTH DAKOTA. SHORT RANGE
MODEL GUIDANCE WAS HINTING THAT THESE LOW CLOUDS/FOG COULD MOVE
INTO EASTERN IA WITH THE RIDGE AXIS LATE TONIGHT. THESE CONDITIONS
WERE NOT INCLUDED IN THE TERMINAL FORECASTS JUST YET BUT MAY BE
DURING LATER UPDATES IF TRENDS SUPPORT THEIR INCLUSION.
DLF
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
406 PM EST SAT DEC 29 2012
.SHORT TERM...THIS EVENING AND TONIGHT
SURFACE OBSERVATIONS UPSTREAM OVER NORTHERN LAKE HURON SUPPORT THE
MAIN STRUCTURE OF LAKE HURON AGGREGATE TROUGH HAS BROKEN DOWN. HIGH
RESOLUTION MODEL DATA HAS BEEN DEPICTING A SOLUTION THAT SUPPORTED
TRACKING A MESOVORTEX OR WELL ORGANIZED LOW LEVEL CONVERGENCE BANDING
STRUCTURE INTO PORTIONS OF HURON COUNTY AND THE NORTHERN THUMB AS
THE NORTHWESTERLY FLOW BECAME DOMINANT. WITH NO REDUCTION IN SFC
VISIBILITIES EARLIER THIS AFTERNOON FOR THE UPSTREAM SHORELINE AREAS
OF NORTHERN LOWER THIS IDEA FOR A MESOLOW CAN NOW BE ABANDONED. THIS
IS IMPORTANT BECAUSE THE IDEA OF LONGER DURATION DUE TO PROPAGATION
EFFECTS CAN BE APTLY BE DISCOUNTED AS WELL.
THE LAKE EFFECT EVENT NOW ANTICIPATED WILL BE A BRIEF
ONE...RELEGATED TO DEVELOPED ACTIVITY ADVECTING THROUGH ON THE LEAD
BACKED NORTHEASTERLY PUSH...VERY MUCH OF A SQUALL NATURE. SATELLITE
IMAGERY HAS SHOWN LOW CLOUD STRATOCUMULUS AGGRESSIVELY PUSHING INTO
EASTERN HURON COUNTY/MARKED WITH A GRAVITY STRUCTURE DURING THE PAST
HOUR. KDTX/KAPX BEAMS ARE BOTH OVERSHOOTING THE ACTIVITY WITH THE
AREAS OF INTEREST AT ROUGHLY 90 NM OR APPX 10 KFT AGL ON THE .5
DEGREE. ENVIRONMENT CANADA EXETER RADAR IS IN A BETTER LOCATION AND
IS SHOWING 25-30 DBZ EXTENDING INLAND/EAST OF BAD AXE. PLACED SOME
CALLS TO FIELD REPORTS AND DID MANAGE TO GET A CREDIBLE REPORT OF .5
INCH PER ONE HALF HOUR IN PORT HOPE. HOWEVER...THE SNOW HAD ALREADY
BEEN ON THE WANE SUGGESTING A TENUOUS SETUP. VARIOUS HI RESOLUTION
FLAVORS OF NWP - 3.5KM ARW WRF - 4 KM NMM SPC WRF - 3KM HRRR AND 13
KM RAP NOW AGREE IN SWEEPING THIS LAKE EFFECT THROUGH DURING 19-22Z.
DURATION OF SNOWFALL SHOULD ONLY LAST 1-1.5 HOUR AT MOST BEFORE
PUSHING BACK INTO LAKE HURON. THEREFORE...THE FORECAST WILL CALL FOR
A CONDITIONAL...UP TO 2 INCHES FOR LOCATIONS OF HURON/SANILAC
COUNTIES EAST OF A LINE FROM BAD AXE TO SANDUSKY.
OTHERWISE...LARGE SCALE MIDLEVEL TROUGH IS NOW ADVANCING INTO THE
WESTERN PORTIONS OF LOWER MICHIGAN. THE OLD 850-700MB DEFORMATION
FORCING THAT IS A CARRYOVER FROM LAST NIGHT HAS BEEN EFFICIENT IN
GENERATING AFTERNOON LIGHT SNOW/FLURRIES HERE ACROSS MUCH OF THE
REGION. HIGHEST REFLECTIVITIES HAVE BEEN IN EXCESS OF 20 DBZ BUT IS
LACKING IN ANY BITE/MORE OF A FUNCTION OF A FEW LARGE FLAKES. NOT
EXPECTING MUCH ACCUMULATION WITH THIS BEFORE DISSIPATING.
LOWS TONIGHT ARE VERY TRICKY AND DEPENDENT ON CLOUD COVER. DID STEER
THE FORECASTED LOWS A LITTLE TOWARDS RECENT GUIDANCE...AROUND 20
DEGREES.
&&
.LONG TERM...SUNDAY THROUGH SATURDAY
QUIET WEATHER EXPECTED SUNDAY/SUNDAY NIGHT AS HIGH PRESSURE BUILDS
ACROSS THE EASTERN CONUS W/ THE NORTHERN EXTENT OF SURFACE RIDGING
PROVIDING RELATIVELY LIGHT WINDS AND PARTLY CLOUDY SKIES FOR THE
SOUTHERN GREAT LAKES. AS THE RIDGE AXIS PROGRESSES EAST OF THE AREA
ON MONDAY...CLOUDS/WINDS WILL INCREASE WITH THE APPROACH OF THE NEXT
DISTURBANCE. THIS SYSTEM WILL CROSS NORTH OF THE AREA...BUT PUSH A
COLD FRONT THROUGH THE REGION BY MONDAY NIGHT.
THE STORM SYSTEM THAT HAS BASICALLY THE ONLY POTENTIAL TO BRING
NOTEWORTHY SNOW TO THE AREA IS CURRENTLY SPINNING OVER CALIFORNIA.
OF THE 12Z MODEL SUITE...THE NAM12 IS THE ONLY MODEL TRYING TO
MAINTAIN SOME INTEGRITY TO THIS WAVE AS IT EJECTS NORTHEAST OUT OF
THE FOUR CORNERS ALONG THE MEAN CENTRAL CONUS UPPER TROUGH INTO A
LARGELY CONFLUENT UPPER FLOW OVER THE NORTHEAST QUADRANT OF THE
NATION.
IN ADDITION TO SHOWING THE STRONGEST SOLUTION FOR THIS SHORTWAVE
ITSELF...THE OTHER MAIN DIFFERENCE IS THE HANDLING OF SHORTWAVE
ENERGY DIGGING SOUTH/SOUTHEAST INTO POLAR VORTEX NEAR HUDSON BAY AS
THE NAM..THROUGH THIS PROCESS...MAINTAINS A MORE NORTHERN POSITION
TO THIS FEATURE AND ALLOWS ITS "STRONGER" WAVE TO EJECT FURTHER
NORTH INTO THE OHIO VALLEY/SOUTHERN GREAT LAKES AND BRING SEVERAL
INCHES OF SNOW TO PARTS OF LOWER MICHIGAN.
WHILE THE ARCTIC JET ENERGY THAT WILL EVENTUALLY DICTATE THE
EVOLUTION OF THE HUDSON BAY LOW AND THE STEERING OF THE SOUTHERN
STREAM WAVE HAS YET TO BE SAMPLED VERY WELL...IT IS HARD TO IGNORE
SUCH A STRONG MODEL CONSENSUS AGAINST THE NAM...WHICH CALLS FOR
STRONGER AMPLIFICATION OF THE NORTHERN STREAM OVER EASTERN CANADA.
THIS SCENARIO WILL SHUNT THE SOUTHERN SYSTEM ON A TRACK WELL SOUTH
OF THE AREA AND KEEP ANY NOTABLE PRECIPITATION CONFINED TO THE
TENNESSEE VALLEY AND POINTS SOUTH WITH IT WITH JUST SCATTERED SNOW
SHOWERS OVER LOWER MICHIGAN WITHIN THE CYCLONIC NORTHWEST FLOW AS
COLDER AIR SURGES THROUGH THE GREAT LAKES WITH THE EVOLUTION OF THIS
NORTHERN SYSTEM.
WILL MAINTAIN A FORECAST BASED ON THIS IDEA...WITH LITTLE/NO CHANCE
OF SIGNIFICANT SNOW AND ALSO A DECENT COOL DOWN AS THIS STRONG
EASTERN CANADA UPPER LOW/TROUGH ALLOWS FOR A DECENT PENETRATION OF
POLAR/MODIFIED ARCTIC AIR INTO THE REGION. SO...AFTER EDGING BACK TO
HIGH TEMPERATURES IN THE 30S ON MONDAY...20S WILL BE THE RULE MUCH
OF THE UPCOMING WEEK WITH LOWS IN THE SINGLE DIGITS/TEENS MUCH OF
THE TIME.
&&
.MARINE...
A MODEST INCREASE TO THE SURFACE PRESSURE GRADIENT COMBINED WITH
WINDS ROTATING TO A MORE ONSHORE DIRECTION WILL MAINTAIN A MODERATE
BREEZE ACROSS CENTRAL AND SOUTHERN LAKE HURON TODAY. WAVE HEIGHTS
ARE ALREADY RAMPING UP INTO THE 4 TO 7 FOOT RANGE THIS AFTERNOON.
SMALL CRAFT ADVISORIES REMAIN IN EFFECT FROM OUTER SAGINAW BAY TO
PORT HURON THROUGH TONIGHT.
A MODERATE SOUTHWEST FLOW WILL DEVELOP SUNDAY NIGHT INTO MONDAY AS
THE SURFACE PRESSURE GRADIENT TIGHTENS OVER AREA WATERS AS LOW
PRESSURE CROSSES NORTH OF THE REGION. GUSTY NORTHWEST WINDS WILL
DEVELOP BY MIDWEEK NEXT WEEK AS COLDER AIR SPREADS INTO THE GREAT
LAKES REGION IN THE WAKE OF THIS SYSTEM.
&&
.AVIATION...ISSUED 1234 PM EST SAT DEC 29 2012
//DISCUSSION...
RESIDUAL MIDLEVEL DYNAMICS FROM AN EARLIER FRONTAL ZONE IS NOW
ADVECTING INTO SOUTHERN PORTIONS OF SOUTHEASTERN MICHIGAN FROM THE
NORTHWEST. FOR NOW...FLOW TRAJECTORY AND LATEST TRENDS SUGGESTS
PRECIPITATION WILL NOT IMPACT KFNT AND KMBS. BEHAVIOR OF BASE
REFLECTIVITY PRODUCTS HAS BEEN INTERESTING...SUGGESTING THAT
SEEDER FEEDER PROCESSES ARE IN PLAY TO HELP GENERATE A MODESTLY
BURGEONING AREA OF LIGHT SNOW. LACK OF ANY TANGIBLE DRY AIR
ADVECTION FOLLOWING LAST NIGHTS SYSTEM CERTAINLY SUPPORTS THIS
IDEA. EXPECTATIONS ARE FOR A PERIOD OF MVFR TYPE SNOW ACTIVITY
WITH SOME IFR VISIBILITIES RESULTING DUE TO THE ADDITION OF BR/HZ.
THE LAKE EFFECT SNOW ACTIVITY THAT IS EXPECTED TO CRASH INTO
PORTIONS OF THE THUMB LATER ON...SHOULD BE SUBSEQUENTLY SWEPT
EASTWARD. PERSISTENT NORTHWESTERLY...CYCLONIC FLOW SUPPORTS
STRATOCUMULUS THROUGHOUT THE TAF CYCLE.
FOR DTW...MVFR TO OCCASIONAL IFR VISBY LIGHT SNOW IS EXPECTED OVER
THE NEXT 3 TO 4 HOURS. THE REASON FOR IFR VISBY IS DUE TO THE
PERSISTENCE OF BR/HZ. CEILING HEIGHTS ARE EXPECTED TO REMAIN MVFR
THROUGHOUT THE PERIOD. MODEL DATA IS SUGGESTING IFR CEILING HEIGHTS
LATE TONIGHT/TOMORROW MORNING BUT ATTM...SUSPECT THE MODELS ARE
OVERDONE ON THE AMOUNT OF NEAR SURFACE MOISTURE.
//DTW THRESHOLD THREATS...
* HIGH CONFIDENCE CEILINGS WILL BE BELOW 5000 FT.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...OUTER SAGINAW BAY...UNTIL 1 AM SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
SANILAC...UNTIL 7 AM SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT SANILAC TO PORT
HURON...FROM 10 PM SATURDAY TO 10 AM SUNDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
SHORT TERM...CB
LONG TERM....DG
MARINE.......CB
AVIATION.....CB
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
356 PM EST SAT DEC 29 2012
.SYNOPSIS...
ISSUED AT 321 PM EST SAT DEC 29 2012
ANOTHER ROUND OF MOSTLY LIGHT SNOW WILL OCCUR OVERNIGHT. UP TO AN
INCH OR TWO OF ACCUMULATION WILL BE POSSIBLE ALONG THE LAKESHORE
NEAR SOUTH HAVEN. AFTER A RATHER DRY SUNDAY AND SUNDAY NIGHT...THE
COMING WORK WEEK WILL BE COLDER THAN NORMAL WITH SLIGHT CHANCES FOR
SNOW MAINLY NEAR THE LAKE SHORE EACH DAY.
&&
.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 321 PM EST SAT DEC 29 2012
AS NOTED IN THE PREVIOUS FORECAST UPDATE DISCUSSION...WE EXPECT
A SHOT OF LAKE ENHANCED SNOW EARLY TONIGHT MAINLY SOUTH OF HOLLAND.
THE BEST TIMEFRAME LOOKS BETWEEN 10 PM AND 2 AM. MOST RECENT RUNS
OF THE RAP HAVE BACKED TOTAL ACCUMULATIONS AT SOUTH HAVEN DOWN TO AN
INCH OR LESS COMPARED TO EARLIER AMOUNTS OF 2+ INCHES. HOWEVER...
PREFER TO MATCH UP WITH SLIGHTLY HIGHER AMOUNTS ADVERTISED BY IWX TO
ACCOUNT FOR LAKE MOISTURE THAT MAY NOT BE HANDLED WELL BY THE MODELS.
OTHERWISE...FEW CHANGES WERE MADE TO THE FORECAST. DID RAISE POPS
AND SNOW AMOUNTS MONDAY AND MONDAY NIGHT OVER OUR NRN ZONES TO
ACCOUNT FOR COLD FRONT DROPPING SOUTH THROUGH THE AREA AND TO BETTER
MATCH WITH APX TO OUR NORTH.
.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 321 PM EST SAT DEC 29 2012
THE FOCUS OF THE FORECAST CONTINUES TO BE CENTERED ON THE ARCTIC AIR
MASS THAT IS EXPECTED TO COME DOWN AND THE RESULTING LAKE EFFECT
SNOW SHOWER CHCS.
TUE AND TUE NIGHT LOOK RATHER QUIET. SOME LIGHT LAKE EFFECT WILL BE
POSSIBLE ON TUE AS WE SHOULD SEE A WEAK UPPER TROUGH MOVE BY.
SUFFICIENT INSTABILITY OVER THE LAKE WILL ALSO BE PRESENT WITH H850
TEMPS AROUND -10 TO -12C. THE LAKE EFFECT POTENTIAL WILL DIMINISH
LATE TUE AND MAINLY DRY CONDITIONS ARE EXPECTED TUE NIGHT WITH
RIDGING BUILDING IN.
WE ARE STILL EXPECTING A FAIRLY VIGOROUS UPPER TROUGH TO DROP DOWN
IN THE REGION WED-THU. THIS WILL BRING A THREAT OF SYNOPTIC SNOW
ALONG WITH SOME LAKE ENHANCEMENT/POTENTIAL AS COLDER AIR WILL FOLLOW
IN BEHIND IT. THE MODELS HAVE BEEN STRUGGLING WITH THE EXACT TRACK
WHICH WILL HAVE IMPLICATIONS ON HOW MUCH SNOW FALLS AND WHERE IT
FALLS. THE LATEST MODELS SHOW IT TRACKING NORTH OF THE AREA AND
HAVING MOST OF THE SNOW NORTH OF IT. THE FLOW IS ALSO IMPORTANT DUE
TO LAKE ENHANCEMENT POTENTIAL. FOR NOW WE HAVE A CHC OF SNOW SHOWERS
EVERYWHERE. THIS WILL HAVE TO BE FINE TUNED.
THE NOTEWORTHY CHANGE IN THE MODELS IS A TREND TOWARD A SHORTER STAY
FOR THE ARCTIC AIR. THE MODELS ARE MORE PROGRESSIVE THAN PREVIOUS
RUNS WITH THE UPPER TROUGH AND ARCTIC AIR. THIS IS LIKELY HAVING TO
DO WITH THE SPLIT FLOW THAT DEVELOPS. THE UPPER TROUGH IS EXPECTED
TO BE GONE BY THU NIGHT. THIS WOULD MEAN LESS LAKE EFFECT POTENTIAL.
BY FRI...THE AIR AT H850 IS NOT EVEN COLD ENOUGH FOR LAKE EFFECT. WE
END UP ONCE AGAIN IN NO MANS LAND BETWEEN THE JET STREAMS. THIS
WOULD BRING US SEASONABLE TEMPERATURES WITH LITTLE IF ANY PCPN CHCS.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1250 PM EST SAT DEC 29 2012
THE TWO MAIN ITEMS OF INTEREST WITH THIS SET OF FCSTS IS THE
CURRENT SNOW MOVING OUT THIS AFTERNOON AND THEN LAKE EFFECT TRENDS
FOR TONIGHT AND TOMORROW.
THE AREA OF LIGHT SNOW WAS SOUTHEAST OF A LINE FROM KALAMAZOO TO
GRAND RAPIDS TO ALMA AS OF 1745Z THIS AFTERNOON. THIS SNOW IS
PRODUCING LOW MVFR TO IFR CONDITIONS. THIS IS EXPECTED TO MOVE OUT
TO THE SE OF ALL THE TERMINALS BY AROUND 21Z THIS AFTERNOON. SOME
SCATTERED VFR CONDITIONS ARE POSSIBLE BEHIND THE SNOW FOR A SHORT
TIME. MORE MVFR CIGS AROUND 2500 FT ACROSS CENTRAL LOWER MICHIGAN
WILL MOVE IN LATER THIS AFTERNOON.
LAKE EFFECT SNOW SHOWERS WILL GRADUALLY MOVE IN LATE THIS
AFTERNOON AND MORE SO TONIGHT AS NNE WINDS GRADUALLY SHIFT TO THE
WEST OVERNIGHT TONIGHT. LAKE EFFECT WILL SPREAD ACROSS THE
LAKESHORE FIRST LATE AFTERNOON/EARLY EVENING...THEN INLAND
THEREAFTER. MAINLY MVFR CIGS AND VSBYS ARE EXPECTED WITH SOME SPOTTY
IFR POSSIBLE CLOSER TO THE LAKESHORE. SNOW SHOWERS WILL SLOWLY
DIMINISH THROUGH 18Z SUN THEN BEFORE ENDING AFTER THE TAF PERIOD.
&&
.MARINE...
ISSUED AT 351 PM EST SAT DEC 29 2012
NO CHANGES WERE MADE TO THE INHERITED FORECAST. LATEST LOCAL RUN
OF THE GLERL KEEPS WAVES BELOW SMALL CRAFT CRITERIA UNTIL WELL
AFTER MIDNIGHT. THIS IS A FEW HOURS AFTER THE 10 PM OFFICIAL START
OF THE SMALL CRAFT ADVISORY. THERE MAY BE A BRIEF PERIOD OF SUB-
ADVISORY WAVES SUNDAY AFTERNOON. HOWEVER THIS WILL BE SHORT-LIVED
AS WINDS NEAR OR AT GALE FORCE ARE EXPECTED BOTH SUNDAY NIGHT AND
MONDAY.
&&
.HYDROLOGY...
ISSUED AT 321 PM EST SAT DEC 29 2012
NO HYDRO CONCERNS DUE TO VERY LITTLE QPF. RIVER ICE WILL BE LIKELY
TO DEVELOP BY THE END OF THE COMING WORK WEEK.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST SUNDAY
FOR LMZ844>849.
&&
$$
SYNOPSIS...TJT
SHORT TERM...TJT
LONG TERM...NJJ
AVIATION...NJJ
HYDROLOGY...TJT
MARINE...TJT
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
321 PM EST SAT DEC 29 2012
.SYNOPSIS...
ISSUED AT 321 PM EST SAT DEC 29 2012
ANOTHER ROUND OF MOSTLY LIGHT SNOW WILL OCCUR OVERNIGHT. UP TO AN
INCH OR TWO OF ACCUMULATION WILL BE POSSIBLE ALONG THE LAKESHORE
NEAR SOUTH HAVEN. AFTER A RATHER DRY SUNDAY AND SUNDAY NIGHT...THE
COMING WORK WEEK WILL BE COLDER THAN NORMAL WITH SLIGHT CHANCES FOR
SNOW MAINLY NEAR THE LAKE SHORE EACH DAY.
&&
.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 321 PM EST SAT DEC 29 2012
AS NOTED IN THE PREVIOUS FORECAST UPDATE DISCUSSION...WE EXPECT
A SHOT OF LAKE ENHANCED SNOW EARLY TONIGHT MAINLY SOUTH OF HOLLAND.
THE BEST TIMEFRAME LOOKS BETWEEN 10 PM AND 2 AM. MOST RECENT RUNS
OF THE RAP HAVE BACKED TOTAL ACCUMULATIONS AT SOUTH HAVEN DOWN TO AN
INCH OR LESS COMPARED TO EARLIER AMOUNTS OF 2+ INCHES. HOWEVER...
PREFER TO MATCH UP WITH SLIGHTLY HIGHER AMOUNTS ADVERTISED BY IWX TO
ACCOUNT FOR LAKE MOISTURE THAT MAY NOT BE HANDLED WELL BY THE MODELS.
OTHERWISE...FEW CHANGES WERE MADE TO THE FORECAST. DID RAISE POPS
AND SNOW AMOUNTS MONDAY AND MONDAY NIGHT OVER OUR NRN ZONES TO
ACCOUNT FOR COLD FRONT DROPPING SOUTH THROUGH THE AREA AND TO BETTER
MATCH WITH APX TO OUR NORTH.
.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 321 PM EST SAT DEC 29 2012
THE FOCUS OF THE FORECAST CONTINUES TO BE CENTERED ON THE ARCTIC AIR
MASS THAT IS EXPECTED TO COME DOWN AND THE RESULTING LAKE EFFECT
SNOW SHOWER CHCS.
TUE AND TUE NIGHT LOOK RATHER QUIET. SOME LIGHT LAKE EFFECT WILL BE
POSSIBLE ON TUE AS WE SHOULD SEE A WEAK UPPER TROUGH MOVE BY.
SUFFICIENT INSTABILITY OVER THE LAKE WILL ALSO BE PRESENT WITH H850
TEMPS AROUND -10 TO -12C. THE LAKE EFFECT POTENTIAL WILL DIMINISH
LATE TUE AND MAINLY DRY CONDITIONS ARE EXPECTED TUE NIGHT WITH
RIDGING BUILDING IN.
WE ARE STILL EXPECTING A FAIRLY VIGOROUS UPPER TROUGH TO DROP DOWN
IN THE REGION WED-THU. THIS WILL BRING A THREAT OF SYNOPTIC SNOW
ALONG WITH SOME LAKE ENHANCEMENT/POTENTIAL AS COLDER AIR WILL FOLLOW
IN BEHIND IT. THE MODELS HAVE BEEN STRUGGLING WITH THE EXACT TRACK
WHICH WILL HAVE IMPLICATIONS ON HOW MUCH SNOW FALLS AND WHERE IT
FALLS. THE LATEST MODELS SHOW IT TRACKING NORTH OF THE AREA AND
HAVING MOST OF THE SNOW NORTH OF IT. THE FLOW IS ALSO IMPORTANT DUE
TO LAKE ENHANCEMENT POTENTIAL. FOR NOW WE HAVE A CHC OF SNOW SHOWERS
EVERYWHERE. THIS WILL HAVE TO BE FINE TUNED.
THE NOTEWORTHY CHANGE IN THE MODELS IS A TREND TOWARD A SHORTER STAY
FOR THE ARCTIC AIR. THE MODELS ARE MORE PROGRESSIVE THAN PREVIOUS
RUNS WITH THE UPPER TROUGH AND ARCTIC AIR. THIS IS LIKELY HAVING TO
DO WITH THE SPLIT FLOW THAT DEVELOPS. THE UPPER TROUGH IS EXPECTED
TO BE GONE BY THU NIGHT. THIS WOULD MEAN LESS LAKE EFFECT POTENTIAL.
BY FRI...THE AIR AT H850 IS NOT EVEN COLD ENOUGH FOR LAKE EFFECT. WE
END UP ONCE AGAIN IN NO MANS LAND BETWEEN THE JET STREAMS. THIS
WOULD BRING US SEASONABLE TEMPERATURES WITH LITTLE IF ANY PCPN CHCS.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1250 PM EST SAT DEC 29 2012
THE TWO MAIN ITEMS OF INTEREST WITH THIS SET OF FCSTS IS THE
CURRENT SNOW MOVING OUT THIS AFTERNOON AND THEN LAKE EFFECT TRENDS
FOR TONIGHT AND TOMORROW.
THE AREA OF LIGHT SNOW WAS SOUTHEAST OF A LINE FROM KALAMAZOO TO
GRAND RAPIDS TO ALMA AS OF 1745Z THIS AFTERNOON. THIS SNOW IS
PRODUCING LOW MVFR TO IFR CONDITIONS. THIS IS EXPECTED TO MOVE OUT
TO THE SE OF ALL THE TERMINALS BY AROUND 21Z THIS AFTERNOON. SOME
SCATTERED VFR CONDITIONS ARE POSSIBLE BEHIND THE SNOW FOR A SHORT
TIME. MORE MVFR CIGS AROUND 2500 FT ACROSS CENTRAL LOWER MICHIGAN
WILL MOVE IN LATER THIS AFTERNOON.
LAKE EFFECT SNOW SHOWERS WILL GRADUALLY MOVE IN LATE THIS
AFTERNOON AND MORE SO TONIGHT AS NNE WINDS GRADUALLY SHIFT TO THE
WEST OVERNIGHT TONIGHT. LAKE EFFECT WILL SPREAD ACROSS THE
LAKESHORE FIRST LATE AFTERNOON/EARLY EVENING...THEN INLAND
THEREAFTER. MAINLY MVFR CIGS AND VSBYS ARE EXPECTED WITH SOME SPOTTY
IFR POSSIBLE CLOSER TO THE LAKESHORE. SNOW SHOWERS WILL SLOWLY
DIMINISH THROUGH 18Z SUN THEN BEFORE ENDING AFTER THE TAF PERIOD.
&&
.MARINE...
ISSUED AT 321 PM EST SAT DEC 29 2012
NO CHANGES WERE MADE TO THE INHERITED FORECAST. LATEST LOCAL RUN OF
THE GLERL KEEPS WAVES BELOW SMALL CRAFT CRITERIA UNTIL WELL AFTER
MIDNIGHT. THIS IS A FEW HOURS AFTER THE 10 PM OFFICIAL START OF
THE SMALL CRAFT ADVISORY. A SUNDAY AFTERNOON EXPIRATION STILL
LOOKS ON TRACK.
&&
.HYDROLOGY...
ISSUED AT 321 PM EST SAT DEC 29 2012
NO HYDRO CONCERNS DUE TO VERY LITTLE QPF. RIVER ICE WILL BE LIKELY
TO DEVELOP BY THE END OF THE COMING WORK WEEK.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST SUNDAY
FOR LMZ844>849.
&&
$$
SYNOPSIS...TJT
SHORT TERM...TJT
LONG TERM...NJJ
AVIATION...NJJ
HYDROLOGY...TJT
MARINE...TJT
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
1250 PM EST SAT DEC 29 2012
.SYNOPSIS...
ISSUED AT 330 AM EST SAT DEC 29 2012
A FEW LIGHT SNOW SHOWERS AND FLURRIES WILL LINGER THIS MORNING WITH
LIGHT LAKE EFFECT SNOW SHOWERS EXPECTED TONIGHT INTO SUNDAY MORNING.
TEMPERATURES WILL AVERAGE BELOW NORMAL THROUGH THE COMING WEEK WITH
SEVERAL CHANCES FOR SNOW SHOWERS AND A SHOT OF MUCH COLDER AIR
EXPECTED FOR LATE WEEK.
&&
.UPDATE...
ISSUED AT 1125 AM EST SAT DEC 29 2012
UPDATED FORECASTS TO LOWER POPS NORTH OF I-96. HAVE ALSO DECREASED
POPS INTO THIS EVENING ALONG THE INTERIOR I-94 CORRIDOR. WE ARE
LOOKING FOR A QUICK BURST OF LAKE ENHANCED SNOW MAINLY BEFORE
MIDNIGHT MAINLY SOUTH OF HOLLAND THAT COULD ADD AN INCH OR SO NEAR
THE LAKESHORE.
RADAR LOOP INDICATES PRESENCE OF A SURFACE MESOLOW OVER
SOUTHEASTERN LAKE MICHIGAN THAT IS WEAKENING AND MOVING SOUTHEAST
TOWARDS SOUTH HAVEN. MESOSCALE SUBSIDENCE BEHIND THIS FEATURE IS
RESULTING IN A SHARP TRAILING EDGE TO THE SNOW THAT IS APPROACHING
I-96 FROM THE NORTH. TO THE WEST...A WEAK N-S UPPER POT VORT LOBE
NOTED ON WATER VAPOR IMAGERY IS CROSSING IA/MN AT THIS TIME AND
SHOULD IMPACT THE CWFA THIS EVENING AT ITS CURRENT RATE OF SPEED.
LATEST RAP SNOW TOOL GUIDANCE FOR SOUTH HAVEN (LWA) SUGGESTS THAT 1
TO 2 INCHES OF SNOW COULD FALL IN THE 9 PM - 1 AM TIME FRAME
THERE.
UPDATE
ISSUED AT 704 AM EST SAT DEC 29 2012
I HAVE UPDATED THE FORECAST TO ALLOW THE SNOW BAND JUST NOW MOVING
INTO THE I-96 AREA TO CONTINUE TO MOVE SOUTH OVER TIME. THIS IS
REALLY A WEAK COLD FRONT THAT IS MOVING SOUTH WITH TIME BEHIND THE
DEPARTING STORM. THE NAM SHOWS SOME WEAK LIFT IN THE DGZ AS THIS
FEATURE MOVES SOUTH WITH TIME. IT DOES TAKE IT`S TIME THROUGH BY
21Z THERE IS STILL LIFT OVER OUR SE CWA WITH THIS FEATURE. ONCE
THE FEATURE MOVES SOUTH THE SNOW WILL END FROM NORTH TO SOUTH BUT
IT MAY TAKE UNTIL NOON OR SO FOR IT TO END BY INTERSTATE 96 AND
LATER BY INTERSTATE 94. ACCUMULATIONS WILL LIMITED AS LIFT IS
FEEBLE AND CURRENT VISIBILITIES ARE IN THE 3 TO 6 MILE RANGE.
&&
.SHORT TERM...(TODAY THROUGH MONDAY AFTERNOON)
ISSUED AT 330 AM EST SAT DEC 29 2012
A FEW LIGHT SNOW SHOWERS AND FLURRIES WILL LINGER THIS MORNING.
STEADIER SYNOPTIC LIGHT SNOW WILL CLIP OUR EXTREME SE FCST AREA OVER
TOWARD JXN THIS MORNING AND EARLY AFTERNOON. LIGHT SNOW BEGAN IN JXN
ABOUT AN HOUR AGO AND VERY LIGHT ACCUMULATIONS OF UNDER AN INCH ARE
ANTICIPATED THERE.
AN UPPER LEVEL DISTURBANCE WILL BRING LAKE ENHANCED LIGHT SNOW
SHOWERS AND FLURRIES TONIGHT INTO SUNDAY MORNING BUT WITH LITTLE IF
ANY ACCUMULATIONS. A HIGH PRESSURE RIDGE WILL BRING FAIR WX SUNDAY
AFTERNOON THROUGH SUNDAY NIGHT BEFORE AN APPROACHING COLD FRONT
BRINGS A CHC OF LIGHT SNOW SHOWERS MONDAY.
.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 330 AM EST SAT DEC 29 2012
THE MAIN FOCUS OF THE LONG TERM PORTION OF THE FCST WILL BE ON THE
ARCTIC AIR MASS THAT IS EXPECTED TO COME DOWN LATER NEXT WEEK AND
THE LAKE EFFECT POTENTIAL WITH IT. THERE IS ALSO SOME POTENTIAL FOR
A SW FLOW EVENT MONDAY NIGHT.
CONFIDENCE IN THIS FORECAST IS BUILDING WITH EACH MODEL RUN SINCE
THE ARCTIC OUTBREAK HAS BEEN SHOWN BY THE GFS AND ECMWF FOR 5 DAYS
IN A ROW...ON BOTH THE 00Z AND 12Z RUNS.
THE LATEST RUN OF THE ECMWF AND GEM SHOW WHAT I HAVE BEEN TRYING TO
SAY FOR THE PAST 4 SHIFTS... THE SYSTEM WILL BE STRONG THAN
CURRENTLY FORECAST BY ANY OF THE MODELS. I BASE THIS ON THE 180-200
JET CORE THAT CROSSED THE DATELINE FRIDAY AFTERNOON. THE MODELS
CONTINUE TO SHOW THIS SYSTEM CLIMBING THE UPPER RIDGE AND DIVING
SOUTHEAST BY TUESDAY NIGHT INTO WEDNESDAY. THIS MAY ACTUALLY SLOW
DOWN THE PUSH OF COLD AIR BY 12 HOURS IF A DECENT SURFACE WAVES
DEVELOPS WHICH I BELIEVE WILL HAPPEN (AS PER LATEST ECMWF). THIS
WOULD MEAN A SIGNIFICANT WIND/SNOW EVENT FOR OUR CWA WED
NIGHT/THURSDAY. GIVEN THE ECMWF THIS WOULD NOT BE JUST THE LAKE
SHORE...SEEMS THERE WILL BE AN I-94 CONVERGENCE BAND THURSDAY SO
THIS SNOW WILL SPREAD WELL INLAND TOO. I INCREASED THE POP TO AROUND
50 PCT BECAUSE THERE IS LITTLE QUESTION IN MY MIND... IF THE COLD
AIR COMES DOWN IT WILL SNOW!
AS FOR MONDAY NIGHT/EARLY TUESDAY AS THE NEXT SHORTWAVE MOVES ACROSS
THE AREA WINDS WILL TURN SOUTHWEST SOME LIFT IN THE DECENT LIFT IN
THE DGZ AROUND 06Z TUESDAY. THIS COULD BE ONE OF THOSE SURPRISE
SNOW EVENTS... WE WILL HAVE TO WATCH THIS CLOSELY.
&&
.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1250 PM EST SAT DEC 29 2012
THE TWO MAIN ITEMS OF INTEREST WITH THIS SET OF FCSTS IS THE
CURRENT SNOW MOVING OUT THIS AFTERNOON AND THEN LAKE EFFECT TRENDS
FOR TONIGHT AND TOMORROW.
THE AREA OF LIGHT SNOW WAS SOUTHEAST OF A LINE FROM KALAMAZOO TO
GRAND RAPIDS TO ALMA AS OF 1745Z THIS AFTERNOON. THIS SNOW IS
PRODUCING LOW MVFR TO IFR CONDITIONS. THIS IS EXPECTED TO MOVE OUT
TO THE SE OF ALL THE TERMINALS BY AROUND 21Z THIS AFTERNOON. SOME
SCATTERED VFR CONDITIONS ARE POSSIBLE BEHIND THE SNOW FOR A SHORT
TIME. MORE MVFR CIGS AROUND 2500 FT ACROSS CENTRAL LOWER MICHIGAN
WILL MOVE IN LATER THIS AFTERNOON.
LAKE EFFECT SNOW SHOWERS WILL GRADUALLY MOVE IN LATE THIS
AFTERNOON AND MORE SO TONIGHT AS NNE WINDS GRADUALLY SHIFT TO THE
WEST OVERNIGHT TONIGHT. LAKE EFFECT WILL SPREAD ACROSS THE
LAKESHORE FIRST LATE AFTERNOON/EARLY EVENING...THEN INLAND
THEREAFTER. MAINLY MVFR CIGS AND VSBYS ARE EXPECTED WITH SOME SPOTTY
IFR POSSIBLE CLOSER TO THE LAKESHORE. SNOW SHOWERS WILL SLOWLY
DIMINISH THROUGH 18Z SUN THEN BEFORE ENDING AFTER THE TAF PERIOD.
&&
.MARINE...
ISSUED AT 330 AM EST SAT DEC 29 2012
WINDS AND WAVES WILL REACH SCA CRITERIA LATE THIS EVENING SO WE WILL
HOIST A SCA FROM ST. JOSEPH TO MANISTEE FROM THEN THROUGH EARLY
SUNDAY AFTERNOON.
&&
.HYDROLOGY...
ISSUED AT 330 AM EST SAT DEC 29 2012
NO HYDRO CONCERNS DUE TO VERY LITTLE QPF BUT RIVER ICE WILL DEVELOP
THIS WEEK... PARTICULARLY LATE IN THE WEEK.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST SUNDAY
FOR LMZ844>849.
&&
$$
UPDATE...TJT
SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...WDM
AVIATION...NJJ
HYDROLOGY...LAURENS
MARINE...LAURENS
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
1234 PM EST SAT DEC 29 2012
.AVIATION...
//DISCUSSION...
RESIDUAL MIDLEVEL DYNAMICS FROM AN EARLIER FRONTAL ZONE IS NOW
ADVECTING INTO SOUTHERN PORTIONS OF SOUTHEASTERN MICHIGAN FROM THE
NORTHWEST. FOR NOW...FLOW TRAJECTORY AND LATEST TRENDS SUGGESTS
PRECIPITATION WILL NOT IMPACT KFNT AND KMBS. BEHAVIOR OF BASE
REFLECTIVITY PRODUCTS HAS BEEN INTERESTING...SUGGESTING THAT
SEEDER FEEDER PROCESSES ARE IN PLAY TO HELP GENERATE A MODESTLY
BURGEONING AREA OF LIGHT SNOW. LACK OF ANY TANGIBLE DRY AIR
ADVECTION FOLLOWING LAST NIGHTS SYSTEM CERTAINLY SUPPORTS THIS
IDEA. EXPECTATIONS ARE FOR A PERIOD OF MVFR TYPE SNOW ACTIVITY
WITH SOME IFR VISIBILITIES RESULTING DUE TO THE ADDITION OF BR/HZ.
THE LAKE EFFECT SNOW ACTIVITY THAT IS EXPECTED TO CRASH INTO
PORTIONS OF THE THUMB LATER ON...SHOULD BE SUBSEQUENTLY SWEPT
EASTWARD. PERSISTENT NORTHWESTERLY...CYCLONIC FLOW SUPPORTS
STRATOCUMULUS THROUGHOUT THE TAF CYCLE.
FOR DTW...MVFR TO OCCASIONAL IFR VISBY LIGHT SNOW IS EXPECTED OVER
THE NEXT 3 TO 4 HOURS. THE REASON FOR IFR VISBY IS DUE TO THE
PERSISTENCE OF BR/HZ. CEILING HEIGHTS ARE EXPECTED TO REMAIN MVFR
THROUGHOUT THE PERIOD. MODEL DATA IS SUGGESTING IFR CEILING HEIGHTS
LATE TONIGHT/TOMORROW MORNING BUT ATTM...SUSPECT THE MODELS ARE
OVERDONE ON THE AMOUNT OF NEAR SURFACE MOISTURE.
//DTW THRESHOLD THREATS...
* HIGH CONFIDENCE CEILINGS WILL BE BELOW 5000 FT.
&&
.PREV DISCUSSION...ISSUED 1114 AM EST SAT DEC 29 2012
UPDATE...
SYSTEM SNOW FROM LAST NIGHTS EVENT HAS ALL BUT ENDED ACROSS
SOUTHEASTERN MICHIGAN. THERE IS SOME 3-4SM VISBY VARIETY LIGHT
SNOW CURRENTLY TRACKING TOWARDS THE WESTERN CWA FROM WESTERN
MICHIGAN. THIS ACTIVITY APPEARS TO BE DRIVEN BY A 850-700MB
TEMPERATURE GRADIENT STRUCTURE AND ASSOCIATED DEFORMATION THAT
HAD STALLED OUT ACROSS SECTIONS OF MID MICHIGAN OVERNIGHT. THIS
AXIS IS BECOMING FLUSHED/BACKED INTO SOUTHERN SECTIONS OF THE
LOWER PENINSULA AS MIDLEVEL WINDS BACK NORTHWESTERLY IN RESPONSE
TO THE SURFACE LOW PRESSURE CENTER NOW TRACKING INTO WESTERN PA.
FORCING DYNAMICS HAVE BEEN ERODING WITH A DOWNTREND OF
CONVERGENCE. A GENERAL CHANCE POP WILL SUFFICE. ANY ACCUMULATIONS
SHOULD BE LIMITED TO SECTIONS OF WASHTENAW/LENAWEE COUNTIES WHERE
A FEW TENTHS OF ADDITIONAL SNOWFALL IS POSSIBLE LATER THIS
AFTERNOON.
OTHERWISE...MAIN THING TO WATCH GOING FORWARD IS THE LAKE EFFECT
SNOWFALL POTENTIAL FOR THE NORTHERN THUMB AND IMMEDIATE LAKE HURON
SHORELINE. IT HAS BEEN DIFFICULT GAUGING INTENSITY AND LOCATION
OF EXISTING LAKE EFFECT/CLOUD MATERIAL DUE TO SPARSE RADAR NETWORK
AND HIGH CLOUDS OBSCURING ANY LOOK DOWN LOW. THERE WERE A FEW IR
IMAGES EARLIER THAT SUGGESTED PRE-EXISTING ORGANIZED BANDING
STRUCTURES. A SAMPLE OF SHORELINE SURFACE OBSERVATIONS DEPICT
CYCLONIC FLOW OUT OVER NORTH CENTRAL LAKE HURON SIGNALING A
MODERATE LAKE AGGREGATE TROUGH. THE SAME BACKING OF WINDS THAT IS
OCCURRING OVER PORTIONS OF LAKE MICHIGAN/WESTERN LOWER MICHIGAN
WILL EVENTUALLY CATCH UP TO LAKE HURON AND ACT IN ERODING THE LAKE
AGGREGATE TROUGH STRUCTURE. THE OBSERVATIONAL SETUP/REGIME AGREES
WELL WITH LATEST HRRR AND IN HOUSE HI RESOLUTION WRF RUNS THAT
CRASH A LAKE SCALE MESOVORTEX INTO HURON COUNTY DURING THE
AFTERNOON. CLOUD BEARING MEAN WIND SHOULD PUSH DEVELOPED LAKE
EFFECT SOUTHWARD WITH A TRAJECTORY THAT SHOULD HIT THE TIP OF THE
THUMB DIRECTLY. MODELS DISAGREE ON TIMING BY AS MUCH AS 3 HOURS
OR SO...WHICH MAKES TIMING THE ONSET DIFFICULT. DURATION IS EXPECTED
TO BE BRIEF...A FEW HOURS AT THOSE LOCATIONS IMPACTED WHICH WILL
LIMIT SNOWFALL AMOUNTS. LAKE EFFECT PARAMETERS ARE SO SO...4C
LAKE SFC TEMPERATURES YIELDING SFC-850 DELTA T OF -15C AND EQL
HEIGHTS REACHING 8 KFT AGL. DID INCREASE THE CONDITIONAL SNOWFALL
ACCUMULATIONS IN THE THUMB AS CONFIDENCE HAS INCREMENTALLY
INCREASED. LOCALLY...ACCUMULATIONS OF UP TO 3 INCHES WILL BE
POSSIBLE.
PREV DISCUSSION...ISSUED 405 AM EST SAT DEC 29 2012
SHORT TERM...TODAY THROUGH TONIGHT
EXTREMELY LOW H7-H4 STATIC STABILITY HAS ALLOWED FOR AN IMPRESSIVE
RESPONSE TO AN UNIMPRESSIVE FORCING FIELD OVER SOUTHEAST MICHIGAN
THIS MORNING. HEIGHT FALLS LEADING AN APPROACHING SHORTWAVE TROUGH
HAVE ALLOWED FOR NORTHWARD DEVELOPMENT OF WEAK DEFORMATION AND
300-305K ISENTROPIC ASCENT WHICH HAS RESULTED IN WIDESPREAD LIGHT
SNOW ALONG/SOUTH OF I-69. THE INHERITED FORECAST STILL LOOKS ON
TRACK GIVEN THE LATEST TRENDS IN OBSERVATIONS AND THE 00Z SUITE OF
GUIDANCE WHICH OFFERED LITTLE REASON TO DEVIATE FROM THE OFFICIAL
FORECAST REASONING. GIVEN AN EXPECTED DURATION OF ANYWHERE FROM 5
HOURS (NORTH) TO 9 HOURS (SOUTH) AND THERMODYNAMIC PROFILES
SUPPORTIVE OF SNOW RATIOS IN THE 10 TO 15:1 RANGE, A SOLID
2-3"/ISOLATED 4" IS STILL A REASONABLE EXPECTATION FOR FAR SOUTHEAST
AREAS, ESPECIALLY MONROE COUNTY...WITH A SOLID 1-2"/ISOLATED 3"
STILL FORECAST ALONG AND SOUTH OF A PORT HURON TO HOWELL LINE.
CONFIDENCE IS INCREASED COMPARED TO PREVIOUS FORECASTS AS IT APPEARS
THAT THE FORCING FIELD WILL SEE A BOOST BETWEEN 10-13Z AS THE TROUGH
AXIS OVER THE WESTERN GREAT LAKES ROTATES INTO THE AREA. LIGHT SNOW
MAY ULTIMATELY BE SLOW TO BREAK UP/TAPER OFF UNTIL PASSAGE OF THE
TROUGH TO THE EAST AFTER 18Z.
ATTENTION THEN TURNS TO LAKE EFFECT POTENTIAL FOR THE
CENTRAL/EASTERN THUMB DURING THE AFTERNOON AND EVENING HOURS.
VEERING BOUNDARY LAYER WIND BEHIND THE DEPARTING LOW WILL FORCE A
LAKE-INDUCED TROUGH TO ROTATE CYCLONICALLY ACROSS THE THUMB AS BL
FLOW SIMULTANEOUSLY BECOMES FOCUSED ONSHORE. IN AN ATTEMPT TO FINE
TUNE THE MESOSCALE ASPECTS OF THE FORECAST, MADE AN AGGRESSIVE
UPWARD BOOST TO POPS FOR BAD AXE AND POINTS EAST IN HURON/SANILAC
COUNTIES, BUT STILL STAYED ON THE CONSERVATIVE SIDE WITH REGARD TO
COVERAGE AND ACCUMULATION POTENTIAL...ALTHOUGH BOTH OF THESE WERE
STILL GIVEN AN UPWARD NUDGE, JUST TO A LESSER DEGREE. THE ROTATING
WIND FIELD IS EXPECTED TO LEAVE NO MORE THAN A 6 HOUR WINDOW THAT
WILL BE FAVORABLE FOR LES CONDITIONS IN THE THUMB, WHICH WILL BE THE
MAIN FACTOR IN LIMITING ACCUMULATING SNOW POTENTIAL IN THIS HIGH
PROBABILITY/SHORT DURATION LES SCENARIO.
LIGHT SNOW SHOWERS WILL THEN POTENTIALLY EXPAND FROM NORTH TO SOUTH
THROUGH THE AFTERNOON AS THE LAKE TROUGH AXIS ROTATES THROUGH THE
CWA DURING PEAK HEATING, GRADUALLY WEAKENING AS IT DOES SO.
ADDITIONAL MINOR ACCUMULATIONS WILL THEREFORE BE POSSIBLE IN THE
21Z-03Z TIME FRAME FOR A WIDE PORTION OF THE AREA, BUT ELECTED TO
LEAVE THE CURRENT FORECAST FOR A FEW ADDITIONAL TENTHS UNCHANGED
UNTIL LAKE-INDUCED EFFECTS BECOME BETTER DEFINED IN THE OBSERVATIONS
LATE THIS MORNING/EARLY THIS AFTERNOON.
DECREASING, BUT STILL PLENTIFUL, LOW CLOUDS AND A FRESH COUPLE
INCHES OF SNOW PACK WILL FAVOR OVERNIGHT LOWS IN THE UPPER TEENS,
JUST A TOUCH COOLER THAN THIS MORNING. A MORE SIGNIFICANT DOWNWARD
ADJUSTMENT WILL BE NEEDED SHOULD CLEARING OCCUR EARLIER THAN
EXPECTED.
LONG TERM...SUNDAY THROUGH FRIDAY
A RIDGE OF HIGH PRESSURE WILL BRING QUIET WEATHER DURING THE SECOND
HALF OF THE WEEKEND AS COOLER THAN NORMAL TEMPERATURES CONTINUE
ACROSS THE CENTRAL GREAT LAKES REGION. ATTENTION CONTINUES TO BE ON
TWO SYSTEMS TRACKING CLOSE TO SOUTHEAST MICHIGAN MONDAY AND MONDAY
NIGHT. THE MODELS CONTINUE TO KEEP THESE SYSTEMS FROM PHASING
TOGETHER OVER THE CENTRAL GREAT LAKES AS THE NORTHERN SYSTEM TRACKS
THROUGH SOUTHERN CANADA...FAR ENOUGH NORTH TO NOT PHASE WITH THE
SOUTHERN SYSTEM ACROSS THE OHIO VALLEY. HOWEVER THE NAM HAS COME IN
THIS RUN WITH THE SOUTHERN SYSTEM TRACKING MUCH FURTHER NORTH THAN
ANY OTHER MODEL INCLUDING THE CANADIAN/ECMWF/GFS. THIS FAR NORTH
SOLUTION WOULD BRING A SOLID INCH OF SNOW ACROSS MUCH OF SOUTHEAST
MICHIGAN AS THE NAM BRINGS THE SURFACE LOW THROUGH THE SOUTHERN
GREAT LAKES DURING THIS PERIOD. THE CANADIAN/ECMWF/GFS MODELS KEEP
THE LOW WELL TO THE SOUTH...TRACKING THROUGH THE TENNESSEE VALLEY
WITH A RIDGE ACROSS THE UPPER PLAINS ASSISTING IN KEEPING THE LOW ON
A SOUTHERN TRACK. SINCE THE NAM IS A SIGNIFICANT OUTLIER AND GIVEN
THE LARGE RIDGE ACROSS THE PLAINS WILL STICK WITH THE SOUTHERN
SOLUTION AND MAINTAIN A MOSTLY DRY FORECAST FOR MUCH OF THE CWA. THE
MAIN EXCEPTION WILL BE ACROSS THE FAR SOUTH WHICH MAY GET A GLANCING
BLOW OF SNOW SHOWERS AS A SHORTWAVE TRACKS THROUGH THE SOUTHERN
GREAT LAKES MONDAY NIGHT.
THE MAIN STORY DURING THE MIDDLE TO LATE PART OF THE WEEK WILL BE AN
ARCTIC AIRMASS THAT WILL MAKE ITS PRESENCE FELT ACROSS THE GREAT
LAKES REGION...BRINGING THE COLDEST AIR OF THE SEASON TO SOUTHEAST
MICHIGAN. THIS COLD AIRMASS WILL LIMIT HIGH TEMPERATURES TO AROUND
20 DEGREES THURSDAY AND FRIDAY...WITH SEVERAL LOCATIONS LIKELY NOT
EVEN REACHING THIS MARK. THE COLDEST PART OF THIS AIRMASS WILL BE
FELT DURING THE OVERNIGHT HOURS AS LOW TEMPERATURES GET DOWN INTO
THE SINGLE DIGITS BELOW ZERO THURSDAY NIGHT AS 850 MB TEMPERATURES
PLUMMET WELL INTO THE TEENS BELOW ZERO WITH SOME BREAKS IN THE
CLOUDS PROVIDING JUST ENOUGH RADIATIONAL COOLING TO PLUMMET
TEMPERATURES QUICKLY. DESPITE MODEL GUIDANCE COMING IN SEVERAL
DEGREES WARMER...THE MODELS GENERALLY HAVE A TOUGH TIME RESOLVING
ARCTIC OUTBREAKS. THEREFORE CONFIDENCE IS HIGHER THAN NORMAL IN
GOING SEVERAL DEGREES BELOW GUIDANCE NUMBERS THIS FAR OUT.
THE SECOND PART OF THE STORY DURING THE MID TO LATE PART OF THE WEEK
WITH BE ADDITIONAL SNOWFALL CHANCES AS A NORTHERLY FETCH OFF LAKE
HURON PRODUCES SEVERAL OPPORTUNITIES FOR LAKE EFFECT SNOW SHOWERS
ACROSS THE THUMB REGION. THE COLD AIRMASS WILL OFFER DELTA T VALUES
IN EXCESS OF 20...WITH THE MAIN LIMITING FACTOR BEING THE EXACT WIND
DIRECTION WHICH WILL DETERMINE WHO GETS THE MAJORITY OF THE LAKE
EFFECT SNOW. THIS FAR OUT WILL BLANKET THE THUMB WITH CHANCY SNOW
POPS UNTIL WIND DIRECTIONS CAN BE BETTER RESOLVED IN SUBSEQUENT RUNS.
MARINE...
A MODEST INCREASE TO THE SURFACE PRESSURE GRADIENT COMBINED WITH
WINDS ROTATING TO A MORE ONSHORE DIRECTION WILL RESULT IN THE
DEVELOPMENT OF A MODERATE BREEZE ACROSS CENTRAL AND SOUTHERN LAKE
HURON TODAY WHICH IS FORECAST TO DRIVE SIGNIFICANT WAVE HEIGHTS INTO
THE 3 TO 5 FOOT RANGE BEGINNING EARLY THIS AFTERNOON. FOR THIS
REASON...SMALL CRAFT ADVISORIES ARE NOW IN EFFECT FROM OUTER SAGINAW
BAY TO PORT SANILAC FOR THIS AFTERNOON THROUGH TONIGHT. DEPENDING ON
THE EXACT EVOLUTION OF THE WIND FIELD...THE ADVISORIES MAY NEED TO
BE ADJUSTED FURTHER SOUTHWARD TOWARD PORT HURON FOR THIS EVENING.
A MODERATE SOUTHWEST FLOW WILL DEVELOP SUNDAY NIGHT INTO MONDAY AS
THE SURFACE PRESSURE GRADIENT TIGHTENS OVER AREA WATERS AS LOW
PRESSURE CROSSES NORTH OF THE REGION. GUSTY NORTHWEST WINDS WILL
DEVELOP BY MIDWEEK NEXT WEEK AS COLDER AIR SPREADS INTO THE GREAT
LAKES REGION IN THE WAKE OF THIS SYSTEM.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
SANILAC...UNTIL 7 AM SUNDAY.
SMALL CRAFT ADVISORY...OUTER SAGINAW BAY...UNTIL 1 AM SUNDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....CB
UPDATE.......CB
SHORT TERM...JVC
LONG TERM....KURIMSKI
MARINE.......JVC
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
1126 AM EST SAT DEC 29 2012
.SYNOPSIS...
ISSUED AT 330 AM EST SAT DEC 29 2012
A FEW LIGHT SNOW SHOWERS AND FLURRIES WILL LINGER THIS MORNING WITH
LIGHT LAKE EFFECT SNOW SHOWERS EXPECTED TONIGHT INTO SUNDAY MORNING.
TEMPERATURES WILL AVERAGE BELOW NORMAL THROUGH THE COMING WEEK WITH
SEVERAL CHANCES FOR SNOW SHOWERS AND A SHOT OF MUCH COLDER AIR
EXPECTED FOR LATE WEEK.
&&
.UPDATE...
ISSUED AT 1125 AM EST SAT DEC 29 2012
UPDATED FORECASTS TO LOWER POPS NORTH OF I-96. HAVE ALSO DECREASED
POPS INTO THIS EVENING ALONG THE INTERIOR I-94 CORRIDOR. WE ARE
LOOKING FOR A QUICK BURST OF LAKE ENHANCED SNOW MAINLY BEFORE
MIDNIGHT MAINLY SOUTH OF HOLLAND THAT COULD ADD AN INCH OR SO NEAR
THE LAKESHORE.
RADAR LOOP INDICATES PRESENCE OF A SURFACE MESOLOW OVER
SOUTHEASTERN LAKE MICHIGAN THAT IS WEAKENING AND MOVING SOUTHEAST
TOWARDS SOUTH HAVEN. MESOSCALE SUBSIDENCE BEHIND THIS FEATURE IS
RESULTING IN A SHARP TRAILING EDGE TO THE SNOW THAT IS APPROACHING
I-96 FROM THE NORTH. TO THE WEST...A WEAK N-S UPPER POT VORT LOBE
NOTED ON WATER VAPOR IMAGERY IS CROSSING IA/MN AT THIS TIME AND
SHOULD IMPACT THE CWFA THIS EVENING AT ITS CURRENT RATE OF SPEED.
LATEST RAP SNOW TOOL GUIDANCE FOR SOUTH HAVEN (LWA) SUGGESTS THAT 1
TO 2 INCHES OF SNOW COULD FALL IN THE 9 PM - 1 AM TIME FRAME
THERE.
UPDATE
ISSUED AT 704 AM EST SAT DEC 29 2012
I HAVE UPDATED THE FORECAST TO ALLOW THE SNOW BAND JUST NOW MOVING
INTO THE I-96 AREA TO CONTINUE TO MOVE SOUTH OVER TIME. THIS IS
REALLY A WEAK COLD FRONT THAT IS MOVING SOUTH WITH TIME BEHIND THE
DEPARTING STORM. THE NAM SHOWS SOME WEAK LIFT IN THE DGZ AS THIS
FEATURE MOVES SOUTH WITH TIME. IT DOES TAKE IT`S TIME THROUGH BY
21Z THERE IS STILL LIFT OVER OUR SE CWA WITH THIS FEATURE. ONCE
THE FEATURE MOVES SOUTH THE SNOW WILL END FROM NORTH TO SOUTH BUT
IT MAY TAKE UNTIL NOON OR SO FOR IT TO END BY INTERSTATE 96 AND
LATER BY INTERSTATE 94. ACCUMULATIONS WILL LIMITED AS LIFT IS
FEEBLE AND CURRENT VISIBILITIES ARE IN THE 3 TO 6 MILE RANGE.
&&
.SHORT TERM...(TODAY THROUGH MONDAY AFTERNOON)
ISSUED AT 330 AM EST SAT DEC 29 2012
A FEW LIGHT SNOW SHOWERS AND FLURRIES WILL LINGER THIS MORNING.
STEADIER SYNOPTIC LIGHT SNOW WILL CLIP OUR EXTREME SE FCST AREA OVER
TOWARD JXN THIS MORNING AND EARLY AFTERNOON. LIGHT SNOW BEGAN IN JXN
ABOUT AN HOUR AGO AND VERY LIGHT ACCUMULATIONS OF UNDER AN INCH ARE
ANTICIPATED THERE.
AN UPPER LEVEL DISTURBANCE WILL BRING LAKE ENHANCED LIGHT SNOW
SHOWERS AND FLURRIES TONIGHT INTO SUNDAY MORNING BUT WITH LITTLE IF
ANY ACCUMULATIONS. A HIGH PRESSURE RIDGE WILL BRING FAIR WX SUNDAY
AFTERNOON THROUGH SUNDAY NIGHT BEFORE AN APPROACHING COLD FRONT
BRINGS A CHC OF LIGHT SNOW SHOWERS MONDAY.
.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 330 AM EST SAT DEC 29 2012
THE MAIN FOCUS OF THE LONG TERM PORTION OF THE FCST WILL BE ON THE
ARCTIC AIR MASS THAT IS EXPECTED TO COME DOWN LATER NEXT WEEK AND
THE LAKE EFFECT POTENTIAL WITH IT. THERE IS ALSO SOME POTENTIAL FOR
A SW FLOW EVENT MONDAY NIGHT.
CONFIDENCE IN THIS FORECAST IS BUILDING WITH EACH MODEL RUN SINCE
THE ARCTIC OUTBREAK HAS BEEN SHOWN BY THE GFS AND ECMWF FOR 5 DAYS
IN A ROW...ON BOTH THE 00Z AND 12Z RUNS.
THE LATEST RUN OF THE ECMWF AND GEM SHOW WHAT I HAVE BEEN TRYING TO
SAY FOR THE PAST 4 SHIFTS... THE SYSTEM WILL BE STRONG THAN
CURRENTLY FORECAST BY ANY OF THE MODELS. I BASE THIS ON THE 180-200
JET CORE THAT CROSSED THE DATELINE FRIDAY AFTERNOON. THE MODELS
CONTINUE TO SHOW THIS SYSTEM CLIMBING THE UPPER RIDGE AND DIVING
SOUTHEAST BY TUESDAY NIGHT INTO WEDNESDAY. THIS MAY ACTUALLY SLOW
DOWN THE PUSH OF COLD AIR BY 12 HOURS IF A DECENT SURFACE WAVES
DEVELOPS WHICH I BELIEVE WILL HAPPEN (AS PER LATEST ECMWF). THIS
WOULD MEAN A SIGNIFICANT WIND/SNOW EVENT FOR OUR CWA WED
NIGHT/THURSDAY. GIVEN THE ECMWF THIS WOULD NOT BE JUST THE LAKE
SHORE...SEEMS THERE WILL BE AN I-94 CONVERGENCE BAND THURSDAY SO
THIS SNOW WILL SPREAD WELL INLAND TOO. I INCREASED THE POP TO AROUND
50 PCT BECAUSE THERE IS LITTLE QUESTION IN MY MIND... IF THE COLD
AIR COMES DOWN IT WILL SNOW!
AS FOR MONDAY NIGHT/EARLY TUESDAY AS THE NEXT SHORTWAVE MOVES ACROSS
THE AREA WINDS WILL TURN SOUTHWEST SOME LIFT IN THE DECENT LIFT IN
THE DGZ AROUND 06Z TUESDAY. THIS COULD BE ONE OF THOSE SURPRISE
SNOW EVENTS... WE WILL HAVE TO WATCH THIS CLOSELY.
&&
.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 704 AM EST SAT DEC 29 2012
AS THE SNOW BAND MOVES OUT OF THE JXN AREA ANOTHER SNOW BAND
ASSOCIATED WITH A WEAK COLD FRONT WILL MOVE ACROSS ALL OF THE TAF
SITES TODAY. OVERALL I EXPECT MVFR CIGS/VSBY AS THIS MOVES THROUGH
SOME BRIEF IFR VSBY ARE POSSIBLE IN THE BETTER SNOW SHOWERS.
TONIGHT WINDS SHIFT FROM NORTH TO WEST AND THAT WILL BRING LAKE
EFFECT INLAND TO MKG..,GRR...BTL AND AZO OVERNIGHT. MORE MVFR
CIGS/VSBY AS THIS TOO WILL BE LIGHT SNOW AS LIFT IS WEAK.
&&
.MARINE...
ISSUED AT 330 AM EST SAT DEC 29 2012
WINDS AND WAVES WILL REACH SCA CRITERIA LATE THIS EVENING SO WE WILL
HOIST A SCA FROM ST. JOSEPH TO MANISTEE FROM THEN THROUGH EARLY
SUNDAY AFTERNOON.
&&
.HYDROLOGY...
ISSUED AT 330 AM EST SAT DEC 29 2012
NO HYDRO CONCERNS DUE TO VERY LITTLE QPF BUT RIVER ICE WILL DEVELOP
THIS WEEK... PARTICULARLY LATE IN THE WEEK.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST SUNDAY
FOR LMZ844>849.
&&
$$
UPDATE...TJT
SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...WDM
AVIATION...WDM
HYDROLOGY...LAURENS
MARINE...LAURENS
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
1114 AM EST SAT DEC 29 2012
.UPDATE...
SYSTEM SNOW FROM LAST NIGHTS EVENT HAS ALL BUT ENDED ACROSS
SOUTHEASTERN MICHIGAN. THERE IS SOME 3-4SM VISBY VARIETY LIGHT
SNOW CURRENTLY TRACKING TOWARDS THE WESTERN CWA FROM WESTERN
MICHIGAN. THIS ACTIVITY APPEARS TO BE DRIVEN BY A 850-700MB
TEMPERATURE GRADIENT STRUCTURE AND ASSOCIATED DEFORMATION THAT
HAD STALLED OUT ACROSS SECTIONS OF MID MICHIGAN OVERNIGHT. THIS
AXIS IS BECOMING FLUSHED/BACKED INTO SOUTHERN SECTIONS OF THE
LOWER PENINSULA AS MIDLEVEL WINDS BACK NORTHWESTERLY IN RESPONSE
TO THE SURFACE LOW PRESSURE CENTER NOW TRACKING INTO WESTERN PA.
FORCING DYNAMICS HAVE BEEN ERODING WITH A DOWNTREND OF
CONVERGENCE. A GENERAL CHANCE POP WILL SUFFICE. ANY ACCUMULATIONS
SHOULD BE LIMITED TO SECTIONS OF WASHTENAW/LENAWEE COUNTIES WHERE
A FEW TENTHS OF ADDITIONAL SNOWFALL IS POSSIBLE LATER THIS
AFTERNOON.
OTHERWISE...MAIN THING TO WATCH GOING FORWARD IS THE LAKE EFFECT
SNOWFALL POTENTIAL FOR THE NORTHERN THUMB AND IMMEDIATE LAKE HURON
SHORELINE. IT HAS BEEN DIFFICULT GAUGING INTENSITY AND LOCATION
OF EXISTING LAKE EFFECT/CLOUD MATERIAL DUE TO SPARSE RADAR NETWORK
AND HIGH CLOUDS OBSCURING ANY LOOK DOWN LOW. THERE WERE A FEW IR
IMAGES EARLIER THAT SUGGESTED PRE-EXISTING ORGANIZED BANDING
STRUCTURES. A SAMPLE OF SHORELINE SURFACE OBSERVATIONS DEPICT
CYCLONIC FLOW OUT OVER NORTH CENTRAL LAKE HURON SIGNALING A
MODERATE LAKE AGGREGATE TROUGH. THE SAME BACKING OF WINDS THAT IS
OCCURRING OVER PORTIONS OF LAKE MICHIGAN/WESTERN LOWER MICHIGAN
WILL EVENTUALLY CATCH UP TO LAKE HURON AND ACT IN ERODING THE LAKE
AGGREGATE TROUGH STRUCTURE. THE OBSERVATIONAL SETUP/REGIME AGREES
WELL WITH LATEST HRRR AND IN HOUSE HI RESOLUTION WRF RUNS THAT
CRASH A LAKE SCALE MESOVORTEX INTO HURON COUNTY DURING THE
AFTERNOON. CLOUD BEARING MEAN WIND SHOULD PUSH DEVELOPED LAKE
EFFECT SOUTHWARD WITH A TRAJECTORY THAT SHOULD HIT THE TIP OF THE
THUMB DIRECTLY. MODELS DISAGREE ON TIMING BY AS MUCH AS 3 HOURS
OR SO...WHICH MAKES TIMING THE ONSET DIFFICULT. DURATION IS EXPECTED
TO BE BRIEF...A FEW HOURS AT THOSE LOCATIONS IMPACTED WHICH WILL
LIMIT SNOWFALL AMOUNTS. LAKE EFFECT PARAMETERS ARE SO SO...4C
LAKE SFC TEMPERATURES YIELDING SFC-850 DELTA T OF -15C AND EQL
HEIGHTS REACHING 8 KFT AGL. DID INCREASE THE CONDITIONAL SNOWFALL
ACCUMULATIONS IN THE THUMB AS CONFIDENCE HAS INCREMENTALLY
INCREASED. LOCALLY...ACCUMULATIONS OF UP TO 3 INCHES WILL BE
POSSIBLE.
&&
.AVIATION...ISSUED 604 AM EST SAT DEC 29 2012
//DISCUSSION...
LIGHT TO OCCASIONALLY MODERATE SNOW HAS EXPANDED INTO SOUTHEAST
MICHIGAN THIS MORNING, BRINGING MVFR TO IFR CONDITIONS TO KFNT AND
POINTS SOUTH. SNOW WILL BE RELATIVELY SHORT-LIVED FOR NORTHERN
LOCATIONS SUCH AS FNT, WHERE AN ADDITIONAL COUPLE HOURS OR SO OF
LIGHT SNOW MAY RESULT IN SOME MINOR ACCUMULATIONS. THE AIRFIELDS OF
THE METRO DETROIT AREA, HOWEVER, WILL SEE A MORE PERSISTENT SNOW
GRADUALLY TAPER OFF IN COVERAGE BETWEEN NOW AND LATE MORNING WHEN
ANYWHERE FROM 1 TO 3 INCHES TOTAL CONTINUES TO LOOK PROBABLE.
ADDITIONAL LIGHT SNOW SHOWERS MAY TRACK FROM NORTH TO SOUTH ACROSS
THE AREA THIS AFTERNOON BRINGING LITTLE TO NO ADDITIONAL
ACCUMULATION.
FOR DTW...SNOW WILL PERSIST WITH REDUCED VSBYS THROUGH AT LEAST 14Z,
BEFORE GRADUALLY TAPERING OFF TO LOW OVERCAST CIGS AND FLURRIES BY
17Z. 2 TO 3 INCHES OF TOTAL ACCUMULATION IS STILL EXPECTED FOR KDTW.
//DTW THRESHOLD THREATS...
* HIGH CONFIDENCE CEILINGS WILL BE BELOW 5000 FT.
* LOW CONFIDENCE VISIBILITIES WILL DROP BELOW A HALF MILE IN SNOW
THIS MORNING.
&&
.PREV DISCUSSION...ISSUED 405 AM EST SAT DEC 29 2012
SHORT TERM...TODAY THROUGH TONIGHT
EXTREMELY LOW H7-H4 STATIC STABILITY HAS ALLOWED FOR AN IMPRESSIVE
RESPONSE TO AN UNIMPRESSIVE FORCING FIELD OVER SOUTHEAST MICHIGAN
THIS MORNING. HEIGHT FALLS LEADING AN APPROACHING SHORTWAVE TROUGH
HAVE ALLOWED FOR NORTHWARD DEVELOPMENT OF WEAK DEFORMATION AND
300-305K ISENTROPIC ASCENT WHICH HAS RESULTED IN WIDESPREAD LIGHT
SNOW ALONG/SOUTH OF I-69. THE INHERITED FORECAST STILL LOOKS ON
TRACK GIVEN THE LATEST TRENDS IN OBSERVATIONS AND THE 00Z SUITE OF
GUIDANCE WHICH OFFERED LITTLE REASON TO DEVIATE FROM THE OFFICIAL
FORECAST REASONING. GIVEN AN EXPECTED DURATION OF ANYWHERE FROM 5
HOURS (NORTH) TO 9 HOURS (SOUTH) AND THERMODYNAMIC PROFILES
SUPPORTIVE OF SNOW RATIOS IN THE 10 TO 15:1 RANGE, A SOLID
2-3"/ISOLATED 4" IS STILL A REASONABLE EXPECTATION FOR FAR SOUTHEAST
AREAS, ESPECIALLY MONROE COUNTY...WITH A SOLID 1-2"/ISOLATED 3"
STILL FORECAST ALONG AND SOUTH OF A PORT HURON TO HOWELL LINE.
CONFIDENCE IS INCREASED COMPARED TO PREVIOUS FORECASTS AS IT APPEARS
THAT THE FORCING FIELD WILL SEE A BOOST BETWEEN 10-13Z AS THE TROUGH
AXIS OVER THE WESTERN GREAT LAKES ROTATES INTO THE AREA. LIGHT SNOW
MAY ULTIMATELY BE SLOW TO BREAK UP/TAPER OFF UNTIL PASSAGE OF THE
TROUGH TO THE EAST AFTER 18Z.
ATTENTION THEN TURNS TO LAKE EFFECT POTENTIAL FOR THE
CENTRAL/EASTERN THUMB DURING THE AFTERNOON AND EVENING HOURS.
VEERING BOUNDARY LAYER WIND BEHIND THE DEPARTING LOW WILL FORCE A
LAKE-INDUCED TROUGH TO ROTATE CYCLONICALLY ACROSS THE THUMB AS BL
FLOW SIMULTANEOUSLY BECOMES FOCUSED ONSHORE. IN AN ATTEMPT TO FINE
TUNE THE MESOSCALE ASPECTS OF THE FORECAST, MADE AN AGGRESSIVE
UPWARD BOOST TO POPS FOR BAD AXE AND POINTS EAST IN HURON/SANILAC
COUNTIES, BUT STILL STAYED ON THE CONSERVATIVE SIDE WITH REGARD TO
COVERAGE AND ACCUMULATION POTENTIAL...ALTHOUGH BOTH OF THESE WERE
STILL GIVEN AN UPWARD NUDGE, JUST TO A LESSER DEGREE. THE ROTATING
WIND FIELD IS EXPECTED TO LEAVE NO MORE THAN A 6 HOUR WINDOW THAT
WILL BE FAVORABLE FOR LES CONDITIONS IN THE THUMB, WHICH WILL BE THE
MAIN FACTOR IN LIMITING ACCUMULATING SNOW POTENTIAL IN THIS HIGH
PROBABILITY/SHORT DURATION LES SCENARIO.
LIGHT SNOW SHOWERS WILL THEN POTENTIALLY EXPAND FROM NORTH TO SOUTH
THROUGH THE AFTERNOON AS THE LAKE TROUGH AXIS ROTATES THROUGH THE
CWA DURING PEAK HEATING, GRADUALLY WEAKENING AS IT DOES SO.
ADDITIONAL MINOR ACCUMULATIONS WILL THEREFORE BE POSSIBLE IN THE
21Z-03Z TIME FRAME FOR A WIDE PORTION OF THE AREA, BUT ELECTED TO
LEAVE THE CURRENT FORECAST FOR A FEW ADDITIONAL TENTHS UNCHANGED
UNTIL LAKE-INDUCED EFFECTS BECOME BETTER DEFINED IN THE OBSERVATIONS
LATE THIS MORNING/EARLY THIS AFTERNOON.
DECREASING, BUT STILL PLENTIFUL, LOW CLOUDS AND A FRESH COUPLE
INCHES OF SNOW PACK WILL FAVOR OVERNIGHT LOWS IN THE UPPER TEENS,
JUST A TOUCH COOLER THAN THIS MORNING. A MORE SIGNIFICANT DOWNWARD
ADJUSTMENT WILL BE NEEDED SHOULD CLEARING OCCUR EARLIER THAN
EXPECTED.
LONG TERM...SUNDAY THROUGH FRIDAY
A RIDGE OF HIGH PRESSURE WILL BRING QUIET WEATHER DURING THE SECOND
HALF OF THE WEEKEND AS COOLER THAN NORMAL TEMPERATURES CONTINUE
ACROSS THE CENTRAL GREAT LAKES REGION. ATTENTION CONTINUES TO BE ON
TWO SYSTEMS TRACKING CLOSE TO SOUTHEAST MICHIGAN MONDAY AND MONDAY
NIGHT. THE MODELS CONTINUE TO KEEP THESE SYSTEMS FROM PHASING
TOGETHER OVER THE CENTRAL GREAT LAKES AS THE NORTHERN SYSTEM TRACKS
THROUGH SOUTHERN CANADA...FAR ENOUGH NORTH TO NOT PHASE WITH THE
SOUTHERN SYSTEM ACROSS THE OHIO VALLEY. HOWEVER THE NAM HAS COME IN
THIS RUN WITH THE SOUTHERN SYSTEM TRACKING MUCH FURTHER NORTH THAN
ANY OTHER MODEL INCLUDING THE CANADIAN/ECMWF/GFS. THIS FAR NORTH
SOLUTION WOULD BRING A SOLID INCH OF SNOW ACROSS MUCH OF SOUTHEAST
MICHIGAN AS THE NAM BRINGS THE SURFACE LOW THROUGH THE SOUTHERN
GREAT LAKES DURING THIS PERIOD. THE CANADIAN/ECMWF/GFS MODELS KEEP
THE LOW WELL TO THE SOUTH...TRACKING THROUGH THE TENNESSEE VALLEY
WITH A RIDGE ACROSS THE UPPER PLAINS ASSISTING IN KEEPING THE LOW ON
A SOUTHERN TRACK. SINCE THE NAM IS A SIGNIFICANT OUTLIER AND GIVEN
THE LARGE RIDGE ACROSS THE PLAINS WILL STICK WITH THE SOUTHERN
SOLUTION AND MAINTAIN A MOSTLY DRY FORECAST FOR MUCH OF THE CWA. THE
MAIN EXCEPTION WILL BE ACROSS THE FAR SOUTH WHICH MAY GET A GLANCING
BLOW OF SNOW SHOWERS AS A SHORTWAVE TRACKS THROUGH THE SOUTHERN
GREAT LAKES MONDAY NIGHT.
THE MAIN STORY DURING THE MIDDLE TO LATE PART OF THE WEEK WILL BE AN
ARCTIC AIRMASS THAT WILL MAKE ITS PRESENCE FELT ACROSS THE GREAT
LAKES REGION...BRINGING THE COLDEST AIR OF THE SEASON TO SOUTHEAST
MICHIGAN. THIS COLD AIRMASS WILL LIMIT HIGH TEMPERATURES TO AROUND
20 DEGREES THURSDAY AND FRIDAY...WITH SEVERAL LOCATIONS LIKELY NOT
EVEN REACHING THIS MARK. THE COLDEST PART OF THIS AIRMASS WILL BE
FELT DURING THE OVERNIGHT HOURS AS LOW TEMPERATURES GET DOWN INTO
THE SINGLE DIGITS BELOW ZERO THURSDAY NIGHT AS 850 MB TEMPERATURES
PLUMMET WELL INTO THE TEENS BELOW ZERO WITH SOME BREAKS IN THE
CLOUDS PROVIDING JUST ENOUGH RADIATIONAL COOLING TO PLUMMET
TEMPERATURES QUICKLY. DESPITE MODEL GUIDANCE COMING IN SEVERAL
DEGREES WARMER...THE MODELS GENERALLY HAVE A TOUGH TIME RESOLVING
ARCTIC OUTBREAKS. THEREFORE CONFIDENCE IS HIGHER THAN NORMAL IN
GOING SEVERAL DEGREES BELOW GUIDANCE NUMBERS THIS FAR OUT.
THE SECOND PART OF THE STORY DURING THE MID TO LATE PART OF THE WEEK
WITH BE ADDITIONAL SNOWFALL CHANCES AS A NORTHERLY FETCH OFF LAKE
HURON PRODUCES SEVERAL OPPORTUNITIES FOR LAKE EFFECT SNOW SHOWERS
ACROSS THE THUMB REGION. THE COLD AIRMASS WILL OFFER DELTA T VALUES
IN EXCESS OF 20...WITH THE MAIN LIMITING FACTOR BEING THE EXACT WIND
DIRECTION WHICH WILL DETERMINE WHO GETS THE MAJORITY OF THE LAKE
EFFECT SNOW. THIS FAR OUT WILL BLANKET THE THUMB WITH CHANCY SNOW
POPS UNTIL WIND DIRECTIONS CAN BE BETTER RESOLVED IN SUBSEQUENT RUNS.
MARINE...
A MODEST INCREASE TO THE SURFACE PRESSURE GRADIENT COMBINED WITH
WINDS ROTATING TO A MORE ONSHORE DIRECTION WILL RESULT IN THE
DEVELOPMENT OF A MODERATE BREEZE ACROSS CENTRAL AND SOUTHERN LAKE
HURON TODAY WHICH IS FORECAST TO DRIVE SIGNIFICANT WAVE HEIGHTS INTO
THE 3 TO 5 FOOT RANGE BEGINNING EARLY THIS AFTERNOON. FOR THIS
REASON...SMALL CRAFT ADVISORIES ARE NOW IN EFFECT FROM OUTER SAGINAW
BAY TO PORT SANILAC FOR THIS AFTERNOON THROUGH TONIGHT. DEPENDING ON
THE EXACT EVOLUTION OF THE WIND FIELD...THE ADVISORIES MAY NEED TO
BE ADJUSTED FURTHER SOUTHWARD TOWARD PORT HURON FOR THIS EVENING.
A MODERATE SOUTHWEST FLOW WILL DEVELOP SUNDAY NIGHT INTO MONDAY AS
THE SURFACE PRESSURE GRADIENT TIGHTENS OVER AREA WATERS AS LOW
PRESSURE CROSSES NORTH OF THE REGION. GUSTY NORTHWEST WINDS WILL
DEVELOP BY MIDWEEK NEXT WEEK AS COLDER AIR SPREADS INTO THE GREAT
LAKES REGION IN THE WAKE OF THIS SYSTEM.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
SANILAC...UNTIL 7 AM SUNDAY.
SMALL CRAFT ADVISORY...OUTER SAGINAW BAY...UNTIL 1 AM SUNDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
UPDATE.......CB
AVIATION.....JVC
SHORT TERM...JVC
LONG TERM....KURIMSKI
MARINE.......JVC
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1159 AM CST SAT DEC 29 2012
AVIATION... /18Z TAF ISSUANCE/
A TROUGH OF LOW PRESSURE ALOFT IS PASSING ACROSS EASTERN MN ATTM.
LIGHT SNOW ACROSS THE TWIN CITIES WILL MOVE ACROSS KRNH AND KEAU
EARLY IN THE AFTERNOON WITH 2SM VSBYS ALONG WITH CEILINGS DIPPING
BELOW 1K FEET. SUBSIDENCE IN THE WAKE OF THE TROUGH IS HELPING TO
DIMINISH CLOUDINESS TO OUR WEST. SOME VFR CEILINGS IN THE 035-040
FOOT RANGE IN WEST CENTRAL MN WILL BE MOVING THROUGH KAXN AND
KRWF. SOME -SN STILL POSSIBLE FOR A FEW HOURS AT KAXN ALONG MVFR
CEILINGS. CONFIDENCE ON FORECAST FOR TONIGHT IS LOW. HIGH
PRESSURE WILL BE PASSING BY WITH LOW LEVEL WARMING DURING THE
OVERNIGHT HOURS. CONCERN IS THAT STRATUS AND FOG MAY DEVELOP FOR
THE MN TAF SITES SIMILAR TO THAT OF THIS MORNING IN EASTERN SD.
VARIOUS GUIDANCE IN THE SHORT TERM IS INDICATING VFR. FOR
NOW...DROPPED VSBYS TO MVFR DURING THE EVENING WITH FEW-SCT CLOUDS
IN THE 008-015 RANGE. WEST WINDS THIS AFTERNOON 7-9 KNOTS BACKING
SW 3-5 KNOTS TONIGHT AND THEN S 8-10 KNOTS ON SUNDAY.
KMSP...MAIN SNOW AREA IS NOW EAST OF THE AIRFIELD WITH BKN-OVC
MVFR CEILINGS. POTENTIAL FOR SCT CONDITIONS IN THE 19Z-21Z TIME
FRAME. VFR CEILINGS IN THE 035-040 POSSIBLE LATE THIS AFTERNOON
AND EARLY TONIGHT. MVFR VSBY LIKELY LATE TONIGHT AND SUNDAY
MORNING.
/OUTLOOK FOR KMSP/
SUN...VFR. WINDS S 5-10 KTS.
MON...MVFR CIGS. WINDS NW 15 TO 20 KTS.
TUE...VFR. WINDS WSW 10 KTS.
&&
.DISCUSSION... /ISSUED ISSUED 427 AM CST SAT DEC 29 2012/
.SHORT TERM...TODAY THROUGH MONDAY NIGHT
STRATUS HAS REDEVELOPED ACROSS ALL OF MN AND WI OVERNIGHT WITH
ONLY SMALL SIGNS OF ERODING OVER FAR WRN MN EARLY THIS MORNING.
AREAS OF FREEZING FOG HAVE ALSO FORMED WITH SOME VISIBILITY
RESTRICTIONS DOWN TO 1/4 MILE. BECAUSE THE DGZ IS SO LOW AND
SATURATED...HAVE ALSO SEEN SEVERAL OBS REPORTING FLURRIES OR LIGHT
SNOW SHOWERS.
CONFIDENCE IS QUITE LOW WITH RESPECT TO TIMING THE CLOUD
DISSIPATION TODAY. NAM AND RAP ARE MOST PESSIMISTIC KEEPING LOW
CLOUDS IN THROUGH THE AFTERNOON. GFS AND LAMP ARE A LITTLE MORE
OPTIMISTIC WITH CLEARING THIS AFTERNOON. GIVEN THE TIME OF YEAR
AND HOW SOLID IT LOOKS ON SATELLITE...AM LEANING TOWARD THE MORE
PESSIMISTIC SOLUTION. AS A RESULT OF THE WIDESPREAD
STRATUS...TEMPERATURES REMAINED A BIT WARMER THAN ANTICIPATED
OVERNIGHT AND AS OF 4 AM ARE NEAR FORECAST HIGHS FOR TODAY. LITTLE
DIURNAL CLIMB EXPECTED THOUGH DUE TO SAID CLOUDS AND WEAK CAA SO
STILL FORECASTING HIGHS IN THE TEENS.
CLEARING SHOULD ARRIVE TONIGHT ACCORDING TO ALL AVAILABLE
GUIDANCE. THERE IS SOME CONCERN HOWEVER THAT IF THEY DO NOT
DISSIPATE THIS AFTERNOON THEY MAY STICK AROUND THROUGH TONIGHT AS
THE INVERSION INTENSIFIES. ASSUMING THE GUIDANCE IS RIGHT...
TONIGHT SHOULD BE A COLD ONE AS A RIDGE AXIS SETTLES OVERHEAD.
LOWS IN THE SINGLE DIGITS ABOVE AND BELOW ZERO ARE EXPECTED.
LOW PRESSURE WILL ZIP ACROSS SOUTHERN CANADA SUNDAY WITH A COLD
FRONT ARRIVING SUNDAY EVENING. WAA AHEAD OF THIS SYSTEM WILL BRING
A QUICK REBOUND OF TEMPS BACK INTO THE 20S. COULD SEE SOME
FLURRIES ACROSS CNTRL MN AND WI WHERE MOISTURE DEPTH AND FORCING
SHOULD BE GREATER...OTHERWISE THE COLD FRONT WILL BE DRY. VERY
STRONG CAA BEHIND THE FRONT WILL BRING STEADY OR FALLING TEMPS
INTO THE SINGLE DIGITS COME MONDAY AS 925 MB TEMPS CRASH TO -18C.
A RIDGE WILL SETTLE OVERHEAD MONDAY NIGHT. CLEAR SKIES...LIGHT
WINDS...AND A VERY COLD AIRMASS SHOULD ALLOW MOST PLACES TO
PLUMMET INTO THE TEENS BELOW ZERO...AND PERHAPS TO 20 BELOW IN
SOME OF THE COLDEST LOCATIONS. THE PLACEMENT OF THE RIDGE WILL BE
CRUCIAL. GFS HAS BEEN FURTHEST EAST WITH IT AND BRINGS WAA ACROSS
WRN MN LATE MONDAY NIGHT WITH THE COLDEST TEMPS ACROSS WI.
NAM/DGEX/GEM/ECMWF HAVE BEEN A BIT FURTHER WEST WITH THE CORE OF
THE COLD AIR. INTERESTINGLY...THE 29.00Z NAM/GEM...28.18Z
DGEX...AND 28.12Z EURO HAD GOOD CONSISTENCY WITH TEMPS RANGING
FROM NEAR -22F OVER ERN CHIPPEWA CO MN...TO ABOUT -5F IN THE TWIN
CITIES METRO. LEANED TOWARD THOSE RAW SOLUTIONS FOR THIS FORECAST
AND DISCARDED THE GFS. 29.00Z EURO CAME IN A TAD WARMER. WITH
TEMPS SUCH AS THESE...IT WON/T TAKE MUCH TO BRING THE WIND CHILL
WAY DOWN. EVEN A 5 KT WIND WOULD RESULT IN -20 TO -30F.
.LONG TERM...NEW YEARS DAY THROUGH FRIDAY
RIDGE SETTLES SOUTH WITH RETURN FLOW ALLOWING ANOTHER QUICK
REBOUND OF TEMPS BACK INTO THE TEENS ON NEW YEARS DAY.
ANOTHER SYSTEM ZIPPING ACROSS THE NORTHERN GREAT LAKES WILL BRING
A WEAK FRONT SOUTH ON TUESDAY. MEANWHILE...YET ANOTHER SYSTEM
WILL DIVE SOUTHEAST INTO THE NORTHERN PLAINS TUESDAY NIGHT AND
BRING A STRONG COLD FRONT THROUGH WEDNESDAY OR WEDNESDAY EVENING.
THIS SYSTEM MAY BRING A BIT OF LIGHT SNOW BEFORE ANOTHER SURGE OF
ARCTIC AIR SPILLS SOUTH. COULD SEE A SIMILAR SCENARIO FROM EARLIER
IN THE WEEK WITH LOWS IN THE TEENS BELOW ZERO THURSDAY MORNING AND
HIGHS IN THE SINGLE DIGITS. THIS ONE HAS A LITTLE MORE UNCERTAINTY
WITH THE POTENTIAL FOR CLOUDS TO LINGER SO DID NOT GO TOO CRAZY
WITH TEMPERATURES YET.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
RAH/BB
AREA FORECAST DISCUSSION
NWS BINGHAMTON NY
1253 PM EST SAT DEC 29 2012
.SYNOPSIS...
LOW PRESSURE WILL TRACK ACROSS THE MID ATLANTIC REGION THIS AFTERNOON,
SPREADING 3 TO 7 INCHES OF SNOW ACROSS MUCH OF UPSTATE NY AND
NORTHEAST PA. A NORTHWEST FLOW BEHIND THIS LOW PRESSURE SYSTEM WILL
GENERATE LAKE EFFECT SNOW SHOWERS FOR UPSTATE NEW YORK FOR THE
REST OF THE WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
IR AND WATER VAPOR IMAGERY SHOW AN IMPRESSIVE UPPER LEVEL WAVE
MOVING INTO WRN PA/NY W VA. COOLING CLOUD TOPS CONTINUE ACRS NY
AND NRN PA ASSCTD WITHE STRONG MID-LEVEL ASCENT. THE TROP PRESSURE
ON THE 1.5 PV SURFACE WAS DOWN TO 560 MB AS PER THE LATEST RAP IN
THE ERN OH VLLY. THIS MATCHED VERY WELL WITH THE SATELLITE DEPICTION
OF THE CENTER OF THE UPPER LEVEL CRLCN. THIS UPPER LEVEL WAVE WILL
MOVE INTO ERN NY BY 2-3Z AS ANOTHER UPR LVL PV INTRUSION...DOWN
TO 490 MB...DEVELOPS OFF THE COAST INDICATIVE OF THE TRANSFER OF THE
MAIN ENERGY TO THE DEVELOPING COASTAL LOW. PRESENTLY THE UPPER
LEVEL WAVE IN THE ERN OH VLLY HAD A SFC REFLECTION MOVING INTO WRN PA
THAT WILL EVENTUALLY GET SWALLOWED UP BY THE DEEPENING SFC CYCLONE
OFF THE E COAST BY THIS EVENING. THIS LOW WILL BE WELL EAST OF THE NJ
COAST BY 00Z. BELIEVE THE HEAVIEST SNOW WILL TAPER DOWN BY LATE
AFTERNOON AS THE MAIN LIFTING WITH THIS UPPER LEVEL WAVE SHIFTS TO
THE EAST. LIGHTER SNOWS WILL PERSIST INTO THE EARLY EVENING.
THE SATELLITE CONTS TO REVEAL THAT THE DEEPER MOISTURE REMAINS OFF
THE EAST COAST AND WAS THE MAIN REASON WHY THIS STORM LIKELY WON/T
BECOME A MAJOR EVENT FOR OUR AREA AS THE UPPER LEVEL WAVE JUST IS
NOT TAPPING INTO THE DEEPER MOISTURE OFFSHORE FOR OUR AREA.
BELIEVE MOST OF OUR FORECAST AREA SEES BETWEEN 4 AND 7
INCHES...WITH BETWEEN 3 AND 6 INCHES IN SCRANTON/WILKES BARRE
AREA/POCONOS WHERE CURRENT SNOW REPORTS SHOW THAN LESS THAN 1
INCH HAS OCCURRED THERE SO FAR. THE BULK OF THEIR SNOW WILL COME
WITH A SIGNIFICANT BAND OF HEAVIER SNOW MOVING INTO SC PA ATTM.
WILL CONTINUE WITH WINTER WEATHER ADVISORIES ALL ZONES. IF SNOW
REPORTS APPROACH 5-6 ICNHES BY 1 PM AND RADAR TRENDS CONTINUES TO
SHOW REDEVELOPMENT TO THE SOUTHWEST MAY HAVE TO UPGRADE TO WINTER
STORM WARNING IN SOME AREAS. DON/T THINK THIS WILL BE THE
CASE...BUT IT COULD COME CLOSE SOME AREAS IN C NY/NRN PA. LATEST
12Z NAM SNOWFALL PROJECTIONS SHOW A SOLID 4-6 INCHES SUPPORTING ADVY.
MOST OF OUR SNOWFALL REPORTS IN NY AND FAR NRN PA ARE 2-3 INCHES
WITH THE SCRANTON AREA LESS THAN 1 INCH AS STATED ABOVE.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
CONTINUING WW ADVISORY TODAY. LATEST MODEL PROGS SUGGEST A VERY
WIDESPREAD SWATH OF 3 TO 5 INCHES OF SNOW ACROSS FA, WITH
POTENTIAL FOR 6-7 INCHES OVER THE VERY HIGH TERRAIN OF THE POCONOS
AND WESTERN CATSKILLS.
THERE ARE CONCERNS WHICH COULD HINDER SNOWFALL AMOUNTS, INCLUDING
RELATIVELY SHALLOW MOIST LAYER AND FAST MOVEMENT OF SYSTEM.
HOWEVER ATMOSPHERIC DYNAMICS ARE VERY STRONG AND CONFIDENCE IS NOW
HIGH FOR ADVISORY ACCUMS. OF NOTE IS IMPRESSIVE PV INTRUSION
VISIBLE DOWN TO 600-500MB ON NAM.
STORM WILL PULL OUT THIS EVENING, WITH A COLD NORTHWEST FLOW
GENERATING LAKE BANDS OFF OF ONTARIO. PRE-EXISTING LL MOIST LAYER
COMBINED WITH LAKE INDUCED INSTABILITY (850MB TEMPS -10C TO -12C)
WILL BE SOMEWHAT TEMPERED BY SHEAR IN THE LOW LAYERS. EXPECT AN
INCH OR TWO OF LAKE SNOW BY SUNDAY AFTERNOON, WHEN INVERSION
BUILDS DOWN AND HIGH PRESSURE STARTS TO LOCK IN.
SUNDAY NIGHT INTO MONDAY...HIGH PRESSURE, FAIR WEATHER, AND A
BRIEF MODERATION IN TEMPERATURES BACK TOWARD SEASONAL NORMS. SHORT
WAVE APPROACHES MONDAY NIGHT, GENERATING LIGHT SNOW SHOWERS.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
2 AM UPDATE...
VRY FEW CHGS NEEDED TO LONG TERM AS IT APPEARS TO BE A PROLONGED
PD OF LK EFFECT ACTIVITY EACH DAY UNDER COLD NW FLOW DROPPING
SOUTH OUT OF CANADA. CDFNT LOOKS TO MV THRU ON THURSDAY, THUS HV
LOWERED MIN TEMPS FOR FRI MRNG AND AGAIN FOR MAXES ON FRIDAY.
SINGLE DIGITS APPEAR LKLY FOR FRIDAY MORNING WITH PERHAPS SOME
LOCALES DROPPING BLO ZERO.
PREV DISCO BLO...
1 PM UPDATE...
FOLLOWED HPC GUIDANCE. A COLD SPELL WITH BELOW NORMAL TEMPERATURES
BUT NO MAJOR CYCLONES AND HEAVY SNOW. MOSTLY LAKE EFFECT. MONDAY
NIGHT STARTS WITH A COLD FRONT BRINGING A REINFORCING SHOT OF COLD
AIR. LIGHT SNOW WITH THE FRONT THEN LAKE EFFECT. THE REST OF THE
EXTENDED MORE OF THE SAME. ANOTHER COLD FRONT THU OR FRI BUT AGAIN
NOT TAPPING ANY ATLANTIC OR GULF MOISTURE. COLDEST DAY OF WEEK
FRIDAY WITH LOWS IN SINGLE DIGITS.
&&
.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
1230 PM UPDATE...
IFR VSBYS MAJORITY OF THE DAY WITH SNOW HEAVY AT TIMES. IFR CIGS
TOO MOSTLY AT THE HIGHER ELEV SITES OF BGM AND ITH. SOME VSBYS
UNDER A QUARTER MILE IN HEAVY SNOW THIS AFTN WILL DROP CONDITIONS
BELOW FLIGHT MINIMUMS. IFR TO CONTINUE THROUGH THE EVENING BEFORE THE
SNOW TAPERS OFF LATE TONIGHT. LOW LEVEL FLOW SHIFTS TO NW THIS
EVENING PROVIDING LAKE EFFECT ENHANCEMENT TO THE LINGERING SNOW.
FOR SUNDAY MVFR CONDITIONS IN NY WITH LAKE EFFECT SNOW SHOWERS AND
VFR AT KAVP.
E WINDS AT 5 TO 10 KTS SHIFTING TO NW LATE THIS AFTN...THEN
CONTINUING TONIGHT. SUNDAY NW WINDS AT 10 TO 15 KTS.
OUTLOOK...
SUN AFTN AND NGT...MVFR/IFR POSSIBLE FOR CNY TERMINALS...IN LAKE
EFFECT SN ACTIVITY.
MON...VFR.
MON NGT TO WED NGT...MVFR/IFR ESPECIALLY FOR CNY TERMINALS.
THU...VFR.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...WINTER WEATHER ADVISORY UNTIL 9 PM EST THIS EVENING FOR
PAZ038>040-043-044-047-048-072.
NY...WINTER WEATHER ADVISORY UNTIL 9 PM EST THIS EVENING FOR NYZ009-
015>018-022>025-036-037-044>046-055>057-062.
&&
$$
SYNOPSIS...DJP
NEAR TERM...DJN
SHORT TERM...DJP
LONG TERM...PVN/TAC
AVIATION...TAC
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
1115 AM EST SAT DEC 29 2012
.SYNOPSIS...
A WIDESPREAD 3 TO 5 INCH SNOWFALL WILL OCCUR TODAY. A FEW
LOCATIONS COULD GET UP TO 6 INCHES OF SNOW FROM THIS FAST-MOVING
SYSTEM. WINDS WILL TURN TO THE NORTHWEST THIS EVENING AND BECOME
GUSTY WITH SNOW SHOWERS LIKELY DOWNSTREAM OF LAKE ERIE AND IN THE
LAUREL HIGHLANDS. NEXT WEEK LOOKS QUIET WITH ONLY A COUPLE OF WEAK
WEATHER SYSTEMS PASSING BY. THE BIG STORY LATER NEXT WEEK WITH BE
THE POSSIBILITY OF VERY COLD AIR ENTERING THE STATE.
&&
.NEAR TERM /UNTIL 7 PM THIS EVENING/...
THE WESTERN SURFACE LOW IS JUST WEST OF JOHNSTOWN. THE DRY SLOW
IS CLOSE TO THIS FEATURE AND SNOW IN WEST-CENTRAL AREAS HAS
DIMINISHED. THE SHORT-WAVE IS STILL TO THE WEST SO ANOTHER INCH OR
SO OF SNOW IS POSSIBLE UNTIL IT PASSES TO THE EAST EARLY THIS
AFTERNOON. THE SURFACE LOW DEVELOPING ALONG THE COAST IS TAKING
OVER. SECOND MILLER-B WINTER STORM EVOLUTION THIS WEEK.
THE SECONDARY LOW HAS BANDS TO ITS NORTH AND WEST WHICH SHOULD
BRING A PERIOD OF ENHANCED SNOW FALL TO ADAMS...YORK...AND
LANCASTER COUNTIES WHICH SHOULD GET THEM INTO THE 3-4 INCH RANGE
EARLY THIS AFTERNOON. MODIFIED GRIDS TO SHOW THIS.
THE RAP AND HRRR CONTINUE TO SHOW THE SNOW PULLING OUT OF THE REGION
RAPIDLY IN THE 1 PM TO 3 PM RANGE FROM SW TO ENE. INTENSITIES
REALLY DROP OFF FAST BASED ON RAP/HRRR SYNTHETIC RADAR AFTER ABOUT
2 PM EVEN IN THE EAST.
BY ABOUT 5-6 PM ANY ACCUMULATING SNOW SHOULD BE ABOUT OVER. MOSTLY
LIGHT SNOW AND FLURRIES AFTER 5-6 PM OVER MOST OF CWA. LINGERING
IN THE MOUNTAINS.
FOR MOST LOCATIONS THE HEAVIEST SNOW HAS LIKELY FALLEN...EXCEPT IN
THE SOUTHEAST WHERE THE NEXT 0-3 HOURS COULD BE THE BEST.
&&
.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SUNDAY/...
MONITORING SNOW SHOWER AND ACCUMULATING SNOW IN SW MOUNTAINS AND
NW PA DURING THIS PERIOD. MOST OTHER AREAS TO EAST WILL SEE LITTLE
OR NOW SNOW AFTER 9 PM GIVE OR TAKE 1-3 HOURS. CONSIDERING AND
ADVISORY IN SW MTNS SUNDAY.
PREVIOUS DISCUSSION....THE LOW DEPARTS AND
DEEPENS OFF THE EAST COAST THIS EVENING. RESIDUAL MOISTURE FROM
THE EXITING LOW...COUPLED WITH W/NW FLOW AND UPSLOPE TOPOGRAPHIC
ENHANCEMENT WILL MAKE SNOW SHOWERS ACROSS THE SNOW BELT AND IN THE
LAUREL HIGHLANDS. THESE SHOWERS SHOULD BE MAINLY LIGHT AND SHOULD
DIE DOWN SUNDAY EVENING. THOSE FAVORED/UPSLOPE LOCATIONS IN THE
LAURELS AND DOWNWIND OF THE LAKES COULD PICK UP ANOTHER INCH OR
TWO TONIGHT AND ANOTHER INCH SUNDAY MORNING BEFORE THE FLOW
BECOMES ANTICYCLONIC. THOSE VALUES SHOULD BE JUST SUB- ADVISORY
FOR THEM. BUT ALLOWING LEEWAY...THE CURRENT ADVY FOR THOSE AREAS
COULD BE EXTENDED IF NECESSARY TO COVER THE ADDITIONAL
LAKE/UPSLOPE SNOW. OTHERWISE...SUNDAY WILL BE A BREEZY BUT FAIR
DAY FOR THE REST OF THE AREA. GUSTS COULD BE INTO THE L30S IN THE
SRN MTS AND EAST...BUT NO WORRY OF WIND ADVY. MAX TEMPS ON SUNDAY
WILL BE SIMILAR TO TODAY.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
THE FLOW WILL SHIFT TO A MORE ZONAL PATTERN AS ANOTHER SYSTEM
MAKES ITS WAY TOWARD THE REGION FOR MONDAY NIGHT/NEW YEARS EVE.
THE CURRENT MODELS ARE FAIRLY CONSISTENT AND HAVE SUFFICIENT PWATS
AND LIFT FROM A JET STREAK TO CREATE SNOW SHOWERS OVER AT LEAST
THE WESTERN HALF OF THE AREA MON NIGHT AND TUES MORNING. A FEW
NORTHERN STREAM FEATURES WILL CROSS THE LOWER GREAT LAKES AROUND
MID-WEEK AND MAKE LAKE EFFECT SHOWERS. AN ARCTIC AIR MASS BEGINS
TO MOVE THROUGH SOUTHERN CANADA AND DECREASING 850MB TEMPERATURES
WILL CONTINUE THROUGH THE LATTER HALF OF THE WEEK. CURRENT RUNS
HAVE PA UNDER M16C TEMPERATURES AT 850MB FRIDAY MORNING. THE GFS
AND EC PROPAGATE ANOTHER TROUGH THROUGH PENNSYLVANIA FRIDAY.
EXPECT HIGH TEMPERATURES THIS WEEK TO BE AT OR BELOW
FREEZING...WITH HIGHS IN THE UPPER TEENS POSSIBLE BY THE END OF
NEXT WEEK. COUPLE THE LOW TEMPS WITH THE GUSTY FLOW...AND WIND
CHILLS COULD BE AN ISSUE DURING THIS TIME FRAME. LOWS THROUGH THE
LATER HALF OF THE WEEK SHOULD BE IN THE LOW TEENS.
&&
.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
THE SNOW HAS REDUCED VISIBILITIES AND CIGS ACROSS THE ENTIRE
REGION. SNOW RATES OF 1 TO 2 INCHES PER HOUR BENEATH BANDS WILL
POSE DEICING ISSUES TOO. CONDITIONS WILL REMAIN POOR THROUGH AT
LEAST 17Z TODAY.
SNOW RATES SHOULD STEADILY DIMINISH SOUTHWEST TO NORTH EAST THIS
AFTERNOON AND EVENING. VISIBILITIES SHOULD RISE TO OVER 3 MILES
LATER THIS EVENING IN MANY SOUTHERN LOCATIONS. PERHAPS VFR A FEW
HOURS BEFORE MIDNIGHT IN THE 02 TO 03Z TIME-FRAME AS THE STORM AND
SNOW LIFTS TO OUR NORTH AND EAST.
GUSTY WINDS APPEAR LIKELY OVERNIGHT TONIGHT INTO SUNDAY WITH
SCATTERED SNOW SHOWERS DEVELOPING IN THE WESTERN AND NORTHWESTERN
MTNS. NWLRY UPSLOPE FLOW WILL LIKELY KEEP FLYING CONDS AT KJST AND
KBFD MARGINAL AFTER THE STORM WITH LOW CLOUDS AND PERIODS OF
LOWERED VISIBILITIES.
MOST OTHER LOCATIONS SHOULD HAVE GENERALLY GOOD FLYING CONDITIONS SUNDAY.
OUTLOOK...
SUN...SHSN AND REDUCED FLIGHT CONDS POSSIBLE WESTERN AND NORTHERN
MTNS.
MON...NO SIG WX EXPECTED.
TUE...CFROPA POSSIBLE. SHSN REDUCED CIGS/VI`S AND GUSTY WINDS
POSS.
WED...MAINLY VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR
PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-
049>053-056>059-063>066.
&&
$$
SYNOPSIS...DANGELO/LA CORTE
NEAR TERM...GRUMM
SHORT TERM...GRUMM/DANGELO
LONG TERM...DANGELO/CERU
AVIATION...GRUMM/GARTNER
AREA FORECAST DISCUSSION...UPDATED
NWS MILWAUKEE/SULLIVAN WI
1154 AM CST SAT DEC 29 2012
.UPDATE...
A SHORTWAVE SWINGING ACROSS EASTERN MN AND IOWA INTO WESTERN WI LATE
THIS MORNING IS PRODUCING SNOW SHOWERS WITH VISIBILITIES DOWN TO 4
NM AT VARIOUS SITES. THE SHORTWAVE WILL PROGRESS EAST WITH THE UPPER
TROUGH THIS AFTERNOON. THEREFORE...INCREASED THE POPS ACROSS ALL OF
THE FORECAST AREA TO MENTION OCCASIONAL LIGHT SNOW OR SCATTERED SNOW
SHOWERS.
MEANWHILE...THE REMNANTS OF THE SYSTEM LAST NIGHT WITH THAT LAKE
ENHANCEMENT BAND THAT STALLED OVER EAST CENTRAL WISCONSIN IS MAKING
ITS WAY SOUTHWARD THROUGH KENOSHA THIS MORNING. THE SNOW SHOWERS
WILL CONTINUE TO GRADUALLY SHIFT SOUTHEAST THROUGH THE AFTERNOON AND
DIMINISH. WINDS IN THE EAST MAY SHIFT TO NORTH FOR A TIME...BUT THEN
SHIFT BACK TO THE NORTHWEST LATER THIS AFTERNOON AND TO THE WEST
TONIGHT.
A FEW FLURRIES MAY LINGER INTO THE EARLY EVENING IN SOUTHEAST WI
UNTIL THAT UPPER TROUGH COMPLETELY CLEARS THE STATE. THEN SKIES WILL
GRADUALLY SCATTER OUT OVERNIGHT AND SHOULD BECOME CLEAR SUNDAY
MORNING WITH HIGH PRESSURE MOVING IN.
&&
.AVIATION/18Z TAFS/...
THE AREA OF SNOW SHOWERS IN EASTERN WI WILL GRADUALLY DIMINISH THIS
AFTERNOON. MEANWHILE...ANOTHER AREA OF LIGHT SNOW SHOWERS WILL
SPREAD ACROSS SOUTHERN WI LATER THIS AFTERNOON. CIGS SHOULD REMAIN
IN FUEL ALTERNATE CATEGORY FOR THE DURATION. VSBYS COULD DROP TO
MVFR AT TIMES WITH SNOW THIS AFTERNOON. SNOW FLURRIES MAY LINGER IN
SOUTHEAST WI THROUGH 9 PM THIS EVENING. OTHERWISE...ALL SNOW SHOULD
END BY EARLY EVENING.
STRATUS WILL BE SLOW TO CLEAR TONIGHT...BUT EXPECT IT TO SCATTER OUT
EARLY SUNDAY MORNING AS HIGH PRESSURE MOVES IN.
&&
.PREV DISCUSSION... /ISSUED 330 AM CST SAT DEC 29 2012/
SHORT TERM...
TODAY-FORECAST CONFIDENCE MEDIUM
INVERTED SURFACE TROUGH AND LAKE ENHANCED BAND OF -SN TO
OCCASIONALLY MODERATE SN WILL AFFECT ERN CWA THIS MRNG AS THEY PIVOT
SOUTHWARD. BOTH NAM AND GFS SHOWING LOW LEVEL FN VECTOR RESPONSE TO
FRONTOGENETICAL FORCING TIED TO SURFACE TROUGH EARLY THIS MRNG IN
THE EAST WITH THESE FEATURES. HENCE ENOUGH CONFIDENCE THAT -SN WL
BE FALLING AFTER 12Z TO BUMP UP TO CATEGORICAL WORDING IN THE
EAST...WITH ADDITIONAL SNOWFALL MOSTLY LESS THAN AN INCH. EXTENDED
WINTER WX ADVY FOR SHEBOYGAN COUNTY TO 13Z TO ACCOUNT FOR LAKE
ENHANCED BAND MOVING THRU. CURRENT VSBY DOWN TO 3/4NM AT KSBM.
KMKX AND TMKE RADARS SHOWING 15 TO 20DBZ TIED TO THIS ENHANCED BAND
OVER NORTHEAST CWA. MORE IMPRESSIVE 25-30DBZ BAND HAS REMAINED
OFFSHORE OVER LAKE MI. NOT IMPOSSIBLE THIS COULD MOVE SOUTHWEST AND
AFFECT SOUTHERN OZAUKEE AND MILWAUKEE COUNTIES AROUND 12Z WHEN NAM12
SHOWS STRONG OMEGA AFFECTING THIS AREA. FORTUNATELY...LOW LEVEL
WINDS CONTINUE TO BACK THROUGH THE MORNING AND AFTERNOON...NOT
ALLOWING THE STRONG CONVERGENCE TO FOCUS ON ONE AREA FOR A PROLONGED
PERIOD OF TIME. BY 20Z...LAKE ENHANCED SNOWFALL AND SURFACE TROUGH
WILL HAVE SAGGED SOUTH OF THE AREA WITH LINGERING PATCHY -SN OR
FLURRIES IN ERN CWA.
TONIGHT-FORECAST CONFIDENCE MEDIUM
NORTHWEST WINDS IN THE LOW TO MID LEVELS WILL USHER DRIER AIR INTO
THE AREA OVERNIGHT AS SHORT WAVE RIDGING BUILDS UPSTREAM OVER THE
NORTHERN PLAINS. HOWEVER LINGERING LOW LEVEL MOISTURE AND THERMAL
TROUGH MAY RESULT IN STRATUS STICKING AROUND OR POSSIBLY
REDEVELOPING FOR A TIME OVERNIGHT...HENCE LOW CONFIDENCE ON AMOUNT
OF OVERNIGHT CLEARING AT THIS TIME.
SUNDAY-FORECAST CONFIDENCE HIGH
POLAR RIDGE OVERHEAD FIRST THING WITH A COLD START...BUT THEN
STRONG WARM ADVECTION OCCURRING DURING THE DAY. IN FACT...925 MB
TEMPS WARM TO ABOUT -2C...SUGGESTING TEMPERATURES APPROACHING 30.
SEEMS THAT MIXING WILL BE PRETTY MINIMAL WITH SNOW COVER SO MID
20S MORE LIKELY.
MONDAY-FORECAST CONFIDENCE MEDIUM
FRONT COMES THROUH FIRST THING WITH COLD ADVECTION DURING THE DAY.
925 MB TEMPS DROP FROM -4C TO -10C DURING THE DAY...IMPLYING THAT
READINGS MAY HOLD STEADY OR DROP IN THE MIDDAY AND EARLY
AFTERNOON. CONFIDENCE OVERALL WOULD BE HIGH BUT NAM HAS A SUBTLE
DIFFERENCE FROM OTHER MODELS. NAM KEEPS UPPER RIDGING STRONGER IN
EASTERN STATES AND IS A LITTLE SLOWER WITH NORTHERN BRANCH TROUGH
IN DAKOTAS...ALLOWING A STRONGER MOISTURE SURGE AHEAD OF
CONFLUENCE ZONE A TAD FARTHER NORTH THAN ALL OTHER MODELS. NAM
WOULD ALLOW A BIT OF SNOW IN THE SOUTHEAST BUT OTHER MODELS DRY
AND WILL KEEP IT DRY GIVEN THAT ECMWF AND GFS ARE USUALLY MORE
TRUSTWORTH BEYOND 36 HOURS THAN NAM.
LONG TERM...
TUESDAY-FORECAST CONFIDENCE HIGH
COLD SHOT WITH 925 MB TEMPS AROUND -14C SUGGESTS NEAR ZERO MORNING
TEMPERATURES. CIPS ANALOGS HAVE 40-50% CHANCE OF BELOW ZERO LOWS
AND ABOUT 30% CHANCE OF -20C OR COLDER WIND CHILLS. CURRENTLY WE
ARE LOOKING AT ABOUT -15C WIND CHILLS IN THE WEST SO GETTING CLOSE
TO ADVISORY LEVELS.
WEDNESDAY-FORECAST CONFIDENCE MEDIUM
MODELS HAVE A CLIPPER SYSTEM MOVING THROUGH...WITH GFS FASTER AND
FARTHER NORTH WITH GEMNH AND ECMWF SLOWER AND FARTHER SOUTH. SINCE
GFS IS TYPICALLY FASTER THIS IS NOT SURPRISING. 00Z GFSE HAD HIGH
STANDARD DEVIATION OF ABOUT 10MB OVER MN...AND A COUPLE OF MEMBERS
WITH CLIPPER TRACKING SOUTH LIKE OTHER GUIDANCE. ADDED 20-30%
CHANCE OF SNOW DURING THIS PERIOD GIVEN ECMWF TRACK AND FACT THAT
COLD AIRMASS WITH DENDRITE ZONE AROUND 850 MB WILL MAKE IT EASY TO
PRODUCE SNOW.
THURSDAY-FORECAST CONFIDENCE MEDIUM
SHOULD BE COLD NO MATTER WHAT HAPPENS WITH CLIPPER WITH 925 MB
TEMPS AROUND -15C. COULD HAVE ANOTHER BELOW ZERO NIGHT AWAY FROM
THE LAKE ESPECIALLY IF THE POLAR RIDGE BUILDS IN AS FORECAST AND
SKIES CLEAR OUT. WIND CHILLS WILL AGAIN FLIRT WITH ADVISORY LEVELS
IN -10 TO -20C RANGE.
FRIDAY-FORECAST CONFIDENCE MEDIUM
BUILDING RIDGE ALOFT AND INTRUSION OF WESTERLY LOW LEVEL FLOW AND
MODIFIED PACIFIC AIRMASS INDICATES POTENTIAL FOR MODERATION.
PROBLEM IS THAT WITH EXTENSIVE SNOW COVER STRONG INVERSION COULD
LIMIT HOW MUCH MIXING DOWN OF WARM AIR OCCURS SO IT SHOULD BE
MILDER BUT MAY NOT GET MUCH ABOVE NORMAL.
AVIATION/12Z TAFS/...
AREAS OF -SN WL KEEP VSBYS AND CIGS IN MVFR OR
LOWER CATEGORY FOR A TIME THIS MRNG IN ERN TAF SITES. AREAS OF -SN
WL DIMINISH LATER THIS MRNG AND AFTER WITH IMPROVING CIGS EXPCD
TNGT. RAP GUIDANCE HAS BEEN THE BEST IN HANDLING LOW LEVEL RH LATELY
AND KEEPS LOW CLOUDS IN THRU 00Z/30. CONFIDENCE LOW ON CLEARING
TNGT AS EXTENSIVE STRATUS SHIELD/RESIDUAL MOISTURE CAUGHT IN
VICINITY OF RIDGELINE ACROSS MN/IA...WL LIKELY WORK ITS WAY EWD
TNGT.
MARINE...EXPECT WIND DIRECTION TO VARY FROM THE NORTHWEST TO NORTH
TO NORTHEAST THIS MORNING AS SURFACE TROUGH SLIPS SOUTH ACROSS
NEARSHORE AREAS. SUSTAINED WINDS AND GUSTS ARE EXPECTED TO REMAIN
BELOW 20KTS. NEXT POTENTIAL FOR STRONGER WIND GUSTS LATER SUNDAY
NIGHT AND MONDAY AHEAD OF NEXT LOW PRESSURE SYSTEM APPROACHING
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
$$
UPDATE...MRC
TODAY/TONIGHT AND AVIATION/MARINE...MBK
SUNDAY THROUGH FRIDAY...COLLAR