Forecast Discussions mentioning any of
"HRRR" "RR" "RUC13" "RUC" received at GSD on 12/20/11
AREA FORECAST DISCUSSION
NWS NEW YORK NY
356 PM EST SUN DEC 18 2011
.SYNOPSIS...
A HIGH PRESSURE RIDGE WILL DRIFT OVER THE REGION TONIGHT...AND
OFFSHORE ON MONDAY. A COLD FRONT WILL PASS MONDAY NIGHT. HIGH
PRESSURE BUILDS OVER THE AREA TUESDAY. A WARM FRONT APPROACHES
FROM THE SOUTH TUESDAY NIGHT...THEN LIFTS TO THE NORTH
WEDNESDAY...FOLLOWED BY A COLD FRONT WEDNESDAY NIGHT...AS AN AREA
OF LOW PRESSURE PASSES TO OUR NORTH. HIGH PRESSURE THEN BUILDS IN
TO OUR NORTH THURSDAY THROUGH SUNDAY...AS A COUPLE OF LOW PRESSURE
SYSTEMS PASS TO OUR SOUTH FRIDAY AND THEN LATE NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 7 PM THIS EVENING/...
AT 20Z A 1026 HIGH WAS CENTERED NEAR MONTREAL. SKIES WERE CLEAR
ACROSS THE CWA. CLEAR SKIES WILL REMAIN LOCKED IN THRU
7PM...ALLOWING TEMPS TO DROP SHARPLY AFT DARK AS WINDS DECOUPLE.
&&
.SHORT TERM /7 PM THIS EVENING THROUGH TUESDAY NIGHT/...
HIGH PRESSURE RIDGING FROM ERN CANADA TO THE GULF COAST WILL SLOWLY
TRANSLATE EWD OVERNIGHT. WINDS WILL GO CALM AS THE RIDGE TRAVERSES
THE CWA. THIS WILL ALLOW TEMPS TO DROP TO SOME OF THE COLDEST
READINGS OF THE YEAR. ONLY LIMITING FACTOR WILL BE CLOUDS OVER THE
GREAT LAKES INTO WRN PA AS THEY SPREAD EWD TOWARDS THE CWA. WITH
SUBSIDENCE OVER THE CWA HOWEVER...MOST OF THE LOW AND MID CLOUD
POTENTIAL WILL BE MITIGATED...LEAVING MAINLY HIGH CLOUDS OVER THE
AREA TNGT. TEMPS WERE THEREFORE TRENDED TOWARDS THE LOWER GUIDANCE
NUMBERS...AND HAVE TWEAKED READINGS EVEN COLDER THAN GUIDANCE ACROSS
THE PINE BARRENS OF LI. A FEW SINGLE DIGIT LOWS WILL BE POSSIBLE IN
THIS AREA. TEMPS BLW GUIDANCE IN THE CITY AS WELL...AS TEMPS AT
20Z WERE CLOSE TO GUIDANCE LOWS AND A FEW DEGREES SHOULD BE LOST
AFT DARK. SOME WARMING LATE IS POSSIBLE IN THE CITY AND WRN LI AS
LIGHT SW FLOW DEVELOPS ON THE BACK SIDE OF THE HIGH.
LOW PRES OVER ONTARIO WILL RACE EWD ON MON UNDER THE INFLUENCE OF A
STRENGTHENING 120KT H3 JET. AS THE ASSOCIATED COLD FRONT
APPROACHES...THE PRES GRAD WILL TIGHTEN...ALLOWING FOR INCREASING
WSW WINDS DURING THE DAY. SUSTAINED WINDS WILL MAX OUT IN THE
15-20KT RANGE WITH SOME GUSTS TO AROUND 30KT. STRONGEST WINDS WILL
BE ALONG THE S SHORES. 12Z OKX SOUNDING INDICATED 0.14 INCHES OF
PW...SO THE FCST WILL BE KEPT DRY DURING THE DAYTIME HOURS WITH
MOISTURE TRANSPORT VECTORS NOT REACHING THE CWA TIL AROUND 00Z TUE.
TEMPS WARMER THAN SUN DUE TO BETTER MIXING ALL AREAS AND AN ONSHORE
COMPONENT ON THE COASTS.
THE COLD FRONT PASSES MON NGT. 12Z MODELS IN GOOD AGREEMENT WITH
THIS. MOISTURE REMAINS EXTREMELY LIMITED...BUT ENOUGH LAKE MOISTURE
MAY ALLOW FOR A FEW SPRINKLES AND/OR FLURRIES. HAVE RETAINED THIS
WEATHER IN THE GRIDS. BL TOO WARM FOR FLAKES NEAR THE COASTS
INITIALLY...BUT AT THE CWA GETS INTO THE RR QUAD OF THE H3 170 PLUS
KT H3 JET AFT MIDNIGHT...A FEW FLURRIES POSSIBLE POST FRONTAL ACROSS
ALL AREAS. MOS WAS IN GOOD AGREEMENT FOR TEMPS...SO A BLEND WAS
USED.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
THE GFS IS MORE PROGRESSIVE THAN THE NAM/ECMWF/SREF WITH THE SYSTEM
IMPACTING THE REGION MID WEEK...AS IS ITS BIAS...SO USED A BLEND OF
THE SLOWER SOLUTIONS TUESDAY THROUGH WEDNESDAY. WEDNESDAY NIGHT
THROUGH CHRISTMAS DAY...THERE ARE QUITE A BIT OF DIFFERENCES BETWEEN
THE GFS AND ECMWF IN HOW THEY HANDLE THE NEXT SYSTEM EJECTING FROM
THE SW U.S. AND ITS INTERACTION WITH THE NORTHERN STREAM. DUE TO
BETTER RUN TO RUN CONSISTENCY AND BETTER OVERALL VERIFICATION IN THE
LONG TERM...LEANED HEAVILY TOWARDS THE ECMWF WEDNESDAY NIGHT THROUGH
SUNDAY.
RIDGING BUILDS INTO THE AREA TUESDAY/TUESDAY NIGHT...THEN SLIDES
OFFSHORE WEDNESDAY AS A SOUTHERN STREAM TROUGH LIFTS INTO THE UPPER
OHIO RIVER VALLEY...THIS TROUGH WILL SUPPORT A SURFACE LOW TRACKING
TO OUR NORTH WEDNESDAY.
TUESDAY SHOULD BE DRY UNDERNEATH THE RIDGE BUILDING IN. OVER RUNNING
SETS UP TUESDAY NIGHT...AHEAD OF A SURFACE AND 850 HPA WARM
FRONT...EXPECT LIGHT PRECIPITATION TO GRADUALLY DEVELOP FROM SW TO
NE FROM TUESDAY NIGHT INTO WEDNESDAY MORNING. LOW LEVEL THERMAL
PROFILES SUPPORT RAIN ACROSS NYC METRO/LONG ISLAND WITH A WINTRY
MIX...INCLUDING POSSIBLY SOME FREEZING RAIN ACROSS THE
INTERIOR...BEFORE CHANGING TO ALL RAIN AS THE WARM FRONT LIFTS TO
THE NORTH WEDNESDAY MORNING. 40-50 KT LOW LEVEL JET MOVES IN BY
WEDNESDAY AFTERNOON SUPPORTING MORE WIDESPREAD RAIN.
THE AFOREMENTIONED TROUGH LIFT JUST OVER THE REGION WEDNESDAY
NIGHT...ALLOWING PRECIPITATION TO TAPER OFF FROM W TO E BY THURSDAY
MORNING - STILL CARRY SLIGHT CHANCE POPS THURSDAY MORNING AS THERE
HAS BEEN SOME UNCERTAINTY IN TIMING OF THE SYSTEM...WITH SOME
SUGGESTIONS IT COULD END UP A TAD SLOWER THAN CURRENTLY FORECAST.
RIDGING BUILDS IN THURSDAY WITH ITS AXIS SLIDING OFFSHORE THURSDAY
NIGHT. FOLLOWING THE ECMWF...IT APPEARS THAT THE SHEARING TROUGH
FORECAST TO LIFT OUT OF BAJA CA WEDNESDAY...APPROACHES BY LATE
THURSDAY NIGHT...THEN CROSSES ON FRIDAY...WITH AN ASSOCIATED
COASTAL LOW PASSING TO THE SOUTH ALONG A STALLED FRONTAL BOUNDARY.
LOW LEVEL THERMAL PROFILES SUGGEST SNOW OR RAIN/SNOW ACROSS NORTHERN
ZONES AND RAIN ACROSS SOUTHERN ZONES BY LATE THURSDAY NIGHT...WITH
PRECIPITATION TRANSITIONING TO ALL RAIN DURING THE DAY ON FRIDAY ON
THE NORTHERN TIER. THERE IS QUITE A BIT OF UNCERTAINTY WITH THIS
SYSTEM...WITH SOME POTENTIAL IT COULD END UP MISSING US ENTIRELY TO
THE SOUTH.
FRIDAY NIGHT AND SATURDAY WILL FEATURE SW FLOW ALOFT...WITH SOME
EMBEDDED SHORTWAVES. THESE WARRANT SLIGHT CHANCE POPS FOR NOW...BUT
MORE THAN LIKELY WILL BE DRY.
THE NEXT POTENTIAL SYSTEM IMPACTS THE REGION LATE CHRISTMAS
EVE/CHRISTMAS DAY...THIS TIME EJECTING FROM NEAR THE FOUR CORNERS
REGION AROUND THURSDAY. LIKE THE SYSTEM FOR FRIDAY...THE SURFACE LOW
WILL TRACK TO THE SOUTH...THE QUESTION IS HOW FAR. FOLLOWING THE
ECMWF...HAVE SLIGHT CHANCE POPS FOR LIGHT SNOW DEVELOPING ACROSS
MOST ZONES LATE SATURDAY NIGHT...AND CONTINUING INTO SUNDAY
MORNING...THEN CHANGING TO RAIN IN THE AFTERNOON. ONCE AGAIN - LOW
CONFIDENCE AT THIS TIME.
NEAR NORMAL TEMPERATURES ARE EXPECTED TUESDAY...THEN ABOVE NORMAL
TEMPERATURES TUESDAY NIGHT THROUGH THURSDAY NIGHT. NEAR NORMAL
TEMPERATURES ARE FORECAST FRIDAY-SUNDAY.
&&
.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
VFR. HIGH PRESSURE REMAINS WEST OF THE AREA TERMINALS.
NORTH-NORTHWEST FLOW WITH SPEEDS OF 8 TO 12 KT WILL GRADUALLY
DIMINISH THIS EVENING TO LESS THAN 10 KT. EXPECT THE WIND DIRECTION
BETWEEN 320 TO 360.
SURFACE HIGH PRESSURE PASSES TO THE EAST TONIGHT WITH MOST TERMINALS
BECOMING LIGHT AND VARIABLE. AT THIS TIME...WINDS WILL GRADUALLY
SHIFT TO THE WEST AND EVENTUALLY THE SOUTHWEST. WIND SPEEDS INCREASE
THROUGHOUT MONDAY MORNING TO 8-12 KT WITH GUSTS INTO THE TEENS AND
LOWER 20S. SPEEDS MAY BE STRONGER AT THE NYC TERMINALS. CLOUD COVER
WILL INCREASE LATE IN THE 30 HOUR TAFS WITH THE APPROACH OF A COLD
FRONT...WITH VFR CIGS EXPECTED.
OUTLOOK FOR 18Z MONDAY THROUGH FRIDAY...
MONDAY AFTERNOON AND MONDAY NIGHT...VFR. STRONG SW FLOW WITH GUST
UP TO 25 KT POSSIBLE. BRIEF PERIOD OF GUSTY NW FLOW LATE AT NIGHT.
TUESDAY AND TUESDAY NIGHT...VFR...TRENDING TOWARD SUB VFR LATE AT
NIGHT.
WEDNESDAY...SUB VFR IN RAIN...BECOMING VFR AT NIGHT.
THURSDAY...VFR.
FRIDAY...SUB-VFR POSSIBLE.
&&
.MARINE...
LIGHT WINDS TNGT AS HIGH PRES BUILDS OVER THE WATERS. THE HIGH
DRIFTS E OF THE CSTL WATERS MON...ALLOWING FOR A TIGHTENING PRES
GRAD TO DEVELOP THRU THE DAY AS A COLD FRONT APPROACHES FROM THE W.
STRENGTHENING WSW WINDS WILL BE THE RESULT. SCA WILL REMAIN IN
EFFECT FOR ALL WATERS EXCEPT FOR THE ERN OCEAN...WHERE THE GALE
WATCH WILL BE RETAINED. WINDS WEAKEN INVOF THE FRONT
OVERNIGHT...THEN VEER TO THE NW BEHIND THE FRONT EARLY TUE MRNG.
SCA LEVEL SEAS COULD LINGER INTO TUESDAY ON THE FAR EASTERN COASTAL
WATERS...OTHERWISE SUB-SCA CONDITIONS ARE EXPECTED TUESDAY AND
TUESDAY NIGHT. SOUTHERLY FLOW AHEAD OF A STORM SYSTEM
WEDNESDAY...SHOULD AT LEAST BUILD SEAS ON THE COASTAL OCEAN WATERS
TO SCA LEVELS...WITH GUSTY WINDS CONTINUING THEM AT SCA LEVELS INTO
THURSDAY. THERE IS SOME POTENTIAL FOR SCA LEVEL GUSTS ON ALL WATERS
WEDNESDAY-THURSDAY...BUT NOT QUITE CONFIDENT ENOUGH TO GO WITH THIS
IN THE FORECAST AT THIS TIME.
FOR NOW GOING WITH SUB-SCA CONDITIONS ON FRIDAY WITH A COASTAL LOW
PASSING TO THE SOUTH...BUT THERE IS MUCH UNCERTAINTY IN THIS.
&&
.HYDROLOGY...
TRACE AMOUNTS OF PCPN ARE POSSIBLE MON NGT.
THERE IS THE POTENTIAL FOR AROUND A 1/4 TO 1/2 AN INCH OF LIQUID
EQUIVALENT TO FALL OVER THE REGION FROM TUESDAY NIGHT INTO WEDNESDAY
NIGHT. SOME OF THIS SHOULD FALL AS FROZEN PRECIPITATION ACROSS
MAINLY NORTHERN INTERIOR ZONES INTO WEDNESDAY MORNING. NO
SIGNIFICANT HYDROLOGIC IMPACT IS CURRENTLY EXPECTED.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM MONDAY TO 1 AM EST TUESDAY FOR
ANZ330-335-338-340-345-355.
GALE WATCH FROM MONDAY MORNING THROUGH LATE MONDAY NIGHT FOR
ANZ350-353.
&&
$$
SYNOPSIS...JMC/MALOIT
NEAR TERM...JMC
SHORT TERM...JMC
LONG TERM...MALOIT
AVIATION...BC
MARINE...JMC/MALOIT
HYDROLOGY...JMC/MALOIT
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
314 PM CST SUN DEC 18 2011
.DISCUSSION...
959 AM CST
THE DENSE FOG CONTINUES TO SLOWLY DISSIPATE...WITH MOST PREVAILING
VISIBILITIES AT OR ABOVE ONE MILE. THE EXCEPTION IS NORTHWEST
INDIANA WHERE THE FOG/STRATUS SPREAD IN THE LATEST. THE FOG
SHOULD CONTINUE TO ABATE WITH INCREASING LOW-LEVEL SOUTHWEST WINDS
EASING THE INVERSION IN THE LOWEST FEW HUNDRED FEET. IT IS
INTERESTING TO NOTE HOW THIS FOG CORRELATED WITH THE LIGHT BUT
FRESH SNOW COVER FROM THE SATURDAY MORNING EVENT. THIS SNOW COVER
MAKES IT TRICKY FOR TEMPERATURES THIS AFTERNOON...AS IT AIDED IN
COOLING LAST NIGHT /DOWN TO 10 DEGREES IN ROCHELLE/. IT HELPED THE
ASSOCIATED DEPTH OF THE INVERSION WITH RUC DIAGNOSTIC SOUNDINGS
INDICATING AN 8C DEGREE CLIMB JUST 100MB /3000 FT OR SO/ FROM THE
SURFACE OVER LOCATIONS IN THE NORTHERN HALF OF THE FORECAST AREA.
THE NORMAL DIURNAL CLIMB AT ORD AND RFD ARE 14 AND 15 DEGREES
RESPECTIVELY. WITH MORNING FOG/STRATUS AT AND AROUND BOTH
LOCATIONS...WOULD NOT THINK WE WOULD CLIMB MUCH ABOVE THAT GIVEN
THE INVERSION STRENGTH. IT WILL LIKELY CLIMB EVEN LESS IN CHICAGO
WHERE THE CLOUDS RESIDED LONGER. BELIEVE THE RUC AND MOST RECENT
NAM RUN AT 12Z HAVE A GOOD HANDLE ON KEEPING TEMPERATURES COOLER
IN THE NORTHERN FORECAST AREA. HAVE TRENDED THAT ROUTE...CUTTING 3
TO 5 DEGREES OFF OR SO.
MTF
//PREV DISCUSSION...
408 AM CST
HIGH PRESSURE CONTINUES TO BUILD INTO THE SOUTHEAST US THIS
MORNING. A STUBBORN STRATUS DECK THAT RESIDED OVER AREAS EAST OF
I-39 HAS FINALLY ERODED. HIGH CIRRUS CLOUDS ARE QUICKLY MOVING
SOUTHEAST INTO THE AREA...BUT IR IMAGERY INDICATES THE CLOUDS ARE
DISSIPATING AS THEY MOVE IN. EXPECTING CLEARING TO CONTINUE
THROUGH TODAY. WHILE MOST OF THE SNOWFALL FROM YESTERDAY HAS
ALREADY MELTED...THE CLEAR SKIES ARE ALLOWING TEMPS TO DROP
RAPIDLY. SOME LOCATIONS THAT HAVE SNOW ON THE GROUND MAY EVEN DIP
INTO THE TEENS BEFORE SUNRISE. AREAS OF FOG WILL CONTINUE TO
PERSIST AND BURN OFF AFTER SUNRISE. WITH PLENTY OF SUNSHINE
TOMORROW...TEMPS WILL RISE INTO THE LOW 40S TODAY.
CLOUDS BEGIN TO MOVE IN LATE TONIGHT AHEAD OF THE NEXT SYSTEM. IN
REGARDS TO THE NEXT SYSTEM...THE MODELS ARE BEGINNING TO SHOW A
SIMILAR SOLUTION AND FORECAST CONFIDENCE FOR THE TIMING OF THE
PRECIP IS MEDIUM. THE LOW MOVES FROM OKLAHOMA TUESDAY MORNING TO
DETROIT BY WEDNESDAY AFTERNOON. THIS PATH WOULD BRING A SWATH OF
PRECIPITATION INTO THE REGION. THE GFS WANTS TO PUSH THE PRECIP
FARTHER NORTH INTO CENTRAL WISCONSIN...WHILE THE ECMWF HAS THE
PRECIP ONLY REACHING SOUTHERN WISCONSIN. SINCE THE GFS SOLUTIONS
HAVE BEEN SLOWLY CONVERGING WITH THE STEADY ECMWF SOLUTION...WENT
AHEAD AND LIMITED THE NORTHERN EXTENT OF THE PRECIP. THAT BEING
SAID...CONFIDENCE IN THE FORECASTED PRECIP TYPE REMAINS LOW. LOOKING
AT MODEL SOUNDINGS...THE GFS WANTS TO WARM THE THERMAL PROFILE
TUESDAY...WHILE THE NAM WANTS TO COOL THE PROFILE. BOTH PROFILES
HAVE SURFACE TEMPS NEAR FREEZING.
PRECIP FROM THE LOW REACHES NORTHEASTERN IL AND NORTHWESTERN IN LATE
MONDAY INTO MONDAY NIGHT AS RAIN. THE RAIN WILL BEGIN SOUTH OF I-80
AND SLOWLY INCH NORTHWARD THROUGH TUESDAY. AREAS SOUTH OF I-80 WILL
LIKELY SEE ALL RAIN AS THEY WILL BE CLOSEST TO THE LOW ITSELF. A
RAIN/SNOW MIX WILL FALL NORTH OF I-80 ON TUESDAY. SINCE THIS LOW IS
COMING OUT OF THE SOUTH CENTRAL US...THERE IS NO GOOD COLD AIR PUSH
ASSOCIATED WITH IT. THEREFORE...AS THE LOW PULLS AWAY TUESDAY NIGHT
AND WEDNESDAY...LINGERING PRECIP WILL FALL AS A RAIN/SNOW MIX OR AS
A COLD RAIN. DAYTIME HIGH TEMPS TUESDAY THROUGH THURSDAY WILL BE IN
THE MID 30S TO LOW 40S. LOW TEMPS WILL BE IN THE UPPER 20S TO LOW
30S.
NUMEROUS UPPER LEVEL ENERGY STREAMERS PASS THROUGH THE REGION
THURSDAY AND FRIDAY...RESULTING IN SLIGHT CHANCES OF SNOW. NONE OF
THESE CHANCES LOOK LIKE THEY WILL PRODUCE SIGNIFICANT SNOWFALL.
HIGH PRESSURE MOVES IN FROM THE PLAINS ON FRIDAY.
JEE
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 21Z...
* MARGINALLY GUSTY SSW TO SW REST OF AFTERNOON.
* TIMING OF PASSAGE LOCALLY OF COLD FRONT TRAILING SW FROM LOW
PRES MOVING ACROSS ONTARIO OVERNIGHT.
* PERIOD OF MVFR CEILINGS POSSIBLE MON MORNING FOLLOWING CFP.
TRS
//DISCUSSION...UPDATED 18Z...
SUN AND INCREASING WINDS DID HEIR JOBS IN MIXING OUT THE STRATUS
AND FOG STUCK UNDER THE VERY SHALLOW INVERSION. REST OF THE DAY
AND MUCH OF TONIGHT WILL ONLY SEE PERIODIC AREAS OF CIRRUS CROSSING
OVERHEAD AS THEY TOP THE BROAD UPPER RIDGE CENTERED OVER THE
PLAINS.
A SHORT WAVE CROSSING THE SOUTHERN CANADIAN ROCKIES LATE THIS
MORNING WILL CONTINUE EAST-SOUTHEAST AND CROSS ONTARIO OVERNIGHT.
A COLD FRONT TRAILING BACK TO THE SOUTHWEST ACROSS THE UPPER
MIDWEST AND THE CENTRAL PLAINS WILL BE MOVING EAST...AND IS
EXPECTED TO CROSS NORTHERN IL AND AND NORTHWEST IND DURING THE
PERIOD FROM 12Z TO 18Z MON.
A THICK LAYER OF MID LEVEL DRY AIR IS PROGGED ACROSS THE LOCAL
AREA DURING THE TIME OF THE PASSAGE OF TAIL OF THE ONTARIO SHORT
WAVE TROUGH AND THE COLD FRONT CROSSING THE LOCAL AREA SO NO
PRECIPITATION OUTSIDE OF A FEW FLURRIES EXPECTED.
FORECAST PROFILES DO SHOW A LAYER OF MOIST LOWER LEVEL AIR
TRAPPED UNDER AN INVERSION FOLLOWING THE COLD FRONTAL PASSAGE WITH
THE BASE OF THE INVERSION LOWERING TO AROUND 022 SO HAVE A PERIOD
OF MVFR CEILINGS IN THE TAFORS FOLLOWING THE COLD FRONT AND THE
ASSOCIATED WIND SHIFT FROM SOUTHWEST TO WEST AND WEST-NORTHWEST.
AS HIGH PRESSURE BUILDS IN FROM SOUTH CENTRAL CANADA AND THE
NORTHERN PLAINS ANTICYCLONIC LOW LEVEL FLOW INCREASES AND SHOULD
SERVE TO BREAK UP AND LIFT THE STRATOCUMULUS DECK.
ANOTHER SHORT WAVE DROPS SOUTHEAST OVER THE NORTHERN HIGH PLAINS
MONDAY MORNING AND THEN TURNS EASTWARD AND CROSSES THE DAKOTAS
DURING THE AFTERNOON BEFORE CROSSING THE UPPER MIDWEST AND WESTERN
GREAT LAKES DURING MIDDAY NIGHT. THIS SHORT WAVE WILL BE PASSING
OVER A LARGE DRY SURFACE HIGH ACROSS THE REGION SO ONLY EVIDENCE
SUSPECTED WILL BE AND INCREASE IN MID LEVEL CLOUDS LATER MONDAY
AND MONDAY NIGHT.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* HIGH CONFIDENCE IN VFR REST OF THIS AFTERNOON AND TONIGHT.
* HIGH CONFIDENCE IN WIND FORECASTS.
* MEDIUM CONFIDENCE IN COLD FRONTAL PASSAGE MONDAY MORNING AND
EXTEND OF MVFR CEILINGS IN WAKE OF THIS FRONT.
TRS
//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...
MONDAY NIGHT...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF
ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN AND SNOW. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
SATURDAY...VFR.
MDB
&&
.MARINE...
305 PM
LOW PRESSURE WILL BE DEEPENING AS IT MOVES EAST ACROSS ONTARIO
TONIGHT. THE DEEPENING OF THE LOW AND THE APPROACH OF THE
SOUTHWESTWARD TRAILING COLD FRONT IS INCREASING THE PRESSURE
GRADIENT ACROSS THE WESTERN GREAT LAKES AND EXPECT WINDS TO REACH
GALE FORCE ON THE NORTH HALF BY LATE AFTERNOON AND ON THE SOUTH
HALF DURING THE EVENING.
AS THE COLD FRONT APPROACHES LATE TONIGHT THE GRADIENT AND
RESULTANT WINDS WILL DIMINISH. WIND DIRECTIONS VEER TO W...NW
AND EVENTUALLY N DURING THE DAY AS HIGH PRESSURE BUILDS OVER THE
PLAINS BEHIND THE COLD FRONT. THIS HIGH THEN SPREADS EAST ACROSS
THE UPPER MIDWEST AND THE UPPER GREAT LAKES....WITH THE HIGH BEING
CENTERED OVER THE GREAT LAKES BY TUESDAY MORNING.
DURING THE DAY TUESDAY LOW PRESSURE WILL BE MOVING NORTHEASTWARD
FROM THE SOUTHERN PLAINS...REACHING THE MID MISSISSIPPI VALLEY BY
TUESDAY NIGHT. THE LOW THEN MOVES EAST ACROSS THE MIDWEST TO THE
UPPER OHIO RIVER VALLEY BY WEDNESDAY EVENING.
ANTHER COLD FRONT WILL MOVE FROM THE UPPER MIDWEST ACROSS LAKE
MICHIGAN DURING WEDNESDAY NIGHT AND THURSDAY MORNING....WITH
ANOTHER LARGE AREA OF HIGH PRESSURE SETTLING OVER THE CENTRAL
PLAINS THURSDAY NIGHT...AND SPREADING EAST ACROSS THE MIDWEST
FRIDAY AND FRIDAY NIGHT.
TRS
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868 UNTIL 5 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 5 AM MONDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 8 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1253 PM CST SUN DEC 18 2011
.DISCUSSION...
959 AM CST
THE DENSE FOG CONTINUES TO SLOWLY DISSIPATE...WITH MOST PREVAILING
VISIBILITIES AT OR ABOVE ONE MILE. THE EXCEPTION IS NORTHWEST
INDIANA WHERE THE FOG/STRATUS SPREAD IN THE LATEST. THE FOG
SHOULD CONTINUE TO ABATE WITH INCREASING LOW-LEVEL SOUTHWEST WINDS
EASING THE INVERSION IN THE LOWEST FEW HUNDRED FEET. IT IS
INTERESTING TO NOTE HOW THIS FOG CORRELATED WITH THE LIGHT BUT
FRESH SNOW COVER FROM THE SATURDAY MORNING EVENT. THIS SNOW COVER
MAKES IT TRICKY FOR TEMPERATURES THIS AFTERNOON...AS IT AIDED IN
COOLING LAST NIGHT /DOWN TO 10 DEGREES IN ROCHELLE/. IT HELPED THE
ASSOCIATED DEPTH OF THE INVERSION WITH RUC DIAGNOSTIC SOUNDINGS
INDICATING AN 8C DEGREE CLIMB JUST 100MB /3000 FT OR SO/ FROM THE
SURFACE OVER LOCATIONS IN THE NORTHERN HALF OF THE FORECAST AREA.
THE NORMAL DIURNAL CLIMB AT ORD AND RFD ARE 14 AND 15 DEGREES
RESPECTIVELY. WITH MORNING FOG/STRATUS AT AND AROUND BOTH
LOCATIONS...WOULD NOT THINK WE WOULD CLIMB MUCH ABOVE THAT GIVEN
THE INVERSION STRENGTH. IT WILL LIKELY CLIMB EVEN LESS IN CHICAGO
WHERE THE CLOUDS RESIDED LONGER. BELIEVE THE RUC AND MOST RECENT
NAM RUN AT 12Z HAVE A GOOD HANDLE ON KEEPING TEMPERATURES COOLER
IN THE NORTHERN FORECAST AREA. HAVE TRENDED THAT ROUTE...CUTTING 3
TO 5 DEGREES OFF OR SO.
MTF
//PREV DISCUSSION...
408 AM CST
HIGH PRESSURE CONTINUES TO BUILD INTO THE SOUTHEAST US THIS
MORNING. A STUBBORN STRATUS DECK THAT RESIDED OVER AREAS EAST OF
I-39 HAS FINALLY ERODED. HIGH CIRRUS CLOUDS ARE QUICKLY MOVING
SOUTHEAST INTO THE AREA...BUT IR IMAGERY INDICATES THE CLOUDS ARE
DISSIPATING AS THEY MOVE IN. EXPECTING CLEARING TO CONTINUE
THROUGH TODAY. WHILE MOST OF THE SNOWFALL FROM YESTERDAY HAS
ALREADY MELTED...THE CLEAR SKIES ARE ALLOWING TEMPS TO DROP
RAPIDLY. SOME LOCATIONS THAT HAVE SNOW ON THE GROUND MAY EVEN DIP
INTO THE TEENS BEFORE SUNRISE. AREAS OF FOG WILL CONTINUE TO
PERSIST AND BURN OFF AFTER SUNRISE. WITH PLENTY OF SUNSHINE
TOMORROW...TEMPS WILL RISE INTO THE LOW 40S TODAY.
CLOUDS BEGIN TO MOVE IN LATE TONIGHT AHEAD OF THE NEXT SYSTEM. IN
REGARDS TO THE NEXT SYSTEM...THE MODELS ARE BEGINNING TO SHOW A
SIMILAR SOLUTION AND FORECAST CONFIDENCE FOR THE TIMING OF THE
PRECIP IS MEDIUM. THE LOW MOVES FROM OKLAHOMA TUESDAY MORNING TO
DETROIT BY WEDNESDAY AFTERNOON. THIS PATH WOULD BRING A SWATH OF
PRECIPITATION INTO THE REGION. THE GFS WANTS TO PUSH THE PRECIP
FARTHER NORTH INTO CENTRAL WISCONSIN...WHILE THE ECMWF HAS THE
PRECIP ONLY REACHING SOUTHERN WISCONSIN. SINCE THE GFS SOLUTIONS
HAVE BEEN SLOWLY CONVERGING WITH THE STEADY ECMWF SOLUTION...WENT
AHEAD AND LIMITED THE NORTHERN EXTENT OF THE PRECIP. THAT BEING
SAID...CONFIDENCE IN THE FORECASTED PRECIP TYPE REMAINS LOW. LOOKING
AT MODEL SOUNDINGS...THE GFS WANTS TO WARM THE THERMAL PROFILE
TUESDAY...WHILE THE NAM WANTS TO COOL THE PROFILE. BOTH PROFILES
HAVE SURFACE TEMPS NEAR FREEZING.
PRECIP FROM THE LOW REACHES NORTHEASTERN IL AND NORTHWESTERN IN LATE
MONDAY INTO MONDAY NIGHT AS RAIN. THE RAIN WILL BEGIN SOUTH OF I-80
AND SLOWLY INCH NORTHWARD THROUGH TUESDAY. AREAS SOUTH OF I-80 WILL
LIKELY SEE ALL RAIN AS THEY WILL BE CLOSEST TO THE LOW ITSELF. A
RAIN/SNOW MIX WILL FALL NORTH OF I-80 ON TUESDAY. SINCE THIS LOW IS
COMING OUT OF THE SOUTH CENTRAL US...THERE IS NO GOOD COLD AIR PUSH
ASSOCIATED WITH IT. THEREFORE...AS THE LOW PULLS AWAY TUESDAY NIGHT
AND WEDNESDAY...LINGERING PRECIP WILL FALL AS A RAIN/SNOW MIX OR AS
A COLD RAIN. DAYTIME HIGH TEMPS TUESDAY THROUGH THURSDAY WILL BE IN
THE MID 30S TO LOW 40S. LOW TEMPS WILL BE IN THE UPPER 20S TO LOW
30S.
NUMEROUS UPPER LEVEL ENERGY STREAMERS PASS THROUGH THE REGION
THURSDAY AND FRIDAY...RESULTING IN SLIGHT CHANCES OF SNOW. NONE OF
THESE CHANCES LOOK LIKE THEY WILL PRODUCE SIGNIFICANT SNOWFALL.
HIGH PRESSURE MOVES IN FROM THE PLAINS ON FRIDAY.
JEE
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* SSW TO SW WINDS GRADUALLY BECOMING A BIT GUSTY THIS AFTERNOON.
* TIMING OF PASSAGE LOCALLY OF COLD FRONT TRAILING SW FROM LOW
PRES MOVING ACROSS ONTARIO OVERNIGHT.
* PERIOD OF MVFR CEILINGS POSSIBLE MON MORNING FOLLOWING CFP.
TRS
//DISCUSSION...UPDATED 18Z...
SUN AND INCREASING WINDS DID HEIR JOBS IN MIXING OUT THE STRATUS
AND FOG STUCK UNDER THE VERY SHALLOW INVERSION. REST OF THE DAY
AND MUCH OF TONIGHT WILL ONLY SEE PERIODIC AREAS OF CIRRUS CROSSING
OVERHEAD AS THEY TOP THE BROAD UPPER RIDGE CENTERED OVER THE
PLAINS.
A SHORT WAVE CROSSING THE SOUTHERN CANADIAN ROCKIES LATE THIS
MORNING WILL CONTINUE EAST-SOUTHEAST AND CROSS ONTARIO OVERNIGHT.
A COLD FRONT TRAILING BACK TO THE SOUTHWEST ACROSS THE UPPER
MIDWEST AND THE CENTRAL PLAINS WILL BE MOVING EAST...AND IS
EXPECTED TO CROSS NORTHERN IL AND AND NORTHWEST IND DURING THE
PERIOD FROM 12Z TO 18Z MON.
A THICK LAYER OF MID LEVEL DRY AIR IS PROGGED ACROSS THE LOCAL
AREA DURING THE TIME OF THE PASSAGE OF TAIL OF THE ONTARIO SHORT
WAVE TROUGH AND THE COLD FRONT CROSSING THE LOCAL AREA SO NO
PRECIPITATION OUTSIDE OF A FEW FLURRIES EXPECTED.
FORECAST PROFILES DO SHOW A LAYER OF MOIST LOWER LEVEL AIR
TRAPPED UNDER AN INVERSION FOLLOWING THE COLD FRONTAL PASSAGE WITH
THE BASE OF THE INVERSION LOWERING TO AROUND 022 SO HAVE A PERIOD
OF MVFR CEILINGS IN THE TAFORS FOLLOWING THE COLD FRONT AND THE
ASSOCIATED WIND SHIFT FROM SOUTHWEST TO WEST AND WEST-NORTHWEST.
AS HIGH PRESSURE BUILDS IN FROM SOUTH CENTRAL CANADA AND THE
NORTHERN PLAINS ANTICYCLONIC LOW LEVEL FLOW INCREASES AND SHOULD
SERVE TO BREAK UP AND LIFT THE STRATOCUMULUS DECK.
ANOTHER SHORT WAVE DROPS SOUTHEAST OVER THE NORTHERN HIGH PLAINS
MONDAY MORNING AND THEN TURNS EASTWARD AND CROSSES THE DAKOTAS
DURING THE AFTERNOON BEFORE CROSSING THE UPPER MIDWEST AND WESTERN
GREAT LAKES DURING MIDDAY NIGHT. THIS SHORT WAVE WILL BE PASSING
OVER A LARGE DRY SURFACE HIGH ACROSS THE REGION SO ONLY EVIDENCE
SUSPECTED WILL BE AND INCREASE IN MID LEVEL CLOUDS LATER MONDAY
AND MONDAY NIGHT.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE IN VFR REST OF TODAY AND TONIGHT.
* HIGH CONFIDENCE IN WIND FORECASTS.
* MEDIUM CONFIDENCE IN COLD FRONTAL PASSAGE MONDAY MORNING AND
EXTEND OF MVFR CEILINGS IN WAKE OF THIS FRONT.
TRS
//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...
MONDAY NIGHT...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF
ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN AND SNOW. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
SATURDAY...VFR.
MDB
&&
.MARINE...
315 AM CST
...SOUTHWEST GALES DEVELOP THIS AFTERNOON...
A SERIES OF RIDGES AND TROUGHS DOT THE EARLY MORNING WEATHER MAP.
HIGH PRESSURE EXTENDS FROM EASTERN QUEBEC INTO NORTHERN NEW ENGLAND
AND IS WORKING TOWARDS THE ATLANTIC WHILE LOW PRESSURE OVER HUDSON
BAY MOVES EASTWARD DRAGGING A TROUGH ACROSS LAKE HURON AND SOUTHERN
ONTARIO. WEAK RIDGING IS POSITIONED TO THE WEST OF THE TROUGH AND
WILL CREST OVER LAKE MICHIGAN THIS MORNING. THE MOST NOTABLE FEATURE
IS LOW PRESSURE MOVING FROM CENTRAL SASKATCHEWAN INTO CENTRAL
MANITOBA. THIS LOW WILL DEEPEN AS IT MOVES EAST TODAY TIGHTENING THE
PRESSURE GRADIENT ACROSS THE UPPER LAKES THIS AFTERNOON. THE LOW WILL
DRAG A TROUGH ACROSS THE LAKE EARLY MONDAY MORNING WHICH WILL SHIFT
WINDS TO NORTHWESTERLY. IN TERMS OF TRENDS...WINDS WILL BEGIN TO
SLACKEN SOMEWHAT THIS MORNING AS THE RIDGE MOVES ACROSS BUT THEN
QUICKLY PICK UP FROM THE SOUTHWEST THIS AFTERNOON AS THE DEEPENING
LOW MOVES INTO WESTERN ONTARIO AND JUST NORTH OF LAKE SUPERIOR BY
EVENING. AM EXPECTING SPEEDS TO REACH GALE FORCE TO 40 KT BY LATE
AFTERNOON NORTH AND CONTINUE THROUGH THE EVENING THEN SLOWLY BEGIN
TO DIMINISH TO 35 KT GALES AFTER MIDNIGHT WITH A REDUCTION TO
BELOW GALE TOWARD DAYBREAK. STRONGEST SPEEDS WILL BE ACROSS THE
NORTHERN HALF TO TWO-THIRDS OF THE LAKE WITH SPEEDS A FEW KNOTS
LOWER AND SLIGHTLY SLOWER IN ARRIVING ACROSS THE SOUTH. SPEEDS
WILL LIKELY REMAIN IN THE 20 TO 25 KT RANGE FOR MOST OF MONDAY AS
THE PRESSURE GRADIENT REMAINS STRONG BETWEEN THE DEPARTING LOW AND
A STRONG HIGH THAT WILL BE MOVING IN FROM THE WEST. WINDS WILL
TURN TO THE NORTH BY AFTERNOON THEN PROBABLY TURN MORE NORTHEAST
AS SPEEDS DROP OFF MONDAY EVENING AS THE HIGH REACHES THE LAKE.
LOW PRESSURE WILL DEVELOP ACROSS NORTHERN TEXAS MONDAY NIGHT AND
LIFT NORTHEASTWARD INTO EAST-CENTRAL ILLINOIS TUESDAY NIGHT WHILE
ANOTHER LOW MOVES ACROSS HUDSON BAY. RIDGING WILL REMAIN ACROSS THE
LAKE BUT THE NORTHERN SYSTEM LOOKS TO PASS CLOSE ENOUGH TO BRING
INCREASING SOUTH TO SOUTHWEST WINDS ACROSS THE FAR NORTHERN PART OF
THE LAKE TUESDAY AFTERNOON. THE GRADIENT WILL REMAIN WEAKER SOUTH
BUT A MORE SOUTHEASTERLY WIND DIRECTION SHOULD PREVAIL AHEAD OF THE
APPROACHING LOW. THE LOW WILL LIKELY PASS JUST TO THE SOUTHEAST OF
THE LAKE WEDNESDAY ALLOWING WINDS TO TURN NORTH OR NORTHEAST BEFORE
TURNING NORTHWEST WEDNESDAY EVENING. THE PATTERN REMAINS ACTIVE FROM
THAT POINT ONWARD WITH A SERIES OF HIGHS AND LOWS BRINGING UPS AND
DOWNS TO THE WIND SPEED FORECAST INTO NEXT WEEKEND.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868 UNTIL 6 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM SUNDAY TO 6 AM
MONDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM SUNDAY TO 9 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
NWS CHICAGO/ROMEOVILLE IL
1000 AM CST SUN DEC 18 2011
.DISCUSSION...
959 AM CST
THE DENSE FOG CONTINUES TO SLOWLY DISSIPATE...WITH MOST PREVAILING
VISIBILITIES AT OR ABOVE ONE MILE. THE EXCEPTION IS NORTHWEST
INDIANA WHERE THE FOG/STRATUS SPREAD IN THE LATEST. THE FOG
SHOULD CONTINUE TO ABATE WITH INCREASING LOW-LEVEL SOUTHWEST WINDS
EASING THE INVERSION IN THE LOWEST FEW HUNDRED FEET. IT IS
INTERESTING TO NOTE HOW THIS FOG CORRELATED WITH THE LIGHT BUT
FRESH SNOW COVER FROM THE SATURDAY MORNING EVENT. THIS SNOW COVER
MAKES IT TRICKY FOR TEMPERATURES THIS AFTERNOON...AS IT AIDED IN
COOLING LAST NIGHT /DOWN TO 10 DEGREES IN ROCHELLE/. IT HELPED THE
ASSOCIATED DEPTH OF THE INVERSION WITH RUC DIAGNOSTIC SOUNDINGS
INDICATING AN 8C DEGREE CLIMB JUST 100MB /3000 FT OR SO/ FROM THE
SURFACE OVER LOCATIONS IN THE NORTHERN HALF OF THE FORECAST AREA.
THE NORMAL DIURNAL CLIMB AT ORD AND RFD ARE 14 AND 15 DEGREES
RESPECTIVELY. WITH MORNING FOG/STRATUS AT AND AROUND BOTH
LOCATIONS...WOULD NOT THINK WE WOULD CLIMB MUCH ABOVE THAT GIVEN
THE INVERSION STRENGTH. IT WILL LIKELY CLIMB EVEN LESS IN CHICAGO
WHERE THE CLOUDS RESIDED LONGER. BELIEVE THE RUC AND MOST RECENT
NAM RUN AT 12Z HAVE A GOOD HANDLE ON KEEPING TEMPERATURES COOLER
IN THE NORTHERN FORECAST AREA. HAVE TRENDED THAT ROUTE...CUTTING 3
TO 5 DEGREES OFF OR SO.
MTF
&&
.PREV DISCUSSION...
408 AM CST
HIGH PRESSURE CONTINUES TO BUILD INTO THE SOUTHEAST US THIS
MORNING. A STUBBORN STRATUS DECK THAT RESIDED OVER AREAS EAST OF
I-39 HAS FINALLY ERODED. HIGH CIRRUS CLOUDS ARE QUICKLY MOVING
SOUTHEAST INTO THE AREA...BUT IR IMAGERY INDICATES THE CLOUDS ARE
DISSIPATING AS THEY MOVE IN. EXPECTING CLEARING TO CONTINUE
THROUGH TODAY. WHILE MOST OF THE SNOWFALL FROM YESTERDAY HAS
ALREADY MELTED...THE CLEAR SKIES ARE ALLOWING TEMPS TO DROP
RAPIDLY. SOME LOCATIONS THAT HAVE SNOW ON THE GROUND MAY EVEN DIP
INTO THE TEENS BEFORE SUNRISE. AREAS OF FOG WILL CONTINUE TO
PERSIST AND BURN OFF AFTER SUNRISE. WITH PLENTY OF SUNSHINE
TOMORROW...TEMPS WILL RISE INTO THE LOW 40S TODAY.
CLOUDS BEGIN TO MOVE IN LATE TONIGHT AHEAD OF THE NEXT SYSTEM. IN
REGARDS TO THE NEXT SYSTEM...THE MODELS ARE BEGINNING TO SHOW A
SIMILAR SOLUTION AND FORECAST CONFIDENCE FOR THE TIMING OF THE
PRECIP IS MEDIUM. THE LOW MOVES FROM OKLAHOMA TUESDAY MORNING TO
DETROIT BY WEDNESDAY AFTERNOON. THIS PATH WOULD BRING A SWATH OF
PRECIPITATION INTO THE REGION. THE GFS WANTS TO PUSH THE PRECIP
FARTHER NORTH INTO CENTRAL WISCONSIN...WHILE THE ECMWF HAS THE
PRECIP ONLY REACHING SOUTHERN WISCONSIN. SINCE THE GFS SOLUTIONS
HAVE BEEN SLOWLY CONVERGING WITH THE STEADY ECMWF SOLUTION...WENT
AHEAD AND LIMITED THE NORTHERN EXTENT OF THE PRECIP. THAT BEING
SAID...CONFIDENCE IN THE FORECASTED PRECIP TYPE REMAINS LOW. LOOKING
AT MODEL SOUNDINGS...THE GFS WANTS TO WARM THE THERMAL PROFILE
TUESDAY...WHILE THE NAM WANTS TO COOL THE PROFILE. BOTH PROFILES
HAVE SURFACE TEMPS NEAR FREEZING.
PRECIP FROM THE LOW REACHES NORTHEASTERN IL AND NORTHWESTERN IN LATE
MONDAY INTO MONDAY NIGHT AS RAIN. THE RAIN WILL BEGIN SOUTH OF I-80
AND SLOWLY INCH NORTHWARD THROUGH TUESDAY. AREAS SOUTH OF I-80 WILL
LIKELY SEE ALL RAIN AS THEY WILL BE CLOSEST TO THE LOW ITSELF. A
RAIN/SNOW MIX WILL FALL NORTH OF I-80 ON TUESDAY. SINCE THIS LOW IS
COMING OUT OF THE SOUTH CENTRAL US...THERE IS NO GOOD COLD AIR PUSH
ASSOCIATED WITH IT. THEREFORE...AS THE LOW PULLS AWAY TUESDAY NIGHT
AND WEDNESDAY...LINGERING PRECIP WILL FALL AS A RAIN/SNOW MIX OR AS
A COLD RAIN. DAYTIME HIGH TEMPS TUESDAY THROUGH THURSDAY WILL BE IN
THE MID 30S TO LOW 40S. LOW TEMPS WILL BE IN THE UPPER 20S TO LOW
30S.
NUMEROUS UPPER LEVEL ENERGY STREAMERS PASS THROUGH THE REGION
THURSDAY AND FRIDAY...RESULTING IN SLIGHT CHANCES OF SNOW. NONE OF
THESE CHANCES LOOK LIKE THEY WILL PRODUCE SIGNIFICANT SNOWFALL.
HIGH PRESSURE MOVES IN FROM THE PLAINS ON FRIDAY.
JEE
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 15Z...
* BAND OF IFR/LIFR STRATUS AND FOG STILL OVER LOCAL TERMINALS AT
MID MORNING.
* TIMING OF IMPROVEMENT TO VFR TODAY.
* INCREASING SSW TO SW WINDS TO MODERATE SPEEDS OF 15-20 KT THIS
AFTERNOON.
* MVFR CEILINGS POSSIBLE MONDAY MORNING AS A TROUGH CROSSES THE AREA.
TRS
//DISCUSSION...UPDATED 15Z...
HAVE DELAYED IMPROVEMENT OF FLIGHT CATEGORIES BACK UP TO VFR A
COUPLE HOURS BUT ALL SHOULD BE VFR BY 18Z. RISING OF SUN AND WEAK
SURFACE HEATING ALONG WITH GRADUALLY INCREASING SSW-SW WINDS
HELPING TO MIX OUT THE STRATUS AND FOG THIS MORNING BUT THE STREAK
OF CIRRUS THAT PASSED RIGHT OVER THE LOW DECK PROBABLY DELAYED
THE QUICKER IMPROVEMENT THAT WAS ANTICIPATED EARLIER THIS MORNING.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 15Z...
* MEDIUM TO HIGH CONFIDENCE LIFR AND IFR VISIBILITIES AND CEILINGS
WILL QUICKLY IMPROVE TO VFR BY 18Z.
* HIGH CONFIDENCE IN WIND FORECASTS.
* MEDIUM CONFIDENCE IN MVFR CEILINGS SOMETIME MONDAY MORNING.
MDB/TRS
//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...
MONDAY NIGHT...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF
ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN AND SNOW. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
SATURDAY...VFR.
MDB
&&
.MARINE...
315 AM CST
...SOUTHWEST GALES DEVELOP THIS AFTERNOON...
A SERIES OF RIDGES AND TROUGHS DOT THE EARLY MORNING WEATHER MAP.
HIGH PRESSURE EXTENDS FROM EASTERN QUEBEC INTO NORTHERN NEW ENGLAND
AND IS WORKING TOWARDS THE ATLANTIC WHILE LOW PRESSURE OVER HUDSON
BAY MOVES EASTWARD DRAGGING A TROUGH ACROSS LAKE HURON AND SOUTHERN
ONTARIO. WEAK RIDGING IS POSITIONED TO THE WEST OF THE TROUGH AND
WILL CREST OVER LAKE MICHIGAN THIS MORNING. THE MOST NOTABLE FEATURE
IS LOW PRESSURE MOVING FROM CENTRAL SASKATCHEWAN INTO CENTRAL
MANITOBA. THIS LOW WILL DEEPEN AS IT MOVES EAST TODAY TIGHTENING THE
PRESSURE GRADIENT ACROSS THE UPPER LAKES THIS AFTERNOON. THE LOW WILL
DRAG A TROUGH ACROSS THE LAKE EARLY MONDAY MORNING WHICH WILL SHIFT
WINDS TO NORTHWESTERLY. IN TERMS OF TRENDS...WINDS WILL BEGIN TO
SLACKEN SOMEWHAT THIS MORNING AS THE RIDGE MOVES ACROSS BUT THEN
QUICKLY PICK UP FROM THE SOUTHWEST THIS AFTERNOON AS THE DEEPENING
LOW MOVES INTO WESTERN ONTARIO AND JUST NORTH OF LAKE SUPERIOR BY
EVENING. AM EXPECTING SPEEDS TO REACH GALE FORCE TO 40 KT BY LATE
AFTERNOON NORTH AND CONTINUE THROUGH THE EVENING THEN SLOWLY BEGIN
TO DIMINISH TO 35 KT GALES AFTER MIDNIGHT WITH A REDUCTION TO
BELOW GALE TOWARD DAYBREAK. STRONGEST SPEEDS WILL BE ACROSS THE
NORTHERN HALF TO TWO-THIRDS OF THE LAKE WITH SPEEDS A FEW KNOTS
LOWER AND SLIGHTLY SLOWER IN ARRIVING ACROSS THE SOUTH. SPEEDS
WILL LIKELY REMAIN IN THE 20 TO 25 KT RANGE FOR MOST OF MONDAY AS
THE PRESSURE GRADIENT REMAINS STRONG BETWEEN THE DEPARTING LOW AND
A STRONG HIGH THAT WILL BE MOVING IN FROM THE WEST. WINDS WILL
TURN TO THE NORTH BY AFTERNOON THEN PROBABLY TURN MORE NORTHEAST
AS SPEEDS DROP OFF MONDAY EVENING AS THE HIGH REACHES THE LAKE.
LOW PRESSURE WILL DEVELOP ACROSS NORTHERN TEXAS MONDAY NIGHT AND
LIFT NORTHEASTWARD INTO EAST-CENTRAL ILLINOIS TUESDAY NIGHT WHILE
ANOTHER LOW MOVES ACROSS HUDSON BAY. RIDGING WILL REMAIN ACROSS THE
LAKE BUT THE NORTHERN SYSTEM LOOKS TO PASS CLOSE ENOUGH TO BRING
INCREASING SOUTH TO SOUTHWEST WINDS ACROSS THE FAR NORTHERN PART OF
THE LAKE TUESDAY AFTERNOON. THE GRADIENT WILL REMAIN WEAKER SOUTH
BUT A MORE SOUTHEASTERLY WIND DIRECTION SHOULD PREVAIL AHEAD OF THE
APPROACHING LOW. THE LOW WILL LIKELY PASS JUST TO THE SOUTHEAST OF
THE LAKE WEDNESDAY ALLOWING WINDS TO TURN NORTH OR NORTHEAST BEFORE
TURNING NORTHWEST WEDNESDAY EVENING. THE PATTERN REMAINS ACTIVE FROM
THAT POINT ONWARD WITH A SERIES OF HIGHS AND LOWS BRINGING UPS AND
DOWNS TO THE WIND SPEED FORECAST INTO NEXT WEEKEND.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...3 PM SUNDAY TO 6 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM SUNDAY TO 6 AM
MONDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM SUNDAY TO 9 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
319 AM CST SUN DEC 18 2011
.DISCUSSION...
849 PM CST
FORECAST CONCERNS/CHALLENGES ARE WITH SKY COVER TONIGHT...AS I AM
LITTLE CONCERNED CLOUD COVER MAY LINGER A LITTLE BIT LONGER THAN
PREVIOUSLY THOUGHT...AS WELL AS FOG DEVELOPMENT.
LARGE SCALE TROUGH WILL CONTINUE TO PUSH EAST TONIGHT WITH
ATTENDANT TROUGH OF LOW PRESSURE TO THE NORTH QUICKLY SHIFTING
EAST THROUGH NORTHERN MICHIGAN. MEANWHILE ACROSS THE CWA...SURFACE
RIDGE AXIS WILL SHIFT OVERHEAD WITH WINDS BECOMING MORE LIGHT AND
VARIABLE. ALTHOUGH...WEAK RIDGING ALOFT COINCIDING WITH A WAVE
SHIFTING SOUTHEAST ACROSS CANADA WILL ALLOW LOW/MID LEVEL WINDS TO
BACK MORE TO THE WEST/SOUTHWEST...WITH LATEST RUC ANALYSIS ALREADY
SHOWING THIS BEGINNING TO OCCUR. THIS IS THE START OF A PERIOD OF
WAA ACROSS MUCH OF THE REGION. ITS THIS WAA/WEAK FORCING RIDING
OVER A MOIST BOUNDARY LAYER FROM HIGHER DEWPOINT AIR AS WELL AS
THE RECENT SNOW...WHICH COULD HELP PROVIDE THE REDEVELOPMENT OF
LOW CEILINGS TONIGHT. CLEARING CURRENTLY ONGOING ACROSS A PORTION
OF NORTHERN ILLINOIS AND NORTHWEST INDIANA MAY INITIALLY BE
HINDERED BY THE LARGE CLOUD SHIELD SHIFTING EAST/SOUTHEAST ACROSS
MUCH OF WISCONSIN. THIS CLOUD SHIELD HAS SHOWN MORE OF A SOUTHERLY
PUSH RECENTLY AND THINK THAT IT WILL LINGER INTO NORTHEAST
ILLINOIS AND NORTHWEST ILLINOIS OVER THE NEXT COUPLE OF HOURS
BEFORE IT COMPLETELY EXITS TO THE EAST. ALTHOUGH...ITS DURING THIS
CLEARING TREND THAT THE REDEVELOPMENT OF LOW CEILINGS/FOG WILL BE
POSSIBLE ACROSS MOST OF THE CWA. THIS CLEARING AND LIGHTER WINDS
IN PLACE WILL ALLOW FOR GOOD RADIATIONAL COOLING TO
CONTINUE...WITH SEVERAL SITES ALREADY SHOWING RAPID TEMPERATURE
DROPS THIS EVENING.
WITH THESE CONCERNS IN MIND...THE RUC/VSREF HAVE BEEN HINTING AT
THE POSSIBILITY OF LOW CEILINGS/VIS WITH LOCATIONS NEAR
DEKALB/ROCHELL ALREADY SHOWING THESE TRENDS. ALTHOUGH AREAS OF FOG
WILL CONTINUE TO DEVELOP TONIGHT WITH SOME SITES OBSERVING VIS
AROUND THE 1-2SM RANGE...DONT THINK VIS WILL REMAIN THIS LOW WITH
STRATUS THEN DEVELOPING. LATEST GUIDANCE CONTINUES TO SHOW THAT
THERE WILL BE ENOUGH MOMENTUM IN THE BOUNDARY LAYER TO FAVOR
STRATUS.
THERE IS STILL UNCERTAINTY WITH SKY COVER TONIGHT...BUT HAVE
TRENDED MORE PESSIMISTIC IN THE GRIDS AND HAVE STARTED THE TREND
TOWARDS MORE CLOUDY SKIES BY SUNDAY MORNING. WILL LEAVE PARTLY
CLOUDY SKIES LATE TONIGHT BUT WILL HAVE TO CONTINUE TO MONITOR
LATEST TRENDS AND ADJUST ACCORDINGLY. HAVE ONLY MADE SOME MINOR
TEMP ADJUSTMENTS TONIGHT...MAINLY TO ACCOUNT FOR THE RAPID COOLING
IN AREAS WHICH HAVE ALREADY OBSERVED CLEAR SKIES.
RODRIGUEZ
//PREV DISCUSSION...
350 PM
LATE AFTERNOON THROUGH MONDAY...
AT MID AFTERNOON ANOTHER SHORT WAVE TROUGH MOVING EAST-SOUTHEAST
ACROSS LAKE SUPERIOR AND THE U.P. OF MI...TRAILING RIGHT BEHIND
THE SHORT WAVE...CURRENTLY OVER THE SOUTH CENTRAL GREAT LAKES
REGION...THAT GAVE AN INCH OR TWO TO MUCH OF OF SNOW TO MUCH OF
NORTH CENTRAL AND FAR NORTHEAST IL LATE LAST NIGHT AND THIS
MORNING...WITH LESSER AMOUNTS FURTHER SOUTH. THIS SECOND SHORT
WAVE WILL TRACK TOO FAR TO OUR NORTH AND NORTHEAST TO THREATEN
THE LOCAL AREA WITH ANY ADDITIONAL LIGHT SNOWFALL TONIGHT.
WIDESPREAD STRATOCUMULUS EXTENDS FROM IND NORTHWESTWARD ACROSS
EAST CENTRAL AND NORTHERN IL...ALL OF WI AND THE SOUTHEAST CORNER
OF MN. WHILE MODEL FORECAST TEMPERATURE AND DEW POINT DEPRESSION
PROFILES AS WELL AS PLAN DISPLAYS OF LOWER LEVEL RH FIELDS SHOW
THESE CLOUDS GRADUALLY CLEARING WEST TO E DURING THE LATE EVENING
AND EARLY A.M. HOURS THIS APPEARS TO BE A BIT FAST AND DO NOT
EXPECT TO SEE SIGNIFICANT CLEARING OVER THE EASTERN PORTIONS OF
THE FORECAST AREA UNTIL THE PRE-DAWN HOURS WHEN THE SECOND SHORT
WAVE TROUGH REACHES THE CENTRAL GREAT LAKES AND A SURFACE RIDGE
SHIFTS EAST ACROSS THE MS RIVER AND OVER THE LOCAL AREA BY 12Z
SUN.
RIDGING ALOFT SPREADS EAST FROM THE NORTHERN PLAINS TO OVER THE
UPPER MIDWEST AND THE LOCAL FORECAST AREA DURING SUNDAY MORNING
BETWEEN THE DEPARTING GREAT LAKES TROUGH AND ANOTHER SHORT WAVE
DIGGING SOUTHEAST OVER ALBERTA AND NORTHERN SASKATCHEWAN. RIDGING
SURFACE AND ALOFT ALONG WITH LOWER LEVEL WINDS BACKING TO SOUTH-
SOUTHWEST AND SOUTHWEST SUNDAY EXPECTED TO BE MOSTLY SUNNY AND
MILD FOR MID DECEMBER WITH TEMPERATURES UP INTO THE LOWER AND
MID 40S FOR THE AFTERNOON. A COLD FRONT EXTENDING FROM A SURFACE
LOW ASSOCIATED WITH THE SECOND SHORT WAVE SWEEPS ACROSS THE
REGION MONDAY NIGHT RETURNING COLDER AIR BUT TEMPERATURES STILL
EXPECTED TO BE FROM AROUND TO A BIT ABOVE NORMALS FOR THE DATE.
TUESDAY THROUGH SATURDAY...
THOUGHTS TURN TO HOLIDAY TRAVEL PLANS FOR NEXT WEEK. AT THIS
POINT LOOKS TO BE PRETTY GOOD CONDITIONS FOR THE AREA AS NO MAJOR
WINTER WEATHER IS EXPECTED.
OVERALL THEME OF MODEL RUNS FROM LAST NIGHT WAS THE IDEA OF LESS
PHASING OF THE CUT-OFF UPPER LOW TO BE OVER THE AZ/MEXICO BORDER
LATE SUNDAY AND A NORTHERN JET STREAM SHORT WAVE MOVING FROM
SOUTHERN B.C. AND THE PACIFIC NORTHWEST SOUTHEASTWARD TO THE
NORTHERN PLAINS...AND THEN EASTWARD ACROSS THE NORTHERN PLAINS
AND THE UPPER MIDWEST...FINALLY REACHING THE WESTERN GREAT LAKES
TUESDAY EVENING. MODEL RUNS FROM THIS MORNING AND MIDDAY
INCLUDING INDIVIDUAL ENSEMBLE MEMBERS MAINTAIN THEIR MEMBER TO
MEMBER...RUN TO RUN...AND MODEL TO MODEL AGREEMENT LEADING TO A
MORE SINGULAR SOLUTION. HOPEFULLY THIS WILL TURN OUT TO BE A
DECENT SOLUTION IF NOT THE BEST.
THIS MORE UNIFIED SOLUTION HAS THE CUT-OFF CLOSED UPPER
LOW...WHICH TAKES UP RESIDENCE OVER OR JUST WEST OF THE NORTHERN
BAJA PENINSULA TONIGHT INTO SATURDAY STARTING TO BE EJECTED BY A
DISTURBANCE DROPPING SOUTH-SOUTHEAST FROM THE GULF OF AK ALONG THE
PACIFIC COAST LATE SUNDAY THROUGH MONDAY. IN RESPONSE THE UPPER
LOW LIFTS NORTHEASTWARD OVER THE CENTRAL PLAINS TUESDAY AND THEN
GRADUALLY OPENS TO AN OPEN WAVE BY LATE WED AS IT CROSSES THE MID
MS VALLEY.
AS THE UPPER LOW/OPEN WAVE MOVES FROM THE EASTERN CENTRAL PLAINS
ACROSS THE MID MS VALLEY AND THE LOWER OH VALLEY LATE TUESDAY
NIGHT THROUGH WEDNESDAY IT WILL BASICALLY BE TRACKING TO THE EAST.
THIS KEEPS THE MAX PRECIP AXIS FROM MO EAST ACROSS SOUTHERN AND
CENTRAL IL AND THEN ACROSS IND...SOUTH OF THE LOCAL FORECAST AREA.
WHILE NORTHERN EDGE OF THE PRECIPITATION SHIELD IS EXPECTED TO
GRADUALLY CREEP FAR ENOUGH NORTHWARD TO GIVE AT LEAST CHANCE
THREAT OF PRECIPITATION FROM LATER MONDAY THROUGH WEDNESDAY.
PRECIPITATION STILL LOOKS TO BE RAIN WITH ONLY A VERY SMALL
THREAT OF MIXED RAIN AND SNOW OR LIGHT SNOW ACROSS THE FAR NORTH
COUNTIES TUESDAY NIGHT INTO WEDNESDAY MORNING AS THE
PRECIPITATION IS MOVING OFF TO THE EAST. LIQUID FORM FAVORED AS
SIGNIFICANT COLD AIR IS HELD AT BAY WITH QUICK PROGRESSION OF
DISTURBANCES MOVING THROUGH THE NORTHERN STREAM NOT PERMITTING
ANY STRONG COLD AIR ADVECTION TO OCCUR BEFORE FLOW BACKS AS THE
NEXT SHORT WAVE APPROACHES.
A RATHER SIGNIFICANT SHORT WAVE IS PROGGED TO DROP ACROSS THE
UPPER MIDWEST...UPPER AND MOD MO VALLEY...AND THE UPPER GREAT
LAKES WEDNESDAY NIGHT...MOVING TO OVER THE CENTRAL GREAT LAKES
BY MIDDAY FRIDAY. HOWEVER...DURING THIS TIME MODELS CONTINUE TO
SHOW A VERY LARGE STRONG ANTICYCLONE SPRAWLED FROM TX TO THE OH
VALLEY AND SOUTHERN GREAT LAKES. THIS WILL KEEP ANY SIGNIFICANT
AWAY FROM THE REGION WITH ONLY A POTENTIAL OF MAINLY LAKE EFFECT
SNOWS DOWNWIND OF THE LAKES.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 09Z...
* TIMING DEPARTURE OF CURRENT MVFR STRATUS.
* POTENTIAL FOR IFR/LIFR FOG/STRATUS DEVELOPMENT TOWARD DAYBREAK
ONCE CURRENT MVFR STRATUS CLEARS.
* LIGHT WEST-SOUTHWEST WINDS OVERNIGHT BECOMING SOUTHWEST AND
GUSTING 15-20 KTS SUNDAY AFTERNOON/EVENING.
MDB
//DISCUSSION...UPDATED 09Z...
MAIN BAND OF MVFR STRATUS CONTINUES TO MOVE EASTWARD AWAY FROM THE
AREA BUT A PORTION OF THE WESTERN FLANK HAS BROKEN OFF AN STARTED
MOVING SOUTHWEST ACROSS ORD/DPA/MDW. EXPECT THAT THIS BAND WILL
SCATTER OUT BUT CONFIDENCE IN HOW QUICKLY THIS WILL OCCUR IS NOT
TERRIBLY HIGH. NEXT CONCERN IS POTENTIAL FOR FOG AND NEW STRATUS
TO DEVELOP CLOSER TO DAYBREAK ONCE THE CURRENT MVFR STRATUS
SCATTERS. BAND OF CIRRUS IS NOW STREAMING IN FROM THE NORTHWEST
BUT BASED ON SATELLITE TRENDS THE COVERAGE WILL QUICKLY DECREASE
CLOSER TO DAYBREAK. OBS TO THE WEST SHOW A MIX OF CONDITIONS WITH
POCKETS OF IFR AND LOWER SHOWING UP IN SPOTS BUT MUCH OF THIS HAD
BEGUN DEVELOPING PRIOR TO THE ARRIVAL OF THE CIRRUS. WILL
CONTINUE WITH MENTION OF IFR AND LOWER VSBY/CIGS BUT SLOW THE
ARRIVAL DOWN ACROSS THE CHICAGO METRO TERMINALS THOUGH THIS MAY BE
TOO PESSIMISTIC SO WILL NEED TO CONTINUE TO MONITOR.
MDB
FROM 06Z...
UPPER-LEVEL DISTURBANCE PULLING EAST OF THE FORECAST AREA LATE
THIS EVENING...WITH CLEARING SKIES SPREADING QUICKLY EAST AS
SUBSIDENCE DEVELOPS BEHIND DEPARTING UPPER TROUGH. EXTRAPOLATION
FROM SATELLITE IMAGERY INDICATES MVFR CIGS WILL CLEAR ORD/MDW
SHORTLY AFTER 06Z AND CLEAR GYY BY 0730Z. QUESTION REMAINS THE
POTENTIAL FOR FOG/LOW STRATUS DEVELOPMENT ACROSS NORTHERN IL AS
SKIES CLEAR AND TEMPERATURES DROP. RPJ/RFD/DKB DISPLAYED QUICK
TEMP DROPS AND FOG/STRATUS DEVELOPMENT EARLIER IN THE EVENING
BEFORE MVFR DECK SPREAD BACK ACROSS THOSE SITES...AND CONCERN IS
THAT SIMILAR TREND WILL OCCUR WITH CLEARING IN NEXT FEW HOURS. 00Z
MODEL SOUNDINGS CONTINUE TO DEPICT VERY SHALLOW BOUNDARY LAYER
SATURATING AT BOTH KRFD/KDPA...SUGGESTING FOG AND PERHAPS IFR OR
EVEN LIFR CEILING DEVELOPMENT. WHILE CONFIDENCE THAT VISIBILITY
WILL LOWER INTO MVFR RANGE IN MANY PLACES...VERY LOW CONFIDENCE
REMAINS WITH COVERAGE OF WHAT MAY BE PATCHY IFR/LIFR CONDITIONS.
HAVE MAINTAINED THE MIDDLE OF THE ROAD THINKING FROM 03Z
AMENDMENTS WITH TEMPO IFR CONDITIONS EARLY SUNDAY MORNING. IF MORE
EXTENSIVE IFR/LIFR DOES DEVELOP...IT MAY TAKE UNTIL 15-16Z BEFORE
STRATUS IS ABLE TO MIX OUT GIVEN RELATIVELY LATE SUNRISE ON NEARLY
THE SHORTEST DAY OF THE YEAR.
IMPROVEMENT TO VFR CONDITIONS IS EXPECTED BY MID-LATE MORNING
HOWEVER...EARLIER IF WIDESPREAD IFR DOES NOT DEVELOP. LOW PRESSURE
MOVING ACROSS CANADA WILL HELP TO TIGHTEN THE PRESSURE GRADIENT
ACROSS THE MIDWEST...WITH SOUTHWEST WINDS INCREASING AND BECOMING
GUSTY IN THE 15-20 KT RANGE IN THE AFTERNOON AND PERHAPS A FEW KTS
HIGHER AT KRFD. WILL LIKELY LOSE HIGHER GUSTS WITH SUNSET BUT
MAINTAIN SUSTAINED WINDS IN THE 10-15 KT RANGE.
LOW LEVEL MOISTURE INCREASES SUNDAY NIGHT AS FAIRLY STRONG WARM
ADVECTION CONTINUES...AND WILL LIKELY SEE VFR CEILINGS DEVELOPING
OVERNIGHT.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 09Z...
* MEDIUM CONFIDENCE IN TIMING OF DEPARTURE OF CURRENT MVFR STRATUS.
* MEDIUM-HIGH CONFIDENCE IN PATCHY IFR FOG/STRATUS DEVELOPING ONCE
STRATUS CLEARS... BUT LOW CONFIDENCE ON DIRECT IMPACT AT ORD/MDW
TERMINALS.
* HIGH CONFIDENCE IN VFR CONDITIONS SUNDAY AFTER ANY MORNING
FOG/STRATUS DISSIPATES.
* HIGH CONFIDENCE IN WIND TRENDS.
MDB
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN...PSBLY MIXED WITH SNOW AT
ONSET TUES. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
RATZER
&&
.MARINE...
315 AM CST
...SOUTHWEST GALES DEVELOP THIS AFTERNOON...
A SERIES OF RIDGES AND TROUGHS DOT THE EARLY MORNING WEATHER MAP.
HIGH PRESSURE EXTENDS FROM EASTERN QUEBEC INTO NORTHERN NEW ENGLAND
AND IS WORKING TOWARDS THE ATLANTIC WHILE LOW PRESSURE OVER HUDSON
BAY MOVES EASTWARD DRAGGING A TROUGH ACROSS LAKE HURON AND SOUTHERN
ONTARIO. WEAK RIDGING IS POSITIONED TO THE WEST OF THE TROUGH AND
WILL CREST OVER LAKE MICHIGAN THIS MORNING. THE MOST NOTABLE FEATURE
IS LOW PRESSURE MOVING FROM CENTRAL SASKATCHEWAN INTO CENTRAL
MANITOBA. THIS LOW WILL DEEPEN AS IT MOVES EAST TODAY TIGHTENING THE
PRESSURE GRADIENT ACROSS THE UPPER LAKES THIS AFTERNOON. THE LOW WILL
DRAG A TROUGH ACROSS THE LAKE EARLY MONDAY MORNING WHICH WILL SHIFT
WINDS TO NORTHWESTERLY. IN TERMS OF TRENDS...WINDS WILL BEGIN TO
SLACKEN SOMEWHAT THIS MORNING AS THE RIDGE MOVES ACROSS BUT THEN
QUICKLY PICK UP FROM THE SOUTHWEST THIS AFTERNOON AS THE DEEPENING
LOW MOVES INTO WESTERN ONTARIO AND JUST NORTH OF LAKE SUPERIOR BY
EVENING. AM EXPECTING SPEEDS TO REACH GALE FORCE TO 40 KT BY LATE
AFTERNOON NORTH AND CONTINUE THROUGH THE EVENING THEN SLOWLY BEGIN
TO DIMINISH TO 35 KT GALES AFTER MIDNIGHT WITH A REDUCTION TO
BELOW GALE TOWARD DAYBREAK. STRONGEST SPEEDS WILL BE ACROSS THE
NORTHERN HALF TO TWO-THIRDS OF THE LAKE WITH SPEEDS A FEW KNOTS
LOWER AND SLIGHTLY SLOWER IN ARRIVING ACROSS THE SOUTH. SPEEDS
WILL LIKELY REMAIN IN THE 20 TO 25 KT RANGE FOR MOST OF MONDAY AS
THE PRESSURE GRADIENT REMAINS STRONG BETWEEN THE DEPARTING LOW AND
A STRONG HIGH THAT WILL BE MOVING IN FROM THE WEST. WINDS WILL
TURN TO THE NORTH BY AFTERNOON THEN PROBABLY TURN MORE NORTHEAST
AS SPEEDS DROP OFF MONDAY EVENING AS THE HIGH REACHES THE LAKE.
LOW PRESSURE WILL DEVELOP ACROSS NORTHERN TEXAS MONDAY NIGHT AND
LIFT NORTHEASTWARD INTO EAST-CENTRAL ILLINOIS TUESDAY NIGHT WHILE
ANOTHER LOW MOVES ACROSS HUDSON BAY. RIDGING WILL REMAIN ACROSS THE
LAKE BUT THE NORTHERN SYSTEM LOOKS TO PASS CLOSE ENOUGH TO BRING
INCREASING SOUTH TO SOUTHWEST WINDS ACROSS THE FAR NORTHERN PART OF
THE LAKE TUESDAY AFTERNOON. THE GRADIENT WILL REMAIN WEAKER SOUTH
BUT A MORE SOUTHEASTERLY WIND DIRECTION SHOULD PREVAIL AHEAD OF THE
APPROACHING LOW. THE LOW WILL LIKELY PASS JUST TO THE SOUTHEAST OF
THE LAKE WEDNESDAY ALLOWING WINDS TO TURN NORTH OR NORTHEAST BEFORE
TURNING NORTHWEST WEDNESDAY EVENING. THE PATTERN REMAINS ACTIVE FROM
THAT POINT ONWARD WITH A SERIES OF HIGHS AND LOWS BRINGING UPS AND
DOWNS TO THE WIND SPEED FORECAST INTO NEXT WEEKEND.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...3 PM SUNDAY TO 6 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM SUNDAY TO 6 AM
MONDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM SUNDAY TO 9 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1053 PM CST SAT DEC 17 2011
.DISCUSSION...
849 PM CST
FORECAST CONCERNS/CHALLENGES ARE WITH SKY COVER TONIGHT...AS I AM
LITTLE CONCERNED CLOUD COVER MAY LINGER A LITTLE BIT LONGER THAN
PREVIOUSLY THOUGHT...AS WELL AS FOG DEVELOPMENT.
LARGE SCALE TROUGH WILL CONTINUE TO PUSH EAST TONIGHT WITH
ATTENDANT TROUGH OF LOW PRESSURE TO THE NORTH QUICKLY SHIFTING
EAST THROUGH NORTHERN MICHIGAN. MEANWHILE ACROSS THE CWA...SURFACE
RIDGE AXIS WILL SHIFT OVERHEAD WITH WINDS BECOMING MORE LIGHT AND
VARIABLE. ALTHOUGH...WEAK RIDGING ALOFT COINCIDING WITH A WAVE
SHIFTING SOUTHEAST ACROSS CANADA WILL ALLOW LOW/MID LEVEL WINDS TO
BACK MORE TO THE WEST/SOUTHWEST...WITH LATEST RUC ANALYSIS ALREADY
SHOWING THIS BEGINNING TO OCCUR. THIS IS THE START OF A PERIOD OF
WAA ACROSS MUCH OF THE REGION. ITS THIS WAA/WEAK FORCING RIDING
OVER A MOIST BOUNDARY LAYER FROM HIGHER DEWPOINT AIR AS WELL AS
THE RECENT SNOW...WHICH COULD HELP PROVIDE THE REDEVELOPMENT OF
LOW CEILINGS TONIGHT. CLEARING CURRENTLY ONGOING ACROSS A PORTION
OF NORTHERN ILLINOIS AND NORTHWEST INDIANA MAY INITIALLY BE
HINDERED BY THE LARGE CLOUD SHIELD SHIFTING EAST/SOUTHEAST ACROSS
MUCH OF WISCONSIN. THIS CLOUD SHIELD HAS SHOWN MORE OF A SOUTHERLY
PUSH RECENTLY AND THINK THAT IT WILL LINGER INTO NORTHEAST
ILLINOIS AND NORTHWEST ILLINOIS OVER THE NEXT COUPLE OF HOURS
BEFORE IT COMPLETELY EXITS TO THE EAST. ALTHOUGH...ITS DURING THIS
CLEARING TREND THAT THE REDEVELOPMENT OF LOW CEILINGS/FOG WILL BE
POSSIBLE ACROSS MOST OF THE CWA. THIS CLEARING AND LIGHTER WINDS
IN PLACE WILL ALLOW FOR GOOD RADIATIONAL COOLING TO
CONTINUE...WITH SEVERAL SITES ALREADY SHOWING RAPID TEMPERATURE
DROPS THIS EVENING.
WITH THESE CONCERNS IN MIND...THE RUC/VSREF HAVE BEEN HINTING AT
THE POSSIBILITY OF LOW CEILINGS/VIS WITH LOCATIONS NEAR
DEKALB/ROCHELL ALREADY SHOWING THESE TRENDS. ALTHOUGH AREAS OF FOG
WILL CONTINUE TO DEVELOP TONIGHT WITH SOME SITES OBSERVING VIS
AROUND THE 1-2SM RANGE...DONT THINK VIS WILL REMAIN THIS LOW WITH
STRATUS THEN DEVELOPING. LATEST GUIDANCE CONTINUES TO SHOW THAT
THERE WILL BE ENOUGH MOMENTUM IN THE BOUNDARY LAYER TO FAVOR
STRATUS.
THERE IS STILL UNCERTAINTY WITH SKY COVER TONIGHT...BUT HAVE
TRENDED MORE PESSIMISTIC IN THE GRIDS AND HAVE STARTED THE TREND
TOWARDS MORE CLOUDY SKIES BY SUNDAY MORNING. WILL LEAVE PARTLY
CLOUDY SKIES LATE TONIGHT BUT WILL HAVE TO CONTINUE TO MONITOR
LATEST TRENDS AND ADJUST ACCORDINGLY. HAVE ONLY MADE SOME MINOR
TEMP ADJUSTMENTS TONIGHT...MAINLY TO ACCOUNT FOR THE RAPID COOLING
IN AREAS WHICH HAVE ALREADY OBSERVED CLEAR SKIES.
RODRIGUEZ
//PREV DISCUSSION...
350 PM
LATE AFTERNOON THROUGH MONDAY...
AT MID AFTERNOON ANOTHER SHORT WAVE TROUGH MOVING EAST-SOUTHEAST
ACROSS LAKE SUPERIOR AND THE U.P. OF MI...TRAILING RIGHT BEHIND
THE SHORT WAVE...CURRENTLY OVER THE SOUTH CENTRAL GREAT LAKES
REGION...THAT GAVE AN INCH OR TWO TO MUCH OF OF SNOW TO MUCH OF
NORTH CENTRAL AND FAR NORTHEAST IL LATE LAST NIGHT AND THIS
MORNING...WITH LESSER AMOUNTS FURTHER SOUTH. THIS SECOND SHORT
WAVE WILL TRACK TOO FAR TO OUR NORTH AND NORTHEAST TO THREATEN
THE LOCAL AREA WITH ANY ADDITIONAL LIGHT SNOWFALL TONIGHT.
WIDESPREAD STRATOCUMULUS EXTENDS FROM IND NORTHWESTWARD ACROSS
EAST CENTRAL AND NORTHERN IL...ALL OF WI AND THE SOUTHEAST CORNER
OF MN. WHILE MODEL FORECAST TEMPERATURE AND DEW POINT DEPRESSION
PROFILES AS WELL AS PLAN DISPLAYS OF LOWER LEVEL RH FIELDS SHOW
THESE CLOUDS GRADUALLY CLEARING WEST TO E DURING THE LATE EVENING
AND EARLY A.M. HOURS THIS APPEARS TO BE A BIT FAST AND DO NOT
EXPECT TO SEE SIGNIFICANT CLEARING OVER THE EASTERN PORTIONS OF
THE FORECAST AREA UNTIL THE PRE-DAWN HOURS WHEN THE SECOND SHORT
WAVE TROUGH REACHES THE CENTRAL GREAT LAKES AND A SURFACE RIDGE
SHIFTS EAST ACROSS THE MS RIVER AND OVER THE LOCAL AREA BY 12Z
SUN.
RIDGING ALOFT SPREADS EAST FROM THE NORTHERN PLAINS TO OVER THE
UPPER MIDWEST AND THE LOCAL FORECAST AREA DURING SUNDAY MORNING
BETWEEN THE DEPARTING GREAT LAKES TROUGH AND ANOTHER SHORT WAVE
DIGGING SOUTHEAST OVER ALBERTA AND NORTHERN SASKATCHEWAN. RIDGING
SURFACE AND ALOFT ALONG WITH LOWER LEVEL WINDS BACKING TO SOUTH-
SOUTHWEST AND SOUTHWEST SUNDAY EXPECTED TO BE MOSTLY SUNNY AND
MILD FOR MID DECEMBER WITH TEMPERATURES UP INTO THE LOWER AND
MID 40S FOR THE AFTERNOON. A COLD FRONT EXTENDING FROM A SURFACE
LOW ASSOCIATED WITH THE SECOND SHORT WAVE SWEEPS ACROSS THE
REGION MONDAY NIGHT RETURNING COLDER AIR BUT TEMPERATURES STILL
EXPECTED TO BE FROM AROUND TO A BIT ABOVE NORMALS FOR THE DATE.
TUESDAY THROUGH SATURDAY...
THOUGHTS TURN TO HOLIDAY TRAVEL PLANS FOR NEXT WEEK. AT THIS
POINT LOOKS TO BE PRETTY GOOD CONDITIONS FOR THE AREA AS NO MAJOR
WINTER WEATHER IS EXPECTED.
OVERALL THEME OF MODEL RUNS FROM LAST NIGHT WAS THE IDEA OF LESS
PHASING OF THE CUT-OFF UPPER LOW TO BE OVER THE AZ/MEXICO BORDER
LATE SUNDAY AND A NORTHERN JET STREAM SHORT WAVE MOVING FROM
SOUTHERN B.C. AND THE PACIFIC NORTHWEST SOUTHEASTWARD TO THE
NORTHERN PLAINS...AND THEN EASTWARD ACROSS THE NORTHERN PLAINS
AND THE UPPER MIDWEST...FINALLY REACHING THE WESTERN GREAT LAKES
TUESDAY EVENING. MODEL RUNS FROM THIS MORNING AND MIDDAY
INCLUDING INDIVIDUAL ENSEMBLE MEMBERS MAINTAIN THEIR MEMBER TO
MEMBER...RUN TO RUN...AND MODEL TO MODEL AGREEMENT LEADING TO A
MORE SINGULAR SOLUTION. HOPEFULLY THIS WILL TURN OUT TO BE A
DECENT SOLUTION IF NOT THE BEST.
THIS MORE UNIFIED SOLUTION HAS THE CUT-OFF CLOSED UPPER
LOW...WHICH TAKES UP RESIDENCE OVER OR JUST WEST OF THE NORTHERN
BAJA PENINSULA TONIGHT INTO SATURDAY STARTING TO BE EJECTED BY A
DISTURBANCE DROPPING SOUTH-SOUTHEAST FROM THE GULF OF AK ALONG THE
PACIFIC COAST LATE SUNDAY THROUGH MONDAY. IN RESPONSE THE UPPER
LOW LIFTS NORTHEASTWARD OVER THE CENTRAL PLAINS TUESDAY AND THEN
GRADUALLY OPENS TO AN OPEN WAVE BY LATE WED AS IT CROSSES THE MID
MS VALLEY.
AS THE UPPER LOW/OPEN WAVE MOVES FROM THE EASTERN CENTRAL PLAINS
ACROSS THE MID MS VALLEY AND THE LOWER OH VALLEY LATE TUESDAY
NIGHT THROUGH WEDNESDAY IT WILL BASICALLY BE TRACKING TO THE EAST.
THIS KEEPS THE MAX PRECIP AXIS FROM MO EAST ACROSS SOUTHERN AND
CENTRAL IL AND THEN ACROSS IND...SOUTH OF THE LOCAL FORECAST AREA.
WHILE NORTHERN EDGE OF THE PRECIPITATION SHIELD IS EXPECTED TO
GRADUALLY CREEP FAR ENOUGH NORTHWARD TO GIVE AT LEAST CHANCE
THREAT OF PRECIPITATION FROM LATER MONDAY THROUGH WEDNESDAY.
PRECIPITATION STILL LOOKS TO BE RAIN WITH ONLY A VERY SMALL
THREAT OF MIXED RAIN AND SNOW OR LIGHT SNOW ACROSS THE FAR NORTH
COUNTIES TUESDAY NIGHT INTO WEDNESDAY MORNING AS THE
PRECIPITATION IS MOVING OFF TO THE EAST. LIQUID FORM FAVORED AS
SIGNIFICANT COLD AIR IS HELD AT BAY WITH QUICK PROGRESSION OF
DISTURBANCES MOVING THROUGH THE NORTHERN STREAM NOT PERMITTING
ANY STRONG COLD AIR ADVECTION TO OCCUR BEFORE FLOW BACKS AS THE
NEXT SHORT WAVE APPROACHES.
A RATHER SIGNIFICANT SHORT WAVE IS PROGGED TO DROP ACROSS THE
UPPER MIDWEST...UPPER AND MOD MO VALLEY...AND THE UPPER GREAT
LAKES WEDNESDAY NIGHT...MOVING TO OVER THE CENTRAL GREAT LAKES
BY MIDDAY FRIDAY. HOWEVER...DURING THIS TIME MODELS CONTINUE TO
SHOW A VERY LARGE STRONG ANTICYCLONE SPRAWLED FROM TX TO THE OH
VALLEY AND SOUTHERN GREAT LAKES. THIS WILL KEEP ANY SIGNIFICANT
AWAY FROM THE REGION WITH ONLY A POTENTIAL OF MAINLY LAKE EFFECT
SNOWS DOWNWIND OF THE LAKES.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* POTENTIAL FOR IFR/LIFR FOG/STRATUS DEVELOPMENT OVERNIGHT.
* LIGHT WEST-SOUTHWEST WINDS OVERNIGHT BECOMING SOUTHWEST AND
GUSTING 15-20 KTS SUNDAY AFTERNOON/EVENING.
RATZER
//DISCUSSION...UPDATED 06Z...
UPPER-LEVEL DISTURBANCE PULLING EAST OF THE FORECAST AREA LATE
THIS EVENING...WITH CLEARING SKIES SPREADING QUICKLY EAST AS
SUBSIDENCE DEVELOPS BEHIND DEPARTING UPPER TROUGH. EXTRAPOLATION
FROM SATELLITE IMAGERY INDICATES MVFR CIGS WILL CLEAR ORD/MDW
SHORTLY AFTER 06Z AND CLEAR GYY BY 0730Z. QUESTION REMAINS THE
POTENTIAL FOR FOG/LOW STRATUS DEVELOPMENT ACROSS NORTHERN IL AS
SKIES CLEAR AND TEMPERATURES DROP. RPJ/RFD/DKB DISPLAYED QUICK
TEMP DROPS AND FOG/STRATUS DEVELOPMENT EARLIER IN THE EVENING
BEFORE MVFR DECK SPREAD BACK ACROSS THOSE SITES...AND CONCERN IS
THAT SIMILAR TREND WILL OCCUR WITH CLEARING IN NEXT FEW HOURS. 00Z
MODEL SOUNDINGS CONTINUE TO DEPICT VERY SHALLOW BOUNDARY LAYER
SATURATING AT BOTH KRFD/KDPA...SUGGESTING FOG AND PERHAPS IFR OR
EVEN LIFR CEILING DEVELOPMENT. WHILE CONFIDENCE THAT VISIBILITY
WILL LOWER INTO MVFR RANGE IN MANY PLACES...VERY LOW CONFIDENCE
REMAINS WITH COVERAGE OF WHAT MAY BE PATCHY IFR/LIFR CONDITIONS.
HAVE MAINTAINED THE MIDDLE OF THE ROAD THINKING FROM 03Z
AMENDMENTS WITH TEMPO IFR CONDITIONS EARLY SUNDAY MORNING. IF MORE
EXTENSIVE IFR/LIFR DOES DEVELOP...IT MAY TAKE UNTIL 15-16Z BEFORE
STRATUS IS ABLE TO MIX OUT GIVEN RELATIVELY LATE SUNRISE ON NEARLY
THE SHORTEST DAY OF THE YEAR.
IMPROVEMENT TO VFR CONDITIONS IS EXPECTED BY MID-LATE MORNING
HOWEVER...EARLIER IF WIDESPREAD IFR DOES NOT DEVELOP. LOW PRESSURE
MOVING ACROSS CANADA WILL HELP TO TIGHTEN THE PRESSURE GRADIENT
ACROSS THE MIDWEST...WITH SOUTHWEST WINDS INCREASING AND BECOMING
GUSTY IN THE 15-20 KT RANGE IN THE AFTERNOON AND PERHAPS A FEW KTS
HIGHER AT KRFD. WILL LIKELY LOSE HIGHER GUSTS WITH SUNSET BUT
MAINTAIN SUSTAINED WINDS IN THE 10-15 KT RANGE.
LOW LEVEL MOISTURE INCREASES SUNDAY NIGHT AS FAIRLY STRONG WARM
ADVECTION CONTINUES...AND WILL LIKELY SEE VFR CEILINGS DEVELOPING
OVERNIGHT.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* MEDIUM-HIGH CONFIDENCE IN PATCHY IFR FOG/STRATUS DEVELOPING...
BUT LOW CONFIDENCE ON DIRECT IMPACT AT ORD/MDW TERMINALS.
* HIGH CONFIDENCE IN VFR CONDITIONS SUNDAY AFTER ANY MORNING
FOG/STRATUS DISSIPATES.
* HIGH CONFIDENCE IN WIND TRENDS.
RATZER
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY...MVFR CIGS POSSIBLE. CHC RAIN MAINLY SOUTH OF ORD/MDW.
TUESDAY AND WEDNESDAY...CHC RAIN...PSBLY MIXED WITH SNOW AT
ONSET TUES. MVFR/IFR CIGS POSSIBLE.
THURSDAY...MAINLY VFR. CHC OF FLURRIES/MVFR CIGS LATE.
FRIDAY...CHC FLURRIES.
RATZER
&&
.MARINE...
219 PM CST
A PROGRESSIVE WEATHER PATTERN ACROSS THE GREAT LAKES WILL CONTINUE
TO USHER MULTIPLE GUSTY SYSTEMS OVER THE REGION THE NEXT COUPLE OF
DAYS. THE FIRST ONE CENTERED OVER NORTHERN ONTARIO TONIGHT WILL
SWING A TROUGH THROUGH LAKE MICHIGAN THROUGH THE EVENING...TURNING
WINDS TO THE WEST...EVEN SLIGHTLY NORTHWEST IN PARTS OF THE OPEN
WATER. SOME WINDS UP TO 30 KTS ARE POSSIBLE WITH THIS
REGIME...MAINLY IN THE NORTH CLOSER TO THE SYSTEM. A STRONGER LOW
PRESSURE NORTH OF LAKE SUPERIOR WILL RACE EAST ON SUNDAY AFTERNOON
AND EVENING...SWEEPING A COLD FRONT THROUGH THE LAKE SUNDAY NIGHT
INTO EARLY MONDAY. THE TIGHT GRADIENT AROUND THIS LOW AND DEEPER
MIXING WILL SUPPORT GALES ACROSS THE LAKE BEGINNING LATE SUNDAY
AFTERNOON OVER THE NORTH AND SUNDAY EVENING OVER THE SOUTH. THE
WINDOW OF TIME FOR THE GALES WILL BE SHORT...ONLY THROUGH SUNDAY
NIGHT...DUE TO THE QUICK MOVEMENT OF THE SYSTEM. PREVAILING WAVES
UP TO 14 FT ARE EXPECTED ACROSS OPEN WATERS OF THE FAR NORTH. THE
NORTHWEST FLOW BEHIND THE FRONT WILL STILL BE BREEZY ON MONDAY
DESPITE THE WIND SPEEDS GRADUALLY DIMINISHING. HIGH PRESSURE WILL
MOVE OVER THE LAKE MONDAY NIGHT INTO THE DAY TUESDAY.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...3 PM SUNDAY TO 6 AM MONDAY.
GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM SUNDAY TO 6 AM
MONDAY.
SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...6 PM SUNDAY TO 9 AM MONDAY.
&&
$$
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
512 PM CST MON DEC 19 2011
.AVIATION...
A STORM SYSTEM WILL SLOWLY MOVE TOWARD IOWA AND ILLINOIS DURING
THE NEXT 24 HOURS. THIS STORM WILL SPREAD MVFR TO IFR CIGS AND
VISIBILITIES OVER THE REGION LATE TONIGHT AND TOMORROW...MAINLY IN
THE FORM OF DRIZZLE AND LOW CLOUDS. SNOW AND ICE PELLETS ARE
POSSIBLE LATE TONIGHT AT BRL...BUT THE TIMING OF THE ONSET IS VERY
LOW CONFIDENCE. THUS...IT MAY HOLD OFF UNTIL TOWARDS 12Z. SOME
EARLY EVENING STRATUS MAY CONTINUE TO AFFECT DBQ AND MLI...WHICH
IS UNRELATED TO THE UPCOMING STORM SYSTEM. THIS STRATUS SHOULD
BREAK UP LATER TONIGHT AS DRY AIR ARRIVES FROM THE NORTH...BEFORE
THE DAYTIME INCREASE IN LOW LEVEL MOISTURE TUESDAY. WINDS WILL BE
NORTH TO NORTHEAST THROUGH THE PERIOD AROUND 6 TO 10 KTS.
&&
.PREV DISCUSSION... /ISSUED 315 PM CST MON DEC 19 2011/
SYNOPSIS...
12Z UA ANALYSIS HAD THE STORM SYSTEM DEVELOPING IN THE SOUTHERN
ROCKIES WITH A LLJ OF 40-50 KNOTS TRANSPORTING MOISTURE NORTH INTO
THE PLAINS AND OHIO VALLEY. AN 850MB COLD FRONT RAN FROM NORTHERN
LAKE HURON INTO NORTHEAST COLORADO. SATELLITE AND RADAR TRENDS
THROUGH MID AFTERNOON SHOWED INCREASING CLOUDS ACROSS THE AREA WITH
PRECIPITATION GENERALLY SOUTH OF A KSTJ TO KUIN LINE.
18Z SFC ANALYSIS HAD A COLD FRONT RUNNING FROM KOSC...TO KMCI...TO
AROUND KDHT. LOW PRESSURES FROM THE DEVELOPING STORM SYSTEM WERE
SOUTH OF KTCC AND NEAR KPPA. DEW POINTS WERE IN THE 40S JUST AHEAD
OF THE COLD FRONT INTO THE OHIO VALLEY WITH 50S CROSSING THE RED
RIVER INTO OKLAHOMA. DEW POINTS IN THE 20S AND 30S WERE ACROSS MUCH
OF THE NORTHERN/CENTRAL PLAINS AND UPPER MIDWEST.
SHORT TERM...TONIGHT AND TUESDAY...
THE MAIN QUESTION IS HOW LONG WILL THE DRY AIR KEEP THE
PRECIPITATION AT BAY TONIGHT INTO TUESDAY. BASED ON 12Z UA DATA...
THE WRF INITIALIZED A LITTLE BETTER THAN THE OTHER MODELS BASED ON
LOW LEVEL MOISTURE.
CONDENSATION PRESSURE DEFICITS ON EITHER STANDARD SURFACES OR THE
290-925K THETA SFC HAVE BEEN DEPICTING WELL THE AREAL COVERAGE OF
THE PRECIPITATION LATE THIS MORNING AND AFTERNOON. ALL MODELS HAVE
GENERALLY SHOWED THIS BUT THE RUC TRENDS HAVE DONE VERY WELL AND THE
RUC WILL BE USED FOR THE IMMEDIATE SHORT TERM.
BASED ON THE RUC CONDENSATION PRESSURE DEFICIT TRENDS...THE EARLY
EVENING WILL REMAIN DRY ACROSS THE ENTIRE AREA. BETWEEN 9 PM AND
MIDNIGHT PRECIPITATION WILL ADVECT/DEVELOP GENERALLY SOUTH OF A KOTM
TO KPIA LINE. FCST SOUNDINGS SHOW A TOP DOWN SATURATION TAKING PLACE
SO THERE WILL BE PLENTY OF EVAPORATIVE COOLING TAKING PLACE. THUS A
RAIN/SNOW MIX WILL DEVELOP THAT WILL LIKELY HAVE A BRIEF PERIOD OF
SLEET AS THE PRECIPITATION DEVELOPS. THERE IS A CONCERN BASED ON HOW
WARM IT HAS GOTTEN TODAY THAT PTYPE COULD BE MORE LIQUID THAN
FREEZING OR FROZEN.
AFTER MIDNIGHT...THE PRECIPITATION SHIELD WILL SLOWLY MOVE
NORTHWARD...REACHING A KOTM TO KGBG LINE AROUND 3 AM AND ROUGHLY A
KOOA TO KC75 LINE AROUND 12Z. THE I-80 CORRIDOR ON NORTH WILL REMAIN
DRY THROUGH SUNRISE. MINS TONIGHT WILL BE HIGHLY DEPENDENT ON CLOUD
COVER AND HOW THE PRECIPITATION SHIELD EVOLVES.
SNOW AMOUNTS SHOULD BE ONE HALF INCH OR LESS TONIGHT.
ON TUESDAY...THE PRECIPITATION SHIELD WILL CONTINUE MOVING NORTH AND
REACH I-80 ROUGHLY AROUND 9 AM AND SHOULD BE AROUND A VINTON TO MT
CARROLL LINE BY MID DAY. THE IMMEDIATE HWY 20 CORRIDOR IS EXPECTED
REMAIN DRY DURING THE MORNING HOURS. EVAPORATIVE COOLING WILL
CONTINUE TO PLAY SIGNIFICANTLY IN PTYPE WITH A RAIN/SNOW MIX ALONG
WITH A BRIEF PERIOD OF SLEET.
BY LATE MORNING AND INTO THE AFTERNOON HOURS...THE OVERALL FORCING
ACROSS THE AREA DECREASES. THE OVERALL PRECIPITATION INTENSITY WILL
LET UP AND A CHANGE OVER TO MAINLY RAIN IS EXPECTED EXCEPT ACROSS
ROUGHLY THE NORTHWEST THIRD OR SO OF THE CWFA WHERE A MIX IS STILL
EXPECTED. THE RAIN MAY STOP OR GO TO MORE DRIZZLE DURING THE
AFTERNOON HOURS.
SNOW AMOUNTS ON TUESDAY SHOULD BE ONE HALF INCH OR LESS. ..08..
LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...
TUESDAY NIGHT AND WEDNESDAY...LATEST 12Z RUNS HAVE SHIFTED SLIGHTLY
BACK SOUTHWARD WITH RESPECT TO MAIN SFC LOW AND MID LEVEL
PROPAGATION PATHS LATER TUE THROUGH WED. WILL SIDE THE NEW 12Z RUN
ECMWF AND NAM WHICH ARE IN GOOD AGREEMENT WITH THEIR MASS FIELDS
WITH EACH OTHER AND THERE SOLUTIONS ARE IN THE MIDDLE OF THE ROAD OF
THE ENSEMBLES OF THESE FEATURES. THESE ACCEPTED SOLUTIONS SUGGEST
THAT THE SFC LOW WILL BE ACRS FAR SOUTHWEST MO AT 00Z WED...AND MOVE
NORTHEASTWARD TO THE EAST CENTRAL IL/WEST CENTRAL INDIANA BORDER
REGION BY 12Z WED WITH EYES ON THE WESTERN BASIN OF LK ERIE BY
MIDDAY WED. UPPER LOW TILTED TO THE NORTHWEST OF THE LLVL CYCLONE
WILL STILL LOOK TO PROGRESS ACRS THE SOUTHWEST HALF OF THE CWA BY
WED MORNING STILL IN A CLOSED FASHION AND THEN LOOK TO OPEN UP ON
THE WAY TO OVER THE SOUTH HALF OF LK MI BY WED AFTERNOON. ACCEPTED
THERMAL PROFILES SUGGEST LIGHT RAIN ACRS THE SOUTHEAST HALF OF THE
DVN CWA TUE EVENING WITH SOME SLEET POSSIBLY MIXED IN THE NORTHERN
FRINGE OF THE RAIN AT SFC BAND UP ALONG THE SOUTHERN I80 CORRIDOR.
WITH THE MODELS STILL SUGGESTING THE MAIN THRUST OF WARM MOIST
CONVEYOR SHUNTED OFF TO THE EAST AND SOUTHEAST OF THE AREA BY LATE
TUE...THE APPROACHING UPPER LOW WILL ONLY HAVE TO WORK WITH
SECONDARY MOISTURE FEED AND THUS ONLY A LIGHT PRECIP EVENT STILL
LOOKS ON TAP FOR TUE NIGHT FOR THE MAJORITY OF THE DVN CWA. THERMAL
PROFILES TUE EVENING ALONG AND NORTH OF A LINE FROM MT CARROLL IL...
TO CID AND SOUTHWEST OF IOWA CITY SUGGEST LIGHT SNOW AND SLEET IN
THESE AREAS TUE EVENING...AND ONLY FLURRIES ALONG AND NORTH OF THE
HWY 20 CORRIDOR. SNOW AND SLEET ACCUMS UNDER AN INCH TUE EVENING IN
THESE AREAS...BUT A CHANCE OF A NARROW SWATH OF 1-2 INCHES OF
SNOW ACCUM ON THE NORTHERN FRINGE OF RAIN/SLEET TRANSITION TO SNOW
BAND FROM WILLIAMSBURG TO CLINTON IA BY MID TUE EVENING. THEN IN-
WRAPPING MID LEVEL DRYING SHOULD SWITCH ALMOST ALL THE PRECIP TO
MAINLY DRIZZLE OR FREEZING DRIZZLE FROM MID EVENING THROUGH 12 AM-1
AM CST. AREAS OF TEMPORARY DENSE FOG POSSIBLE TOO BUT WILL LEAVE
OUT MENTION AT THIS POINT. THEN WITH THE APPROACH OF THE MID LEVEL
LOW AFTER MIDNIGHT...THE FCST SOUNDINGS SATURATE DEEPER AGAIN AND
SUPPORT A BAND OF SECONDARY DEF ZONE RAINS CLIPPING THE SOUTHEAST
THIRD OF THE CWA INTO EARLY WED MORNING WITH UP TO .3 OR .4 INCHES OF
RAIN POSSIBLE BY 8 AM CST WED. THE WESTERN FRINGE OF THIS DEF ZONE
RAIN MAY MIX WITH SNOW BY WED MORNING WITH LIGHT SLUSHY SNOW ACCUMS
UP TO AN INCH. FURTHER NORTH AND WEST OVER THE REST OF THE CWA...
LIGHT DRIZZLE OR FREEZING DRIZZLE DEPENDING ON THE SFC TEMPS WILL
LOOK TO TOP-DOWN COOL AND SATURATE INTO ALL LIGHT SNOW PARAMETERS
AFTER 1 AM WITH LIGHT ADDITIONAL SNOW ACCUMS POSSIBLE UP TO AN INCH
BY WED MORNING WHEN THE PRECIP WILL BE ON THE MOVE OUT OF THE LOCAL
FCST AREA. WILL STILL HAVE TO BE WARY OF SOME BANDED SNOWS OF AT
LEAST 1-2 INCHES AS THE UPPER LOW APPROACHES LATE TUE NIGHT IF
DYNAMICAL/TOP DOWN COOLING OCCURS QUICKER THAN CURRENTLY ANTICIPATED.
THERE STILL MAY BE A NEED FOR A WINTER WEATHER ADVISORY TUE NIGHT FOR
THE ROUNDS OF LIGHT FREEZING RAIN...FREEZING DRIZZLE...SNOW AND SLEET
MIX WITH AREAS ALONG AND NORTH OF I80 THE MOST LIKELY TARGET. THE
REST OF WED AND WED NIGHT SHOULD HAVE NO REAL WX MAKERS AND BE QUIET.
THURSDAY THROUGH FRIDAY...DEPENDING ON WHAT LIES IN THE WAKE OF THE
MID WEEK SYSTEM STREAM FLOW AND BAROCLINICITY-WISE...A RE-LOADING
SOUTHWESTERN CONUS TROF AND ACTIVE NORTHERN STREAM ACRS THE WEST
HALF OF THE CONUS HAVE ALL THE MEDIUM RANGE MODELS A FLUTTER THIS
PERIOD. MUCH UNCERTAINTY OF COURSE...BUT SIGNALS OF SOUTH-WESTERLIES
IN THE SOUTHERN STREAM REORGANIZING SOUTH AND SOUTHWEST OF THE
LOCAL AREA JUST SOUTH OF CONFLUENT FLOW MAY ALLOW SOME ELEVATED
FRONTOGENETICAL FORCING ALONG AND BEHIND A LLVL FRONT GETTING
ALIGNED PARALLEL TO THIS MEAN FLOW TO GENERATE SOME LIGHT SNOW OR
FLURRIES ACRS THE CWA EITHER LATE THU OR THU NIGHT INTO FRI
MORNING. AT THIS POINT WITH THE DRY LOOKING VERTICAL PROFILES...JUST
A DUSTING TO UNDER AN INCH WOULD ALL THAT WOULD BE POSSIBLE BY FRI
MORNING AND MAINLY FROM IOWA CITY TO FREEPORT IL AND NORTHWARD.
THE 12Z RUN UKMET...GEM AN GFS ARE EITHER DRY OR JUST HAVE FLURRIES
FOR THU NIGHT. LONGER RANGE SIGNALS SUGGEST PHASING ISSUES A PLENTY
AS THE DIGGING NORTHERN STREAM UPPER TROF OVER CENTRAL CANADA TRIES
TO INTERACT WITH THE SOUTHWEST PLAINS TROFFINESS. THE MAJORITY OF
THE LONGER RANGE MODELS HANDLE THIS PROCESS IN A WAY THAT ANY
SOUTHERN STREAM WX MAKER AND IT/S ASSOCIATED PRECIP REMAINS ALONG
OR SOUTH OF THE DVN CWA FROM FRI INTO SAT. BUT THE 12Z GFS MUCH
MORE OMINOUS AND DEVELOPED UPSTREAM. IT PHASES THE STREAMS IN A WAY
THAT A STORM SYSTEM WITH AT LEAST HIGHER END ADVISORY SNOWS/2-5+
INCHES IMPACTS THE ENTIRE CWA FRI NIGHT INTO SAT MORNING. WILL WATCH
FURTHER TRENDS OF COURSE WITH ADDITIONAL RUNS OVER THE NEXT 24-48
HRS. WILL GO WITH SEASONABLE TEMPS FOR THU THROUGH FRI FOR NOW.
SATURDAY THROUGH MONDAY...ENSEMBLES AND TELECONNECTIONS OVER THE
HOLIDAY WEEKEND SUGGEST SOME AO/ARCTIC OSCILLATION INFLUENCE AS
GENERAL L/W TROFFINESS TRIES TO ESTABLISH THIS PERIOD AND INTO EARLY
NEXT WEEK ACRS THE UPPER MIDWEST AND GRT LKS. THIS PERIOD ALSO LOOKS
GENERALLY DRY AFTER SAT WITH SOME RE-ENFORCING COOL SHOTS OUT OF
CANADA POSSIBLE FOR SEASONABLE OR SOMEWHAT BELOW TEMPS INTO NEXT
MONDAY. CAN/T RULE OUT SOME FLURRIES ON LEADING EDGES OF COOL DUMPS
OR WEAK WAVES EMBEDDED IN NORTHWESTERLY CYCLONIC FLOW...BUT WILL GO
MAINLY DRY FOR NOW. ..12..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS TOPEKA KS
525 PM CST MON DEC 19 2011
...UPDATE TO AVIATION...
.DISCUSSION...
THE FOCUS OF THIS FORECAST REMAINS ON THE POTENT STORM SYSTEM WHICH
WILL MOVE OFF THE HIGH PLAINS AND BRING RAIN AND SNOW TO ALL OF
NORTHEAST AND EAST CENTRAL KANSAS TONIGHT AND TOMORROW.
20Z WATER VAPOR IMAGERY AND ASSOCIATED RUC ANALYSIS SHOWING THE 500
MB TROUGH MAKING A NORTHEAST TURN AS IT TAKES ON A NEGATIVE TILT
OVER FAR WESTERN TEXAS. STRONG ISENTROPIC LIFT CAUSING A WIDE SHIELD
OF PRECIPITATION MAINLY IN THE FORM OF RAIN TO MOVE NORTHWARD ACROSS
THE AREA. SOME ELEVATED INSTABILITY HAS ALLOWED FOR SOME WEAK
CONVECTION WITHIN THE AREA OF PRECIP ALLOWING FOR A FEW RUMBLES OF
THUNDER. WITH WARM LOW LEVEL TEMPERATURES ACROSS FAR EASTERN KANSAS
THE PRECIPITATION HAS FALLEN AS RAIN THROUGHOUT THE DAY. FURTHER TO
THE WEST COOLER AIR IN THE LOWER TO MID LEVELS HAS FACILITATED A
GRADUAL CHANGE OVER TO A MIX OF RAIN AND SNOW WITH SOME SLEET.
ACROSS CENTRAL AND SOUTHWEST KANSAS WHERE THE COLD AIR IS EVEN
DEEPER PRECIP HAS CHANGED COMPLETELY OVER TO SNOW. THE AREA WITH THE
BIGGEST CONCERN FOR THIS SYSTEM WILL BE ACROSS CENTRAL AND NORTH
CENTRAL KANSAS WHERE SNOW AMOUNTS COULD BE THE HIGHEST. BEST
FRONTOGENETICAL LIFT AND ASSOCIATED HIGHEST OMEGA LOOKS TO PERSIST
ACROSS THE AREA BETWEEN 00Z AND 12Z TONIGHT...AND THIS WILL LIKELY
BRING THE HEAVIEST SNOW...ESPECIALLY TO AREAS OF CENTRAL KANSAS.
GOOD LIFT THROUGH THE -8 TO -14 C DENDRITIC GROWTH LAYER WILL LIKELY
KEEP ALL PRECIP WEST AND NORTH OF A HIAWATHA TO COUNCIL GROVE LINE.
SNOW COULD RAPIDLY INCREASE WITH SNOW RATES APPROACHING 3 TO 5
INCHES OVER A 6 TO 10 HOUR PERIOD ACROSS THAT AREA. COMPLICATING THE
CONDITIONS WILL BE STRONG WINDS ACROSS CENTRAL KANSAS
OVERNIGHT...LEADING TO REDUCED VISIBILITIES AND DANGEROUS TRAVEL
CONDITIONS...ESPECIALLY ALONG INTERSTATE 70. VERY TRICKY PRECIP TYPE
FORECAST FOR AREAS ALONG AND EAST OF THE KANSAS TURNPIKE. FORECAST
SOUNDINGS INDICATE ICE CRYSTALS INTRODUCED INTO THE ATMOSPHERIC
COLUMN...BUT WARMER 850 MB TEMPS COULD TEMPER THE ABILITY OF SNOW TO
REACH THE SURFACE. HOWEVER WITH REAL TIME TEMPS RUNNING A BIT COOLER
THAN MODEL TEMPS...MAY NEED TO CALIBRATE MODELS WITH REAL TIME INFO
AND LEAN TOWARD A SLIGHTLY COOLER SOLUTION...FOR PRECIP TYPES AND
SNOW AMOUNTS ACROSS THE EASTERN COUNTIES. SHOULD PRECIP BE ABLE TO
CHANGE OVER TO SNOW BY 01 TO 03Z EAST OF THE AFOREMENTIONED HIAWATHA
TO COUNCIL GROVE LINE...MAY NEED TO BUMP UP SNOW
AMOUNTS...ESPECIALLY FOR THE TOPEKA AREA. AROUND 12Z TUESDAY MORNING
DRY MID LEVEL AIR WILL PUSH INTO THE AREA WHICH WILL REMOVE ICE
CRYSTALS FROM THE COLUMN FOR A FEW HOURS TUESDAY MORNING. DURING
THIS TIME EXPECT PRECIP TO GO FROM A LIGHT SNOW TO A LIGHT DRIZZLE
OR FREEZING DRIZZLE ACROSS AREAS WHERE TEMPS ARE BELOW FREEZING. BY
LATE TUESDAY AFTERNOON THE MID LEVEL TROWAL WILL SET UP NEAR THE
INTERSTATE 70 CORRIDOR WHICH COULD BRING ANOTHER ROUND OF LIGHT SNOW
FOR TUESDAY AFTERNOON AS THE ATMOSPHERIC COLUMN SHOULD BE COOL
ENOUGH ACROSS THE ENTIRE FORECAST AREA.
WILL NOT MAKE ANY MAJOR CHANGES TO THE ONGOING WARNING/ADVISORY
LOCATIONS AS COUNTIES CURRENTLY UNDER THE WINTER STORM WARNING ARE
STILL ON TRACK TO ACCUMULATE 6 TO 8 INCHES OF SNOW. THE COUNTIES
FURTHEST NORTH AND EAST CONTAIN LESSER CONFIDENCE IN REACHING THE 6
TO 8 INCH RANGE...BUT COUNTIES ALONG INTERSTATE 70 AND WEST OF THE
KANSAS TURNPIKE SHOULD EXPECT AT LEAST 4 TO 6 INCHES OF SNOW...WITH
HIGHER AMOUNTS ACROSS CENTRAL KANSAS. ALSO STRONG WINDS ALONG
INTERSTATE 70 WILL COMPLICATE TRAVEL CONDITIONS AS THEY WILL
COINCIDE WITH THE HEAVY SNOW OVERNIGHT TO BRING LOWERED VISIBILITY
AND DANGEROUS TRAVEL CONDITIONS.
EXPECT LIGHT SNOW TO GRADUALLY COME TO AN END BY EARLY WEDNESDAY
MORNING AS THE UPPER TROUGH EXITS COMPLETELY OUT OF THE AREA WITH
CLEARING SKIES AND SEASONABLE TEMPS.
ANOTHER SYSTEM SWINGS INTO THE PLAINS THURSDAY INTO FRIDAY BUT
WITH A NORTHERLY TRAJECTORY AND MORE LIMITED MOISTURE WILL CARRY
CHANCE TO SLIGHT CHANCE POPS AT THIS TIME. CONDITIONS CLEAR OUT
FOR SATURDAY WITH ANOTHER PUSH OF COLDER AIR SATURDAY NIGHT INTO
SUNDAY.
&&
.AVIATION...
MVFR TO IFR CONDITIONS ARE EXPECTED TO BECOME IFR BETWEEN 00-03Z
AND PERSIST THROUGH MUCH OF THE FORECAST PERIOD. MHK HAS SWITCHED
TO ALL SNOW...WITH RAIN AT TOP/FOE. EXPECT WINTRY MIX OF
PRECIPITATION AT TOP/FOE BY 04Z...WITH ALL TAF SITES IMPACTED WITH
WINTRY TYPE OF PRECIP THROUGH MUCH OF THE PERIOD.
BLAIR
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM CST TUESDAY FOR KSZ009>011-
020>023-034>036.
WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR KSZ008-012-
024-026-037>039.
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM CST
TUESDAY FOR KSZ040-054-055.
&&
$$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
506 PM CST MON DEC 19 2011
.AVIATION...
FOR THE 00Z TAF ISSUANCE...CIGS WILL REMAIN LIFR/IFR IN ASSOCIATION
WITH SN/BLSN. CIGS WILL EVENTUALLY IMPROVE TO MVFR TOWARDS 18Z TOMORROW.
WINDS WILL REMAIN STRONG AROUND 30 KT TONIGHT AND THEN ABATE IN THE
20-25 KT BY MORNING. -SUGDEN
&&
.PREV DISCUSSION... /ISSUED 320 PM CST MON DEC 19 2011/
SYNOPSIS...
THE OVERALL SYNOPSIS FROM THE 12Z...250MB CHART SHOWED A 80-KNOT
JET STREAK OF WIND FROM SOUTHWEST TEXAS THROUGH SOUTHWEST KANSAS
TO SOUTHERN IOWA. A STRONGER 110KT NORTHWEST JET WAS ENTERING BAJA
CALIFORNIA (W. MEXICO), WHILE A 120-KNOT JET STRETCHED FROM
NORTHERN MINNESOTA TO SOUTHWEST QUEBEC. THE 500MB CHART AT 12Z HAD
A LARGE UPPER LOW PRESSURE SYSTEM OVER EXTREME WESTERN TEXAS, WITH
MOISTURE FLOWING NORTHEASTWARD INTO KANSAS. THE 500MB TEMPERATURE
AT DDC WAS AT 17C. THE 700 MB CHART LOOKED SIMILAR TO THE 500MB
CHART PATTERN, BUT WITH THE H7 LOW PRESSURE OVER SOUTH CENTRAL NEW
MEXICO. A COLD FRONT WAS EVIDENT AT 12Z AT THE 850MB LEVEL ACROSS
NORTH CENTRAL KANSAS, WITH LBF AT -04C AND DDC AT +10C.
DISCUSSION...
DAYS 1-2...
THE UPPER STORM SYSTEM MOVING ACROSS NEW MEXICO AND TEXAS, AND
INTO NORTHERN OKLAHOMA, WAS BRINGING WINTER-LIKE WEATHER TO MOST
OF SOUTHWESTERN KANSAS THIS AFTERNOON. THERE WAS A BAND OF RAIN,
SOME MODERATE, THAT MOVED NORTH FROM FROM OKLAHOMA MORNING LAID
DOWN 0.02 TO 0.50 INCH OF RAIN ACROSS MUCH OF OUR SOUTHERN CWA.
THIS SOAKED UPPER LAYER OF SURFACE GROUND WILL DELAY TO ONSET OF
ACCUMULATING SNOW, BUT SNOW RATES OF .5 TO 1.0-INCH PER HOUR AT
TIMES WILL LEAD TO A QUICK ACCUMULATION. FURTHERMORE, PER THE
FORECAST SOUNDINGS FROM THE NAM AND RUC MODELS BOTH SHOWED A WARM
ELEVATED LAYER OF +2 DEGREES, INDICATING THERE MAY BE SOME SLEET
OR LIGHT FREEZING RAIN BEFORE THE EASTERN PART OF THE CWA CHANGES
TO ALL SNOW, SO WILL MENTION THAT. A SURFACE COLD FRONT WAS
WORKING SOUTH THROUGH THE CWA TODAY, AND CLEARED THE SOUTHEAST
PART OF OUR FORECAST AREA BETWEEN 20 AND 21Z. WHERE THE
OVERRIDING COLD AIR WILL MEET THE BEST LIFT OVER THE ELEVATED
FRONT IS WHERE A HEAVY BAND OF SNOW SHOULD SET UP...FROM
APPROXIMATELY LAKIN TO GARDEN CITY TO NESS CITY...WHERE 10 TO 11
INCHES OF SNOW IS POSSIBLE BY TUESDAY AFTERNOON. SOUTHEAST OF THAT
ZONE, IN THE LIBERAL TO DODGE CITY TO KINSLEY TO SAINT JOHN ZONE...I
STILL THINK THERE COULD BE SOME BANDS OF HEAVY SNOW TONIGHT...WITH
LESS DURATION THAN NORTH OF THERE, AND 5 TO 8 INCHES OF SNOW IS
EXPECTED THERE BY TUESDAY AFTERNOON. IN BOTH THESE ZONES...STRONG
NORTH WINDS OF 20 TO 35 MPH WITH GUSTS TO NEAR 45 MPH WILL COMBINE
WITH THE SNOW TO CREATE LOW VISIBILITIES IN BLOWING AND DRIFTING
SNOW. WITH A FEW AREAS IN OUR EXTREME WEST SUCH AS TRB AND 3K3
ALREADY REPORTING M1/4SM +SN...THINK THIS COLD AIR AND STRONG
WINDS WILL WRAP TO THE EAST TONIGHT. THEREFORE, THE BLIZZARD
WARNING WILL CONTINUE THROUGH NOON TUESDAY, NORTHWEST OF A LINE
FROM COLDWATER TO PRATT. A WINTER WEATHER ADVISORY FOR 3 TO 5
INCHES OF SNOW AND BLOWING SNOW WILL ALSO CONTINUE THROUGH NOON
TUESDAY FOR PRATT, BARBER AND COMANCHE COUNTIES.
AS FOR TEMPS, THINK OVERNIGHT THAT LOWER DEW POINTS WILL BE
FILTERING IN FROM THE NORTH ON THE STRONG FLOW. STAYED PRETTY
CLOSE TO THE PREVIOUS FORECAST OF MIN T`S FROM AROUND 17F IN EHA
TO 23F IN P28. TOMORROW WILL SEE THICK CLOUDS AROUND ALONG WITH
EARLY SNOW. THE TEMPERATURE WILL NOT RISE MUCH AND SHOULD TOP OUT
IN THE 27F TO 30F DEGREE RANGE. CLOUDS WILL CLEAR OUT FROM WEST TO
EAST TUESDAY EVENING, AND WITH FRESH SNOW COVER EXPECTED AND LIGHT
WEST WINDS, THE TEMPERATURE SHOULD PLUMMET. LOWS TUESDAY NIGHT
WILL BE QUITE COLD, RANGING FROM A VERY COLD 5F IN EHA TO 14F IN
P28. WEDNESDAY, WE WILL STILL BE IN THE GRIP OF COLD ARCTIC AIR
CENTERED TO OUR NORTHEAST, BUT NOT MUCH WARMER THAN TUESDAY IN
MOST SPOTS. HAVE WENT WITH A MAX T FORECAST FOR WEDNESDAY IN THE
27F DEGREE RANGE NEAR LBL, EHA, GCK AND DDC, RANGING UP TO 33F AT P28.
DAYS 3-7...
A NORTHERN BRANCH SHORTWAVE TROUGH WILL DIG TO NEAR THE FOUR CORNERS
ON THURSDAY WITH SOME LIGHT SNOW EXPECTED MOSTLY IN THE AFTERNOON
ACROSS WESTERN KANSAS. THE TROUGH THEN WILL MOVE INTO THE PLAINS ON
FRIDAY WITH LIGHT SNOW ENDING FROM WEST TO EAST ON FRIDAY MORNING.
EXPECT LESS THAN AN INCH ACCUMULATION. ANOTHER LONGER WAVE TROUGH
WILL MOVE ACROSS THE CENTRAL CONUS ON SUNDAY WITH MAINLY DRY
CONDITIONS AND LESS MOISTURE TO WORK WITH. THE GFS AND NEW ECMWF ARE
DIFFERENT WITH ONE SHOWING A SHORTWAVE RIDGE AND THE OTHER A
SHORTWAVE TROUGH BUT LOOKS TO DRY FOR ANY PRECIPITATION.
A COLD FRONT WILL MOVE INTO THE CENTRAL PLAINS WITH HIGH PRESSURE
AND LOWS IN THE TEENS TO LOW 20S ON THURSDAY MORNING AND HIGHS FROM
THE UPPER 20S NORTH TO AROUND 34 SOUTHEAST FA ON THURSDAY. A RIDGE
OF COLD HIGH PRESSURE MOVES INTO THE PLAINS ON FRIDAY WITH LOWS IN
THE TEENS AND HIGHS ONLY IN THE MID 20S. SATURDAY MORNING LOOKS THE
COLDEST WITH LIGHT WINDS AND LOWS IN THE SINGLE DIGITS. FOR SATURDAY
HIGHS SHOULD BE AROUND 30 TO 35. ON CHRISTMAS DAY SUNDAY MORNING
LOWS WILL BE MAINLY IN THE TEENS AND HIGHS AROUND 30 TO 35 WITH
MOSTLY CLEAR SKIES. ON MONDAY MORNING LOWS WILL BE COLD AGAIN WITH
CLEAR SKIES AROUND 10 TO 15 DEGREES AND HIGHS MONDAY WITH WARMING
SOUTHWEST WINDS AND HIGHS FROM THE MID 30S TO LOWER 40S.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 20 27 9 27 / 100 80 0 0
GCK 19 28 6 27 / 100 70 0 0
EHA 17 28 5 27 / 100 60 0 0
LBL 20 28 6 27 / 100 60 0 0
HYS 23 29 6 28 / 100 100 0 0
P28 26 30 14 36 / 100 90 10 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WARNING UNTIL NOON CST /11 AM MST/ TUESDAY FOR KSZ030-
031-043>046-061>066-074>080-084>088.
WINTER WEATHER ADVISORY UNTIL NOON CST TUESDAY FOR KSZ081-089-
090.
&&
$$
FN36/36/36
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
140 AM EST SUN DEC 18 2011
.SYNOPSIS...
SNOW SHOWERS WILL SLOWLY END AS WEAK LOW PRESSURE ALOFT EXITS
SUNDAY MORNING. A SLOWING MIDWEST COLD FRONT WILL PROVIDE RAIN
MONDAY AFTERNOON INTO WEDNESDAY WITH PERHAPS A CHANCE OF SNOW
TUESDAY MORNING.
&&
.NEAR TERM /THROUGH TODAY/...
MADE SLIGHT ADJUSTMENTS TO TEMPERATURES, POPS, AND WINDS
OVERNIGHT. RECENT IR SATELITE IMAGERY SHOWS CLOUD TOPS COOLING
AND RADAR SCANS HAVE INDICATED SOME SLIGHTLY STRONGER SNOW BANDS
SO THINK THAT IT IS REASONABLE THAT AT LEAST A FEW TENTHS OF AN
INCH MORE CAN BE EXPECTED...UP TO A HALF INCH THROUGH SUNDAY
MORNING AND AN INCH OR SO OVER THE RIDGES. STILL THINK SNOW SHOULD
END SUNDAY MORNING WITH SUFFICIENT LIFT, AND MOISTURE PUSHING OFF
TO THE EAST. IN ADDITION, THE MORE WESTERLY WIND DIRECTION ALOFT
MAKES LAKE EFFECT ENHANCEMENT UNLIKELY.
850HPA RIDGE IS CURRENTLY OVER THE OHIO VALLEY WITH SOME WAA
KEEPING TEMPERATURES RELATIVELY STEADY THROUGH THE NIGHT, SO MADE
TEMPERATURE ADJUSTMENTS OVERNIGHT AND SUNDAY.
PREVIOUS DISCUSSION FOLLOWS...
PER RECENT SURFACE AND RADAR DATA, COUPLED WITH HRRR AND NAM MODEL
OUTPUT, EXPECT EXITING WEAK LOW PRESSURE ALOFT TO CAUSE LIGHT SNOW
SHOWERS TO SLOWLY END WEST TO EAST OVERNIGHT INTO SUNDAY MORNING.
MOST PLACES WILL GET LITTLE IF ANY ADDED SNOW ACCUMULATION, WITH
PERHAPS UP TO AN INCH ACROSS THE MOUNTAINS.
THE ONLY APPARENT HAZARD AT THIS TIME IS LINGERING BLACK ICE ON
UNTREATED PAVEMENTS.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY/...
DRY AND COOL SUNDAY NIGHT INTO EARLY MONDAY AS SURFACE RIDGE MOVES
OFF THE SOUTHEAST ATLANTIC COAST. BY MONDAY AFTERNOON A COLD FRONT WILL
MOVE INTO NORTHWEST PENNSYLVANIA AND CROSS THE REGION MONDAY
NIGHT. THE FRONT WILL STALL OVER NORTHERN WEST VIRGINIA BEFORE
MOVING NORTHWARD TUESDAY AS DEVELOPING LOW PRESSURE MOVES
NORTHEAST OUT OF TEXAS.
MODELS ARE NOW IN GOOD AGREEMENT ON ENOUGH COLD AIR BEHIND FRONT
FOR RAIN TO MIX WITH SNOW FROM PITTSBURGH SOUTH LATER MONDAY NIGHT
INTO TUESDAY MORNING WITH A PERIOD OF ALL SNOW FROM PITTSBURGH
NORTH AS 1000-850MB THICKNESS FALLS BELOW CRITICAL VALUES. BULK OF
PRECIPITATION STILL LOOKS TO BE RAIN AND SNOW ACCUMULATION LOOKS
TO BE LIMITED AS DEEPER MOISTURE WILL BE IN A FAIRLY NARROW BAND
ALONG AND JUST BEHIND THE FRONT. POPS WERE KEPT HIGH CHANCE TO LOW
LIKELY AS EXACT PLACEMENT OF WHERE BOUNDARY STALLS MONDAY NIGHT
WILL DETERMINE WHERE HIGHEST QPF WILL BE. TEMPERATURES TRENDED A
BIT LOWER ON AVERAGE WITH BETTER PUSH OF COLD AIR NOW EXPECTED.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
THE FORECAST PERIOD BEGINS WITH REASONABLE GFSE/ECMWF/CANADIAN
AGREEMENT THAT THE CUT OFF LOW OFF OF CALIFORNIA WILL EJECT INTO THE
CENTRAL PLAINS BY TUESDAY NIGHT AND PUSH INTO THE UPPER OHIO VALLEY
AS A TROUGH BY WEDNESDAY NIGHT. A FRONTAL BOUNDARY IN THE VICINITY
OF THE AREA ALONG WITH A MID-LEVEL SOUTHWESTERLY FLOW AHEAD OF THIS
SYSTEM WILL ALLOW FOR LIKELY POPS TUESDAY NIGHT INTO EARLY
WEDNESDAY. HIGH CHANCE POPS ARE FORECAST WEDNESDAY AS THE TROUGH
CROSSES THE AREA. GFS/ECMWF INDICATE CRITICAL THICKNESS LINES FOR
WINTRY PRECIP WILL BE WELL NORTH OF THE AREA AND THUS THE FORECAST
IS PREDOMINATELY IN THE FORM OF RAIN UNTIL THE TROUGH SHIFTS EAST
AND ADVECTS COLD AIR IN BEHIND IT. ON THE BACK SIDE OF THE TROUGH, A
MIX OF RAIN AND SNOW SHOWERS ARE FORECAST WEDNESDAY NIGHT BEFORE
PRECIPITATION COMES TO AN END.
THE TROUGH WILL SHIFT WELL EAST OF THE AREA WITH A DRY FORECAST FOR
THURSDAY. GFSE/ECMWF SOLUTIONS ARE HINTING AT A LOW PRESSURE SYSTEM
CLIPPING THE AREA AS IT PASSES TO THE SOUTHEAST ON FRIDAY. THUS HAVE
CHANCE POPS SOUTH OF PITTSBURGH. AFTER THIS POINT, FORECAST IS
CLOSEST TO THE ECMWF WITH ANOTHER TROUGH PASSING THROUGH AND SCHC
POPS FOR SATURDAY. TEMPERATURES WILL BE AROUND 5 DEGREES ABOVE
NORMAL UNTIL SATURDAY WHEN A CANADIAN HIGH USHERS COLDER AIR INTO
THE REGION AND BRINGS TEMPS CLOSER TO SEASONAL NORMALS.
&&
.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
EXPECT AREAS OF MAINLY MVFR SNOW SHOWERS WITH SPOTTY IFR
RESTRICTIONS TO DECREASE IN COVERAGE EARLY THIS MORNING AS AN UPPER
TROUGH MOVES THROUGH. PREVAILING STRATOCUMULUS BASES WILL LIKELY
FLUCTUATE BETWEEN MVFR AND VFR AND THEN BECOME MAINLY VFR BY MIDDAY
SUNDAY.
OUTLOOK...SUNDAY NIGHT THROUGH THURSDAY...
HIGH PRESSURE WILL MAINTAIN VFR CONDITIONS SUNDAY NIGHT INTO
MONDAY. THE NEXT LOW PRESSURE SYSTEM WILL APPROACH FROM THE
SOUTHWEST MONDAY NIGHT, RETURNING THE CHANCE OF SHOWERS WITH
RESTRICTIONS THROUGH THURSDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
103 PM EST SUN DEC 18 2011
UPDATED AVIATION DISCUSSION FOR 18Z TAFS
.DISCUSSION /TODAY THROUGH SATURDAY/... ISSUED AT 431 AM EST
QUIET MORNING ACROSS UPPER MICHIGAN...AS SFC RIDGE IS SLIDING ACROSS
THE UPPER GREAT LKS REGION. PERSISTENT AREA OF LOW CLOUDS EARLY THIS
MORNING ON SATELLITE...STRETCHING SW INTO NRN WI. MOST MODELS HAVING
A DIFFICULT TIME WITH THEM...BUT RUC SEEMS TO HAVE A DECENT HANDLE
ON LOW CLOUDS ON 0.5-1KM RH FIELDS...SO HAVE FOLLOWED THAT FOR THE
EXIT OF THE MVFR CLOUDS THIS MORNING. THINK THEY WILL LIKELY PERSIST
THROUGH THE FIRST PART OF THE MORNING UNTIL LLVL WINDS SHIFT TO THE
SW AND PUSH THEM NE OF THE AREA.
1002MB LOW PRESSURE SYSTEM CURRENTLY LOCATED JUST NW OF LK WINNIPEG
WILL SLOWLY DEEPEN THROUGH THE DAY...AS A NRN STREAM SHORTWAVE
AMPLIFIES OVER SOUTHERN CANADA THROUGH THE DAY. BY 00Z...SHOULD SEE
A 999MB LOW LOCATED JUST TO THE N OF LK SUPERIOR. STRONG H850-500
WAA OVER SRN CANADA /AND PRODUCING A FEW -SHSN E OF LK WINNIPEG/
WILL SHIFT ESE THROUGH SRN ONTARIO AND FAR NRN LK SUPERIOR FROM MID
MORNING THROUGH THE REST OF THE DAY. WITH THE BEST MOISTURE LOCATED
IN THIS AREA...EXPECT THE PCPN TO STAY N OF THE LAND AREAS. HEADING
FARTHER S OVER UPPER MI...DRY AIR BELOW H750 SHOULD KEEP ANY PCPN
COMING OUT OF THE MID CLOUDS FROM REACHING THE SFC FROM MID MORNING
THROUGH EARLY AFTN. LIKELY WON/T SEE MUCH SUN THROUGH THE MORNING
HOURS WITH THE LINGERING LLVL CLOUDS THAT WILL BE OVERRUN BY THE
INCOMING MID CLOUDS. DRY SLOT BEGINS TO MOVE OVER THE AREA AROUND
MID AFTN AND MAY LEAD TO SOME CLEARING...ESPECIALLY OVER THE W HALF.
WITH THE LOW INTENSIFYING AS IT MOVES N OF THE AREA...WILL LIKELY
SEE SOME GUSTY SW WINDS THIS AFTN. STRENGTHENING INVERSION AROUND
H900 WILL LIMIT ACCESS TO THE LLVL JET AROUND 45KTS. BUT TIGHTENING
PRESS GRADIENT WILL STILL LEAD TO GUSTS IN THE 20-30KT
RANGE...ESPECIALLY IN THE SW WIND DOWNSLOPE AREAS NEAR LK SUPERIOR.
THE INVERSION AND CLEARING THIS AFTN MAKES TEMPS TRICKY...AS THERE
WILL BE A LIMITED PERIOD FOR SUNSHINE HELP MIX HIGHER ALOFT. THOUGH
PREVIOUS HIGHS LOOKED GOOD AND ONLY MADE MINOR TWEAKS. WITH THE WARM
START AND SSWRLY FLOW...EXPECT THE HIGHS TO BE IN THE UPPER 30S AND
MAYBE AN ISOLATED 40 OVER THE WRN CWA /WHERE WARMER AIR SURGES INTO
THE AREA AND THERE IS A LONGER PERIOD OF CLEAR SKIES/...ALONG WITH
DOWNSLOPE AREAS NEAR LK SUPERIOR.
SFC LOW WILL QUICKLY DEEPEN TO 993MB THROUGH THE NIGHT AS IT SHIFTS
JUST SE OF JAMES BAY BY 12Z. DRY SLOT WILL STILL BE OVER THE AREA
AND PROVIDE A CLEAR BUT BREEZY EVENING. SFC TROUGH/COLD FRONT WILL
THEN SLIDE SE THROUGH THE CWA AFTER MIDNIGHT AND BRING A CHANCE FOR
PCPN TO AREAS NEAR LK SUPERIOR. NOT OVERLY IMPRESSED WITH
FORCING/MOISTURE ALONG THE FRONT...SO HAVE WENT WITH SLIGHT
CHANCES...EXCEPT FOR FAVORABLE UPSLOPE NW WIND LOCATIONS OVER THE
WRN CWA. P-TYPE WILL BE SNOW INITIALLY WITH THE PASSAGE OF THE
FRONT...BUT COULD BE SOME FZDZ WITH THE UPSLOPE FLOW OVER THE WRN
U.P. SOUNDINGS SHOW INCREASING LLVL LAPSE RATES OVER THE WEST AFTER
06Z TONIGHT BELOW THE 3-4KFT INVERSION. WITH NEAR SFC DRY AIR
PUTTING CLOUD BASES AROUND 1.5-2.5KFT...OVERALL CLOUD DEPTH WILL BE
FAIRLY SHALLOW. IN ADDITION...CLOUD TOPS ARE ONLY AROUND -7 TO -8C
AFTER THE FRONT MOVES THROUGH...LIMITING ICE CRYSTALS IN THE CLOUDS.
THEREFORE...HAVE ADDED A MENTION OF FZDZ OVER THE W AFTER 09Z. OVER
THE E...WARMER TEMPS WILL LIKELY LEAD TO MORE OF A DZ/SN POTENTIAL
LATE TONIGHT.
WITH CONTINUED H925-850 MOISTURE AND H850 TEMPS FALLING TOWARDS -10C
BY MID MORNING...EXPECT A PERIOD OF LK ENHANCED PCPN DURING THE
MORNING HOURS. TEMPS SHOULD FALL ENOUGH MON MORN OVER THE W TO
PRODUCE ENOUGH ICE CRYSTALS FOR ANY LINGERING SHOWERS TO BE ALL
SNOW. THERE COULD BE A SLIGHT LAG OVER THE E NEAR LK SUPERIOR FOR
THE FIRST COUPLE OF HOURS AND MENTIONED A -SHSN/FZDZ INITIALLY IN
THE MORNING. LAKE EFFECT POTENTIAL QUICKLY DIMINISHES HEADING INTO
THE AFTN...AS H850-700 SUBSIDENCE INCREASES AND LLVL MOISTURE
DEPARTS. IN ADDITION...MODELS SHOWING INVERSION HEIGHTS AT OR BELOW
3KFT IN THE AFTN AND LOCAL/NATIONAL HIRES WRF RUNS NOT SHOWING ANY
PCPN. WITH ALL THE NEGATIVES...HAVE TAPERED BACK EXISTING POPS IN
THE AFTN...BUT DID LEAVE SOME LOW CHANCES OVER THE E FOR NNW WIND
FAVORED LOCATIONS WHERE THE LONGER FETCH MAY HELP KEEP PCPN GOING.
HIGH PRESSURE RIDGE WILL BUILD OVER THE AREA ON MON NIGHT...BRINGING
AN END TO ANY LINGERING LES EARLY IN THE EVENING. WITH LIGHT WINDS
AND CLEAR SKIES UNDER THE HIGH PRESSURE RIDGE...EXPECT A GOOD
RADIATIONAL COOLING NIGHT. PWAT VALUES /AROUND 0.1 INCH OR 35
PERCENT OF NORMAL/ SUPPORT GOING ON THE LOW END OF GUIDANCE...AND
HAVE LOWS FALLING INTO THE SINGLE DIGITS ABOVE ZERO.
NRN STREAM OF THE JET WILL REMAIN N OF THE AREA FOR TUES/WED...WHILE
THE SRN STREAM IS LOCATED OVER THE SRN CONUS. THIS LEAVES THE AREA
WITH FAIRLY QUIET AND SEASONABLE CONDITIONS. SFC RIDGE WILL BE OVER
THE CWA AT THE START OF TUES...WITH ANOTHER SHORTWAVE MOVING THROUGH
SRN CANADA IN THE NRN STREAM. AS WITH THE SYSTEM TODAY...MAIN
ENERGY/MOISTURE WILL BE JUST TO THE N OF THE AREA...BRUSHING NRN LK
SUPERIOR. AS THIS QUICKLY MOVES E TUES EVENING...WEAK SFC RIDGE WILL
LIKELY BUILD BACK OVER THE AREA FOR TUES NIGHT INTO WED MORNING.
SEASONABLE TEMPS WILL CONTINUE...ALTHOUGH THE GUSTY WINDS AT TIMES
WILL MAKE IT FEEL A LITTLE COOLER.
DIFFERENCES START TO APPEAR IN THE EXTENDED MODELS WED INTO THURS
NIGHT WITH THE HANDLING OF THE EASTWARD MOVING UPPER LOW IN THE SRN
STREAM THAT WILL BE OVER THE CNTRL ROCKIES ON WED. ANOTHER NRN
STREAM TROUGH WILL BE DROPPING THROUGH THE CANADIAN ROCKIES AT THIS
TIME AND THEY WILL TRY TO MERGE THE NRN/SRN STREAMS OVER THE GREAT
LAKES REGION. 00Z RUNS OF THE GFS/ECMWF/GEM HAVE SPED UP THE EXITING
SRN STREAM WAVE...PUSHING IT THROUGH THE LOWER GREAT LKS AND OHIO
VALLEY BY 06Z THURS. AT THAT TIME...NRN STREAM WAVE WILL BE
APPROACHING THE UPPER GREAT LKS AND PASS THROUGH ON THURS.
THUS...WILL CONTINUE TO MENTION PCPN CHANCES DURING THAT
TIME...MAINLY DUE TO THE APPROACHING NRN STREAM WAVE.
BEHIND THESE DISTURBANCES...COLDER H850 TEMPS /TOWARDS -14C/ WILL
FILTER OVER THE UPPER GREAT LKS THURS INTO FRI AND LEAD TO LES UNDER
NWRLY FLOW. BEST CHANCES LOOK TO BE THURS INTO FRI MORNING WITH
ADDITIONAL MOISTURE FROM THE UPPER TROUGH...BEFORE SFC HIGH BEGINS
TO PULL DRIER AIR AND WARMER TEMPS ALOFT IN ON FRI AFTN. HAVE STUCK
WITH LOW CHANCES FOR NOW...BUT MAY NEED TO BUMP UP POPS IF
CONDITIONS REMAIN FAVORABLE. SWRLY FLOW WILL REDEVELOP FRI NIGHT AND
CONTINUE INTO SAT...AHEAD OF THE NEXT NRN STREAM SHORTWAVE TO AFFECT
THE AREA LATE SAT.
&&
.AVIATION /FOR THE 18Z TAF ISSUANCE/...
INCREASING SW SFC WINDS WILL CONTINUE THROUGH THE EARLY EVENING
HOURS...WHEN WINDS DECOUPLE/INVERSION TAKES HOLD AND THE STRONGEST
WINDS REMAIN ALOFT. THESE STRONG WINDS AROUND 50KTS AROUND 2KFT
ABOVE THE SFC WILL GREATLY DIMINISH TO AROUND 25KTS BETWEEN 03Z AND
06Z MONDAY /WEST TO EAST/. AS A RESULT...WILL KEEP LLWS AT ALL SITES
THROUGH THE MID TO LATE EVENING HOURS. A TROUGH/COLD FRONT SWINGING
WEST TO EAST OVERNIGHT WILL PUSH WINDS TO A MORE NW DIRECTION...AS
WELL AS INCREASED LOW LEVEL MOISTURE AND PLENTY OF COLD AIR. EXPECT
MVFR TO HIGH END IFR CEIGS POSSIBLE BEHIND THE COLD FRONT /LOWEST AT
CMX AND IWD GIVEN THE FAVORABLE NW UPSLOPE WINDS OFF LS/...WITH ONLY
MINIMAL IMPROVEMENT BY 18Z MONDAY PRIMARILY WEST AS DRIER AIR WORKS
IN.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
AS PRES GRADIENT TIGHTENS WITH LOW PRES MOVING ACROSS MANITOBA INTO
NRN ONTARIO...SW WINDS WILL BE ON THE INCREASE TODAY. ALTHOUGH
INVERSION WILL LIMIT NEAR SFC WINDS FROM BEING STRONGER...AREA OF
PRES FALLS ON THE ORDER OF 6MB/3HR PASSING OVER AND JUST N OF LAKE
SUPERIOR WILL WORK TO BOOST WINDS TO GALE FORCE OVER CNTRL AND ERN
LAKE SUPERIOR LATER THIS AFTERNOON AND TONIGHT. HIGHEST WINDS...
PERHAPS GUSTING TO AROUND 40KT...WILL LIKELY OCCUR OVER EASTERN
PORTIONS OF THE LAKE FROM STANNARD ROCK EASTWARD DUE TO FAVORABLE
POSITIONING OF PRES FALLS. AREA AROUND GRAND MARAIS SHOULD BE
ESPECIALLY FAVORED FOR STRONGER WINDS FOR A FEW HRS THIS EVENING.
AFTER COLD FRONTAL PASSAGE TONIGHT ASSOCIATED WITH THE LOW PRES
SYSTEM...NW WINDS WILL PROBABLY GUST TO AROUND 35KT OVER THE E HALF
OF THE LAKE INTO MON MORNING. WINDS WILL DIMINISH W TO E MON
AFTN/NIGHT AS HIGH PRES SYSTEM QUICKLY PASSES ACROSS THE GREAT
LAKES. DEEP LOW PRES MOVING E TO HUDSON BAY EARLY TUE WILL PROBABLY
BRING ANOTHER ROUND OF SW GALES TO PORTIONS OF LAKE SUPERIOR. SW
WIND DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND ISLE ROYALE
FOR STRONGEST WINDS TUE. GALES WILL END TUE NIGHT AS PRES GRADIENT
WEAKENS. WINDS WILL BE BLO 30KT FOR WED/THU.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
GALE WARNING UNTIL 1 PM EST MONDAY FOR LSZ266-267.
GALE WARNING UNTIL 7 AM EST MONDAY FOR LSZ264.
GALE WARNING UNTIL 1 AM EST MONDAY FOR LSZ263.
GALE WARNING FROM 4 PM THIS AFTERNOON TO 1 PM EST MONDAY FOR
LSZ250-251.
LAKE MICHIGAN...
GALE WARNING FROM 4 PM THIS AFTERNOON TO 1 AM EST MONDAY FOR
LMZ248-250.
&&
$$
DISCUSSION...SRF
AVIATION...KF
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
740 AM EST SUN DEC 18 2011
UPDATED AVIATION DISCUSSION FOR THE 12Z TAFS
.DISCUSSION /TODAY THROUGH SATURDAY/... ISSUED AT 431 AM EST
QUIET MORNING ACROSS UPPER MICHIGAN...AS SFC RIDGE IS SLIDING ACROSS
THE UPPER GREAT LKS REGION. PERSISTENT AREA OF LOW CLOUDS EARLY THIS
MORNING ON SATELLITE...STRETCHING SW INTO NRN WI. MOST MODELS HAVING
A DIFFICULT TIME WITH THEM...BUT RUC SEEMS TO HAVE A DECENT HANDLE
ON LOW CLOUDS ON 0.5-1KM RH FIELDS...SO HAVE FOLLOWED THAT FOR THE
EXIT OF THE MVFR CLOUDS THIS MORNING. THINK THEY WILL LIKELY PERSIST
THROUGH THE FIRST PART OF THE MORNING UNTIL LLVL WINDS SHIFT TO THE
SW AND PUSH THEM NE OF THE AREA.
1002MB LOW PRESSURE SYSTEM CURRENTLY LOCATED JUST NW OF LK WINNIPEG
WILL SLOWLY DEEPEN THROUGH THE DAY...AS A NRN STREAM SHORTWAVE
AMPLIFIES OVER SOUTHERN CANADA THROUGH THE DAY. BY 00Z...SHOULD SEE
A 999MB LOW LOCATED JUST TO THE N OF LK SUPERIOR. STRONG H850-500
WAA OVER SRN CANADA /AND PRODUCING A FEW -SHSN E OF LK WINNIPEG/
WILL SHIFT ESE THROUGH SRN ONTARIO AND FAR NRN LK SUPERIOR FROM MID
MORNING THROUGH THE REST OF THE DAY. WITH THE BEST MOISTURE LOCATED
IN THIS AREA...EXPECT THE PCPN TO STAY N OF THE LAND AREAS. HEADING
FARTHER S OVER UPPER MI...DRY AIR BELOW H750 SHOULD KEEP ANY PCPN
COMING OUT OF THE MID CLOUDS FROM REACHING THE SFC FROM MID MORNING
THROUGH EARLY AFTN. LIKELY WON/T SEE MUCH SUN THROUGH THE MORNING
HOURS WITH THE LINGERING LLVL CLOUDS THAT WILL BE OVERRUN BY THE
INCOMING MID CLOUDS. DRY SLOT BEGINS TO MOVE OVER THE AREA AROUND
MID AFTN AND MAY LEAD TO SOME CLEARING...ESPECIALLY OVER THE W HALF.
WITH THE LOW INTENSIFYING AS IT MOVES N OF THE AREA...WILL LIKELY
SEE SOME GUSTY SW WINDS THIS AFTN. STRENGTHENING INVERSION AROUND
H900 WILL LIMIT ACCESS TO THE LLVL JET AROUND 45KTS. BUT TIGHTENING
PRESS GRADIENT WILL STILL LEAD TO GUSTS IN THE 20-30KT
RANGE...ESPECIALLY IN THE SW WIND DOWNSLOPE AREAS NEAR LK SUPERIOR.
THE INVERSION AND CLEARING THIS AFTN MAKES TEMPS TRICKY...AS THERE
WILL BE A LIMITED PERIOD FOR SUNSHINE HELP MIX HIGHER ALOFT. THOUGH
PREVIOUS HIGHS LOOKED GOOD AND ONLY MADE MINOR TWEAKS. WITH THE WARM
START AND SSWRLY FLOW...EXPECT THE HIGHS TO BE IN THE UPPER 30S AND
MAYBE AN ISOLATED 40 OVER THE WRN CWA /WHERE WARMER AIR SURGES INTO
THE AREA AND THERE IS A LONGER PERIOD OF CLEAR SKIES/...ALONG WITH
DOWNSLOPE AREAS NEAR LK SUPERIOR.
SFC LOW WILL QUICKLY DEEPEN TO 993MB THROUGH THE NIGHT AS IT SHIFTS
JUST SE OF JAMES BAY BY 12Z. DRY SLOT WILL STILL BE OVER THE AREA
AND PROVIDE A CLEAR BUT BREEZY EVENING. SFC TROUGH/COLD FRONT WILL
THEN SLIDE SE THROUGH THE CWA AFTER MIDNIGHT AND BRING A CHANCE FOR
PCPN TO AREAS NEAR LK SUPERIOR. NOT OVERLY IMPRESSED WITH
FORCING/MOISTURE ALONG THE FRONT...SO HAVE WENT WITH SLIGHT
CHANCES...EXCEPT FOR FAVORABLE UPSLOPE NW WIND LOCATIONS OVER THE
WRN CWA. P-TYPE WILL BE SNOW INITIALLY WITH THE PASSAGE OF THE
FRONT...BUT COULD BE SOME FZDZ WITH THE UPSLOPE FLOW OVER THE WRN
U.P. SOUNDINGS SHOW INCREASING LLVL LAPSE RATES OVER THE WEST AFTER
06Z TONIGHT BELOW THE 3-4KFT INVERSION. WITH NEAR SFC DRY AIR
PUTTING CLOUD BASES AROUND 1.5-2.5KFT...OVERALL CLOUD DEPTH WILL BE
FAIRLY SHALLOW. IN ADDITION...CLOUD TOPS ARE ONLY AROUND -7 TO -8C
AFTER THE FRONT MOVES THROUGH...LIMITING ICE CRYSTALS IN THE CLOUDS.
THEREFORE...HAVE ADDED A MENTION OF FZDZ OVER THE W AFTER 09Z. OVER
THE E...WARMER TEMPS WILL LIKELY LEAD TO MORE OF A DZ/SN POTENTIAL
LATE TONIGHT.
WITH CONTINUED H925-850 MOISTURE AND H850 TEMPS FALLING TOWARDS -10C
BY MID MORNING...EXPECT A PERIOD OF LK ENHANCED PCPN DURING THE
MORNING HOURS. TEMPS SHOULD FALL ENOUGH MON MORN OVER THE W TO
PRODUCE ENOUGH ICE CRYSTALS FOR ANY LINGERING SHOWERS TO BE ALL
SNOW. THERE COULD BE A SLIGHT LAG OVER THE E NEAR LK SUPERIOR FOR
THE FIRST COUPLE OF HOURS AND MENTIONED A -SHSN/FZDZ INITIALLY IN
THE MORNING. LAKE EFFECT POTENTIAL QUICKLY DIMINISHES HEADING INTO
THE AFTN...AS H850-700 SUBSIDENCE INCREASES AND LLVL MOISTURE
DEPARTS. IN ADDITION...MODELS SHOWING INVERSION HEIGHTS AT OR BELOW
3KFT IN THE AFTN AND LOCAL/NATIONAL HIRES WRF RUNS NOT SHOWING ANY
PCPN. WITH ALL THE NEGATIVES...HAVE TAPERED BACK EXISTING POPS IN
THE AFTN...BUT DID LEAVE SOME LOW CHANCES OVER THE E FOR NNW WIND
FAVORED LOCATIONS WHERE THE LONGER FETCH MAY HELP KEEP PCPN GOING.
HIGH PRESSURE RIDGE WILL BUILD OVER THE AREA ON MON NIGHT...BRINGING
AN END TO ANY LINGERING LES EARLY IN THE EVENING. WITH LIGHT WINDS
AND CLEAR SKIES UNDER THE HIGH PRESSURE RIDGE...EXPECT A GOOD
RADIATIONAL COOLING NIGHT. PWAT VALUES /AROUND 0.1 INCH OR 35
PERCENT OF NORMAL/ SUPPORT GOING ON THE LOW END OF GUIDANCE...AND
HAVE LOWS FALLING INTO THE SINGLE DIGITS ABOVE ZERO.
NRN STREAM OF THE JET WILL REMAIN N OF THE AREA FOR TUES/WED...WHILE
THE SRN STREAM IS LOCATED OVER THE SRN CONUS. THIS LEAVES THE AREA
WITH FAIRLY QUIET AND SEASONABLE CONDITIONS. SFC RIDGE WILL BE OVER
THE CWA AT THE START OF TUES...WITH ANOTHER SHORTWAVE MOVING THROUGH
SRN CANADA IN THE NRN STREAM. AS WITH THE SYSTEM TODAY...MAIN
ENERGY/MOISTURE WILL BE JUST TO THE N OF THE AREA...BRUSHING NRN LK
SUPERIOR. AS THIS QUICKLY MOVES E TUES EVENING...WEAK SFC RIDGE WILL
LIKELY BUILD BACK OVER THE AREA FOR TUES NIGHT INTO WED MORNING.
SEASONABLE TEMPS WILL CONTINUE...ALTHOUGH THE GUSTY WINDS AT TIMES
WILL MAKE IT FEEL A LITTLE COOLER.
DIFFERENCES START TO APPEAR IN THE EXTENDED MODELS WED INTO THURS
NIGHT WITH THE HANDLING OF THE EASTWARD MOVING UPPER LOW IN THE SRN
STREAM THAT WILL BE OVER THE CNTRL ROCKIES ON WED. ANOTHER NRN
STREAM TROUGH WILL BE DROPPING THROUGH THE CANADIAN ROCKIES AT THIS
TIME AND THEY WILL TRY TO MERGE THE NRN/SRN STREAMS OVER THE GREAT
LAKES REGION. 00Z RUNS OF THE GFS/ECMWF/GEM HAVE SPED UP THE EXITING
SRN STREAM WAVE...PUSHING IT THROUGH THE LOWER GREAT LKS AND OHIO
VALLEY BY 06Z THURS. AT THAT TIME...NRN STREAM WAVE WILL BE
APPROACHING THE UPPER GREAT LKS AND PASS THROUGH ON THURS.
THUS...WILL CONTINUE TO MENTION PCPN CHANCES DURING THAT
TIME...MAINLY DUE TO THE APPROACHING NRN STREAM WAVE.
BEHIND THESE DISTURBANCES...COLDER H850 TEMPS /TOWARDS -14C/ WILL
FILTER OVER THE UPPER GREAT LKS THURS INTO FRI AND LEAD TO LES UNDER
NWRLY FLOW. BEST CHANCES LOOK TO BE THURS INTO FRI MORNING WITH
ADDITIONAL MOISTURE FROM THE UPPER TROUGH...BEFORE SFC HIGH BEGINS
TO PULL DRIER AIR AND WARMER TEMPS ALOFT IN ON FRI AFTN. HAVE STUCK
WITH LOW CHANCES FOR NOW...BUT MAY NEED TO BUMP UP POPS IF
CONDITIONS REMAIN FAVORABLE. SWRLY FLOW WILL REDEVELOP FRI NIGHT AND
CONTINUE INTO SAT...AHEAD OF THE NEXT NRN STREAM SHORTWAVE TO AFFECT
THE AREA LATE SAT.
&&
.AVIATION /FOR THE 12Z TAF ISSUANCE/...
STRATUS DECK WITH MVFR CIGS WILL CONTINUE TO LIFT NE THIS MORNING AS
SW FLOW INCREASES AHEAD OF AN APPROACHING COLD FRONT. LOW CLOUDS
CLEARED KIWD A FEW HRS AGO...AND KCMX/KSAW SHOULD SEE THE STRATUS
DEPART MID TO LATE MORNING. THEREAFTER...VFR CONDITIONS WILL PREVAIL
INTO THE EVENING HRS AT ALL 3 TAF SITES. TIGHTENING PRES GRADIENT
WILL LEAD TO GUSTY SW WINDS INTO THE 20-25KT RANGE THIS AFTN.
THEN...THERE SHOULD BE ENOUGH DECOUPLING THIS EVENING TO RESULT IN
LLWS AS LOW-LEVEL JET WILL STILL BE OVER THE AREA. AFTER COLD FRONT
PASSAGE TONIGHT...MODELS ARE INDICATING A GOOD PUSH OF LOW-LEVEL
MOISTURE. THERE ARE LOW CLOUDS WELL UPSTREAM BEHIND FRONT...SO OPTED
TO DROP CIGS TO LOW MVFR LATER TONIGHT. CERTAINLY POSSIBLE THAT CIGS
COULD DROP TO IFR...ESPECIALLY AT KCMX/KIWD DUE TO UPSLOPING NW WIND.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
AS PRES GRADIENT TIGHTENS WITH LOW PRES MOVING ACROSS MANITOBA INTO
NRN ONTARIO...SW WINDS WILL BE ON THE INCREASE TODAY. ALTHOUGH
INVERSION WILL LIMIT NEAR SFC WINDS FROM BEING STRONGER...AREA OF
PRES FALLS ON THE ORDER OF 6MB/3HR PASSING OVER AND JUST N OF LAKE
SUPERIOR WILL WORK TO BOOST WINDS TO GALE FORCE OVER CNTRL AND ERN
LAKE SUPERIOR LATER THIS AFTERNOON AND TONIGHT. HIGHEST WINDS...
PERHAPS GUSTING TO AROUND 40KT...WILL LIKELY OCCUR OVER EASTERN
PORTIONS OF THE LAKE FROM STANNARD ROCK EASTWARD DUE TO FAVORABLE
POSITIONING OF PRES FALLS. AREA AROUND GRAND MARAIS SHOULD BE
ESPECIALLY FAVORED FOR STRONGER WINDS FOR A FEW HRS THIS EVENING.
AFTER COLD FRONTAL PASSAGE TONIGHT ASSOCIATED WITH THE LOW PRES
SYSTEM...NW WINDS WILL PROBABLY GUST TO AROUND 35KT OVER THE E HALF
OF THE LAKE INTO MON MORNING. WINDS WILL DIMINISH W TO E MON
AFTN/NIGHT AS HIGH PRES SYSTEM QUICKLY PASSES ACROSS THE GREAT
LAKES. DEEP LOW PRES MOVING E TO HUDSON BAY EARLY TUE WILL PROBABLY
BRING ANOTHER ROUND OF SW GALES TO PORTIONS OF LAKE SUPERIOR. SW
WIND DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND ISLE ROYALE
FOR STRONGEST WINDS TUE. GALES WILL END TUE NIGHT AS PRES GRADIENT
WEAKENS. WINDS WILL BE BLO 30KT FOR WED/THU.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...
GALE WARNING FROM 3 PM THIS AFTERNOON TO 1 PM EST MONDAY FOR
LSZ266-267.
GALE WARNING FROM 3 PM THIS AFTERNOON TO 7 AM EST MONDAY FOR
LSZ264.
GALE WARNING FROM 1 PM THIS AFTERNOON TO 1 AM EST MONDAY FOR
LSZ263.
GALE WARNING FROM 4 PM THIS AFTERNOON TO 1 PM EST MONDAY FOR
LSZ250-251.
LAKE MICHIGAN...
GALE WARNING FROM 7 PM THIS EVENING TO 1 AM EST MONDAY FOR
LMZ248-250.
&&
$$
DISCUSSION...SRF
AVIATION...ROLFSON
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
431 AM EST SUN DEC 18 2011
.DISCUSSION /TODAY THROUGH SATURDAY/...
QUIET MORNING ACROSS UPPER MICHIGAN...AS SFC RIDGE IS SLIDING ACROSS
THE UPPER GREAT LKS REGION. PERSISTENT AREA OF LOW CLOUDS EARLY THIS
MORNING ON SATELLITE...STRETCHING SW INTO NRN WI. MOST MODELS HAVING
A DIFFICULT TIME WITH THEM...BUT RUC SEEMS TO HAVE A DECENT HANDLE
ON LOW CLOUDS ON 0.5-1KM RH FIELDS...SO HAVE FOLLOWED THAT FOR THE
EXIT OF THE MVFR CLOUDS THIS MORNING. THINK THEY WILL LIKELY PERSIST
THROUGH THE FIRST PART OF THE MORNING UNTIL LLVL WINDS SHIFT TO THE
SW AND PUSH THEM NE OF THE AREA.
1002MB LOW PRESSURE SYSTEM CURRENTLY LOCATED JUST NW OF LK WINNIPEG
WILL SLOWLY DEEPEN THROUGH THE DAY...AS A NRN STREAM SHORTWAVE
AMPLIFIES OVER SOUTHERN CANADA THROUGH THE DAY. BY 00Z...SHOULD SEE
A 999MB LOW LOCATED JUST TO THE N OF LK SUPERIOR. STRONG H850-500
WAA OVER SRN CANADA /AND PRODUCING A FEW -SHSN E OF LK WINNIPEG/
WILL SHIFT ESE THROUGH SRN ONTARIO AND FAR NRN LK SUPERIOR FROM MID
MORNING THROUGH THE REST OF THE DAY. WITH THE BEST MOISTURE LOCATED
IN THIS AREA...EXPECT THE PCPN TO STAY N OF THE LAND AREAS. HEADING
FARTHER S OVER UPPER MI...DRY AIR BELOW H750 SHOULD KEEP ANY PCPN
COMING OUT OF THE MID CLOUDS FROM REACHING THE SFC FROM MID MORNING
THROUGH EARLY AFTN. LIKELY WON/T SEE MUCH SUN THROUGH THE MORNING
HOURS WITH THE LINGERING LLVL CLOUDS THAT WILL BE OVERRUN BY THE
INCOMING MID CLOUDS. DRY SLOT BEGINS TO MOVE OVER THE AREA AROUND
MID AFTN AND MAY LEAD TO SOME CLEARING...ESPECIALLY OVER THE W HALF.
WITH THE LOW INTENSIFYING AS IT MOVES N OF THE AREA...WILL LIKELY
SEE SOME GUSTY SW WINDS THIS AFTN. STRENGTHENING INVERSION AROUND
H900 WILL LIMIT ACCESS TO THE LLVL JET AROUND 45KTS. BUT TIGHTENING
PRESS GRADIENT WILL STILL LEAD TO GUSTS IN THE 20-30KT
RANGE...ESPECIALLY IN THE SW WIND DOWNSLOPE AREAS NEAR LK SUPERIOR.
THE INVERSION AND CLEARING THIS AFTN MAKES TEMPS TRICKY...AS THERE
WILL BE A LIMITED PERIOD FOR SUNSHINE HELP MIX HIGHER ALOFT. THOUGH
PREVIOUS HIGHS LOOKED GOOD AND ONLY MADE MINOR TWEAKS. WITH THE WARM
START AND SSWRLY FLOW...EXPECT THE HIGHS TO BE IN THE UPPER 30S AND
MAYBE AN ISOLATED 40 OVER THE WRN CWA /WHERE WARMER AIR SURGES INTO
THE AREA AND THERE IS A LONGER PERIOD OF CLEAR SKIES/...ALONG WITH
DOWNSLOPE AREAS NEAR LK SUPERIOR.
SFC LOW WILL QUICKLY DEEPEN TO 993MB THROUGH THE NIGHT AS IT SHIFTS
JUST SE OF JAMES BAY BY 12Z. DRY SLOT WILL STILL BE OVER THE AREA
AND PROVIDE A CLEAR BUT BREEZY EVENING. SFC TROUGH/COLD FRONT WILL
THEN SLIDE SE THROUGH THE CWA AFTER MIDNIGHT AND BRING A CHANCE FOR
PCPN TO AREAS NEAR LK SUPERIOR. NOT OVERLY IMPRESSED WITH
FORCING/MOISTURE ALONG THE FRONT...SO HAVE WENT WITH SLIGHT
CHANCES...EXCEPT FOR FAVORABLE UPSLOPE NW WIND LOCATIONS OVER THE
WRN CWA. P-TYPE WILL BE SNOW INITIALLY WITH THE PASSAGE OF THE
FRONT...BUT COULD BE SOME FZDZ WITH THE UPSLOPE FLOW OVER THE WRN
U.P. SOUNDINGS SHOW INCREASING LLVL LAPSE RATES OVER THE WEST AFTER
06Z TONIGHT BELOW THE 3-4KFT INVERSION. WITH NEAR SFC DRY AIR
PUTTING CLOUD BASES AROUND 1.5-2.5KFT...OVERALL CLOUD DEPTH WILL BE
FAIRLY SHALLOW. IN ADDITION...CLOUD TOPS ARE ONLY AROUND -7 TO -8C
AFTER THE FRONT MOVES THROUGH...LIMITING ICE CRYSTALS IN THE CLOUDS.
THEREFORE...HAVE ADDED A MENTION OF FZDZ OVER THE W AFTER 09Z. OVER
THE E...WARMER TEMPS WILL LIKELY LEAD TO MORE OF A DZ/SN POTENTIAL
LATE TONIGHT.
WITH CONTINUED H925-850 MOISTURE AND H850 TEMPS FALLING TOWARDS -10C
BY MID MORNING...EXPECT A PERIOD OF LK ENHANCED PCPN DURING THE
MORNING HOURS. TEMPS SHOULD FALL ENOUGH MON MORN OVER THE W TO
PRODUCE ENOUGH ICE CRYSTALS FOR ANY LINGERING SHOWERS TO BE ALL
SNOW. THERE COULD BE A SLIGHT LAG OVER THE E NEAR LK SUPERIOR FOR
THE FIRST COUPLE OF HOURS AND MENTIONED A -SHSN/FZDZ INITIALLY IN
THE MORNING. LAKE EFFECT POTENTIAL QUICKLY DIMINISHES HEADING INTO
THE AFTN...AS H850-700 SUBSIDENCE INCREASES AND LLVL MOISTURE
DEPARTS. IN ADDITION...MODELS SHOWING INVERSION HEIGHTS AT OR BELOW
3KFT IN THE AFTN AND LOCAL/NATIONAL HIRES WRF RUNS NOT SHOWING ANY
PCPN. WITH ALL THE NEGATIVES...HAVE TAPERED BACK EXISTING POPS IN
THE AFTN...BUT DID LEAVE SOME LOW CHANCES OVER THE E FOR NNW WIND
FAVORED LOCATIONS WHERE THE LONGER FETCH MAY HELP KEEP PCPN GOING.
HIGH PRESSURE RIDGE WILL BUILD OVER THE AREA ON MON NIGHT...BRINGING
AN END TO ANY LINGERING LES EARLY IN THE EVENING. WITH LIGHT WINDS
AND CLEAR SKIES UNDER THE HIGH PRESSURE RIDGE...EXPECT A GOOD
RADIATIONAL COOLING NIGHT. PWAT VALUES /AROUND 0.1 INCH OR 35
PERCENT OF NORMAL/ SUPPORT GOING ON THE LOW END OF GUIDANCE...AND
HAVE LOWS FALLING INTO THE SINGLE DIGITS ABOVE ZERO.
NRN STREAM OF THE JET WILL REMAIN N OF THE AREA FOR TUES/WED...WHILE
THE SRN STREAM IS LOCATED OVER THE SRN CONUS. THIS LEAVES THE AREA
WITH FAIRLY QUIET AND SEASONABLE CONDITIONS. SFC RIDGE WILL BE OVER
THE CWA AT THE START OF TUES...WITH ANOTHER SHORTWAVE MOVING THROUGH
SRN CANADA IN THE NRN STREAM. AS WITH THE SYSTEM TODAY...MAIN
ENERGY/MOISTURE WILL BE JUST TO THE N OF THE AREA...BRUSHING NRN LK
SUPERIOR. AS THIS QUICKLY MOVES E TUES EVENING...WEAK SFC RIDGE WILL
LIKELY BUILD BACK OVER THE AREA FOR TUES NIGHT INTO WED MORNING.
SEASONABLE TEMPS WILL CONTINUE...ALTHOUGH THE GUSTY WINDS AT TIMES
WILL MAKE IT FEEL A LITTLE COOLER.
DIFFERENCES START TO APPEAR IN THE EXTENDED MODELS WED INTO THURS
NIGHT WITH THE HANDLING OF THE EASTWARD MOVING UPPER LOW IN THE SRN
STREAM THAT WILL BE OVER THE CNTRL ROCKIES ON WED. ANOTHER NRN
STREAM TROUGH WILL BE DROPPING THROUGH THE CANADIAN ROCKIES AT THIS
TIME AND THEY WILL TRY TO MERGE THE NRN/SRN STREAMS OVER THE GREAT
LAKES REGION. 00Z RUNS OF THE GFS/ECMWF/GEM HAVE SPED UP THE EXITING
SRN STREAM WAVE...PUSHING IT THROUGH THE LOWER GREAT LKS AND OHIO
VALLEY BY 06Z THURS. AT THAT TIME...NRN STREAM WAVE WILL BE
APPROACHING THE UPPER GREAT LKS AND PASS THROUGH ON THURS.
THUS...WILL CONTINUE TO MENTION PCPN CHANCES DURING THAT
TIME...MAINLY DUE TO THE APPROACHING NRN STREAM WAVE.
BEHIND THESE DISTURBANCES...COLDER H850 TEMPS /TOWARDS -14C/ WILL
FILTER OVER THE UPPER GREAT LKS THURS INTO FRI AND LEAD TO LES UNDER
NWRLY FLOW. BEST CHANCES LOOK TO BE THURS INTO FRI MORNING WITH
ADDITIONAL MOISTURE FROM THE UPPER TROUGH...BEFORE SFC HIGH BEGINS
TO PULL DRIER AIR AND WARMER TEMPS ALOFT IN ON FRI AFTN. HAVE STUCK
WITH LOW CHANCES FOR NOW...BUT MAY NEED TO BUMP UP POPS IF
CONDITIONS REMAIN FAVORABLE. SWRLY FLOW WILL REDEVELOP FRI NIGHT AND
CONTINUE INTO SAT...AHEAD OF THE NEXT NRN STREAM SHORTWAVE TO AFFECT
THE AREA LATE SAT.
&&
.AVIATION /FOR THE 06Z TAF ISSUANCE/...
STRATUS DECK WITH MVFR CIGS SHOULD GRADUALLY LIFT FROM THE WEST AS
SFC RDG AXIS MOVES ACROSS THE AREA IN THE OVERNIGHT AND EARLY
MORNING HRS. AFTER CLOUDS DISSIPATE LOOK FOR VFR CONDITIONS THROUGH
THE DAY TODAY. INCREASING SOUTHERLY WINDS GUSTING 22 TO 25KTS BEHIND
THE SFC RDG AND AHEAD OF NEXT APPROACHING TROUGH FROM THE NRN PLAINS
WILL RESULT IN GUSTY SSW WINDS TO 25 KT...ESPECIALLY AT KIWD AND KSAW
BY EARLY AFTERNOON. EXPECT LLWS WIND SHEAR AT ALL TAF SITES THIS
EVENING WITH TIGHT SW GRADIENT AHEAD OF THE TROUGH. SOME GUSTY WRLY
WINDS BEHIND THE TROF/FRONTAL PASSAGE CAN BE EXPECTED AT KCMX AROUND
MIDNIGHT SUNDAY NIGHT.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
AS PRES GRADIENT TIGHTENS WITH LOW PRES MOVING ACROSS MANITOBA INTO
NRN ONTARIO...SW WINDS WILL BE ON THE INCREASE TODAY. ALTHOUGH
INVERSION WILL LIMIT NEAR SFC WINDS FROM BEING STRONGER...AREA OF
PRES FALLS ON THE ORDER OF 6MB/3HR PASSING OVER AND JUST N OF LAKE
SUPERIOR WILL WORK TO BOOST WINDS TO GALE FORCE OVER CNTRL AND ERN
LAKE SUPERIOR LATER THIS AFTERNOON AND TONIGHT. HIGHEST WINDS...
PERHAPS GUSTING TO AROUND 40KT...WILL LIKELY OCCUR OVER EASTERN
PORTIONS OF THE LAKE FROM STANNARD ROCK EASTWARD DUE TO FAVORABLE
POSITIONING OF PRES FALLS. AREA AROUND GRAND MARAIS SHOULD BE
ESPECIALLY FAVORED FOR STRONGER WINDS FOR A FEW HRS THIS EVENING.
AFTER COLD FRONTAL PASSAGE TONIGHT ASSOCIATED WITH THE LOW PRES
SYSTEM...NW WINDS WILL PROBABLY GUST TO AROUND 35KT OVER THE E HALF
OF THE LAKE INTO MON MORNING. WINDS WILL DIMINISH W TO E MON
AFTN/NIGHT AS HIGH PRES SYSTEM QUICKLY PASSES ACROSS THE GREAT
LAKES. DEEP LOW PRES MOVING E TO HUDSON BAY EARLY TUE WILL PROBABLY
BRING ANOTHER ROUND OF SW GALES TO PORTIONS OF LAKE SUPERIOR. SW
WIND DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND ISLE ROYALE
FOR STRONGEST WINDS TUE. GALES WILL END TUE NIGHT AS PRES GRADIENT
WEAKENS. WINDS WILL BE BLO 30KT FOR WED/THU.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
GALE WARNING FROM 3 PM THIS AFTERNOON TO 1 PM EST MONDAY FOR
LSZ266-267.
GALE WARNING FROM 3 PM THIS AFTERNOON TO 7 AM EST MONDAY FOR
LSZ264.
GALE WARNING FROM 1 PM THIS AFTERNOON TO 1 AM EST MONDAY FOR
LSZ263.
GALE WARNING FROM 4 PM THIS AFTERNOON TO 1 PM EST MONDAY FOR
LSZ250-251.
LAKE MICHIGAN...
GALE WARNING FROM 7 PM THIS EVENING TO 1 AM EST MONDAY FOR
LMZ248-250.
&&
$$
DISCUSSION...SRF
AVIATION...VOSS
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
1128 AM CST SUN DEC 18 2011
.DISCUSSION...
LATEST WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYZES CONTINUE TO
SHOW A CUTOFF UPPER LOW OVER THE SOUTHWEST US WITH A BROAD RIDGE
OVER-TOP OF IT EXTENDING FROM THE PACIFIC NORTHWEST COAST INTO THE
UPPER MIDWEST. THE DEEP UPPER LOW NORTH OF HUDSON BAY HAS MOVED
LITTLE OF LATE... AND SHOW NO SIGNS OF GOING ANYWHERE THROUGH AT
LEAST THE NEXT 10 DAYS ON THE GFS... ECMWF... AND THEIR RESPECTIVE
ENSEMBLES. IN THE BIG PICTURE... THIS SUGGESTS CONDITIONS IN OUR
NECK OF THE WOOD SHOULDN/T CHANGE TOO MUCH THROUGH AT LEAST THE
NEXT WEEK OR TWO... WITH NEAR TO ABOVE NORMAL TEMPERATURES
PREDOMINATING AS WEST TO NORTHWEST MID-UPPER LEVEL FLOW CONTINUES
TO BRING SYSTEMS OF PACIFIC ORIGIN INTO OUR AREA. WE WILL CONTINUE
TO SEE FAIRLY FREQUENT COLD FRONTAL PASSAGES... BUT NONE LOOK TO
BRING ANY TRUE ARCTIC AIR INTO THE REGION... AND INSTEAD WILL
SIMPLY BRING TEMPERATURES DOWN TO NEAR OR PERHAPS SLIGHTLY BELOW
NORMAL FOR BRIEF PERIODS OF TIME AS THEY MOVE THROUGH. AS FAR AS
PRECIPITATION GOES... THE PRESENT LONG WAVE PATTERN IS NOT
CONDUCIVE TO US SEEING MUCH... WITH MINIMAL MOISTURE RETURN AHEAD
OF INDIVIDUAL SHORTWAVES... AND THE DEEPENING OF SYSTEMS OCCURRING
SOUTH AND EAST OF OUR AREA AS THEY MOVE INTO THE MEAN LONG WAVE
TROUGH POSITION.
ROBUST WARM ADVECTION WILL OCCUR ACROSS THE AREA TODAY... WITH
TEMPERATURES SOARING INTO THE 40S IN MOST LOCATIONS... AND LIKELY
ECLIPSING THE 50 DEGREE MARK OVER WEST CENTRAL AND SOUTHWEST
MINNESOTA. IT ISN/T TOO OFTEN WE SEE 850MB TEMPERATURES IN EXCESS
OF 8C... BUT THAT LOOKS TO BE THE CASE TODAY OVER THE SOUTHERN
PART OF THE STATE. WE CERTAINLY WON/T MIX TO 850MB... BUT EVEN
MIXING THROUGH 950MB WILL ALLOW TEMPERATURES TO CLIMB TO AOA 50
DEGREES OVER MANY AREAS SOUTH AND WEST OF THE TWIN CITIES.
WOULDN/T BE SHOCKED IF THE TWIN CITIES MANAGES TO GET CLOSE TO 50
DEGREES DEPENDING UPON HOW WELL THINGS MIX OR IF WE/RE ABLE TO
ADVECT SOME OF THE WARMER UPSTREAM READINGS INTO THE AREA DURING
THE AFTERNOON HOURS. JUST NUDGED READINGS UP SLIGHTLY OVER
PREVIOUSLY FORECAST VALUES... BUT IT WILL CERTAINLY BE SOMETHING
TO KEEP AN EYE ON TODAY. LOW PRESSURE ASSOCIATED WITH THE
SHORTWAVE CURRENTLY SEEN MOVING INTO ALBERTA WILL PASS BY NORTH OF
THE STATE THIS EVENING... DRAGGING A COLD FRONT ACROSS THE AREA
DURING THE EVENING AND OVERNIGHT HOURS. THIS WILL COOL THINGS DOWN
TO ABOUT WHERE THEY SHOULD BE FOR MONDAY. A FEW FLURRIES COULD BE
SEEN BEHIND THE FRONT DEPENDING UPON HOW DEEP THE MOISTURE IS
BENEATH THE SUBSIDENCE INVERSION AND IF CYCLONIC BOUNDARY LAYER
FLOW IS ABLE TO LINGER. AT THIS POINT... THE CHANCES LOOK MINIMAL
AND IT WOULD ONLY BE SCATTERED FLURRIES AT BEST... SO LEFT IT OUT
OF THE FORECAST.
HIGH PRESSURE WILL BUILD ACROSS THE REGION MONDAY AFTER THROUGH
MONDAY NIGHT... AS THE 850-700MB THERMAL TROUGH MOVES ACROSS THE
AREA AND WEAKENS. THIS WILL BRING WHAT WILL FEEL LIKE A CHILLY
NIGHT MONDAY NIGHT... ALTHOUGH READINGS STILL LOOK TO BE NEAR OR
SLIGHTLY ABOVE NORMAL. WEAK WARM ADVECTION LOOKS TO BE IN PLACE
ACROSS THE REGION TUESDAY AND TUESDAY NIGHT AS A SHORTWAVE AND
SURFACE LOW MOVE BY WELL NORTH OF THE US/CANADA BORDER... AND A
SURFACE LOW ASSOCIATED WITH THE CUTOFF LOW CURRENTLY OVER THE
SOUTHWEST MOVES OUT OF THE SOUTHERN PLAINS TO THE OHIO VALLEY. WE
WILL FIND OURSELVES NESTLED BETWEEN THESE FEATURES... WITH BENIGN
WEATHER IN PLACE. A SLOWLY MOVING COLD FRONT WILL DROP SOUTH
THROUGH THE REGION WEDNESDAY INTO THURSDAY. THERE ARE SOME HINTS
WE COULD SEE MOISTURE POOL SUFFICIENTLY ALONG THIS BAROCLINIC ZONE
TO GET SOME PCPN DEPENDING UPON WHEN THE UPSTREAM SHORTWAVE
DROPPING SOUTHEAST FROM SOUTH CENTRAL CANADA IS ABLE TO CATCH UP
WITH IT. GIVEN UNCERTAINTIES IN NOT ONLY IF SOME PCPN WILL BE
SQUEEZED OUT... BUT WHEN AND WHERE IT MIGHT OCCUR... CHOSE TO
LEAVE PCPN OUT OF THE FORECAST IN THE WEDNESDAY TO THURSDAY TIME
FRAME... BUT FEEL THERE IS AT LEAST A CHANCE FOR SOME FLURRIES OF
VERY LIGHT SNOW DURING THAT PERIOD WHICH MAY GET INCLUDED AS WE
GET CLOSER TO THAT TIME PERIOD. THE MEDIUM RANGE GUIDANCE BECOMES
QUITE MUDDY IN ITS AGREEMENT BY WEEK/S END... WITH THE
DETERMINISTIC GFS AND ECMWF DIFFERING BY 15-20MB IN SURFACE
PRESSURES OVER OUR AREA BY FRIDAY AS THE GFS CLOSES OFF A SURFACE
LOW IN THE SAME AREA WHERE THE ECMWF SUGGESTS A FAIRLY POTENT
RIDGE. THE ECMWF SOLUTION WOULDN/T SUPPORT ANY PCPN... AND THE GFS
WOULD SUGGEST VERY LITTLE... SO THE PATH OF LEAST RESISTANCE AT
THIS POINT IS SIMPLY TO KEEP THINGS DRY.
&&
.AVIATION.../18Z TAF ISSUANCE/
NO AVIATION CONCERNS IN THE FIRST 6 TO 12 HRS WITH VFR CONDITIONS
PREVAILING...WITH WNDS FROM THE SW/S...BECOMING MORE W IN WESTERN
MN...AND SW IN EASTERN MN. SOME GUSTS UP TO 18-22 KTS ARE POSSIBLE
AT RWF/AXN/STC THIS AFTN. EAU/RNH WILL LIKELY REMAIN AOB 12 KTS
FROM THE SSW THIS AFTN...THAN MORE SW BY 23Z. AFT 6Z...A FRONTAL
BOUNDARY AND FAIRLY SHALLOW MOISTURE WILL MOVE SOUTHWARD ACROSS
THE FA. THERE REMAINS SOME CONCERN WITH MVFR CIGS DEVELOPING
ALONG AND BEHIND THIS FRONT. HOWEVER...MODELS SLOWLY DECREASE THE
LOW LEVEL MOISTURE AS IT HEADS TO THE S OVERNIGHT. CONFIDENCE
REMAINS LOW ON MVFR CIGS DEVELOPING. AFT 15Z...ALL AREAS SHOULD
LIFT TO VFR WITH CIGS AOA 4K. WNDS WILL INCREASING SLIGHTLY DURING
THE MORNING WITH SOME GUSTS FROM THE NW/NNW.
MSP...VFR CONDITIONS THRU 6Z WITH WNDS BECOMING MORE SW...THEN WSW
LATE THIS AFTN/EVENING. AFT 9Z...WNDS WILL SHIFT TO THE NW WITH
MVFR CIGS DEVELOPING. CONFIDENCE REMAINS LOW ON MVFR CIGS
ATTM...BUT ENOUGH TO WARRANT A PERIOD FROM 9-14Z. NO OTHER CHGS
EXPECTED AFT 15Z...WITH WNDS GENERALLY FROM THE NW/NNW ARND 10
KTS.
MON/TUE/WED...VFR CONDITIONS EXPECTED.
..JLT..
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
TRH/JLT
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
540 AM CST SUN DEC 18 2011
UPDATED TO ADD THE 12Z AVIATION DISCUSSION BELOW...
.DISCUSSION...
LATEST WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSES CONTINUE TO
SHOW A CUTOFF UPPER LOW OVER THE SOUTHWEST US WITH A BROAD RIDGE
OVERTOP OF IT EXTENDING FROM THE PACIFIC NORTHWEST COAST INTO THE
UPPER MIDWEST. THE DEEP UPPER LOW NORTH OF HUDSON BAY HAS MOVED
LITTLE OF LATE... AND SHOW NO SIGNS OF GOING ANYWHERE THROUGH AT
LEAST THE NEXT 10 DAYS ON THE GFS... ECMWF... AND THEIR RESPECTIVE
ENSEMBLES. IN THE BIG PICTURE... THIS SUGGESTS CONDITIONS IN OUR
NECK OF THE WOOD SHOULDN/T CHANGE TOO MUCH THROUGH AT LEAST THE
NEXT WEEK OR TWO... WITH NEAR TO ABOVE NORMAL TEMPERATURES
PREDOMINATING AS WEST TO NORTHWEST MID-UPPER LEVEL FLOW CONTINUES
TO BRING SYSTEMS OF PACIFIC ORIGIN INTO OUR AREA. WE WILL CONTINUE
TO SEE FAIRLY FREQUENT COLD FRONTAL PASSAGES... BUT NONE LOOK TO
BRING ANY TRUE ARCTIC AIR INTO THE REGION... AND INSTEAD WILL
SIMPLY BRING TEMPERATURES DOWN TO NEAR OR PERHAPS SLIGHTLY BELOW
NORMAL FOR BRIEF PERIODS OF TIME AS THEY MOVE THROUGH. AS FAR AS
PRECIPITATION GOES... THE PRESENT LONG WAVE PATTERN IS NOT
CONDUCIVE TO US SEEING MUCH... WITH MINIMAL MOISTURE RETURN AHEAD
OF INDIVIDUAL SHORTWAVES... AND THE DEEPENING OF SYSTEMS OCCURRING
SOUTH AND EAST OF OUR AREA AS THEY MOVE INTO THE MEAN LONG WAVE
TROUGH POSITION.
ROBUST WARM ADVECTION WILL OCCUR ACROSS THE AREA TODAY... WITH
TEMPERATURES SOARING INTO THE 40S IN MOST LOCATIONS... AND LIKELY
ECLIPSING THE 50 DEGREE MARK OVER WEST CENTRAL AND SOUTHWEST
MINNESOTA. IT ISN/T TOO OFTEN WE SEE 850MB TEMPERATURES IN EXCESS
OF 8C... BUT THAT LOOKS TO BE THE CASE TODAY OVER THE SOUTHERN
PART OF THE STATE. WE CERTAINLY WON/T MIX TO 850MB... BUT EVEN
MIXING THROUGH 950MB WILL ALLOW TEMPERATURES TO CLIMB TO AOA 50
DEGREES OVER MANY AREAS SOUTH AND WEST OF THE TWIN CITIES.
WOULDN/T BE SHOCKED IF THE TWIN CITIES MANAGES TO GET CLOSE TO 50
DEGREES DEPENDING UPON HOW WELL THINGS MIX OR IF WE/RE ABLE TO
ADVECT SOME OF THE WARMER UPSTREAM READINGS INTO THE AREA DURING
THE AFTERNOON HOURS. JUST NUDGED READINGS UP SLIGHTLY OVER
PREVIOUSLY FORECAST VALUES... BUT IT WILL CERTAINLY BE SOMETHING
TO KEEP AN EYE ON TODAY. LOW PRESSURE ASSOCIATED WITH THE
SHORTWAVE CURRENTLY SEEN MOVING INTO ALBERTA WILL PASS BY NORTH OF
THE STATE THIS EVENING... DRAGGING A COLD FRONT ACROSS THE AREA
DURING THE EVENING AND OVERNIGHT HOURS. THIS WILL COOL THINGS DOWN
TO ABOUT WHERE THEY SHOULD BE FOR MONDAY. A FEW FLURRIES COULD BE
SEEN BEHIND THE FRONT DEPENDING UPON HOW DEEP THE MOISTURE IS
BENEATH THE SUBSIDENCE INVERSION AND IF CYCLONIC BOUNDARY LAYER
FLOW IS ABLE TO LINGER. AT THIS POINT... THE CHANCES LOOK MINIMAL
AND IT WOULD ONLY BE SCATTERED FLURRIES AT BEST... SO LEFT IT OUT
OF THE FORECAST.
HIGH PRESSURE WILL BUILD ACROSS THE REGION MONDAY AFTER THROUGH
MONDAY NIGHT... AS THE 850-700MB THERMAL TROUGH MOVES ACROSS THE
AREA AND WEAKENS. THIS WILL BRING WHAT WILL FEEL LIKE A CHILLY
NIGHT MONDAY NIGHT... ALTHOUGH READINGS STILL LOOK TO BE NEAR OR
SLIGHTLY ABOVE NORMAL. WEAK WARM ADVECTION LOOKS TO BE IN PLACE
ACROSS THE REGION TUESDAY AND TUESDAY NIGHT AS A SHORTWAVE AND
SURFACE LOW MOVE BY WELL NORTH OF THE US/CANADA BORDER... AND A
SURFACE LOW ASSOCIATED WITH THE CUTOFF LOW CURRENTLY OVER THE
SOUTHWEST MOVES OUT OF THE SOUTHERN PLAINS TO THE OHIO VALLEY. WE
WILL FIND OURSELVES NESTLED BETWEEN THESE FEATURES... WITH BENIGN
WEATHER IN PLACE. A SLOWLY MOVING COLD FRONT WILL DROP SOUTH
THROUGH THE REGION WEDNESDAY INTO THURSDAY. THERE ARE SOME HINTS
WE COULD SEE MOISTURE POOL SUFFICIENTLY ALONG THIS BAROCLINIC ZONE
TO GET SOME PCPN DEPENDING UPON WHEN THE UPSTREAM SHORTWAVE
DROPPING SOUTHEAST FROM SOUTH CENTRAL CANADA IS ABLE TO CATCH UP
WITH IT. GIVEN UNCERTAINTIES IN NOT ONLY IF SOME PCPN WILL BE
SQUEEZED OUT... BUT WHEN AND WHERE IT MIGHT OCCUR... CHOSE TO
LEAVE PCPN OUT OF THE FORECAST IN THE WEDNESDAY TO THURSDAY TIME
FRAME... BUT FEEL THERE IS AT LEAST A CHANCE FOR SOME FLURRIES OF
VERY LIGHT SNOW DURING THAT PERIOD WHICH MAY GET INCLUDED AS WE
GET CLOSER TO THAT TIME PERIOD. THE MEDIUM RANGE GUIDANCE BECOMES
QUITE MUDDY IN ITS AGREEMENT BY WEEK/S END... WITH THE
DETERMINISTIC GFS AND ECMWF DIFFERING BY 15-20MB IN SURFACE
PRESSURES OVER OUR AREA BY FRIDAY AS THE GFS CLOSES OFF A SURFACE
LOW IN THE SAME AREA WHERE THE ECMWF SUGGESTS A FAIRLY POTENT
RIDGE. THE ECMWF SOLUTION WOULDN/T SUPPORT ANY PCPN... AND THE GFS
WOULD SUGGEST VERY LITTLE... SO THE PATH OF LEAST RESISTANCE AT
THIS POINT IS SIMPLY TO KEEP THINGS DRY.
&&
.AVIATION... /12Z TAF ISSUANCE/
WARM FRONT ADVANCING EAST INTO THE LOWER GREAT LAKES REGION LATER
TODAY. ONLY SOME HIGH CLOUDS ANTICIPATED OVER THE TAF SITES TODAY.
SURFACE WINDS INCREASING FROM THE SOUTH-SOUTHWEST 10-15 KT WITH
GUSTS BETWEEN 18-23 KT BY LATE MORNING. COLD FRONT WILL DROP SOUTH
INTO CENTRAL MN EARLY TONIGHT. THE FRONT WILL CONTINUE TO TREK SOUTH
OVER THE LOWER GREAT LAKES INTO THE CENTRAL PLAINS BY DAYBREAK
MONDAY. SURFACE OBSERVATION SHOWED SOME CEILING ROUGHLY BETWEEN
1000-3000 FEET AGL NEAR LAKE WINNEPEG. RESIDUAL MOISTURE ASSOCIATED
WITH THESE CLOUDS/CEILINGS SHOULD FLOW SOUTHEAST INTO MINNESOTA
OVERNIGHT. THE BIG QUESTION...IS IF THESE CLOUDS WILL BECOME A
CEILING OVERNIGHT. WL BRING SOME SCATTERED CLOUDS BETWEEN 1000-2000
FEET AGL OVER THE TAF SITES EARLY MONDAY MORNING.
KMSP...VFR CONDITIONS WILL REMAIN VFR THROUGH THE BULK OF THE
PERIOD. SOME LOWER CLOUDS WILL SNEAK DOWN OUT OF CANADA LATER THIS
EVENING AND OVERNIGHT. SURFACE WINDS SOUTHWEST AND INCREASING TO 10
TO 20 KT. SOME PATCHY OR LOW CLOUDS BETWEEN 1500-2000 FEET AGL
DEVELOPING AFTER MIDNIGHT TONIGHT.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
TRH/JM
AREA FORECAST DISCUSSION
NWS TWIN CITIES/CHANHASSEN MN
235 AM CST SUN DEC 18 2011
.DISCUSSION...
LATEST WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSES CONTINUE TO
SHOW A CUTOFF UPPER LOW OVER THE SOUTHWEST US WITH A BROAD RIDGE
OVERTOP OF IT EXTENDING FROM THE PACIFIC NORTHWEST COAST INTO THE
UPPER MIDWEST. THE DEEP UPPER LOW NORTH OF HUDSON BAY HAS MOVED
LITTLE OF LATE... AND SHOW NO SIGNS OF GOING ANYWHERE THROUGH AT
LEAST THE NEXT 10 DAYS ON THE GFS... ECMWF... AND THEIR RESPECTIVE
ENSEMBLES. IN THE BIG PICTURE... THIS SUGGESTS CONDITIONS IN OUR
NECK OF THE WOOD SHOULDN/T CHANGE TOO MUCH THROUGH AT LEAST THE
NEXT WEEK OR TWO... WITH NEAR TO ABOVE NORMAL TEMPERATURES
PREDOMINATING AS WEST TO NORTHWEST MID-UPPER LEVEL FLOW CONTINUES
TO BRING SYSTEMS OF PACIFIC ORIGIN INTO OUR AREA. WE WILL CONTINUE
TO SEE FAIRLY FREQUENT COLD FRONTAL PASSAGES... BUT NONE LOOK TO
BRING ANY TRUE ARCTIC AIR INTO THE REGION... AND INSTEAD WILL
SIMPLY BRING TEMPERATURES DOWN TO NEAR OR PERHAPS SLIGHTLY BELOW
NORMAL FOR BRIEF PERIODS OF TIME AS THEY MOVE THROUGH. AS FAR AS
PRECIPITATION GOES... THE PRESENT LONG WAVE PATTERN IS NOT
CONDUCIVE TO US SEEING MUCH... WITH MINIMAL MOISTURE RETURN AHEAD
OF INDIVIDUAL SHORTWAVES... AND THE DEEPENING OF SYSTEMS OCCURRING
SOUTH AND EAST OF OUR AREA AS THEY MOVE INTO THE MEAN LONG WAVE
TROUGH POSITION.
ROBUST WARM ADVECTION WILL OCCUR ACROSS THE AREA TODAY... WITH
TEMPERATURES SOARING INTO THE 40S IN MOST LOCATIONS... AND LIKELY
ECLIPSING THE 50 DEGREE MARK OVER WEST CENTRAL AND SOUTHWEST
MINNESOTA. IT ISN/T TOO OFTEN WE SEE 850MB TEMPERATURES IN EXCESS
OF 8C... BUT THAT LOOKS TO BE THE CASE TODAY OVER THE SOUTHERN
PART OF THE STATE. WE CERTAINLY WON/T MIX TO 850MB... BUT EVEN
MIXING THROUGH 950MB WILL ALLOW TEMPERATURES TO CLIMB TO AOA 50
DEGREES OVER MANY AREAS SOUTH AND WEST OF THE TWIN CITIES.
WOULDN/T BE SHOCKED IF THE TWIN CITIES MANAGES TO GET CLOSE TO 50
DEGREES DEPENDING UPON HOW WELL THINGS MIX OR IF WE/RE ABLE TO
ADVECT SOME OF THE WARMER UPSTREAM READINGS INTO THE AREA DURING
THE AFTERNOON HOURS. JUST NUDGED READINGS UP SLIGHTLY OVER
PREVIOUSLY FORECAST VALUES... BUT IT WILL CERTAINLY BE SOMETHING
TO KEEP AN EYE ON TODAY. LOW PRESSURE ASSOCIATED WITH THE
SHORTWAVE CURRENTLY SEEN MOVING INTO ALBERTA WILL PASS BY NORTH OF
THE STATE THIS EVENING... DRAGGING A COLD FRONT ACROSS THE AREA
DURING THE EVENING AND OVERNIGHT HOURS. THIS WILL COOL THINGS DOWN
TO ABOUT WHERE THEY SHOULD BE FOR MONDAY. A FEW FLURRIES COULD BE
SEEN BEHIND THE FRONT DEPENDING UPON HOW DEEP THE MOISTURE IS
BENEATH THE SUBSIDENCE INVERSION AND IF CYCLONIC BOUNDARY LAYER
FLOW IS ABLE TO LINGER. AT THIS POINT... THE CHANCES LOOK MINIMAL
AND IT WOULD ONLY BE SCATTERED FLURRIES AT BEST... SO LEFT IT OUT
OF THE FORECAST.
HIGH PRESSURE WILL BUILD ACROSS THE REGION MONDAY AFTER THROUGH
MONDAY NIGHT... AS THE 850-700MB THERMAL TROUGH MOVES ACROSS THE
AREA AND WEAKENS. THIS WILL BRING WHAT WILL FEEL LIKE A CHILLY
NIGHT MONDAY NIGHT... ALTHOUGH READINGS STILL LOOK TO BE NEAR OR
SLIGHTLY ABOVE NORMAL. WEAK WARM ADVECTION LOOKS TO BE IN PLACE
ACROSS THE REGION TUESDAY AND TUESDAY NIGHT AS A SHORTWAVE AND
SURFACE LOW MOVE BY WELL NORTH OF THE US/CANADA BORDER... AND A
SURFACE LOW ASSOCIATED WITH THE CUTOFF LOW CURRENTLY OVER THE
SOUTHWEST MOVES OUT OF THE SOUTHERN PLAINS TO THE OHIO VALLEY. WE
WILL FIND OURSELVES NESTLED BETWEEN THESE FEATURES... WITH BENIGN
WEATHER IN PLACE. A SLOWLY MOVING COLD FRONT WILL DROP SOUTH
THROUGH THE REGION WEDNESDAY INTO THURSDAY. THERE ARE SOME HINTS
WE COULD SEE MOISTURE POOL SUFFICIENTLY ALONG THIS BAROCLINIC ZONE
TO GET SOME PCPN DEPENDING UPON WHEN THE UPSTREAM SHORTWAVE
DROPPING SOUTHEAST FROM SOUTH CENTRAL CANADA IS ABLE TO CATCH UP
WITH IT. GIVEN UNCERTAINTIES IN NOT ONLY IF SOME PCPN WILL BE
SQUEEZED OUT... BUT WHEN AND WHERE IT MIGHT OCCUR... CHOSE TO
LEAVE PCPN OUT OF THE FORECAST IN THE WEDNESDAY TO THURSDAY TIME
FRAME... BUT FEEL THERE IS AT LEAST A CHANCE FOR SOME FLURRIES OF
VERY LIGHT SNOW DURING THAT PERIOD WHICH MAY GET INCLUDED AS WE
GET CLOSER TO THAT TIME PERIOD. THE MEDIUM RANGE GUIDANCE BECOMES
QUITE MUDDY IN ITS AGREEMENT BY WEEK/S END... WITH THE
DETERMINISTIC GFS AND ECMWF DIFFERING BY 15-20MB IN SURFACE
PRESSURES OVER OUR AREA BY FRIDAY AS THE GFS CLOSES OFF A SURFACE
LOW IN THE SAME AREA WHERE THE ECMWF SUGGESTS A FAIRLY POTENT
RIDGE. THE ECMWF SOLUTION WOULDN/T SUPPORT ANY PCPN... AND THE GFS
WOULD SUGGEST VERY LITTLE... SO THE PATH OF LEAST RESISTANCE AT
THIS POINT IS SIMPLY TO KEEP THINGS DRY.
&&
.AVIATION... /06Z TAF ISSUANCE/
/ISSUED 1135 PM CST SAT DEC 17 2011/
FEW PROBLEMS SEEN THIS TAF PERIOD AS A WARM FRONT IN THE DAKOTAS
MOVES EASTWARD ACROSS THE TAF SITES EARLY ON SUNDAY. SOME MINOR
VISIBILITY RESTRICTIONS OF 4-6SM BR POSSIBLE THROUGH DAYBREAK AT
KRNH AND KEAU BUT CONFIDENCE IS NOT HIGH WITH SCT-BKN CI/CS
DROPPING SOUTHEAST ACROSS THE AREA. SURFACE WINDS WILL INCREASE
TO 12-15 KNOTS AFTER 15Z ON SUNDAY WITH GUSTS FROM 18-23 KNOTS.
CONCERNS BEGIN AROUND 19/03Z AS A COLD FRONT BEGINS TO MOVE
SOUTH INTO CENTRAL MN. GUIDANCE IS SHOWING SOME POTENTIAL FOR
BKN010 IN THE WAKE OF THE FRONT FOR A FEW HOURS. TRAJECTORY
FORECASTS FROM NORTHWEST OF LAKE WINNIPEG...WHERE SOME MVFR
CEILINGS ARE LOCATED NOW...DO MAKE IT INTO NORTHWEST MN BY 19/03Z.
SO THERE IS SOME POTENTIAL THAT THIS SCENARIO COULD OCCUR.
HOWEVER...GIVEN THE TIME FRAME...CONFIDENCE IS LOW AND FEW-
SCT010-015 INSERTED INTO THE KAXN AND KSTC TAFS AS A START.
KMSP...LIGHT SOUTH WINDS OVERNIGHT WILL INCREASE TO 12 KNOTS WITH
GUSTS TO 18 KNOTS AFTER 16Z AND CONTINUE THROUGH THE AFTERNOON
BEFORE DIMINISHING AND BECOMING SOUTHWEST SUNDAY EVENING. A COLD
FRONT WILL PASS THE AIRPORT AROUND 19/07Z. SOME POTENTIAL FOR
BKN010-015 IN THE WAKE OF THE FRONT BETWEEN 07Z-12Z. CONFIDENCE IS
LOW AND INSERTED FEW015 IN THE TAF TO INDICATE THE POTENTIAL.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
TRH/RAH
AREA FORECAST DISCUSSION...UPDATED
NWS ST LOUIS MO
939 PM CST MON DEC 19 2011
.UPDATE...
/935 PM CST MON DEC 19 2011/
MADE SOME MINOR TWEEKS TO THE FORECAST FOR TONIGHT AND EARLY TUESDAY
MORNING...NAMELY TO TRIM BACK THE MENTION OF WINTRY PRECIPITATION
ACROSS NORTHERN PORTIONS OF THE CWA. THE LATEST UPPER AIR DATA AND
SURFACE OBS SHOW DEEPER COLD AIR TO SUPPORT A POTENTIAL WINTRY MIX
IS BETTER JUXTAPOSED WEST OF THE CWA. THE LATEST MODEL GUIDANCE
INCLUDING THE RUC AND HRRR SUPPORT THIS AS WELL WITH GREATER CAA
WEST OF THE CWA. IN FACT A MULTITUDE OF SOUNDINGS SHOW VERY LOW
POTENTIAL FOR ANY SNOW OR SLEET THRU 12Z. AS A RESULT I HAVE
TRIMMED BACK THE MENTION OF RAIN...SLEET...SNOW TO KNOX AND LEWIS
COUNTIES FOR LATE TONIGHT...AFTER 09Z. AFTER THIS TIME I CAN`T
RULE OUT THE POSSIBILITY BUT EVEN IN THESE FEW COUNTIES IT MAY BE
TOO WARM.
GLASS
&&
.DISCUSSION...
/358 PM CST MON DEC 19 2011/
PRIMARY CONCERN WITH THIS FCST PCKG IS PRECIP CHANCES AND PTYPE FOR
THE NEXT 7 DAYS.
ISENTROPIC ASCENT AHEAD OF A LOW PRESSURE SYSTEM LIFTING NEWD INTO
THE SRN PLAINS WAS PRODUCING A BROAD PCPN SHIELD THIS AFTN THAT
STRETCHED ACROSS MOST OF KS AND MO AND INTO THE SRN HALF OF IL.
AMPLE MOISTURE WILL BE AVAILABLE FOR PCPN WITH MODELS SHOWING A
STRONG LLJ TRANSPORTING A VERY MOIST AIR MASS /PWAT VALUES OF
AROUND 1 INCH WHICH IS 2 STANDARD DEVIATIONS ABOVE NORMAL FOR
DECEMBER IN THIS PART OF THE COUNTRY/ NWD INTO THE REGION. PCPN
SHOULD CONTINUE OVERNIGHT AND INCREASE IN COVERAGE AS THE UPPER
LOW APPROACHES AND LARGE SCALE LIFT INCREASES WITH SOME ADDITIONAL
ENHANCEMENT PROVIDED BY WEAK JET COUPLING. TEMPERATURE PROFILES
CONTINUE TO SUPPORT AN ALL-RAIN EVENT ACROSS ALL BUT THE FAR NRN
CWA WHERE A COLD FRONT WAS EDGING SWD OUT OF IA. THE FAR NRN CWA
WILL BE VERY CLOSE TO THE TRANSITION ZONE BETWEEN RAIN AND SNOW
AND BUFKIT PROFILES AS WELL AS PARTIAL THICKNESS METHODS SUGGEST
THAT SNOW AND SLEET MAY MIX WITH THE RAIN AT TIMES. AS THE SFC LOW
LIFTS OUT OF THE TX PANHANDLE TONIGHT AND TOMORROW...THE BOUNDARY
WILL BE LIFTED NWD AS A WARM FRONT AND PCPN SHOULD CHANGE BACK TO
RAIN. DRY SLOT EFFECTS MAY CAUSE PCPN TO FALL MORE AS DRIZZLE THAN
AS RAIN FOR THE SRN HALF OF THE CWA TOMORROW AND TOMORROW NIGHT.
FINALLY...COLD AIR WRAPPING AROUND THE BACK SIDE OF THE DEPARTING
SYSTEM MAY CAUSE SNOW TO MIX WITH RAIN ACROSS NWRN PARTS OF THE
CWA TOMORROW NIGHT. ATTM IT APPEARS THAT THE DEFORMATION ZONE WILL
REMAIN NORTH AND WEST OF THE CWA. BARRING ANY UNEXPECTED SHIFTS IN
THE TRACK OF THIS SYSTEM...LESS THAN A HALF INCH OF SNOW AND SLEET
ACCUMULATION IS EXPECTED ACROSS THE FAR NRN CWA.
MEANWHILE...WATER VAPOR IMAGERY SHOWED ANOTHER SHORTWAVE DROPPING
SWD ALONG THE CA COAST TOWARDS BAJA CALIFORNIA. MODELS ARE IN GOOD
AGREEMENT THAT THIS SYSTEM CLOSES OFF AND SLOWS DOWN BEFORE MOVING
THROUGH NRN MEXICO AND FINALLY LIFTING THROUGH ERN TX ON WED/THU IN
RESPONSE TO THE STRONGER SHORTWAVE REACHING THE WA/OR COAST ON TUE
NIGHT. THE SHORTWAVE CURRENTLY ALONG THE CA COAST IS NOT EXPECTED TO
PRODUCE ANY PCPN FOR OUR AREA AS IT LIFTS THROUGH THE SRN CONUS.
HOWEVER...MODELS SHOW THAT THE OTHER SYSTEM DEEPENS AFTER CROSSING
THE ROCKIES AND TAKES A TRACK THAT WOULD BE FAVORABLE FOR SNOWFALL
ACROSS MOST OF THE CWA. THERE ARE STILL SIGNIFICANT DIFFERENCES
BETWEEN THE GFS/ECMWF/GEM /ESPECIALLY WRT PHASING WITH NRN STREAM
SHORTWAVES/ AND BETTER MODEL AGREEMENT MIGHT NOT OCCUR UNTIL AFTER
THESE FEATURES HAVE BEEN SAMPLED BY THE UPPER AIR NETWORK.
KANOFSKY
&&
.AVIATION...
/512 PM CST MON DEC 19 2011/
RA IS EXPECTED TO CONTINUE THRU MUCH OF THE TAF PERIOD AS A STORM
SYSTEM APPROACHES THE REGION. VSBYS ARE EXPECTED TO REMAIN IN THE
LOW MVFR RANGE WITH CIGS EXPECTED TO LOWER TO AND REMAIN IN THE
IFR RANGE THRU MUCH OF THE PERIOD. WINDS ARE EXPECTED TO BE NLY AS
WRMFNT SETTLES JUST S OF TERMINALS. MAY SEE SOME IMPROVEMENT LATE
TUES AFTERNOON AS DRY SLOT MOVES INTO THE REGION. HOWEVER...THIS
IMPROVEMENT IS EXPECTED TO BE SHORT LIVED AS CIGS MAY DROP BACK
INTO THE IFR RANGE AS THE SFC LOW APPROACHES.
SPECIFICS FOR KSTL...RA IS EXPECTED TO CONTINUE THRU MUCH OF THE
TAF PERIOD AS A STORM SYSTEM APPROACHES THE REGION. VSBYS ARE
EXPECTED TO REMAIN IN THE LOW MVFR RANGE WITH CIGS EXPECTED TO
LOWER TO AND REMAIN IN THE IFR RANGE THRU MUCH OF THE PERIOD.
WINDS ARE EXPECTED TO BE NLY AS WRMFNT SETTLES JUST S OF
TERMINAL. MAY SEE SOME IMPROVEMENT LATE TUES AFTERNOON AS DRY
SLOT MOVES INTO THE REGION. HOWEVER...THIS IMPROVEMENT IS EXPECTED
TO BE SHORT LIVED AS CIGS MAY DROP BACK INTO THE IFR RANGE AS THE
SFC LOW APPROACHES.
TILLY
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
IL...NONE.
&&
$$
WFO LSX
AREA FORECAST DISCUSSION
NWS HASTINGS NE
603 PM CST MON DEC 19 2011
.AVIATION...00Z KGRI. A MID-LEVEL DECK OF CLOUDS SHOULD HANG
AROUND FOR THE ENTIRE FORECAST. WIND WILL GRADUALLY DECREASE WITH
TIME AND BY LATE TUESDAY AFTERNOON...BECOME LIGHT AND VARIABLE.
&&
.PREV DISCUSSION... /ISSUED 349 PM CST MON DEC 19 2011/
SHORT TERM...MORNING UPPER AIR ANALYSIS AND WATER VAPOR IMAGERY
INDICATE A MID AND UPPER LEVEL LOW OVER WEST TEXAS...MOVING NORTHEAST
INTO THE CENTRAL CONUS. WATER VAPOR IMAGERY ALSO INDICATES A MID
LEVEL DRY INTRUSION MOVING NORTHEASTWARD INTO NORTHERN TEXAS AND
PORTIONS OF OKLAHOMA. AT THE SURFACE AN AREA OF LOW PRESSURE EXISTS OVER
THE PANHANDLE OF TEXAS AND A SURFACE FRONT EXTENDS NORTHEAST FROM
THE SURFACE LOW INTO WESTERN AND NORTHERN OKLAHOMA...AS WELL AS
EASTERN KANSAS. KUEX INDICATES INCOMING PRECIPITATION OVER NORTH
CENTRAL KANSAS IN A ZONE OF LOW LEVEL THERMAL ADVECTION AND
RESULTANT ISENTROPIC UPGLIDE AND SATURATION. ADDITIONAL FORCING
THROUGH A ZONE OF MID LEVEL DIFFLUENCE IS ALSO HELPING PROMOTE
PRECIPITATION OVER AREAS NORTHEAST OF THE MID LEVEL LOW. SNOW IS
ALREADY IN PROGRESS AT NATOMA AS A RESULT.
THE LOW LEVEL BAROCLINIC ZONE CLEARED OUR CWA EARLIER TODAY AND
THE LOW LEVEL WIND FIELD ACROSS OUR CWA REMAINS FROM THE
NORTH/NORTHEAST AS A RESULT. SURFACE TEMPERATURES HAVE BEEN AT A
NEAR STANDSTILL IF NOT FALLING SOMEWHAT TODAY...WITH TEMPERATURES
AS OF MID AFTERNOON GENERALLY IN THE LOWER 30S. SHORT TERM GUIDANCE
CONTINUES TO SUGGEST THE MID LEVEL LOW WILL MOVE NORTHEAST ACROSS
THE SOUTHERN AND CENTRAL PLAINS TONIGHT AND TUESDAY. LOW LEVEL
THERMAL ADVECTION...WORKING IN CONCERT WITH MID LEVEL DIFFLUENCE AND
DEFORMATION TO THE NORTH AND NORTHEAST OF THE MID LEVEL LOW...WILL CONTINUE
PROMOTING PRECIPITATION PRODUCTION OVER THE AREA TONIGHT.
PRECIPITATION IS ALSO EXPECTED DURING THE DAY TUESDAY AS MID LEVEL
DEFORMATION TO THE NORTH AND NORTHWEST OF THE MID LEVEL LOW CLEARS
THE AREA.
MOISTURE THROUGH THE LOWER HALF OF THE TROPOSPHERIC COLUMN IS
EXPECTED TO REMAIN QUITE HIGH THROUGH THE NEXT 24 HOURS WITH 500MB
DEW POINTS IN EXCESS OF -25 DEGREES C AND 700MB DEW POINTS IN
EXCESS OF -10 DEGREES C ACROSS OUR SOUTH/SOUTHEAST. THESE MOISTURE
LEVELS...WORKING IN CONCERT WITH THE AFOREMENTIONED KINEMATIC
FORCING...SHOULD BE MORE THAN SUFFICIENT FOR SIGNIFICANT
PRECIPITATION PRODUCTION ACROSS OUR SOUTH AND SOUTHEAST TONIGHT AND
TOMORROW. QPF FIELDS FROM THE NAM...OPERATIONAL GFS...EC AND SREF-
MEAN ALL SUGGEST STORM TOTAL LIQUID PRECIPITATION AMOUNTS IN
EXCESS OF 0.80" ACROSS OUR SOUTH AND SOUTHEAST. SURFACE
TEMPERATURES WILL LIKELY FALL INTO THE UPPER AND MID 20S THROUGH
THE REMAINDER OF THE EVENT AND AS A RESULT WILL GO AHEAD AND
ASSUME A 10:1 SNOW-WATER RATIO TO START THE EVENT...WITH RATIOS
CLIMBING TO NEAR 13:1 BY TONIGHT AND TOMORROW. THIS YIELDS STORM
TOTAL SNOWFALL ACCUMULATIONS ON THE ORDER OF 5-12 INCHES ACROSS
OUR EXTREME SOUTH...AND STORM TOTAL SNOWFALL ACCUMULATIONS IN THE
1-5 INCH RANGE FARTHER NORTH.
LOW LEVEL PRESSURE RISES POST-FROPA HAVE PROMOTED AN INCREASED LOW
LEVEL PRESSURE GRADIENT TODAY...WITH SUSTAINED WINDS NEAR 20KTS
ACROSS MUCH OF THE CWA AS OF MID AFTERNOON. THESE CONDITIONS ARE EXPECTED
TO CONTINUE THROUGH THIS EVENING...WITH DIMINISHING WINDS EXPECTED
BY MIDNIGHT AS THE LOW LEVEL PRESSURE GRADIENT RELAXES. AS A
RESULT...THESE WINDS SHOULD REMAIN WELL BELOW BLIZZARD CRITERIA.
ALL THAT BEING SAID...THE INHERITED WINTER STORM WARNING FOR
ROOKS...OSBORNE AND MITCHELL COUNTIES...ALONG WITH THE WINTER
WEATHER ADVISORY FOR PHILLIPS...SMITH AND JEWELL COUNTIES...APPEAR
TO BE RIGHT ON...BUT DID GO AHEAD AND START THE WINTER STORM
WARNING NOW GIVEN SNOWFALL IS ALREADY OCCURRING AT NATOMA.
JUST A FEW THINGS TO CONSIDER AS WE HEAD INTO THIS STORM. THE
CONTRAST BETWEEN MOIST AIR AND DRY AIR...AS WELL AS BETWEEN STRONG
KINEMATIC FORCING AND NEXT TO NO FORCING...IS EXPECTED TO BE RATHER
SHARP THUS RESULTING IN A VERY TIGHT GRADIENT OF STORM TOTAL
SNOWFALL ACCUMULATIONS. ALTHOUGH CONFIDENCE REMAINS HIGH REGARDING
ACTUAL STORM TOTAL SNOWFALL ACCUMULATIONS...THE AXIS OF HEAVIEST
SNOW COULD SHIFT DRAMATICALLY IN RESPONSE TO VERY SMALL DEVIATIONS
IN STORM PATH. THANKFULLY...GUIDANCE HAS REMAINED FAIRLY
CONSISTENT WITH RESPECT TO STORM PATH...A TREND WHICH WE HOPE WILL
CONTINUE. FINALLY...GUIDANCE DOES SUGGEST THE MID LEVEL DRY
INTRUSION WILL INFILTRATE MUCH OF KANSAS BY TUESDAY MORNING...THUS
DRYING OUT THE DENDRITIC LAYER AND LIKELY LEADING TO A PERIOD OF
FREEZING DRIZZLE. AT THIS TIME IT APPEARS THIS MID LEVEL DRY
INTRUSION SHOULD REMAIN SOUTH AND SOUTHEAST OF OUR AREA AND AS A
RESULT...LEFT ANY MENTION OF FREEZING DRIZZLE OUT OF THE FORECAST.
LONG TERM...TUESDAY NIGHT THROUGH MONDAY. THE UPPER LOW WILL
CONTINUE TO MOVE NORTHEAST AND AWAY FROM THE AREA TUESDAY NIGHT.
THE MAJORITY OF MODEL SOLUTIONS SUGGESTS THE SNOW SHOULD BE DONE BY
TUESDAY NIGHT...AND WILL CONTINUE TO CARRY A DRY FORECAST.
A BRIEF H5 RIDGE BUILDS IN TUESDAY NIGHT INTO WEDNESDAY...WHICH
SHOULD KEEP IT DRY THROUGH WEDNESDAY...HOWEVER ANOTHER UPPER
TROUGH/LOW BEGINS TO APPROACH THE REGION WEDNESDAY NIGHT. THE
NAM/GFS/ECMWF ALL AGREE THAT MOST OF WEDNESDAY EVENING SHOULD REMAIN
DRY...HOWEVER LIGHT SNOW COULD BEGIN TO APPROACH FAR NORTH AND WEST
PORTIONS OF THE FORECAST AREA BY LATE EVENING. THE SNOW CHANCES
WILL THEN SPREAD ACROSS THE FORECAST AREA OVERNIGHT WEDNESDAY INTO
THURSDAY. THE NAM/GFS DEPICT THE STRONGEST LIFT/FORCING ACROSS
ROUGHLY THE SOUTHERN HALF OF THE CWA LATE WEDNESDAY NIGHT INTO
THURSDAY...AND HAVE INCREASED POPS FOR THAT AREA...ESPECIALLY FOR
THURSDAY. SNOW AMOUNTS ARE STILL UNCERTAIN...AND SREF 12 HOUR SNOW
PROBABILITIES FOR AN INCH OR MORE OF SNOW ARE NOT VERY HIGH...THOUGH
THE HIGHER PROBABILITIES ARE SHOWN IN THE SOUTH AND WEST.
ONE CONCERN IS THE POTENTIAL FOR HIGHER SNOW RATIOS WITH THE CARIBOU
SNOW TECHNIQUE SUGGESTING RATIOS CLIMBING TO NEAR 18 TO 1 FOR
THURSDAY AFTERNOON. FOR NOW...WILL GO WITH A GENERAL HALF INCH TO
INCH AND A HALF...WITH THE HIGHER AMOUNTS IN THE SOUTH AND WEST.
THERE IS STILL PLENTY OF TIME TO REFINE AMOUNTS AS THIS NEXT SYSTEM
GETS CLOSER.
OVERALL...THE CHRISTMAS HOLIDAY WEEKEND LOOKS TO BE FAIRLY QUIET.
ANOTHER WAVE COULD MOVE ACROSS THE REGION SATURDAY NIGHT INTO
CHRISTMAS DAY...BUT MOISTURE IS LACKING SO IT SHOULD PASS THROUGH
DRY. TEMPERATURES ARE EXPECTED TO BE FAIRLY SEASONABLE WITH HIGHS
PRIMARILY IN THE 30S.
PREV DISCUSSION... /ISSUED 1120 AM CST MON DEC 19 2011/
AVIATION...18Z TAF. IFR CEILINGS HAVE MOVED INTO PARTS OF SOUTH
CENTRAL NEBRASKA BEHIND A COLD FRONT THAT TRAVELED ACROSS THE
AREA EARLIER TODAY. THE GENERAL TREND HAS BEEN FOR THE IFR
CEILINGS TO LIFT TO MVFR...AND THIS IS ALSO SHOWN BY THE LATEST
NAM PROXIMITY SOUNDINGS..SO WILL ONLY CARRY THE LOWER CEILINGS IN
A BRIEF TEMPO GROUP. PROXIMITY SOUNDINGS ALSO SHOW THE MVFR
CEILINGS IMPROVING THIS AFTERNOON...THOUGH THE RUC IS FASTER IN
LIFTING THE CEILINGS THAN THE NAM. WILL AIM FOR MORE OF A
COMPROMISE SOLUTION AND GO WITH 21Z AS A START. WINDS WILL REMAIN
GUSTY AND FROM THE NORTH MOST OF THE AFTERNOON...BUT THEY SHOULD
DIMINISH THIS EVENING. THERE WILL BE CHANCES OF SNOW SOUTH OF
KGRI AS A STORM SYSTEM MOVES ACROSS THE CENTRAL AND SOUTHERN
PLAINS...BUT THINK THAT THE CHANCES WILL STAY FAR ENOUGH SOUTH TO
KEEP THE MENTION OUT OF THE FORECAST AT KGRI.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR KSZ005>007.
WINTER STORM WARNING UNTIL 6 PM CST TUESDAY FOR KSZ017>019.
&&
$$
SHORT TERM...BRYANT
AVIATION...HEINLEIN
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
1232 AM EST SUN DEC 18 2011
.SYNOPSIS...
MUCH COLDER TEMPERATURES CONTINUE FOR THE OVERNIGHT HOURS AS
TEMPERATURES DROP INTO THE SINGLE DIGITS ABOVE AND BELOW ZERO.
LOCALIZED LAKE CHAMPLAIN LAKE EFFECT SNOW SHOWERS WILL BE
POSSIBLE TONIGHT...WITH SOME LIGHT ACCUMULATION ACROSS THE
CHAMPLAIN VALLEY. MAINLY CLEAR SKIES WILL CONTINUE FOR
SUNDAY...BEFORE A WEAK WARM FRONT PRODUCES SOME CLOUDS AND A
CHANCE OF SNOW SHOWERS LATE SUNDAY INTO MONDAY.
&&
.NEAR TERM /UNTIL 7 AM THIS MORNING/...
AS OF 1230 AM EST SUNDAY...FCST IN GREAT SHAPE THIS MORNING WITH
ONE MINOR CHANGE. HAVE DECREASE TEMPS BY SEVERAL DEGREES ACRS
NORTHERN NY PER LATEST OBS. SLK ALREADY AT -3F AND MSS AT
+2F...THINKING NEAR -10F FOR SLK AND -4F FOR MSS...WITH SINGLE
DIGITS ABOVE ZERO FOR THE CPV AND NEAR ZERO FOR PARTS OF CENTRAL AND
NORTHERN VT...WITH NEAR 10F FOR SOUTHERN VT. OTHERWISE...STILL
WATCHING SOME WEAK LAKE CHAMPLAIN ACTIVITY PER LATEST RADAR...BUT
OVERALL INTENSITY/COVERAGE IS LIMITED DUE TO LLVL DRY AIR AND WIND
SHEAR PER LATEST VAD FROM KCXX. THINKING A DUSTING OR SO WL STILL
BE POSSIBLE NEAR LAKE CHAMPLAIN BY MORNING AND WL CONT TO MENTION
SCHC TO CHC POPS IN A NARROW BAND. REST OF FCST IN GREAT.
MINOR UPDATE TO SNOW SHOWER/FLURRY CHANCES ALONG LAKE CHAMPLAIN
THROUGH THE REMAINDER OF THE NIGHT. LOWERING INVERSION HEIGHT AND
DRY AIR ADVECTION SHOULD LIMIT ACTIVITY TO MAINLY VERY LIGHT
ACTIVITY WITH LITTLE MORE THAN A DUSTING OVERNIGHT IN FAVORED
AREAS FROM SHELBURNE TO CHARLOTTE...FERRISBURGH AND THE WESTERN
LAKESHORE IN ESSEX COUNTY NEW YORK FROM WILLSBORO TO WESTPORT.
REST OF FCST UNCHANGED.
PRIOR DISCUSSION FROM 622 PM EST SATURDAY...
FORECAST ESSENTIALLY ON TRACK FOR THIS EVENING AND HAVE MADE ONLY
MODEST ADJUSTMENTS TO SKY COVER THROUGH THE EVENING/OVERNIGHT
HOURS BASED OFF IR SATELLITE DATA AND RUC13 850 HPA RH PROGS. THIS
WOULD SUGGEST SKIES TO REMAIN PTLY CLOUDY THROUGH MIDNIGHT OR
SO...THEN TRENDING MAINLY CLEAR IN MOST AREAS BY MORNING OUTSIDE
IMMEDIATE VCNTY OF LAKE CHAMPLAIN. RECENT AIRCRAFT DATA OUT OF
PIERRE TRUDEAU APT IN MONTREAL CONFIRM RUC/NAM/GFS 850 HPA TEMPS
OF AROUND -18C...SO SEE NO REASON TO DISCOUNT PRESENT CHILLY LOW
TEMP FORECAST IN THE -7 TO +7F RANGE BY SUNDAY MORNING...SLIGHTLY
MILDER SOUTH. IN REGARD TO THE CHAMPLAIN LAKE EFFECT...EVOLVING
NORTHERLY TRAJECTORIES AND LAKE-850 HPA AIR TEMP DIFFERENCE NEAR
24C MORE THAN SUFFICIENT TO ALLOW PERIODIC SNOW SHOWERS/FLURRIES
TO CONTINUE OVERNIGHT TO THE SOUTH AND EAST OF THE LAKE. LIMITING
FACTORS INCLUDING SHALLOW BOUNDARY LAYER AND DRY AIR ADVECTION
SHOULD PRECLUDE ANYTHING SUBSTANTIAL HOWEVER. AGAIN...PRESENT FCST
HAS THIS COVERED SO OTHER THAN SKY ADJUSTMENTS NOTED ABOVE...NO
OTHER CHANGES NEEDED AT THIS TIME. ENJOY YOUR EVENING.
&&
.SHORT TERM /7 AM THIS MORNING THROUGH MONDAY NIGHT/...
AS OF 300 PM EST SATURDAY...MID/UPPER LEVEL RIDGE BUILDS ACROSS
OUR CWA AS SURFACE HIGH PRESSURE SHIFTS TOWARD EASTERN NEW
ENGLAND. GIVEN DEEP DRY LAYER AND PLENTY OF NVA FROM BUILDING
HGHTS...EXPECT MAINLY CLEAR SKIES WITH MAX TEMPS ON SUNDAY AROUND
TEN DEGREES BELOW NORMAL. TEMPS RETURN TO NEAR NORMAL BY SUNDAY
NIGHT AS 850 TEMPS SLOWLY WARM FROM THE NEGATIVE TEENS ON SUNDAY
TO NEGATIVE SINGLE DIGITS SUNDAY NIGHT. MONDAY WILL BEGIN DRY
WITH HIGH PRESSURE STILL IN PLAY...BUT BY LATE MONDAY...ANOTHER
SFC COLD FRNT APPROACHES OUR WESTERN CWA. WITH A GOOD RIBBON OF
850 TO 500MB MOISTURE AND STRONG SFC CONVERGENCE. THIS COMBINED
WITH STEEP 0 TO 2 KM AGL LAPSE RATES...AND POTENTIAL FOR SOME
LAKE MOISTURE INTERACTION...A BAND OF SNOW SHOWERS AND SNOW
SQUALLS LOOKS POSSIBLE LATE MONDAY AFTN INTO MONDAY NIGHT. WINDS
ALSO LOOK STRONG ON MONDAY AS 850 JET PEAKS AROUND 60 KTS DURING
THE AFTERNOON. HAVE CONTINUED WITH MENTION OF LIKELY POPS ACROSS
NORTHERN NY/VT BY 00Z...WITH A QUICK INCH OR TWO OF SNOW
POSSIBLE. TEMPERATURES WILL WARM BACK INTO THE 30S TO NEAR 40F ON
MONDAY...ASSOCIATED WITH SOUTHERLY FLOW AHEAD OF BOUNDARY.
OVERNIGHT MIN TEMPS WILL BE SLIGHTLY WARMER THAN NORMAL WITH
RESIDUAL CLOUDS FROM FRONT AND WINDS PROMOTING MIXING.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 247 PM EST SATURDAY...THE EXTENDED FCST PERIOD STARTS QUIET
AS SFC RIDGE OF HIGH PRESSURE CRESTS OVER NY AND NEW ENGLAND ON
TUESDAY. SHOULD SEE MOSTLY SUNNY SKIES TUESDAY WITH LIGHT WINDS
AND SEASONABLY TEMPS /HIGHS IN THE UPR 20S TO LOWER 30S/. RIDGE
AXIS SHIFTS EAST TUESDAY NIGHT WITH DEVELOPING S-SW WINDS. MAY
SEE TEMPS LEVELING OUT IN THE CHAMPLAIN AND ST. LAWRENCE VALLEYS
WITH INCREASED MIXING AND DEVELOPING WARM ADVECTION REGIME.
MODELS HAVE DIVERGED COMPARED TO PREVIOUS RUNS FOR POTENTIAL
PRECIPITATION SYSTEM WEDNESDAY INTO WEDNESDAY NIGHT. THE 12Z GFS
AND ECMWF SOLNS SHOW THAT THE NORTHERN AND SOUTHERN STREAMS ARE
NO LONGER IN PHASE...WITH SRN STREAM SHORTWAVE TROUGH PRECEDING
NORTHERN STREAM AS VORT MAX EMERGES FROM THE OHIO RIVER VALLEY.
THE 12Z GFS IS A BIT FASTER...WITH VORT PASSING THRU PA AND THEN
OFFSHORE SOUTH OF LONG ISLAND. THE BULK OF ASSOCIATED
PRECIPITATION REMAINS SOUTH OF THE NORTH COUNTRY AS WELL. HIGHEST
POPS WOULD OCCUR LATE TUESDAY NIGHT INTO WEDNESDAY. THE ECMWF IS
ABOUT 12 HRS SLOWER AND WARMER ALOFT...WITH 850MB TEMPS +5C AT
00Z THU. HAVE CUT BACK ON POPS TO 30-40 PERCENT...AND HAVE
INDICATED MIXED PRECIPITATION TYPES BASED. NOT EXPECTING A LOT OF
QPF AT THIS POINT BASED ON ABSENCE OF PHASING AND GFS TRACK. WILL
CONTINUE TO MONITOR...BUT SIGNIFICANT WEATHER IMPACTS LOOK LESS
LIKELY THAN THIS TIME YESTERDAY.
THE 12Z GFS MAINTAINS A MORE SIGNIFICANT UPPER TROUGH LATE NEXT
WEEK AND OFFERS A COLDER SOLN THU-FRI AS COMPARED TO THE ECMWF.
HAVE MADE SOME ADJUSTMENTS BETWEEN THE TWO MODELS...INDICATING
HIGHS MOSTLY IN THE 30S WITH LOWS IN THE 20S...SO SOMEWHAT ABOVE
CLIMO ON TEMPS. CAN`T RULE OUT SOME SNOW SHOWER ACTIVITY
THU/FRI...BUT OVERALL NO SIGNIFICANT WEATHER EXPECTED AT THIS
TIME.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
THROUGH 06Z MONDAY...MAINLY VFR CONDITIONS EXPECTED THROUGH THE
PERIOD...EXCEPT FOR POSSIBLE MVFR AT KBTV/KSLK THROUGH 12Z. PATCHY
BR POSSIBLE AT KSLK...WHILE CLOUDS ASSOCIATED WITH SNOW SHOWERS
OVER LAKE CHAMPLAIN MAY DRIFT OVER KBTV AT TIMES. OTHERWISE...
MAINLY CLEAR SKIES THROUGH SUNDAY...WITH INCREASING CLOUDS SUNDAY
NIGHT. WINDS LIGHT AND VARIABLE...THEN BECOMING SSW 5-10 KTS OVER
NORTHERN NY SUNDAY AFTERNOON AND OVER VT SUNDAY NIGHT.
OUTLOOK 06Z MONDAY THROUGH THURSDAY...HIGH PRESSURE BRINGS MAINLY
VFR CONDITIONS THRU 18Z MONDAY. COLD FRONT MONDAY AFTERNOON INTO
MONDAY NIGHT MAY BRING LOCALLY GUSTY W-NW WINDS TO 25 KTS AND
SCATTERED SNOW SHOWERS WITH A PERIOD OF MVFR OR BRIEF IFR
CONDITIONS. NEXT PRECIPITATION SYSTEM ARRIVES LATE TUESDAY NIGHT
INTO WEDNESDAY...THOUGH CURRENT INDICATIONS ARE THAT BULK OF
PRECIPITATION WILL SLIDE SOUTH OF THE NORTH COUNTRY. A PERIOD OF
SNOW OR MIXED PCPN IS EXPECTED TO BE LIGHT AT THIS TIME.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.
&&
$$
SYNOPSIS...NEILES
NEAR TERM...JMG/TABER
SHORT TERM...NEILES
LONG TERM...BANACOS
AVIATION...RJS/LOCONTO
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
1230 AM EST SUN DEC 18 2011
.SYNOPSIS...
MUCH COLDER TEMPERATURES CONTINUE FOR THE OVERNIGHT HOURS AS
TEMPERATURES DROP INTO THE SINGLE DIGITS ABOVE AND BELOW ZERO.
LOCALIZED LAKE CHAMPLAIN LAKE EFFECT SNOW SHOWERS WILL BE
POSSIBLE TONIGHT...WITH SOME LIGHT ACCUMULATION ACROSS THE
CHAMPLAIN VALLEY. MAINLY CLEAR SKIES WILL CONTINUE FOR
SUNDAY...BEFORE A WEAK WARM FRONT PRODUCES SOME CLOUDS AND A
CHANCE OF SNOW SHOWERS LATE SUNDAY INTO MONDAY.
&&
.NEAR TERM /UNTIL 7 AM THIS MORNING/...
AS OF 927 PM EST SATURDAY...MINOR UPDATE TO SNOW SHOWER/FLURRY
CHANCES ALONG LAKE CHAMPLAIN THROUGH THE REMAINDER OF THE NIGHT.
LOWERING INVERSION HEIGHT AND DRY AIR ADVECTION SHOULD LIMIT
ACTIVITY TO MAINLY VERY LIGHT ACTIVITY WITH LITTLE MORE THAN A
DUSTING OVERNIGHT IN FAVORED AREAS FROM SHELBURNE TO
CHARLOTTE...FERRISBURGH AND THE WESTERN LAKESHORE IN ESSEX COUNTY
NEW YORK FROM WILLSBORO TO WESTPORT. REST OF FCST UNCHANGED.
PRIOR DISCUSSION FROM 622 PM EST SATURDAY...
FORECAST ESSENTIALLY ON TRACK FOR THIS EVENING AND HAVE MADE ONLY
MODEST ADJUSTMENTS TO SKY COVER THROUGH THE EVENING/OVERNIGHT
HOURS BASED OFF IR SATELLITE DATA AND RUC13 850 HPA RH PROGS. THIS
WOULD SUGGEST SKIES TO REMAIN PTLY CLOUDY THROUGH MIDNIGHT OR
SO...THEN TRENDING MAINLY CLEAR IN MOST AREAS BY MORNING OUTSIDE
IMMEDIATE VCNTY OF LAKE CHAMPLAIN. RECENT AIRCRAFT DATA OUT OF
PIERRE TRUDEAU APT IN MONTREAL CONFIRM RUC/NAM/GFS 850 HPA TEMPS
OF AROUND -18C...SO SEE NO REASON TO DISCOUNT PRESENT CHILLY LOW
TEMP FORECAST IN THE -7 TO +7F RANGE BY SUNDAY MORNING...SLIGHTLY
MILDER SOUTH. IN REGARD TO THE CHAMPLAIN LAKE EFFECT...EVOLVING
NORTHERLY TRAJECTORIES AND LAKE-850 HPA AIR TEMP DIFFERENCE NEAR
24C MORE THAN SUFFICIENT TO ALLOW PERIODIC SNOW SHOWERS/FLURRIES
TO CONTINUE OVERNIGHT TO THE SOUTH AND EAST OF THE LAKE. LIMITING
FACTORS INCLUDING SHALLOW BOUNDARY LAYER AND DRY AIR ADVECTION
SHOULD PRECLUDE ANYTHING SUBSTANTIAL HOWEVER. AGAIN...PRESENT FCST
HAS THIS COVERED SO OTHER THAN SKY ADJUSTMENTS NOTED ABOVE...NO
OTHER CHANGES NEEDED AT THIS TIME. ENJOY YOUR EVENING.
&&
.SHORT TERM /7 AM THIS MORNING THROUGH MONDAY NIGHT/...
AS OF 300 PM EST SATURDAY...MID/UPPER LEVEL RIDGE BUILDS ACROSS
OUR CWA AS SURFACE HIGH PRESSURE SHIFTS TOWARD EASTERN NEW
ENGLAND. GIVEN DEEP DRY LAYER AND PLENTY OF NVA FROM BUILDING
HGHTS...EXPECT MAINLY CLEAR SKIES WITH MAX TEMPS ON SUNDAY AROUND
TEN DEGREES BELOW NORMAL. TEMPS RETURN TO NEAR NORMAL BY SUNDAY
NIGHT AS 850 TEMPS SLOWLY WARM FROM THE NEGATIVE TEENS ON SUNDAY
TO NEGATIVE SINGLE DIGITS SUNDAY NIGHT. MONDAY WILL BEGIN DRY
WITH HIGH PRESSURE STILL IN PLAY...BUT BY LATE MONDAY...ANOTHER
SFC COLD FRNT APPROACHES OUR WESTERN CWA. WITH A GOOD RIBBON OF
850 TO 500MB MOISTURE AND STRONG SFC CONVERGENCE. THIS COMBINED
WITH STEEP 0 TO 2 KM AGL LAPSE RATES...AND POTENTIAL FOR SOME
LAKE MOISTURE INTERACTION...A BAND OF SNOW SHOWERS AND SNOW
SQUALLS LOOKS POSSIBLE LATE MONDAY AFTN INTO MONDAY NIGHT. WINDS
ALSO LOOK STRONG ON MONDAY AS 850 JET PEAKS AROUND 60 KTS DURING
THE AFTERNOON. HAVE CONTINUED WITH MENTION OF LIKELY POPS ACROSS
NORTHERN NY/VT BY 00Z...WITH A QUICK INCH OR TWO OF SNOW
POSSIBLE. TEMPERATURES WILL WARM BACK INTO THE 30S TO NEAR 40F ON
MONDAY...ASSOCIATED WITH SOUTHERLY FLOW AHEAD OF BOUNDARY.
OVERNIGHT MIN TEMPS WILL BE SLIGHTLY WARMER THAN NORMAL WITH
RESIDUAL CLOUDS FROM FRONT AND WINDS PROMOTING MIXING.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 247 PM EST SATURDAY...THE EXTENDED FCST PERIOD STARTS QUIET
AS SFC RIDGE OF HIGH PRESSURE CRESTS OVER NY AND NEW ENGLAND ON
TUESDAY. SHOULD SEE MOSTLY SUNNY SKIES TUESDAY WITH LIGHT WINDS
AND SEASONABLY TEMPS /HIGHS IN THE UPR 20S TO LOWER 30S/. RIDGE
AXIS SHIFTS EAST TUESDAY NIGHT WITH DEVELOPING S-SW WINDS. MAY
SEE TEMPS LEVELING OUT IN THE CHAMPLAIN AND ST. LAWRENCE VALLEYS
WITH INCREASED MIXING AND DEVELOPING WARM ADVECTION REGIME.
MODELS HAVE DIVERGED COMPARED TO PREVIOUS RUNS FOR POTENTIAL
PRECIPITATION SYSTEM WEDNESDAY INTO WEDNESDAY NIGHT. THE 12Z GFS
AND ECMWF SOLNS SHOW THAT THE NORTHERN AND SOUTHERN STREAMS ARE
NO LONGER IN PHASE...WITH SRN STREAM SHORTWAVE TROUGH PRECEDING
NORTHERN STREAM AS VORT MAX EMERGES FROM THE OHIO RIVER VALLEY.
THE 12Z GFS IS A BIT FASTER...WITH VORT PASSING THRU PA AND THEN
OFFSHORE SOUTH OF LONG ISLAND. THE BULK OF ASSOCIATED
PRECIPITATION REMAINS SOUTH OF THE NORTH COUNTRY AS WELL. HIGHEST
POPS WOULD OCCUR LATE TUESDAY NIGHT INTO WEDNESDAY. THE ECMWF IS
ABOUT 12 HRS SLOWER AND WARMER ALOFT...WITH 850MB TEMPS +5C AT
00Z THU. HAVE CUT BACK ON POPS TO 30-40 PERCENT...AND HAVE
INDICATED MIXED PRECIPITATION TYPES BASED. NOT EXPECTING A LOT OF
QPF AT THIS POINT BASED ON ABSENCE OF PHASING AND GFS TRACK. WILL
CONTINUE TO MONITOR...BUT SIGNIFICANT WEATHER IMPACTS LOOK LESS
LIKELY THAN THIS TIME YESTERDAY.
THE 12Z GFS MAINTAINS A MORE SIGNIFICANT UPPER TROUGH LATE NEXT
WEEK AND OFFERS A COLDER SOLN THU-FRI AS COMPARED TO THE ECMWF.
HAVE MADE SOME ADJUSTMENTS BETWEEN THE TWO MODELS...INDICATING
HIGHS MOSTLY IN THE 30S WITH LOWS IN THE 20S...SO SOMEWHAT ABOVE
CLIMO ON TEMPS. CAN`T RULE OUT SOME SNOW SHOWER ACTIVITY
THU/FRI...BUT OVERALL NO SIGNIFICANT WEATHER EXPECTED AT THIS
TIME.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
THROUGH 06Z MONDAY...MAINLY VFR CONDITIONS EXPECTED THROUGH THE
PERIOD...EXCEPT FOR POSSIBLE MVFR AT KBTV/KSLK THROUGH 12Z. PATCHY
BR POSSIBLE AT KSLK...WHILE CLOUDS ASSOCIATED WITH SNOW SHOWERS
OVER LAKE CHAMPLAIN MAY DRIFT OVER KBTV AT TIMES. OTHERWISE...
MAINLY CLEAR SKIES THROUGH SUNDAY...WITH INCREASING CLOUDS SUNDAY
NIGHT. WINDS LIGHT AND VARIABLE...THEN BECOMING SSW 5-10 KTS OVER
NORTHERN NY SUNDAY AFTERNOON AND OVER VT SUNDAY NIGHT.
OUTLOOK 06Z MONDAY THROUGH THURSDAY...HIGH PRESSURE BRINGS MAINLY
VFR CONDITIONS THRU 18Z MONDAY. COLD FRONT MONDAY AFTERNOON INTO
MONDAY NIGHT MAY BRING LOCALLY GUSTY W-NW WINDS TO 25 KTS AND
SCATTERED SNOW SHOWERS WITH A PERIOD OF MVFR OR BRIEF IFR
CONDITIONS. NEXT PRECIPITATION SYSTEM ARRIVES LATE TUESDAY NIGHT
INTO WEDNESDAY...THOUGH CURRENT INDICATIONS ARE THAT BULK OF
PRECIPITATION WILL SLIDE SOUTH OF THE NORTH COUNTRY. A PERIOD OF
SNOW OR MIXED PCPN IS EXPECTED TO BE LIGHT AT THIS TIME.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.
&&
$$
SYNOPSIS...NEILES
NEAR TERM...JMG
SHORT TERM...NEILES
LONG TERM...BANACOS
AVIATION...RJS/LOCONTO
AREA FORECAST DISCUSSION
NWS BISMARCK ND
1147 PM CST SAT DEC 17 2011
.DISCUSSION...CURRENT FORECAST REMAINS ON TRACK TONIGHT WITH
MOSTLY CLEAR SKIES...SCATTERED CIRRUS FILTERING THROUGH FROM
MONTANA AND SASKATCHEWAN INTO NORTH DAKOTA. MADE MINOR CHANGES TO
OVERNIGHT LOWS BY WARMING A COUPLE DEGREES IN THE SOUTHWEST PER
LATEST HOURLY TEMPS AND RUC DATA. MAIN THEME REST OF TONIGHT WILL
BE WATCHING A WARM FRONT NOW OVER WESTERN NORTH DAKOTA SLIDE EAST.
WARM AIR ADVECTION LOOKS TO CONTINUE THROUGH SUNDAY MORNING...THEN A
TRANSITION TO COLD AIR ADVECTION WILL COMMENCE FROM NORTHWEST TO
SOUTHEAST BETWEEN 18Z SUNDAY AND 03Z MONDAY AS A COLD FRONT SWEEPS
THROUGH. EXPECT DRY WEATHER...BUT BREEZY CONDITIONS DEVELOPING AS
THE FRONT MOVES THROUGH.
&&
.AVIATION...HIGH PRESSURE WILL REMAIN OVERHEAD TONIGHT...WHICH WILL
KEEP WEST TO SOUTHWEST WINDS AND VFR CONDITIONS THROUGH 12Z TOMORROW
MORNING. WINDS WILL START TO INCREASE AND SHIFT TO THE WEST TOMORROW
MORNING AS A LOW PRESSURE SYSTEM AND COLD FRONT APPROACHES THE REGION.
CEILINGS WILL START TO LOWER AFTER 18Z AS A MVFR CLOUD DECK SPREADS
FROM THE NORTHWEST TO SOUTHEAST AHEAD OF THE COLD FRONT.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...KS
AVIATION....LTH
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
550 AM EST SUN DEC 18 2011
.SYNOPSIS...
HIGH PRESSURE TODAY INTO MONDAY. EAST/WEST FRONT DROPS SOUTH MONDAY
NIGHT...BECOMES STATIONARY BY TUESDAY MORNING IN NORTHERN WEST
VIRGINIA INTO CENTRAL OHIO...THEN CREEPS BACK NORTH IN AFTERNOON.
&&
.NEAR TERM /THROUGH TONIGHT/...
NO MAJOR CHANGES AT 545 AM.
PREVIOUS DISCUSSION...
VORT MAX ALONG BACK EDGE OF H500 TROUGH SHOWING UP WELL ON WATER
VAPOR LOOP...NOW IN THE TRI-STATE AREA. RUC13 HAS A GOOD HANDLE ON
THIS...BRINGING THE LOBE EAST OF CRW BY 12Z...AND ACROSS THE
MOUNTAINS BY 15Z. BACK EDGE OF LIGHT SNOW WILL FOLLOW THIS...UNTIL
ONLY A FEW SCATTERED UPSLOPE SHSN REMAIN BY MIDMORNING. HAVE NOT
RECEIVED MANY SNOW REPORTS BUT EXPECT ACCUMULATIONS ARE GENERALLY AN
INCH OR LESS AT THIS POINT. FAVORABLE SNOW GROWTH CONDITIONS WILL BE
DIMINISHING AS MOISTURE IN THE DGZ DECREASES. ADDITIONAL MINOR
ACCUMULATION OF LESS THAN AN INCH IS POSSIBLE...MAINLY IN THE
NORTHERN MOUNTAINS...WITH A BIT OF AN UPSLOPE ASSIST. A FEW
FLURRIES MAY LINGER INTO EARLY AFTERNOON IN THE NORTHERN MOUNTAINS
BEFORE ENDING. CLOUDS WILL BE BREAKING IN THE WEST AS ANTICYCLONIC
FLOW TAKES HOLD.
SURFACE HIGH PRESSURE CROSSES BY TO OUR SOUTH THIS EVENING...AND
MOVES TOWARD THE CAROLINA COAST BY 12Z MONDAY. AFTER A CLEAR START
TO THE NIGHT...SOME MID AND HIGH CLOUDS WILL START SHOWING UP LATE
IN THE DEVELOPING SW RETURN FLOW. WARM ADVECTION IS FAIRLY GENTLE
OVERNIGHT AND STICKING WITH A NORMAL DIURNAL TEMPERATURE TREND FOR
NOW.
LEANED A BIT MORE TOWARD THE COOLER MAV TODAY...HAVING PERFORMED
BETTER YESTERDAY. WARMER MET LOOKS MORE REASONABLE TONIGHT IN THE
DEVELOPING WARM ADVECTION.
&&
.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
NO MAJOR CHANGES MADE TO MONDAY ON THIS SUNDAY MORNING GRAVEYARD
SHIFT. CLOUDS INCREASE ACROSS OUR WESTERN AND NORTHERN
COUNTIES...WITH SUNSHINE HOLDING THE LONGEST IN SOUTHWEST VIRGINIA
AND SOUTHEAST WEST VIRGINIA. POPS INCREASING QUICKLY ACROSS
SOUTHEAST OHIO DURING THE AFTERNOON.
HAVE LIKELY POPS FOR PCPN MONDAY NIGHT...MAINLY N OF HTS-CRW-EKN
LINE.
BASING THE FORECAST ON THE FRONT STILL SAGGING SOUTH MONDAY
NIGHT...REACHING NEAR A ROUTE 50 CORRIDOR BY 12Z TUESDAY BEFORE
TRYING TO LIFT SLOWLY BACK NORTH TUESDAY AFTERNOON...AHEAD OF
SURFACE LOW PRESSURE MOVING NORTHEAST UP THE OHIO RIVER VALLEY
TUESDAY NIGHT INTO WEDNESDAY.
FOR ABOUT A 6 HOUR WINDOW ON EITHER SIDE OF 12Z TUESDAY...WILL HAVE
THE POSSIBILITY OF A WINTRY MIXTURE OF RAIN...SNOW...SLEET...FROM
THE EKN VCNTY TO CKB-PKB AND NORTH OF UNI. FORECASTING THE SURFACE
TEMPERATURES IN THE 34/35 DEGREE NEIGHBORHOOD IN THAT TIME
INTERVAL FOR NORTHERN COUNTIES...SO DO NOT HAVE READINGS BELOW
FREEZING. OF COURSE...IN THE STRONG NORTH TO SOUTH GRADIENT...IF
FRONT SNEAKS A BIT FURTHER SOUTH...IT WOULD BE COLDER.
WILL HAVE STRATIFORM TYPE PRECIPITATION MONDAY AFTERNOON
THROUGH TUESDAY MORNING...THEN GO TO RAIN SHOWERS/CONVECTIVE TYPE
PRECIPITATION/ FOR TUESDAY AFTERNOON AND TUESDAY NIGHT. KEPT THE
CHANCE OF THUNDER BELOW 15 PCT FOR OUR SOUTHERN COUNTIES TUESDAY
NIGHT.
SURFACE FRONT LIKELY TO WHIP THROUGH DURING THE DAY ON
WEDNESDAY...SO INCREASED SURFACE WINDS THEN.
CURRENTLY...NO STRONG INDICATIONS FROM THE 00Z MODEL SOLUTIONS TO
ADD ANY WATER HAZARD FOR RAIN AMOUNTS.
TEMPERATURES WILL BE TOUGH THROUGH THIS ENTIRE PERIOD. TRIED TO STAY
ON THE MILD SIDE OF 00Z GFS MOS GUIDANCE FOR TUESDAY NIGHT...IN THE
WARM SECTOR AHEAD OF APPROACHING LOW.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
UNFORTUNATELY MODELS HAVE REVERTED BACK TO THEIR TIMING DIFF WITH
EJECTIONS OF SW UPR LOW...WITH 12Z ECWMF CONSIDERABLY SLOWER NOW.
WILL LEAN HEAVILY ON HPC WITH THIS SYS. ASSOCIATED SFC LOW LOOKS TO
TAKE A FAMILIAR TRACK THIS SEASON...THRU OH VALLEY. THIS WILL MEAN A
COLD FRONTAL PASSAGE SOMETIME ON WED WITH RA AND A TURN TO SEASONAL
TEMPS BEHIND IT FOR THU.
MORE ENERGY LOOKS TO DUMP BACK INTO SW CONUS...HELPING TO FORM
ANOTHER UPR LOW WHICH WILL TRY TO COME EAST LATE IN THE
PERIOD...WITH NORTHERN STREAM TRYING TO AMPLIFY ACROSS THE UPR
MIDWEST. THIS WILL HAVE TO BE MONITORED FOR SOME POTENTIAL PRE
CHRISTMAS MISCHIEF. AS OF NOW BL LOOKS WARM ENOUGH FOR RA.
&&
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
VORT MAX ROTATING ACROSS CENTRAL WEST VIRGINIA AT THIS TIME...WITH
BACK EDGE OF GENERAL SNOW SHOWER ACTIVITY ACCOMPANYING IT. MVFR
CIGS AT CKB/EKN/BKW WILL LINGER FOR A COUPLE OF HOURS...BEFORE
MOISTURE DECREASE SHUTS OFF THE REMAINING SNOW SHOWERS. CIGS WILL
RISE TO VFR IN MOST AREAS BY MIDMORNING. AS HIGH PRESSURE BUILDS IN
THIS AFTERNOON...SKIES WILL CLEAR AREAWIDE...WITH VFR EXPECTED FROM
18Z ON.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z MONDAY...
FORECAST CONFIDENCE: HIGH.
ALTERNATE SCENARIOS: MVFR CIGS MAY LINGER A BIT LONGER THAN FORECAST.
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 M H H H H H H H H H H H
HTS CONSISTENCY H H H H H H H H H H H H
BKW CONSISTENCY H L M H H H H H H H H H
EKN CONSISTENCY M L L M M M M M M H H H
PKB CONSISTENCY M H H H H H H H H H H H
CKB CONSISTENCY M M M M M M M M H H H H
AFTER 12Z MONDAY...
NO SIGNIFICANT AREAS OF IFR EXPECTED.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...KTB/CL
NEAR TERM...CL
SHORT TERM...KTB
LONG TERM...30
AVIATION...CL
AREA FORECAST DISCUSSION
NWS CHARLESTON WV
339 AM EST SUN DEC 18 2011
.SYNOPSIS...
HIGH PRESSURE TODAY INTO MONDAY. EAST/WEST FRONT DROPS SOUTH MONDAY
NIGHT...BECOMES STATIONARY BY TUESDAY MORNING IN NORTHERN WEST
VIRGINIA INTO CENTRAL OHIO...THEN CREEPS BACK NORTH IN AFTERNOON.
&&
.NEAR TERM /THROUGH TONIGHT/...
VORT MAX ALONG BACK EDGE OF H500 TROUGH SHOWING UP WELL ON WATER
VAPOR LOOP...NOW IN THE TRI-STATE AREA. RUC13 HAS A GOOD HANDLE ON
THIS...BRINGING THE LOBE EAST OF CRW BY 12Z...AND ACROSS THE
MOUNTAINS BY 15Z. BACK EDGE OF LIGHT SNOW WILL FOLLOW THIS...UNTIL
ONLY A FEW SCATTERED UPSLOPE SHSN REMAIN BY MIDMORNING. HAVE NOT
RECEIVED MANY SNOW REPORTS BUT EXPECT ACCUMULATIONS ARE GENERALLY AN
INCH OR LESS AT THIS POINT. FAVORABLE SNOW GROWTH CONDITIONS WILL BE
DIMINISHING AS MOISTURE IN THE DGZ DECREASES. ADDITIONAL MINOR
ACCUMULATION OF LESS THAN AN INCH IS POSSIBLE...MAINLY IN THE
NORTHERN MOUNTAINS...WITH A BIT OF AN UPSLOPE ASSIST. A FEW
FLURRIES MAY LINGER INTO EARLY AFTERNOON IN THE NORTHERN MOUNTAINS
BEFORE ENDING. CLOUDS WILL BE BREAKING IN THE WEST AS ANTICYCLONIC
FLOW TAKES HOLD.
SURFACE HIGH PRESSURE CROSSES BY TO OUR SOUTH THIS EVENING...AND
MOVES TOWARD THE CAROLINA COAST BY 12Z MONDAY. AFTER A CLEAR START
TO THE NIGHT...SOME MID AND HIGH CLOUDS WILL START SHOWING UP LATE
IN THE DEVELOPING SW RETURN FLOW. WARM ADVECTION IS FAIRLY GENTLE
OVERNIGHT AND STICKING WITH A NORMAL DIURNAL TEMPERATURE TREND FOR
NOW.
LEANED A BIT MORE TOWARD THE COOLER MAV TODAY...HAVING PERFORMED
BETTER YESTERDAY. WARMER MET LOOKS MORE REASONABLE TONIGHT IN THE
DEVELOPING WARM ADVECTION.
&&
.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
NO MAJOR CHANGES MADE TO MONDAY ON THIS SUNDAY MORNING GRAVEYARD
SHIFT. CLOUDS INCREASE ACROSS OUR WESTERN AND NORTHERN
COUNTIES...WITH SUNSHINE HOLDING THE LONGEST IN SOUTHWEST VIRGINIA
AND SOUTHEAST WEST VIRGINIA. POPS INCREASING QUICKLY ACROSS
SOUTHEAST OHIO DURING THE AFTERNOON.
HAVE LIKELY POPS FOR PCPN MONDAY NIGHT...MAINLY N OF HTS-CRW-EKN
LINE.
BASING THE FORECAST ON THE FRONT STILL SAGGING SOUTH MONDAY
NIGHT...REACHING NEAR A ROUTE 50 CORRIDOR BY 12Z TUESDAY BEFORE
TRYING TO LIFT SLOWLY BACK NORTH TUESDAY AFTERNOON...AHEAD OF
SURFACE LOW PRESSURE MOVING NORTHEAST UP THE OHIO RIVER VALLEY
TUESDAY NIGHT INTO WEDNESDAY.
FOR ABOUT A 6 HOUR WINDOW ON EITHER SIDE OF 12Z TUESDAY...WILL HAVE
THE POSSIBILITY OF A WINTRY MIXTURE OF RAIN...SNOW...SLEET...FROM
THE EKN VCNTY TO CKB-PKB AND NORTH OF UNI. FORECASTING THE SURFACE
TEMPERATURES IN THE 34/35 DEGREE NEIGHBORHOOD IN THAT TIME
INTERVAL FOR NORTHERN COUNTIES...SO DO NOT HAVE READINGS BELOW
FREEZING. OF COURSE...IN THE STRONG NORTH TO SOUTH GRADIENT...IF
FRONT SNEAKS A BIT FURTHER SOUTH...IT WOULD BE COLDER.
WILL HAVE STRATIFORM TYPE PRECIPITATION MONDAY AFTERNOON
THROUGH TUESDAY MORNING...THEN GO TO RAIN SHOWERS/CONVECTIVE TYPE
PRECIPITATION/ FOR TUESDAY AFTERNOON AND TUESDAY NIGHT. KEPT THE
CHANCE OF THUNDER BELOW 15 PCT FOR OUR SOUTHERN COUNTIES TUESDAY
NIGHT.
SURFACE FRONT LIKELY TO WHIP THROUGH DURING THE DAY ON
WEDNESDAY...SO INCREASED SURFACE WINDS THEN.
CURRENTLY...NO STRONG INDICATIONS FROM THE 00Z MODEL SOLUTIONS TO
ADD ANY WATER HAZARD FOR RAIN AMOUNTS.
TEMPERATURES WILL BE TOUGH THROUGH THIS ENTIRE PERIOD. TRIED TO STAY
ON THE MILD SIDE OF 00Z GFS MOS GUIDANCE FOR TUESDAY NIGHT...IN THE
WARM SECTOR AHEAD OF APPROACHING LOW.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
UNFORTUNATELY MODELS HAVE REVERTED BACK TO THEIR TIMING DIFF WITH
EJECTIONS OF SW UPR LOW...WITH 12Z ECWMF CONSIDERABLY SLOWER NOW.
WILL LEAN HEAVILY ON HPC WITH THIS SYS. ASSOCIATED SFC LOW LOOKS TO
TAKE A FAMILIAR TRACK THIS SEASON...THRU OH VALLEY. THIS WILL MEAN A
COLD FRONTAL PASSAGE SOMETIME ON WED WITH RA AND A TURN TO SEASONAL
TEMPS BEHIND IT FOR THU.
MORE ENERGY LOOKS TO DUMP BACK INTO SW CONUS...HELPING TO FORM
ANOTHER UPR LOW WHICH WILL TRY TO COME EAST LATE IN THE
PERIOD...WITH NORTHERN STREAM TRYING TO AMPLIFY ACROSS THE UPR
MIDWEST. THIS WILL HAVE TO BE MONITORED FOR SOME POTENTIAL PRE
CHRISTMAS MISCHIEF. AS OF NOW BL LOOKS WARM ENOUGH FOR RA.
&&
.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
01Z SUNDAY THRU 00Z MONDAY...
UPPER DISTURBANCE ROTATES THROUGH OVERNIGHT. MVFR CIGS/VSBYS IN -SN
WITH OCCASIONAL IFR TO THE NORTH (PKB/CKB/EKN). NOT MUCH SNOW TO
THE SOUTH...BUT MVFR CIGS ARE EXPECTED TO DEVELOP FOR AT LEAST A FEW
HOURS. SYSTEM STARTS TO PULL AWAY AFTER 12Z WITH IMPROVING
CIG/VSBY...ALTHOUGH EKN WILL SEE MVFR LINGER FOR A FEW MORE HOURS.
SKIES WILL THEN CLEAR THIS AFTERNOON...WITH VFR FOR THE BALANCE OF
THE PERIOD.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z MONDAY...
FORECAST CONFIDENCE: MEDIUM.
ALTERNATE SCENARIOS: TIMING AND INTENSITY OF SNOW COULD VARY ACROSS
THE NORTH.
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 SUN 12/18/11
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 H M M M M H H H H H H H
HTS CONSISTENCY H M H H H H H M H H H H
BKW CONSISTENCY H M M H M M H M H H H H
EKN CONSISTENCY L L M M M M M M L M M H
PKB CONSISTENCY H H H H H M M H H H H H
CKB CONSISTENCY M M M M M M M L M L H H
AFTER 06Z MONDAY...
NO SIGNIFICANT AREAS OF IFR EXPECTED.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...KTB/CL
NEAR TERM...CL
SHORT TERM...KTB
LONG TERM...30
AVIATION...CL
AREA FORECAST DISCUSSION
NWS HOUSTON/GALVESTON TX
544 PM CST MON DEC 19 2011
.AVIATION...
LOT OF THINGS HAPPENING THIS EVENING MAKING AVIAION FORECAST VERY
DIFFICULT. WARM MOIST AIRMASS STREAMING NORTH AHEAD OF THE
APPROACHING FRONT AND UPPER AIR DISTURBANCE. NUMEROUS RAINSHOWERS
CONTINUE TO STREAM NORTH FROM THE GULF MAINLY EAST OF A BRYAN TO
MATAGORDA BAY LINE. THESE SHOWERS WILL RESULT IN VISIBILITY
DROPPING TO NEAR 1-2 MILES AT TIMES AND CEILINGS DOWN TO 015BKN.
THIS AREA OF PCPN WILL SLOWLY SLIDE TO THE EAST AS THE APPROACHING
FRONT WITH A LINE OF THUNDERSTORMS APPROACHES FROM THE WEST. THESE
THUNDERSTORM WILL REACH KCLL AROUND 02Z...KCXO AROUND 06Z...KIAH
AROUND 06Z...KHOU AROUND 07Z. NOT SURE IF THE THUNDERSTORMS WILL
MAKE IT TO THE COAST BUT THE FRONT SHOULD PUSH OFF THE COAST
AROUND 12Z. A LOT OF UNCERTAINTY IN THE TAF FORECASTS ON TIMING
AND ALSO ON TYPE OF PCPN. EARLY TONIGHT EXPECT SOME LOW LEVEL WIND
SHEAR AT MOST TAF SITES SOUTH AND EAST OF FRONT AS LOW LEVEL WINDS
ARE BETWEEN 30 AND 40 KNOTS FROM THE SOUTH.
&&
.PREV DISCUSSION... /ISSUED 350 PM CST MON DEC 19 2011/
DISCUSSION...
A STRONG UPPER LEVEL LOW PRESSURE SYSTEM CONTINUES PUSHING
NORTHEASTWARD INTO THE TEXAS PANHANDLE THIS AFTERNOON. AHEAD OF
THIS SYSTEM SHOWERS AND THUNDERSTORMS CONTINUE TO INCREASE IN
COVERAGE ACROSS CENTRAL AND NORTH TEXAS...WITH THIS ACTIVITY
EXTENDING SOUTHWARD INTO OUR NORTHWESTERN COUNTIES. THIS ACTIVITY
SHOULD CONTINUE TO INCREASE IN COVERAGE ACROSS OUR WESTERN
COUNTIES THIS AFTERNOON BEFORE A BROKEN LINE OF THUNDERSTORMS
PUSHES EASTWARD THROUGH THE REGION THIS EVENING. LATEST RUNS OF
THE HRRR AND LOCAL WRF MODELS CONTINUE TO SUGGEST THE STRONGEST
ACTIVITY WILL DEVELOP ACROSS OUR NORTHERN COUNTIES LATER THIS
EVENING AND PUSH EASTWARD OUT OF THE REGION BY AROUND MIDNIGHT.
SCATTERED SHOWERS AND THUNDERSTORMS MAY LINGER ACROSS OUR EASTERN
AND COASTAL COUNTIES THROUGH DAYBREAK ON TUESDAY BEFORE THE
PACIFIC COLD FRONT PUSHES THROUGH THE REGION. OUR NEXT CHANCE FOR
RAIN WILL COME WEDNESDAY NIGHT INTO THURSDAY MORNING AS ANOTHER
UPPER LEVEL TROUGH MOVES THROUGH THE PANHANDLE. STRONG ISENTROPIC
LIFT WILL EXIST ACROSS THE REGION ALONG WITH UPPER LEVEL SUPPORT
IN THE FORM OF A RIGHT ENTRANCE REGION OF THE UPPER JET.
PRECIPITATION SHOULD COME TO AN END FAIRLY EARLY THURSDAY
AFTERNOON AS THE SYSTEM MOVES RAPIDLY OUT OF THE REGION.
MODELS CONTINUE TO HAVE SOME DIFFICULTY WITH THE TIMING OF THE
NEXT WEATHER SYSTEM WHICH WILL AFFECT THE REGION OVER THE HOLIDAY
WEEKEND. LATEST MODEL RUNS HAVE TRENDED DRIER FOR THE WEEKEND BUT
AM HESITANT TO REMOVE POPS WITH THE UPPER TROUGH AXIS REMAINING TO
OUR WEST. WILL KEEP SLIGHT CHANCE POPS IN PLACE FOR CHRISTMAS DAY
FOR NOW. 38
&&
.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 53 61 38 60 46 / 80 10 10 10 60
HOUSTON (IAH) 62 68 43 62 50 / 80 20 10 10 60
GALVESTON (GLS) 63 70 50 62 56 / 60 30 10 10 60
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 9 PM CST THIS EVENING
FOR THE FOLLOWING ZONES: MATAGORDA BAY...WATERS FROM
FREEPORT TO THE MATAGORDA SHIP CHANNEL OUT 20 NM.
SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL MIDNIGHT CST TONIGHT
FOR THE FOLLOWING ZONES: GALVESTON BAY...WATERS FROM HIGH
ISLAND TO FREEPORT OUT 20 NM.
SMALL CRAFT ADVISORY UNTIL 6 AM CST TUESDAY FOR THE FOLLOWING
ZONES: WATERS FROM HIGH ISLAND TO FREEPORT 20 TO 60 NM.
SMALL CRAFT ADVISORY UNTIL 9 PM CST THIS EVENING FOR THE
FOLLOWING ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP
CHANNEL 20 NM TO 60 NM.
&&
$$
DISCUSSION...47
AVIATION/MARINE...34
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
407 PM CST SUN DEC 18 2011
.DISCUSSION...
12Z UPPER AIR ANALYSIS INDICATED THAT A CUT OFF LOW REMAINED IN
PLACE OVER FAR SOUTHERN CA WITH RIDGING OVER THE GULF OF MEXICO.
THIS LEFT SOUTHWEST FLOW ALOFT OVER THE SOUTHERN PLAINS OUT AHEAD
OF THE UPPER LOW. SOUTHWEST FLOW ALOFT HAD LED TO THE ADVECTION OF
STEEP LAPSE RATES INTO WEST TX THIS MORNING WITH A TEMPERATURE
DIFFERENCE IN THE H700 TO H500 LAYER OF 22 DEG C. A POOL OF 10 DEG
C DEW POINTS WAS OBSERVED AT THE H850 LEVEL OVER FAR SOUTH TX AND
THE EFFECTS OF LEE SIDE CYCLOGENESIS WERE BECOMING EVIDENT WITH
THE DEVELOPMENT OF A CYCLONIC CIRCULATION OVER FAR WEST TX. 21Z
SFC ANALYSIS INDICATED THAT A MOISTURE WAS RAPIDLY RETURNING TO
WESTERN AND CENTRAL TX WITH 45 DEG F DEW POINTS OBSERVED AS VAR
NORTH AS CHILDRESS.
TONIGHT THROUGH TUESDAY...AFTERNOON WATER VAPOR IMAGERY INDICATED
THAT THE CUT OFF LOW AS ALREADY BEGINNING TO MOVE EAST AND THE
CENTER OF CIRCULATION HAD JUST CROSSED OVER THE SOUTHERN AZ BORDER
AS OF 21Z. A PLUME OF PACIFIC MOISTURE HAS ALREADY BEEN ADVECTED
OVER MUCH OF THE SOUTHERN PLAINS...AND SOUTHWEST FLOW ALOFT
CONTINUES THIS TRANSPORT OF MID TO UPPER TROPOSPHERIC MOISTURE
INTO THE REGION. THE PROGRESSION OF SURFACE DEW POINTS WAS THE
MOST INTERESTING PIECE OF INFORMATION THAT COULD BE OBSERVED ABOUT
THE POTENTIAL THERMODYNAMIC ENVIRONMENT THIS AFTERNOON AHEAD OF
THIS UPPER LOW. BASED ON 12Z GUIDANCE...THE NAM WAS THE ONLY MODEL
TO SUFFICIENTLY HANDLE THE RAPID INFLUX OF LOW LEVEL MOISTURE INTO
TX. THE NAM HAD ROUGHLY AN ACCURATE REPRESENTATION OF 21Z DEW
POINTS ACROSS TX WITH THE GFS LAGGING BEHIND BY 6 HRS AND THE
ECMWF COMING IN A FEW DEG F TOO LOW FOR ITS 00Z FORECAST THIS
EVENING. EVEN THE 18Z INITIALIZATION OF THE RUC IS SLOW ON THIS
MOISTURE TRANSPORT WHICH POINTS TO A POTENTIALLY SIGNIFICANT
SOURCE OF ERROR WITH REGARDS TO HANDLING THE THERMODYNAMIC
ENVIRONMENT THAT WILL SET UP OVER NORTH TX TOMORROW.
DID NOT CHANGE MUCH WITH REGARDS TO THE TIMING OF EXPECTED
PRECIPITATION ACROSS NORTH TX WITH THIS FORECAST PACKAGE. THE
UPPER LEVEL SYSTEM AND ASSOCIATED FRONTAL BOUNDARIES ARE EXPECTED
TO MOVE THRU NORTH TX AT ROUGHLY THE SAME TIME AS THE PREVIOUS
FORECAST INDICATED. THE UPPER LOW IS EXPECTED TO MOVE INTO THE
SOUTHERN PLAINS TOMORROW EVENING AND THEN BECOME NEGATIVELY TILTED
AS IT MOVES NORTHEAST OVER NORTH CENTRAL TX AND OVER OK MONDAY
NIGHT. STRONG LARGE SCALE FORCING FOR ASCENT WILL SPREAD OVER
NORTH TX AHEAD OF THIS UPPER LOW...WITH MAXIMUM ASCENT SPREADING
OVER THE FORECAST AREA FROM 21Z MONDAY TO 06Z TUESDAY. THE
FORECAST STRENGTH OF THE UPPER LOW AS IT MOVES OVER THE SOUTHERN
PLAINS IS HIGH WITH H500 HEIGHTS REGISTERING AS A -2.5 STANDARD
DEVIATION ANOMALY PER HPCS ANALYSIS OF THE 12Z GFS. PRECIPITABLE
WATER VALUES CONTINUE TO BE FORECAST TO HOLD IN THE 99TH
PERCENTILE OVER NORTH TX FOR DECEMBER. THE 0 TO 6 KM BULK SHEAR
MAGNITUDE IS EXPECTED TO BE IN EXCESS OF 55 KTS DURING THE PERIOD
OF MAXIMUM FORCING FOR ASCENT WHICH SPEAKS TO THE STRENGTH OF THE
WIND FIELDS OUT AHEAD OF THIS SYSTEM. INSTABILITY CONTINUES TO BE
THE MOST DIFFICULT PARAMETER TO FORECAST...AND THE DEGREE OF
INSTABILITY WILL LARGELY DETERMINE OUR SEVERE WEATHER CHANCES AND
COVERAGE TOMORROW AFTERNOON.
BASED ON 21Z SURFACE OBS...THE NAM APPEARS TO HAVE THE BEST HANDLE
ON LOW LEVEL MOISTURE MOISTURE RETURN OUT AHEAD OF THIS SYSTEM.
MOISTURE TRANSPORT IS EXPECTED TO INCREASE IN INTENSITY TONIGHT
AND DURING THE DAY MONDAY AS THE UPPER LEVEL LOW MOVES OVER THE
SOUTHERN PLAINS. THE LOW LEVEL JET IS FORECAST TO INCREASE TO AT
LEAST 50 KTS OVER NORTH TX TOMORROW...WITH OUR LOCAL 4 KM WRF
INDICATING A POTENTIAL JET CORE OF 60 KTS AFTER 21Z. STRATUS IS
STILL EXPECTED TO BE IN PLACE OVER MOST OF THE OPEN WARM SECTOR
TOMORROW WHICH WILL BE A LIMITING FACTOR FOR LOW LEVEL
DESTABILIZATION. HOWEVER WITH MOISTURE TRANSPORT LIKELY
UNDERESTIMATED IN MOST OPERATIONAL GUIDANCE...THINK THAT SURFACE
BASED INSTABILITY IS LIKEWISE UNDERESTIMATED. 12Z MOS GUIDANCE IS
NOW CONSISTENT WITH MID 60S HIGHS FOR DFW TOMORROW. MOS GUIDANCE
ALSO INDICATES HIGHS IN THE UPPER 60S TO LOWER 70S FOR WACO
TOMORROW. THIS IS A FEW DEGREES WARMER THAN HIGHS WERE EXPECTED TO
CLIMB FROM YESTERDAYS FORECAST.
CONFIDENCE IN THESE HIGHER TEMPERATURES IS INCREASING DUE TO
SIGNIFICANT BREAKS IN CLOUD COVER OVER NORTH TX AND THE TX GULF
COAST. WARMER AFTERNOON TEMPERATURES TODAY WILL THEORETICALLY LEAD
TO WARMER OVERNIGHT LOWS ONCE CLOUD COVER BUILDS BACK IN TONIGHT.
THIS WOULD MEAN THAT LESS HEATING IS NECESSARY TO REACH HIGHER
TEMPERATURES TOMORROW AFTERNOON. THE 12 AND 18Z NAM RUNS BOTH
CONTINUE TO AGGRESSIVELY ADVERTISE FREE CONVECTION POTENTIAL
TOMORROW AFTERNOON AND EVENING. WITH THE NAM HAVING THE BEST
HANDLE ON LOW LEVEL MOISTURE AND HIGH TEMPERATURES LIKELY CLIMBING
A FEW DEGREES HIGHER TOMORROW THAN PREVIOUS EXPECTED...CONFIDENCE
IN THE NAMS THERMODYNAMIC SOLUTION HAS INCREASED SUBSTANTIALLY.
THE NAM ADVERTISES A CORRIDOR OF SURFACE BASED CAPE OF 1000 J/KG
EXTENDING FROM THE METROPLEX SOUTH...NEAR THE INTERSTATE 35
CORRIDOR BY 00Z TUE OR TOMORROW AT 6 PM.
AS PREVIOUS FORECAST MENTIONED...LOW LCL HEIGHTS INDICATE THAT A
SIGNIFICANT PORTION OF THE FREE CONVECTION POTENTIAL ENERGY /CAPE/
WILL LIE IN THE LOWEST 3 KMS. 0 TO 3 KM CAPE VALUES ARE FORECAST
TO BE IN EXCESS OF 200 J/KG WITHIN THIS SAME GENERAL CORRIDOR.
THESE VALUES ARE QUITE HIGH EVEN FOR A SPRING SEVERE WEATHER
EPISODE...AND HIGH LOW LEVEL CAPE VALUES SPEAK TO THE POTENTIAL
FOR LOW LEVEL STRETCHING AND TILTING OF HORIZONTAL VORTICITY INTO
THE VERTICAL. LOW LEVEL WIND PROFILES CONTINUE TO VEER WITH HEIGHT
AND CONTAIN SIGNIFICANT SPEED SHEAR DUE TO THE PRESENCE OF THE
STRONG LOW LEVEL JET. 0-1 KM HELICITY VALUES IN EXCESS OF 200
M2/S2 ARE PRESENT WITHIN THE CORRIDOR OF HIGH LOW LEVEL CAPE. THIS
COMBINATION OF PARAMETERS INDICATES THAT ANY UPDRAFT WILL HAVE A
STRONG LIKELIHOOD TO INGEST HORIZONTAL VORTICITY WHICH GREATLY
INCREASES THE SEVERE WEATHER THREAT TOMORROW AFTERNOON. THE
GENERAL STORM MODE IS STILL EXPECTED TO BE LINEAR WITH SIGNIFICANT
FORCING FOR ASCENT EXPECTED ALONG A PACIFIC TYPE COLD FRONT THAT
WILL MOVE TROUGH NORTH TX JUST AHEAD OF THE CORE OF THE UPPER LOW.
THIS NORTH/SOUTH ORIENTED FRONT IS ORIENTED NEARLY PARALLEL TO THE
0-6 KM BULK SHEAR VECTORS WHICH GENERALLY FAVORS SHARED COLD POOLS
LEADING TO A LINEAR STORM MODE.
EVEN WITH A LINEAR STORM MODE STRETCHING AND TILTING OF HORIZONTAL
VORTICITY INTO THE VERTICAL CAN LEAD TO THE DEVELOPMENT OF
MESOVORTICIES CAPABLE OF PRODUCING STRONG LOCALIZED WIND
DAMAGE...AND TO THE DEVELOPMENT OF BRIEF TORNADOES. ANY DISCRETE
STORMS OUT AHEAD OF LINE SEGMENT CONVECTION WILL LIKELY BE IN THE
FORM OF LOW-TOPPED AND VERY FAST MOVING SUPERCELLS. ANY LOW-TOPPED
SUPERCELL AWAY FROM THE MAIN LINE OF CONVECTION WILL BE CAPABLE OF
PRODUCING A TORNADO...ESPECIALLY SOUTH OF THE METROPLEX TOMORROW
AFTERNOON. THE MOST WIDESPREAD SEVERE WEATHER HAZARD IS THOUGHT
TO BE IN THE FORM OF STRAIGHT LINE WIND DAMAGE...AND THIS IS
MOSTLY DUE TO THE POTENTIAL FOR STRONG ENVIRONMENTAL WINDS TO BE
DRIVEN DOWN TO THE SURFACE. DEEP MOISTURE MEANS THAT THERE IS
LITTLE THETA-E DIFFERENCE WITH HEIGHT...AND THEREFORE LITTLE
POTENTIAL FOR ENHANCED DOWNDRAFT SPEEDS OR MICROBURSTS.
OVERALL CONFIDENCE IN AN ORGANIZED STORM MODE IS HIGH NOW FOR
TOMORROW AFTERNOON. DAMAGING STRAIGHT LINE WINDS WITH A HIGH
POTENTIAL FOR LOCALLY ENHANCED DAMAGE IS THE MOST PREVALENT SEVERE
WEATHER HAZARD. THERE IS AN ATTENDANT TORNADO THREAT TOMORROW
AFTERNOON...ESPECIALLY IF ANY DISCRETE STORMS ARE ABLE TO DEVELOP
OUT AHEAD OF THE SQUALL LINE/PACIFIC FRONT. 99TH PERCENTILE PWATS
ALWAYS RAISE THE POTENTIAL FOR LOCALIZED FLOODING ISSUES...HOWEVER
THE VERY FAST STORM MOTION IS EXPECTED TO MITIGATE SIGNIFICANT
FLOODING CONCERNS.
THE PACIFIC TYPE COLD FRONT IS EXPECTED TO MOVE EAST THRU MOST OF
NORTH TX BY MIDNIGHT /06Z TUE/ MONDAY NIGHT. THE ATTENDANT SQUALL
LINE WILL LIKELY BE JUST EXITING THE FORECAST AREA AT THIS TIME
SO HAVE LINGERED HIGH POPS OVER THE FAR EASTERN CWA AFTER
MIDNIGHT. BY TUESDAY MORNING THERE IS SOME LOW END POTENTIAL FOR
LIGHT RAIN ASSOCIATED WITH MOISTURE WRAPPED AROUND THE UPPER
LOW...ESPECIALLY AS SOME RESIDUAL FRONTOGENETIC FORCING BUILDS
INTO THE NORTHERN CWA AS THE CANADIAN AIRMASS RESPONSIBLE FOR THE
BLIZZARD PORTION OF THIS SYSTEM /OVER THE SOUTHERN HIGH PLAINS/
MOVES SOUTH INTO NORTH TX. NO WINTRY PRECIPITATION IS EXPECTED AT
THIS TIME AS THERE WILL BE VERY LITTLE MOISTURE LEFT TO WORK WITH
AND TEMPERATURES WILL GENERALLY REMAIN ABOVE FREEZING EARLY
TUESDAY MORNING BEHIND THE FRONT.
EXTENDED...NO SIGNIFICANT CHANGES MADE TO THE EXTENDED AT THIS
TIME. KEPT THE LOW END RAIN CHANCES OVER THE SOUTHEASTERN PORTION
OF THE CWA ON THURSDAY AS ANOTHER SHORTWAVE TROUGH MOVES OVER
NORTH TX. THE 12Z ECMWF WAS THE MOST AGGRESSIVE WITH PRECIPITATION
BECAUSE IT BRINGS THE WAVE OVER NORTH TX THE FURTHEST NORTH AND
STRONGER THAN THE GFS ADVERTISES. EITHER WAY LIMITED MOISTURE WILL
PREVENT SIGNIFICANT COVERAGE OF RAIN OVER NORTH TX ON THURSDAY.
MAINTAINED A DRY FORECAST FOR THE HOLIDAY WEEKEND AS RUN TO RUN
AND MODEL TO MODEL CONSISTENCY EVEN ON LARGE SCALE FLOW REMAINS
POOR AT THIS TIME. GENERAL CONSENSUS IS THAT TEMPERATURES WILL BE
BELOW NORMAL...SO FOR NOW A COOL AND DRY HOLIDAY WEEKEND IS
EXPECTED.
CAVANAUGH
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 51 64 45 50 31 / 10 80 100 5 5
WACO, TX 52 67 44 53 28 / 10 70 100 5 5
PARIS, TX 44 63 47 54 30 / 10 50 100 10 10
DENTON, TX 52 61 43 46 27 / 10 90 100 10 5
MCKINNEY, TX 48 62 45 50 30 / 10 80 100 5 5
DALLAS, TX 51 64 46 50 31 / 10 80 100 5 5
TERRELL, TX 48 64 49 53 31 / 10 50 100 5 5
CORSICANA, TX 48 66 47 55 32 / 10 50 100 5 5
TEMPLE, TX 50 66 43 55 29 / 10 70 100 5 5
MINERAL WELLS, TX 53 64 39 46 25 / 20 100 80 10 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS LUBBOCK TX
1148 AM CST SUN DEC 18 2011
.AVIATION...
COMPLICATED FORECAST THIS PERIOD DUE TO RECENT DEVELOPMENT OF VFR
CONDITIONS. EARLIER MVFR CIGS AT LBB HAVE SINCE BEEN ERADICATED
BY DRIER AIR/DEEPER MIXING ALONG A LINE FROM BROWNFIELD-LUBBOCK-
NORTHEAST OF PLAINVIEW. LATEST RUC SUGGESTS THESE VFR CONDITIONS
WILL HOLD THROUGH THE DAY WITH STEADY SWLY WINDS...BUT A NWLY PUSH
OF DEEPER MOISTURE OUT OF THE PERMIAN BASIN COULD THREATEN THIS
WITH A RETURN TO MVFR DECKS BEFORE SUNSET. FOR NOW IT APPEARS
SCT LOW CLOUDS WILL PREVAIL AT LBB INTO THE EVENING. THE MOIST
PUSH WILL BE REINFORCED TONIGHT AS WINDS BACK SELY WELL AHEAD OF A
POWERFUL UPPER CYCLONE. CONFIDENCE IS HIGH THAT PROLONGED IFR
CIGS AND REDUCED VISBYS WILL UNFOLD AT LBB AROUND MIDNIGHT BEFORE
DRIZZLE/RAIN/ISOLATED TSRA EMERGE EARLY MON MORNING. PRECIPITATION
MAY BE HEAVY AT TIMES /ESPECIALLY AT CDS/ BUT WILL REMAIN ALL
LIQUID THROUGH 19/18Z BEFORE A STRONG COLD FRONT CHANGES RAIN OVER
TO LIGHT SNOW WELL AFTER THIS TAF WINDOW.
&&
PREV DISCUSSION... /ISSUED 515 AM CST SUN DEC 18 2011/
SHORT TERM...
IMPENDING WINTER STORM IS STILL THE MAIN FOCUS IN THE FORECAST BUT
THE SHORT TERM FORECAST WILL SEE INCREASING CHANCES OF PRECIPITATION
AHEAD OF THE SYSTEM. THE CENTER OF THE UPPER LOW WAS NEARLY ONSHORE
IN BAJA CALIFORNIA EARLY THIS MORNING. THE SYSTEM WILL THEN BEGIN
ITS MARCH EASTWARD TO A LOCATION JUST EAST OF EL PASO BY 12Z MONDAY.
HEIGHTS WILL BEGIN A RAPID DESCENT EARLY MONDAY MORNING ALONG WITH
DIFFLUENCE IN THE UPPER LEVEL WIND FIELDS. THE UPPER LEVEL LIFT FROM
THE LOW WILL BEGIN TO SPREAD OVER THE REGION FROM WEST TO EAST BY
DAYBREAK MONDAY MORNING. AT THE SAME TIME...A LOW LEVEL JET WILL
DEVELOP WITH GOOD ISENTROPIC LIFT SPREADING INTO THE AREA. MOIST LOW
AND UPPER LEVELS WILL BE PREVALENT AT THIS TIME WITH MID LEVEL
SLOWLY MOISTENING. OVERNIGHT TONIGHT...LOW LEVEL MOISTURE WILL
CONTINUE TO SURGE NORTHWARD WITH WINDS SLIGHTLY BACKING TO THE SSE.
PRECIPITATION WILL START OUT AS ALL LIQUID AT THE SURFACE THROUGH
MONDAY MORNING. FOR SUNDAY...LOW STRATUS WILL STICK AROUND AND MAY
BE ABLE TO SQUEEZE OUT A FEW SPRINKLES THIS AFTERNOON AND EVENING.
JDV
LONG TERM...
SOLUTIONS REMAIN TIGHTLY CLUSTERED WITH UPPER LEVEL LOW PRESSURE
MOVING ACROSS SOUTHEAST NEW MEXICO 18Z MONDAY...NEAR LITTLEFIELD
00Z TUESDAY...AND AROUND CLARENDON BY 06Z TUESDAY. THE LATEST RUNS
HAVE WOBBLED BACK A BIT TO THE NORTH BUT REMAIN CONSISTENT ENOUGH
TO RAISE OUR CONFIDENCE IN A POTENTIAL WINTER STORM EVENT OVER THE
FAR NORTHWESTERN SOUTH PLAINS AND EXTREME SOUTHERN TEXAS PANHANDLE.
WE REMAIN SUSPICIOUS OF THIS LEVEL OF AGREEMENT AND ARE RELUCTANT
TO USE MODELS QUITE SO DETERMINISTICALLY. THEREFORE WE HAVE INCLUDED
THE NORTHWESTERN SOUTH PLAINS IN A WINTER STORM WATCH AS A BUFFER
FOR THE MORE PRONE EXTREME SOUTHWEST AND SOUTH-CENTRAL PANHANDLE
ZONES.
OTHER CHANGES THIS GO-AROUND INCLUDE SLIGHTLY DELAYING THE COLD
FRONT PASSAGE THROUGH OUR NORTHWESTERN ZONES UNTIL MID OR LATE
AFTERNOON FOR SOME AREAS. ALTHOUGH COLUMN COOLING WILL BE GOING ON
STRONG...THIS MAY DELAY POSSIBLE CHANGE-OVER TO FROZEN PRECIPITATION
STAGE UNTIL LATER MONDAY FOR MOST NORTHWESTERN ZONES. IT STILL LOOKS
LIKELY THAT THE SOUTHWESTERN SOUTH PLAINS COUNTIES WILL BECOME
DRY-SLOTTED FOLLOWING A POTENTIAL HEALTHY SHOWER OR THUNDERSTORM
EVENT AROUND AND JUST AFTER DAYBREAK MONDAY MORNING...BUT COLD AIR
NOT EXPECTED TO ARRIVE IN TIME FOR FROZEN STAGE SWITCH-OVER INTO
CENTRAL SOUTH PLAINS BEFORE MOST OF THIS PRECIPITATION MOVES AWAY
FROM THE AREA. CENTRAL AREAS WILL NEED FRONTO-GENETIC FORCING AND
POSSIBLE WEAK SOUTHERN EXTENSION OF THE TROWEL LATE MONDAY NIGHT
FOR MUCH PRECIPITATION OPPORTUNITY. AND GIVEN THE LATEST TRENDS OF
PASSAGE SLIGHTLY FURTHER NORTH...SIGNIFICANT COLD PHASE PRECIPITATION
SEEMS UNLIKELY AT THE MOMENT.
ACROSS NORTHERN ZONES LATE MONDAY AND EARLY MONDAY NIGHT...
FRONTOGENETIC FORCING SHOULD BE AUGMENTED BY AT LEAST SOMEWHAT
STRONGER MID LEVEL LIFT AND REMNANT INSTABILITY FOR AN OPPORTUNITY
TO PRODUCE HEAVIER SNOW RATES. HOWEVER...AVAILABILITY OF
SIGNIFICANT DENDRITES STILL IN DOUBT. A MAJOR WINTER STORM MOST
LIKELY WILL REQUIRE THIS ELEMENT WHICH APPEARS MUCH MORE CERTAIN
FROM NORTHEASTERN NEW MEXICO ACROSS THE NORTHERN TEXAS PANHANDLE.
ANYWAY...THIS WAS ONE OF THE ELEMENTS THAT DELAYED US REACHING
SUFFICIENT CONFIDENCE LEVELS EARLIER FOR A WINTER STORM WATCH AND
STILL REMAINS A CONCERN. HOWEVER...OTHER THRESHOLDS SUCH AS STORM
TRACK AND DEEPENING OF THE PARENT UPPER LOW REQUIRES NOW UPGRADING
THE SITUATION TO A WINTER STORM WATCH...ESPECIALLY SINCE START OF
THE EVENT IS NOW WITHIN 36 HOURS. WE HAVE INCREASED FORECAST SNOW
TOTALS SLIGHTLY ACROSS OUR FAR NORTHERN ZONES THOUGH REMAIN WITH
ONLY MODERATE SNOW AMOUNTS. ADDITION OF STIFF NORTHERLY WINDS
POTENTIALLY CLOSE TO 30 MPH AND THREAT OF BLOWING SNOW ADDS
ANOTHER LEVEL OF CONCERN FOR THIS POTENTIAL WINTER STORM.
SYSTEM SHOULD PASS TO THE EAST FAIRLY QUICKLY EARLY TUESDAY.
TEMPERATURES FOR A DAY OR TWO FOLLOWING WILL BE TRICKY DEPENDING
ON ANY SNOW COVER. MOSTLY DRY POSITIVE TILTED TROUGH PASSAGE
EXPECTED EARLY THURSDAY WITH A COOL SURFACE RIDGE MOVING IN.
ANOTHER POTENTIALLY MORE POTENT UPPER TROUGH APPEARS WILL APPROACH
AND PASS JUST NORTH OF THE AREA FRIDAY...DRY MOST LIKELY FOR US...
BUT YET ANOTHER CHILLY AIRMASS SETTLING IN FOR THE WEEKEND. RMCQUEEN
&&
.PRELIMINARY POINT TEMPS/POPS...
FRIONA 55 36 38 21 34 / 10 60 90 60 10
TULIA 56 42 42 22 35 / 10 60 90 70 10
PLAINVIEW 55 43 44 23 37 / 10 60 90 60 10
LEVELLAND 54 43 45 24 40 / 10 70 70 40 10
LUBBOCK 54 45 46 25 39 / 10 60 70 50 10
DENVER CITY 54 42 48 25 44 / 10 70 70 40 0
BROWNFIELD 55 44 49 26 42 / 10 70 70 40 0
CHILDRESS 62 43 47 27 40 / 10 40 90 60 10
SPUR 58 45 51 28 43 / 10 50 80 40 10
ASPERMONT 61 46 54 30 45 / 10 50 70 40 10
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM MONDAY AFTERNOON THROUGH LATE MONDAY
NIGHT FOR THE FOLLOWING ZONES: TXZ021>024-027>029.
&&
$$
99/99/93
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
957 PM EST MON DEC 19 2011
.SYNOPSIS...
A FRONTAL BOUNDARY WILL STALL OUT NORTH OF THE AREA TONIGHT AND
TUESDAY WITH A MILD SOUTHWEST FLOW TO PREDOMINATE. MEANWHILE
STRONG LOW PRESSURE WILL LIFT WELL TO THE NORTHWEST OF THE REGION ON
TUESDAY NIGHT WITH ITS ASSOCIATED COLD FRONT WORKING EAST THROUGH
THE AREA ON WEDNESDAY. AN AREA OF LOW PRESSURE WILL TRACK THROUGH
THE CAROLINAS AND VIRGINIA ON FRIDAY. STRONG UPPER LEVEL HIGH
PRESSURE WILL HOLD BACK ANY INTRUSIONS OF COLDER AIR UNTIL LATE
WEEKEND OR EARLY NEXT WEEK.
&&
.NEAR TERM /THROUGH TUESDAY/...
AS OF 955 PM EST MONDAY...
STILL APPEARS THAT MOST OF THE WARM FRONTAL SHWOERY PRECIP WILL
REMAIN TO THE NORTHWEST OF THE BLACKSBURG FORECAST AREA
OVERNIGHT...HOWEVER ONLY ONE MODEL...LAST FEW RUNS OF THE HOURLY
HRRR...SHOWS ANY INDICATION OF THE ISOLATED SHOWERS LIFTING INTO
EASTERN KY FROM SOUTHERN KY...AND THOSE STAND A MUCH BETTER CHANCE
OF REACHING INTO WRN GREENBRIER OR EVEN SUMMERS COUNTIES A LITTLE
AFTER MIDNIGHT...SO LEANED TOWARD HRRR SOLUTION FOR THAT AND
SLIGHTLY INCREASED THE AREA OF CHC POPS AS WELL AS SLIGHT CHC
POPS. WITH HARDLY ANY BREAKS IN CLOUD COVER EXPECTED ACROSS THE
WEST...AM EXPECTING OVERNIGHT TEMPS TO REMAIN AT OR ABOVE
FREEZING AND SO NOW ONLY HAVE ONE OR TWO GRID POINTS IN GREENBRIER
SUGGESTING ANY SNOW MIXED IN WITH RAIN. ANY PRECIP WILL BE BARELY
MORE THAN A SPRINKLE ANYWAY.
18Z MODEL TRENDS ARE TO SLOW DOWN ANY THREAT OF EVEN LIGHT UPSLOPE
DRIZZLE ALONG THE SOUTHERN BLUE RIDGE UNTIL TOMORROW EVENING AS
MOIST SW FLOW INCREASED AHEAD OF APPROACHING MIDWEST SYSTEM...AND
THE SLOWER TIMING HAS BEEN A CONSISTENT TREND IN MODELS SO MAY BE
PRUDENT TO CONSIDER REMOVING ANY POPS DURING THE DAY TUES.
PREV UPDATE AS OF 710 PM EST MONDAY...
VERY MINOR UPDATE TO INCLUDE MENTION OF SLIGHT CHANCE SHWRS FROM
NOW THROUGH REST OF OVERNIGHT PER RADAR SHOWING WHAT MAY BE A FEW
SPRINKLES OVER THE HIGHER ELEVATIONS OF GREENBRIER AND MAYBE
REACHING PARTS OF BATH COUNTY SOON. STILL LOOKS LIKE ANY AREAS OF
STEADIER LGITH RAIN ASSOC WITH WAVE ALONG WARM FRONT WILL REMAIN
TO THE NORTH OF THE FCST AREA LATER ON TONIGHT...BUT AM KEEPING
THE TINY CORNER OF CHC POPS IN CLOSER TO 12Z. FCST SOUNDINGS
INDICATE NO CHC FOR FREEZING RAIN...MORE LIKELY A SNOW FLAKE THAT
SURVIVES BY WET BULBING THROUGH A PRETTY DRY LOWER ATMOS...SO
REMOVED FREEZING RAIN GRIDS AND INCLUDED A FEW SNOW OR SNOW MIXED
WITH RAIN...AGAIN ONLY A SLIGHT CHC. OTHERWISE MADE A FEW TWEAKS
TO SKTY COVER AND LATEST TEMPS AND DEW PTS...WITH SOME LOWER TEENS
DEW PTS AT SOME HIGHER ELEVATIONS. INCREASED WIND GUSTS ALONG SOME
OF THE RIDGES TO BETTER MATCH SOME RECENT OBS AT HSP.
PREV DISCUSSION AS OF 255 PM EST MONDAY...
RIBBON OF HIGHER MOISTURE/PRECIP FORECAST TO STREAM EASTWARD ALONG A
FRONTAL BOUNDARY EMANATING FROM THE STRONG LOW NOW BRINGING
EXTREME WINTER CONDITIONS TO PARTS OF THE SOUTHWESTERN U.S. HIGHER
RH WITH VERY LIGHT PRECIP COULD FLIRT WITH OUR FAR NORTHERN ZONES
AROUND 09-12Z BUT MODELS CONTINUE TO HOLD THE BULK OF COLD AIR
JUST TO THE NORTH OF THE CWA. H85 REMAINS JUST ABV 0C AND VARIOUS
MODEL P-TYPE ALGORITHMS AND THICKNESS PARAMETERS ALSO KEEP FROZEN
VARIETY JUST NORTH. THAT IS ASSUMING ANY PRECIP AT ALL MAKES IT
INTO THE CWA AND WHATEVER DOES FALL LOOKS TO BE VERY LIGHT.STILL
PLENTY OF DRY AIR OT OVERCOME AS 12Z RNK SOUNDING SHOWED PWAT OF
ONLY 0.24 INCHES OR ABOUT HALF OF NORMAL. SREF PROB AND ENSEMBLE
MEANS BRING VERY LITTLE IF ANY MEASURABLE TO FAR NORTHERN ZONES
EARLY IN THE MORNING. LEFT A FEW HOURS OF SLIGHT CHANCE POPS IN
THE GRIDS OVER GREENBRIER AND BATH COUNTIES WITH POCKETS OF MIXED
PCPN. THE CHANCE OF FROZEN WILL BE HIGHLY DEPENDENT ON HOW MUCH
DIURNAL FALL CAN OCCUR IN BREAKS IN THE OVERCAST AS MID-LEVEL
CLOUD COVER HAS ALREADY OVERTAKEN WESTERN CWA THIS AFTERNOON. LOWS
WILL GENERALLY BE HELD UP BY THIS CLOUD COVER AND WILL RANGE FROM
30S TO NEAR 40 IN MOST LOCATIONS...STILL WELL ABOVE NORMAL.
WHATEVER PRECIP DOES MANAGE TO SNEAK INTO THE FAR NORTHERN ZONES
WILL BE SHORT-LIVED AS POPS DECREASE THROUGH THE DAY WITH THE
BOUNDARY REMAINING STATIONARY AND THEN STARTING A NORTHWARD
RETREAT. ANOTHER MILD DAY TOMORROW IS IN THE CARDS WITH SOUTHERLY
FLOW INCREASING AHEAD OF THE SURFACE LOW BACK OVER THE LOWER
MISSISSIPPI VALLEY. GUIDANCE SHOWING LOW 50S IN THE FAR NORTH AND
MOUNTAINS TO LOW 60S IN THE PIEDMONT...AGAIN AT LEAST 10F ABOVE
MID-DECEMBER CLIMO.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
AS OF 330 PM EST MONDAY...
ECMWF AND SREF A LITTLE SLOWER WITH QPF TUESDAY NIGHT...SO AGAIN
BACKED OFF ABOUT 6 HRS FROM PREVIOUS GRIDS. BEST CHC FOR RAIN WILL
BE WED MORNING...WITH JUST SPOTTY SHOWERS IN THE AFTERNOON. MAX T
WILL BE TOUGH THIS DAY BECAUSE RAIN ARRIVING EARLY IN THE MORNING
MAY MAKE IT DIFFICULT FOR TEMPS TO REBOUND IN THE AFTERNOON
DESPITE DOUBLE DIGIT H85 TEMPS. WENT A FEW DEGREES BELOW GUIDANCE...WITH
THE EXCEPTION OF THE SOUTHSIDE. SOME SLIGHTLY COOLER AIR DOES
ARRIVE ACROSS SE WEST VA LATE PM AND OVERNIGHT AS THE COLD FRONT
ENTERS THE CWA. ANOTHER WAVE WILL RIDE ALONG THE OLD DECAYING
BOUNDARY SUCH THAT RAIN ARRIVES MAINLY THURSDAY NIGHT. THE
GFS/ECMWF ARE IN GOOD AGREEMENT THIS FAR OUT SO INCREASED POPS.
PERHAPS SOME DOWNSLOPING AND CLEARING WILL ALLOW BETTER MIXING AND
THUS WARMER TEMPS ON THURSDAY IN COMPARISON TO WEDNESDAY. A WARM
BUT WET NIGHT FOLLOWS THURSDAY NIGHT. CONSIDERING CLOUDS AND H85
TEMPS WENT ABV GUIDANCE FOR MINS.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 330 PM EST MONDAY...
ECMWF/GFS DIVERGE MORE THOUGH INTO THE HOLIDAY WEEKEND...WITH THE
ECMWF PUSHING THE FRONT FURTHER OFF THE COAST IN COMPARISON TO THE
GFS. THE OP GFS IS QUICKER WITH A DISTURBANCE MOVING OUT OF THE
MIDWEST THAN THE ECMWF WHICH HOLDS MUCH OF THIS UPPER LEVEL
POSITIVELY TILTED TROUGH BACK INTO THE ROCKIES. THIS MEANS THAT
THE OP GFS HAS A STRONG ARCTIC HIGH OVER MAINE...AND DEVELOPS A
STRONG WEDGE WITH LOW PRESSURE GOING UP THE COAST EARLY SATURDAY.
THIS SOLUTION WOULD SUGGEST THE POTENTIAL FOR A WINTRY MIX ACROSS
THE SOUTHERN SHENANDOAH INITIALLY EARLY CHRISTMAS EVE DAY. THE
EUROPEAN...WHICH CONTINUES TO BE THE MORE SKILLFUL MODEL DAY 5 AT
H5...FROM 12Z...HOLDS THE HIGH PRESSURE FURTHER WEST INTO SE
CANADA...AND IT DOES NOT MOVE QUICK ENOUGH EAST TO WEDGE DOWN THE
APPALACHIANS...MEANING A WARMER SOLUTION WITH LOW PRESSURE
TRAVELING FURTHER WEST FROM THE COAST. CONFIDENCE IS LOW
ATTM...BUT WOULD LEAN MORE TOWARDS THE ECMWF EVEN THOUGH IT DOES
HAVE A STRONG BIAS WITH REGARDS TO SOUTHEASTERN US RIDGING. ON THE
CONTRARY...THE SE CONUS RIDGE HAS BEEN A DOMINANT FEATURE THIS
EARLY COOL SEASON SO A WARMER SOLUTION...LIKE THE ECMWF IS MORE
APPROPRIATE. THUS WILL HOLD BACK THE COLDEST AIR IN THE GRIDS
UNTIL MONDAY AND MONDAY NIGHT...WITH JUST RAIN THIS WEEKEND AND
SOME UPSLOPE SNOW SHOWERS ACROSS SE WEST VA CHRISTMAS DAY AND
EARLY MONDAY.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
AS OF 615 PM EST MONDAY...
MAINLY DEALING WITH MID AND HIGH LEVEL CLOUDS THROUGH THE PERIOD. NOT
EXPECTING TOO MANY LOW CLOUDS BUT COULD FLIRT WITH MVFR ESP AT
LWB/BLF TOWARD MORNING...BUT CONFIDENCE LOW AT THE MOMENT ON BELOW
3KFT CIGS.
SUB-VFR CONDITIONS HOLD OFF UNTIL LATER TUE NIGHT...WITH MORE
WIDESPREAD RAIN AND ASSOCIATED LOW CLOUDS AND VISIBILITIES ON
WEDNESDAY. BRIEF VFR RETURNS THURSDAY FOLLOWED BY A SECOND STORM
SYSTEM BY FRIDAY WHICH MAY BRING ANOTHER ROUND OF RAIN AS WELL AS
LOW CIGS AND VSBYS THURSDAY NIGHT INTO FRIDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...JH/KM
NEAR TERM...PC/SK
SHORT TERM...KM
LONG TERM...KM
AVIATION...JH/PC/WP
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
553 PM CST MON DEC 19 2011
.SHORT TERM...THROUGH WEDNESDAY NIGHT
246 PM CST MON DEC 19 2011
MAIN FORECAST CONCERN IS WITH THE PRECIPITATION CHANCES AND TYPES
TUESDAY AND TUESDAY NIGHT.
SURFACE ANALYSIS THIS AFTERNOON SHOWS A NEARLY STATIONARY FRONT
FROM LOWER MICHIGAN TO AN AREA OF LOW PRESSURE OVER EASTERN NEW
MEXICO. HIGH PRESSURE WAS CENTERED OVER THE WESTERN DAKOTAS AND
EASTERN MONTANA.
STRATUS CLOUDS HAVE COME IN BEHIND THE COLD FRONT AND COVERED
ALMOST THE ENTIRE AREA THIS AFTERNOON. VISIBLE SATELLITE DOES
SHOW QUITE A FEW HOLES IN THE CLOUD FIELD AND THE CLOUDS ALSO
APPEAR TO BE THINNING OUT. THE 19.12Z NAM BUFKIT SOUNDINGS WOULD
SUGGEST THE CLOUDS SHOULD SCATTER OUT THIS EVENING WHILE SEVERAL
RUNS NOW OF THE RUC DO NOT SCATTER THE CLOUDS OUT UNTIL THE
OVERNIGHT HOURS. HAVE TRIED TO BALANCE THESE MODEL TRENDS WITH THE
CURRENT SATELLITE TRENDS TO SHOW CLEARING THROUGH THE EVENING FOR
MOST OF THE AREA. THIS WILL ALSO HAVE A BIG IMPACT ON THE
TEMPERATURES. HAVE BUMPED THE TEMPERATURES UP SOME...ESPECIALLY
ACROSS THE NORTH WHERE THE CLOUDS MAY HOLD ON THE LONGEST...BUT IF
THEY CLEAR OUT EARLIER THAN EXPECTED...THESE WILL HAVE TO BE MOVED
DOWN.
THE STORM SYSTEM OVER THE SOUTHWEST WILL BE EJECTING NORTHEAST
TOWARD THE OHIO RIVER VALLEY AND EASTERN GREAT LAKES FOR TUESDAY
THROUGH WEDNESDAY. AFTER A NORTHWARD JOG IN THE TRACK OF THIS
SYSTEM WITH YESTERDAY/S MODELS...ALL THE 19.12Z MODELS HAVE
SETTLED BACK SOUTH WITH THE TRACK. IT ONCE AGAIN APPEARS THAT THE
SOUTHERN PARTS OF THE AREA WILL EITHER GET BRUSHED WITH THIS SYSTEM
OR IT WILL JUST MISS TO THE SOUTH. THE NAM AND GFS STILL SHOW
DECENT FORCING WITH THIS SYSTEM JUST GOING BY TO THE SOUTH.
BETWEEN 4 AND 8 PVU/S OF VORTICITY ADVECTION IN THE 500-300 MB
LAYER PASSES BY TUESDAY AFTERNOON AND NIGHT. THE BEST QG
CONVERGENCE IS EXPECTED TO MISS THE AREA WITH JUST SOME WEAK
CONVERGENCE IN THE 700-500 MB LAYER COMING THROUGH TUESDAY NIGHT.
STILL EXPECTING TO SEE SOME WEAK FRONTOGENESIS IN THE 850-500 MB
LAYER AS WELL. ONE THING THAT HAS NOT CHANGED IN THE MODELS...IS
WHETHER THERE WILL BE ICE PRESENT IN THE CLOUDS. BUFKIT SOUNDINGS
ACROSS THE FAR SOUTH CONTINUE TO SUGGEST CLOUD TOP TEMPERATURES
ONLY AROUND -10C WHICH COULD LEAD TO MORE LIQUID INSTEAD OF SNOW.
HAVE CONTINUED WITH THE MIX OF FREEZING RAIN/RAIN AND SNOW BUT
WITH ONLY LIGHT PRECIPITATION AMOUNTS ANTICIPATED...ANY SNOW OR
ICE ACCUMULATIONS WILL BE VERY LIGHT.
ONCE THIS SYSTEM GOES BY...A NORTHERN STREAM SHORT WAVE TROUGH
WILL MOVE ALONG THE CANADIAN BORDER WEDNESDAY NIGHT. THIS WAVE
WILL PUSH A COLD FRONT INTO THE AREA THAT COULD POSSIBLY PRODUCE
SOME LIGHT SNOW AND HAVE CONTINUED WITH THE LOW END SNOW CHANCES
ACROSS THE NORTH WITH THIS SYSTEM.
.LONG TERM...THURSDAY THROUGH MONDAY
246 PM CST MON DEC 19 2011
THE COLD FRONT WILL CONTINUE TO PUSH SOUTH ACROSS THE REMAINDER OF
THE AREA THURSDAY AND COULD STILL BE PRODUCING SOME LIGHT SNOW.
ADDED IN SOME LOW END SNOW CHANCES TO HANDLE THIS POSSIBILITY.
ONCE THIS SYSTEM GOES BY...THE REMAINDER OF THE PERIOD LOOKS TO BE
PRETTY QUIET. ANOTHER NORTHERN STREAM WAVE COULD BRUSH THE UPPER
MIDWEST CHRISTMAS DAY AND HAVE CONTINUED WITH THE LOW SNOW CHANCES
ACROSS THE NORTHERN PART OF THE FORECAST AREA AS THE BEST FORCING
WITH THIS WAVE LOOKS TO REMAIN TO THE NORTH OF THE AREA.
&&
.AVIATION...TONIGHT AND TUESDAY
553 PM CST MON DEC 19 2011
THE MAIN CONCERN AT THE REGIONAL TAF SITES IS WITH CLOUD COVER AND
WHEN/IF THE MVFR/VFR STRATUS CLEARS OUT. A STRATUS FIELD
CURRENTLY BLANKETS MUCH OF WISCONSIN AND EASTERN MINNESOTA WITH
LITTLE PUSH EASTWARD TO THE CLEARING ON THE WESTERN EDGE OF THESE
CLOUDS. THESE CEILINGS ARE MAINLY IN THE 2KFT TO 4KFT RANGE WITH
RST MORE LIKELY TO STAY MVFR TONIGHT THAN LSE WHERE THE HIGHER
BASED CLOUDS ARE SITUATED. SHORT TERM MODEL TRENDS SHOW SOME DRIER
AIR MOVING IN OVERNIGHT AS THE CORE OF A RIDGE OF HIGH PRESSURE
PUSHES EASTWARD TOWARD THE UPPER MISSISSIPPI RIVER VALLEY. CURRENT
TIMING WOULD SUGGEST A POSSIBLE CLEARING AROUND 9Z OR SO...BUT
CONFIDENCE IS NOT HIGH IN THIS OCCURRING. IF CLOUDS DO
CLEAR...WILL MAINLY BE DEALING WITH SCT TO OVC CIRRUS MOVING
NORTHWARD FROM THE SOUTHERN PLAINS AND LIGHT WINDS WITH THE RIDGE
AXIS IN PLACE.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
246 PM CST MON DEC 19 2011
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...04
LONG TERM...04
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
227 PM CST SUN DEC 18 2011
.SHORT TERM...THROUGH TUESDAY NIGHT
227 PM CST SUN DEC 18 2011
MAIN FORECAST CONCERN IS WITH THE PRECIPITATION CHANCES AND TYPES
TUESDAY AND TUESDAY NIGHT.
SURFACE ANALYSIS THIS AFTERNOON SHOWS AN AREA OF LOW PRESSURE OVER
SOUTHWEST ONTARIO WITH A COLD FRONT EXTENDING SOUTHWEST THROUGH
NORTH DAKOTA.
THE COLD FRONT WILL SLIDE ACROSS THE REGION OVERNIGHT. AS IT
DOES...THE 18.12Z NAM AND 18.18Z RUC SUGGEST THERE WILL BE A
RIBBON OF LOW LEVEL MOISTURE BEHIND THE FRONT THAT SHOULD BE
SUFFICIENT TO ALLOW SATURATION TO OCCUR. THIS SHOULD RESULT IN A
BAND OF STRATUS CLOUDS DEVELOPING ACROSS THE REGION AND HAVE
RAISED THE CLOUD COVER TO HANDLE THIS. OBSERVATIONS ACROSS
SASKATCHEWAN AND MANITOBA DO INDICATE THE EXISTENCE OF THIS
STRATUS ALREADY. THE NAM BUFKIT SOUNDINGS INDICATE SOME VERTICAL
MOTION THROUGH THIS SATURATED LAYER SUGGESTING THE POTENTIAL FOR
SOME DRIZZLE. HOWEVER...THE RUC DOES NOT SHOW THIS AND WILL LEAVE
OUT THE MENTION OF ANY DRIZZLE.
THE FRONT WILL BECOME STATIONARY SOUTH OF THE AREA MONDAY NIGHT AS
THE UPPER LEVEL LOW OVER THE SOUTHWEST STARTS TO EJECT OUT TO THE
NORTHEAST. AS THIS SYSTEM COMES OUT...BOTH THE NAM AND GFS BRING
BETWEEN 4 AND 8 PVU/S OF VORTICITY ADVECTION IN THE 500-300 MB
LAYER ACROSS THE SOUTHERN PARTS OF THE FORECAST AREA TUESDAY AND
TUESDAY NIGHT. THIS IS EXPECTED TO RESULT IN WEAK TO MODERATE QG
CONVERGENCE OCCURRING ACROSS THE FAR SOUTHERN PARTS OF THE
FORECAST AREA. THERE SHOULD ALSO BE SOME WEAK FRONTOGENESIS IN THE
850-500 MB LAYER OF THE SAME AREA. THERE IS ENOUGH OF A CONSENSUS
IN ALL THE MODELS TO BRING THE PRECIPITATION CHANCES TO ABOUT THE
INTERSTATE 90 CORRIDOR TUESDAY AFTERNOON AND NIGHT. BUFKIT
SOUNDINGS FROM BOTH THE NAM AND GFS SUGGEST THERE MAY NOT BE A LOT
OF ICE PRESENT IN THE CLOUDS AS THIS SYSTEM COMES THROUGH. THE
SOUNDINGS SUGGEST CLOUD TOP TEMPERATURES MAY BE IN THE -10 TO -12C
RANGE AND THERE COULD ALSO BE A BIT OF A WARM LAYER ALOFT AT TIMES
AS WELL. HAVE THUS ADDED IN SOME PROBABILITIES OF FREEZING RAIN
AND WILL HAVE A MIXTURE OF RAIN...SNOW AND FREEZING RAIN. ACTUAL
PRECIPITATION AMOUNTS SHOULD BE VERY LIGHT AND ANY SNOW OR ICE
ACCUMULATIONS THAT OCCUR SHOULD NOT AMOUNT TO MUCH.
.LONG TERM...WEDNESDAY THROUGH SUNDAY
227 PM CST SUN DEC 18 2011
AS THE SYSTEM PULLS AWAY FROM THE AREA WEDNESDAY...THERE COULD
STILL BE A LITTLE BIT OF LINGERING PRECIPITATION ACROSS THE FAR
SOUTHEASTERN PARTS OF THE FORECAST AREA. THE NEXT NORTHERN STREAM
SHORT WAVE TROUGH IS EXPECTED TO COME ACROSS THE UPPER MIDWEST
WEDNESDAY NIGHT AND THURSDAY. MODELS HAVE BEEN INCONSISTENT ON
WHETHER THIS WILL BE ENOUGH TO PRODUCE SOME LIGHT SNOW AS THE WEAK
COLD FRONT COMES THROUGH. FOR NOW...WILL STAY WITH THE CURRENT
MODEL CONSENSUS GRIDS SHOWING THE SNOW CHANCES FARTHER NORTH
CLOSER TO THE SHORT WAVE TROUGH...BUT COULD SEE LATER FORECASTS
ADDING IN SOME SNOW CHANCES FOR THIS SYSTEM. ANOTHER WAVE WILL BE
DROPPING INTO THE UPPER MIDWEST NEXT SUNDAY AND WILL HAVE SOME
SMALL SNOW CHANCES ACROSS THE NORTH WITH THIS SYSTEM.
&&
.AVIATION...THROUGH 18Z MONDAY
1148 AM CST SUN DEC 18 2011
MAIN CONCERN WILL BE COLD FRONTAL PASSAGE TONIGHT ALONG WITH IFR
STRATUS. CURRENTLY...VFR CONDITIONS ACROSS THE AREA WITH MILD
SOUTHWEST FLOW AHEAD OF AN AREA OF LOW PRESSURE TRACKING ALONG THE
U.S./CANADIAN BORDER. A COLD FRONT ASSOCIATED WITH THE LOW WILL
DROP INTO THE AREA LATER THIS EVENING AND EXIT BY DAYBREAK.
WARMING TODAY HAS CAUSED SNOWMELT AND CONSEQUENTLY IS LOADING THE
BOUNDARY LAYER WITH MOISTURE. THIS MOISTURE IS EXPECTED TO
CONVERGE ALONG THE COLD FRONT AS IT DROPS INTO THE AREA LATE THIS
EVENING...AND IS EXPECTED TO PRODUCE SCATTERED STRATUS. BY
08-09Z...COLDER AIR FILTERING INT BEHIND THE FRONT ON NORTHERLY
WINDS IS EXPECTED TO COOL THE RELATIVELY MOIST BOUNDARY LAYER FOR
MORE WIDESPREAD IFR STRATUS FORMATION. THIS IFR STRATUS IS
EXPECTED TO LINGER THROUGH MONDAY MORNING AS MOISTURE IS TRAPPED
BELOW A SUBSIDENCE INVERSION ASSOCIATED WITH A RIDGE OF HIGH
PRESSURE EXTENDING FROM THE NORTHERN PLAINS INTO NORTHERN WI.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
227 PM CST SUN DEC 18 2011
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...04
LONG TERM...04
AVIATION...DAS
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1121 PM CST SAT DEC 17 2011
.SHORT TERM...TONIGHT
901 PM CST SAT DEC 17 2011
THE MAIN CHANGE FOR OVERNIGHT WITH THE FORECAST WAS TO ADD IN SOME
FOG MENTION ACROSS THE REGION.
LOW LEVEL STRATUS HAS CLEARED MUCH OF THE FORECAST AREA WITH THE
BACK EDGE OF IT RUNNING THROUGH TAYLOR/NORTHEAST CLARK DOWN TO
JUNEAU AND ADAMS COUNTY. WITH WESTERLY LOW LEVEL WINDS IN
PLACE...THESE CLOUDS SHOULD CONTINUE TO MARCH EASTWARD OVER THE
NEXT FEW HOURS.
WITH THE COMBINATION OF CLEARING AND WARMER LOW LEVEL AIR
STARTING TO ADVECT INTO THE REGION...18.01Z RUC SOUNDINGS FROM THE
REGION ARE SHOWING A STEEP INVERSION SETTING UP OFF OF THE SURFACE
UP TO AROUND 1KFT. WITH A WEAK SURFACE RIDGE COMING
THROUGH...WINDS HAVE/WILL DROP OFF TO JUST A FEW KNOTS BEFORE
COMING AROUND TO THE SOUTH AROUND DAYBREAK TOMORROW MORNING. WITH
DEW POINTS STILL IN THE MID 20S...ANY RADIATIONAL COOLING SHOULD
LEAD TO SMALL SURFACE DEW POINT DEPRESSIONS.
THESE CONDITIONS ARE EXPECTED TO LEAD TO SOME FOG DEVELOPMENT
OVERNIGHT WITH PLATTEVILLE ALREADY DROPPING DOWN TO 3/4SM. THE TWO
HINDRANCES TO THE FOG DEVELOPMENT IS WITH THE WINDS EXPECTED TO
PICK UP THROUGH THE MORNING ALONG WITH SOME CIRRUS MOVING IN FROM
THE WEST THAT MAY LIMIT RADIATIONAL COOLING. REGARDLESS...IT LOOKS
LIKE ENOUGH OF A CHANCE TO WARRANT PUTTING IN THE FORECAST AT THIS
TIME. WITH TEMPERATURES BELOW FREEZING...THERE COULD BE SOME SLICK
SPOTS THAT DEVELOP ON AREA ROADS THOUGH MANY OF THEM HAVE BEEN
TREATED FOR THE SNOW THAT FELL LAST NIGHT. THERE COULD ALSO BE
SOME HOAR FROST THAT DEVELOPS IN ANY AREAS THAT SEES THE DENSER
FOG. AT THIS POINT...NOT EXPECTING TO HAVE TO ISSUE A DENSE FOG
ADVISORY OVERNIGHT...BUT CONDITIONS WILL BE MONITORED.
.LONG TERM...TUESDAY THROUGH SATURDAY
217 PM CST SAT DEC 17 2011
GOOD AGREEMENT EARLY IN THE PERIOD BETWEEN THE MODELS THAT THE
SURFACE LOW TRACKING ALONG THE COLD FRONT WILL STAY WELL SOUTH OF
THE REGION KEEPING THE AREA DRY THROUGH THE MIDDLE OF THE WEEK.
AFTER THAT THERE ARE SOME DIFFERENCES THAT SHOW UP. THE 17.00Z
ECMWF SHOWS ANOTHER LOW GETTING CUT OFF OVER THE DESERT SOUTHWEST
WITH A PRETTY STRONG NORTHERN STREAM SHORT WAVE TROUGH COMING
ACROSS THE UPPER MIDWEST THURSDAY THROUGH FRIDAY. THE 17.12Z GFS
AND GEM ALSO SHOW A TROUGH INTO THE DESERT SOUTHWEST BUT DO NOT
INDICATE A CUT OFF LOW NOR DO THEY HAVE THE NORTHERN STREAM WAVE.
AS A RESULT...THE ECMWF IS THE ONLY MODEL SHOWING ANY
PRECIPITATION ACROSS THE REGION FOR THURSDAY AND THURSDAY NIGHT.
INTERESTINGLY...THE 17.12Z GFS ENSEMBLE DOES SHOW A LOW PROBABILITY
OF SOME PRECIPITATION THURSDAY SIMILAR TO THE ECMWF. WILL CARRY
JUST A SLIGHT CHANCE OF SOME PRECIPITATION ACROSS THE NORTH TO
HONOR THE ECMWF SOLUTION.
&&
.AVIATION...THROUGH 06Z MONDAY
1121 PM CST SAT DEC 17 2011
THE MAIN CONCERNS OVER THE NEXT 24 HOURS ARE WITH THE SHALLOW
GROUND FOG EARLY THIS MORNING AND ALSO WITH A POSSIBLE STRATUS
DECK THAT COULD FORM SUNDAY EVENING.
CURRENTLY...A WEAK RIDGE OF HIGH PRESSURE IS SET UP ACROSS THE
REGION WITH LIGHT WINDS AND MAINLY CLEAR SKIES OUTSIDE OF SOME
CIRRUS. WITH A FRESH SNOW PACK IN PLACE FROM SOUTHEAST MINNESOTA
INTO SOUTHWEST WISCONSIN...IDEAL RADIATIONAL COOLING CONDITIONS
ARE TAKING PLACE. THIS HAS CREATED A VERY SHARP SURFACE BASED
INVERSION THAT IS TRAPPING ANY LOW LEVEL MOISTURE UNDER IT.
VISIBILITY HAVE FOR THE MOST PART BEEN VFR ACROSS THE
REGION...THOUGH A FEW SPOTS HAVE QUICKLY DROPPED TO AROUND A MILE
SUCH AS PLATTEVILLE AND WATERLOO. THE POTENTIAL IS THERE FOR BOTH
RST AND LSE TO SEE SOME OF THESE DROPS THIS MORNING...SO HAVE PUT
IN A TEMPO GROUP FROM 8Z-12Z TO ACCOUNT FOR ANY VFR TO IFR DROPS.
WINDS PICK UP QUICKLY AROUND DAYBREAK AND SHOULD MIX OUT ANY
REMNANT FOG WITH GUSTS UP IN THE 18-22KT RANGE IN THE AFTERNOON.
WITH WARM TEMPERATURES ABOVE FREEZING TODAY...THE SNOW PACK IS
EXPECTED TO MELT AWAY TODAY AND ADD SOME MOISTURE TO THE BOUNDARY
LAYER. 18.00Z NAM FORECAST SOUNDINGS SHOW A SHALLOW SATURATED
LAYER FORMING THIS EVENING AND LASTING OVERNIGHT AS A COLD FRONT
APPROACHES THE REGION. AT THIS POINT...HAVE HINTED AT THIS
STRATUS DECK FORMING AROUND 00Z TONIGHT IN THE TAFS.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
217 PM CST SAT DEC 17 2011
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...HALBACH
LONG TERM...04
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
419 AM EST TUE DEC 20 2011
.SHORT TERM.../TODAY THROUGH WEDNESDAY NIGHT/
STRONG ISENTROPIC LIFT HAS ALLOWED FOR BAND OF PERSISTENT PRECIP
FROM SOUTHERN QUARTER OR SO OF THE FORECAST AREA BACK TO THE WEST
ACROSS MUCH OF CENTRAL AND SOUTHERN ILLINOIS. EARLIER TAMDAR
SOUNDINGS INDICATED THAT RISK FOR SNOW MAY BE MINIMAL INTO TUES
MORNING. HOWEVER...RECENT SFC OBS AND CALL AROUND TO CENTRAL
DISPATCHES IN SOUTHERN AREAS SHOWS RAIN HAS BEEN MIXING WITH AND
EVEN CHANGING TO SOME LIGHT SNOW. MAIN SWITCH OVER HAS BEEN
OCCURRING IN SE AREAS WHERE NE FLOW HAS ALLOWED SLIGHTLY COLDER
TEMPS TO MIX FURTHER THROUGH THE COLUMN. SFC TEMPS WERE ABOVE
FREEZING ACROSS THE AREA WITH ANY SNOW MELTING AS IT FALLS. OF
CONCERN IS NEW 6Z NAM12 WHICH SUGGEST A SWATH OF LOCALLY HEAVIER
PRECIP MAY ARRIVE TOWARDS 12Z AND FALL IN AREA WHERE COOLING MAY BE
MAXIMIZED. GRIDS HAVE HAD LIGHT ACCUMS IN FOR SEVERAL DAYS AND HAVE
KEPT THIS THINKING GENERALLY THE SAME THROUGH THIS MORNING. KFWA
OBSERVER JUST CONTACTED US WITH A FEW TENTHS OF AN INCH ON VEHICLES
BUT EVERYTHING MELTING ON THE GROUND. BLEND OF RUC AND LOCAL WRF WAS
USED TO GET POP LAYOUT TODAY WITH VERY TIGHT CUT OFF TO THE NORTH AS
LOCATIONS NORTH OF US 6 MAY SEE LITTLE OR NO PRECIPITATION. LOCAL
WRF AND HRRR WANT TO QUICKLY DRY THINGS OUT IN THE 21 TO 00Z TIME
FRAME AS BEST FORCING SHIFTS NORTH WITH THE WARM FRONT PASSING
THROUGH. THIS COULD LEAVE MUCH OF THE AREA EITHER DRY OR WITH SOME
AREAS OF DRIZZLE. HAVE MADE NO CHANGES TO THIS AFTERNOON WITH CHC
POPS REMAINING IN FAR N AND NW AREAS AND LIKELY REMAINDER OF THE
AREA. WILL LET DAY SHIFT MONITOR TRENDS.
UPPER LOW WILL TRACK TOWARDS THE REGION LATER TONIGHT INTO WEDS.
MODELS STILL VARY ON PATH OF THIS FEATURE EITHER BEING OVER THE AREA
OR JUST TO THE SE. STILL THINK MOST AREAS WILL SEE A CHANCE FOR
LIGHT RAIN FOR AT LEAST A 6 TO 12 HOUR PERIOD BEFORE ENDING BY WEDS
EVENING.
IN TERMS OF TEMPS THROUGH THE PERIOD...EXPECTING LITTLE OVERALL
CHANGE IN SFC TEMPS TODAY ACROSS THE NORTH AND A SLOW WARM UP IN
SOUTHERN AREAS ESPECIALLY AS WARM FRONT MOVES NORTH. IF ANY BREAKS
IN THE CLOUDS CAN FORM LATER THIS AFTERNOON...COULD SEE HIGHS WARMER
THAN FORECAST. HOWEVER...OBS TO THE SOUTH SHOW PRETTY EXTENSIVE
CLOUD COVER SO WILL HOLD OFF ON ANY CHANGES FOR HIGHS TODAY. HIGHS
ON WEDS COULD VARY GREATLY DEPENDING ON THE TRACK OF THE UPPER LOW
WITH WARMEST READINGS SE WHERE HIGHS COULD EASILY CLIMB INTO THE
50S. OVERNIGHT LOWS BOTH NIGHTS EXPECTED TO REMAIN ABOVE FREEZING.
&&
.LONG TERM.../THURSDAY THROUGH MONDAY/
NEXT IN SERIES OF SRN STREAMS SHRTWVS EMANATING FROM SPLIT FLOW OVER
WRN U.S. WILL LIFT RAPIDLY NE FROM THE SRN PLAINS TO THE LWR OH
VALLEY THU EVE. THIS SYSTEM SHOULD BE CONSIDERABLY WEAKER THAN ITS
PREDECESSOR DUE TO MORE SHEARING FM INTERACTION WITH NRN STREAM
SHRTWV MOVG ESE INTO THE UPR GRTLKS AT THE SAME TIME. PER GFS
SOLUTION... SFC/H85 BAROCLINIC ZONE EXPECTED TO REMAIN FAR ENOUGH TO
THE S-SE TO KEEP NWRN EDGE OF PRECIP SHIELD WITH THIS SYSTEM JUST SE
OF OUR CWA. WK WAA AHEAD OF THE NRN STREAM SHRTWV/CDFNT SHOULD ALLOW
HIGHS TO REACH THE L-M40S ACROSS THE AREA DESPITE CONSIDERABLE
CLOUDINESS.
CDFNT WILL MOVE THROUGH THE AREA BY THU EVE WITH HIGH PRESSURE OVER
THE NRN PLAINS BUILDING EAST ACROSS THE WRN GRTLKS IN ITS WAKE. WK
CONVERGENCE ALONG FRONT AS IT MERGES WITH CIRCULATION OF SURFACE LOW
TO THE SE SUGGESTS JUST SOME CLOUDINESS WILL ACCOMPANY IT... BUT
LITTLE CHC OF MEASURABLE PRECIP. FAIRLY WK CAA WITH H85 TEMPS ONLY
FALLING TO -2C/-4C ACROSS THE CWA COMBINED WITH CLOUDINESS SUGGESTS
LOWS WILL ONLY BE IN THE U20S/L30S THU NGT.
FOR THE EXTENDED DAYS 4-7...MEDIUM RANGE MODELS IN DECENT AGREEMENT
INDICATING MEAN TROF OVER WRN U.S. IN SHORT TERM WILL PROGRESS TO
NEAR THE EAST COAST BY THE END OF THE LONG TERM PERIOD. THIS SHOULD
RESULT IN A GRADUAL COOL DOWN OVER THE HOLIDAY WEEKEND WITH A WARMUP
EARLY NEXT WEEK AS RIDGING ALOFT MOVES INTO THE GRTLKS IN THE WAKE
OF THIS TROF. SPLIT FLOW WILL PERSIST AS THE MEAN TROF MOVES EAST...
AT LEAST THROUGH FRIDAY OR SAT. MODELS HAVE VERY DIFFERENT
TIMING/TRACK/INTENSITY WITH SHRTWV LIFTING OUT OF THE SRN STREAM
FLOW OVER THE WEEKEND... THUS LITTLE CONFIDENCE IN THE POPS SATURDAY
BUT MAINTAINED FCST CONTINUITY BY FOLLOWING GFS SOLUTION WHICH
INDICATES A CHC OF RAIN/SNOW IN OUR AREA AROUND THIS PERIOD. IN THE
WAKE OF THIS SYSTEM... NRN STREAM TROF PROGGED TO STRENGTHEN/DIG SE
A BIT WHICH SHOULD ALLOW AIRMASS OVER THE WRN GRTLKS TO BECOME COLD
ENOUGH FOR SOME LAKE EFFECT SNOW SHOWERS BY LATE SUNDAY... THOUGH
DOESN`T LOOK LIKE A FAVORABLE SETUP FOR SGFNT LES ATTM WITH GFS
INDICATING FAIRLY LOW INVERSION HEIGHTS.
&&
.AVIATION...
CONDITIONS WILL CONTINUE TO GO DOWNHILL AT KFWA AS CONTINUED FLOW
OF MOISTURE OVER FRONTAL BOUNDARY TO THE SOUTH SETS THE STAGE FOR
PERIODS OF LIGHT PRECIP AND EXPANSIVE LOW CLOUDS. RADAR TRENDS
SUGGEST PRECIP STARTING TO MAKE A RUN FOR KFWA ATTM AND SPECIAL
JUST CAME IN AT KFWA FOR LIGHT RAIN STARTING AND DOWN TO 39.
TAMDAR SOUNDING OUT OF FORT WAYNE A FEW HOURS AGO SUPPORTS ALL
RAIN WITH A NEARLY 5000 FOOT DEEP LAYER OF TEMPS ABOVE FREEZING.
THAT BEING SAID...ONLY TALKING A FEW DEGREES ABOVE FREEZING AND SO
CLOSE ENOUGH TO KEEP MIX MENTION IN. HAVE KEPT WITH MIX MENTION
FOR SEVERAL HOURS AND WILL MONITOR FOR REMOVAL. LARGER AREA
WORKING ACROSS ILLINOIS WILL MOVE IN CLOSER TO 12Z AND BRING BEST
CHANCE FOR PRECIP. RAIN LOOKS TO SHIFT NORTH OF THE AREA POSSIBLY
BY LATE AFTERNOON BUT WILL QUICKLY MOVE BACK IN AND REMAIN IN
PLACE WITH IFR CIGS THROUGH 6Z.
MUCH MORE DIFFICULT FORECAST AT KSBN WHERE DRIER AIR HAS WORKED IN
AND ONLY MID/HIGH CLOUDS EXIST. LOWER CIGS NOT TOO FAR AWAY WIT
KASW HAVING A MVFR CIG ATTM. HAVE KEPT KSBN VFR THROUGH 17Z BUT
WOULD NOT BE SURPRISED IF AN AMENDMENT WILL BE NEEDED OVERNIGHT AS
MODELS GENERALLY TOO FAR SOUTH WITH CURRENT PRECIP AND CLOUD COVER
LAYOUT.
RAIN LOOKS TO EVENTUALLY MOVE IN THIS AFTERNOON WITH BETTER
CHANCES TOWARD THE END OF THE CURRENT FORECAST PERIOD. FURTHER
CHANGES WILL BE NEEDED TO KSBN OVER THE NEXT 6 HOURS AS EVOLUTION
OF PRECIP SHIELD AND EFFECTS OF DRY AIR BECOME BETTER ESTABLISHED.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SHORT TERM...FISHER
LONG TERM...JT
AVIATION...FISHER
AREA FORECAST DISCUSSION
NWS QUAD CITIES IA IL
1106 PM CST MON DEC 19 2011
.AVIATION...
A STORM SYSTEM WILL SLOWLY MOVE TOWARD IOWA AND ILLINOIS DURING
THE NEXT 24 HOURS. THIS STORM WILL SPREAD MVFR TO IFR CIGS AND
VISIBILITIES OVER SOUTHERN PARTS OF IOWA AND CENTRAL AND SOUTHERN
ILLINOIS. THIS WILL OCCUR MAINLY IN THE
FORM OF DRIZZLE AND LOW CLOUDS. SNOW RAIN MIXED ARE POSSIBLE
VERY LATE TONIGHT AT BRL...BUT THE TIMING OF THE ONSET IS VERY LOW
CONFIDENCE. THUS...IT MAY HOLD OFF UNTIL TOWARDS 15Z. NORTHEAST
WINDS AROUND 5 TO 8 KTS WILL BECOME LIGHT AND VARIABLE BY LATE
AFTERNOON TUESDAY. FROM LATE AFTERNOON THROUGH THE NIGHT TUESDAY
NIGHT...IFR LOW CLOUDS AND FOG ARE LIKELY...ALONG WITH DRIZZLE.
THIS MAY BRING A PERIOD OF LIFR CONDITIONS TO THE REGION.
&&
.PREV DISCUSSION... /ISSUED 315 PM CST MON DEC 19 2011/
SYNOPSIS...
12Z UA ANALYSIS HAD THE STORM SYSTEM DEVELOPING IN THE SOUTHERN
ROCKIES WITH A LLJ OF 40-50 KNOTS TRANSPORTING MOISTURE NORTH INTO
THE PLAINS AND OHIO VALLEY. AN 850MB COLD FRONT RAN FROM NORTHERN
LAKE HURON INTO NORTHEAST COLORADO. SATELLITE AND RADAR TRENDS
THROUGH MID AFTERNOON SHOWED INCREASING CLOUDS ACROSS THE AREA WITH
PRECIPITATION GENERALLY SOUTH OF A KSTJ TO KUIN LINE.
18Z SFC ANALYSIS HAD A COLD FRONT RUNNING FROM KOSC...TO KMCI...TO
AROUND KDHT. LOW PRESSURES FROM THE DEVELOPING STORM SYSTEM WERE
SOUTH OF KTCC AND NEAR KPPA. DEW POINTS WERE IN THE 40S JUST AHEAD
OF THE COLD FRONT INTO THE OHIO VALLEY WITH 50S CROSSING THE RED
RIVER INTO OKLAHOMA. DEW POINTS IN THE 20S AND 30S WERE ACROSS MUCH
OF THE NORTHERN/CENTRAL PLAINS AND UPPER MIDWEST.
SHORT TERM...TONIGHT AND TUESDAY...
THE MAIN QUESTION IS HOW LONG WILL THE DRY AIR KEEP THE
PRECIPITATION AT BAY TONIGHT INTO TUESDAY. BASED ON 12Z UA DATA...
THE WRF INITIALIZED A LITTLE BETTER THAN THE OTHER MODELS BASED ON
LOW LEVEL MOISTURE.
CONDENSATION PRESSURE DEFICITS ON EITHER STANDARD SURFACES OR THE
290-925K THETA SFC HAVE BEEN DEPICTING WELL THE AREAL COVERAGE OF
THE PRECIPITATION LATE THIS MORNING AND AFTERNOON. ALL MODELS HAVE
GENERALLY SHOWED THIS BUT THE RUC TRENDS HAVE DONE VERY WELL AND THE
RUC WILL BE USED FOR THE IMMEDIATE SHORT TERM.
BASED ON THE RUC CONDENSATION PRESSURE DEFICIT TRENDS...THE EARLY
EVENING WILL REMAIN DRY ACROSS THE ENTIRE AREA. BETWEEN 9 PM AND
MIDNIGHT PRECIPITATION WILL ADVECT/DEVELOP GENERALLY SOUTH OF A KOTM
TO KPIA LINE. FCST SOUNDINGS SHOW A TOP DOWN SATURATION TAKING PLACE
SO THERE WILL BE PLENTY OF EVAPORATIVE COOLING TAKING PLACE. THUS A
RAIN/SNOW MIX WILL DEVELOP THAT WILL LIKELY HAVE A BRIEF PERIOD OF
SLEET AS THE PRECIPITATION DEVELOPS. THERE IS A CONCERN BASED ON HOW
WARM IT HAS GOTTEN TODAY THAT PTYPE COULD BE MORE LIQUID THAN
FREEZING OR FROZEN.
AFTER MIDNIGHT...THE PRECIPITATION SHIELD WILL SLOWLY MOVE
NORTHWARD...REACHING A KOTM TO KGBG LINE AROUND 3 AM AND ROUGHLY A
KOOA TO KC75 LINE AROUND 12Z. THE I-80 CORRIDOR ON NORTH WILL REMAIN
DRY THROUGH SUNRISE. MINS TONIGHT WILL BE HIGHLY DEPENDENT ON CLOUD
COVER AND HOW THE PRECIPITATION SHIELD EVOLVES.
SNOW AMOUNTS SHOULD BE ONE HALF INCH OR LESS TONIGHT.
ON TUESDAY...THE PRECIPITATION SHIELD WILL CONTINUE MOVING NORTH AND
REACH I-80 ROUGHLY AROUND 9 AM AND SHOULD BE AROUND A VINTON TO MT
CARROLL LINE BY MID DAY. THE IMMEDIATE HWY 20 CORRIDOR IS EXPECTED
REMAIN DRY DURING THE MORNING HOURS. EVAPORATIVE COOLING WILL
CONTINUE TO PLAY SIGNIFICANTLY IN PTYPE WITH A RAIN/SNOW MIX ALONG
WITH A BRIEF PERIOD OF SLEET.
BY LATE MORNING AND INTO THE AFTERNOON HOURS...THE OVERALL FORCING
ACROSS THE AREA DECREASES. THE OVERALL PRECIPITATION INTENSITY WILL
LET UP AND A CHANGE OVER TO MAINLY RAIN IS EXPECTED EXCEPT ACROSS
ROUGHLY THE NORTHWEST THIRD OR SO OF THE CWFA WHERE A MIX IS STILL
EXPECTED. THE RAIN MAY STOP OR GO TO MORE DRIZZLE DURING THE
AFTERNOON HOURS.
SNOW AMOUNTS ON TUESDAY SHOULD BE ONE HALF INCH OR LESS. ..08..
LONG TERM...TUESDAY NIGHT THROUGH NEXT MONDAY...
TUESDAY NIGHT AND WEDNESDAY...LATEST 12Z RUNS HAVE SHIFTED SLIGHTLY
BACK SOUTHWARD WITH RESPECT TO MAIN SFC LOW AND MID LEVEL
PROPAGATION PATHS LATER TUE THROUGH WED. WILL SIDE THE NEW 12Z RUN
ECMWF AND NAM WHICH ARE IN GOOD AGREEMENT WITH THEIR MASS FIELDS
WITH EACH OTHER AND THERE SOLUTIONS ARE IN THE MIDDLE OF THE ROAD OF
THE ENSEMBLES OF THESE FEATURES. THESE ACCEPTED SOLUTIONS SUGGEST
THAT THE SFC LOW WILL BE ACRS FAR SOUTHWEST MO AT 00Z WED...AND MOVE
NORTHEASTWARD TO THE EAST CENTRAL IL/WEST CENTRAL INDIANA BORDER
REGION BY 12Z WED WITH EYES ON THE WESTERN BASIN OF LK ERIE BY
MIDDAY WED. UPPER LOW TILTED TO THE NORTHWEST OF THE LLVL CYCLONE
WILL STILL LOOK TO PROGRESS ACRS THE SOUTHWEST HALF OF THE CWA BY
WED MORNING STILL IN A CLOSED FASHION AND THEN LOOK TO OPEN UP ON
THE WAY TO OVER THE SOUTH HALF OF LK MI BY WED AFTERNOON. ACCEPTED
THERMAL PROFILES SUGGEST LIGHT RAIN ACRS THE SOUTHEAST HALF OF THE
DVN CWA TUE EVENING WITH SOME SLEET POSSIBLY MIXED IN THE NORTHERN
FRINGE OF THE RAIN AT SFC BAND UP ALONG THE SOUTHERN I80 CORRIDOR.
WITH THE MODELS STILL SUGGESTING THE MAIN THRUST OF WARM MOIST
CONVEYOR SHUNTED OFF TO THE EAST AND SOUTHEAST OF THE AREA BY LATE
TUE...THE APPROACHING UPPER LOW WILL ONLY HAVE TO WORK WITH
SECONDARY MOISTURE FEED AND THUS ONLY A LIGHT PRECIP EVENT STILL
LOOKS ON TAP FOR TUE NIGHT FOR THE MAJORITY OF THE DVN CWA. THERMAL
PROFILES TUE EVENING ALONG AND NORTH OF A LINE FROM MT CARROLL IL...
TO CID AND SOUTHWEST OF IOWA CITY SUGGEST LIGHT SNOW AND SLEET IN
THESE AREAS TUE EVENING...AND ONLY FLURRIES ALONG AND NORTH OF THE
HWY 20 CORRIDOR. SNOW AND SLEET ACCUMS UNDER AN INCH TUE EVENING IN
THESE AREAS...BUT A CHANCE OF A NARROW SWATH OF 1-2 INCHES OF
SNOW ACCUM ON THE NORTHERN FRINGE OF RAIN/SLEET TRANSITION TO SNOW
BAND FROM WILLIAMSBURG TO CLINTON IA BY MID TUE EVENING. THEN IN-
WRAPPING MID LEVEL DRYING SHOULD SWITCH ALMOST ALL THE PRECIP TO
MAINLY DRIZZLE OR FREEZING DRIZZLE FROM MID EVENING THROUGH 12 AM-1
AM CST. AREAS OF TEMPORARY DENSE FOG POSSIBLE TOO BUT WILL LEAVE
OUT MENTION AT THIS POINT. THEN WITH THE APPROACH OF THE MID LEVEL
LOW AFTER MIDNIGHT...THE FCST SOUNDINGS SATURATE DEEPER AGAIN AND
SUPPORT A BAND OF SECONDARY DEF ZONE RAINS CLIPPING THE SOUTHEAST
THIRD OF THE CWA INTO EARLY WED MORNING WITH UP TO .3 OR .4 INCHES OF
RAIN POSSIBLE BY 8 AM CST WED. THE WESTERN FRINGE OF THIS DEF ZONE
RAIN MAY MIX WITH SNOW BY WED MORNING WITH LIGHT SLUSHY SNOW ACCUMS
UP TO AN INCH. FURTHER NORTH AND WEST OVER THE REST OF THE CWA...
LIGHT DRIZZLE OR FREEZING DRIZZLE DEPENDING ON THE SFC TEMPS WILL
LOOK TO TOP-DOWN COOL AND SATURATE INTO ALL LIGHT SNOW PARAMETERS
AFTER 1 AM WITH LIGHT ADDITIONAL SNOW ACCUMS POSSIBLE UP TO AN INCH
BY WED MORNING WHEN THE PRECIP WILL BE ON THE MOVE OUT OF THE LOCAL
FCST AREA. WILL STILL HAVE TO BE WARY OF SOME BANDED SNOWS OF AT
LEAST 1-2 INCHES AS THE UPPER LOW APPROACHES LATE TUE NIGHT IF
DYNAMICAL/TOP DOWN COOLING OCCURS QUICKER THAN CURRENTLY ANTICIPATED.
THERE STILL MAY BE A NEED FOR A WINTER WEATHER ADVISORY TUE NIGHT FOR
THE ROUNDS OF LIGHT FREEZING RAIN...FREEZING DRIZZLE...SNOW AND SLEET
MIX WITH AREAS ALONG AND NORTH OF I80 THE MOST LIKELY TARGET. THE
REST OF WED AND WED NIGHT SHOULD HAVE NO REAL WX MAKERS AND BE QUIET.
THURSDAY THROUGH FRIDAY...DEPENDING ON WHAT LIES IN THE WAKE OF THE
MID WEEK SYSTEM STREAM FLOW AND BAROCLINICITY-WISE...A RE-LOADING
SOUTHWESTERN CONUS TROF AND ACTIVE NORTHERN STREAM ACRS THE WEST
HALF OF THE CONUS HAVE ALL THE MEDIUM RANGE MODELS A FLUTTER THIS
PERIOD. MUCH UNCERTAINTY OF COURSE...BUT SIGNALS OF SOUTH-WESTERLIES
IN THE SOUTHERN STREAM REORGANIZING SOUTH AND SOUTHWEST OF THE
LOCAL AREA JUST SOUTH OF CONFLUENT FLOW MAY ALLOW SOME ELEVATED
FRONTOGENETICAL FORCING ALONG AND BEHIND A LLVL FRONT GETTING
ALIGNED PARALLEL TO THIS MEAN FLOW TO GENERATE SOME LIGHT SNOW OR
FLURRIES ACRS THE CWA EITHER LATE THU OR THU NIGHT INTO FRI
MORNING. AT THIS POINT WITH THE DRY LOOKING VERTICAL PROFILES...JUST
A DUSTING TO UNDER AN INCH WOULD ALL THAT WOULD BE POSSIBLE BY FRI
MORNING AND MAINLY FROM IOWA CITY TO FREEPORT IL AND NORTHWARD.
THE 12Z RUN UKMET...GEM AN GFS ARE EITHER DRY OR JUST HAVE FLURRIES
FOR THU NIGHT. LONGER RANGE SIGNALS SUGGEST PHASING ISSUES A PLENTY
AS THE DIGGING NORTHERN STREAM UPPER TROF OVER CENTRAL CANADA TRIES
TO INTERACT WITH THE SOUTHWEST PLAINS TROFFINESS. THE MAJORITY OF
THE LONGER RANGE MODELS HANDLE THIS PROCESS IN A WAY THAT ANY
SOUTHERN STREAM WX MAKER AND IT/S ASSOCIATED PRECIP REMAINS ALONG
OR SOUTH OF THE DVN CWA FROM FRI INTO SAT. BUT THE 12Z GFS MUCH
MORE OMINOUS AND DEVELOPED UPSTREAM. IT PHASES THE STREAMS IN A WAY
THAT A STORM SYSTEM WITH AT LEAST HIGHER END ADVISORY SNOWS/2-5+
INCHES IMPACTS THE ENTIRE CWA FRI NIGHT INTO SAT MORNING. WILL WATCH
FURTHER TRENDS OF COURSE WITH ADDITIONAL RUNS OVER THE NEXT 24-48
HRS. WILL GO WITH SEASONABLE TEMPS FOR THU THROUGH FRI FOR NOW.
SATURDAY THROUGH MONDAY...ENSEMBLES AND TELECONNECTIONS OVER THE
HOLIDAY WEEKEND SUGGEST SOME AO/ARCTIC OSCILLATION INFLUENCE AS
GENERAL L/W TROFFINESS TRIES TO ESTABLISH THIS PERIOD AND INTO EARLY
NEXT WEEK ACRS THE UPPER MIDWEST AND GRT LKS. THIS PERIOD ALSO LOOKS
GENERALLY DRY AFTER SAT WITH SOME RE-ENFORCING COOL SHOTS OUT OF
CANADA POSSIBLE FOR SEASONABLE OR SOMEWHAT BELOW TEMPS INTO NEXT
MONDAY. CAN/T RULE OUT SOME FLURRIES ON LEADING EDGES OF COOL DUMPS
OR WEAK WAVES EMBEDDED IN NORTHWESTERLY CYCLONIC FLOW...BUT WILL GO
MAINLY DRY FOR NOW. ..12..
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
232 AM CST TUE DEC 20 2011
.DISCUSSION...
DAYS 1-2...
00Z TUESDAY UPPER AIR ANALYSIS PLACED A 850MB AND 700MB
BAROCLINIC ZONE FROM JUST NORTH OF ELKHART TO NEAR HAYS. THE UPPER
LOW WAS POSITIONED NEAR AMARILLO. STILL OBSERVING GOOD MOISTURE
AND WARM AIR ADVECTION ACROSS CENTRAL AND PARTS OF SOUTHWEST
KANSAS AS OUR UPPER LOW MOVES TOWARDS NORTHWEST OKLAHOMA EARLIER
THIS MORNING. JET STREAK DYNAMICS NEAR THE LEFT EXIT REGION OF
250MB JET WILL BE LOCATED ACROSS PORTIONS OF NORTH CENTRAL KANSAS
EARLY THIS MORNING SO AT THIS TIME BASED ON THE LOCATION OF THE
MID LEVEL FRONTOGENESIS IT WOULD APPEAR THAT PERIODS OF MODERATE
SNOW STILL WILL BE POSSIBLE IN AREAS ALONG AND NORTH OF HIGHWAY
156. THE NAM, RUC, AND HRRR WERE ALSO ALL IN DECENT AGREEMENT WITH
PRECIPITATION CONTINUING THROUGH THE EARLY MORNING HOURS IN THIS
AREA SO INITIAL THOUGHTS WILL BE TO FOLLOW THE GENERAL TRENDS OF
THE NAM,RUC AND HRRR OVER THE NEXT 6-9 HOURS. FURTHER WEST NEAR
THE COLORADO BORDER AND AREAS SOUTH NEAR THE OKLAHOMA BORDER THE
PRECIPITATION SHOULD BE STARTING TO TAPER OFF.
WINDS STILL WILL BE AN ISSUE EARLY TUESDAY MORNING GIVEN THE
LOCATION OF THE PRESSURE GRADIENT NORTHWEST OF THE SURFACE LOW
ALONG WITH THE CURRENT VAD WINDS AND PROFILER DATA. ALTHOUGH WIND
SPEEDS ARE NOT EXPECTED TO BE AS STRONG AS YESTERDAY, IT DOES
APPEAR THAT SOME REDUCED VISIBILITIES WILL CONTINUE IN THE
BLIZZARD WARNING AREA. LOCATIONS SOUTH OF HIGHWAY 156 WILL SEE
IMPROVING CONDITIONS EARLY THIS MORNING BUT GIVEN ONGOING SNOW,
BLOWING SNOW AND CURRENT CONDITIONS HAVE DECIDED NOT TO BEGIN
TRIMMING THE BLIZZARD WARNING YET.
BY MID DAY ISENTROPIC DOWN GLIDE WILL BEGIN TO DEVELOP WEST OF
OUR UPPER LOW WHICH WILL BE LOCATED NEAR SOUTH CENTRAL KANSAS. A
SURFACE HIGH WILL THEN BEGIN TO BUILD INTO WESTERN KANSAS FROM THE
NORTHWEST. MODEL SOUNDINGS CONTINUE TO SUGGEST TO CLOUD COVER
THROUGH MUCH OF THE DAY SO BASED ON THIS AND COLD AIR ADVECTION
OCCURRING OVER THE SNOW PACK WILL UNDERCUT GUIDANCE FOR HIGHS
TODAY.
TONIGHT SKIES WILL CLEAR AS WINDS DECREASE TO LESS THAN 10KTS.
WINDS NOT IDEAL FOR A GREAT NIGHT OF RADIATION COOLING BUT
CONDITIONS STILL FAVOR UNDERCUTTING CURRENT GUIDANCE AND STAYING
CLOSE TO THE CURRENT FORECAST OF WITH LOWS EARLY WEDNESDAY MORNING
IN THE SINGLE DIGITS.
WEDNESDAY SHOULD BE SUNNY AS WESTERLY DOWNSLOPE FLOW IMPROVES
ACROSS WESTERN KANSAS. DECENT WARMING OCCURS ABOVE THE SURFACE BUT
BASED ON SNOWFALL EXPECTED ACROSS SOUTHWEST KANSAS FEEL MUCH OF
THE WARMING WILL GO INTO SNOW MELT. AS A RESULT WILL UNDERCUT
GUIDANCE ONCE AGAIN AND FAVOR THE PREVIOUS FORECAST WHICH IS CLOSE
TO 10F COOLER THAN THE COOLEST GUIDANCE.
DAYS 3-7...
.LONG TERM /THURSDAY THROUGH MONDAY/
A PROGRESSIVE LONGWAVE PATTERN IS IN STORE FOR THE EXTENDED PERIOD,
WITH AT LEAST A COUPLE OF ADDITIONAL COLD FRONTAL PASSAGES ACROSS
THE CENTRAL HIGH PLAINS.
AFTER THE MAJOR SYSTEM THAT IS CAUSING THE BLIZZARD RIGHT NOW OVER
WESTERN KANSAS LIFTS EASTWARD INTO THE UPPER MIDWEST ON TUESDAY
NIGHT AND WEDNESDAY, ANOTHER PAIR OF SHARP MID LEVEL IMPULSES WILL
BE ROTATING THROUGH THE MEAN TROUGH. THE FIRST WILL ROTATE SOUTHWARD
FROM THE NORTHERN ROCKIES AND THE SECOND, JUST AHEAD OF THE NORTHERN
STREAM SHORTWAVE, FROM THE DESERT SOUTHWEST. FROM A LOOK AT THE GFS
AND ECMWF THE TWO WAVES APPEAR TO ENHANCE THE MID LEVEL BAROCLINICITY
ACROSS WESTERN KANSAS ON THURSDAY, WHILE A SURFACE COLD FRONT DIVES
SOUTHWARD ACROSS THE AREA EARLY IN THE DAY. BOTH MODELS HAVE BEEN
CONSISTENT IN PRODUCING BETWEEN 0.05" AND 0.15" OF PRECIPITATION
TIED TO THE LEADING SHORTWAVE, WITH POST SURFACE FRONT QPF. QUITE COLD
850 MB AIR ABOUT -5 T0 -8 SHOULD ENSURE THE PRECIPITATION TYPE WOULD
BE SNOW, AND AS A RESULT, IT IS POSSIBLE CENTRAL KANSAS AND MUCH OF
SOUTHWEST WILL BE EXPERIENCING ADDITIONAL, BUT PROBABLY MINOR
ACCUMULATIONS ON THURSDAY AFTERNOON. THE REMAINDER OF THE FORECAST
DOES LOOK DRY, BUT COLD. THE SECOND OF THESE UPPER SHORTWAVES
ROTATES THROUGH THE MEAN TROUGH ON FRIDAY AND SURFACE WINDS BEGIN TO
WEAKEN AS THE UPPER LEVEL HEIGHT FIELDS BECOME PARALLEL TO THE
MOUNTAIN BARRIER. FRIDAY WILL REMAIN COLD WITH VERY WEAK SURFACE
WINDS OVER THE AREA, BUT THE 850 MB TEMPERATURES BEGIN TO INCREASE
WITH STRONGER DOWNSLOPE FLOW OVER THE SNOWPACK. MODELS SEEM TO BUMP
MAXIMUM TEMPERATURES ABOUT 5 DEGREES ON SATURDAY AFTERNOON, BUT THIS
IS STILL WELL BELOW NORMAL. THE MODELS CONTINUE THOUGH THE END OF
THE WEEKEND DRY AND COOL WITH DEEP NORTHWEST FLOW OVER THE HIGH
PLAINS REGION INTO MONDAY.
&&
.AVIATION...
FOR THE 06Z TAF ISSUANCE... BLIZZARD OR NEAR BLIZZARD CONDITIONS
WILL CONTINUE THROUGH EARLY TUESDAY MORNING WITH THE DOMINANT
FLIGHT CATEGORY BEING VLIFR AT GCK AND DDC THROUGH MUCH OF THE
NIGHT TOWARD DAYBREAK. WIND SPEEDS WILL GRADUALLY DECREASE BY
DAYBREAK WITH VISIBILITIES IMPROVING AS WELL. AFTER THE SNOW
CEASES...LOW OVERCAST WILL LIKELY PERSIST THROUGH AT LEAST THE
EARLY AFTERNOON BEFORE CLEARING TAKES PLACE AND VFR CONDITIONS
RESUME. -UMSCHEID
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 27 9 30 14 / 90 0 0 10
GCK 28 6 29 13 / 90 0 0 10
EHA 27 5 29 13 / 50 0 0 10
LBL 27 6 30 15 / 50 0 0 10
HYS 29 6 30 15 / 100 0 0 20
P28 31 14 38 23 / 70 10 0 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WARNING UNTIL NOON CST /11 AM MST/ TODAY FOR KSZ030-031-
043>046-061>066-074>080-084>088.
WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR KSZ081-089-090.
&&
$$
FN18/33/25
AREA FORECAST DISCUSSION...UPDATED
NWS TOPEKA KS
1141 PM CST MON DEC 19 2011
...UPDATE TO AVIATION...
.DISCUSSION...
THE FOCUS OF THIS FORECAST REMAINS ON THE POTENT STORM SYSTEM WHICH
WILL MOVE OFF THE HIGH PLAINS AND BRING RAIN AND SNOW TO ALL OF
NORTHEAST AND EAST CENTRAL KANSAS TONIGHT AND TOMORROW.
20Z WATER VAPOR IMAGERY AND ASSOCIATED RUC ANALYSIS SHOWING THE 500
MB TROUGH MAKING A NORTHEAST TURN AS IT TAKES ON A NEGATIVE TILT
OVER FAR WESTERN TEXAS. STRONG ISENTROPIC LIFT CAUSING A WIDE SHIELD
OF PRECIPITATION MAINLY IN THE FORM OF RAIN TO MOVE NORTHWARD ACROSS
THE AREA. SOME ELEVATED INSTABILITY HAS ALLOWED FOR SOME WEAK
CONVECTION WITHIN THE AREA OF PRECIP ALLOWING FOR A FEW RUMBLES OF
THUNDER. WITH WARM LOW LEVEL TEMPERATURES ACROSS FAR EASTERN KANSAS
THE PRECIPITATION HAS FALLEN AS RAIN THROUGHOUT THE DAY. FURTHER TO
THE WEST COOLER AIR IN THE LOWER TO MID LEVELS HAS FACILITATED A
GRADUAL CHANGE OVER TO A MIX OF RAIN AND SNOW WITH SOME SLEET.
ACROSS CENTRAL AND SOUTHWEST KANSAS WHERE THE COLD AIR IS EVEN
DEEPER PRECIP HAS CHANGED COMPLETELY OVER TO SNOW. THE AREA WITH THE
BIGGEST CONCERN FOR THIS SYSTEM WILL BE ACROSS CENTRAL AND NORTH
CENTRAL KANSAS WHERE SNOW AMOUNTS COULD BE THE HIGHEST. BEST
FRONTOGENETICAL LIFT AND ASSOCIATED HIGHEST OMEGA LOOKS TO PERSIST
ACROSS THE AREA BETWEEN 00Z AND 12Z TONIGHT...AND THIS WILL LIKELY
BRING THE HEAVIEST SNOW...ESPECIALLY TO AREAS OF CENTRAL KANSAS.
GOOD LIFT THROUGH THE -8 TO -14 C DENDRITIC GROWTH LAYER WILL LIKELY
KEEP ALL PRECIP WEST AND NORTH OF A HIAWATHA TO COUNCIL GROVE LINE.
SNOW COULD RAPIDLY INCREASE WITH SNOW RATES APPROACHING 3 TO 5
INCHES OVER A 6 TO 10 HOUR PERIOD ACROSS THAT AREA. COMPLICATING THE
CONDITIONS WILL BE STRONG WINDS ACROSS CENTRAL KANSAS
OVERNIGHT...LEADING TO REDUCED VISIBILITIES AND DANGEROUS TRAVEL
CONDITIONS...ESPECIALLY ALONG INTERSTATE 70. VERY TRICKY PRECIP TYPE
FORECAST FOR AREAS ALONG AND EAST OF THE KANSAS TURNPIKE. FORECAST
SOUNDINGS INDICATE ICE CRYSTALS INTRODUCED INTO THE ATMOSPHERIC
COLUMN...BUT WARMER 850 MB TEMPS COULD TEMPER THE ABILITY OF SNOW TO
REACH THE SURFACE. HOWEVER WITH REAL TIME TEMPS RUNNING A BIT COOLER
THAN MODEL TEMPS...MAY NEED TO CALIBRATE MODELS WITH REAL TIME INFO
AND LEAN TOWARD A SLIGHTLY COOLER SOLUTION...FOR PRECIP TYPES AND
SNOW AMOUNTS ACROSS THE EASTERN COUNTIES. SHOULD PRECIP BE ABLE TO
CHANGE OVER TO SNOW BY 01 TO 03Z EAST OF THE AFOREMENTIONED HIAWATHA
TO COUNCIL GROVE LINE...MAY NEED TO BUMP UP SNOW
AMOUNTS...ESPECIALLY FOR THE TOPEKA AREA. AROUND 12Z TUESDAY MORNING
DRY MID LEVEL AIR WILL PUSH INTO THE AREA WHICH WILL REMOVE ICE
CRYSTALS FROM THE COLUMN FOR A FEW HOURS TUESDAY MORNING. DURING
THIS TIME EXPECT PRECIP TO GO FROM A LIGHT SNOW TO A LIGHT DRIZZLE
OR FREEZING DRIZZLE ACROSS AREAS WHERE TEMPS ARE BELOW FREEZING. BY
LATE TUESDAY AFTERNOON THE MID LEVEL TROWAL WILL SET UP NEAR THE
INTERSTATE 70 CORRIDOR WHICH COULD BRING ANOTHER ROUND OF LIGHT SNOW
FOR TUESDAY AFTERNOON AS THE ATMOSPHERIC COLUMN SHOULD BE COOL
ENOUGH ACROSS THE ENTIRE FORECAST AREA.
WILL NOT MAKE ANY MAJOR CHANGES TO THE ONGOING WARNING/ADVISORY
LOCATIONS AS COUNTIES CURRENTLY UNDER THE WINTER STORM WARNING ARE
STILL ON TRACK TO ACCUMULATE 6 TO 8 INCHES OF SNOW. THE COUNTIES
FURTHEST NORTH AND EAST CONTAIN LESSER CONFIDENCE IN REACHING THE 6
TO 8 INCH RANGE...BUT COUNTIES ALONG INTERSTATE 70 AND WEST OF THE
KANSAS TURNPIKE SHOULD EXPECT AT LEAST 4 TO 6 INCHES OF SNOW...WITH
HIGHER AMOUNTS ACROSS CENTRAL KANSAS. ALSO STRONG WINDS ALONG
INTERSTATE 70 WILL COMPLICATE TRAVEL CONDITIONS AS THEY WILL
COINCIDE WITH THE HEAVY SNOW OVERNIGHT TO BRING LOWERED VISIBILITY
AND DANGEROUS TRAVEL CONDITIONS.
EXPECT LIGHT SNOW TO GRADUALLY COME TO AN END BY EARLY WEDNESDAY
MORNING AS THE UPPER TROUGH EXITS COMPLETELY OUT OF THE AREA WITH
CLEARING SKIES AND SEASONABLE TEMPS.
ANOTHER SYSTEM SWINGS INTO THE PLAINS THURSDAY INTO FRIDAY BUT
WITH A NORTHERLY TRAJECTORY AND MORE LIMITED MOISTURE WILL CARRY
CHANCE TO SLIGHT CHANCE POPS AT THIS TIME. CONDITIONS CLEAR OUT
FOR SATURDAY WITH ANOTHER PUSH OF COLDER AIR SATURDAY NIGHT INTO
SUNDAY.
&&
.AVIATION...
UPPER LOW NOW MOVING EAST NORTHEASTWARD FROM THE TX PANHANDLE WILL
PASS OFF TO THE EAST OF THE TAF SITES AFT 00Z/20. UNTIL THEN...EXPECT
MVFR/IFR SNOW AND SOME SLEET MIX AND GUSTY WINDS FROM 07Z-11Z
BEFORE DRY SLOT OVER NORTHERN OK MOVES THROUGH ALLOWING FOR THE
DEVELOPMENT OF A SNOW/FREEZING DRIZZLE MIX IN IFR CIGS/VSBYS AFT
11Z THEN ENDING NEAR 23Z AS THE UPPER LOW MOVES TO THE EAST WITH
LINGERING MVFR STRATUS AND DECREASING WINDS THROUGH 06Z.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 6 PM CST TUESDAY FOR KSZ009>011-
020>023-034>036.
WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR KSZ008-012-
024-026-037>039.
WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR KSZ040-054-
055.
&&
$$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
1140 PM CST MON DEC 19 2011
.AVIATION...
FOR THE 06Z TAF ISSUANCE...
BLIZZARD OR NEAR BLIZZARD CONDITIONS WILL CONTINUE THROUGH EARLY
TUESDAY MORNING WITH THE DOMINANT FLIGHT CATEGORY BEING VLIFR AT
GCK AND DDC THROUGH MUCH OF THE NIGHT TOWARD DAYBREAK. WIND
SPEEDS WILL GRADUALLY DECREASE BY DAYBREAK WITH VISIBILITIES
IMPROVING AS WELL. AFTER THE SNOW CEASES...LOW OVERCAST WILL
LIKELY PERSIST THROUGH AT LEAST THE EARLY AFTERNOON BEFORE
CLEARING TAKES PLACE AND VFR CONDITIONS RESUME. -UMSCHEID
&&
.PREV DISCUSSION... /ISSUED 506 PM CST MON DEC 19 2011/
AVIATION...
FOR THE 00Z TAF ISSUANCE...CIGS WILL REMAIN LIFR/IFR IN ASSOCIATION
WITH SN/BLSN. CIGS WILL EVENTUALLY IMPROVE TO MVFR TOWARDS 18Z TOMORROW.
WINDS WILL REMAIN STRONG AROUND 30 KT TONIGHT AND THEN ABATE IN THE
20-25 KT BY MORNING. -SUGDEN
PREV DISCUSSION... /ISSUED 320 PM CST MON DEC 19 2011/
SYNOPSIS...
THE OVERALL SYNOPSIS FROM THE 12Z...250MB CHART SHOWED A 80-KNOT
JET STREAK OF WIND FROM SOUTHWEST TEXAS THROUGH SOUTHWEST KANSAS
TO SOUTHERN IOWA. A STRONGER 110KT NORTHWEST JET WAS ENTERING BAJA
CALIFORNIA (W. MEXICO), WHILE A 120-KNOT JET STRETCHED FROM
NORTHERN MINNESOTA TO SOUTHWEST QUEBEC. THE 500MB CHART AT 12Z HAD
A LARGE UPPER LOW PRESSURE SYSTEM OVER EXTREME WESTERN TEXAS, WITH
MOISTURE FLOWING NORTHEASTWARD INTO KANSAS. THE 500MB TEMPERATURE
AT DDC WAS AT 17C. THE 700 MB CHART LOOKED SIMILAR TO THE 500MB
CHART PATTERN, BUT WITH THE H7 LOW PRESSURE OVER SOUTH CENTRAL NEW
MEXICO. A COLD FRONT WAS EVIDENT AT 12Z AT THE 850MB LEVEL ACROSS
NORTH CENTRAL KANSAS, WITH LBF AT -04C AND DDC AT +10C.
DISCUSSION...
DAYS 1-2...
THE UPPER STORM SYSTEM MOVING ACROSS NEW MEXICO AND TEXAS, AND
INTO NORTHERN OKLAHOMA, WAS BRINGING WINTER-LIKE WEATHER TO MOST
OF SOUTHWESTERN KANSAS THIS AFTERNOON. THERE WAS A BAND OF RAIN,
SOME MODERATE, THAT MOVED NORTH FROM FROM OKLAHOMA MORNING LAID
DOWN 0.02 TO 0.50 INCH OF RAIN ACROSS MUCH OF OUR SOUTHERN CWA.
THIS SOAKED UPPER LAYER OF SURFACE GROUND WILL DELAY TO ONSET OF
ACCUMULATING SNOW, BUT SNOW RATES OF .5 TO 1.0-INCH PER HOUR AT
TIMES WILL LEAD TO A QUICK ACCUMULATION. FURTHERMORE, PER THE
FORECAST SOUNDINGS FROM THE NAM AND RUC MODELS BOTH SHOWED A WARM
ELEVATED LAYER OF +2 DEGREES, INDICATING THERE MAY BE SOME SLEET
OR LIGHT FREEZING RAIN BEFORE THE EASTERN PART OF THE CWA CHANGES
TO ALL SNOW, SO WILL MENTION THAT. A SURFACE COLD FRONT WAS
WORKING SOUTH THROUGH THE CWA TODAY, AND CLEARED THE SOUTHEAST
PART OF OUR FORECAST AREA BETWEEN 20 AND 21Z. WHERE THE
OVERRIDING COLD AIR WILL MEET THE BEST LIFT OVER THE ELEVATED
FRONT IS WHERE A HEAVY BAND OF SNOW SHOULD SET UP...FROM
APPROXIMATELY LAKIN TO GARDEN CITY TO NESS CITY...WHERE 10 TO 11
INCHES OF SNOW IS POSSIBLE BY TUESDAY AFTERNOON. SOUTHEAST OF THAT
ZONE, IN THE LIBERAL TO DODGE CITY TO KINSLEY TO SAINT JOHN ZONE...I
STILL THINK THERE COULD BE SOME BANDS OF HEAVY SNOW TONIGHT...WITH
LESS DURATION THAN NORTH OF THERE, AND 5 TO 8 INCHES OF SNOW IS
EXPECTED THERE BY TUESDAY AFTERNOON. IN BOTH THESE ZONES...STRONG
NORTH WINDS OF 20 TO 35 MPH WITH GUSTS TO NEAR 45 MPH WILL COMBINE
WITH THE SNOW TO CREATE LOW VISIBILITIES IN BLOWING AND DRIFTING
SNOW. WITH A FEW AREAS IN OUR EXTREME WEST SUCH AS TRB AND 3K3
ALREADY REPORTING M1/4SM +SN...THINK THIS COLD AIR AND STRONG
WINDS WILL WRAP TO THE EAST TONIGHT. THEREFORE, THE BLIZZARD
WARNING WILL CONTINUE THROUGH NOON TUESDAY, NORTHWEST OF A LINE
FROM COLDWATER TO PRATT. A WINTER WEATHER ADVISORY FOR 3 TO 5
INCHES OF SNOW AND BLOWING SNOW WILL ALSO CONTINUE THROUGH NOON
TUESDAY FOR PRATT, BARBER AND COMANCHE COUNTIES.
AS FOR TEMPS, THINK OVERNIGHT THAT LOWER DEW POINTS WILL BE
FILTERING IN FROM THE NORTH ON THE STRONG FLOW. STAYED PRETTY
CLOSE TO THE PREVIOUS FORECAST OF MIN T`S FROM AROUND 17F IN EHA
TO 23F IN P28. TOMORROW WILL SEE THICK CLOUDS AROUND ALONG WITH
EARLY SNOW. THE TEMPERATURE WILL NOT RISE MUCH AND SHOULD TOP OUT
IN THE 27F TO 30F DEGREE RANGE. CLOUDS WILL CLEAR OUT FROM WEST TO
EAST TUESDAY EVENING, AND WITH FRESH SNOW COVER EXPECTED AND LIGHT
WEST WINDS, THE TEMPERATURE SHOULD PLUMMET. LOWS TUESDAY NIGHT
WILL BE QUITE COLD, RANGING FROM A VERY COLD 5F IN EHA TO 14F IN
P28. WEDNESDAY, WE WILL STILL BE IN THE GRIP OF COLD ARCTIC AIR
CENTERED TO OUR NORTHEAST, BUT NOT MUCH WARMER THAN TUESDAY IN
MOST SPOTS. HAVE WENT WITH A MAX T FORECAST FOR WEDNESDAY IN THE
27F DEGREE RANGE NEAR LBL, EHA, GCK AND DDC, RANGING UP TO 33F AT P28.
DAYS 3-7...
A NORTHERN BRANCH SHORTWAVE TROUGH WILL DIG TO NEAR THE FOUR CORNERS
ON THURSDAY WITH SOME LIGHT SNOW EXPECTED MOSTLY IN THE AFTERNOON
ACROSS WESTERN KANSAS. THE TROUGH THEN WILL MOVE INTO THE PLAINS ON
FRIDAY WITH LIGHT SNOW ENDING FROM WEST TO EAST ON FRIDAY MORNING.
EXPECT LESS THAN AN INCH ACCUMULATION. ANOTHER LONGER WAVE TROUGH
WILL MOVE ACROSS THE CENTRAL CONUS ON SUNDAY WITH MAINLY DRY
CONDITIONS AND LESS MOISTURE TO WORK WITH. THE GFS AND NEW ECMWF ARE
DIFFERENT WITH ONE SHOWING A SHORTWAVE RIDGE AND THE OTHER A
SHORTWAVE TROUGH BUT LOOKS TO DRY FOR ANY PRECIPITATION.
A COLD FRONT WILL MOVE INTO THE CENTRAL PLAINS WITH HIGH PRESSURE
AND LOWS IN THE TEENS TO LOW 20S ON THURSDAY MORNING AND HIGHS FROM
THE UPPER 20S NORTH TO AROUND 34 SOUTHEAST FA ON THURSDAY. A RIDGE
OF COLD HIGH PRESSURE MOVES INTO THE PLAINS ON FRIDAY WITH LOWS IN
THE TEENS AND HIGHS ONLY IN THE MID 20S. SATURDAY MORNING LOOKS THE
COLDEST WITH LIGHT WINDS AND LOWS IN THE SINGLE DIGITS. FOR SATURDAY
HIGHS SHOULD BE AROUND 30 TO 35. ON CHRISTMAS DAY SUNDAY MORNING
LOWS WILL BE MAINLY IN THE TEENS AND HIGHS AROUND 30 TO 35 WITH
MOSTLY CLEAR SKIES. ON MONDAY MORNING LOWS WILL BE COLD AGAIN WITH
CLEAR SKIES AROUND 10 TO 15 DEGREES AND HIGHS MONDAY WITH WARMING
SOUTHWEST WINDS AND HIGHS FROM THE MID 30S TO LOWER 40S.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 20 27 9 27 / 100 80 0 0
GCK 19 28 6 27 / 100 70 0 0
EHA 17 28 5 27 / 100 60 0 0
LBL 20 28 6 27 / 100 60 0 0
HYS 23 29 6 28 / 100 100 0 0
P28 26 30 14 36 / 100 90 10 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WARNING UNTIL NOON CST /11 AM MST/ TUESDAY FOR KSZ030-
031-043>046-061>066-074>080-084>088.
WINTER WEATHER ADVISORY UNTIL NOON CST TUESDAY FOR KSZ081-089-
090.
&&
$$
FN99/99/25
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
411 AM EST TUE DEC 20 2011
.DISCUSSION /TODAY THROUGH MONDAY/...
UPPER TROUGH EXITING THE AREA THIS MORNING...PLACING THE AREA UNDER
MORE ZONAL FLOW THROUGH TONIGHT. AT THE SFC...LOW MOVING THROUGH
HUDSON BAY TODAY WILL PUSH A COLD FRONT THROUGH SRN CANADA.
INCREASING GRADIENT AHEAD OF THE FRONT WILL INCREASE WSW WINDS OVER
THE CWA...ESPECIALLY OVER WRN LK SUPERIOR. H925 WINDS /JUST BELOW
THE INVERSION/ SHOULD INCREASE TO 35-40KTS OVER WRN LK SUPERIOR AND
25-30KTS OVER MUCH OF THE CWA. WITH EXPECTED MIXING TOWARDS THAT
LEVEL THIS AFTN WITH MORE SUN...WILL BE BREEZY AT TIMES THIS AFTN
WITH GUSTS TO 25-30MPH...ESPECIALLY NEAR LK SUPERIOR.
PESKY LOW CLOUDS WILL BE THE SHORT TERM FCST CONCERN...AS MODELS
CONTINUE TO STRUGGLE EVEN ACKNOWLEDGING CLOUDS BEING PRESENT. THE
INCREASING H925 WINDS SHOULD HELP PUSH THE LOW CLOUDS NE AND ALSO
AID IN MIXING INTO DRIER AIR ALOFT AND FROM THE WSW. DOWNSLOPING SW
WINDS ALREADY STARTING TO BREAK UP CLOUDS OVER NCNTRL UPPER MI AND
EXPECT THAT TO CONTINUE INTO THE MORNING. RUC STILL LOOKS TO HAVE
THE BEST HANDLE ON THE CLOUDS...AND 06Z RUNS HAVE IT DIMINISHING BY
MID DAY. LLVL WINDS OFF COOLER LK MI WILL LIKELY KEEP CLOUDS HANGING
ON LONGER OVER THE E. IN ADDITION...WITH H850 TEMPS AROUND -9C
CREATING DELTA-T VALUES OF 16 OVER LK MI WILL KEEP LK ENHANCED
CLOUDS OVER FAR SE LUCE/SCHOOLCRAFT COUNTIES THROUGH MUCH OF THE
DAY.
ONCE THE CLOUDS EXIT THE AREA...SHOULD BE A NICE LATE DECEMBER AFTN
WITH PARTLY/MOSTLY SUNNY SKIES /ALTHOUGH A FEW MID CLOUDS COULD PUSH
SE OVER NRN LK SUPERIOR AND AFFECT THE KEWEENAW/ AND HIGHS IN THE
UPPER 20S AND LOWER 30S.
UPPER LOW ASSOCIATED WITH STRONG WINTER STORM IN THE LEE OF THE
CNTRL/SRN ROCKIES WILL SHIFT NE TONIGHT AND MOVE THROUGH THE LOWER
GREAT LAKES ON WED INTO WED NIGHT. WITH THIS SYSTEM PUSHING NE AND
SFC FRONT SLOWLY DROPPING SE THROUGH CANADA AND TOWARDS THE U.S.
BORDER...EXPECT A PORTION OF THE AREA TO BE UNDER THE PINCHED DRY
AIR BETWEEN THE SYSTEMS. LATEST TRENDS IN THE MODELS PUT THIS MORE
OVER THE SE CWA TONIGHT...WHILE THE NW HALF IS UNDER THE INCREASING
CLOUDS WITH THE APPROACHING SFC TROUGH. EXPECT THE CLOUDS TO
CONTINUE SE SLOWLY DURING THE DAY ON WED AS THE SFC TROUGH CONTINUES
IT/S SE PUSH.
PCPN CHANCES INCREASE AS THE SFC TROUGH PUSHES THROUGH LATE WED
NIGHT AND CHANCES WILL CONTINUE ON THURS AS LES DEVELOPS. H850 TEMPS
SHOULD FALL FROM -7C AT 06Z THURS TO -13C AT 18Z AND PUSH DELTA-T
VALUES TOWARDS 17. AS THE COLDER AIR ARRIVES...DEEPER MOISTURE EXITS
AND H850-700 SUBSIDENCE INCREASES /ESPECIALLY IN THE AFTN/...WHICH
CAUSES INVERSION HEIGHTS TO FALL TOWARDS 3-4KFT. THUS...POTENTIAL
FOR MUCH MORE THAT A INCH OR TWO OF LES IS LIMITED ON THURS. DID
BUMP POPS UP SOME FOR THURS FOR THE NNW WIND LOCATIONS...BUT STILL
ONLY PEAKED IT OUT IN THE MID-UPPER CHANCE AREA. ALSO BUMPED UP POPS
SOME FOR THURS NIGHT...TO CHANCES OVER THE E...SINCE LES WILL LIKELY
BE ONGOING AND BEST MOISTURE LOOKS TO BE THERE. WRN CWA IS A LITTLE
MORE UNCERTAIN WITH SFC RIDGE AND DRYING ARRIVING THROUGH THE NIGHT.
WILL GO WITH SLIGHTS FOR MOST OF THE N WIND FAVORED
LOCATIONS...THOUGH WILL GO WITH SOME CHANCES IN THE EVENING OVER THE
HIGHER TERRAIN LOCATIONS.
UPPER TROUGH IN THE NRN STREAM WILL DROP SE OUT OF THE CANADIAN
ROCKIES ON WED AND THROUGH THE UPPER GREAT LAKES THURS THROUGH FRI.
STILL SOME DIFFERENCES IN THE MODELS ON POTENTIALLY CLOSING OFF THE
SRN EXTENT OF THE UPPER TROUGH OVER THE CNTRL PLAINS FRI...WHICH
WOULD ALLOW WEAK UPPER RIDGING TO MOVE INTO THE WRN GREAT LKS
EARLIER ON FRI NIGHT AND CONTINUE INTO SAT. EITHER WAY...CWA WILL
LIKELY BE BETWEEN SYSTEMS AND HAVE SFC HIGH OVER THE AREA FRI NIGHT
INTO SAT.
EXPECT LINGERING LES TO DIMINISH AND PUSH OFFSHORE OVER THE ERN CWA
ON FRI...AS H850 WAA PUSHES TEMPS TOWARDS -8C AND LLVL WINDS BACK TO
THE WSW. AT THE SAME TIME SHORTWAVE MOVING THROUGH THE NRN STREAM IN
CNTRL/NRN ONTARIO SHOULD ONLY BRUSH HIGH CLOUDS OVER NRN LK
SUPERIOR...ALTHOUGH 00Z GFS/GEM HAS TRENDED FARTHER S WITH WITH WAVE
AND BRUSHES PCPN OVER NRN LK SUPERIOR. SWRLY FLOW AND DRY AIR ALOFT
SHOULD KEEP TEMPS IN CHECK WITH CLEAR SKIES ON FRI NIGHT AND WILL GO
WITH ABOVE NORMAL LOWS. DRY AIR ABOVE THE STRONG INVERSION AROUND
H925 SHOULD KEEP SKIES MOSTLY SUNNY ON SAT OTHER THAN SOME PASSING
HIGH CLOUDS. TEMPS ARE UNCERTAIN THIS FAR OUT AND WILL LEAN TOWARDS
A CONSENSUS FOR HIGHS. THAT BEING SAID...CLEAR SKIES AND SW WINDS
FAVOR WARMER TEMPS IN DOWNSLOPE AREAS NEAR LK SUPERIOR...SO DID
ADJUST THOSE AREAS UP A FEW DEGREES.
NRN STREAM TROUGH IS STILL SHOWN ON THE EXTENDED MODELS TO AFFECT
THE AREA SUN INTO MON. SFC TROUGH ASSOCIATED WITH LOW MOVING THROUGH
HUDSON BAY SHOULD DRAG A SFC TROUGH ACROSS THE CWA SAT NIGHT OR SUN
/12Z ECMWF AND 00Z GEM ARE THE FASTER SOLNS/. AS HAS BEEN THE CASE
WITH THE SERIES OF NRN STREAM WAVES...MOISTURE/FORCING ALONG THE
FRONT APPEARS TO BE LIMITED SO WILL CONTINUE SLIGHTS/LOW CHANCES
WITH THE FRONTAL PASSAGE. H850 TEMPS AROUND -15C AND POST FRONTAL
LLVL MOISTURE SHOULD LEAD TO LES IN NW WIND FAVORED LOCATIONS SUN
AND BUMPED UP POPS FROM THE CONSENSUS AND WILL CONTINUE CHANCE POPS
THROUGH SUN NIGHT. 00Z GFS SOUNDINGS WOULD SUPPORT A CHANCE OF
SEEING AT LEAST FEW INCHES OF SNOW ACCUMULATIONS NNW SNOWBELTS FOR
XMAS AFTN/EVENING. ECMWF ON THE OTHERHAND QUICKLY PULLS DRIER AIR
INTO THE REGION SUN AFTN/NIGHT WITH THE ARRIVAL OF THE SFC RIDGE.
ANOTHER NRN STREAM SHORTWAVE WAVE LOOKS TO BRUSH LK SUPERIOR ON
MN...BUT WITH OVERALL WEAK WAVE AND LIMITED MOISTURE WILL ONLY GO
SLIGHT POPS.
&&
.AVIATION /FOR THE 06Z TAF ISSUANCE/...
MVFR CIGS HAVE PERSISTED SIGNIFICANTLY LONGER THAN GUIDANCE OR WHAT
NAM/GFS LOW LEVEL RH PROGS WOULD SUGGEST. HOWEVER...EXPECT SKIES TO
FINALLY CLEAR EARLY TODAY AS THE HIGH PRES RIDGE AXIS DROPS SE
THRU THE AREA AND WINDS SHIFT TO THE SOUTHWEST AND BRINGS DRIER AIR
TOWARD THE AREA FROM THE UPPER MS VALLEY...PER RUC PROGS. SW
GRADIENT WINDS WILL INCREASE TODAY WITH GUSTS AROUND 25 KT BY LATE
MORNING/EARLY AFTERNOON.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
DEEP LOW PRES MOVING E TO HUDSON BAY WILL BRING ANOTHER ROUND OF SW
GALES TO MUCH OF LAKE SUPERIOR TODAY THRU THIS EVENING. SW WIND
DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND ISLE ROYALE FOR
STRONGEST WINDS (GUSTS TO 40-45KT). GALES WILL END LATER TONIGHT
AS PRES GRADIENT WEAKENS. WINDS WILL BE BLO 25KT WED THRU FRI THOUGH
THERE MAY BE A PERIOD OF 20-30KT WINDS OVER CNTRL LAKE SUPERIOR THU
MORNING IN THE WAKE OF A PASSING COLD FRONT. ANOTHER LOW PRES SYSTEM
TRACKING E TO HUDSON BAY COULD BRING A PERIOD OF SW WINDS UP TO 30KT
OVER PORTIONS OF WEST AND NCNTRL LAKE SUPERIOR LATE FRI NIGHT INTO
SAT.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
GALE WARNING FROM 1 PM THIS AFTERNOON TO 1 AM EST WEDNESDAY FOR
LSZ267.
GALE WARNING FROM 9 AM THIS MORNING TO 1 AM EST WEDNESDAY FOR
LSZ266.
GALE WARNING UNTIL MIDNIGHT EST /11 PM CST/ TONIGHT FOR LSZ162.
GALE WARNING UNTIL 3 AM EST WEDNESDAY FOR LSZ263-264.
LAKE MICHIGAN...
NONE.
&&
$$
DISCUSSION...SRF
AVIATION...JLB
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1214 AM EST TUE DEC 20 2011
UPDATED FOR 06Z AVIATION DISCUSSION
.SHORT TERM /TONIGHT AND TUESDAY/... ISSUED AT 337 PM EST
HIGH PRESSURE RIDGE SLIDING OVER THE AREA TONIGHT SHOULD BRING AN
END TO THE LES/FLURRIES OVER THE E THIS EVENING. GIVEN WIDESPREAD
STRATOCU DECK IN PLACE ACROSS NRN MN...WI AND ONTARIO...CLOUDS MAY
PERSIST A BIT LONGER INTO AT LEAST THE EARLY EVENING
HRS...ESPECIALLY OVER ERN COUNTIES...WITH A NW FLOW. STILL EXPECT
DECREASING CLOUDS BY LATE EVENING WITH ARRIVAL OF SFC RDG AXIS AND
ASSOC SUBSIDENCE. WITH THE DECREASING CLOUDS AND WINDS...SHOULD BE A
COLD NIGHT OVER THE INTERIOR LOCATIONS. PWATS AROUND 35 PERCENT OF
NORMAL WILL HELP ENHANCE RADIATIONAL COOLING SO WENT ON THE LOWER
END OF MODEL MOS GUIDANCE WITH LOWS IN THE MID SINGLE DIGITS ABOVE
ZERO OVER THE INTERIOR W/CNTRL. WINDS WILL INCREASE SOME OVER THE
FAR W LATE IN THE NIGHT AHEAD OF THE NEXT WAVE...WHICH COULD LEAD TO
A RISE IN TEMPS LATE THERE.
NRN STREAM SHORTWAVE AND ASSOCIATED LOW WILL BE MOVING THROUGH FAR
NRN ONTARIO/HUDSON BAY REGION ON TUESDAY. THIS WILL RESULT IN DRY
CONDITIONS ACROSS UPR MI ON TUESDAY BUT FALLING PRES NORTH OF LAKE
SUPERIOR SHOULD ALLOW WSW TO PICK UP AND BCM GUSTY ESPECIALLY ACROSS
THE NRN TIER OF THE FCST AREA. SHOULD BE ANOTHER ABOVE NORMAL TEMP
DAY (UPPER 20S AND LOWER 30S) UNDER A MOSTLY SUNNY SKY.
.LONG TERM /00Z WED THROUGH NEXT SUN/...
MODELS HAVE CONTINUED THE FASTER TREND WITH MERGING THE SRN STREAM
UPPER LOW CURRENTLY OVER THE SWRN CONUS WITH THE NRN STREAM ON WED
OVER THE LOWER GREAT LAKES. WITH THE APPROACHING NRN STREAM WAVE
OVER MANITOBA/SASK...AREA SHOULD BE UNDER THE INFLUENCE OF A WEAK
SFC TROUGH DROPPING S FROM ONTARIO. MOSTLY CLEAR SKIES AT 00Z WED
WILL GIVE WAY TO CLOUDS MOVING IN FROM THE NW THROUGH WED. WITH
MODELS MOVING THE SFC TROUGH AND LOW LEVEL MOISTURE IN FAST...HAVE
INCREASED HOW FAST THE CLOUDS MOVE IN. MOISTURE/FORCING IS WEAK WITH
THE PASSAGE OF THE TROUGH...SO WILL CONTINUE SLIGHT CHANCE POPS OVER
WRN LK SUPERIOR IN THE AFTN AND SLIGHT/LOW CHANCE POPS ALONG THE
FRONT WED NIGHT.
UPPER TROUGH THEN SWEEPS ACROSS THE AREA LATE WED NIGHT INTO
FRI...BRINGING A BETTER CHANCE FOR SNOW BEHIND THE FRONT. 850MB
TEMPS LOOK TO FALL TO AROUND -12C BY 18Z THU...WHICH WOULD CREATE
LARGE ENOUGH DELTA-T VALUES FOR LES. 800-650MB SUBSIDENCE AND DRY
AIR WILL LIMIT THE INVERSION HEIGHTS TO 4KFT. SHOULD BE DECENT LLVL
MOISTURE TO WORK WITH BELOW THE INVERSION...SO CONTINUED WITH CHANCE
POPS. WITH THE FORCING BELOW THE DGZ /CLOUD TOPS ONLY REACH -15C/
EXPECT SNOW RATIOS TO BE IN THE LOW TEENS AND WILL LIKELY ONLY SEE A
LIGHT DUSTING FOR AREAS FAVORED BY A NNW WIND.
UPPER TROUGH STARTS TO SHIFT E ON FRI AS SFC HIGH PUSHES OVER THE
AREA. DRIER AIR ASSOCIATED WITH THE HIGH WILL LEAD TO DIMINISHING
LES POPS THURS NIGHT WEST AND DURING THE DAY FRI EAST...AS WINDS
BECOME ANTICYCLONIC. MAY SEE WEAK UPPER RIDGING ON SAT /AS SHOWN BY
THE 12Z/19 GFS/...HOWEVER...THERE IS A GOOD DEAL OF UNCERTAINTY AS
THE 00Z/19 ECMWF SHOWS A SHARP UPPER TROUGH OVER THE CWA AT THE SAME
TIME. THE NEXT NRN STREAM TROUGH TO AFFECT THE AREA WILL MOVE IN ON
SAT NIGHT INTO SUN. FORCING/MOISTURE LOOK TO BE LIMITED ALONG THE
FRONT AND THE BEST POTENTIAL FOR PCPN WILL COME ON SUN WITH LES...AS
H850 TEMPS FALL TOWARDS -13C.
BROAD UPPER RIDGING LOOKS TO MOVE OVER THE WRN HALF OF THE CONUS ON
MONDAY AS THE UPPER TROUGH MOVES EAST OF THE CWA...PUTTING THE CWA
UNDER GENERAL NW FLOW ALOFT. THERE IS A SIGNIFICANT AMOUNT OF
UNCERTAINTY FOR SUNDAY NIGHT INTO MONDAY...WITH MODELS HAVING BAD
RUN TO RUN CONTINUITY AND MODEL DISAGREEMENT. OVERALL...EXPECT
DIMINISHING LES AS 850MB TEMPS WARM AND FLOW GENERALLY BECOMES MORE
ANTICYCLONIC.
&&
.AVIATION /FOR THE 06Z TAF ISSUANCE/...
MVFR CIGS HAVE PERSISTED SIGNIFICANTLY LONGER THAN GUIDANCE OR WHAT
NAM/GFS LOW LEVEL RH PROGS WOULD SUGGEST. HOWEVER...EXPECT SKIES TO
FINALLY CLEAR EARLY TODAY AS THE HIGH PRES RIDGE AXIS DROPS SE
THRU THE AREA AND WINDS SHIFT TO THE SOUTHWEST AND BRINGS DRIER AIR
TOWARD THE AREA FROM THE UPPER MS VALLEY...PER RUC PROGS. SW
GRADIENT WINDS WILL INCREASE TODAY WITH GUSTS AROUND 25 KT BY LATE
MORNING/EARLY AFTERNOON.
&&
.MARINE /FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE/...
WINDS WILL DIMINISH BLO 25 KT TONIGHT AS HIGH PRES QUICKLY PASSES
ACROSS THE GREAT LAKES. DEEP LOW PRES MOVING E TO HUDSON BAY EARLY
TUE WILL LIKELY BRING ANOTHER ROUND OF SW GALES TO PORTIONS OF LAKE
SUPERIOR...MAINLY THE W HALF. SW WIND DIRECTION WILL FAVOR THE AREA
BTWN THE KEWEENAW AND ISLE ROYALE FOR STRONGEST WINDS TUE (GUSTS TO
AROUND 40KT). GALES WILL END TUE NIGHT AS PRES GRADIENT WEAKENS.
WINDS WILL BE BLO 25KT WED THRU FRI. ANOTHER LOW PRES SYSTEM
TRACKING ACROSS HUDSON BAY COULD BRING A PERIOD OF SW WINDS TO 30 KT
OVER WEST AND NORTH CENTRAL LAKE SUPERIOR FRI NIGHT INTO SATURDAY.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...
GALE WARNING FROM 9 AM TUESDAY TO 1 AM EST WEDNESDAY FOR LSZ266.
GALE WARNING FROM 7 AM EST /6 AM CST/ TUESDAY TO MIDNIGHT EST
/11 PM CST/ TUESDAY NIGHT FOR LSZ162.
GALE WARNING FROM 7 AM TUESDAY TO 3 AM EST WEDNESDAY FOR LSZ263-
264.
LAKE MICHIGAN...NONE.
&&
$$
SHORT TERM...VOSS
LONG TERM...TITUS
AVIATION...JLB
MARINE...VOSS
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
346 AM CST Tue Dec 20 2011
.DISCUSSION...
In the short term a classic panhandle low continues to accomplish
what it often does for this portion of the region, that is, sending
copious amount of moisture northward and creating a headache for
winter precipitation forecasts.
Early this morning, expansive dry slot is now rapidly lifting
northeast and across eastern Kansas and western Missouri. With
satellite imagery indicating the loss of ice crystals we`re also slowly
losing much of our precipitation across the region. However, during
the past 18 hours extensive northward moisture transport resulting in
PWAT values nearly 1" (or within the 99th percentile for this time of
the year) and efficient rain processes have produced near record
rainfall in the local area. The result of nearly 1-1.5" of rain will
be the flooding of several rivers in central Missouri. Further north,
a more problematic forecast persists as a tight moisture gradient has
formed over extreme northern Missouri thanks to Canadian high
pressure over the Dakotas and strong dry air advection behind a
departing northern stream trough in the Western Great Lakes. 00z
OAX/DVN soundings confirmed the extent of this moisture disparity,
which is resulting in a overall lack of precipitation reaching the
ground despite the extensive areal coverage of radar echoes. Thus,
snowfall totals have been severely hampered over NE Kansas and NW
Missouri with isolated totals of a half inch in some locations.
For today, following much of the guidance from the suite of
mesoscale models which have a reasonable handle on the current
situation. The 00z NMM, 06z NAM, and RUC are the most reasonable
solutions at this time. As dry slot rotates through the area, precip
will continue to diminish through 15z, with lingering activity
mainly in the northern zones. Soundings continue to support a mix of
snow/sleet and perhaps rain in and along the Highway 36 corridor.
Given the absence of ice crystals would also be concerned for a bit
of freezing drizzle. By the middle to late morning hours, we should
also begin to see the expansive deformation zone in southwestern
Kansas begin to lift northeast towards the area. However, as the
upper low begins to eject eastward, support for heavy precipitation
will diminish as in tandem the favorable upper jet streak and rich
moisture feed both shift eastward. Feel model qpf may be a bit too
high given the lack of ice aloft, but soundings similar to these have
produced periods of light rain/drizzle/sleet or even snow showers
before, just usually very light in nature. The best chance for any
wintry precip will remain in the northwestern third of the CWA with
little accumulation. Further south would expect more drizzle or light
rain showers than anything. Will continue with the advisory for now
given potential for some development, but feel impacts may be much
lower than earlier thought.
Tonight, as mentioned in previous discussion, models continue to
hint at an area of low static stability most likely tied to an
individual vort lobe rotating around the upper low. Mesoscale model
output remains consistent in bringing a pocket of strong omega,
non-coincident with the aforementioned deformation zone, through
southern Kansas and into portions of central Missouri. Soundings and
cross sections through this layer suggest that with rather high
freezing levels, would expect mainly a patch of light to moderate
rain showers. Would also not be surprised to see a rumble or two of
thunder, but confidence not high enough to include. It is
theoretically possible that there could be enough dynamical cooling
within this locally intensifying vort lobe to produce a very quick
batch of heavy snow. Once again, not a certain forecast at all. Of
more concern is the potential that if roads and paved surfaces cannot
dry out by nighttime as colder air arrives, a period of black ice may
be possible heading into Wednesday morning.
Wednesday: The region will quickly transition to a zonal or
southwest flow pattern aloft for Wednesday as energy again digs into
the southwestern United States. Given the lack of snowcover except
in the NW CWA and modest southwest low level flow have bumped up
high temperatures a category or two in most locations.
For Thursday: Secondary upper trough emanating out of the Southwest
will quickly race into the region on Thursday. The southerly track
of this wave will hold moisture well south of the CWA with a weak
surface ridge axis bisecting the area.
31
Thursday through Tuesday...
Models have been trending toward a slightly stronger system for
Thursday night and Friday. However, there is still some difficulty
with respect to interactions between the Northern Plains shortwave
trough. Regardless, since moisture is limited will keep the threat
of snow in the low chance category. Otherwise, for the rest of the
period, it will remain rather quiet with only weak shortwaves in
basically dry northwest upper flow.
DB
&&
.AVIATION...
Initial wave of precipitation has shifted east of the terminals this
evening. Secondary, more scattered precip now beginning to shift
northward and should affect the terminals over the next several
hours. The anticipated dry slot now moving into southern Kansas and
will continue to progress northward, reaching the taf site during the
overnight hours. Prior to this, periodic rain and drizzle along with
IFR ceilings (perhaps occasionally LIFR within the heavier rain bands)
will overspread the Kansas City terminals. More uncertainty at KSTJ
where the temperature profile is hovering near the freezing mark.
Expect a rain and periodic snow mix within the heavier precipitation
areas to move across the taf site. Aforementioned dry slot should
overspread the terminals by ~09z, depleting any ice crystal growth
from the mid levels of the column. This is expected to result in a
transition to drizzle and freezing drizzle (depending on the surface
temperature at the respective terminals) through the afternoon hours.
There is a chance for a quick burst of light snow by the evening
hours tomorrow along the backside of the upper low. However,
confidence on the location and temperature profile precludes a
mention at this time.
Deroche
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER WEATHER ADVISORY until 6 PM CST this evening FOR
MOZ001>005-011>014-020>022.
KS...WINTER WEATHER ADVISORY until 6 PM CST this evening FOR KSZ025-
102.
&&
$$
WFO EAX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NWS ST LOUIS MO
1107 PM CST MON DEC 19 2011
.UPDATE...
/935 PM CST MON DEC 19 2011/
MADE SOME MINOR TWEEKS TO THE FORECAST FOR TONIGHT AND EARLY TUESDAY
MORNING...NAMELY TO TRIM BACK THE MENTION OF WINTRY PRECIPITATION
ACROSS NORTHERN PORTIONS OF THE CWA. THE LATEST UPPER AIR DATA AND
SURFACE OBS SHOW DEEPER COLD AIR TO SUPPORT A POTENTIAL WINTRY MIX
IS BETTER JUXTAPOSED WEST OF THE CWA. THE LATEST MODEL GUIDANCE
INCLUDING THE RUC AND HRRR SUPPORT THIS AS WELL WITH GREATER CAA
WEST OF THE CWA. IN FACT A MULTITUDE OF SOUNDINGS SHOW VERY LOW
POTENTIAL FOR ANY SNOW OR SLEET THRU 12Z. AS A RESULT I HAVE
TRIMMED BACK THE MENTION OF RAIN...SLEET...SNOW TO KNOX AND LEWIS
COUNTIES FOR LATE TONIGHT...AFTER 09Z. AFTER THIS TIME I CAN`T
RULE OUT THE POSSIBILITY BUT EVEN IN THESE FEW COUNTIES IT MAY BE
TOO WARM.
GLASS
&&
.DISCUSSION...
/358 PM CST MON DEC 19 2011/
PRIMARY CONCERN WITH THIS FCST PCKG IS PRECIP CHANCES AND PTYPE FOR
THE NEXT 7 DAYS.
ISENTROPIC ASCENT AHEAD OF A LOW PRESSURE SYSTEM LIFTING NEWD INTO
THE SRN PLAINS WAS PRODUCING A BROAD PCPN SHIELD THIS AFTN THAT
STRETCHED ACROSS MOST OF KS AND MO AND INTO THE SRN HALF OF IL.
AMPLE MOISTURE WILL BE AVAILABLE FOR PCPN WITH MODELS SHOWING A
STRONG LLJ TRANSPORTING A VERY MOIST AIR MASS /PWAT VALUES OF
AROUND 1 INCH WHICH IS 2 STANDARD DEVIATIONS ABOVE NORMAL FOR
DECEMBER IN THIS PART OF THE COUNTRY/ NWD INTO THE REGION. PCPN
SHOULD CONTINUE OVERNIGHT AND INCREASE IN COVERAGE AS THE UPPER
LOW APPROACHES AND LARGE SCALE LIFT INCREASES WITH SOME ADDITIONAL
ENHANCEMENT PROVIDED BY WEAK JET COUPLING. TEMPERATURE PROFILES
CONTINUE TO SUPPORT AN ALL-RAIN EVENT ACROSS ALL BUT THE FAR NRN
CWA WHERE A COLD FRONT WAS EDGING SWD OUT OF IA. THE FAR NRN CWA
WILL BE VERY CLOSE TO THE TRANSITION ZONE BETWEEN RAIN AND SNOW
AND BUFKIT PROFILES AS WELL AS PARTIAL THICKNESS METHODS SUGGEST
THAT SNOW AND SLEET MAY MIX WITH THE RAIN AT TIMES. AS THE SFC LOW
LIFTS OUT OF THE TX PANHANDLE TONIGHT AND TOMORROW...THE BOUNDARY
WILL BE LIFTED NWD AS A WARM FRONT AND PCPN SHOULD CHANGE BACK TO
RAIN. DRY SLOT EFFECTS MAY CAUSE PCPN TO FALL MORE AS DRIZZLE THAN
AS RAIN FOR THE SRN HALF OF THE CWA TOMORROW AND TOMORROW NIGHT.
FINALLY...COLD AIR WRAPPING AROUND THE BACK SIDE OF THE DEPARTING
SYSTEM MAY CAUSE SNOW TO MIX WITH RAIN ACROSS NWRN PARTS OF THE
CWA TOMORROW NIGHT. ATTM IT APPEARS THAT THE DEFORMATION ZONE WILL
REMAIN NORTH AND WEST OF THE CWA. BARRING ANY UNEXPECTED SHIFTS IN
THE TRACK OF THIS SYSTEM...LESS THAN A HALF INCH OF SNOW AND SLEET
ACCUMULATION IS EXPECTED ACROSS THE FAR NRN CWA.
MEANWHILE...WATER VAPOR IMAGERY SHOWED ANOTHER SHORTWAVE DROPPING
SWD ALONG THE CA COAST TOWARDS BAJA CALIFORNIA. MODELS ARE IN GOOD
AGREEMENT THAT THIS SYSTEM CLOSES OFF AND SLOWS DOWN BEFORE MOVING
THROUGH NRN MEXICO AND FINALLY LIFTING THROUGH ERN TX ON WED/THU IN
RESPONSE TO THE STRONGER SHORTWAVE REACHING THE WA/OR COAST ON TUE
NIGHT. THE SHORTWAVE CURRENTLY ALONG THE CA COAST IS NOT EXPECTED TO
PRODUCE ANY PCPN FOR OUR AREA AS IT LIFTS THROUGH THE SRN CONUS.
HOWEVER...MODELS SHOW THAT THE OTHER SYSTEM DEEPENS AFTER CROSSING
THE ROCKIES AND TAKES A TRACK THAT WOULD BE FAVORABLE FOR SNOWFALL
ACROSS MOST OF THE CWA. THERE ARE STILL SIGNIFICANT DIFFERENCES
BETWEEN THE GFS/ECMWF/GEM /ESPECIALLY WRT PHASING WITH NRN STREAM
SHORTWAVES/ AND BETTER MODEL AGREEMENT MIGHT NOT OCCUR UNTIL AFTER
THESE FEATURES HAVE BEEN SAMPLED BY THE UPPER AIR NETWORK.
KANOFSKY
&&
.AVIATION...
/1104 PM CST MON DEC 19 2011/
NOT MUCH CHANGED FOR THIS TAF SET. CURRENT CONDITIONS ARE EXPECTED
TO IMPROVE TUES AFTERNOON FOR A SHORT PERIOD BEFORE DROPPING BACK
INTO IFR RANGE. LATEST GUIDANCE CONTINUES TO SUGGEST PRECIP WILL
FALL AS RA THRU THE TAF PERIOD. HOWEVER...TEMPS ARE EXPECTED TO
DROP TO NEAR FREEZING AT UIN.
SPECIFICS FOR KSTL...NOT MUCH CHANGED FOR THIS TAF SET. CURRENT
CONDITIONS ARE EXPECTED TO IMPROVE TUES AFTERNOON FOR A SHORT
PERIOD BEFORE DROPPING BACK INTO IFR RANGE. LATEST GUIDANCE
CONTINUES TO SUGGEST PRECIP WILL FALL AS RA THRU THE TAF PERIOD.
TILLY
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
IL...NONE.
&&
$$
WFO LSX
AREA FORECAST DISCUSSION
NWS HASTINGS NE
1052 PM CST MON DEC 19 2011
.AVIATION...06Z KGRI. A MID-LEVEL DECK OF CLOUDS SHOULD HANG
AROUND FOR MOST OF THE FORECAST AND THEN GIVE WAY TO HIGHER LEVEL
CLOUDINESS BY TUESDAY AFTERNOON. WIND WILL GRADUALLY DECREASE WITH
TIME AND BY LATE TUESDAY AFTERNOON...BECOME LIGHT MAINLY FROM THE
SOUTHWEST.
&&
PREV DISCUSSION... /ISSUED 349 PM CST MON DEC 19 2011/
SHORT TERM...MORNING UPPER AIR ANALYSIS AND WATER VAPOR IMAGERY
INDICATE A MID AND UPPER LEVEL LOW OVER WEST TEXAS...MOVING NORTHEAST
INTO THE CENTRAL CONUS. WATER VAPOR IMAGERY ALSO INDICATES A MID
LEVEL DRY INTRUSION MOVING NORTHEASTWARD INTO NORTHERN TEXAS AND
PORTIONS OF OKLAHOMA. AT THE SURFACE AN AREA OF LOW PRESSURE EXISTS OVER
THE PANHANDLE OF TEXAS AND A SURFACE FRONT EXTENDS NORTHEAST FROM
THE SURFACE LOW INTO WESTERN AND NORTHERN OKLAHOMA...AS WELL AS
EASTERN KANSAS. KUEX INDICATES INCOMING PRECIPITATION OVER NORTH
CENTRAL KANSAS IN A ZONE OF LOW LEVEL THERMAL ADVECTION AND
RESULTANT ISENTROPIC UPGLIDE AND SATURATION. ADDITIONAL FORCING
THROUGH A ZONE OF MID LEVEL DIFFLUENCE IS ALSO HELPING PROMOTE
PRECIPITATION OVER AREAS NORTHEAST OF THE MID LEVEL LOW. SNOW IS
ALREADY IN PROGRESS AT NATOMA AS A RESULT.
THE LOW LEVEL BAROCLINIC ZONE CLEARED OUR CWA EARLIER TODAY AND
THE LOW LEVEL WIND FIELD ACROSS OUR CWA REMAINS FROM THE
NORTH/NORTHEAST AS A RESULT. SURFACE TEMPERATURES HAVE BEEN AT A
NEAR STANDSTILL IF NOT FALLING SOMEWHAT TODAY...WITH TEMPERATURES
AS OF MID AFTERNOON GENERALLY IN THE LOWER 30S. SHORT TERM GUIDANCE
CONTINUES TO SUGGEST THE MID LEVEL LOW WILL MOVE NORTHEAST ACROSS
THE SOUTHERN AND CENTRAL PLAINS TONIGHT AND TUESDAY. LOW LEVEL
THERMAL ADVECTION...WORKING IN CONCERT WITH MID LEVEL DIFFLUENCE AND
DEFORMATION TO THE NORTH AND NORTHEAST OF THE MID LEVEL LOW...WILL CONTINUE
PROMOTING PRECIPITATION PRODUCTION OVER THE AREA TONIGHT.
PRECIPITATION IS ALSO EXPECTED DURING THE DAY TUESDAY AS MID LEVEL
DEFORMATION TO THE NORTH AND NORTHWEST OF THE MID LEVEL LOW CLEARS
THE AREA.
MOISTURE THROUGH THE LOWER HALF OF THE TROPOSPHERIC COLUMN IS
EXPECTED TO REMAIN QUITE HIGH THROUGH THE NEXT 24 HOURS WITH 500MB
DEW POINTS IN EXCESS OF -25 DEGREES C AND 700MB DEW POINTS IN
EXCESS OF -10 DEGREES C ACROSS OUR SOUTH/SOUTHEAST. THESE MOISTURE
LEVELS...WORKING IN CONCERT WITH THE AFOREMENTIONED KINEMATIC
FORCING...SHOULD BE MORE THAN SUFFICIENT FOR SIGNIFICANT
PRECIPITATION PRODUCTION ACROSS OUR SOUTH AND SOUTHEAST TONIGHT AND
TOMORROW. QPF FIELDS FROM THE NAM...OPERATIONAL GFS...EC AND SREF-
MEAN ALL SUGGEST STORM TOTAL LIQUID PRECIPITATION AMOUNTS IN
EXCESS OF 0.80" ACROSS OUR SOUTH AND SOUTHEAST. SURFACE
TEMPERATURES WILL LIKELY FALL INTO THE UPPER AND MID 20S THROUGH
THE REMAINDER OF THE EVENT AND AS A RESULT WILL GO AHEAD AND
ASSUME A 10:1 SNOW-WATER RATIO TO START THE EVENT...WITH RATIOS
CLIMBING TO NEAR 13:1 BY TONIGHT AND TOMORROW. THIS YIELDS STORM
TOTAL SNOWFALL ACCUMULATIONS ON THE ORDER OF 5-12 INCHES ACROSS
OUR EXTREME SOUTH...AND STORM TOTAL SNOWFALL ACCUMULATIONS IN THE
1-5 INCH RANGE FARTHER NORTH.
LOW LEVEL PRESSURE RISES POST-FROPA HAVE PROMOTED AN INCREASED LOW
LEVEL PRESSURE GRADIENT TODAY...WITH SUSTAINED WINDS NEAR 20KTS
ACROSS MUCH OF THE CWA AS OF MID AFTERNOON. THESE CONDITIONS ARE EXPECTED
TO CONTINUE THROUGH THIS EVENING...WITH DIMINISHING WINDS EXPECTED
BY MIDNIGHT AS THE LOW LEVEL PRESSURE GRADIENT RELAXES. AS A
RESULT...THESE WINDS SHOULD REMAIN WELL BELOW BLIZZARD CRITERIA.
ALL THAT BEING SAID...THE INHERITED WINTER STORM WARNING FOR
ROOKS...OSBORNE AND MITCHELL COUNTIES...ALONG WITH THE WINTER
WEATHER ADVISORY FOR PHILLIPS...SMITH AND JEWELL COUNTIES...APPEAR
TO BE RIGHT ON...BUT DID GO AHEAD AND START THE WINTER STORM
WARNING NOW GIVEN SNOWFALL IS ALREADY OCCURRING AT NATOMA.
JUST A FEW THINGS TO CONSIDER AS WE HEAD INTO THIS STORM. THE
CONTRAST BETWEEN MOIST AIR AND DRY AIR...AS WELL AS BETWEEN STRONG
KINEMATIC FORCING AND NEXT TO NO FORCING...IS EXPECTED TO BE RATHER
SHARP THUS RESULTING IN A VERY TIGHT GRADIENT OF STORM TOTAL
SNOWFALL ACCUMULATIONS. ALTHOUGH CONFIDENCE REMAINS HIGH REGARDING
ACTUAL STORM TOTAL SNOWFALL ACCUMULATIONS...THE AXIS OF HEAVIEST
SNOW COULD SHIFT DRAMATICALLY IN RESPONSE TO VERY SMALL DEVIATIONS
IN STORM PATH. THANKFULLY...GUIDANCE HAS REMAINED FAIRLY
CONSISTENT WITH RESPECT TO STORM PATH...A TREND WHICH WE HOPE WILL
CONTINUE. FINALLY...GUIDANCE DOES SUGGEST THE MID LEVEL DRY
INTRUSION WILL INFILTRATE MUCH OF KANSAS BY TUESDAY MORNING...THUS
DRYING OUT THE DENDRITIC LAYER AND LIKELY LEADING TO A PERIOD OF
FREEZING DRIZZLE. AT THIS TIME IT APPEARS THIS MID LEVEL DRY
INTRUSION SHOULD REMAIN SOUTH AND SOUTHEAST OF OUR AREA AND AS A
RESULT...LEFT ANY MENTION OF FREEZING DRIZZLE OUT OF THE FORECAST.
LONG TERM...TUESDAY NIGHT THROUGH MONDAY. THE UPPER LOW WILL
CONTINUE TO MOVE NORTHEAST AND AWAY FROM THE AREA TUESDAY NIGHT.
THE MAJORITY OF MODEL SOLUTIONS SUGGESTS THE SNOW SHOULD BE DONE BY
TUESDAY NIGHT...AND WILL CONTINUE TO CARRY A DRY FORECAST.
A BRIEF H5 RIDGE BUILDS IN TUESDAY NIGHT INTO WEDNESDAY...WHICH
SHOULD KEEP IT DRY THROUGH WEDNESDAY...HOWEVER ANOTHER UPPER
TROUGH/LOW BEGINS TO APPROACH THE REGION WEDNESDAY NIGHT. THE
NAM/GFS/ECMWF ALL AGREE THAT MOST OF WEDNESDAY EVENING SHOULD REMAIN
DRY...HOWEVER LIGHT SNOW COULD BEGIN TO APPROACH FAR NORTH AND WEST
PORTIONS OF THE FORECAST AREA BY LATE EVENING. THE SNOW CHANCES
WILL THEN SPREAD ACROSS THE FORECAST AREA OVERNIGHT WEDNESDAY INTO
THURSDAY. THE NAM/GFS DEPICT THE STRONGEST LIFT/FORCING ACROSS
ROUGHLY THE SOUTHERN HALF OF THE CWA LATE WEDNESDAY NIGHT INTO
THURSDAY...AND HAVE INCREASED POPS FOR THAT AREA...ESPECIALLY FOR
THURSDAY. SNOW AMOUNTS ARE STILL UNCERTAIN...AND SREF 12 HOUR SNOW
PROBABILITIES FOR AN INCH OR MORE OF SNOW ARE NOT VERY HIGH...THOUGH
THE HIGHER PROBABILITIES ARE SHOWN IN THE SOUTH AND WEST.
ONE CONCERN IS THE POTENTIAL FOR HIGHER SNOW RATIOS WITH THE CARIBOU
SNOW TECHNIQUE SUGGESTING RATIOS CLIMBING TO NEAR 18 TO 1 FOR
THURSDAY AFTERNOON. FOR NOW...WILL GO WITH A GENERAL HALF INCH TO
INCH AND A HALF...WITH THE HIGHER AMOUNTS IN THE SOUTH AND WEST.
THERE IS STILL PLENTY OF TIME TO REFINE AMOUNTS AS THIS NEXT SYSTEM
GETS CLOSER.
OVERALL...THE CHRISTMAS HOLIDAY WEEKEND LOOKS TO BE FAIRLY QUIET.
ANOTHER WAVE COULD MOVE ACROSS THE REGION SATURDAY NIGHT INTO
CHRISTMAS DAY...BUT MOISTURE IS LACKING SO IT SHOULD PASS THROUGH
DRY. TEMPERATURES ARE EXPECTED TO BE FAIRLY SEASONABLE WITH HIGHS
PRIMARILY IN THE 30S.
PREV DISCUSSION... /ISSUED 1120 AM CST MON DEC 19 2011/
AVIATION...18Z TAF. IFR CEILINGS HAVE MOVED INTO PARTS OF SOUTH
CENTRAL NEBRASKA BEHIND A COLD FRONT THAT TRAVELED ACROSS THE
AREA EARLIER TODAY. THE GENERAL TREND HAS BEEN FOR THE IFR
CEILINGS TO LIFT TO MVFR...AND THIS IS ALSO SHOWN BY THE LATEST
NAM PROXIMITY SOUNDINGS..SO WILL ONLY CARRY THE LOWER CEILINGS IN
A BRIEF TEMPO GROUP. PROXIMITY SOUNDINGS ALSO SHOW THE MVFR
CEILINGS IMPROVING THIS AFTERNOON...THOUGH THE RUC IS FASTER IN
LIFTING THE CEILINGS THAN THE NAM. WILL AIM FOR MORE OF A
COMPROMISE SOLUTION AND GO WITH 21Z AS A START. WINDS WILL REMAIN
GUSTY AND FROM THE NORTH MOST OF THE AFTERNOON...BUT THEY SHOULD
DIMINISH THIS EVENING. THERE WILL BE CHANCES OF SNOW SOUTH OF
KGRI AS A STORM SYSTEM MOVES ACROSS THE CENTRAL AND SOUTHERN
PLAINS...BUT THINK THAT THE CHANCES WILL STAY FAR ENOUGH SOUTH TO
KEEP THE MENTION OUT OF THE FORECAST AT KGRI.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR KSZ005>007.
WINTER STORM WARNING UNTIL 6 PM CST TUESDAY FOR KSZ017>019.
&&
$$
SHORT TERM...BRYANT
AVIATION...HEINLEIN
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
1157 PM EST MON DEC 19 2011
.SYNOPSIS...
A FRONTAL BOUNDARY WILL STALL OUT NORTH OF THE AREA TONIGHT AND
TUESDAY WITH A MILD SOUTHWEST FLOW TO PREDOMINATE. MEANWHILE
STRONG LOW PRESSURE WILL LIFT WELL TO THE NORTHWEST OF THE REGION ON
TUESDAY NIGHT WITH ITS ASSOCIATED COLD FRONT WORKING EAST THROUGH
THE AREA ON WEDNESDAY. AN AREA OF LOW PRESSURE WILL TRACK THROUGH
THE CAROLINAS AND VIRGINIA ON FRIDAY. STRONG UPPER LEVEL HIGH
PRESSURE WILL HOLD BACK ANY INTRUSIONS OF COLDER AIR UNTIL LATE
WEEKEND OR EARLY NEXT WEEK.
&&
.NEAR TERM /THROUGH TUESDAY/...
AS OF 955 PM EST MONDAY...
STILL APPEARS THAT MOST OF THE WARM FRONTAL SHWOERY PRECIP WILL
REMAIN TO THE NORTHWEST OF THE BLACKSBURG FORECAST AREA
OVERNIGHT...HOWEVER ONLY ONE MODEL...LAST FEW RUNS OF THE HOURLY
HRRR...SHOWS ANY INDICATION OF THE ISOLATED SHOWERS LIFTING INTO
EASTERN KY FROM SOUTHERN KY...AND THOSE STAND A MUCH BETTER CHANCE
OF REACHING INTO WRN GREENBRIER OR EVEN SUMMERS COUNTIES A LITTLE
AFTER MIDNIGHT...SO LEANED TOWARD HRRR SOLUTION FOR THAT AND
SLIGHTLY INCREASED THE AREA OF CHC POPS AS WELL AS SLIGHT CHC
POPS. WITH HARDLY ANY BREAKS IN CLOUD COVER EXPECTED ACROSS THE
WEST...AM EXPECTING OVERNIGHT TEMPS TO REMAIN AT OR ABOVE
FREEZING AND SO NOW ONLY HAVE ONE OR TWO GRID POINTS IN GREENBRIER
SUGGESTING ANY SNOW MIXED IN WITH RAIN. ANY PRECIP WILL BE BARELY
MORE THAN A SPRINKLE ANYWAY.
18Z MODEL TRENDS ARE TO SLOW DOWN ANY THREAT OF EVEN LIGHT UPSLOPE
DRIZZLE ALONG THE SOUTHERN BLUE RIDGE UNTIL TOMORROW EVENING AS
MOIST SW FLOW INCREASED AHEAD OF APPROACHING MIDWEST SYSTEM...AND
THE SLOWER TIMING HAS BEEN A CONSISTENT TREND IN MODELS SO MAY BE
PRUDENT TO CONSIDER REMOVING ANY POPS DURING THE DAY TUES.
PREV UPDATE AS OF 710 PM EST MONDAY...
VERY MINOR UPDATE TO INCLUDE MENTION OF SLIGHT CHANCE SHWRS FROM
NOW THROUGH REST OF OVERNIGHT PER RADAR SHOWING WHAT MAY BE A FEW
SPRINKLES OVER THE HIGHER ELEVATIONS OF GREENBRIER AND MAYBE
REACHING PARTS OF BATH COUNTY SOON. STILL LOOKS LIKE ANY AREAS OF
STEADIER LGITH RAIN ASSOC WITH WAVE ALONG WARM FRONT WILL REMAIN
TO THE NORTH OF THE FCST AREA LATER ON TONIGHT...BUT AM KEEPING
THE TINY CORNER OF CHC POPS IN CLOSER TO 12Z. FCST SOUNDINGS
INDICATE NO CHC FOR FREEZING RAIN...MORE LIKELY A SNOW FLAKE THAT
SURVIVES BY WET BULBING THROUGH A PRETTY DRY LOWER ATMOS...SO
REMOVED FREEZING RAIN GRIDS AND INCLUDED A FEW SNOW OR SNOW MIXED
WITH RAIN...AGAIN ONLY A SLIGHT CHC. OTHERWISE MADE A FEW TWEAKS
TO SKTY COVER AND LATEST TEMPS AND DEW PTS...WITH SOME LOWER TEENS
DEW PTS AT SOME HIGHER ELEVATIONS. INCREASED WIND GUSTS ALONG SOME
OF THE RIDGES TO BETTER MATCH SOME RECENT OBS AT HSP.
PREV DISCUSSION AS OF 255 PM EST MONDAY...
RIBBON OF HIGHER MOISTURE/PRECIP FORECAST TO STREAM EASTWARD ALONG A
FRONTAL BOUNDARY EMANATING FROM THE STRONG LOW NOW BRINGING
EXTREME WINTER CONDITIONS TO PARTS OF THE SOUTHWESTERN U.S. HIGHER
RH WITH VERY LIGHT PRECIP COULD FLIRT WITH OUR FAR NORTHERN ZONES
AROUND 09-12Z BUT MODELS CONTINUE TO HOLD THE BULK OF COLD AIR
JUST TO THE NORTH OF THE CWA. H85 REMAINS JUST ABV 0C AND VARIOUS
MODEL P-TYPE ALGORITHMS AND THICKNESS PARAMETERS ALSO KEEP FROZEN
VARIETY JUST NORTH. THAT IS ASSUMING ANY PRECIP AT ALL MAKES IT
INTO THE CWA AND WHATEVER DOES FALL LOOKS TO BE VERY LIGHT.STILL
PLENTY OF DRY AIR OT OVERCOME AS 12Z RNK SOUNDING SHOWED PWAT OF
ONLY 0.24 INCHES OR ABOUT HALF OF NORMAL. SREF PROB AND ENSEMBLE
MEANS BRING VERY LITTLE IF ANY MEASURABLE TO FAR NORTHERN ZONES
EARLY IN THE MORNING. LEFT A FEW HOURS OF SLIGHT CHANCE POPS IN
THE GRIDS OVER GREENBRIER AND BATH COUNTIES WITH POCKETS OF MIXED
PCPN. THE CHANCE OF FROZEN WILL BE HIGHLY DEPENDENT ON HOW MUCH
DIURNAL FALL CAN OCCUR IN BREAKS IN THE OVERCAST AS MID-LEVEL
CLOUD COVER HAS ALREADY OVERTAKEN WESTERN CWA THIS AFTERNOON. LOWS
WILL GENERALLY BE HELD UP BY THIS CLOUD COVER AND WILL RANGE FROM
30S TO NEAR 40 IN MOST LOCATIONS...STILL WELL ABOVE NORMAL.
WHATEVER PRECIP DOES MANAGE TO SNEAK INTO THE FAR NORTHERN ZONES
WILL BE SHORT-LIVED AS POPS DECREASE THROUGH THE DAY WITH THE
BOUNDARY REMAINING STATIONARY AND THEN STARTING A NORTHWARD
RETREAT. ANOTHER MILD DAY TOMORROW IS IN THE CARDS WITH SOUTHERLY
FLOW INCREASING AHEAD OF THE SURFACE LOW BACK OVER THE LOWER
MISSISSIPPI VALLEY. GUIDANCE SHOWING LOW 50S IN THE FAR NORTH AND
MOUNTAINS TO LOW 60S IN THE PIEDMONT...AGAIN AT LEAST 10F ABOVE
MID-DECEMBER CLIMO.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
AS OF 330 PM EST MONDAY...
ECMWF AND SREF A LITTLE SLOWER WITH QPF TUESDAY NIGHT...SO AGAIN
BACKED OFF ABOUT 6 HRS FROM PREVIOUS GRIDS. BEST CHC FOR RAIN WILL
BE WED MORNING...WITH JUST SPOTTY SHOWERS IN THE AFTERNOON. MAX T
WILL BE TOUGH THIS DAY BECAUSE RAIN ARRIVING EARLY IN THE MORNING
MAY MAKE IT DIFFICULT FOR TEMPS TO REBOUND IN THE AFTERNOON
DESPITE DOUBLE DIGIT H85 TEMPS. WENT A FEW DEGREES BELOW GUIDANCE...WITH
THE EXCEPTION OF THE SOUTHSIDE. SOME SLIGHTLY COOLER AIR DOES
ARRIVE ACROSS SE WEST VA LATE PM AND OVERNIGHT AS THE COLD FRONT
ENTERS THE CWA. ANOTHER WAVE WILL RIDE ALONG THE OLD DECAYING
BOUNDARY SUCH THAT RAIN ARRIVES MAINLY THURSDAY NIGHT. THE
GFS/ECMWF ARE IN GOOD AGREEMENT THIS FAR OUT SO INCREASED POPS.
PERHAPS SOME DOWNSLOPING AND CLEARING WILL ALLOW BETTER MIXING AND
THUS WARMER TEMPS ON THURSDAY IN COMPARISON TO WEDNESDAY. A WARM
BUT WET NIGHT FOLLOWS THURSDAY NIGHT. CONSIDERING CLOUDS AND H85
TEMPS WENT ABV GUIDANCE FOR MINS.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 330 PM EST MONDAY...
ECMWF/GFS DIVERGE MORE THOUGH INTO THE HOLIDAY WEEKEND...WITH THE
ECMWF PUSHING THE FRONT FURTHER OFF THE COAST IN COMPARISON TO THE
GFS. THE OP GFS IS QUICKER WITH A DISTURBANCE MOVING OUT OF THE
MIDWEST THAN THE ECMWF WHICH HOLDS MUCH OF THIS UPPER LEVEL
POSITIVELY TILTED TROUGH BACK INTO THE ROCKIES. THIS MEANS THAT
THE OP GFS HAS A STRONG ARCTIC HIGH OVER MAINE...AND DEVELOPS A
STRONG WEDGE WITH LOW PRESSURE GOING UP THE COAST EARLY SATURDAY.
THIS SOLUTION WOULD SUGGEST THE POTENTIAL FOR A WINTRY MIX ACROSS
THE SOUTHERN SHENANDOAH INITIALLY EARLY CHRISTMAS EVE DAY. THE
EUROPEAN...WHICH CONTINUES TO BE THE MORE SKILLFUL MODEL DAY 5 AT
H5...FROM 12Z...HOLDS THE HIGH PRESSURE FURTHER WEST INTO SE
CANADA...AND IT DOES NOT MOVE QUICK ENOUGH EAST TO WEDGE DOWN THE
APPALACHIANS...MEANING A WARMER SOLUTION WITH LOW PRESSURE
TRAVELING FURTHER WEST FROM THE COAST. CONFIDENCE IS LOW
ATTM...BUT WOULD LEAN MORE TOWARDS THE ECMWF EVEN THOUGH IT DOES
HAVE A STRONG BIAS WITH REGARDS TO SOUTHEASTERN US RIDGING. ON THE
CONTRARY...THE SE CONUS RIDGE HAS BEEN A DOMINANT FEATURE THIS
EARLY COOL SEASON SO A WARMER SOLUTION...LIKE THE ECMWF IS MORE
APPROPRIATE. THUS WILL HOLD BACK THE COLDEST AIR IN THE GRIDS
UNTIL MONDAY AND MONDAY NIGHT...WITH JUST RAIN THIS WEEKEND AND
SOME UPSLOPE SNOW SHOWERS ACROSS SE WEST VA CHRISTMAS DAY AND
EARLY MONDAY.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AS OF 1150 PM EST MONDAY...
VFR MID TO HIGH CLOUDS THROUGH THE DAY TUESDAY...ONLY A VERY
SLIGHT CHANC FOR A STRAY SHOWER AT LWB DURING THE REMAINDER OF
EARLY TUESDAY MORNING OVERNIGHT HOURS BUT EXPECTING LOW END VFR TO
PREVAIL. JUST MENTIONED SHOWER IN VCNTY. OTHERWISE LOWERING CEILINGS
BY TUESDAY EVENING INTO OVERNIGHT WITH MVFR CIGS BETWEEN 00 AND 06
Z AT BLF...BCB...AND POSSIBLY DAN. GUIDANCE WANTS TO BRING IN VERY LOW
CIGS AND PERHAPS DRIZZLE TO BCB BEFORE 03Z WITH INCREASING SOUTHERLY
MOIST FLOW...BUT BLV A LITTLE OVERDONE WITH THIS. MORE LIKELY
BETWEEN 06 AND 09Z. ANY IFR CIGS AND VSBYS WITH LIGHT SHWRS OR
DRIZZLE WOULD BE CONFINED TO NEAR BLUE RIDGE TUES EVENING.
CLOSER TO DAWN WED MORNING BETTER CHANCE FOR SHWRS WITH MVFR TO
IFR CONDITIONS AT BLF...LWB...AND BCB...AND LIKELY ONLY ONLY BRIEF
PERIODS OF SUB VFR ELSWHERE LATER IN THE DAY WED. BRIEF VFR
RETURNS THURSDAY FOLLOWED BY A SECOND STORM SYSTEM BY FRIDAY WHICH
MAY BRING ANOTHER ROUND OF RAIN AS WELL AS LOW CIGS AND VSBYS
THURSDAY NIGHT INTO FRIDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...JH/KM
NEAR TERM...PC/SK
SHORT TERM...KM
LONG TERM...KM
AVIATION...JH/PC/SK/WP
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1120 PM CST MON DEC 19 2011
.SHORT TERM...THROUGH WEDNESDAY NIGHT
246 PM CST MON DEC 19 2011
MAIN FORECAST CONCERN IS WITH THE PRECIPITATION CHANCES AND TYPES
TUESDAY AND TUESDAY NIGHT.
SURFACE ANALYSIS THIS AFTERNOON SHOWS A NEARLY STATIONARY FRONT
FROM LOWER MICHIGAN TO AN AREA OF LOW PRESSURE OVER EASTERN NEW
MEXICO. HIGH PRESSURE WAS CENTERED OVER THE WESTERN DAKOTAS AND
EASTERN MONTANA.
STRATUS CLOUDS HAVE COME IN BEHIND THE COLD FRONT AND COVERED
ALMOST THE ENTIRE AREA THIS AFTERNOON. VISIBLE SATELLITE DOES
SHOW QUITE A FEW HOLES IN THE CLOUD FIELD AND THE CLOUDS ALSO
APPEAR TO BE THINNING OUT. THE 19.12Z NAM BUFKIT SOUNDINGS WOULD
SUGGEST THE CLOUDS SHOULD SCATTER OUT THIS EVENING WHILE SEVERAL
RUNS NOW OF THE RUC DO NOT SCATTER THE CLOUDS OUT UNTIL THE
OVERNIGHT HOURS. HAVE TRIED TO BALANCE THESE MODEL TRENDS WITH THE
CURRENT SATELLITE TRENDS TO SHOW CLEARING THROUGH THE EVENING FOR
MOST OF THE AREA. THIS WILL ALSO HAVE A BIG IMPACT ON THE
TEMPERATURES. HAVE BUMPED THE TEMPERATURES UP SOME...ESPECIALLY
ACROSS THE NORTH WHERE THE CLOUDS MAY HOLD ON THE LONGEST...BUT IF
THEY CLEAR OUT EARLIER THAN EXPECTED...THESE WILL HAVE TO BE MOVED
DOWN.
THE STORM SYSTEM OVER THE SOUTHWEST WILL BE EJECTING NORTHEAST
TOWARD THE OHIO RIVER VALLEY AND EASTERN GREAT LAKES FOR TUESDAY
THROUGH WEDNESDAY. AFTER A NORTHWARD JOG IN THE TRACK OF THIS
SYSTEM WITH YESTERDAY/S MODELS...ALL THE 19.12Z MODELS HAVE
SETTLED BACK SOUTH WITH THE TRACK. IT ONCE AGAIN APPEARS THAT THE
SOUTHERN PARTS OF THE AREA WILL EITHER GET BRUSHED WITH THIS SYSTEM
OR IT WILL JUST MISS TO THE SOUTH. THE NAM AND GFS STILL SHOW
DECENT FORCING WITH THIS SYSTEM JUST GOING BY TO THE SOUTH.
BETWEEN 4 AND 8 PVU/S OF VORTICITY ADVECTION IN THE 500-300 MB
LAYER PASSES BY TUESDAY AFTERNOON AND NIGHT. THE BEST QG
CONVERGENCE IS EXPECTED TO MISS THE AREA WITH JUST SOME WEAK
CONVERGENCE IN THE 700-500 MB LAYER COMING THROUGH TUESDAY NIGHT.
STILL EXPECTING TO SEE SOME WEAK FRONTOGENESIS IN THE 850-500 MB
LAYER AS WELL. ONE THING THAT HAS NOT CHANGED IN THE MODELS...IS
WHETHER THERE WILL BE ICE PRESENT IN THE CLOUDS. BUFKIT SOUNDINGS
ACROSS THE FAR SOUTH CONTINUE TO SUGGEST CLOUD TOP TEMPERATURES
ONLY AROUND -10C WHICH COULD LEAD TO MORE LIQUID INSTEAD OF SNOW.
HAVE CONTINUED WITH THE MIX OF FREEZING RAIN/RAIN AND SNOW BUT
WITH ONLY LIGHT PRECIPITATION AMOUNTS ANTICIPATED...ANY SNOW OR
ICE ACCUMULATIONS WILL BE VERY LIGHT.
ONCE THIS SYSTEM GOES BY...A NORTHERN STREAM SHORT WAVE TROUGH
WILL MOVE ALONG THE CANADIAN BORDER WEDNESDAY NIGHT. THIS WAVE
WILL PUSH A COLD FRONT INTO THE AREA THAT COULD POSSIBLY PRODUCE
SOME LIGHT SNOW AND HAVE CONTINUED WITH THE LOW END SNOW CHANCES
ACROSS THE NORTH WITH THIS SYSTEM.
.LONG TERM...THURSDAY THROUGH MONDAY
246 PM CST MON DEC 19 2011
THE COLD FRONT WILL CONTINUE TO PUSH SOUTH ACROSS THE REMAINDER OF
THE AREA THURSDAY AND COULD STILL BE PRODUCING SOME LIGHT SNOW.
ADDED IN SOME LOW END SNOW CHANCES TO HANDLE THIS POSSIBILITY.
ONCE THIS SYSTEM GOES BY...THE REMAINDER OF THE PERIOD LOOKS TO BE
PRETTY QUIET. ANOTHER NORTHERN STREAM WAVE COULD BRUSH THE UPPER
MIDWEST CHRISTMAS DAY AND HAVE CONTINUED WITH THE LOW SNOW CHANCES
ACROSS THE NORTHERN PART OF THE FORECAST AREA AS THE BEST FORCING
WITH THIS WAVE LOOKS TO REMAIN TO THE NORTH OF THE AREA.
&&
.AVIATION...THROUGH 06Z WEDNESDAY
1120 PM CST MON DEC 19 2011
THE MAIN CONCERN FOR THE TERMINAL IS IN THE VERY NEAR TERM WITH
HOW LONG THE 2500FT CEILINGS HOLD ON AT RST. AS OF 5Z...THERE IS A
NARROW STRIP OF THESE LOWER CEILINGS THAT EXTENDS FROM PRESTON
NORTH THROUGH ROCHESTER TOWARD THE TWIN CITIES. THE CLEARING BACK
EDGE IS A COUNTY AWAY TO THE WEST AND IS EXPECTED TO EVENTUALLY
WORK EASTWARD. FOR NOW...HAVE KEPT SOME 2500FT CIGS IN THERE FOR A
FEW HOURS BEFORE THEY CLEAR OUT. OTHERWISE AT LSE...CEILINGS HAVE
BEEN VFR THROUGH THE NIGHT AND ARE EXPECTED TO REMAIN THAT WAY
THROUGH THE MORNING. BEYOND THIS...WINDS WILL REMAIN LIGHT AND
COME AROUND TO THE SOUTH TODAY AS A RIDGE AXIS MOVES THROUGH. HIGH
CLOUDS WILL CONTINUE TO BLANKET THE REGION WELL TO THE NORTH OF A
POTENT STORM SYSTEM MOVING THROUGH THE PLAINS.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
246 PM CST MON DEC 19 2011
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
SHORT TERM...04
LONG TERM...04
AVIATION...HALBACH
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
643 AM EST TUE DEC 20 2011
.AVIATION...
MOIST SOUTHERLY FLOW AHEAD OF STRONG SRN PLAINS LOW OVER-RUNNING
STALLED CDFNT OVER SRN INDIANA/OH RESULTING IN AN E-W BAND OF
PRECIP WITH IFR CONDITIONS ACROSS NRN INDIANA THIS MORNING. AS
LOW CONTINUES TO MOVE NE TODAY FRONT WILL LIFT SLOWLY NORTH AS A
WARM FRONT CAUSING RNSN MIX TO CHANGE OVER TO ALL RAIN BY MID-
MORNING AT FWA. MID LEVEL DRY SLOT SHOULD OVERSPREAD THE AREA THIS
AFTN ENDING OVER-RUNNING PRECIP...LIKELY BEFORE IT REACHES SBN.
IFR CONDITIONS SHOULD PERSIST AT FWA THROUGH THE DAY WITH CEILINGS
LOWERING TO MVFR AT SBN. AS WARM FRONT CONTS TO LIFT NORTH INTO
NRN INDIANA TONIGHT EXPECT FLYING CONDITIONS TO LOWER TO LIFR WITH
STRATUS/FOG AND LIGHT RAIN/DRIZZLE.
&&
.PREV DISCUSSION... /ISSUED 419 AM EST TUE DEC 20 2011/
SHORT TERM.../TODAY THROUGH WEDNESDAY NIGHT/
STRONG ISENTROPIC LIFT HAS ALLOWED FOR BAND OF PERSISTENT PRECIP
FROM SOUTHERN QUARTER OR SO OF THE FORECAST AREA BACK TO THE WEST
ACROSS MUCH OF CENTRAL AND SOUTHERN ILLINOIS. EARLIER TAMDAR
SOUNDINGS INDICATED THAT RISK FOR SNOW MAY BE MINIMAL INTO TUES
MORNING. HOWEVER...RECENT SFC OBS AND CALL AROUND TO CENTRAL
DISPATCHES IN SOUTHERN AREAS SHOWS RAIN HAS BEEN MIXING WITH AND
EVEN CHANGING TO SOME LIGHT SNOW. MAIN SWITCH OVER HAS BEEN
OCCURRING IN SE AREAS WHERE NE FLOW HAS ALLOWED SLIGHTLY COLDER
TEMPS TO MIX FURTHER THROUGH THE COLUMN. SFC TEMPS WERE ABOVE
FREEZING ACROSS THE AREA WITH ANY SNOW MELTING AS IT FALLS. OF
CONCERN IS NEW 6Z NAM12 WHICH SUGGEST A SWATH OF LOCALLY HEAVIER
PRECIP MAY ARRIVE TOWARDS 12Z AND FALL IN AREA WHERE COOLING MAY BE
MAXIMIZED. GRIDS HAVE HAD LIGHT ACCUMS IN FOR SEVERAL DAYS AND HAVE
KEPT THIS THINKING GENERALLY THE SAME THROUGH THIS MORNING. KFWA
OBSERVER JUST CONTACTED US WITH A FEW TENTHS OF AN INCH ON VEHICLES
BUT EVERYTHING MELTING ON THE GROUND. BLEND OF RUC AND LOCAL WRF WAS
USED TO GET POP LAYOUT TODAY WITH VERY TIGHT CUT OFF TO THE NORTH AS
LOCATIONS NORTH OF US 6 MAY SEE LITTLE OR NO PRECIPITATION. LOCAL
WRF AND HRRR WANT TO QUICKLY DRY THINGS OUT IN THE 21 TO 00Z TIME
FRAME AS BEST FORCING SHIFTS NORTH WITH THE WARM FRONT PASSING
THROUGH. THIS COULD LEAVE MUCH OF THE AREA EITHER DRY OR WITH SOME
AREAS OF DRIZZLE. HAVE MADE NO CHANGES TO THIS AFTERNOON WITH CHC
POPS REMAINING IN FAR N AND NW AREAS AND LIKELY REMAINDER OF THE
AREA. WILL LET DAY SHIFT MONITOR TRENDS.
UPPER LOW WILL TRACK TOWARDS THE REGION LATER TONIGHT INTO WEDS.
MODELS STILL VARY ON PATH OF THIS FEATURE EITHER BEING OVER THE AREA
OR JUST TO THE SE. STILL THINK MOST AREAS WILL SEE A CHANCE FOR
LIGHT RAIN FOR AT LEAST A 6 TO 12 HOUR PERIOD BEFORE ENDING BY WEDS
EVENING.
IN TERMS OF TEMPS THROUGH THE PERIOD...EXPECTING LITTLE OVERALL
CHANGE IN SFC TEMPS TODAY ACROSS THE NORTH AND A SLOW WARM UP IN
SOUTHERN AREAS ESPECIALLY AS WARM FRONT MOVES NORTH. IF ANY BREAKS
IN THE CLOUDS CAN FORM LATER THIS AFTERNOON...COULD SEE HIGHS WARMER
THAN FORECAST. HOWEVER...OBS TO THE SOUTH SHOW PRETTY EXTENSIVE
CLOUD COVER SO WILL HOLD OFF ON ANY CHANGES FOR HIGHS TODAY. HIGHS
ON WEDS COULD VARY GREATLY DEPENDING ON THE TRACK OF THE UPPER LOW
WITH WARMEST READINGS SE WHERE HIGHS COULD EASILY CLIMB INTO THE
50S. OVERNIGHT LOWS BOTH NIGHTS EXPECTED TO REMAIN ABOVE FREEZING.
LONG TERM.../THURSDAY THROUGH MONDAY/
NEXT IN SERIES OF SRN STREAMS SHRTWVS EMANATING FROM SPLIT FLOW
OVER WRN U.S. WILL LIFT RAPIDLY NE FROM THE SRN PLAINS TO THE LWR
OH VALLEY THU EVE. THIS SYSTEM SHOULD BE CONSIDERABLY WEAKER THAN
ITS PREDECESSOR DUE TO MORE SHEARING FM INTERACTION WITH NRN
STREAM SHRTWV MOVG ESE INTO THE UPR GRTLKS AT THE SAME TIME. PER
GFS SOLUTION... SFC/H85 BAROCLINIC ZONE EXPECTED TO REMAIN FAR
ENOUGH TO THE S-SE TO KEEP NWRN EDGE OF PRECIP SHIELD WITH THIS
SYSTEM JUST SE OF OUR CWA. WK WAA AHEAD OF THE NRN STREAM
SHRTWV/CDFNT SHOULD ALLOW HIGHS TO REACH THE L-M40S ACROSS THE
AREA DESPITE CONSIDERABLE CLOUDINESS.
CDFNT WILL MOVE THROUGH THE AREA BY THU EVE WITH HIGH PRESSURE OVER
THE NRN PLAINS BUILDING EAST ACROSS THE WRN GRTLKS IN ITS WAKE. WK
CONVERGENCE ALONG FRONT AS IT MERGES WITH CIRCULATION OF SURFACE LOW
TO THE SE SUGGESTS JUST SOME CLOUDINESS WILL ACCOMPANY IT... BUT
LITTLE CHC OF MEASURABLE PRECIP. FAIRLY WK CAA WITH H85 TEMPS ONLY
FALLING TO -2C/-4C ACROSS THE CWA COMBINED WITH CLOUDINESS SUGGESTS
LOWS WILL ONLY BE IN THE U20S/L30S THU NGT.
FOR THE EXTENDED DAYS 4-7...MEDIUM RANGE MODELS IN DECENT AGREEMENT
INDICATING MEAN TROF OVER WRN U.S. IN SHORT TERM WILL PROGRESS TO
NEAR THE EAST COAST BY THE END OF THE LONG TERM PERIOD. THIS SHOULD
RESULT IN A GRADUAL COOL DOWN OVER THE HOLIDAY WEEKEND WITH A WARMUP
EARLY NEXT WEEK AS RIDGING ALOFT MOVES INTO THE GRTLKS IN THE WAKE
OF THIS TROF. SPLIT FLOW WILL PERSIST AS THE MEAN TROF MOVES EAST...
AT LEAST THROUGH FRIDAY OR SAT. MODELS HAVE VERY DIFFERENT
TIMING/TRACK/INTENSITY WITH SHRTWV LIFTING OUT OF THE SRN STREAM
FLOW OVER THE WEEKEND... THUS LITTLE CONFIDENCE IN THE POPS SATURDAY
BUT MAINTAINED FCST CONTINUITY BY FOLLOWING GFS SOLUTION WHICH
INDICATES A CHC OF RAIN/SNOW IN OUR AREA AROUND THIS PERIOD. IN THE
WAKE OF THIS SYSTEM... NRN STREAM TROF PROGGED TO STRENGTHEN/DIG SE
A BIT WHICH SHOULD ALLOW AIRMASS OVER THE WRN GRTLKS TO BECOME COLD
ENOUGH FOR SOME LAKE EFFECT SNOW SHOWERS BY LATE SUNDAY... THOUGH
DOESN`T LOOK LIKE A FAVORABLE SETUP FOR SGFNT LES ATTM WITH GFS
INDICATING FAIRLY LOW INVERSION HEIGHTS.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SHORT TERM...FISHER
LONG TERM...JT
AVIATION...JT
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
621 AM CST TUE DEC 20 2011
.UPDATE...
.AVIATION /FOR THE 12Z TAF ISSUANCE/
IFR CONDITIONS WILL PERSIST THROUGH THE NEXT SEVERAL HOURS BASED ON
BOTH LOW CEILINGS AND VISIBILITIES REDUCED IN SNOW. SOME IMPROVEMENT TO
THE MVFR RANGE IS POSSIBLE BY AROUND 18 UTC AS THE UPPER LOW LIFTS
FARTHER INTO EASTERN KANSAS. WINDS WILL ALSO BE DIMINISHING INTO HE
15 TO 25 MPH RANGE LATER IN THE DAY, SUPPORTED BY LOCAL GFS MOS
GUIDANCE.
&&
.PREV DISCUSSION... /ISSUED 232 AM CST TUE DEC 20 2011/
DISCUSSION...
DAYS 1-2...
00Z TUESDAY UPPER AIR ANALYSIS PLACED A 850MB AND 700MB
BAROCLINIC ZONE FROM JUST NORTH OF ELKHART TO NEAR HAYS. THE UPPER
LOW WAS POSITIONED NEAR AMARILLO. STILL OBSERVING GOOD MOISTURE
AND WARM AIR ADVECTION ACROSS CENTRAL AND PARTS OF SOUTHWEST
KANSAS AS OUR UPPER LOW MOVES TOWARDS NORTHWEST OKLAHOMA EARLIER
THIS MORNING. JET STREAK DYNAMICS NEAR THE LEFT EXIT REGION OF
250MB JET WILL BE LOCATED ACROSS PORTIONS OF NORTH CENTRAL KANSAS
EARLY THIS MORNING SO AT THIS TIME BASED ON THE LOCATION OF THE
MID LEVEL FRONTOGENESIS IT WOULD APPEAR THAT PERIODS OF MODERATE
SNOW STILL WILL BE POSSIBLE IN AREAS ALONG AND NORTH OF HIGHWAY
156. THE NAM, RUC, AND HRRR WERE ALSO ALL IN DECENT AGREEMENT WITH
PRECIPITATION CONTINUING THROUGH THE EARLY MORNING HOURS IN THIS
AREA SO INITIAL THOUGHTS WILL BE TO FOLLOW THE GENERAL TRENDS OF
THE NAM,RUC AND HRRR OVER THE NEXT 6-9 HOURS. FURTHER WEST NEAR
THE COLORADO BORDER AND AREAS SOUTH NEAR THE OKLAHOMA BORDER THE
PRECIPITATION SHOULD BE STARTING TO TAPER OFF.
WINDS STILL WILL BE AN ISSUE EARLY TUESDAY MORNING GIVEN THE
LOCATION OF THE PRESSURE GRADIENT NORTHWEST OF THE SURFACE LOW
ALONG WITH THE CURRENT VAD WINDS AND PROFILER DATA. ALTHOUGH WIND
SPEEDS ARE NOT EXPECTED TO BE AS STRONG AS YESTERDAY, IT DOES
APPEAR THAT SOME REDUCED VISIBILITIES WILL CONTINUE IN THE
BLIZZARD WARNING AREA. LOCATIONS SOUTH OF HIGHWAY 156 WILL SEE
IMPROVING CONDITIONS EARLY THIS MORNING BUT GIVEN ONGOING SNOW,
BLOWING SNOW AND CURRENT CONDITIONS HAVE DECIDED NOT TO BEGIN
TRIMMING THE BLIZZARD WARNING YET.
BY MID DAY ISENTROPIC DOWN GLIDE WILL BEGIN TO DEVELOP WEST OF
OUR UPPER LOW WHICH WILL BE LOCATED NEAR SOUTH CENTRAL KANSAS. A
SURFACE HIGH WILL THEN BEGIN TO BUILD INTO WESTERN KANSAS FROM THE
NORTHWEST. MODEL SOUNDINGS CONTINUE TO SUGGEST TO CLOUD COVER
THROUGH MUCH OF THE DAY SO BASED ON THIS AND COLD AIR ADVECTION
OCCURRING OVER THE SNOW PACK WILL UNDERCUT GUIDANCE FOR HIGHS
TODAY.
TONIGHT SKIES WILL CLEAR AS WINDS DECREASE TO LESS THAN 10KTS.
WINDS NOT IDEAL FOR A GREAT NIGHT OF RADIATION COOLING BUT
CONDITIONS STILL FAVOR UNDERCUTTING CURRENT GUIDANCE AND STAYING
CLOSE TO THE CURRENT FORECAST OF WITH LOWS EARLY WEDNESDAY MORNING
IN THE SINGLE DIGITS.
WEDNESDAY SHOULD BE SUNNY AS WESTERLY DOWNSLOPE FLOW IMPROVES
ACROSS WESTERN KANSAS. DECENT WARMING OCCURS ABOVE THE SURFACE BUT
BASED ON SNOWFALL EXPECTED ACROSS SOUTHWEST KANSAS FEEL MUCH OF
THE WARMING WILL GO INTO SNOW MELT. AS A RESULT WILL UNDERCUT
GUIDANCE ONCE AGAIN AND FAVOR THE PREVIOUS FORECAST WHICH IS CLOSE
TO 10F COOLER THAN THE COOLEST GUIDANCE.
DAYS 3-7...
LONG TERM /THURSDAY THROUGH MONDAY/
A PROGRESSIVE LONGWAVE PATTERN IS IN STORE FOR THE EXTENDED PERIOD,
WITH AT LEAST A COUPLE OF ADDITIONAL COLD FRONTAL PASSAGES ACROSS
THE CENTRAL HIGH PLAINS.
AFTER THE MAJOR SYSTEM THAT IS CAUSING THE BLIZZARD RIGHT NOW OVER
WESTERN KANSAS LIFTS EASTWARD INTO THE UPPER MIDWEST ON TUESDAY
NIGHT AND WEDNESDAY, ANOTHER PAIR OF SHARP MID LEVEL IMPULSES WILL
BE ROTATING THROUGH THE MEAN TROUGH. THE FIRST WILL ROTATE SOUTHWARD
FROM THE NORTHERN ROCKIES AND THE SECOND, JUST AHEAD OF THE NORTHERN
STREAM SHORTWAVE, FROM THE DESERT SOUTHWEST. FROM A LOOK AT THE GFS
AND ECMWF THE TWO WAVES APPEAR TO ENHANCE THE MID LEVEL BAROCLINICITY
ACROSS WESTERN KANSAS ON THURSDAY, WHILE A SURFACE COLD FRONT DIVES
SOUTHWARD ACROSS THE AREA EARLY IN THE DAY. BOTH MODELS HAVE BEEN
CONSISTENT IN PRODUCING BETWEEN 0.05" AND 0.15" OF PRECIPITATION
TIED TO THE LEADING SHORTWAVE, WITH POST SURFACE FRONT QPF. QUITE COLD
850 MB AIR ABOUT -5 T0 -8 SHOULD ENSURE THE PRECIPITATION TYPE WOULD
BE SNOW, AND AS A RESULT, IT IS POSSIBLE CENTRAL KANSAS AND MUCH OF
SOUTHWEST WILL BE EXPERIENCING ADDITIONAL, BUT PROBABLY MINOR
ACCUMULATIONS ON THURSDAY AFTERNOON. THE REMAINDER OF THE FORECAST
DOES LOOK DRY, BUT COLD. THE SECOND OF THESE UPPER SHORTWAVES
ROTATES THROUGH THE MEAN TROUGH ON FRIDAY AND SURFACE WINDS BEGIN TO
WEAKEN AS THE UPPER LEVEL HEIGHT FIELDS BECOME PARALLEL TO THE
MOUNTAIN BARRIER. FRIDAY WILL REMAIN COLD WITH VERY WEAK SURFACE
WINDS OVER THE AREA, BUT THE 850 MB TEMPERATURES BEGIN TO INCREASE
WITH STRONGER DOWNSLOPE FLOW OVER THE SNOWPACK. MODELS SEEM TO BUMP
MAXIMUM TEMPERATURES ABOUT 5 DEGREES ON SATURDAY AFTERNOON, BUT THIS
IS STILL WELL BELOW NORMAL. THE MODELS CONTINUE THOUGH THE END OF
THE WEEKEND DRY AND COOL WITH DEEP NORTHWEST FLOW OVER THE HIGH
PLAINS REGION INTO MONDAY.
AVIATION...
FOR THE 06Z TAF ISSUANCE... BLIZZARD OR NEAR BLIZZARD CONDITIONS
WILL CONTINUE THROUGH EARLY TUESDAY MORNING WITH THE DOMINANT
FLIGHT CATEGORY BEING VLIFR AT GCK AND DDC THROUGH MUCH OF THE
NIGHT TOWARD DAYBREAK. WIND SPEEDS WILL GRADUALLY DECREASE BY
DAYBREAK WITH VISIBILITIES IMPROVING AS WELL. AFTER THE SNOW
CEASES...LOW OVERCAST WILL LIKELY PERSIST THROUGH AT LEAST THE
EARLY AFTERNOON BEFORE CLEARING TAKES PLACE AND VFR CONDITIONS
RESUME. -UMSCHEID
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 27 9 30 14 / 90 0 0 10
GCK 28 6 29 13 / 90 0 0 10
EHA 27 5 29 13 / 50 0 0 10
LBL 27 6 30 15 / 50 0 0 10
HYS 29 6 30 15 / 100 0 0 20
P28 32 14 38 23 / 70 10 0 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WARNING UNTIL NOON CST /11 AM MST/ TODAY FOR KSZ030-031-
043>046-061>066-074>080-084>088.
WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR KSZ081-089-090.
&&
$$
FN99/99
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1044 AM EST TUE DEC 20 2011
.SYNOPSIS...
A COLD FRONT STALLING ACROSS THE UPPER OHIO VALLEY WILL PROVIDE
RAIN TODAY. HOWEVER, THERE CAN BE A SHORT PERIOD OF WET SNOW THIS
MORNING NORTH OF PITTSBURGH. LOW PRESSURE, COMING NORTHEAST FROM TEXAS,
WILL BRING MILDER TEMPERATURES AND RAIN TONIGHT AND WEDNESDAY.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
UPDATED TO EXTEND PATCHY DENSE FOG IN THE MOUNTAINS FOR SEVERAL HOURS.
PER RECENT RADAR AND SURFACE DATA, COUPLED WITH RECENT HRRR AND
NAM MODEL OUTPUT, EXPECT PRECIPITATION ACROSS THE ENTIRE UPPER
OHIO VALLEY INTO MIDDAY. RECENT SURFACE DATA SHOWS LOW
VISIBILITIES ACROSS HIGHER TERRAIN WHICH CAN AFFECT TRAVEL ON
I-68 AND PA TURNPIKE.
THE COLD FRONT MOVING SLOWLY SOUTH FROM THE I-80 CORRIDOR MAY
LOWER SURFACE TEMPERATURES ENOUGH TO CAUSE A CHANGE TO WET SNOW
FOR A TIME THIS MORNING AS FAR SOUTH AS COLUMBIANA COUNTY OHIO,
BEAVER COUNTY, NORTHERN ALLEGHENY COUNTY AND NORTHERN INDIANA
COUNTY PENNSYLVANIA...ALSO ACROSS THE HIGHER MOUNTAIN RIDGES
FARTHER SOUTH. RAIN-WETTED GROUND SHOULD RESULT IN MINIMAL SNOW
ACCUMULATION, IF ANY.
WILL ISSUE STATEMENT REGARDING THE POSSIBILITY OF ICY CONDITIONS
WHERE TEMPERATURES REACH THE FREEZING POINT NEAR THE I-80
CORRIDOR. WILL ALSO ISSUE A STATEMENT MENTIONING LOW VISIBILITIES
IN FOG FOR HIGHER TERRAIN SOUTH.
EXPECT TEMPERATURES TO BEGIN SLOWLY WARMING LATER THIS MORNING, AS POSTFRONTAL
NORTH WINDS ABATE BEHIND THE STALLING COLD FRONT. THIS WILL
LIKEWISE ALLOW DAYTIME PROCESSES TO RAISE TEMPERATURES ALSO. HENCE
LOCATIONS WITH WET SNOW EARLY THIS MORNING SHOULD SEE IT END BY
MIDDAY. NAM MODEL OUTPUT SHOWS SOUTHEASTERLY WINDS INCREASE AHEAD
OF THE LOW PRESSURE CENTER INCOMING FROM TEXAS, CAUSING A SLOW
WARM UP INTO TONIGHT.
MODELS SHOW THERE MAY BE A BREAK IN THE RAIN SHOWERS EARLY TONIGHT, THEN
AN INCREASE IN RAIN SHOWER COVERAGE LATE TONIGHT AND DAYTIME
WEDNESDAY AS THE LOW PRESSURE CENTER PASSES NORTHEASTWARD THROUGH
OHIO.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
BLEND OF RECENT MODELS SHOWS SCATTERED POST-SYSTEM SHOWERS
CONTINUING IN THE WAKE OF THE EXITING LOW PRESSURE WEDNESDAY NIGHT.
A SECOND LOW PRESSURE SYSTEM, COMING NORTHEAST FROM LOUISIANA,
WILL PROVIDE SHOWERS THURSDAY NIGHT AND FRIDAY.
SOUTHWEST WINDS ALOFT WILL ENSURE TEMPERATURES REMAINING MILDER
THAN NORMAL, AS INDICATED BY RECENT GFS AND NAM MOS. THIS MILDNESS
WILL PREVENT ANY CHANGE TO WINTRY TYPE PRECIPITATION THIS PERIOD.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
MODELS IN FAIRLY GOOD AGREEMENT WITH SERIES OF SHORT WAVES RUNNING
ALONG THE NORTHERN PERIPHERY OF SUBTROPICAL RIDGE SATURDAY.
PROBLEM IS HOW MUCH PHASING WILL OCCUR...AND HOW FAR NORTH
PRECIPITATION WILL COME AS SURFACE LOWS MOVE ALONG THE FRONT IN
THE MID ATLANTIC STATES.
DID NOT STRAY TOO FAR FROM HPC GRIDS WITH BEST CHANCES OF PRECIP
SATURDAY INTO SUNDAY CHRISTMAS DAY. THERE CAN BE SUFFICIENT COOL
DOWN TO PROVIDE A CHANCE OF MIXED RAIN AND SNOW SHOWERS SOUTH
WITH SNOW SHOWERS IN THE NORTH.
&&
.AVIATION /16Z TUESDAY THROUGH SATURDAY/...
PER RECENT SURFACE AND RADAR DATA, ALONG WITH HRRR MODEL OUTPUT,
FOR TAF SITES SOUTH OF KFKL AND KDUJ, EXPECT MVFR RAIN AND FOG WITH
SOME INTERLUDES OF IFR THROUGH 16Z. FOR KFKL AND KDUJ, THERE CAN
BE A PERIOD OF IFR SNOW AND FOG THROUGH 16Z.
WITH THE FRONT THEN RETREATING NORTHWARD THIS AFTERNOON, EXPECT
THE RAIN TO DECREASE IN COVERAGE INTO EARLY TONIGHT WITH FLIGHT
CONDITIONS MAINLY MVFR ALL LOCATIONS.
LOW PRESSURE CENTER MOVING NORTHEASTWARD FROM TEXAS TODAY THROUGH
OHIO WEDNESDAY, WILL PROVIDE FREQUENT RAIN SHOWERS LATE TONIGHT
AND DAYTIME WEDNESDAY. THIS WILL LIKELY CAUSE ADDITIONAL BOUTS OF
IFR RESTRICTIONS.
OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...
MVFR WEDNESDAY NIGHT IN LINGERING POST SYSTEM SHOWERS AND CLOUDS
CAN GIVE WAY TO VFR THURSDAY. THE POTENTIAL FOR RESTRICTIONS
THEN RETURNS WITH MIXED PRECIPITATION FRIDAY AND SATURDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
811 AM EST TUE DEC 20 2011
.SYNOPSIS...
A COLD FRONT STALLING ACROSS THE UPPER OHIO VALLEY WILL PROVIDE
RAIN TODAY. HOWEVER, THERE CAN BE A SHORT PERIOD OF WET SNOW THIS
MORNING NORTH OF PITTSBURGH. LOW PRESSURE, COMING NORTHEAST FROM TEXAS,
WILL BRING MILDER TEMPERATURES AND RAIN TONIGHT AND WEDNESDAY.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
UPDATED FOR MINOR ADJUSTMENTS TO WINDS THIS MORNING.
PER RECENT RADAR AND SURFACE DATA, COUPLED WITH RECENT HRRR AND
NAM MODEL OUTPUT, EXPECT PRECIPITATION ACROSS THE ENTIRE UPPER
OHIO VALLEY INTO MIDDAY. RECENT SURFACE DATA SHOWS LOW
VISIBILITIES ACROSS HIGHER TERRAIN WHICH CAN AFFECT TRAVEL ON
I-68 AND PA TURNPIKE.
THE COLD FRONT MOVING SLOWLY SOUTH FROM THE I-80 CORRIDOR MAY
LOWER SURFACE TEMPERATURES ENOUGH TO CAUSE A CHANGE TO WET SNOW
FOR A TIME THIS MORNING AS FAR SOUTH AS COLUMBIANA COUNTY OHIO,
BEAVER COUNTY, NORTHERN ALLEGHENY COUNTY AND NORTHERN INDIANA
COUNTY PENNSYLVANIA...ALSO ACROSS THE HIGHER MOUNTAIN RIDGES
FARTHER SOUTH. RAIN-WETTED GROUND SHOULD RESULT IN MINIMAL SNOW
ACCUMULATION, IF ANY.
WILL ISSUE STATEMENT REGARDING THE POSSIBILITY OF ICY CONDITIONS
WHERE TEMPERATURES REACH THE FREEZING POINT NEAR THE I-80
CORRIDOR. WILL ALSO ISSUE A STATEMENT MENTIONING LOW VISIBILITIES
IN FOG FOR HIGHER TERRAIN SOUTH.
EXPECT TEMPERATURES TO BEGIN SLOWLY WARMING LATER THIS MORNING, AS POSTFRONTAL
NORTH WINDS ABATE BEHIND THE STALLING COLD FRONT. THIS WILL
LIKEWISE ALLOW DAYTIME PROCESSES TO RAISE TEMPERATURES ALSO. HENCE
LOCATIONS WITH WET SNOW EARLY THIS MORNING SHOULD SEE IT END BY
MIDDAY. NAM MODEL OUTPUT SHOWS SOUTHEASTERLY WINDS INCREASE AHEAD
OF THE LOW PRESSURE CENTER INCOMING FROM TEXAS, CAUSING A SLOW
WARM UP INTO TONIGHT.
MODELS SHOW THERE MAY BE A BREAK IN THE RAIN SHOWERS EARLY TONIGHT, THEN
AN INCREASE IN RAIN SHOWER COVERAGE LATE TONIGHT AND DAYTIME
WEDNESDAY AS THE LOW PRESSURE CENTER PASSES NORTHEASTWARD THROUGH
OHIO.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
BLEND OF RECENT MODELS SHOWS SCATTERED POST-SYSTEM SHOWERS
CONTINUING IN THE WAKE OF THE EXITING LOW PRESSURE WEDNESDAY NIGHT.
A SECOND LOW PRESSURE SYSTEM, COMING NORTHEAST FROM LOUISIANA,
WILL PROVIDE SHOWERS THURSDAY NIGHT AND FRIDAY.
SOUTHWEST WINDS ALOFT WILL ENSURE TEMPERATURES REMAINING MILDER
THAN NORMAL, AS INDICATED BY RECENT GFS AND NAM MOS. THIS MILDNESS
WILL PREVENT ANY CHANGE TO WINTRY TYPE PRECIPITATION THIS PERIOD.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
MODELS IN FAIRLY GOOD AGREEMENT WITH SERIES OF SHORT WAVES RUNNING
ALONG THE NORTHERN PERIPHERY OF SUBTROPICAL RIDGE SATURDAY.
PROBLEM IS HOW MUCH PHASING WILL OCCUR...AND HOW FAR NORTH
PRECIPITATION WILL COME AS SURFACE LOWS MOVE ALONG THE FRONT IN
THE MID ATLANTIC STATES.
DID NOT STRAY TOO FAR FROM HPC GRIDS WITH BEST CHANCES OF PRECIP
SATURDAY INTO SUNDAY CHRISTMAS DAY. THERE CAN BE SUFFICIENT COOL
DOWN TO PROVIDE A CHANCE OF MIXED RAIN AND SNOW SHOWERS SOUTH
WITH SNOW SHOWERS IN THE NORTH.
&&
.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
PER RECENT SURFACE AND RADAR DATA, ALONG WITH HRRR MODEL OUTPUT,
FOR TAF SITES SOUTH OF KFKL AND KDUJ, EXPECT MVFR RAIN AND FOG WITH
SOME INTERLUDES OF IFR THROUGH 16Z. FOR KFKL AND KDUJ, THERE CAN
BE A PERIOD OF IFR SNOW AND FOG THROUGH 16Z.
WITH THE FRONT THEN RETREATING NORTHWARD THIS AFTERNOON, EXPECT
THE RAIN TO DECREASE IN COVERAGE INTO EARLY TONIGHT WITH FLIGHT
CONDITIONS MAINLY MVFR ALL LOCATIONS.
LOW PRESSURE CENTER MOVING NORTHEASTWARD FROM TEXAS TODAY THROUGH
OHIO WEDNESDAY, WILL PROVIDE FREQUENT RAIN SHOWERS LATE TONIGHT
AND DAYTIME WEDNESDAY. THIS WILL LIKELY CAUSE ADDITIONAL BOUTS OF
IFR RESTRICTIONS.
OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...
MVFR WEDNESDAY NIGHT IN LINGERING POST SYSTEM SHOWERS AND CLOUDS
CAN GIVE WAY TO VFR THURSDAY. THE POTENTIAL FOR RESTRICTIONS
THEN RETURNS WITH MIXED PRECIPITATION FRIDAY AND SATURDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
537 AM EST TUE DEC 20 2011
.SYNOPSIS...
A COLD FRONT STALLING ACROSS THE UPPER OHIO VALLEY WILL PROVIDE
RAIN TODAY. HOWEVER, THERE CAN BE A SHORT PERIOD OF WET SNOW THIS
MORNING NORTH OF PITTSBURGH. LOW PRESSURE, COMING NORTHEAST FROM TEXAS,
WILL BRING MILDER TEMPERATURES AND RAIN TONIGHT AND WEDNESDAY.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
UPDATED FORECAST TO ADD MENTION OF AREAS OF DENSE FOG ACROSS THE
WV-MD-SOUTHWEST PA MOUNTAINS INTO MID-MORNING.
PER RECENT RADAR AND SURFACE DATA, COUPLED WITH RECENT HRRR AND
NAM MODEL OUTPUT, EXPECT PRECIPITATION ACROSS THE ENTIRE UPPER
OHIO VALLEY INTO MIDDAY. RECENT SURFACE DATA SHOWS LOW
VISIBILITIES ACROSS HIGHER TERRAIN WHICH CAN AFFECT TRAVEL ON
I-68 AND PA TURNPIKE.
THE COLD FRONT MOVING SLOWLY SOUTH FROM THE I-80 CORRIDOR MAY
LOWER SURFACE TEMPERATURES ENOUGH TO CAUSE A CHANGE TO WET SNOW
FOR A TIME THIS MORNING AS FAR SOUTH AS COLUMBIANA COUNTY OHIO,
BEAVER COUNTY, NORTHERN ALLEGHENY COUNTY AND NORTHERN INDIANA
COUNTY PENNSYLVANIA...ALSO ACROSS THE HIGHER MOUNTAIN RIDGES
FARTHER SOUTH. RAIN-WETTED GROUND SHOULD RESULT IN MINIMAL SNOW
ACCUMULATION, IF ANY.
WILL ISSUE STATEMENT REGARDING THE POSSIBILITY OF ICY CONDITIONS
WHERE TEMPERATURES REACH THE FREEZING POINT NEAR THE I-80
CORRIDOR. WILL ALSO ISSUE A STATEMENT MENTIONING LOW VISIBILITIES
IN FOG FOR HIGHER TERRAIN SOUTH.
EXPECT TEMPERATURES TO BEGIN SLOWLY WARMING LATER THIS MORNING, AS POSTFRONTAL
NORTH WINDS ABATE BEHIND THE STALLING COLD FRONT. THIS WILL
LIKEWISE ALLOW DAYTIME PROCESSES TO RAISE TEMPERATURES ALSO. HENCE
LOCATIONS WITH WET SNOW EARLY THIS MORNING SHOULD SEE IT END BY
MIDDAY. NAM MODEL OUTPUT SHOWS SOUTHEASTERLY WINDS INCREASE AHEAD
OF THE LOW PRESSURE CENTER INCOMING FROM TEXAS, CAUSING A SLOW
WARM UP INTO TONIGHT.
MODELS SHOW THERE MAY BE A BREAK IN THE RAIN SHOWERS EARLY TONIGHT, THEN
AN INCREASE IN RAIN SHOWER COVERAGE LATE TONIGHT AND DAYTIME
WEDNESDAY AS THE LOW PRESSURE CENTER PASSES NORTHEASTWARD THROUGH
OHIO.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
BLEND OF RECENT MODELS SHOWS SCATTERED POST-SYSTEM SHOWERS
CONTINUING IN THE WAKE OF THE EXITING LOW PRESSURE WEDNESDAY NIGHT.
A SECOND LOW PRESSURE SYSTEM, COMING NORTHEAST FROM LOUISIANA,
WILL PROVIDE SHOWERS THURSDAY NIGHT AND FRIDAY.
SOUTHWEST WINDS ALOFT WILL ENSURE TEMPERATURES REMAINING MILDER
THAN NORMAL, AS INDICATED BY RECENT GFS AND NAM MOS. THIS MILDNESS
WILL PREVENT ANY CHANGE TO WINTRY TYPE PRECIPITATION THIS PERIOD.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
MODELS IN FAIRLY GOOD AGREEMENT WITH SERIES OF SHORT WAVES RUNNING
ALONG THE NORTHERN PERIPHERY OF SUBTROPICAL RIDGE SATURDAY.
PROBLEM IS HOW MUCH PHASING WILL OCCUR...AND HOW FAR NORTH
PRECIPITATION WILL COME AS SURFACE LOWS MOVE ALONG THE FRONT IN
THE MID ATLANTIC STATES.
DID NOT STRAY TOO FAR FROM HPC GRIDS WITH BEST CHANCES OF PRECIP
SATURDAY INTO SUNDAY CHRISTMAS DAY. THERE CAN BE SUFFICIENT COOL
DOWN TO PROVIDE A CHANCE OF MIXED RAIN AND SNOW SHOWERS SOUTH
WITH SNOW SHOWERS IN THE NORTH.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
PER RECENT SURFACE AND RADAR DATA, ALONG WITH HRRR MODEL OUTPUT,
FOR TAF SITES SOUTH OF KFKL AND KDUJ, EXPECT MVFR RAIN AND FOG WITH
SOME INTERLUDES OF IFR THROUGH 16Z. FOR KFKL AND KDUJ, THERE CAN
BE A PERIOD OF IFR SNOW AND FOG THROUGH 16Z.
WITH THE FRONT THEN RETREATING NORTHWARD THIS AFTERNOON, EXPECT
THE RAIN TO DECREASE IN COVERAGE INTO EARLY TONIGHT WITH FLIGHT
CONDITIONS MAINLY MVFR ALL LOCATIONS.
LOW PRESSURE CENTER MOVING NORTHEASTWARD FROM TEXAS TODAY THROUGH
OHIO WEDNESDAY, WILL PROVIDE FREQUENT RAIN SHOWERS LATE TONIGHT
AND DAYTIME WEDNESDAY. THIS WILL LIKELY CAUSE ADDITIONAL BOUTS OF
IFR RESTRICTIONS.
OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...
MVFR WEDNESDAY NIGHT IN LINGERING POST SYSTEM SHOWERS AND CLOUDS
CAN GIVE WAY TO VFR THURSDAY. THE POTENTIAL FOR RESTRICTIONS
THEN RETURNS WITH MIXED PRECIPITATION FRIDAY AND SATURDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
516 AM EST TUE DEC 20 2011
.SYNOPSIS...
A COLD FRONT STALLING ACROSS THE UPPER OHIO VALLEY WILL PROVIDE
RAIN TODAY. HOWEVER, THERE CAN BE A SHORT PERIOD OF WET SNOW THIS
MORNING NORTH OF PITTSBURGH. LOW PRESSURE, COMING NORTHEAST FROM TEXAS,
WILL BRING MILDER TEMPERATURES AND RAIN TONIGHT AND WEDNESDAY.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
PER RECENT RADAR AND SURFACE DATA, COUPLED WITH RECENT HRRR AND
NAM MODEL OUTPUT, EXPECT PRECIPITATION ACROSS THE ENTIRE UPPER
OHIO VALLEY INTO MIDDAY.
THE COLD FRONT MOVING SLOWLY SOUTH FROM THE I-80 CORRIDOR MAY
LOWER SURFACE TEMPERATURES ENOUGH TO CAUSE A CHANGE TO WET SNOW
FOR A TIME THIS MORNING AS FAR SOUTH AS COLUMBIANA COUNTY OHIO,
BEAVER COUNTY, NORTHERN ALLEGHENY COUNTY AND NORTHERN INDIANA
COUNTY PENNSYLVANIA...ALSO ACROSS THE HIGHER MOUNTAIN RIDGES
FARTHER SOUTH. RAIN-WETTED GROUND SHOULD RESULT IN MINIMAL SNOW
ACCUMULATION, IF ANY.
WILL ISSUE STATEMENT REGARDING THE POSSIBILITY OF ICY CONDITIONS
WHERE TEMPERATURES REACH THE FREEZING POINT NEAR THE I-80
CORRIDOR.
EXPECT TEMPERATURES TO BEGIN SLOWLY WARMING LATER THIS MORNING, AS POSTFRONTAL
NORTH WINDS ABATE BEHIND THE STALLING COLD FRONT. THIS WILL
LIKEWISE ALLOW DAYTIME PROCESSES TO RAISE TEMPERATURES ALSO. HENCE
LOCATIONS WITH WET SNOW EARLY THIS MORNING SHOULD SEE IT END BY
MIDDAY. NAM MODEL OUTPUT SHOWS SOUTHEASTERLY WINDS INCREASE AHEAD
OF THE LOW PRESSURE CENTER INCOMING FROM TEXAS, CAUSING A SLOW
WARM UP INTO TONIGHT.
MODELS SHOW THERE MAY BE A BREAK IN THE RAIN SHOWERS EARLY TONIGHT, THEN
AN INCREASE IN RAIN SHOWER COVERAGE LATE TONIGHT AND DAYTIME
WEDNESDAY AS THE LOW PRESSURE CENTER PASSES NORTHEASTWARD THROUGH
OHIO.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
BLEND OF RECENT MODELS SHOWS SCATTERED POST-SYSTEM SHOWERS
CONTINUING IN THE WAKE OF THE EXITING LOW PRESSURE WEDNESDAY NIGHT.
A SECOND LOW PRESSURE SYSTEM, COMING NORTHEAST FROM LOUISIANA,
WILL PROVIDE SHOWERS THURSDAY NIGHT AND FRIDAY.
SOUTHWEST WINDS ALOFT WILL ENSURE TEMPERATURES REMAINING MILDER
THAN NORMAL, AS INDICATED BY RECENT GFS AND NAM MOS. THIS MILDNESS
WILL PREVENT ANY CHANGE TO WINTRY TYPE PRECIPITATION THIS PERIOD.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
MODELS IN FAIRLY GOOD AGREEMENT WITH SERIES OF SHORT WAVES RUNNING
ALONG THE NORTHERN PERIPHERY OF SUBTROPICAL RIDGE SATURDAY.
PROBLEM IS HOW MUCH PHASING WILL OCCUR...AND HOW FAR NORTH
PRECIPITATION WILL COME AS SURFACE LOWS MOVE ALONG THE FRONT IN
THE MID ATLANTIC STATES.
DID NOT STRAY TOO FAR FROM HPC GRIDS WITH BEST CHANCES OF PRECIP
SATURDAY INTO SUNDAY CHRISTMAS DAY. THERE CAN BE SUFFICIENT COOL
DOWN TO PROVIDE A CHANCE OF MIXED RAIN AND SNOW SHOWERS SOUTH
WITH SNOW SHOWERS IN THE NORTH.
&&
.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
PER RECENT SURFACE AND RADAR DATA, ALONG WITH HRRR MODEL OUTPUT,
FOR TAF SITES SOUTH OF KFKL AND KDUJ, EXPECT MVFR RAIN AND FOG WITH
SOME INTERLUDES OF IFR THROUGH 16Z. FOR KFKL AND KDUJ, THERE CAN
BE A PERIOD OF IFR SNOW AND FOG THROUGH 16Z.
WITH THE FRONT THEN RETREATING NORTHWARD THIS AFTERNOON, EXPECT
THE RAIN TO DECREASE IN COVERAGE INTO EARLY TONIGHT WITH FLIGHT
CONDITIONS MAINLY MVFR ALL LOCATIONS.
LOW PRESSURE CENTER MOVING NORTHEASTWARD FROM TEXAS TODAY THROUGH
OHIO WEDNESDAY, WILL PROVIDE FREQUENT RAIN SHOWERS LATE TONIGHT
AND DAYTIME WEDNESDAY. THIS WILL LIKELY CAUSE ADDITIONAL BOUTS OF
IFR RESTRICTIONS.
OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...
MVFR WEDNESDAY NIGHT IN LINGERING POST SYSTEM SHOWERS AND CLOUDS
CAN GIVE WAY TO VFR THURSDAY. THE POTENTIAL FOR RESTRICTIONS
THEN RETURNS WITH MIXED PRECIPITATION FRIDAY AND SATURDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
630 AM EST TUE DEC 20 2011
UPDATED AVIATION DISCUSSION FOR THE 12Z TAFS
.DISCUSSION /TODAY THROUGH MONDAY/... ISSUED AT 411 AM EST
UPPER TROUGH EXITING THE AREA THIS MORNING...PLACING THE AREA UNDER
MORE ZONAL FLOW THROUGH TONIGHT. AT THE SFC...LOW MOVING THROUGH
HUDSON BAY TODAY WILL PUSH A COLD FRONT THROUGH SRN CANADA.
INCREASING GRADIENT AHEAD OF THE FRONT WILL INCREASE WSW WINDS OVER
THE CWA...ESPECIALLY OVER WRN LK SUPERIOR. H925 WINDS /JUST BELOW
THE INVERSION/ SHOULD INCREASE TO 35-40KTS OVER WRN LK SUPERIOR AND
25-30KTS OVER MUCH OF THE CWA. WITH EXPECTED MIXING TOWARDS THAT
LEVEL THIS AFTN WITH MORE SUN...WILL BE BREEZY AT TIMES THIS AFTN
WITH GUSTS TO 25-30MPH...ESPECIALLY NEAR LK SUPERIOR.
PESKY LOW CLOUDS WILL BE THE SHORT TERM FCST CONCERN...AS MODELS
CONTINUE TO STRUGGLE EVEN ACKNOWLEDGING CLOUDS BEING PRESENT. THE
INCREASING H925 WINDS SHOULD HELP PUSH THE LOW CLOUDS NE AND ALSO
AID IN MIXING INTO DRIER AIR ALOFT AND FROM THE WSW. DOWNSLOPING SW
WINDS ALREADY STARTING TO BREAK UP CLOUDS OVER NCNTRL UPPER MI AND
EXPECT THAT TO CONTINUE INTO THE MORNING. RUC STILL LOOKS TO HAVE
THE BEST HANDLE ON THE CLOUDS...AND 06Z RUNS HAVE IT DIMINISHING BY
MID DAY. LLVL WINDS OFF COOLER LK MI WILL LIKELY KEEP CLOUDS HANGING
ON LONGER OVER THE E. IN ADDITION...WITH H850 TEMPS AROUND -9C
CREATING DELTA-T VALUES OF 16 OVER LK MI WILL KEEP LK ENHANCED
CLOUDS OVER FAR SE LUCE/SCHOOLCRAFT COUNTIES THROUGH MUCH OF THE
DAY.
ONCE THE CLOUDS EXIT THE AREA...SHOULD BE A NICE LATE DECEMBER AFTN
WITH PARTLY/MOSTLY SUNNY SKIES /ALTHOUGH A FEW MID CLOUDS COULD PUSH
SE OVER NRN LK SUPERIOR AND AFFECT THE KEWEENAW/ AND HIGHS IN THE
UPPER 20S AND LOWER 30S.
UPPER LOW ASSOCIATED WITH STRONG WINTER STORM IN THE LEE OF THE
CNTRL/SRN ROCKIES WILL SHIFT NE TONIGHT AND MOVE THROUGH THE LOWER
GREAT LAKES ON WED INTO WED NIGHT. WITH THIS SYSTEM PUSHING NE AND
SFC FRONT SLOWLY DROPPING SE THROUGH CANADA AND TOWARDS THE U.S.
BORDER...EXPECT A PORTION OF THE AREA TO BE UNDER THE PINCHED DRY
AIR BETWEEN THE SYSTEMS. LATEST TRENDS IN THE MODELS PUT THIS MORE
OVER THE SE CWA TONIGHT...WHILE THE NW HALF IS UNDER THE INCREASING
CLOUDS WITH THE APPROACHING SFC TROUGH. EXPECT THE CLOUDS TO
CONTINUE SE SLOWLY DURING THE DAY ON WED AS THE SFC TROUGH CONTINUES
IT/S SE PUSH.
PCPN CHANCES INCREASE AS THE SFC TROUGH PUSHES THROUGH LATE WED
NIGHT AND CHANCES WILL CONTINUE ON THURS AS LES DEVELOPS. H850 TEMPS
SHOULD FALL FROM -7C AT 06Z THURS TO -13C AT 18Z AND PUSH DELTA-T
VALUES TOWARDS 17. AS THE COLDER AIR ARRIVES...DEEPER MOISTURE EXITS
AND H850-700 SUBSIDENCE INCREASES /ESPECIALLY IN THE AFTN/...WHICH
CAUSES INVERSION HEIGHTS TO FALL TOWARDS 3-4KFT. THUS...POTENTIAL
FOR MUCH MORE THAT A INCH OR TWO OF LES IS LIMITED ON THURS. DID
BUMP POPS UP SOME FOR THURS FOR THE NNW WIND LOCATIONS...BUT STILL
ONLY PEAKED IT OUT IN THE MID-UPPER CHANCE AREA. ALSO BUMPED UP POPS
SOME FOR THURS NIGHT...TO CHANCES OVER THE E...SINCE LES WILL LIKELY
BE ONGOING AND BEST MOISTURE LOOKS TO BE THERE. WRN CWA IS A LITTLE
MORE UNCERTAIN WITH SFC RIDGE AND DRYING ARRIVING THROUGH THE NIGHT.
WILL GO WITH SLIGHTS FOR MOST OF THE N WIND FAVORED
LOCATIONS...THOUGH WILL GO WITH SOME CHANCES IN THE EVENING OVER THE
HIGHER TERRAIN LOCATIONS.
UPPER TROUGH IN THE NRN STREAM WILL DROP SE OUT OF THE CANADIAN
ROCKIES ON WED AND THROUGH THE UPPER GREAT LAKES THURS THROUGH FRI.
STILL SOME DIFFERENCES IN THE MODELS ON POTENTIALLY CLOSING OFF THE
SRN EXTENT OF THE UPPER TROUGH OVER THE CNTRL PLAINS FRI...WHICH
WOULD ALLOW WEAK UPPER RIDGING TO MOVE INTO THE WRN GREAT LKS
EARLIER ON FRI NIGHT AND CONTINUE INTO SAT. EITHER WAY...CWA WILL
LIKELY BE BETWEEN SYSTEMS AND HAVE SFC HIGH OVER THE AREA FRI NIGHT
INTO SAT.
EXPECT LINGERING LES TO DIMINISH AND PUSH OFFSHORE OVER THE ERN CWA
ON FRI...AS H850 WAA PUSHES TEMPS TOWARDS -8C AND LLVL WINDS BACK TO
THE WSW. AT THE SAME TIME SHORTWAVE MOVING THROUGH THE NRN STREAM IN
CNTRL/NRN ONTARIO SHOULD ONLY BRUSH HIGH CLOUDS OVER NRN LK
SUPERIOR...ALTHOUGH 00Z GFS/GEM HAS TRENDED FARTHER S WITH WITH WAVE
AND BRUSHES PCPN OVER NRN LK SUPERIOR. SWRLY FLOW AND DRY AIR ALOFT
SHOULD KEEP TEMPS IN CHECK WITH CLEAR SKIES ON FRI NIGHT AND WILL GO
WITH ABOVE NORMAL LOWS. DRY AIR ABOVE THE STRONG INVERSION AROUND
H925 SHOULD KEEP SKIES MOSTLY SUNNY ON SAT OTHER THAN SOME PASSING
HIGH CLOUDS. TEMPS ARE UNCERTAIN THIS FAR OUT AND WILL LEAN TOWARDS
A CONSENSUS FOR HIGHS. THAT BEING SAID...CLEAR SKIES AND SW WINDS
FAVOR WARMER TEMPS IN DOWNSLOPE AREAS NEAR LK SUPERIOR...SO DID
ADJUST THOSE AREAS UP A FEW DEGREES.
NRN STREAM TROUGH IS STILL SHOWN ON THE EXTENDED MODELS TO AFFECT
THE AREA SUN INTO MON. SFC TROUGH ASSOCIATED WITH LOW MOVING THROUGH
HUDSON BAY SHOULD DRAG A SFC TROUGH ACROSS THE CWA SAT NIGHT OR SUN
/12Z ECMWF AND 00Z GEM ARE THE FASTER SOLNS/. AS HAS BEEN THE CASE
WITH THE SERIES OF NRN STREAM WAVES...MOISTURE/FORCING ALONG THE
FRONT APPEARS TO BE LIMITED SO WILL CONTINUE SLIGHTS/LOW CHANCES
WITH THE FRONTAL PASSAGE. H850 TEMPS AROUND -15C AND POST FRONTAL
LLVL MOISTURE SHOULD LEAD TO LES IN NW WIND FAVORED LOCATIONS SUN
AND BUMPED UP POPS FROM THE CONSENSUS AND WILL CONTINUE CHANCE POPS
THROUGH SUN NIGHT. 00Z GFS SOUNDINGS WOULD SUPPORT A CHANCE OF
SEEING AT LEAST FEW INCHES OF SNOW ACCUMULATIONS NNW SNOWBELTS FOR
XMAS AFTN/EVENING. ECMWF ON THE OTHERHAND QUICKLY PULLS DRIER AIR
INTO THE REGION SUN AFTN/NIGHT WITH THE ARRIVAL OF THE SFC RIDGE.
ANOTHER NRN STREAM SHORTWAVE WAVE LOOKS TO BRUSH LK SUPERIOR ON
MN...BUT WITH OVERALL WEAK WAVE AND LIMITED MOISTURE WILL ONLY GO
SLIGHT POPS.
&&
.AVIATION /FOR THE 12Z TAF ISSUANCE/...
MVFR CIGS CONTINUE TO HANG ON LONGER THAN SUGGESTED BY GUIDANCE.
WITH SFC HIGH PRES RIDGE AXIS SLIPPING SE OF THE AREA...RESULTING IN
INCREASING SW WINDS...EXPECT LOWER CLOUDS TO CLEAR OUT BTWN MID
MORNING AND EARLY AFTN PER TRENDS NOTED ON SATELLITE IMAGERY. VFR
CONDITIONS WILL THEN PERSIST THRU THE END OF THIS FCST PERIOD.
TIGHTENING PRES GRADIENT TODAY WILL RESULT IN GUSTY WINDS TO AROUND
25KT. LLWS MAY DEVELOP THIS EVENING DEPENDING ON DEGREE OF
DECOUPLING THAT OCCURS. RIGHT NOW...EXPECT WINDS TO RETAIN SOME
GUSTINESS THRU THE EVENING.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
DEEP LOW PRES MOVING E TO HUDSON BAY WILL BRING ANOTHER ROUND OF SW
GALES TO MUCH OF LAKE SUPERIOR TODAY THRU THIS EVENING. SW WIND
DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND ISLE ROYALE FOR
STRONGEST WINDS (GUSTS TO 40-45KT). GALES WILL END LATER TONIGHT
AS PRES GRADIENT WEAKENS. WINDS WILL BE BLO 25KT WED THRU FRI THOUGH
THERE MAY BE A PERIOD OF 20-30KT WINDS OVER CNTRL LAKE SUPERIOR THU
MORNING IN THE WAKE OF A PASSING COLD FRONT. ANOTHER LOW PRES SYSTEM
TRACKING E TO HUDSON BAY COULD BRING A PERIOD OF SW WINDS UP TO 30KT
OVER PORTIONS OF WEST AND NCNTRL LAKE SUPERIOR LATE FRI NIGHT INTO
SAT.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...
GALE WARNING FROM 1 PM THIS AFTERNOON TO 1 AM EST WEDNESDAY FOR
LSZ267.
GALE WARNING FROM 9 AM THIS MORNING TO 1 AM EST WEDNESDAY FOR
LSZ266.
GALE WARNING UNTIL MIDNIGHT EST /11 PM CST/ TONIGHT FOR LSZ162.
GALE WARNING UNTIL 3 AM EST WEDNESDAY FOR LSZ263-264.
LAKE MICHIGAN...NONE.
&&
$$
DISCUSSION...SRF
AVIATION...ROLFSON
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
510 AM CST Tue Dec 20 2011
...UPDATED AVIATION DISCUSSION...
.DISCUSSION...
In the short term a classic panhandle low continues to accomplish
what it often does for this portion of the region, that is, sending
copious amount of moisture northward and creating a headache for
winter precipitation forecasts.
Early this morning, expansive dry slot is now rapidly lifting
northeast and across eastern Kansas and western Missouri. With
satellite imagery indicating the loss of ice crystals we`re also slowly
losing much of our precipitation across the region. However, during
the past 18 hours extensive northward moisture transport resulting in
PWAT values nearly 1" (or within the 99th percentile for this time of
the year) and efficient rain processes have produced near record
rainfall in the local area. The result of nearly 1-1.5" of rain will
be the flooding of several rivers in central Missouri. Further north,
a more problematic forecast persists as a tight moisture gradient has
formed over extreme northern Missouri thanks to Canadian high
pressure over the Dakotas and strong dry air advection behind a
departing northern stream trough in the Western Great Lakes. 00z
OAX/DVN soundings confirmed the extent of this moisture disparity,
which is resulting in a overall lack of precipitation reaching the
ground despite the extensive areal coverage of radar echoes. Thus,
snowfall totals have been severely hampered over NE Kansas and NW
Missouri with isolated totals of a half inch in some locations.
For today, following much of the guidance from the suite of
mesoscale models which have a reasonable handle on the current
situation. The 00z NMM, 06z NAM, and RUC are the most reasonable
solutions at this time. As dry slot rotates through the area, precip
will continue to diminish through 15z, with lingering activity
mainly in the northern zones. Soundings continue to support a mix of
snow/sleet and perhaps rain in and along the Highway 36 corridor.
Given the absence of ice crystals would also be concerned for a bit
of freezing drizzle. By the middle to late morning hours, we should
also begin to see the expansive deformation zone in southwestern
Kansas begin to lift northeast towards the area. However, as the
upper low begins to eject eastward, support for heavy precipitation
will diminish as in tandem the favorable upper jet streak and rich
moisture feed both shift eastward. Feel model qpf may be a bit too
high given the lack of ice aloft, but soundings similar to these have
produced periods of light rain/drizzle/sleet or even snow showers
before, just usually very light in nature. The best chance for any
wintry precip will remain in the northwestern third of the CWA with
little accumulation. Further south would expect more drizzle or light
rain showers than anything. Will continue with the advisory for now
given potential for some development, but feel impacts may be much
lower than earlier thought.
Tonight, as mentioned in previous discussion, models continue to
hint at an area of low static stability most likely tied to an
individual vort lobe rotating around the upper low. Mesoscale model
output remains consistent in bringing a pocket of strong omega,
non-coincident with the aforementioned deformation zone, through
southern Kansas and into portions of central Missouri. Soundings and
cross sections through this layer suggest that with rather high
freezing levels, would expect mainly a patch of light to moderate
rain showers. Would also not be surprised to see a rumble or two of
thunder, but confidence not high enough to include. It is
theoretically possible that there could be enough dynamical cooling
within this locally intensifying vort lobe to produce a very quick
batch of heavy snow. Once again, not a certain forecast at all. Of
more concern is the potential that if roads and paved surfaces cannot
dry out by nighttime as colder air arrives, a period of black ice may
be possible heading into Wednesday morning.
Wednesday: The region will quickly transition to a zonal or
southwest flow pattern aloft for Wednesday as energy again digs into
the southwestern United States. Given the lack of snowcover except
in the NW CWA and modest southwest low level flow have bumped up
high temperatures a category or two in most locations.
For Thursday: Secondary upper trough emanating out of the Southwest
will quickly race into the region on Thursday. The southerly track
of this wave will hold moisture well south of the CWA with a weak
surface ridge axis bisecting the area.
31
Thursday through Tuesday...
Models have been trending toward a slightly stronger system for
Thursday night and Friday. However, there is still some difficulty
with respect to interactions between the Northern Plains shortwave
trough. Regardless, since moisture is limited will keep the threat
of snow in the low chance category. Otherwise, for the rest of the
period, it will remain rather quiet with only weak shortwaves in
basically dry northwest upper flow.
DB
&&
.AVIATION...
For the 12Z tafs, much of the precipitation associated with the
strong isentropic lift has shifted east this morning. However, weak isentropic
lift ahead of the upper level storm system in Oklahoma will continue
to produce drizzle and patches of light rain. This will aid in
keeping ceilings in the LIFR category with MVFR visibilities today.
Little change is expected tonight as the upper level storm system
produces patches of light rain and snow. Any accumulation of snow is
expected to be below an inch.
DB
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER WEATHER ADVISORY until 6 PM CST this evening FOR
MOZ001>005-011>014-020>022.
KS...WINTER WEATHER ADVISORY until 6 PM CST this evening FOR KSZ025-
102.
&&
$$
WFO EAX
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
649 AM EST TUE DEC 20 2011
.SYNOPSIS...
HIGH PRESSURE LOCATED OVER THE GREAT LAKES WILL MOVE TOWARD THE
NORTH COUNTRY TODAY. THIS WILL PROVIDE OUR REGION WITH INCREASING
AMOUNTS OF SUNSHINE...ALONG WITH COOL NORTHERLY WINDS. TEMPERATURES
WILL HOLD IN THE UPPER TEENS IN THE MOUNTAINS TO THE MID TO UPPER
20S IN THE VALLEYS. THE NEXT STORM SYSTEM WILL IMPACT THE REGION
WEDNESDAY INTO THURSDAY...WITH MIXED PRECIPITATION QUICKLY
CHANGING TO A COLD RAIN. TEMPERATURES WILL WARM BACK INTO THE 30S
TO NEAR 40 IN MANY LOCATIONS ON WEDNESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 600 AM EST TUESDAY...SEVERAL CHANGES TO CRNT FCST BASED ON IR
SATL PICS AND LATEST TEMPS. SFC COLD FRNT HAS PUSHED INTO SOUTHERN
NEW ENGLAND THIS MORNING WHILE LLVL CAA CONTS. THIS HAS RESULTED
IN A TIGHT NORTH TO SOUTH THERMAL GRADIENT ACRS OUR CWA...ALONG
WITH A WIDE RANGE IN TEMPS. TEMPS RANGE FROM THE M/U TEENS ACRS
NNY TO 35F AT VSF. WL UPDATE WITH CRNT TEMPS ATTM AND INCREASE
DAYTIME HIGHS BY SEVERAL DEGREES ACRS CENTRAL/SOUTHERN VT. IN
ADDITION...LATEST RUC13 SHOWS PLENTY OF LLVL MOISTURE RESULTING IN
LOTS OF CLOUDS ACRS OUR CWA. HAVE INCREASED CLOUDS ACRS MOST OF
THE REGION...BUT EXPECT AREAL COVERAGE TO DECREASE BY 15Z TODAY.
REST OF FCST IN GOOD SHAPE.
WATER VAPOR SHOWS WELL DEFINED SHORT WAVE QUICKLY MOVING
SOUTHEAST OF OUR CWA THIS MORNING ASSOCIATED WITH SFC COLD
FRNT...WHILE AREA OF SUBSIDENCE/DRY AIR ALOFT ADVECTS INTO OUR
REGION. THIS COMBINED WITH SFC HIGH PRES OVERHEAD BY 18Z
TODAY...WL RESULT IN CLRING SKIES AND PLENTY OF SUNSHINE. THE
COMBINATION OF LEFTOVER MOISTURE AND SOME WEAK UPSLOPE FLW THIS
MORNING MAY PRODUCE A FEW FLURRIES AND CLOUDS ACRS THE MTNS. TEMPS
WL BE TRICKY WITH SHARP THERMAL GRADIENT AND ASSOCIATED CAA ACRS
OUR CWA TODAY. THINKING U10S MTNS/SLK TO NEAR L30S VSF...WITH MANY
AREAS HOLDING IN THE M/U 20S.
TONIGHT...SFC HIGH PRES QUICKLY SHIFTS OFF THE MID ATLANTIC COAST
WITH A RETURN SOUTHERLY FLW DEVELOPING. THIS RESULTS IN SIGNIFICANT
WARMING OF THE LLVLS WITH 850MB TEMPS NEAR 0C BY 12Z WEDS ACRS OUR
SOUTHERN ZNS. THE COMBINATION OF WAA...INCREASING CLOUDS...AND
DEVELOPING SOUTHERLY FLW WL MAKE FOR A CHALLENGING LOW TEMP FCST.
THINKING COLDEST TEMPS WL BE ACRS THE NEK/EASTERN VT WITH LOWS IN
THE LOWER TEENS TO NEAR 20F CPV/SLV. ONCE AGAIN EXPECT LOWS TO BE
BEFORE MIDNIGHT WITH TEMPS RISING TWD MORNING. WL CONT TO MENTION
SCHC/CHC POPS ALONG AND SOUTH OF A MSS TO SLK TO MPV LINE BTWN
09Z-12Z WEDS...ASSOCIATED WITH WAA LIFT/MOISTURE. OVERALL QPF
AMOUNTS WL BE VERY LIGHT...WITH MOST OF THE PRECIP EVAPORATING
BEFORE REACHING THE GROUND...DUE TO VERY DEEP DRY AIR AHEAD OF
MOISTURE/LIFT. THERMAL PROFILES SUPPORT ALL SNOW THRU 12Z
WEDS...WITH ONLY A DUSTING OF ACCUMULATIONS ANTICIPATED.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 415 AM EST TUESDAY...FCST FOCUS WL BE PRECIP EVENT WEDS
INTO THURS...ASSOCIATED WITH SOUTHERN PLAINS SYSTEM. ONCE AGAIN A
MAINLY COLD RAIN EVENT IS ANTICIPATED WITH QPF AMOUNTS BTWN 0.10
FOR THE CPV TO 0.40" FOR THE DACKS AND PARTS OF THE SOUTHERN GREEN
MTNS. SEVERAL PERIODS OF MAINLY LIGHT RAIN IS ANTICIPATED...WITH
BEST DEEP LAYER LIFT/MOISTURE BEING ACRS CENTRAL/SOUTHERN VT.
FIRST SURGE OF 850 TO 500MB MOISTURE AND 700 TO 500MB LIFT WL MOVE
FROM SOUTHWEST TO NORTHEAST ACRS OUR CWA BTWN 12Z-15Z WEDS.
THERMAL PROFILES SUPPORT A MIX OF SNOW...SLEET...AND FREEZING
RAIN...ESPECIALLY EAST OF THE GREEN MTNS...BUT TOTAL QPF AMOUNTS
ASSOCIATED WITH INITIAL BAND OF PRECIP WL BE LIGHT AND ONLY A
DUSTING OF SNOW/SLEET IS ANTICIPATED. LOW LEVEL SOUTH TO SOUTHWEST
FLW WL QUICKLY ADVECT WARMER TEMPS ACRS OUR CWA BY 15Z WEDS...WITH
85H TEMPS RISING BTWN +3C AND +5C...AND 925MB TEMPS NEAR +3C. IN
ADDITION...GIVEN POSITION OF SFC HIGH PRES WITH NO BLOCKING
SIGNATURE IN THE SLP FIELDS...FEEL COLD AIR WL QUICKLY RETREAT.
ALSO...LIMITED SNOW PACK AND DEVELOPING SOUTHERLY FLW WL HELP TO
ERODE LLVL COLD AIR...BEFORE HEAVIER PRECIP ARRIVES AFT 18Z WEDS.
THE BETTER DYNAMICS ASSOCIATED WITH DECAYING MID/UPPER LVL
CIRCULATION AND POTENT 5H VORT MOVES ACRS OUR CWA BTWN 21Z-06Z.
THIS ULVL SUPPORT COMBINED WITH GOOD 850 TO 500MB Q-VECTOR
CONVERGENCE AND GOOD AVAILABLE MOISTURE WITH PWS APPROACHING
0.75"...WL RESULT IN A PERIOD OF OCCASIONAL LIGHT RAIN ACRS OUR
CWA ON WEDS NIGHT. ONCE AGAIN...A FEW POCKETS OF FREEZING RAIN WL
BE POSSIBLE ACRS EASTERN VT/NEK...BUT NOT ANTICIPATING ANY ICE
ACCUMULATION ATTM. TEMPS WL WARM INTO THE L40S CPV TO M30S
NEK/EASTERN VT ON WEDS. LITTLE CHANGE IN TEMPS IS EXPECTED ON WEDS
NIGHT WITH CLOUDS AND PRECIP EXPECTED. SFC COLD FRNT APPROACHES
NORTHERN CWA BY 12Z THURS...WITH TIGHT THERMAL GRADIENT. THIS WL
PUSH ACRS OUR FA ON THURS...WITH COOLER TEMPS AND THE CHANCE FOR
RAIN/SNOW SHOWERS. UNFORTUNATELY...AS THE AIR BECMS COLD ENOUGH TO
SUPPORT SNOW...THE BEST MOISTURE MOVES TO OUR EAST. NOT
ANTICIPATING MUCH SNOW ACCUMULATION...MAYBE AN INCH OR SO IN THE
FAVORABLE UPSLOPE REGIONS OF THE DACKS/GREEN MTNS. TEMPS WL START
NEAR 40F IN THE CPV...BUT WL FALL INTO THE 30S AS NORTH WINDS AND
LLVL CAA DEVELOPS. OTHERWISE...MAINLY 30S WL BE THE HIGHS ON THURS
ACRS THE MTNS.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 230 PM EST MONDAY...DEVELOPING COLD FRONT NORTH OF THE
INTERNATIONAL BORDER WILL DROP SOUTH INTO FORECAST LATER THURSDAY
NIGHT. MEANWHILE...LOW PRESSURE WILL TRACK SOUTH OF THE AREA PASSING
OFF MID ATLANTIC COAST. EXPECT SOME SNOW SHOWERS ASSOCIATED WITH
COLD FRONT TO AFFECT NORTHERN ZONES...WITH LIGHT SNOW ASSOCIATED
WITH LOW TO OUR SOUTH POSSIBLY AFFECTING SOUTHERN ZONES. ALL ADDS
UP TO CHANCE POPS...MAINLY AFTER MIDNIGHT. LOW DEPARTS OFFSHORE FRIDAY
MORNING...BUT THERE WILL BE A CONTINUED CHANCE FOR A FEW SNOW SHOWERS
AS THE COLD FRONT DEPRESSES SOUTH OF FORECAST AREA BY AFTERNOON.
HIGH PRESSURE BUILDING ACROSS ONTARIO INTO QUEBEC LATER FRIDAY
INTO SATURDAY WILL BRING MAINLY DRY WEATHER TO THE NORTH COUNTRY
ALONG WITH COLDER TEMPERATURES. LOWS FRIDAY NIGHT UNDER MAINLY CLEAR
SKIES WILL BE MAINLY IN THE TEENS...AND HIGHS ON SATURDAY IN THE
UPPER 20S TO LOWER 30S.
SITUATION BECOMES MORE COMPLICATED SATURDAY NIGHT AS HIGH MOVES
INTO EASTERN CANADA AND SHORTWAVE AND ASSOCIATED SURFACE LOW LIFT
NORTHEAST FROM THE TENNESSEE VALLEY. SOME RATHER SIGNIFICANT
DIFFERENCES BETWEEN GFS AND ECMWF REGARDING THIS SYSTEM...
ESPECIALLY WITH RESPECT TO TIMING. GFS MUCH FASTER...BRINGING
PRECIPITATION IN QUICKLY SATURDAY NIGHT AND EXITING CHRISTMAS
MORNING. TEMP PROFILE ON GFS WARMS ENOUGH SO THAT PTYPE MAY BECOME
AN ISSUE. ECMWF MAINTAINS DRY CONDITIONS SATURDAY NIGHT WITH BULK
OF PCPN SUNDAY PM/EVENING...AND MAINLY SNOW AS TEMPS SLIGHTLY
COOLER. HAVE ATTEMPTED TO BLEND THE TWO MODELS. LOW CONFIDENCE IN
TIMING OF THIS SYSTEM...BUT CONFIDENCE INCREASING THAT THERE WILL
BE AN EVENT IN THE SATURDAY NIGHT TO SUNDAY NIGHT TIMEFRAME. HAVE
GONE WITH 40 POPS FOR SNOW OR SNOW/RAIN MIX ACROSS THE AREA...SO
THERE IS HOPE FOR THOSE LOOKING FOR A WHITE CHRISTMAS. THOSE WITH
TRAVEL INTERESTS AROUND CHRISTMAS DAY SHOULD MONITOR LATEST
FORECASTS. DRIER CONDITIONS EXPECTED MONDAY...ALTHOUGH THERE MAY
BE A FEW SNOW SHOWERS...ESPECIALLY OVER NORTHERN SECTIONS.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
THROUGH 12Z WEDNESDAY...INTERMITTENT LIGHT SNOW SHOWERS OVER THE
GREEN MOUNTAINS INCLUDING KMPV WILL BE ENDING BY 14Z. AREAS OF
MVFR CIGS THIS MORNING WILL IMPROVE TO VFR AT ALL SITES BY
16Z...WITH MAINLY CLEAR SKIES EXPECTED THIS AFTERNOON/EVENING AS
HIGH PRESSURE MOVES ACROSS THE REGION. EXPECT AN INCREASE IN
CLOUDS TONIGHT WITH CHANCE LIGHT SNOW AND MVFR CONDITIONS TOWARDS
12Z WEDNESDAY. GUSTY NORTHWEST WINDS WILL DIMINISH THIS MORNING
AND BECOME LIGHT AND VARIABLE THIS AFTERNOON.
OUTLOOK 12Z WEDNESDAY THROUGH SATURDAY...
MVFR CEILINGS AND MIXED PCPN DEVELOPING EARLY WEDNESDAY WITH
APPROACHING WARM FRONT. LIGHT SNOW/SLEET MIX WILL CHANGE TO RAIN
BY WEDNESDAY AFTERNOON. MVFR WITH PERIODS OF IFR CEILINGS EXPECTED
MUCH OF WEDNESDAY AND WEDNESDAY NIGHT WITH HIR TRRN OBSCD.
THURSDAY WILL FEATURE PARTIAL CLEARING WITH SOME MVFR CEILINGS...
ESPECIALLY AT MPV/SLK. COLD FRONT BRINGS CHANCE SNOW SHOWERS WITH
POSSIBLE MVFR CONDITIONS FRIDAY MORNING. HIGH PRESSURE AND VFR
CONDITIONS EXPECTED FRIDAY PM/NIGHT AND CONTINUING THROUGH MUCH OF
SATURDAY. NEXT FRONTAL SYSTEM APPROACHES FROM THE SOUTHWEST LATE
SATURDAY WITH IFR SNOW POSSIBLE SATURDAY NIGHT.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.
&&
$$
SYNOPSIS...TABER
NEAR TERM...TABER
SHORT TERM...TABER
LONG TERM...RJS
AVIATION...RJS
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
600 AM EST TUE DEC 20 2011
.SYNOPSIS...
HIGH PRESSURE LOCATED OVER THE GREAT LAKES WILL MOVE TOWARD THE
NORTH COUNTRY TODAY. THIS WILL PROVIDE OUR REGION WITH INCREASING
AMOUNTS OF SUNSHINE...ALONG WITH COOL NORTHERLY WINDS. TEMPERATURES
WILL HOLD IN THE UPPER TEENS IN THE MOUNTAINS TO THE MID TO UPPER
20S IN THE VALLEYS. THE NEXT STORM SYSTEM WILL IMPACT THE REGION
WEDNESDAY INTO THURSDAY...WITH MIXED PRECIPITATION QUICKLY
CHANGING TO A COLD RAIN. TEMPERATURES WILL WARM BACK INTO THE 30S
TO NEAR 40 IN MANY LOCATIONS ON WEDNESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 600 AM EST TUESDAY...SEVERAL CHANGES TO CRNT FCST BASED ON IR
SATL PICS AND LATEST TEMPS. SFC COLD FRNT HAS PUSHED INTO SOUTHERN
NEW ENGLAND THIS MORNING WHILE LLVL CAA CONTS. THIS HAS RESULTED
IN A TIGHT NORTH TO SOUTH THERMAL GRADIENT ACRS OUR CWA...ALONG
WITH A WIDE RANGE IN TEMPS. TEMPS RANGE FROM THE M/U TEENS ACRS
NNY TO 35F AT VSF. WL UPDATE WITH CRNT TEMPS ATTM AND INCREASE
DAYTIME HIGHS BY SEVERAL DEGREES ACRS CENTRAL/SOUTHERN VT. IN
ADDITION...LATEST RUC13 SHOWS PLENTY OF LLVL MOISTURE RESULTING IN
LOTS OF CLOUDS ACRS OUR CWA. HAVE INCREASED CLOUDS ACRS MOST OF
THE REGION...BUT EXPECT AREAL COVERAGE TO DECREASE BY 15Z TODAY.
REST OF FCST IN GOOD SHAPE.
WATER VAPOR SHOWS WELL DEFINED SHORT WAVE QUICKLY MOVING
SOUTHEAST OF OUR CWA THIS MORNING ASSOCIATED WITH SFC COLD
FRNT...WHILE AREA OF SUBSIDENCE/DRY AIR ALOFT ADVECTS INTO OUR
REGION. THIS COMBINED WITH SFC HIGH PRES OVERHEAD BY 18Z
TODAY...WL RESULT IN CLRING SKIES AND PLENTY OF SUNSHINE. THE
COMBINATION OF LEFTOVER MOISTURE AND SOME WEAK UPSLOPE FLW THIS
MORNING MAY PRODUCE A FEW FLURRIES AND CLOUDS ACRS THE MTNS. TEMPS
WL BE TRICKY WITH SHARP THERMAL GRADIENT AND ASSOCIATED CAA ACRS
OUR CWA TODAY. THINKING U10S MTNS/SLK TO NEAR L30S VSF...WITH MANY
AREAS HOLDING IN THE M/U 20S.
TONIGHT...SFC HIGH PRES QUICKLY SHIFTS OFF THE MID ATLANTIC COAST
WITH A RETURN SOUTHERLY FLW DEVELOPING. THIS RESULTS IN SIGNIFICANT
WARMING OF THE LLVLS WITH 850MB TEMPS NEAR 0C BY 12Z WEDS ACRS OUR
SOUTHERN ZNS. THE COMBINATION OF WAA...INCREASING CLOUDS...AND
DEVELOPING SOUTHERLY FLW WL MAKE FOR A CHALLENGING LOW TEMP FCST.
THINKING COLDEST TEMPS WL BE ACRS THE NEK/EASTERN VT WITH LOWS IN
THE LOWER TEENS TO NEAR 20F CPV/SLV. ONCE AGAIN EXPECT LOWS TO BE
BEFORE MIDNIGHT WITH TEMPS RISING TWD MORNING. WL CONT TO MENTION
SCHC/CHC POPS ALONG AND SOUTH OF A MSS TO SLK TO MPV LINE BTWN
09Z-12Z WEDS...ASSOCIATED WITH WAA LIFT/MOISTURE. OVERALL QPF
AMOUNTS WL BE VERY LIGHT...WITH MOST OF THE PRECIP EVAPORATING
BEFORE REACHING THE GROUND...DUE TO VERY DEEP DRY AIR AHEAD OF
MOISTURE/LIFT. THERMAL PROFILES SUPPORT ALL SNOW THRU 12Z
WEDS...WITH ONLY A DUSTING OF ACCUMULATIONS ANTICIPATED.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 415 AM EST TUESDAY...FCST FOCUS WL BE PRECIP EVENT WEDS
INTO THURS...ASSOCIATED WITH SOUTHERN PLAINS SYSTEM. ONCE AGAIN A
MAINLY COLD RAIN EVENT IS ANTICIPATED WITH QPF AMOUNTS BTWN 0.10
FOR THE CPV TO 0.40" FOR THE DACKS AND PARTS OF THE SOUTHERN GREEN
MTNS. SEVERAL PERIODS OF MAINLY LIGHT RAIN IS ANTICIPATED...WITH
BEST DEEP LAYER LIFT/MOISTURE BEING ACRS CENTRAL/SOUTHERN VT.
FIRST SURGE OF 850 TO 500MB MOISTURE AND 700 TO 500MB LIFT WL MOVE
FROM SOUTHWEST TO NORTHEAST ACRS OUR CWA BTWN 12Z-15Z WEDS.
THERMAL PROFILES SUPPORT A MIX OF SNOW...SLEET...AND FREEZING
RAIN...ESPECIALLY EAST OF THE GREEN MTNS...BUT TOTAL QPF AMOUNTS
ASSOCIATED WITH INITIAL BAND OF PRECIP WL BE LIGHT AND ONLY A
DUSTING OF SNOW/SLEET IS ANTICIPATED. LOW LEVEL SOUTH TO SOUTHWEST
FLW WL QUICKLY ADVECT WARMER TEMPS ACRS OUR CWA BY 15Z WEDS...WITH
85H TEMPS RISING BTWN +3C AND +5C...AND 925MB TEMPS NEAR +3C. IN
ADDITION...GIVEN POSITION OF SFC HIGH PRES WITH NO BLOCKING
SIGNATURE IN THE SLP FIELDS...FEEL COLD AIR WL QUICKLY RETREAT.
ALSO...LIMITED SNOW PACK AND DEVELOPING SOUTHERLY FLW WL HELP TO
ERODE LLVL COLD AIR...BEFORE HEAVIER PRECIP ARRIVES AFT 18Z WEDS.
THE BETTER DYNAMICS ASSOCIATED WITH DECAYING MID/UPPER LVL
CIRCULATION AND POTENT 5H VORT MOVES ACRS OUR CWA BTWN 21Z-06Z.
THIS ULVL SUPPORT COMBINED WITH GOOD 850 TO 500MB Q-VECTOR
CONVERGENCE AND GOOD AVAILABLE MOISTURE WITH PWS APPROACHING
0.75"...WL RESULT IN A PERIOD OF OCCASIONAL LIGHT RAIN ACRS OUR
CWA ON WEDS NIGHT. ONCE AGAIN...A FEW POCKETS OF FREEZING RAIN WL
BE POSSIBLE ACRS EASTERN VT/NEK...BUT NOT ANTICIPATING ANY ICE
ACCUMULATION ATTM. TEMPS WL WARM INTO THE L40S CPV TO M30S
NEK/EASTERN VT ON WEDS. LITTLE CHANGE IN TEMPS IS EXPECTED ON WEDS
NIGHT WITH CLOUDS AND PRECIP EXPECTED. SFC COLD FRNT APPROACHES
NORTHERN CWA BY 12Z THURS...WITH TIGHT THERMAL GRADIENT. THIS WL
PUSH ACRS OUR FA ON THURS...WITH COOLER TEMPS AND THE CHANCE FOR
RAIN/SNOW SHOWERS. UNFORTUNATELY...AS THE AIR BECMS COLD ENOUGH TO
SUPPORT SNOW...THE BEST MOISTURE MOVES TO OUR EAST. NOT
ANTICIPATING MUCH SNOW ACCUMULATION...MAYBE AN INCH OR SO IN THE
FAVORABLE UPSLOPE REGIONS OF THE DACKS/GREEN MTNS. TEMPS WL START
NEAR 40F IN THE CPV...BUT WL FALL INTO THE 30S AS NORTH WINDS AND
LLVL CAA DEVELOPS. OTHERWISE...MAINLY 30S WL BE THE HIGHS ON THURS
ACRS THE MTNS.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 230 PM EST MONDAY...DEVELOPING COLD FRONT NORTH OF THE
INTERNATIONAL BORDER WILL DROP SOUTH INTO FORECAST LATER THURSDAY
NIGHT. MEANWHILE...LOW PRESSURE WILL TRACK SOUTH OF THE AREA PASSING
OFF MID ATLANTIC COAST. EXPECT SOME SNOW SHOWERS ASSOCIATED WITH
COLD FRONT TO AFFECT NORTHERN ZONES...WITH LIGHT SNOW ASSOCIATED
WITH LOW TO OUR SOUTH POSSIBLY AFFECTING SOUTHERN ZONES. ALL ADDS
UP TO CHANCE POPS...MAINLY AFTER MIDNIGHT. LOW DEPARTS OFFSHORE FRIDAY
MORNING...BUT THERE WILL BE A CONTINUED CHANCE FOR A FEW SNOW SHOWERS
AS THE COLD FRONT DEPRESSES SOUTH OF FORECAST AREA BY AFTERNOON.
HIGH PRESSURE BUILDING ACROSS ONTARIO INTO QUEBEC LATER FRIDAY
INTO SATURDAY WILL BRING MAINLY DRY WEATHER TO THE NORTH COUNTRY
ALONG WITH COLDER TEMPERATURES. LOWS FRIDAY NIGHT UNDER MAINLY CLEAR
SKIES WILL BE MAINLY IN THE TEENS...AND HIGHS ON SATURDAY IN THE
UPPER 20S TO LOWER 30S.
SITUATION BECOMES MORE COMPLICATED SATURDAY NIGHT AS HIGH MOVES
INTO EASTERN CANADA AND SHORTWAVE AND ASSOCIATED SURFACE LOW LIFT
NORTHEAST FROM THE TENNESSEE VALLEY. SOME RATHER SIGNIFICANT
DIFFERENCES BETWEEN GFS AND ECMWF REGARDING THIS SYSTEM...
ESPECIALLY WITH RESPECT TO TIMING. GFS MUCH FASTER...BRINGING
PRECIPITATION IN QUICKLY SATURDAY NIGHT AND EXITING CHRISTMAS
MORNING. TEMP PROFILE ON GFS WARMS ENOUGH SO THAT PTYPE MAY BECOME
AN ISSUE. ECMWF MAINTAINS DRY CONDITIONS SATURDAY NIGHT WITH BULK
OF PCPN SUNDAY PM/EVENING...AND MAINLY SNOW AS TEMPS SLIGHTLY
COOLER. HAVE ATTEMPTED TO BLEND THE TWO MODELS. LOW CONFIDENCE IN
TIMING OF THIS SYSTEM...BUT CONFIDENCE INCREASING THAT THERE WILL
BE AN EVENT IN THE SATURDAY NIGHT TO SUNDAY NIGHT TIMEFRAME. HAVE
GONE WITH 40 POPS FOR SNOW OR SNOW/RAIN MIX ACROSS THE AREA...SO
THERE IS HOPE FOR THOSE LOOKING FOR A WHITE CHRISTMAS. THOSE WITH
TRAVEL INTERESTS AROUND CHRISTMAS DAY SHOULD MONITOR LATEST
FORECASTS. DRIER CONDITIONS EXPECTED MONDAY...ALTHOUGH THERE MAY
BE A FEW SNOW SHOWERS...ESPECIALLY OVER NORTHERN SECTIONS.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
THROUGH 06Z WEDNESDAY...COLD FRONT HAS PUSHED SOUTH OF FRECAST
AREA. INTERMITTENT LIGHT SNOW SHOWERS WILL BE ENDING BY 08Z WITH
AREAS OF MVFR CIGS THROUGH ABOUT 12Z. EXPECT CIGS IMPROVING TO VFR
ALONG WITH A DECREASE IN CLOUD COVER...WITH CLEAR SKIES BY 17Z ALL
TAF SITES. VFR CONDITIONS WILL THEN PREVAIL FOR THE REST OF THE
PERIOD. EXPECT GUSTY NORTHWEST WINDS TO SLACKEN INTO THE 5-10KT
RANGE BY MID-MORNING.
OUTLOOK 06Z WEDNESDAY THROUGH SATURDAY...
VFR THRU 10Z WEDNESDAY...THEN MVFR CEILINGS AND MIXED PCPN
DEVELOPING EARLY WEDNESDAY WITH APPROACHING WARM FRONT. LIGHT
SNOW/SLEET MIX WILL CHANGE TO RAIN BY WEDNESDAY AFTERNOON. MVFR
WITH PERIODS OF IFR CEILINGS EXPECTED MUCH OF WEDNESDAY AND
WEDNESDAY NIGHT WITH HIR TRRN OBSCD. THURSDAY WILL FEATURE PARTIAL
CLEARING WITH SOME MVFR CEILINGS...ESPECIALLY AT MPV/SLK. COLD
FRONT BRINGS CHANCE SNOW SHOWERS WITH BRIEF MVFR CONDITIONS FRIDAY
MORNING. HIGH PRESSURE AND VFR CONDITIONS EXPECTED FRIDAY PM/NIGHT
AND CONTINUING THROUGH MUCH OF SATURDAY. NEXT FRONTAL SYSTEM
APPROACHES FROM THE SOUTHWEST LATE SATURDAY WITH IFR RAIN OR SNOW
POSSIBLE SATURDAY NIGHT.
&&
.MARINE...
STRONG SOUTH TO SOUTHWEST WINDS CONTINUE THIS AFTERNOON ON LAKE
CHAMPLAIN WITH 20 TO 30 KNOTS STILL BEING OBSERVED AT COLCHESTER
REEF AT 3 PM. THIS IS EXPECTED TO DECREASE SLIGHTLY TO 15 TO 25
KNOTS THIS EVENING. WINDS WILL THEN TURN TO THE WEST AND THEN
NORTHWEST OVERNIGHT FROM 15 TO 25 KNOTS. THUS THE LAKE WIND
ADVISORY CONTINUES THROUGH TONIGHT. THE NORTHWEST WINDS WILL HANG
ON INTO TUESDAY MORNING BEFORE WEAKENING DURING THE DAY WITH 5 TO
15 KNOT WINDS EXPECTED IN THE AFTERNOON. WAVES WILL BE 3 TO 5 FEET
THIS AFTERNOON...DECREASING TO 1 TO 3 FEET OVERNIGHT.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...NONE.
NY...NONE.
&&
$$
SYNOPSIS...TABER
NEAR TERM...TABER
SHORT TERM...TABER
LONG TERM...RJS
AVIATION...RJS
MARINE...
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
149 PM EST TUE DEC 20 2011
.AVIATION...
WMFNTL BNDRY ALG THE OH RVR WILL CONT TO ADVT SLOWLY NWD THIS PD.
THUS WIDESPREAD MVFR/IFR CIGS WILL CONT W/A GRADUAL DETERIORATION
XPCD OVERNIGHT AS SFC BNDRY NEARS CLOSER...LL FLW BACKS MORE SRLY
AND DRY SLOT BLDG IN OVERHEAD LEADING TO AREAS OF DZ. PRIOR FCST HAD
THIS WELL IN HAND AND CARRIED FORWARD W/JUST A FEW TWEAKS. IMPROVING
CONDS XPCD JUST AFT THE END OF THIS PD WED AFTN AS UPR TROF OPENS
AND ACCELERATES NEWD INTO THE ERN LAKES.
&&
.PREV DISCUSSION... /ISSUED 419 AM EST TUE DEC 20 2011/
SHORT TERM.../TODAY THROUGH WEDNESDAY NIGHT/
STRONG ISENTROPIC LIFT HAS ALLOWED FOR BAND OF PERSISTENT PRECIP
FROM SOUTHERN QUARTER OR SO OF THE FORECAST AREA BACK TO THE WEST
ACROSS MUCH OF CENTRAL AND SOUTHERN ILLINOIS. EARLIER TAMDAR
SOUNDINGS INDICATED THAT RISK FOR SNOW MAY BE MINIMAL INTO TUES
MORNING. HOWEVER...RECENT SFC OBS AND CALL AROUND TO CENTRAL
DISPATCHES IN SOUTHERN AREAS SHOWS RAIN HAS BEEN MIXING WITH AND
EVEN CHANGING TO SOME LIGHT SNOW. MAIN SWITCH OVER HAS BEEN
OCCURRING IN SE AREAS WHERE NE FLOW HAS ALLOWED SLIGHTLY COLDER
TEMPS TO MIX FURTHER THROUGH THE COLUMN. SFC TEMPS WERE ABOVE
FREEZING ACROSS THE AREA WITH ANY SNOW MELTING AS IT FALLS. OF
CONCERN IS NEW 6Z NAM12 WHICH SUGGEST A SWATH OF LOCALLY HEAVIER
PRECIP MAY ARRIVE TOWARDS 12Z AND FALL IN AREA WHERE COOLING MAY BE
MAXIMIZED. GRIDS HAVE HAD LIGHT ACCUMS IN FOR SEVERAL DAYS AND HAVE
KEPT THIS THINKING GENERALLY THE SAME THROUGH THIS MORNING. KFWA
OBSERVER JUST CONTACTED US WITH A FEW TENTHS OF AN INCH ON VEHICLES
BUT EVERYTHING MELTING ON THE GROUND. BLEND OF RUC AND LOCAL WRF WAS
USED TO GET POP LAYOUT TODAY WITH VERY TIGHT CUT OFF TO THE NORTH AS
LOCATIONS NORTH OF US 6 MAY SEE LITTLE OR NO PRECIPITATION. LOCAL
WRF AND HRRR WANT TO QUICKLY DRY THINGS OUT IN THE 21 TO 00Z TIME
FRAME AS BEST FORCING SHIFTS NORTH WITH THE WARM FRONT PASSING
THROUGH. THIS COULD LEAVE MUCH OF THE AREA EITHER DRY OR WITH SOME
AREAS OF DRIZZLE. HAVE MADE NO CHANGES TO THIS AFTERNOON WITH CHC
POPS REMAINING IN FAR N AND NW AREAS AND LIKELY REMAINDER OF THE
AREA. WILL LET DAY SHIFT MONITOR TRENDS.
UPPER LOW WILL TRACK TOWARDS THE REGION LATER TONIGHT INTO WEDS.
MODELS STILL VARY ON PATH OF THIS FEATURE EITHER BEING OVER THE AREA
OR JUST TO THE SE. STILL THINK MOST AREAS WILL SEE A CHANCE FOR
LIGHT RAIN FOR AT LEAST A 6 TO 12 HOUR PERIOD BEFORE ENDING BY WEDS
EVENING.
IN TERMS OF TEMPS THROUGH THE PERIOD...EXPECTING LITTLE OVERALL
CHANGE IN SFC TEMPS TODAY ACROSS THE NORTH AND A SLOW WARM UP IN
SOUTHERN AREAS ESPECIALLY AS WARM FRONT MOVES NORTH. IF ANY BREAKS
IN THE CLOUDS CAN FORM LATER THIS AFTERNOON...COULD SEE HIGHS WARMER
THAN FORECAST. HOWEVER...OBS TO THE SOUTH SHOW PRETTY EXTENSIVE
CLOUD COVER SO WILL HOLD OFF ON ANY CHANGES FOR HIGHS TODAY. HIGHS
ON WEDS COULD VARY GREATLY DEPENDING ON THE TRACK OF THE UPPER LOW
WITH WARMEST READINGS SE WHERE HIGHS COULD EASILY CLIMB INTO THE
50S. OVERNIGHT LOWS BOTH NIGHTS EXPECTED TO REMAIN ABOVE FREEZING.
LONG TERM.../THURSDAY THROUGH MONDAY/
NEXT IN SERIES OF SRN STREAMS SHRTWVS EMANATING FROM SPLIT FLOW
OVER WRN U.S. WILL LIFT RAPIDLY NE FROM THE SRN PLAINS TO THE LWR
OH VALLEY THU EVE. THIS SYSTEM SHOULD BE CONSIDERABLY WEAKER THAN
ITS PREDECESSOR DUE TO MORE SHEARING FM INTERACTION WITH NRN
STREAM SHRTWV MOVG ESE INTO THE UPR GRTLKS AT THE SAME TIME. PER
GFS SOLUTION... SFC/H85 BAROCLINIC ZONE EXPECTED TO REMAIN FAR
ENOUGH TO THE S-SE TO KEEP NWRN EDGE OF PRECIP SHIELD WITH THIS
SYSTEM JUST SE OF OUR CWA. WK WAA AHEAD OF THE NRN STREAM
SHRTWV/CDFNT SHOULD ALLOW HIGHS TO REACH THE L-M40S ACROSS THE
AREA DESPITE CONSIDERABLE CLOUDINESS.
CDFNT WILL MOVE THROUGH THE AREA BY THU EVE WITH HIGH PRESSURE OVER
THE NRN PLAINS BUILDING EAST ACROSS THE WRN GRTLKS IN ITS WAKE. WK
CONVERGENCE ALONG FRONT AS IT MERGES WITH CIRCULATION OF SURFACE LOW
TO THE SE SUGGESTS JUST SOME CLOUDINESS WILL ACCOMPANY IT... BUT
LITTLE CHC OF MEASURABLE PRECIP. FAIRLY WK CAA WITH H85 TEMPS ONLY
FALLING TO -2C/-4C ACROSS THE CWA COMBINED WITH CLOUDINESS SUGGESTS
LOWS WILL ONLY BE IN THE U20S/L30S THU NGT.
FOR THE EXTENDED DAYS 4-7...MEDIUM RANGE MODELS IN DECENT AGREEMENT
INDICATING MEAN TROF OVER WRN U.S. IN SHORT TERM WILL PROGRESS TO
NEAR THE EAST COAST BY THE END OF THE LONG TERM PERIOD. THIS SHOULD
RESULT IN A GRADUAL COOL DOWN OVER THE HOLIDAY WEEKEND WITH A WARMUP
EARLY NEXT WEEK AS RIDGING ALOFT MOVES INTO THE GRTLKS IN THE WAKE
OF THIS TROF. SPLIT FLOW WILL PERSIST AS THE MEAN TROF MOVES EAST...
AT LEAST THROUGH FRIDAY OR SAT. MODELS HAVE VERY DIFFERENT
TIMING/TRACK/INTENSITY WITH SHRTWV LIFTING OUT OF THE SRN STREAM
FLOW OVER THE WEEKEND... THUS LITTLE CONFIDENCE IN THE POPS SATURDAY
BUT MAINTAINED FCST CONTINUITY BY FOLLOWING GFS SOLUTION WHICH
INDICATES A CHC OF RAIN/SNOW IN OUR AREA AROUND THIS PERIOD. IN THE
WAKE OF THIS SYSTEM... NRN STREAM TROF PROGGED TO STRENGTHEN/DIG SE
A BIT WHICH SHOULD ALLOW AIRMASS OVER THE WRN GRTLKS TO BECOME COLD
ENOUGH FOR SOME LAKE EFFECT SNOW SHOWERS BY LATE SUNDAY... THOUGH
DOESN`T LOOK LIKE A FAVORABLE SETUP FOR SGFNT LES ATTM WITH GFS
INDICATING FAIRLY LOW INVERSION HEIGHTS.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SHORT TERM...FISHER
LONG TERM...JT
AVIATION...T
AREA FORECAST DISCUSSION
NWS TOPEKA KS
319 PM CST TUE DEC 20 2011
.DISCUSSION...
SHORT RANGE (TONIGHT AND WEDNESDAY)...
20Z WATER VAPOR IMAGERY AND ASSOCIATED RUC ANALYSIS CONTINUES TO
SHOW THE 500 MB TROUGH MOVING SLOWLY TO THE NORTHEAST ACROSS EASTERN
KANSAS. CURRENTLY IT IS SITTING OVER SOUTH CENTRAL KANSAS AND SHOULD
PUSH THROUGH THE AREA BY TONIGHT. RADAR TRENDS SHOW PRECIPITATION
ENDING ACROSS CENTRAL KANSAS...AND THIS TREND SHOULD CONTINUE
THROUGH THE REST OF THE EVENING AS THE BETTER LIFT ASSOCIATED WITH
THIS SYSTEM PUSHES EAST. ANOTHER SHIELD OF LIGHT PRECIPITATION IS
MOVING NORTHEASTWARD ALONG THE KANSAS TURNPIKE AND WILL LIKELY BRING
ANOTHER ROUND OF MIXED PRECIPITATION TO AREAS EAST OF THE TURNPIKE.
CURRENTLY KUKL INDICATES 36 DEGREES AS DOES KOJC...SO EXPECT THE
BULK OF THE REMAINING PRECIP TO FALL IN THE FORM OF A RAIN/SNOW MIX
FOR THE REMAINDER OF THE EVENING ALONG THE NEWLY FORMED DEFORMATION
BAND. EXPECT THE BEST LIFT WITH THIS ROUND OF SHOWERS TO MOVE OFF TO
THE EAST BY LATE THIS EVENING THUS ENDING ALL PRECIP FOR OUR
FORECAST AREA. SHOULD THERE BE ANY SNOW ASSOCIATED WITH THIS
EVENINGS PRECIP DON`T EXPECT MUCH MORE THAN A DUSTING OF SNOW ON
GRASSY SURFACES. SINCE ROADWAYS ARE WET FROM THE ONGOING PRECIP AND
OVERNIGHT LOWS WILL DROP INTO THE TEENS TO TWENTIES THERE IS A
POTENTIAL FOR SLICK SPOTS ON ROADWAYS...ESPECIALLY ONCE TEMPS DIP
BELOW 32 DEGREES. SKIES WILL GRADUALLY CLEAR BEHIND THE DEPARTING
SYSTEM...FIRST ACROSS CENTRAL AND NORTH CENTRAL KANSAS...THEN BY 12Z
ACROSS FAR EASTERN KANSAS. AS A RESULT OF THE NEWLY FALLEN SNOW
ACROSS C/NC KANSAS AND THE CLEARING SKIES EXPECT LOW TEMPS TO REACH
INTO THE MID TEENS TONIGHT...AND INTO THE LOWER TO MID 20S FURTHER
EAST WHERE NO SNOW FELL AND SKIES WILL BE SLOWER TO CLEAR. WEDNESDAY
WILL BRING A MILD DAY ACROSS NORTHEAST KANSAS AS TEMPS WILL REACH
INTO THE LOWER TO MID 40S WHERE NO NEW SNOW FELL...BUT WILL ONLY
REACH THE MID 30S OVER THE SNOW PACK IN C/NC KANSAS. JL
THURS-TUES...AFTER A BREAK FROM THE CLOUDS AND
PRECIPITATION...THE NEXT UPPER TROF APPROACHES THE STATE FROM THE
NORTH AND NORTHWEST THURSDAY AND THROUGH FRIDAY. AT THIS TIME MAIN
PIECE OF ENERGY AND DYNAMICS STAYS TO THE WEST...LEAVING THE LEAD
SHEAR VORTICITY AHEAD OF THE NORTHERN WAVE TO SLIDE ACROSS KANSAS.
ENOUGH LIFT WITH THIS AND COUPLED WITH SOME FRONTOGENETIC FORCING
TO BRING A CHANCE OF SNOW THROUGH FRIDAY. NOT MUCH MOISTURE TO
WORK WITH SO DONT EXPECT MUCH FOR ACCUMULATIONS DESPITE HIGHER
SNOW TO LIQUID RATIOS THAN THE PREVIOUS STORM. STILL VARIATIONS IN
THE GUIDANCE AS TO HOW TO HANDLE THE WESTERN PORTION OF THIS
SYSTEM WITH EC/NAM TRENDING A SOUTHWARD SLOWER TRACK AND GFS MORE
PROGRESSIVE ACROSS AND OUT OF OUR AREA. EC IS THEREFORE COOLER IN
THE EXTENDED WHILE GFS IS WARMER IN MORE WESTERLY FLOW. HAVE DRY
CONDITIONS BEYOND FRIDAY WITH A SLOW WARMING TREND...AND WILL HAVE
TO WATCH EVOLUTION OF THAT UPPER PATTERN FOR CHANGES. 67
&&
.AVIATION...
IFR CONDITIONS EXPECTED TO DOMINATE FOR MUCH OF THE DAY INTO THE
OVERNIGHT WITH BRIEF PERIODS OF LIFR OR MVFR POSSIBLE. SNOW WILL
CONTINUE AT KMHK FOR MUCH OF THE AFTERNOON WITH DRIZZLE EXPECTED
TO CONTINUE AT KTOP AND KFOE. FROZEN PRECIPITATION MAY MIX IN
BRIEFLY AT TIMES AT KTOP AND KFOE BUT TEMPERATURES AT THE SURFACE
SHOULD REMAIN ABOVE FREEZING AS PRECIPITATION OCCURS. PRECIP. WILL
COME TO AN END AROUND 00Z WITH CEILINGS IMPROVING TO VFR BY 10Z
TOMORROW.
ANDERSON
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS DODGE CITY KS
1136 AM CST TUE DEC 20 2011
.AVIATION...
FOR THE 18Z TAF ISSUANCE...
LIGHT SNOW OR BLOWING SNOW WILL BE POSSIBLE OVER THE NEXT COUPLE
OF HOURS AS THE STORM SYSTEM MOVES TO THE EAST. OTHERWISE EXPECT
MOSTLY CLOUDY SKIES AOA030 UNTIL AROUND 20Z. THEREAFTER...SKIES
SHOULD CLEAR FROM WEST TO EAST AND BECOME MOSTLY CLEAR BY THIS
EVENING. NORTHERLY WINDS AROUND 20 KNOTS EARLY THIS AFTERNOON
SHOULD SHIFT TO THE NORTHWEST AND DECREASE TO AROUND 12 KNOTS LATE
THIS AFTERNOON. WINDS ARE THEN ANTICIPATED TO BECOME LIGHT AND
VARIABLE THIS EVENING INTO THE OVERNIGHT HOURS.
&&
.PREV DISCUSSION... /ISSUED 621 AM CST TUE DEC 20 2011/
UPDATE...
AVIATION /FOR THE 12Z TAF ISSUANCE/
IFR CONDITIONS WILL PERSIST THROUGH THE NEXT SEVERAL HOURS BASED ON
BOTH LOW CEILINGS AND VISIBILITIES REDUCED IN SNOW. SOME IMPROVEMENT TO
THE MVFR RANGE IS POSSIBLE BY AROUND 18 UTC AS THE UPPER LOW LIFTS
FARTHER INTO EASTERN KANSAS. WINDS WILL ALSO BE DIMINISHING INTO HE
15 TO 25 MPH RANGE LATER IN THE DAY, SUPPORTED BY LOCAL GFS MOS
GUIDANCE.
PREV DISCUSSION... /ISSUED 232 AM CST TUE DEC 20 2011/
DISCUSSION...
DAYS 1-2...
00Z TUESDAY UPPER AIR ANALYSIS PLACED A 850MB AND 700MB
BAROCLINIC ZONE FROM JUST NORTH OF ELKHART TO NEAR HAYS. THE UPPER
LOW WAS POSITIONED NEAR AMARILLO. STILL OBSERVING GOOD MOISTURE
AND WARM AIR ADVECTION ACROSS CENTRAL AND PARTS OF SOUTHWEST
KANSAS AS OUR UPPER LOW MOVES TOWARDS NORTHWEST OKLAHOMA EARLIER
THIS MORNING. JET STREAK DYNAMICS NEAR THE LEFT EXIT REGION OF
250MB JET WILL BE LOCATED ACROSS PORTIONS OF NORTH CENTRAL KANSAS
EARLY THIS MORNING SO AT THIS TIME BASED ON THE LOCATION OF THE
MID LEVEL FRONTOGENESIS IT WOULD APPEAR THAT PERIODS OF MODERATE
SNOW STILL WILL BE POSSIBLE IN AREAS ALONG AND NORTH OF HIGHWAY
156. THE NAM, RUC, AND HRRR WERE ALSO ALL IN DECENT AGREEMENT WITH
PRECIPITATION CONTINUING THROUGH THE EARLY MORNING HOURS IN THIS
AREA SO INITIAL THOUGHTS WILL BE TO FOLLOW THE GENERAL TRENDS OF
THE NAM,RUC AND HRRR OVER THE NEXT 6-9 HOURS. FURTHER WEST NEAR
THE COLORADO BORDER AND AREAS SOUTH NEAR THE OKLAHOMA BORDER THE
PRECIPITATION SHOULD BE STARTING TO TAPER OFF.
WINDS STILL WILL BE AN ISSUE EARLY TUESDAY MORNING GIVEN THE
LOCATION OF THE PRESSURE GRADIENT NORTHWEST OF THE SURFACE LOW
ALONG WITH THE CURRENT VAD WINDS AND PROFILER DATA. ALTHOUGH WIND
SPEEDS ARE NOT EXPECTED TO BE AS STRONG AS YESTERDAY, IT DOES
APPEAR THAT SOME REDUCED VISIBILITIES WILL CONTINUE IN THE
BLIZZARD WARNING AREA. LOCATIONS SOUTH OF HIGHWAY 156 WILL SEE
IMPROVING CONDITIONS EARLY THIS MORNING BUT GIVEN ONGOING SNOW,
BLOWING SNOW AND CURRENT CONDITIONS HAVE DECIDED NOT TO BEGIN
TRIMMING THE BLIZZARD WARNING YET.
BY MID DAY ISENTROPIC DOWN GLIDE WILL BEGIN TO DEVELOP WEST OF
OUR UPPER LOW WHICH WILL BE LOCATED NEAR SOUTH CENTRAL KANSAS. A
SURFACE HIGH WILL THEN BEGIN TO BUILD INTO WESTERN KANSAS FROM THE
NORTHWEST. MODEL SOUNDINGS CONTINUE TO SUGGEST TO CLOUD COVER
THROUGH MUCH OF THE DAY SO BASED ON THIS AND COLD AIR ADVECTION
OCCURRING OVER THE SNOW PACK WILL UNDERCUT GUIDANCE FOR HIGHS
TODAY.
TONIGHT SKIES WILL CLEAR AS WINDS DECREASE TO LESS THAN 10KTS.
WINDS NOT IDEAL FOR A GREAT NIGHT OF RADIATION COOLING BUT
CONDITIONS STILL FAVOR UNDERCUTTING CURRENT GUIDANCE AND STAYING
CLOSE TO THE CURRENT FORECAST OF WITH LOWS EARLY WEDNESDAY MORNING
IN THE SINGLE DIGITS.
WEDNESDAY SHOULD BE SUNNY AS WESTERLY DOWNSLOPE FLOW IMPROVES
ACROSS WESTERN KANSAS. DECENT WARMING OCCURS ABOVE THE SURFACE BUT
BASED ON SNOWFALL EXPECTED ACROSS SOUTHWEST KANSAS FEEL MUCH OF
THE WARMING WILL GO INTO SNOW MELT. AS A RESULT WILL UNDERCUT
GUIDANCE ONCE AGAIN AND FAVOR THE PREVIOUS FORECAST WHICH IS CLOSE
TO 10F COOLER THAN THE COOLEST GUIDANCE.
DAYS 3-7...
LONG TERM /THURSDAY THROUGH MONDAY/
A PROGRESSIVE LONGWAVE PATTERN IS IN STORE FOR THE EXTENDED PERIOD,
WITH AT LEAST A COUPLE OF ADDITIONAL COLD FRONTAL PASSAGES ACROSS
THE CENTRAL HIGH PLAINS.
AFTER THE MAJOR SYSTEM THAT IS CAUSING THE BLIZZARD RIGHT NOW OVER
WESTERN KANSAS LIFTS EASTWARD INTO THE UPPER MIDWEST ON TUESDAY
NIGHT AND WEDNESDAY, ANOTHER PAIR OF SHARP MID LEVEL IMPULSES WILL
BE ROTATING THROUGH THE MEAN TROUGH. THE FIRST WILL ROTATE SOUTHWARD
FROM THE NORTHERN ROCKIES AND THE SECOND, JUST AHEAD OF THE NORTHERN
STREAM SHORTWAVE, FROM THE DESERT SOUTHWEST. FROM A LOOK AT THE GFS
AND ECMWF THE TWO WAVES APPEAR TO ENHANCE THE MID LEVEL BAROCLINICITY
ACROSS WESTERN KANSAS ON THURSDAY, WHILE A SURFACE COLD FRONT DIVES
SOUTHWARD ACROSS THE AREA EARLY IN THE DAY. BOTH MODELS HAVE BEEN
CONSISTENT IN PRODUCING BETWEEN 0.05" AND 0.15" OF PRECIPITATION
TIED TO THE LEADING SHORTWAVE, WITH POST SURFACE FRONT QPF. QUITE COLD
850 MB AIR ABOUT -5 T0 -8 SHOULD ENSURE THE PRECIPITATION TYPE WOULD
BE SNOW, AND AS A RESULT, IT IS POSSIBLE CENTRAL KANSAS AND MUCH OF
SOUTHWEST WILL BE EXPERIENCING ADDITIONAL, BUT PROBABLY MINOR
ACCUMULATIONS ON THURSDAY AFTERNOON. THE REMAINDER OF THE FORECAST
DOES LOOK DRY, BUT COLD. THE SECOND OF THESE UPPER SHORTWAVES
ROTATES THROUGH THE MEAN TROUGH ON FRIDAY AND SURFACE WINDS BEGIN TO
WEAKEN AS THE UPPER LEVEL HEIGHT FIELDS BECOME PARALLEL TO THE
MOUNTAIN BARRIER. FRIDAY WILL REMAIN COLD WITH VERY WEAK SURFACE
WINDS OVER THE AREA, BUT THE 850 MB TEMPERATURES BEGIN TO INCREASE
WITH STRONGER DOWNSLOPE FLOW OVER THE SNOWPACK. MODELS SEEM TO BUMP
MAXIMUM TEMPERATURES ABOUT 5 DEGREES ON SATURDAY AFTERNOON, BUT THIS
IS STILL WELL BELOW NORMAL. THE MODELS CONTINUE THOUGH THE END OF
THE WEEKEND DRY AND COOL WITH DEEP NORTHWEST FLOW OVER THE HIGH
PLAINS REGION INTO MONDAY.
AVIATION...
FOR THE 06Z TAF ISSUANCE... BLIZZARD OR NEAR BLIZZARD CONDITIONS
WILL CONTINUE THROUGH EARLY TUESDAY MORNING WITH THE DOMINANT
FLIGHT CATEGORY BEING VLIFR AT GCK AND DDC THROUGH MUCH OF THE
NIGHT TOWARD DAYBREAK. WIND SPEEDS WILL GRADUALLY DECREASE BY
DAYBREAK WITH VISIBILITIES IMPROVING AS WELL. AFTER THE SNOW
CEASES...LOW OVERCAST WILL LIKELY PERSIST THROUGH AT LEAST THE
EARLY AFTERNOON BEFORE CLEARING TAKES PLACE AND VFR CONDITIONS
RESUME. -UMSCHEID
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 9 30 14 29 / 0 0 10 60
GCK 6 29 13 27 / 0 0 10 50
EHA 5 29 13 27 / 0 0 10 50
LBL 6 30 15 29 / 0 0 10 50
HYS 6 30 15 28 / 0 0 20 70
P28 14 38 23 33 / 10 0 10 50
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
FN12/42/42
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
110 PM EST TUE DEC 20 2011
.SYNOPSIS...
A COLD FRONT STALLING ACROSS THE UPPER OHIO VALLEY WILL PROVIDE
RAIN TODAY. LOW PRESSURE, COMING NORTHEAST FROM TEXAS, WILL BRING
MILDER TEMPERATURES AND RAIN TONIGHT INTO WEDNESDAY.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
PER RECENT RADAR AND SURFACE DATA, COUPLED WITH RECENT HRRR AND
NAM MODEL OUTPUT, EXPECT PRECIPITATION TO CONTINUE THIS AFTERNOON
AND BEGIN TO DECREASE IN COVERAGE INTO THE EARLY EVENING. NAM
MODEL OUTPUT SHOWS SOUTHEASTERLY WINDS INCREASE AHEAD OF THE LOW
PRESSURE CENTER INCOMING FROM TEXAS, CAUSING A SLOW WARM UP INTO
TONIGHT.
MODELS SHOW THERE MAY BE A BREAK IN THE RAIN SHOWERS EARLY TONIGHT, THEN
AN INCREASE IN RAIN SHOWER COVERAGE LATE TONIGHT AND DAYTIME
WEDNESDAY AS THE LOW PRESSURE CENTER PASSES NORTHEASTWARD THROUGH
OHIO.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
BLEND OF RECENT MODELS SHOWS SCATTERED POST-SYSTEM SHOWERS
CONTINUING IN THE WAKE OF THE EXITING LOW PRESSURE WEDNESDAY NIGHT.
A SECOND LOW PRESSURE SYSTEM, COMING NORTHEAST FROM LOUISIANA,
WILL PROVIDE SHOWERS THURSDAY NIGHT AND FRIDAY.
SOUTHWEST WINDS ALOFT WILL ENSURE TEMPERATURES REMAINING MILDER
THAN NORMAL, AS INDICATED BY RECENT GFS AND NAM MOS. THIS MILDNESS
WILL PREVENT ANY CHANGE TO WINTRY TYPE PRECIPITATION THIS PERIOD.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
MODELS IN FAIRLY GOOD AGREEMENT WITH SERIES OF SHORT WAVES RUNNING
ALONG THE NORTHERN PERIPHERY OF SUBTROPICAL RIDGE SATURDAY.
PROBLEM IS HOW MUCH PHASING WILL OCCUR...AND HOW FAR NORTH
PRECIPITATION WILL COME AS SURFACE LOWS MOVE ALONG THE FRONT IN
THE MID ATLANTIC STATES.
DID NOT STRAY TOO FAR FROM HPC GRIDS WITH BEST CHANCES OF PRECIP
SATURDAY INTO SUNDAY CHRISTMAS DAY. THERE CAN BE SUFFICIENT COOL
DOWN TO PROVIDE A CHANCE OF MIXED RAIN AND SNOW SHOWERS SOUTH
WITH SNOW SHOWERS IN THE NORTH.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
IFR CEILINGS WITH MVFR VISIBILITIES WILL MOSTLY PREVAIL ACROSS THE
TERMINALS INTO THE EVENING AS A FRONTAL BOUNDARY SLOWLY LIFTS NORTHWARD
ACROSS THE AREA. THE EXCEPTION WILL BE KMGW, WHERE VFR CONDITIONS
WILL PREVAIL UNTIL AFTER 03Z. SHOWERS WILL MOSTLY PUSH EAST OF THE
AREA THIS EVENING, WITH SHOWERS DIMINISHING IN COVERAGE.
ABUNDANT LOW-LEVEL MOISTURE WILL ALLOW FOR IFR CEILINGS TO LOWER
TO LIFR OVERNIGHT AND FOR MVFR VISIBILITIES TO CONTINUE TO PREVAIL.
A FEW LINGERING SHOWERS CANNOT BE RULED OUT OVERNIGHT, ALTHOUGH DO
NOT EXPECT THE MORE PERSISTENT RAINFALL TO RETURN UNTIL CLOSER TO
DAWN ON WEDNESDAY.
A SURFACE LOW WILL PUSH INTO THE OHIO VALLEY ON WEDNESDAY AND ALLOW
FOR SHOWERS WITH IFR CEILINGS TO PREVAIL MUCH OF THE DAY. THERE
IS A CHANCE OF THUNDERSTORMS IN THE AFTERNOON ON WEDNESDAY AS WARM
AIR IS DRAWN INTO THE AREA AHEAD OF THE LOW.
OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY...
THE SURFACE LOW WILL PULL NORTHEAST OF THE AREA ON WEDNESDAY NIGHT
WITH SHOWERS ENDING. MVFR CEILINGS WILL CONTINUE TO PREVAIL
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT.
THE NEXT SURFACE LOW WILL MOVE FROM THE SOUTHEAST INTO THE MID-
ATLANTIC THURSDAY NIGHT INTO FRIDAY, BRINGING SHOWERS WITH
RESTRICTIONS TO THE TERMINALS SOUTHEAST OF KPIT. VFR CONDITIONS
WILL MOSTLY PREVAIL FRIDAY INTO SATURDAY. LOW CONFIDENCE FORECAST
FOR SUNDAY, WITH A CHANCE OF RAIN AND SNOW SHOWERS WITH
RESTRICTIONS.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS PITTSBURGH PA
1221 PM EST TUE DEC 20 2011
.SYNOPSIS...
A COLD FRONT STALLING ACROSS THE UPPER OHIO VALLEY WILL PROVIDE
RAIN TODAY. HOWEVER, THERE CAN BE A SHORT PERIOD OF WET SNOW THIS
MORNING NORTH OF PITTSBURGH. LOW PRESSURE, COMING NORTHEAST FROM TEXAS,
WILL BRING MILDER TEMPERATURES AND RAIN TONIGHT AND WEDNESDAY.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
UPDATED TO REMOVE MORNING WORDING.
PER RECENT RADAR AND SURFACE DATA, COUPLED WITH RECENT HRRR AND
NAM MODEL OUTPUT, EXPECT PRECIPITATION ACROSS THE ENTIRE UPPER
OHIO VALLEY INTO MIDDAY. RECENT SURFACE DATA SHOWS LOW
VISIBILITIES ACROSS HIGHER TERRAIN WHICH CAN AFFECT TRAVEL ON
I-68 AND PA TURNPIKE.
THE COLD FRONT MOVING SLOWLY SOUTH FROM THE I-80 CORRIDOR MAY
LOWER SURFACE TEMPERATURES ENOUGH TO CAUSE A CHANGE TO WET SNOW
FOR A TIME THIS MORNING AS FAR SOUTH AS COLUMBIANA COUNTY OHIO,
BEAVER COUNTY, NORTHERN ALLEGHENY COUNTY AND NORTHERN INDIANA
COUNTY PENNSYLVANIA...ALSO ACROSS THE HIGHER MOUNTAIN RIDGES
FARTHER SOUTH. RAIN-WETTED GROUND SHOULD RESULT IN MINIMAL SNOW
ACCUMULATION, IF ANY.
WILL ISSUE STATEMENT REGARDING THE POSSIBILITY OF ICY CONDITIONS
WHERE TEMPERATURES REACH THE FREEZING POINT NEAR THE I-80
CORRIDOR. WILL ALSO ISSUE A STATEMENT MENTIONING LOW VISIBILITIES
IN FOG FOR HIGHER TERRAIN SOUTH.
EXPECT TEMPERATURES TO BEGIN SLOWLY WARMING LATER THIS MORNING, AS POSTFRONTAL
NORTH WINDS ABATE BEHIND THE STALLING COLD FRONT. THIS WILL
LIKEWISE ALLOW DAYTIME PROCESSES TO RAISE TEMPERATURES ALSO. HENCE
LOCATIONS WITH WET SNOW EARLY THIS MORNING SHOULD SEE IT END BY
MIDDAY. NAM MODEL OUTPUT SHOWS SOUTHEASTERLY WINDS INCREASE AHEAD
OF THE LOW PRESSURE CENTER INCOMING FROM TEXAS, CAUSING A SLOW
WARM UP INTO TONIGHT.
MODELS SHOW THERE MAY BE A BREAK IN THE RAIN SHOWERS EARLY TONIGHT, THEN
AN INCREASE IN RAIN SHOWER COVERAGE LATE TONIGHT AND DAYTIME
WEDNESDAY AS THE LOW PRESSURE CENTER PASSES NORTHEASTWARD THROUGH
OHIO.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
BLEND OF RECENT MODELS SHOWS SCATTERED POST-SYSTEM SHOWERS
CONTINUING IN THE WAKE OF THE EXITING LOW PRESSURE WEDNESDAY NIGHT.
A SECOND LOW PRESSURE SYSTEM, COMING NORTHEAST FROM LOUISIANA,
WILL PROVIDE SHOWERS THURSDAY NIGHT AND FRIDAY.
SOUTHWEST WINDS ALOFT WILL ENSURE TEMPERATURES REMAINING MILDER
THAN NORMAL, AS INDICATED BY RECENT GFS AND NAM MOS. THIS MILDNESS
WILL PREVENT ANY CHANGE TO WINTRY TYPE PRECIPITATION THIS PERIOD.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
MODELS IN FAIRLY GOOD AGREEMENT WITH SERIES OF SHORT WAVES RUNNING
ALONG THE NORTHERN PERIPHERY OF SUBTROPICAL RIDGE SATURDAY.
PROBLEM IS HOW MUCH PHASING WILL OCCUR...AND HOW FAR NORTH
PRECIPITATION WILL COME AS SURFACE LOWS MOVE ALONG THE FRONT IN
THE MID ATLANTIC STATES.
DID NOT STRAY TOO FAR FROM HPC GRIDS WITH BEST CHANCES OF PRECIP
SATURDAY INTO SUNDAY CHRISTMAS DAY. THERE CAN BE SUFFICIENT COOL
DOWN TO PROVIDE A CHANCE OF MIXED RAIN AND SNOW SHOWERS SOUTH
WITH SNOW SHOWERS IN THE NORTH.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
PER RECENT SURFACE AND RADAR DATA, ALONG WITH HRRR MODEL OUTPUT,
FOR TAF SITES SOUTH OF KFKL AND KDUJ, EXPECT MVFR RAIN AND FOG WITH
SOME INTERLUDES OF IFR THROUGH 16Z. FOR KFKL AND KDUJ, THERE CAN
BE A PERIOD OF IFR SNOW AND FOG THROUGH 16Z.
WITH THE FRONT THEN RETREATING NORTHWARD THIS AFTERNOON, EXPECT
THE RAIN TO DECREASE IN COVERAGE INTO EARLY TONIGHT WITH FLIGHT
CONDITIONS MAINLY MVFR ALL LOCATIONS.
LOW PRESSURE CENTER MOVING NORTHEASTWARD FROM TEXAS TODAY THROUGH
OHIO WEDNESDAY, WILL PROVIDE FREQUENT RAIN SHOWERS LATE TONIGHT
AND DAYTIME WEDNESDAY. THIS WILL LIKELY CAUSE ADDITIONAL BOUTS OF
IFR RESTRICTIONS.
OUTLOOK...WEDNESDAY NIGHT THROUGH SATURDAY...
MVFR WEDNESDAY NIGHT IN LINGERING POST SYSTEM SHOWERS AND CLOUDS
CAN GIVE WAY TO VFR THURSDAY. THE POTENTIAL FOR RESTRICTIONS
THEN RETURNS WITH MIXED PRECIPITATION FRIDAY AND SATURDAY.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1232 PM EST TUE DEC 20 2011
UPDATED AVIATION DISCUSSION FOR THE 18Z TAFS
.DISCUSSION /TODAY THROUGH MONDAY/... ISSUED AT 411 AM EST
UPPER TROUGH EXITING THE AREA THIS MORNING...PLACING THE AREA UNDER
MORE ZONAL FLOW THROUGH TONIGHT. AT THE SFC...LOW MOVING THROUGH
HUDSON BAY TODAY WILL PUSH A COLD FRONT THROUGH SRN CANADA.
INCREASING GRADIENT AHEAD OF THE FRONT WILL INCREASE WSW WINDS OVER
THE CWA...ESPECIALLY OVER WRN LK SUPERIOR. H925 WINDS /JUST BELOW
THE INVERSION/ SHOULD INCREASE TO 35-40KTS OVER WRN LK SUPERIOR AND
25-30KTS OVER MUCH OF THE CWA. WITH EXPECTED MIXING TOWARDS THAT
LEVEL THIS AFTN WITH MORE SUN...WILL BE BREEZY AT TIMES THIS AFTN
WITH GUSTS TO 25-30MPH...ESPECIALLY NEAR LK SUPERIOR.
PESKY LOW CLOUDS WILL BE THE SHORT TERM FCST CONCERN...AS MODELS
CONTINUE TO STRUGGLE EVEN ACKNOWLEDGING CLOUDS BEING PRESENT. THE
INCREASING H925 WINDS SHOULD HELP PUSH THE LOW CLOUDS NE AND ALSO
AID IN MIXING INTO DRIER AIR ALOFT AND FROM THE WSW. DOWNSLOPING SW
WINDS ALREADY STARTING TO BREAK UP CLOUDS OVER NCNTRL UPPER MI AND
EXPECT THAT TO CONTINUE INTO THE MORNING. RUC STILL LOOKS TO HAVE
THE BEST HANDLE ON THE CLOUDS...AND 06Z RUNS HAVE IT DIMINISHING BY
MID DAY. LLVL WINDS OFF COOLER LK MI WILL LIKELY KEEP CLOUDS HANGING
ON LONGER OVER THE E. IN ADDITION...WITH H850 TEMPS AROUND -9C
CREATING DELTA-T VALUES OF 16 OVER LK MI WILL KEEP LK ENHANCED
CLOUDS OVER FAR SE LUCE/SCHOOLCRAFT COUNTIES THROUGH MUCH OF THE
DAY.
ONCE THE CLOUDS EXIT THE AREA...SHOULD BE A NICE LATE DECEMBER AFTN
WITH PARTLY/MOSTLY SUNNY SKIES /ALTHOUGH A FEW MID CLOUDS COULD PUSH
SE OVER NRN LK SUPERIOR AND AFFECT THE KEWEENAW/ AND HIGHS IN THE
UPPER 20S AND LOWER 30S.
UPPER LOW ASSOCIATED WITH STRONG WINTER STORM IN THE LEE OF THE
CNTRL/SRN ROCKIES WILL SHIFT NE TONIGHT AND MOVE THROUGH THE LOWER
GREAT LAKES ON WED INTO WED NIGHT. WITH THIS SYSTEM PUSHING NE AND
SFC FRONT SLOWLY DROPPING SE THROUGH CANADA AND TOWARDS THE U.S.
BORDER...EXPECT A PORTION OF THE AREA TO BE UNDER THE PINCHED DRY
AIR BETWEEN THE SYSTEMS. LATEST TRENDS IN THE MODELS PUT THIS MORE
OVER THE SE CWA TONIGHT...WHILE THE NW HALF IS UNDER THE INCREASING
CLOUDS WITH THE APPROACHING SFC TROUGH. EXPECT THE CLOUDS TO
CONTINUE SE SLOWLY DURING THE DAY ON WED AS THE SFC TROUGH CONTINUES
IT/S SE PUSH.
PCPN CHANCES INCREASE AS THE SFC TROUGH PUSHES THROUGH LATE WED
NIGHT AND CHANCES WILL CONTINUE ON THURS AS LES DEVELOPS. H850 TEMPS
SHOULD FALL FROM -7C AT 06Z THURS TO -13C AT 18Z AND PUSH DELTA-T
VALUES TOWARDS 17. AS THE COLDER AIR ARRIVES...DEEPER MOISTURE EXITS
AND H850-700 SUBSIDENCE INCREASES /ESPECIALLY IN THE AFTN/...WHICH
CAUSES INVERSION HEIGHTS TO FALL TOWARDS 3-4KFT. THUS...POTENTIAL
FOR MUCH MORE THAT A INCH OR TWO OF LES IS LIMITED ON THURS. DID
BUMP POPS UP SOME FOR THURS FOR THE NNW WIND LOCATIONS...BUT STILL
ONLY PEAKED IT OUT IN THE MID-UPPER CHANCE AREA. ALSO BUMPED UP POPS
SOME FOR THURS NIGHT...TO CHANCES OVER THE E...SINCE LES WILL LIKELY
BE ONGOING AND BEST MOISTURE LOOKS TO BE THERE. WRN CWA IS A LITTLE
MORE UNCERTAIN WITH SFC RIDGE AND DRYING ARRIVING THROUGH THE NIGHT.
WILL GO WITH SLIGHTS FOR MOST OF THE N WIND FAVORED
LOCATIONS...THOUGH WILL GO WITH SOME CHANCES IN THE EVENING OVER THE
HIGHER TERRAIN LOCATIONS.
UPPER TROUGH IN THE NRN STREAM WILL DROP SE OUT OF THE CANADIAN
ROCKIES ON WED AND THROUGH THE UPPER GREAT LAKES THURS THROUGH FRI.
STILL SOME DIFFERENCES IN THE MODELS ON POTENTIALLY CLOSING OFF THE
SRN EXTENT OF THE UPPER TROUGH OVER THE CNTRL PLAINS FRI...WHICH
WOULD ALLOW WEAK UPPER RIDGING TO MOVE INTO THE WRN GREAT LKS
EARLIER ON FRI NIGHT AND CONTINUE INTO SAT. EITHER WAY...CWA WILL
LIKELY BE BETWEEN SYSTEMS AND HAVE SFC HIGH OVER THE AREA FRI NIGHT
INTO SAT.
EXPECT LINGERING LES TO DIMINISH AND PUSH OFFSHORE OVER THE ERN CWA
ON FRI...AS H850 WAA PUSHES TEMPS TOWARDS -8C AND LLVL WINDS BACK TO
THE WSW. AT THE SAME TIME SHORTWAVE MOVING THROUGH THE NRN STREAM IN
CNTRL/NRN ONTARIO SHOULD ONLY BRUSH HIGH CLOUDS OVER NRN LK
SUPERIOR...ALTHOUGH 00Z GFS/GEM HAS TRENDED FARTHER S WITH WITH WAVE
AND BRUSHES PCPN OVER NRN LK SUPERIOR. SWRLY FLOW AND DRY AIR ALOFT
SHOULD KEEP TEMPS IN CHECK WITH CLEAR SKIES ON FRI NIGHT AND WILL GO
WITH ABOVE NORMAL LOWS. DRY AIR ABOVE THE STRONG INVERSION AROUND
H925 SHOULD KEEP SKIES MOSTLY SUNNY ON SAT OTHER THAN SOME PASSING
HIGH CLOUDS. TEMPS ARE UNCERTAIN THIS FAR OUT AND WILL LEAN TOWARDS
A CONSENSUS FOR HIGHS. THAT BEING SAID...CLEAR SKIES AND SW WINDS
FAVOR WARMER TEMPS IN DOWNSLOPE AREAS NEAR LK SUPERIOR...SO DID
ADJUST THOSE AREAS UP A FEW DEGREES.
NRN STREAM TROUGH IS STILL SHOWN ON THE EXTENDED MODELS TO AFFECT
THE AREA SUN INTO MON. SFC TROUGH ASSOCIATED WITH LOW MOVING THROUGH
HUDSON BAY SHOULD DRAG A SFC TROUGH ACROSS THE CWA SAT NIGHT OR SUN
/12Z ECMWF AND 00Z GEM ARE THE FASTER SOLNS/. AS HAS BEEN THE CASE
WITH THE SERIES OF NRN STREAM WAVES...MOISTURE/FORCING ALONG THE
FRONT APPEARS TO BE LIMITED SO WILL CONTINUE SLIGHTS/LOW CHANCES
WITH THE FRONTAL PASSAGE. H850 TEMPS AROUND -15C AND POST FRONTAL
LLVL MOISTURE SHOULD LEAD TO LES IN NW WIND FAVORED LOCATIONS SUN
AND BUMPED UP POPS FROM THE CONSENSUS AND WILL CONTINUE CHANCE POPS
THROUGH SUN NIGHT. 00Z GFS SOUNDINGS WOULD SUPPORT A CHANCE OF
SEEING AT LEAST FEW INCHES OF SNOW ACCUMULATIONS NNW SNOWBELTS FOR
XMAS AFTN/EVENING. ECMWF ON THE OTHERHAND QUICKLY PULLS DRIER AIR
INTO THE REGION SUN AFTN/NIGHT WITH THE ARRIVAL OF THE SFC RIDGE.
ANOTHER NRN STREAM SHORTWAVE WAVE LOOKS TO BRUSH LK SUPERIOR ON
MN...BUT WITH OVERALL WEAK WAVE AND LIMITED MOISTURE WILL ONLY GO
SLIGHT POPS.
&&
.AVIATION /FOR THE 18Z TAF ISSUANCE/...
MVFR CIGS HAVE LIFTED FROM KSAW AND WOULD EXPECT VFR CONDITIONS TO
PERSIST THRU ALL TAF SITES THROUGH THE END OF THIS FCST PERIOD.
TIGHTENING PRES GRADIENT TODAY WILL RESULT IN GUSTY SW WINDS TO
AROUND 25KT. EXPECT LLWS TO DEVELOP THIS EVENING AS WINDS DECOUPLE
SOMEWHAT. LOOK FOR SOME LOWER VFR CIGS 4-5KFT TO MOVE INTO KIWD AND
KCMX BY LATE WED MORNING AS WINDS SHIFT WRLY BEHIND COLD FRONTAL
PASSAGE.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
DEEP LOW PRES MOVING E TO HUDSON BAY WILL BRING ANOTHER ROUND OF SW
GALES TO MUCH OF LAKE SUPERIOR TODAY THRU THIS EVENING. SW WIND
DIRECTION WILL FAVOR THE AREA BTWN THE KEWEENAW AND ISLE ROYALE FOR
STRONGEST WINDS (GUSTS TO 40-45KT). GALES WILL END LATER TONIGHT
AS PRES GRADIENT WEAKENS. WINDS WILL BE BLO 25KT WED THRU FRI THOUGH
THERE MAY BE A PERIOD OF 20-30KT WINDS OVER CNTRL LAKE SUPERIOR THU
MORNING IN THE WAKE OF A PASSING COLD FRONT. ANOTHER LOW PRES SYSTEM
TRACKING E TO HUDSON BAY COULD BRING A PERIOD OF SW WINDS UP TO 30KT
OVER PORTIONS OF WEST AND NCNTRL LAKE SUPERIOR LATE FRI NIGHT INTO
SAT.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...
GALE WARNING FROM 1 PM THIS AFTERNOON TO 1 AM EST WEDNESDAY FOR
LSZ267.
GALE WARNING FROM 9 AM THIS MORNING TO 1 AM EST WEDNESDAY FOR
LSZ266.
GALE WARNING UNTIL MIDNIGHT EST /11 PM CST/ TONIGHT FOR LSZ162.
GALE WARNING UNTIL 3 AM EST WEDNESDAY FOR LSZ263-264.
LAKE MICHIGAN...NONE.
&&
$$
DISCUSSION...SRF
AVIATION...VOSS
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS KANSAS CITY/PLEASANT HILL MO
1201 PM CST TUE DEC 20 2011
...UPDATED AVIATION DISCUSSION...
.DISCUSSION...
Relatively warm boundary layer temperatures and a marginal
temperatures aloft for ice crystals over nw MO is making it
difficult to generate much in the way of snow. Instead we are left
with a wintry mix...and a light mix at that. Calls around to local
law enforcement indicate no impacts from ongoing weather and with
air temperatures expected to remain status quo or even inch up a
degree or two any snow which falls will most likely accumulate
mainly on grassy areas. With that in mind and only minor snow/sleet
accumulations forecast have opted to drop the winter weather
advisory.
MJ
&&
.PREV DISCUSSION...
/346 AM CST Tue Dec 20 2011/
In the short term a classic panhandle low continues to accomplish
what it often does for this portion of the region, that is, sending
copious amount of moisture northward and creating a headache for
winter precipitation forecasts.
Early this morning, expansive dry slot is now rapidly lifting
northeast and across eastern Kansas and western Missouri. With
satellite imagery indicating the loss of ice crystals we`re also
slowly losing much of our precipitation across the region. However,
during the past 18 hours extensive northward moisture transport
resulting in PWAT values nearly 1" (or within the 99th percentile
for this time of the year) and efficient rain processes have
produced near record rainfall in the local area. The result of
nearly 1-1.5" of rain will be the flooding of several rivers in
central Missouri. Further north, a more problematic forecast
persists as a tight moisture gradient has formed over extreme
northern Missouri thanks to Canadian high pressure over the Dakotas
and strong dry air advection behind a departing northern stream
trough in the Western Great Lakes. 00z OAX/DVN soundings confirmed
the extent of this moisture disparity, which is resulting in a
overall lack of precipitation reaching the ground despite the
extensive areal coverage of radar echoes. Thus, snowfall totals have
been severely hampered over NE Kansas and NW Missouri with isolated
totals of a half inch in some locations.
For today, following much of the guidance from the suite of
mesoscale models which have a reasonable handle on the current
situation. The 00z NMM, 06z NAM, and RUC are the most reasonable
solutions at this time. As dry slot rotates through the area, precip
will continue to diminish through 15z, with lingering activity
mainly in the northern zones. Soundings continue to support a mix of
snow/sleet and perhaps rain in and along the Highway 36 corridor.
Given the absence of ice crystals would also be concerned for a bit
of freezing drizzle. By the middle to late morning hours, we should
also begin to see the expansive deformation zone in southwestern
Kansas begin to lift northeast towards the area. However, as the
upper low begins to eject eastward, support for heavy precipitation
will diminish as in tandem the favorable upper jet streak and rich
moisture feed both shift eastward. Feel model qpf may be a bit too
high given the lack of ice aloft, but soundings similar to these have
produced periods of light rain/drizzle/sleet or even snow showers
before, just usually very light in nature. The best chance for any
wintry precip will remain in the northwestern third of the CWA with
little accumulation. Further south would expect more drizzle or light
rain showers than anything. Will continue with the advisory for now
given potential for some development, but feel impacts may be much
lower than earlier thought.
Tonight, as mentioned in previous discussion, models continue to
hint at an area of low static stability most likely tied to an
individual vort lobe rotating around the upper low. Mesoscale model
output remains consistent in bringing a pocket of strong omega,
non-coincident with the aforementioned deformation zone, through
southern Kansas and into portions of central Missouri. Soundings and
cross sections through this layer suggest that with rather high
freezing levels, would expect mainly a patch of light to moderate
rain showers. Would also not be surprised to see a rumble or two
of thunder, but confidence not high enough to include. It is
theoretically possible that there could be enough dynamical cooling
within this locally intensifying vort lobe to produce a very quick
batch of heavy snow. Once again, not a certain forecast at all. Of
more concern is the potential that if roads and paved surfaces cannot
dry out by nighttime as colder air arrives, a period of black ice may
be possible heading into Wednesday morning.
Wednesday: The region will quickly transition to a zonal or
southwest flow pattern aloft for Wednesday as energy again digs into
the southwestern United States. Given the lack of snowcover except
in the NW CWA and modest southwest low level flow have bumped up
high temperatures a category or two in most locations.
For Thursday: Secondary upper trough emanating out of the Southwest
will quickly race into the region on Thursday. The southerly track
of this wave will hold moisture well south of the CWA with a weak
surface ridge axis bisecting the area.
31
Thursday through Tuesday...
Models have been trending toward a slightly stronger system for
Thursday night and Friday. However, there is still some difficulty
with respect to interactions between the Northern Plains shortwave
trough. Regardless, since moisture is limited will keep the threat
of snow in the low chance category. Otherwise, for the rest of the
period, it will remain rather quiet with only weak shortwaves in
basically dry northwest upper flow.
DB
&&
.AVIATION...
For the 18Z TAFs, above freezing temperatures near the surface and a
lack of ice crystals aloft will result in intermittent drizzle into
the early evening with a period or tow of sleet mixed in between
KMCI and KSTJ. A weakening deformation zone with snow will move east
this evening into far western MO but a lack of cold air should
result in only a brief period or two of a rain/snow mix for
KMCI/KMKC while KSTJ stands a better chance of all snow. However,
only minor snow accumulations possible in KSTJ...half an inch or
less...and little if any accumulation for the KC terminals. Plenty
of residual low level moisture around indicates LIFR/IFR cigs even
after all of the precipitation moves east by midnight.
Winds will back to the southwest on Wednesday and the low stratus
will scatter out quickly by mid morning with VFR conditions.
MJ
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&
$$
WFO EAX
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
600 PM EST TUE DEC 20 2011
.SYNOPSIS...
A COLD FRONT WILL SLOWLY APPROACH THE AREA WEDNESDAY AND THURSDAY
...THEN STALL ACROSS THE AREA THROUGH THE WEEKEND. WAVES OF LOW
PRESSURE WILL RIDE ALONG THIS FRONT...RESULTING WITH INCREASING
CHANCES FOR PRECIPITATION. THE PROSPECTS FOR MEASURABLE RAINFALL
WILL INCREASE AS THE WEEK PROGRESSES WITH THE BEST CHANCE EARLY IN
THE WEEKEND. HIGH PRESSURE WILL FINALLY REACH THE AREA EARLY IN THE
NEW WORK WEEK.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AS OF 545 PM TUESDAY...HAVE INCREASED CLOUD COVER ACROSS ALL OF THE
ILM CWA. THIS BASED ON LATEST SAT IMAGERY TRENDS AND THE LATEST 18Z
MODEL RUNS. LATEST HRRR KEEPS THE MAJORITY OF THE PCPN TONIGHT WEST
OF THE ILM CWA. BEST PCPN CHANCES ACROSS THE ILM CWA WILL OCCUR WEST
OF THE I-95 CORRIDOR. 5H S/W TROF AND ASSOCIATED UVVS MOVING
NE-WARD...WILL PASS IN CLOSE PROXIMITY TO WARRANT LOW CHANCE POPS
WELL INLAND. EAST OF I-95 AND TO THE COAST...ISOLATED -SHRA AT BEST.
WIDESPREAD 50S FOR LOWS LOOK GOOD EARLY IN THE NIGHT...WITH TEMPS
EITHER STEADY OR INCREASING SLIGHTLY AFTER MIDNIGHT DUE TO WAA AND
THE CLOUD COVER.
PREVIOUS DISCUSSION.............................................
AS OF 3 PM TUESDAY...LOW LEVEL ADVECTION OF WARM AND MOIST AIR AT
ODDS WITH MID LEVEL DRYNESS IN TRYING TO GENERATE PRECIPITATION
THROUGH THE PERIOD. MOST OF THE ADVECTION WILL JUST GO TO AN
INCREASE IN CLOUDINESS...ALTHOUGH SLIGHT CHANCE POPS CANNOT BE
RULED OUT. SUSPECT THAT NON-MEASURABLE SPRINKLES MORE LIKELY THAN
ANYTHING HIGHER. THE EXTENSIVE CLOUD COVER PAIRED WITH THE WAA
WILL KEEP LOWS EXCEPTIONALLY MILD...CLOSER TO NORMAL HIGH TEMPS
FOR THE SEASON...WITH READINGS GENERALLY IN THE MID 50S.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 3 PM TUESDAY...A LARGE AREA OF HIGH PRESSURE WILL BE CENTERED
ACROSS THE WESTERN ATLANTIC. THE WESTERN PERIPHERY OF THIS HIGH WILL
HANG ON ACROSS THE EASTERN CAROLINAS THROUGH THE MID-TERM. AT THE
SAME TIME...A VERY DEEP TROUGH WILL CARVE OUT ACROSS THE WESTERN
UNITED STATES. ONE AREA OF LOW PRESSURE WILL PASS WELL N OF THE AREA
ON WED AS ANOTHER AREA OF LOW PRESSURE EJECTS OUT OF THE FOUR
CORNERS REGION AND PASSES JUST N OF THE AREA THU AND THU NIGHT. AS
EACH ONE OF THESE SYSTEMS RIDE OVER THE TOP OF THE RIDGE THEY WILL
AID IN FLATTENING IT OUT...SETTING UP THE STAGE FOR PERHAPS SOME
MEANINGFUL RAIN JUST BEYOND THIS FORECAST PERIOD.
A DEEP AND WARM SW FLOW WILL KEEP CONDITIONS UNSETTLED THIS PERIOD
WITH CLOUDS DOMINATING THE SKY. WHILE MEASURABLE RAINFALL CAN NOT BE
RULED OUT AT ANY TIME DURING THIS PERIOD...AT THIS POINT IT IS VERY
DIFFICULT TO HONE IN ON A TIME WHEN THE CHANCE FOR SHOWERS WILL BE
HIGHEST. HOWEVER...WE WILL CARRY THE HIGHEST POPS LATER THU AND THU
NIGHT AS FOUR CORNERS LOW MAKES ITS CLOSEST APPROACH. HOWEVER...
AGAIN...TIMING IS VERY UNCERTAIN AT THIS POINT.
GIVEN DEWPOINTS IN THE LOWER TO MID 60S WILL BE ADVECTING
NORTHWARD...WE DO EXPECT PATCHY SEA FOG TO DEVELOP. GIVEN THE
TRAJECTORIES...SOME OF THIS FOG SHOULD SKIRT THE COASTAL AREAS...
ESPECIALLY ACROSS BRUNSWICK COUNTY. INTRODUCED PATCHY FOG ALONG THE
COAST FOR LATER WED S...SPREADING UP THE COAST WED NIGHT AND THU.
THIS FOG MAY EVENTUALLY GROW MORE WIDESPREAD AND DENSE AT THE COAST
AS WARM AND MOIST FLOW PERSISTS ACROSS THE COOL SHELF WATERS.
DAYTIME HIGHS AND LOWS WILL BE WELL ABOVE NORMAL THROUGH THE PERIOD.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 3 PM TUESDAY...MUCH OF THE PERIOD REMAINS UNSETTLED. A COLD
FRONT...LAYING PARALLEL TO FLOW ALOFT...WILL BE STALLED OVER THE
AREA FRI AND THEN JUST OFF THE COAST SAT/SUN. SEVERAL WEAK
SURFACE WAVES WILL TRAVEL NORTHEAST ALONG THE BOUNDARY. ADDITIONALLY
THERE WILL BE WEAK SHORTWAVES TRAVELING UP THE WESTERN SIDE OF THE
5H RIDGE DURING THE FIRST HALF OF THE PERIOD. TIMING THESE SUBTLE
FEATURES IS DIFFICULT AT BEST SO DID NOT MAKE A LOT OF CHANGES TO
POP GRIDS.
SUN INTO MON THE MEDIUM RANGE GUIDANCE STARTS TO DIVERGE. THE GFS
SHOWS A MORE PROGRESSIVE ZONAL PATTERN DEVELOPING WHILE THE
ECMWF/CANADIAN SHOW MORE AMPLIFICATION. THE RESULT OF THIS IS THE
GFS WANTS TO BRING IN ANOTHER SYSTEM BEFORE THE END OF THE PERIOD
WHILE THE ECMWF/CANADIAN SOLUTIONS DO NOT. THE SLOWER ECMWF SOLUTION
IS FAVORED WHICH KEEPS THE END OF THE PERIOD DRY.
TEMPERATURES ABOVE TO WELL ABOVE CLIMO CONTINUE INTO THE WEEKEND
DESPITE CLOUD COVER AND THREAT OF PRECIP. ONCE THE FRONT PUSHES OFF
THE COAST...SUN INTO MON...TEMPERATURES WILL DROP BELOW CLIMO
THROUGH THE END OF THE PERIOD.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 00Z...MOISTURE WILL BE ON THE INCREASE AS A COLD FRONT SLOWLY
APPROACHES THE REGION. MODERATE UNCERTAINTY WITH RESPECT TO CEILING
HEIGHTS OVERNIGHT. THE NAM IS THE MOST PESSIMISTIC...WITH IFR
PREDOMINATE AFTER MIDNIGHT. THINK THIS MAY BE OVERDONE...GIVEN THAT
IT ALSO SHOWING LOW VISIBILITIES. WILL GO WITH A LOW MVFR
CEILING...MAINLY AT THE INLAND TERMINALS.
DEEP MOISTURE MOVES INTO THE WESTERN CWA BY MIDDAY WEDNESDAY...WITH
A DECENT CHANCE FOR PRECIPITATION. ANY RAIN WILL LIKELY BY
LIGHT...WITH LITTLE REDUCTION IN VISIBILITY. LIKEWISE CEILINGS WILL
REMAIN MVFR TO VFR...WITH A LOT OF 4K CEILINGS NEAR THE SUBSIDENCE
INVERSION. SOUTHERLY GRADIENT WILL INCREASE...WITH GUSTY WINDS
EXPECTED BY LATE MORNING.
EXTENDED OUTLOOK...LOW CONFIDENCE IN MORNING FOG THURSDAY. MORE RAIN
WITH ASSOCIATED RESTRICTIONS POSSIBLE FRIDAY/SATURDAY. VFR EXPECTED
SUNDAY.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 545 PM TUESDAY...WAA UNDER S-SW WINDS WILL RULE TONIGHT.
LATEST NAM INDICATES WAA WINDS AT 925MB INCREASING TO 25-30 KT AFTER
MIDNIGHT THROUGH DAYBREAK WEDNESDAY. WITH SSTS ACROSS THE SHELF
WATERS IN THE 50S...THE HIGHER WINDS ALOFT WILL HAVE A DIFFICULT
TIME MIXING TO THE OCEAN SFC. AS A RESULT...WILL INDICATE S-SW WINDS
INCREASING ONLY TO 10-15 KT OVERNIGHT. SEAS 2 TO 3 FT...WILL
INCREASE ONLY TO 2 TO 4 FT...EXCEPT UP TO 5 FT ACROSS THE OUTER
WATERS OFF CAPE FEAR. THE INCREASE IN SEAS OVERNIGHT WILL MAINLY
COME FROM THE HIGHER WINDS AND RESULTANT SEAS OFFSHORE...WHERE SSTS
NEAR 70...BLEED INTO THE COASTAL WATERS.
PREVIOUS DISCUSSION...............................................
AS OF 3 PM TUESDAY...BERMUDA HIGH PRESSURE MORE TYPICAL OF WARM
SEASON TO REMAIN ANCHORED FIRMLY IN PLACE THROUGH THE PERIOD. WIND
WILL THUS BE SOUTHWESTERLY AND WILL TEND TO PICK UP INTO THE 10 TO
15 KT RANGE. THIS INCREASE IN WINDS WILL TRANSLATE INTO A SMALL
INCREASE IN SEAS. THE SOUTHWESTERLY FLOW IS LARGELY PARALLEL TO
THE COAST SO THE MOST SIGNIFICANT BUILDING OF SEAS...ABOUT A
FOOT...WILL BE WELL AWAY FROM SHORE WHILE THOSE NEAR SHORE BUILD
LESS. IN THE END A GENERAL 2 TO 4 FT RANGE IS EXPECTED FOR THE
OVERNIGHT PERIOD.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 3 PM TUESDAY...WINDS WILL BE FROM THE SW THROUGH THE PERIOD.
SW FLOW ALOFT WILL BE ROBUST WITH JETTING AT TIMES INCREASING WINDS
TO 40+ KT ALOFT. HOWEVER...THESE WINDS WILL NOT EFFICIENTLY MIX DOWN
GIVEN THE COOL WATER TEMPS...THUS WINDS THROUGH THE PERIOD SHOULD
NOT EXCEED 15 TO 20 KT. SEAS WILL NOT EXCEED 3 TO 5 FT.
AS DEWPOINTS IN THE LOWER TO MID 60S ADVECT ACROSS THE WATERS...
PATCHY SEA FOG IS EXPECTED TO DEVELOP ACROSS THE SOUTHERN WATERS WED
AFTERNOON AND THEN SPREAD N THROUGH THU. THE COVERAGE OF FOG MAY
INCREASE WITH TIME AND GROW DENSER AS WARM AND MOIST FLOW PERSISTS
ACROSS THE COOL SHELF WATERS.
LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 3 PM TUESDAY...STALLED FRONT IN THE VICINITY WILL KEEP WIND
DIRECTION FORECAST THROUGH THE PERIOD QUITE TRICKY. FRI THE FRONT
WILL BE WEST OF THE WATERS WITH SOUTHWEST FLOW IN PLACE. FRONT
SHIFTS OFFSHORE FRI NIGHT INTO SAT WITH LIGHT NORTHERLY FLOW
DEVELOPING. FRONT REMAINS STALLED JUST OFF THE COAST THROUGH THE
END OF THE PERIOD...WITH SPEEDS 10 TO 15 KT. SEAS WILL RUN 3 TO 5
FT THROUGH THE PERIOD.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.
&&
$$
NEAR TERM...DCH/MBB
SHORT TERM...RJD
LONG TERM...III
AVIATION...43
AREA FORECAST DISCUSSION
NWS WILMINGTON NC
545 PM EST TUE DEC 20 2011
.SYNOPSIS...
A COLD FRONT WILL SLOWLY APPROACH THE AREA WEDNESDAY AND THURSDAY
...THEN STALL ACROSS THE AREA THROUGH THE WEEKEND. WAVES OF LOW
PRESSURE WILL RIDE ALONG THIS FRONT...RESULTING WITH INCREASING
CHANCES FOR PRECIPITATION. THE PROSPECTS FOR MEASURABLE RAINFALL
WILL INCREASE AS THE WEEK PROGRESSES WITH THE BEST CHANCE EARLY IN
THE WEEKEND. HIGH PRESSURE WILL FINALLY REACH THE AREA EARLY IN THE
NEW WORK WEEK.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AS OF 545 PM TUESDAY...HAVE INCREASED CLOUD COVER ACROSS ALL OF THE
ILM CWA. THIS BASED ON LATEST SAT IMAGERY TRENDS AND THE LATEST 18Z
MODEL RUNS. LATEST HRRR KEEPS THE MAJORITY OF THE PCPN TONIGHT WEST
OF THE ILM CWA. BEST PCPN CHANCES ACROSS THE ILM CWA WILL OCCUR WEST
OF THE I-95 CORRIDOR. 5H S/W TROF AND ASSOCIATED UVVS MOVING
NE-WARD...WILL PASS IN CLOSE PROXIMITY TO WARRANT LOW CHANCE POPS
WELL INLAND. EAST OF I-95 AND TO THE COAST...ISOLATED -SHRA AT BEST.
WIDESPREAD 50S FOR LOWS LOOK GOOD EARLY IN THE NIGHT...WITH TEMPS
EITHER STEADY OR INCREASING SLIGHTLY AFTER MIDNIGHT DUE TO WAA AND
THE CLOUD COVER.
PREVIOUS DISCUSSION.............................................
AS OF 3 PM TUESDAY...LOW LEVEL ADVECTION OF WARM AND MOIST AIR AT
ODDS WITH MID LEVEL DRYNESS IN TRYING TO GENERATE PRECIPITATION
THROUGH THE PERIOD. MOST OF THE ADVECTION WILL JUST GO TO AN
INCREASE IN CLOUDINESS...ALTHOUGH SLIGHT CHANCE POPS CANNOT BE
RULED OUT. SUSPECT THAT NON-MEASURABLE SPRINKLES MORE LIKELY THAN
ANYTHING HIGHER. THE EXTENSIVE CLOUD COVER PAIRED WITH THE WAA
WILL KEEP LOWS EXCEPTIONALLY MILD...CLOSER TO NORMAL HIGH TEMPS
FOR THE SEASON...WITH READINGS GENERALLY IN THE MID 50S.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 3 PM TUESDAY...A LARGE AREA OF HIGH PRESSURE WILL BE CENTERED
ACROSS THE WESTERN ATLANTIC. THE WESTERN PERIPHERY OF THIS HIGH WILL
HANG ON ACROSS THE EASTERN CAROLINAS THROUGH THE MID-TERM. AT THE
SAME TIME...A VERY DEEP TROUGH WILL CARVE OUT ACROSS THE WESTERN
UNITED STATES. ONE AREA OF LOW PRESSURE WILL PASS WELL N OF THE AREA
ON WED AS ANOTHER AREA OF LOW PRESSURE EJECTS OUT OF THE FOUR
CORNERS REGION AND PASSES JUST N OF THE AREA THU AND THU NIGHT. AS
EACH ONE OF THESE SYSTEMS RIDE OVER THE TOP OF THE RIDGE THEY WILL
AID IN FLATTENING IT OUT...SETTING UP THE STAGE FOR PERHAPS SOME
MEANINGFUL RAIN JUST BEYOND THIS FORECAST PERIOD.
A DEEP AND WARM SW FLOW WILL KEEP CONDITIONS UNSETTLED THIS PERIOD
WITH CLOUDS DOMINATING THE SKY. WHILE MEASURABLE RAINFALL CAN NOT BE
RULED OUT AT ANY TIME DURING THIS PERIOD...AT THIS POINT IT IS VERY
DIFFICULT TO HONE IN ON A TIME WHEN THE CHANCE FOR SHOWERS WILL BE
HIGHEST. HOWEVER...WE WILL CARRY THE HIGHEST POPS LATER THU AND THU
NIGHT AS FOUR CORNERS LOW MAKES ITS CLOSEST APPROACH. HOWEVER...
AGAIN...TIMING IS VERY UNCERTAIN AT THIS POINT.
GIVEN DEWPOINTS IN THE LOWER TO MID 60S WILL BE ADVECTING
NORTHWARD...WE DO EXPECT PATCHY SEA FOG TO DEVELOP. GIVEN THE
TRAJECTORIES...SOME OF THIS FOG SHOULD SKIRT THE COASTAL AREAS...
ESPECIALLY ACROSS BRUNSWICK COUNTY. INTRODUCED PATCHY FOG ALONG THE
COAST FOR LATER WED S...SPREADING UP THE COAST WED NIGHT AND THU.
THIS FOG MAY EVENTUALLY GROW MORE WIDESPREAD AND DENSE AT THE COAST
AS WARM AND MOIST FLOW PERSISTS ACROSS THE COOL SHELF WATERS.
DAYTIME HIGHS AND LOWS WILL BE WELL ABOVE NORMAL THROUGH THE PERIOD.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 3 PM TUESDAY...MUCH OF THE PERIOD REMAINS UNSETTLED. A COLD
FRONT...LAYING PARALLEL TO FLOW ALOFT...WILL BE STALLED OVER THE
AREA FRI AND THEN JUST OFF THE COAST SAT/SUN. SEVERAL WEAK
SURFACE WAVES WILL TRAVEL NORTHEAST ALONG THE BOUNDARY. ADDITIONALLY
THERE WILL BE WEAK SHORTWAVES TRAVELING UP THE WESTERN SIDE OF THE
5H RIDGE DURING THE FIRST HALF OF THE PERIOD. TIMING THESE SUBTLE
FEATURES IS DIFFICULT AT BEST SO DID NOT MAKE A LOT OF CHANGES TO
POP GRIDS.
SUN INTO MON THE MEDIUM RANGE GUIDANCE STARTS TO DIVERGE. THE GFS
SHOWS A MORE PROGRESSIVE ZONAL PATTERN DEVELOPING WHILE THE
ECMWF/CANADIAN SHOW MORE AMPLIFICATION. THE RESULT OF THIS IS THE
GFS WANTS TO BRING IN ANOTHER SYSTEM BEFORE THE END OF THE PERIOD
WHILE THE ECMWF/CANADIAN SOLUTIONS DO NOT. THE SLOWER ECMWF SOLUTION
IS FAVORED WHICH KEEPS THE END OF THE PERIOD DRY.
TEMPERATURES ABOVE TO WELL ABOVE CLIMO CONTINUE INTO THE WEEKEND
DESPITE CLOUD COVER AND THREAT OF PRECIP. ONCE THE FRONT PUSHES OFF
THE COAST...SUN INTO MON...TEMPERATURES WILL DROP BELOW CLIMO
THROUGH THE END OF THE PERIOD.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
AS OF 18Z...EXPECT VFR CONDITIONS TO PERSIST INTO THE OVERNIGHT
HOURS ON W-SW FLOW OF 5 TO 10 KT. S TO SW FLOW AHEAD OF AN
APPROACHING COLD FRONT COULD BRING SCATTERED SHOWERS TO THE AREA
AFTER 00Z BUT THE PROBABILITY LOOKS TOO LOW TO INCLUDE IN THE TAFS
PRESENTLY. THERE IS SOME POTENTIAL FOR AN IFR STRATUS EVENT
TONIGHT...ESPECIALLY AT INLAND TERMINALS. WINDS OVERNIGHT WILL
BECOME SOUTHERLY AND DECREASE TO 3-6 KTS. SHOWERS REMAIN POSSIBLE
ALL AREAS AFTER 12Z WITH MVFR CIGS EXPECTED AT ALL TERMINALS.
SHOWERS WERE ONLY INCLUDED AT INLAND TAF SITES IN THE 12 TO 18Z
WINDOW AS THE PROBABILITY IS HIGHEST AT THOSE TERMINALS.
EXTENDED OUTLOOK...LOW CONFIDENCE IN MORNING FOG THURSDAY. MORE RAIN
WITH ASSOCIATED RESTRICTIONS POSSIBLE FRIDAY/SATURDAY. VFR EXPECTED
SUNDAY.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 545 PM TUESDAY...WAA UNDER S-SW WINDS WILL RULE TONIGHT.
LATEST NAM INDICATES WAA WINDS AT 925MB INCREASING TO 25-30 KT AFTER
MIDNIGHT THROUGH DAYBREAK WEDNESDAY. WITH SSTS ACROSS THE SHELF
WATERS IN THE 50S...THE HIGHER WINDS ALOFT WILL HAVE A DIFFICULT
TIME MIXING TO THE OCEAN SFC. AS A RESULT...WILL INDICATE S-SW WINDS
INCREASING ONLY TO 10-15 KT OVERNIGHT. SEAS 2 TO 3 FT...WILL
INCREASE ONLY TO 2 TO 4 FT...EXCEPT UP TO 5 FT ACROSS THE OUTER
WATERS OFF CAPE FEAR. THE INCREASE IN SEAS OVERNIGHT WILL MAINLY
COME FROM THE HIGHER WINDS AND RESULTANT SEAS OFFSHORE...WHERE SSTS
NEAR 70...BLEED INTO THE COASTAL WATERS.
PREVIOUS DISCUSSION...............................................
AS OF 3 PM TUESDAY...BERMUDA HIGH PRESSURE MORE TYPICAL OF WARM
SEASON TO REMAIN ANCHORED FIRMLY IN PLACE THROUGH THE PERIOD. WIND
WILL THUS BE SOUTHWESTERLY AND WILL TEND TO PICK UP INTO THE 10 TO
15 KT RANGE. THIS INCREASE IN WINDS WILL TRANSLATE INTO A SMALL
INCREASE IN SEAS. THE SOUTHWESTERLY FLOW IS LARGELY PARALLEL TO
THE COAST SO THE MOST SIGNIFICANT BUILDING OF SEAS...ABOUT A
FOOT...WILL BE WELL AWAY FROM SHORE WHILE THOSE NEAR SHORE BUILD
LESS. IN THE END A GENERAL 2 TO 4 FT RANGE IS EXPECTED FOR THE
OVERNIGHT PERIOD.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 3 PM TUESDAY...WINDS WILL BE FROM THE SW THROUGH THE PERIOD.
SW FLOW ALOFT WILL BE ROBUST WITH JETTING AT TIMES INCREASING WINDS
TO 40+ KT ALOFT. HOWEVER...THESE WINDS WILL NOT EFFICIENTLY MIX DOWN
GIVEN THE COOL WATER TEMPS...THUS WINDS THROUGH THE PERIOD SHOULD
NOT EXCEED 15 TO 20 KT. SEAS WILL NOT EXCEED 3 TO 5 FT.
AS DEWPOINTS IN THE LOWER TO MID 60S ADVECT ACROSS THE WATERS...
PATCHY SEA FOG IS EXPECTED TO DEVELOP ACROSS THE SOUTHERN WATERS WED
AFTERNOON AND THEN SPREAD N THROUGH THU. THE COVERAGE OF FOG MAY
INCREASE WITH TIME AND GROW DENSER AS WARM AND MOIST FLOW PERSISTS
ACROSS THE COOL SHELF WATERS.
LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 3 PM TUESDAY...STALLED FRONT IN THE VICINITY WILL KEEP WIND
DIRECTION FORECAST THROUGH THE PERIOD QUITE TRICKY. FRI THE FRONT
WILL BE WEST OF THE WATERS WITH SOUTHWEST FLOW IN PLACE. FRONT
SHIFTS OFFSHORE FRI NIGHT INTO SAT WITH LIGHT NORTHERLY FLOW
DEVELOPING. FRONT REMAINS STALLED JUST OFF THE COAST THROUGH THE
END OF THE PERIOD...WITH SPEEDS 10 TO 15 KT. SEAS WILL RUN 3 TO 5
FT THROUGH THE PERIOD.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.
&&
$$
NEAR TERM...DCH/MBB
SHORT TERM...RJD
LONG TERM...III
AVIATION...RAN
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
402 PM EST TUE DEC 20 2011
.SYNOPSIS...
A COLD FRONT STALLED ACROSS THE MASON DIXON LINE WILL SLOWLY
LIFT NORTH AS A WARM FRONT TONIGHT AND WEDNESDAY. THIS WILL
PRODUCE PERIODS OF LIGHT RAIN OR DRIZZLE INTO THE EVENING HOURS.
LOW PRESSURE WILL MOVE THRU THE EASTERN GREAT LAKES ON
WEDNESDAY EVENTUALLY DRAGGING A COLD FRONT ACROSS THE REGION.
HIGH PRESSURE WILL MOVE INTO THE AREA ON THURSDAY FOLLOWED BY
MORE UNSETTLED WEATHER FOR LATE IN THE WEEK AND POTENTIALLY THE
CHRISTMAS WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
LATEST SFC ANALYSIS INDICATES A STALLED FRONT ALONG OR JUST SOUTH
OF THE MASON-DIXON LINE WITH LIGHT OVERRUNNING PRECIP STREAKING
EAST ACROSS MUCH OF MY FCST AREA. ANYTHING THAT FALLS OVER THE FAR
NORTH WHERE TEMPS ARE STILL CLOSE TO FREEZING MAY FALL AS
SNOW...BUT OVER MOST OF THE REGION WE ARE SEEING MAINLY LIGHT RAIN
OR DRIZZLE.
LATEST NAM AND HRRR SHOW A CHUNK OF LIGHT PRECIP BETWEEN NOW AND
ROUGHLY 00Z...WHEN ACTIVITY IS MADE TO TAPER OFF AND BECOME MORE
SCATTERED IN NATURE.
FROM THERE THE SREF AND NEW 12Z NAM/GFS DEVELOP ANOTHER SURGE OF
PRECIPITATION FOR THE AFTER MIDNIGHT PERIOD AS THE LEFT EXIT
REGION OF THE UPPER JET STARTS TO NOSE INTO THE REGION. THE
FORECAST GETS A LITTLE TRICKY OVER THE NORTHERN MOUNTAINS WHERE
SOME COLDER SPOTS COULD BOTTOM OUT JUST UNDER FREEZING. THIS WILL
CREATE THE POTENTIAL FOR A PERIOD OF LIGHT FREEZING RAIN OR DRIZZLE
BEFORE THE WARM ADVECTION WARMS UP ALL LOCATIONS LATER TONIGHT AND
EARLY WED. AT THIS POINT CONFIDENCE IS TOO LOW TO ISSUE ANY
HEADLINE PRODUCTS...BUT FOR NOW THE POTENTIAL HAS BEEN ADDRESSED
IN THE HWO.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
WED WILL SEE THE APPROACH OF A FAIRLY VIGOROUS MID LEVEL
SHORTWAVE AND ASSOCIATED SFC FRONTAL SYSTEM.
MODELS ARE QUICK TO ERODE STABILITY AS DEEP MOISTURE AND
INCREASING MID LEVEL LAPSE RATES SURGE INTO THE FCST AREA WITH THE
APPROACH OF THE LEFT EXIT REGION OF AN IMPRESSIVE MID/UPPER LEVEL
JET STREAK. WITH THE MODELS DEPICTING SOME RESPECTABLE CONVECTIVE
INSTABILITY...AND EVEN SOME INERTIAL INSTABILITY...CANNOT RULE OUT
EMBEDDED THUNDER AS THE SHORTWAVE AND FRONTAL SYSTEM MOVE THROUGH
DURING THE AFTERNOON AND EARLY EVENING.
LOW TO MID LEVEL WIND FIELDS WILL BE ON THE INCREASE THROUGHOUT
THE DAY AS THE UPPER WAVE BARRELS OUR WAY. SPC HAS THE REGION IN
THE "SEE TEXT" PORTION OF THE OUTLOOK ACKNOWLEDGING THE
POSSIBILITY OF STRONG WIND FIELDS BEING TAPPED BY THE CONVECTION
AND PERHAPS CAUSING LOCALLY DAMAGING WIND GUSTS.
AFTER SOME INITIAL COOL AIR DAMMING...HIGHS ARE EXPECTED TO MAKE
IT INTO THE 40S AND 50S...WHICH WILL BE WELL ABOVE MID DECEMBER
NORMALS.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
VERY ACTIVE SOUTHERN JET STREAM WILL CONTINUE A COMPLEX FORECAST
SCENARIO FOR THE MID ATLANTIC STATES THROUGH THE LONG TERM
PERIOD. MODEL GUIDANCE KEEPS THE MEAN UPPER TROF OVER THE WESTERN
U.S. THROUGH MUCH OF THE PD...WITH SWRLY FLOW DOMINATING THE
EASTERN HALF OF THE COUNTRY. NOT UNTIL MONDAY DOES THE ECMWF BRING A
PROGRESSIVE UPPER TROF INTO THE EASTERN U.S.
NUMEROUS SHORTWAVES WILL EJECT FROM THE SWRN UPPER TROF AND TRAVEL THROUGH
THE CENTER OF THE COUNTRY AND INTO OUR REGION. DURING THIS
FORECAST PD CURRENT TIMING BRINGS ONE WAVE/SFC LOW THROUGH ON
FRIDAY AND ANOTHER ON SUNDAY.
WHILE THE NORTHERN JET STREAM WILL ALSO BE ACTIVE...BRINGING
SHOTS OF COLD AIR TOWARD PA...THE DOMINANT SWRLY FLOW WILL LEAD TO
MOST PCPN BEING IN THE FORM OF RAIN. BEST CHANCE OF ANY SNOW FALL
WILL BE ON THE TAIL END OF EACH SYSTEM. WHAT HAD LOOKED LIKE A
SHOT A MEASURABLE SNOW PREVIOUSLY...FOR CHRISTMAS DAY...CONTINUES
TO BE IN QUESTION AS THIS MORNINGS ECMWF IS NOW SIGNIFICANTLY
WARMER AND THE GFS IS ALMOST COMPLETELY DRY.
AFTER CHRISTMAS IT LOOKS DRIER AND COOLER AS THE TRAIN OF SRN
STREAM WAVES TAKES A BREAK.
&&
.AVIATION /21Z TUESDAY THROUGH SUNDAY/...
A STALLED FRONTAL BOUNDARY STRETCHED ACROSS THE PA/MD LINE WILL
BEGIN TO SLOWLY LIFT BACK TO THE NORTH LATER THIS AFTERNOON. THE
ASSOCIATED CLOUDS WILL KEEP CIGS LOW ACROSS THE STATE. EXPECT
PROLONGED IFR/LIFR CIGS AND VISIBILITIES AT BFD AND JST THROUGHOUT
MOST OF THE DAY. ELSEWHERE LOOK FOR MVFR TO IFR CIGS 005-020. CIGS
WILL DROP AGAIN OVERNIGHT AND STAY LOW THROUGH THE REMAINDER OF THE
TAF PERIOD AS THE FRONT LIFTS AND ANOTHER LOW PRESSURE SYSTEM MOVES
INTO THE OHIO VALLEY ON WEDNESDAY. EXPECT MVFR TO IFR RESTRICTIONS
WEDNESDAY WITH WIDESPREAD -RA AND A CHANCE OF TS IN THE SOUTHERN
PART OF THE STATE.
OUTLOOK...
WED...MVFR TO IFR RESTRICTIONS LKLY. WDSPRD -RA/CHC OF TS SRN PA.
THUR...NO SIG WX. MVFR CIGS PSBL WEST.
THUR NGT...RESTRICTIONS PSBL IN RA/SN AS WAVE MOVES THROUGH SOUTHERN MID-ATLC.
FRI-SUN...MVR TO IFR RESTRICTIONS POSSIBLE AS ANOTHER SYSTEM MOVES
THROUGH THE REGION.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...LA CORTE/GARTNER
NEAR TERM...LA CORTE
SHORT TERM...LA CORTE
LONG TERM...DEVOIR/GARTNER
AVIATION...LA CORTE/STEINBUGL
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
111 PM EST TUE DEC 20 2011
.SYNOPSIS...
A COLD FRONT STALLED ACROSS THE MASON DIXON LINE WILL SLOWLY
LIFT NORTH AS A WARM FRONT TONIGHT AND WEDNESDAY. THIS WILL
PRODUCE PERIODS OF LIGHT RAIN OR DRIZZLE INTO THE EVENING HOURS.
LOW PRESSURE WILL MOVE THRU THE EASTERN GREAT LAKES ON
WEDNESDAY EVENTUALLY DRAGGING A COLD FRONT ACROSS THE REGION.
HIGH PRESSURE WILL MOVE INTO THE AREA ON THURSDAY FOLLOWED BY
MORE UNSETTLED WEATHER FOR LATE IN THE WEEK AND POTENTIALLY THE
CHRISTMAS WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
LATEST SFC ANALYSIS INDICATES A STALLED FRONT ALONG OR JUST SOUTH
OF THE MASON-DIXON LINE WITH LIGHT OVERRUNNING PRECIP STREAKING
EAST ACROSS MUCH OF MY FCST AREA. ANYTHING THAT FALLS OVER THE FAR
NORTH WHERE TEMPS ARE STILL CLOSE TO FREEZING MAY FALL AS
SNOW...BUT OVER MOST OF THE REGION WE ARE SEEING MAINLY LIGHT RAIN
OR DRIZZLE.
LATEST NAM AND HRRR SHOW A CHUNK OF LIGHT PRECIP BETWEEN NOW AND
ROUGHLY 00Z...WHEN ACTIVITY IS MADE TO TAPER OFF AND BECOME MORE
SCATTERED IN NATURE.
FROM THERE THE SREF AND NEW 12Z NAM/GFS DEVELOP ANOTHER SURGE OF
PRECIPITATION FOR THE AFTER MIDNIGHT PERIOD AS THE LEFT EXIT
REGION OF THE UPPER JET STARTS TO NOSE INTO THE REGION. THE
FORECAST GETS A LITTLE TRICKY OVER THE NORTHERN MOUNTAINS WHERE
SOME COLDER SPOTS COULD BOTTOM OUT JUST UNDER FREEZING. THIS WILL
CREATE THE POTENTIAL FOR A PERIOD OF LIGHT FREEZING RAIN OR DRIZZLE
BEFORE THE WARM ADVECTION WARMS UP ALL LOCATIONS LATER TONIGHT AND
EARLY WED. AT THIS POINT CONFIDENCE IS TOO LOW TO ISSUE ANY
HEADLINE PRODUCTS...BUT FOR NOW THE POTENTIAL HAS BEEN ADDRESSED
IN THE HWO.
&&
.SHORT TERM /WEDNESDAY/...
WED WILL SEE THE APPROACH OF A FAIRLY VIGOROUS MID LEVEL
SHORTWAVE AND ASSOCIATED SFC FRONTAL SYSTEM.
MODELS ARE QUICK TO ERODE STABILITY AS DEEP MOISTURE AND
INCREASING MID LEVEL LAPSE RATES SURGE INTO THE FCST AREA WITH THE
APPROACH OF THE LEFT EXIT REGION OF AN IMPRESSIVE MID/UPPER LEVEL
JET STREAK. WITH THE MODELS DEPICTING SOME RESPECTABLE CONVECTIVE
INSTABILITY...AND EVEN SOME INERTIAL INSTABILITY...CANNOT RULE OUT
EMBEDDED THUNDER AS THE SHORTWAVE AND FRONTAL SYSTEM MOVE THROUGH
DURING THE AFTERNOON AND EARLY EVENING.
LOW TO MID LEVEL WIND FIELDS WILL BE ON THE INCREASE THROUGHOUT
THE DAY AS THE UPPER WAVE BARRELS OUR WAY. SPC HAS THE REGION IN
THE "SEE TEXT" PORTION OF THE OUTLOOK ACKNOWLEDGING THE
POSSIBILITY OF STRONG WIND FIELDS BEING TAPPED BY THE CONVECTION
AND PERHAPS CAUSING LOCALLY DAMAGING WIND GUSTS.
AFTER SOME INITIAL COOL AIR DAMMING...HIGHS ARE EXPECTED TO MAKE
IT INTO THE 40S AND 50S...WHICH WILL BE WELL ABOVE MID DECEMBER
NORMALS.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
THE LONGER TERM WILL BE ACTIVE WITH NO FEWER THAN 3 WEATHER SYSTEMS
EJECTING FROM THE MEAN UPPER TROF POSITION OVER THE ROCKIES AND HIGH
PLAINS WEDNESDAY THROUGH SUNDAY. COLD AIR IS LACKING...KEEPING
PRECIPITATION TYPES MAINLY IN LIQUID FORM THROUGHOUT THE WEEK...BUT
COLDER AIR ON THE BACKSIDE OF EACH SYSTEM (ROUGHLY PASSING EVERY 1.5
DAYS) WILL BRING SOME CHANGEOVER TO SNOW SHOWER ACTIVITY.
MAIN CHANGES THIS MORNING BASED ON LATEST AVAILABLE GEFS PLUMES AND
OPERATIONAL RUNS/GUIDANCE WAS TO DECREASE EXTENT AND COVERAGE OF
MIXED PRECIPITATION DURING MIDWEEK. +8C TO +10C THERMAL RIDGE OVER
CENTRAL AND EASTERN PA WILL SUPPORT ISOLATED THUNDER WEDNESDAY
AFTERNOON AND LIKELY A NARROW COLD FRONTAL RAIN BAND. LATEST
GUIDANCE ALSO SUGGESTS THE COLD AIR BEHIND THIS SYSTEM FOR THURSDAY
IS NOT ALL THAT COLD...AND A CHANGEOVER MAY NOT EVEN OCCUR EVEN OVER
NORTHWEST PA...BEFORE THE NEXT SURGE OF WAA APPROACHES FROM THE
LOWER OHIO VALLEY AND CENTRAL APPALACHIANS LATE THURSDAY AND
THURSDAY NIGHT.
1026 MB TO 1028 MB SFC HIGH TRACKING EASTWARD FROM ONTARIO INTO
WESTERN QUEBEC LATE THURSDAY INTO FRIDAY WILL DIRECT COLDER AIR TO
THE EAST OF THE GREAT LAKES AND THERE MAY BE SOME MINOR ACCUMS ON
THE BACKSIDE OF THE SYSTEM OVER THE NORTHERN HALF OF CENTRAL PA AS
THE SFC LOW SCOOTS OFF OF THE MID ATLANTIC COASTLINE ON FRIDAY.
HIGH PRESSURE QUICKLY BUILDS EASTWARD ACROSS THE LOWER LAKES AND
INTO PA FRIDAY NIGHT AND FOR THE FIRST HALF OF SATURDAY BEFORE YET
ANOTHER WAVE OF LOW PRESSURE APPROACHES FROM THE SOUTHWEST LATE
CHRISTMAS EVE DAY. THIS TOO APPEARS TO BE MAINLY RAIN...ALTHOUGH
COLDER AIR WRAPPING AROUND THE STORM MAY AGAIN PROMOTE A CHANGE BACK
TO SNOW FOR CHRISTMAS MORNING. THERE IS SOME INDICATION THAT A MORE
PRONOUNCED LAKE EFFECT REGIME IS POSSIBLE FOR SUNDAY AND MONDAY AT
THE VERY END OF THE PERIOD...BUT THIS TOO IS LIKELY TO CHANGE AND
REMAINS A LOW CONFIDENCE SOLUTION AT THIS TIME.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
A STALLED FRONTAL BOUNDARY STRETCHED ACROSS THE PA/MD LINE WILL
BEGIN TO SLOWLY LIFT BACK TO THE NORTH LATER THIS AFTERNOON. THE
ASSOCIATED CLOUDS WILL KEEP CIGS LOW ACROSS THE STATE. EXPECT
PROLONGED IFR/LIFR CIGS AND VISIBILITIES AT BFD AND JST THROUGHOUT
MOST OF THE DAY. ELSEWHERE LOOK FOR MVFR TO IFR CIGS 005-020. CIGS
WILL DROP AGAIN OVERNIGHT AND STAY LOW THROUGH THE REMAINDER OF THE
TAF PERIOD AS THE FRONT LIFTS AND ANOTHER LOW PRESSURE SYSTEM MOVES
INTO THE OHIO VALLEY ON WEDNESDAY. EXPECT MVFR TO IFR RESTRICTIONS
WEDNESDAY WITH WIDESPREAD -RA AND A CHANCE OF TS IN THE SOUTHERN
PART OF THE STATE.
OUTLOOK...
WED...MVFR TO IFR RESTRICTIONS LKLY. WDSPRD -RA/CHC OF TS SRN PA.
THUR...NO SIG WX. MVFR CIGS PSBL WEST.
THUR NGT...RESTRICTIONS PSBL IN RA/SN AS WAVE MOVES THROUGH SOUTHERN MID-ATLC.
FRI-SUN...MVR TO IFR RESTRICTIONS POSSIBLE AS ANOTHER SYSTEM MOVES
THROUGH THE REGION.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...LA CORTE
NEAR TERM...LA CORTE
SHORT TERM...LA CORTE
LONG TERM...DEVOIR
AVIATION...LA CORTE/COLBERT
AREA FORECAST DISCUSSION...UPDATED
NWS SPOKANE WA
245 PM PST Tue Dec 20 2011
.SYNOPSIS...A cold front will sweep through the Inland Northwest from
the north late this afternoon and this evening. This system is not
expected to carry much snow, but it will bring decidedly cooler
temperatures to the region as well as improving ventilation
conditions. An active winter weather pattern is expected to
continue through the holiday weekend and into the first part of
next week.
&&
.DISCUSSION...
Tonight...Satellite imagery indicates an upper level trough over
British Columbia dropping southeast towards Eastern Washington and
North Idaho. Instability in the mid levels of the atmosphere will
increase significantly this evening as 500mb temps fall to near
-36C and 850-500mb lapse rates increase to 7-8 C/KM. However
moisture is limited with this trough, and with 850mb winds of
15-25 knots out of the west to northwest significant down slope
flow off the higher terrain of Northern Washington and British
Columbia is likely. This should keep the best chances for snow
showers over the Cascades, Central Panhandle Mountains, Blue
Mountains, and Camas Prairie. Low level up slope flow into the
Palouse may also result in a brief light accumulation. An area of
lift from a passing vort max will also increase chances for snow
showers in these areas. The Camas Prairie looks to be the most
favored in this flow pattern but even here models only generate
one to two tenths of liquid precipitation so snow accumulations
were kept near 2 inches with no highlights needed at this time.
The cool and dry advection tonight with this trough will weaken
the inversion and will bring erosion of the stratus layer
especially over the northern valleys...and down the Okanogan
Valley into the western Columbia Basin. Patchy fog may form once
stratus clears but with the boundary layer drying out confidence
is not high so for now left mention of the forecast. JW
Wednesday through Friday...Through this portion of the forecast an
upper level low will pass out of the forecast area Wednesday morning,
then the weather will be dominated by a flat ridge of high
pressure through Thursday after. This will be followed by a
weakening/splitting weather disturbance Thursday night and Friday.
Challenges through this portion of the forecast will be the
probably of fog/stratus development with high pressure over the
region. Also, while model guidance all show a weakening frontal
system Thursday night the GFS/SREF show some weakening and a
slower solution than the NAM/EC/GEM. So far this season slower and
splitting weather systems have been the way and will lean in that
direction, what ever solution verifies confidence is not high
that there will be much snow.
Wednesday through Thursday northwest-north flow will keep some
snow showers over the southeast zones through about mid day
Wednesday, otherwise a dry and cool flow will result in a dry
forecast. The northerly flow and resultant cold air advection
should me enough to mix out the surface inversion and the
fog/stratus that has been going with it. There will most likely be
some regeneration of the fog along warmer water sources Thursday
morning, but expect this to be shallow and patchy. Temperatures
will cool by several degrees and be just on the cool side of normal.
Thursday night and Friday upper level moisture ahead of the
upstream weather system will move over the ridge. This should help
inhibit radiational cooling and keep the inversion from
strengthening any further. Model guidance is showing differing
solutions, but this trough passage is far from impressive. Some
isentropic ascent and upper level moisture is expected to track
through southern BC and will bring some light snow to the Cascade
crest and the northern mountains. Up-sloping will increase the
lift over the panhandle mountains, but with little moisture to
work with any snow accumulations will be very light. The following
cold front is almost non-existent at the surface but may be marginally
successful in keeping the boundary layer mixed. /Tobin
FRI NT THROUGH TUES: SIGNIFICANT CHALLENGES STILL EXIST AS A RESULT
OF MAJOR GUIDANCE TIMING DISAGREEMENTS BEGINNING CHRISTMAS EVE
AND LASTING THROUGH TUES. CONSENSUS IS TO STAY WITH THE LESS
PROGRESSIVE AND SOMEWHAT DRIER ECMWF, WHICH DELAYS THE COLD FRONT
PASSAGE THE GFS HAS FOR CHRISTMAS DAY UNTIL CHRISTMAS NIGHT. EVEN
SO, THE ECMWF STILL BEGINS TO PRODUCE LIGHT STRATIFORM SNOWS ALONG
A DEVELOPING...OR IN-SITU...WARM FRONTAL BOUNDARY BISECTING ERN WA
AND N ID MORE OR LESS WEST TO EAST WELL IN ADVANCE OF ITS OFFSHORE
COLD FRONT THAT THE GFS ALREADY HAS PAST SPOKANE BY MIDDAY
CHRISTMAS. WITH CHRISTMAS FIVE DAYS OUT, IT`S ESSENTIAL THAT WE
TREND IN THE DIRECTION OF THE MOST CONSISTANT GUIDANCE AND TRY TO
GIVE THE MAJOR POPULATION CENTERS MORE ATTENTION. THAT SAID, AND
BASED ON THE ABOVE MENTIONED GUIDANCE TRENDS, IT STILL LOOKS LIKE
SPOKANE WILL SEE SOME SNOW ON CHRISTMAS. THIS WILL BE ESPECIALLY
TRUE IF THE AFOREMENTIONED STATIONARY EAST-WEST FRONTAL BOUNDARY
SETS UP FARTHER SOUTH THAN EXPECTED. IT IS THIS BOUNDARY THAT WILL
BE THE PRIMARY SOURCE OF ISENTROPIC LIFT THAT WILL PRODUCE THE
INITIAL SNOW ON CHRISTMAS. DUE TO THE QUICK APPROACH OF THE UPPER
LOW, SNOW AMNTS SHOULDER NOT BE HEAVY. HOWEVER, THE HIGHEST AMNTS
WILL FALL ACROSS NRN WA AND N ID CHRISTMAS. A NOTE OF SIGNIFICANCE:
ONCE THE UPPER LOW CROSSES THE CASCADES CHRISTMAS NIGHT AND
CROSSES N ID MON (ASSUMING THIS TIMING IS CORRECT), N ID (AND
ESPECIALLY THE MTNS) WILL ENTER A VERY FAVORABLE PATTERN FOR
CONVECTIVE SNOWS AS THE POST FRONTAL LAPSE RATES STEEPEN AND THE
FLOW VEERS TO WESTERLY AND TAKES ON A MUCH MORE FAVORABLE UPSLOPE
COMPONENT. GUSTY WINDS STILL LOOK POSSIBLE INTO MONDAY.BZ
&&
.AVIATION...
18Z TAFs: Low stratus will continue to impact the majority of the
TAF sites this afternoon. The exception will be KPUW and KLWS where
a drier boundary layer from south-southeast winds should result in
VFR conditions persisting. A tough forecast in general for the
KGEG-KSFF-KCOE corridor as models indicate stratus hanging up in
this area with clearing to the south and stratus remaining locked in
to the north. Will rely on current trends and HRRR guidance for
this area. As winds switch to the southwest ahead of a cold front
late this afternoon and evening this will favor stratus advecting east
from the basin into the KGEG-KSFF-KCOE corridor as well as KPUW and
eventually KLWS. But then as drier advection moves in after 06z
behind the cold front should see some erosion of the stratus
especially KMWH/KEAT and probably KGEG and KSFF based on drying in
the boundary layer indicated by the NAM. Stratus will probably hang
in longer at KCOE/KPUW/KLWS with west-northwest winds favoring
stratus hanging up in these areas. A brief period of -SN may also
occur in these areas with the cold front especially KPUW.
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 22 28 16 26 19 30 / 20 0 0 0 0 20
Coeur d`Alene 21 29 15 29 15 33 / 20 0 0 0 0 30
Pullman 25 30 15 30 21 34 / 40 10 0 0 0 10
Lewiston 30 33 20 35 22 37 / 50 10 0 0 0 10
Colville 21 29 10 30 18 32 / 20 0 0 0 0 10
Sandpoint 22 29 11 29 16 31 / 30 10 0 0 0 30
Kellogg 24 29 18 30 21 32 / 70 10 10 0 0 30
Moses Lake 22 33 14 31 18 32 / 0 0 0 0 0 10
Wenatchee 24 33 17 33 24 33 / 0 0 0 0 0 10
Omak 19 29 9 29 18 31 / 10 0 0 0 0 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$
AREA FORECAST DISCUSSION
NWS SPOKANE WA
238 PM PST Tue Dec 20 2011
.SYNOPSIS...A cold front will sweep through the Inland Northwest from
the north late this afternoon and this evening. This system is not
expected to carry much snow, but it will bring decidedly cooler
temperatures to the region as well as improving ventilation
conditions. An active winter weather pattern is expected to
continue through the holiday weekend and into the first part of
next week.
&&
.DISCUSSION...
Tonight...Satellite imagery indicates an upper level trough over
British Columbia dropping southeast towards Eastern Washington and
North Idaho. Instability in the mid levels of the atmosphere will
increase significantly this evening as 500mb temps fall to near
-36C and 850-500mb lapse rates increase to 7-8 C/KM. However
moisture is limited with this trough, and with 850mb winds of
15-25 knots out of the west to northwest significant down slope
flow off the higher terrain of Northern Washington and British
Columbia is likely. This should keep the best chances for snow
showers over the Cascades, Central Panhandle Mountains, Blue
Mountains, and Camas Prairie. Low level up slope flow into the
Palouse may also result in a brief light accumulation. An area of
lift from a passing vort max will also increase chances for snow
showers in these areas. The Camas Prairie looks to be the most
favored in this flow pattern but even here models only generate
one to two tenths of liquid precipitation so snow accumulations
were kept near 2 inches with no highlights needed at this time.
The cool and dry advection tonight with this trough will weaken
the inversion and will bring erosion of the stratus layer
especially over the northern valleys...and down the Okanogan
Valley into the western Columbia Basin. Patchy fog may form once
stratus clears but with the boundary layer drying out confidence
is not high so for now left mention of the forecast. JW
Wednesday through Friday...Through this portion of the forecast an
upper level low will pass out of the forecast area Wednesday morning,
then the weather will be dominated by a flat ridge of high
pressure through Thursday after. This will be followed by a
weakening/splitting weather disturbance Thursday night and Friday.
Challenges through this portion of the forecast will be the
probably of fog/stratus development with high pressure over the
region. Also, while model guidance all show a weakening frontal
system Thursday night the GFS/SREF show some weakening and a
slower solution than the NAM/EC/GEM. So far this season slower and
splitting weather systems have been the way and will lean in that
direction, what ever solution verifies confidence is not high
that there will be much snow.
Wednesday through Thursday northwest-north flow will keep some
snow showers over the southeast zones through about mid day
Wednesday, otherwise a dry and cool flow will result in a dry
forecast. The northerly flow and resultant cold air advection
should me enough to mix out the surface inversion and the
fog/stratus that has been going with it. There will most likely be
some regeneration of the fog along warmer water sources Thursday
morning, but expect this to be shallow and patchy. Temperatures
will cool by several degrees and be just on the cool side of normal.
Thursday night and Friday upper level moisture ahead of the
upstream weather system will move over the ridge. This should help
inhibit radiational cooling and keep the inversion from
strengthening any further. Model guidance is showing differing
solutions, but this trough passage is far from impressive. Some
isentropic ascent and upper level moisture is expected to track
through southern BC and will bring some light snow to the Cascade
crest and the northern mountains. Up-sloping will increase the
lift over the panhandle mountains, but with little moisture to
work with any snow accumulations will be very light. The following
cold front is almost non-existent at the surface but may be marginally
successful in keeping the boundary layer mixed. /Tobin
FRI NT THROUGH TUES: SIGNIFICANT CHALLENGES STILL EXIST AS A RESULT
OF MAJOR GUIDANCE TIMING DISAGREEMENTS BEGINNING CHRISTMAS EVE
AND LASTING THROUGH TUES. CONSENSUS IS TO STAY WITH THE LESS
PROGRESSIVE AND SOMEWHAT DRIER ECMWF, WHICH DELAYS THE COLD FRONT
PASSAGE THE GFS HAS FOR CHRISTMAS DAY UNTIL CHRISTMAS NIGHT. EVEN
SO, THE ECMWF STILL BEGINS TO PRODUCE LIGHT STRATIFORM SNOWS ALONG
A DEVELOPING...OR IN-SITU...WARM FRONTAL BOUNDARY BISECTING ERN WA
AND N ID MORE OR LESS WEST TO EAST WELL IN ADVANCE OF ITS OFFSHORE
COLD FRONT THAT THE GFS ALREADY HAS PAST SPOKANE BY MIDDAY
CHRISTMAS. WITH CHRISTMAS FIVE DAYS OUT, IT`S ESSENTIAL THAT WE
TREND IN THE DIRECTION OF THE MOST CONSISTANT GUIDANCE AND TRY TO
GIVE THE MAJOR POPULATION CENTERS MORE ATTENTION. THAT SAID, AND
BASED ON THE ABOVE MENTIONED GUIDANCE TRENDS, IT STILL LOOKS LIKE
SPOKANE WILL SEE SOME SNOW ON CHRISTMAS. THIS WILL BE ESPECIALLY
TRUE IF THE AFOREMENTIONED STATIONARY EAST-WEST FRONTAL BOUNDARY
SETS UP FARTHER SOUTH THAN EXPECTED. IT IS THIS BOUNDARY THAT WILL
BE THE PRIMARY SOURCE OF ISENTROPIC LIFT THAT WILL PRODUCE THE
INITIAL SNOW ON CHRISTMAS. DUE TO THE QUICK APPROACH OF THE UPPER
LOW, SNOW AMNTS SHOULDER NOT BE HEAVY. HOWEVER, THE HIGHEST AMNTS
WILL FALL ACROSS NRN WA AND N ID CHRISTMAS. A NOTE OF SIGNIFICANCE:
ONCE THE UPPER LOW CROSSES THE CASCADES CHRISTMAS NIGHT AND
CROSSES N ID MON (ASSUMING THIS TIMING IS CORRECT), N ID (AND
ESPECIALLY THE MTNS) WILL ENTER A VERY FAVORABLE PATTERN FOR
CONVECTIVE SNOWS AS THE POST FRONTAL LAPSE RATES STEEPEN AND THE
FLOW VEERS TO WESTERLY AND TAKES ON A MUCH MORE FAVORABLE UPSLOPE
COMPONENT. GUSTY WINDS STILL LOOK POSSIBLE INTO MONDAY.BZ
&&
.AVIATION...
18Z TAFs: Low stratus will continue to impact the majority of the
TAF sites this afternoon. The exception will be KPUW and KLWS where
a drier boundary layer from south-southeast winds should result in
VFR conditions persisting. A tough forecast in general for the
KGEG-KSFF-KCOE corridor as models indicate stratus hanging up in
this area with clearing to the south and stratus remaining locked in
to the north. Will rely on current trends and HRRR guidance for
this area. As winds switch to the southwest ahead of a cold front
late this afternoon and evening this will favor stratus advecting east
from the basin into the KGEG-KSFF-KCOE corridor as well as KPUW and
eventually KLWS. But then as drier advection moves in after 06z
behind the cold front should see some erosion of the stratus
especially KMWH/KEAT and probably KGEG and KSFF based on drying in
the boundary layer indicated by the NAM. Stratus will probably hang
in longer at KCOE/KPUW/KLWS with west-northwest winds favoring
stratus hanging up in these areas. A brief period of -SN may also
occur in these areas with the cold front especially KPUW.
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 22 28 16 26 19 30 / 20 0 0 0 0 20
Coeur d`Alene 21 29 15 29 15 33 / 20 0 0 0 0 30
Pullman 25 30 15 30 21 34 / 40 10 0 0 0 10
Lewiston 30 33 20 35 22 37 / 50 10 0 0 0 10
Colville 21 29 10 30 18 32 / 20 0 0 0 0 10
Sandpoint 22 29 11 29 16 31 / 30 10 0 0 0 30
Kellogg 24 29 18 30 21 32 / 70 10 10 0 0 30
Moses Lake 22 33 14 31 18 32 / 0 0 0 0 0 10
Wenatchee 24 33 17 33 24 33 / 0 0 0 0 0 10
Omak 19 29 9 29 18 31 / 10 0 0 0 0 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$
AREA FORECAST DISCUSSION
NWS SPOKANE WA
1226 PM PST Tue Dec 20 2011
.SYNOPSIS...The ridge of the past couple weeks will break down today
and tonight as a robust cold front sweeps in from the north.
Although this system won`t contain much snow, it will bring decidedly
cooler temperatures to the region as well as improving ventilation
conditions. A slightly more active winter weather pattern is
expected to continue through the end of the week and into the
holiday weekend.
&&
.DISCUSSION...
The forecast has been updated to end the air stagnation advisory.
Mixing potential will increase over the next 24 hours at cold
advection increases behind a cold front passage tonight.
For the rest of today minor adjustments have been made to lower
precipitation chances in some areas. Thus far precipitation has
been confined to the North Idaho Panhandle and Cascade crest area.
With westerly flow increasing this afternoon off the Cascades,
went with the NAM idea of areas in the lee of the Cascades such as
Leavenworth and Winthrop remaining in a snow shadow.
Meanwhile, precipitation chances will remain low today over the
Camas Prairie until the cold front passes through tonight. Thus
pops were lowered in this area for the afternoon hours. Pops were
also lowered this afternoon for Spokane with radar showing very
little in the way of precipitation in the area. Satellite indicated
a band of mid and high clouds moving over the stratus layer and
with the warm front already out of the area the westerly flow
should keep light snow activity this afternoon over the mountains
north and east of Spokane. JW
&&
.AVIATION...
18Z TAFs: Low stratus will continue to impact the majority of the
TAF sites this afternoon. The exception will be KPUW and KLWS where
a drier boundary layer from south-southeast winds should result in
VFR conditions persisting. A tough forecast in general for the
KGEG-KSFF-KCOE corridor as models indicate stratus hanging up in
this area with clearing to the south and stratus remaining locked in
to the north. Will rely on current trends and HRRR guidance for
this area. As winds switch to the southwest ahead of a cold front
late this afternoon and evening this will favor stratus advecting east
from the basin into the KGEG-KSFF-KCOE corridor as well as KPUW and
eventually KLWS. But then as drier advection moves in after 06z
behind the cold front should see some erosion of the stratus
especially KMWH/KEAT and probably KGEG and KSFF based on drying in
the boundary layer indicated by the NAM. Stratus will probably hang
in longer at KCOE/KPUW/KLWS with west-northwest winds favoring
stratus hanging up in these areas. A brief period of -SN may also
occur in these areas with the cold front especially KPUW.
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 30 22 28 16 26 19 / 10 20 0 0 0 0
Coeur d`Alene 32 21 29 15 29 15 / 20 20 0 0 0 0
Pullman 37 25 30 15 30 21 / 20 40 10 0 0 0
Lewiston 38 30 33 20 35 22 / 10 50 10 0 0 0
Colville 32 21 29 10 30 18 / 20 20 0 0 0 0
Sandpoint 32 22 29 11 29 16 / 30 30 10 0 0 0
Kellogg 34 24 29 18 30 21 / 50 70 10 10 0 0
Moses Lake 32 22 33 14 31 18 / 0 0 0 0 0 0
Wenatchee 32 24 33 17 33 24 / 0 0 0 0 0 0
Omak 31 19 29 9 29 18 / 0 0 0 0 0 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$
AREA FORECAST DISCUSSION
NWS SPOKANE WA
951 AM PST Tue Dec 20 2011
.SYNOPSIS...The ridge of the past couple weeks will break down today
and tonight as a robust cold front sweeps in from the north.
Although this system won`t contain much snow, it will bring decidedly
cooler temperatures to the region as well as improving ventilation
conditions. A slightly more active winter weather pattern is
expected to continue through the end of the week and into the
holiday weekend.
&&
.DISCUSSION...
Today through Wednesday morning...After a two week stay or so...the
persistent upper level ridge will be broken down by a well-
defined upper level trough currently moving toward the central BC
coast. The short-range models are in good agreement that a broad
swath of moisture ahead of this trough will dip south through the
forecast area during the day...hitting locations near the Canadian
border this morning and moving into the central portion of the
forecast area by afternoon. Precipitable water values within this
plume were around a half inch east of the Cascades which is around
150% of the seasonal normals and is surprisingly high considering
the cool in situ near ground temperatures and the track of the
system from the northwest. Nonetheless precipitation chances will
not be great as there is very little sign of an associated
surface-850 mb low and little variance from the west-northwest
flow at 850 mbs. Thus rain shadowing will be a big factor in
determining where precipitation falls. Given the flow pattern the
best chances for measurable precipitation today will occur near
the Cascades and over the Idaho Panhandle. As is typically the
case with systems diving down from the northwest...QPF amounts are
generally very light and this will likely prove no exception. We
have penciled in amounts of an inch or less for locations near the
Cascade crest...including the upper Methow Valley...and less than
half an inch for locations over the north Idaho Panhandle. By
evening the upper level trough tracks across the International
Border bringing a cold front with it. 500 mb temperatures plummet
to -36c or cooler resulting in a rapid destabilization. This will
likely manifest itself as a few snow showers...but they won`t be
widespread as the dendritic layer becomes sapped of appreciable
moisture...at least across the northern portions of the forecast
area. The southeast half of the forecast area...Palouse...Lewiston
area...Blue Mountains and Camas Prairie stand to see the most
appreciable weather from the approaching trough. The flow behind
the cold front will turn to more of a north-northwest orientation
which will combine with the destabilization during the overnight
portions of the forecast. The combination of upper level ascent
associated with the shortwave trough and the orographic ascent
through an unstable layer will result in widespread shower
activity...but even so QPF and snow amounts will be somewhat
underwhelming as the system moves through very quick. The models
continue to trend QPF amounts downward with most of the activity
ending by Wednesday morning. At this point we have placed around
1-2 inches of snow with local 3 inch amounts over the central
Panhandle, Blue Mountains, and Camas Prairie. Although this is
significant compared to what has occurred lately, it is well below
winter headline criteria. For the Lewiston and Pullman areas less
than an inch will accumulate overnight.
While this storm will likely underwhelm from a snow perspective it
will finally rid us of the persistent inversions which have
plagued much of the Columbia Basin for the past couple weeks. The
air stagnation advisory will finally be allowed to end with the
arrival of the cooler and drier air from the north. fx
Wednesday afternoon through Friday: By Wednesday afternoon, a mid-
level system will have pushed southeast of the area. Model
agreement on a faster solution seems to be fairly strong at this
time, with the GFS the slowest guidance by 18z Wednesday. Even as
the slowest guidance, the GFS still have the mid-level wave axis
extending from roughly Boise to Billings, which places it far to
the southeast of our forecast area. With the faster speed,
subsequent drying and cold air advection behind it will already be
into high gear. Strong model consensus on drying the entire CWA
from 700 mb upward exists by 18z Wednesday, with only weak
moisture from the surface to 700 mb remaining over the central
Idaho Panhandle. Because of this, PoPs were slashed everywhere,
and the only remnant of a chance of snow showers will be the
highest terrain of Shoshone County while exceedingly weak upslope
850 mb flow turns basically calm by the end of the afternoon.
As Tuesday night/early Wednesday`s system continues to depart to
the southeast, short wave ridging and surface high pres sue builds
into the area. With a complete boundary layer air mass changeover
likely, it seems probable that even with subsidence incoming, fog
may be tough to form given the dry Canadian origins of the
environment by that juncture. Fog has been excluded from the
forecast as a result, however it may still be possible along local
rivers and lakes that will act as a surface layer moisture source.
Additionally, meager layer moisture above the boundary layer means
a very clear night by be in store. With surface high pressure
overhead, a dry air mass, and clear skies, temperatures are likely
to fall to their lowest levels of the season in many spots. The
forecast remains largely below guidance, however the new GFS grids
suggest that many of the northern valleys will fall below 0F.
While it seems likely some locations will do this, the lack of
widespread snow cover in the valleys will make this an isolated
rather than widespread scenario.
The 00z guidance tonight has also come into a stronger cluster
with the arrival of the next system to affect the area. All signs
from the NAM/GEM/GFS/ECMWF point to isentropic and slop over
precipitation reaching the crest and near crest of the Cascades
overnight Thursday night. Given the cold air in place, all
precipitation is likely to be snow, however, the mid-level system
never closes off and moisture again looks limited. As a result,
low level westerlies will likely create an expansive precipitation
shadow east of the Cascades that may well extend all the way to
the Idaho Panhandle mountains. PoPs east of the Cascades and
throughout most of eastern Washington are very limited as a
result.
Beyond Friday: Model and ensemble guidance continues to point at a
transient ridge shifting through the area next weekend with its
departure targeted for Sunday night. After that time, early
indications are that a wetter on shore flow pattern may result,
however model solutions become much more scatter shot with any
system location let alone show any agreement over the direction of
the flow over the area. As a result, after a mostly dry weekend,
PoPs trend quickly toward climatology into next week. /Fries
&&
.AVIATION...
18Z TAFs: Low stratus will continue to impact the majority of the
TAF sites this afternoon. The exception will be KPUW and KLWS where
a drier boundary layer from south-southeast winds should result in
VFR conditions persisting. A tough forecast in general for the
KGEG-KSFF-KCOE corridor as models indicate stratus hanging up in
this area with clearing to the south and stratus remaining locked in
to the north. Will rely on current trends and HRRR guidance for
this area. As winds switch to the southwest ahead of a cold front
late this afternoon and evening this will favor stratus advecting east
from the basin into the KGEG-KSFF-KCOE corridor as well as KPUW and
eventually KLWS. But then as drier advection moves in after 06z
behind the cold front should see some erosion of the stratus
especially KMWH/KEAT and probably KGEG and KSFF based on drying in
the boundary layer indicated by the NAM. Stratus will probably hang
in longer at KCOE/KPUW/KLWS with west-northwest winds favoring
stratus hanging up in these areas. A brief period of -SN may also
occur in these areas with the cold front especially KPUW.
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 30 22 28 14 26 20 / 20 20 0 0 0 0
Coeur d`Alene 30 21 29 15 29 15 / 20 20 0 0 0 0
Pullman 37 25 30 15 30 22 / 30 40 10 0 0 0
Lewiston 38 30 33 20 35 22 / 10 50 10 0 0 0
Colville 32 23 29 10 30 19 / 20 20 0 0 0 0
Sandpoint 32 22 29 11 29 16 / 30 30 10 0 0 0
Kellogg 33 24 29 18 30 22 / 50 70 10 10 0 0
Moses Lake 32 22 33 14 31 18 / 0 0 0 0 0 0
Wenatchee 32 24 34 17 33 24 / 0 0 0 0 0 0
Omak 31 19 29 9 29 19 / 10 0 0 0 0 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Air Stagnation Advisory until Noon PST today for Central
Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse-
Lewiston Area-Northern Panhandle.
WA...Air Stagnation Advisory until Noon PST today for East Slopes
Northern Cascades-Lower Garfield and Asotin Counties-Moses
Lake Area-Northeast Mountains-Okanogan Highlands-Okanogan
Valley-Spokane Area-Upper Columbia Basin-Washington Palouse-
Waterville Plateau-Wenatchee Area.
&&
$$
AREA FORECAST DISCUSSION
NWS MILWAUKEE/SULLIVAN WI
325 PM CST TUE DEC 20 2011
.VERY SHORT TERM...TONIGHT AND WEDNESDAY.
BAND OF LIGHT RAIN/LIGHT SNOW SHOWERS CURRENTLY IN FAR NORTHERN
ILLINOIS SHOULD PUSH INTO THE FAR SOUTHERN COUNTIES THROUGH THE REST
OF THE AFTERNOON. ROCKFORD ASOS REPORTED A PERIOD OF RAIN AND SNOW
WITH THIS BAND...WITH RUC FORECAST SOUNDINGS IN THE AREA SHOWING WEB
BULB NEAR FREEZING. THIS AREA BEING DRIVEN BY LOW LEVEL WARM AIR
ADVECTION AND MID LEVEL FRONTOGENESIS RESPONSE. THIS AREA OF
PRECIPITATION BEING SLOWED IN ITS ADVANCE BY DRIER AIR PUSHING
SOUTHEAST INTO THE AREA.
LOCAL HIGH RESOLUTION MODELS NOT DOING A GOOD JOB WITH CAPTURING
THIS BAND. THINKING FOR THE REST OF THE AFTERNOON WOULD BE TO
MENTION LIGHT RAIN SHOWERS/SNOW SHOWERS IN THE FAR SOUTHERN
COUNTIES. WARM AIR ADVECTION SHIFTS EAST BY 00Z WEDNESDAY...SO THINK
THIS BAND WILL WEAKEN AND DISSIPATE BY THEN. WILL HAVE TO KEEP AN
EYE ON IT INTO THE EARLY EVENING...AS IT MAY AFFECT ROADS WITH A
DUSTING OF SNOW INTO THE EARLY EVENING IN THIS AREA.
ONCE THIS DISSIPATES BY EARLY EVENING...NEXT ISSUE WILL BE DRIZZLE
AND VERY LIGHT RAIN WITH PASSING UPPER LEVEL LOW TONIGHT AND EARLY
WEDNESDAY. WEAK LOW LEVEL FRONTOGENESIS RESPONSE CLIPS THE FAR
SOUTHERN AND SOUTHEASTERN COUNTIES THIS EVENING...EXITING THE
SOUTHEAST BY EARLY WEDNESDAY MORNING. UPPER LOW TRACKS NORTHEAST TO
FAR EASTERN IOWA BY 12Z WEDNESDAY...WITH DIFFERENTIAL CYCLONIC
VORTICITY ADVECTION INTO THE FORECAST AREA AHEAD OF IT.
AREA FORECAST SOUNDINGS SATURATE IN THE LOW LEVELS FROM SOUTHEAST TO
NORTHEAST ACROSS THE SOUTHERN PORTIONS OF THE FORECAST AREA THIS
EVENING...REMAINING SO INTO WEDNESDAY MORNING. SOUNDINGS SUPPORT
VERY LIGHT RAIN/DRIZZLE ACROSS THE SOUTHEAST AND FAR SOUTHERN
COUNTIES TONIGHT. POTENTIAL FOR LIGHT FREEZING DRIZZLE REMAINS IN
AREAS MAINLY SOUTH AND SOUTHWEST OF MADISON...WHERE TEMPERATURES ARE
EXPECTED TO DIP BELOW FREEZING.
PRECIPITATION SHOULD CLEAR THE FAR SOUTHEAST BY LATE WEDNESDAY
MORNING. DRIER AIR WORKING INTO THE LOW LEVELS SHOULD THEN BRING
QUIET WEATHER THROUGH THE AFTERNOON...WITH CLOUDS GRADUALLY MIXING
OUT FROM WEST TO EAST.
.SHORT TERM...WEDNESDAY NIGHT THROUGH FRIDAY.
FOCUS OF THIS PERIOD ON INCREASING THREAT FOR LIGHT PRECIPITATION
WEDNESDAY NIGHT INTO THURSDAY. SHORT TERM GUIDANCE IN REASONABLE
AGREEMENT ON WEAK ISENTROPIC FORCING SPREADING ACROSS PORTIONS OF
SOUTH CENTRAL WI LATER WED NIGHT INTO THU. WEAK ISENTROPIC FORCING
ON 295 THETA SFC ENHANCED BY RIGHT ENTRANCE REGION OF 300H JET
MOVING TO THE EAST ACROSS THE NORTHERN GTLAKES. HENCE WL ADD LOW
CHANCE POPS ACROSS NRN CWA. BEST FORCING SLIDES TO THE EAST THU
MRNG. WL CONT SCHC WORDING AS WEAK ISENTROPIC OMEGA AND WEAK 700H
WAVE SLIDES ACROSS SRN WI.
LOW LEVEL FLOW TURNS TO THE NORTH THU NIGHT. LOW LEVEL WINDS REMAIN
MORE NORTHERLY ON NAM WHILE GFS MORE NORTHEAST. WITH DELTA-T AROUND
15C...GFS WOULD HINT AT POSSIBLY PERIOD OF -SHSN OVER LAKESHORE
COUNTIES THU EVE. INITIAL MOISTURE QUESTIONABLE...AND LOW LEVELS
GRADUALLY DRY OUT THU NIGHT...SO WEAK LAKE EFFECT THREAT DIMINISHES
AFT MIDNIGHT. FOR NOW...DUE TO UNCERTAINTY IN LOW LEVEL WINDS...WL
HAVE SCHC WORDING DURING THE EVE. COLDER AIR IN PLACE ON FRIDAY AS
HIGH PRESSURE RIDGING PASSES THROUGH SRN WI.
.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY.
UNCERTAINTIES APPEAR RIGHT AWAY IN THE EXTENDED PERIOD AS BOTH ECMWF
AND GFS HAVING DIFFICULTIES DETERMINING STRENGTH OF SPLIT FLOW
ACROSS CONUS AND WESTERLIES ACROSS UPPER MIDWEST. EXTENDED GUIDANCE
NOW TRENDING TOWARD STRONGER WEST TO NORTHWEST FLOW ACROSS NORTHERN
CONUS INCLUDING WRN GTLAKES FOR DURATION OF PERIOD...HENCE
INCREASING CONFIDENCE. GFS ENSEMBLE MEMBERS ALSO SHOWING BETTER
AGREEMENT FOR THIS PATTERN AS WELL. THIS SCENARIO RESULTS IN DEEP
MOISTURE REMAINING WELL SOUTH OF AREA...AVAILABLE TO TAP INTO FOR
MORE UNSETTLED FLOW ACROSS SRN CONUS.
WITH MOSTLY ZONAL TO WNW FLOW AND DEEP MOISTURE TO THE
SOUTH...EXTENDED PERIOD FOR SRN WI LOOKING FAIRLY QUIET WITH
TEMPERATURES AVERAGING OUT NEAR OR SLIGHTLY ABOVE NORMAL DUE TO LACK
OF SNOW COVER. BOTH ECMWF AND GFS INDICATE LONG WAVE TROUGH MOVING
THRU WRN GTLAKES LATE IN THE HOLIDAY WEEKEND. ECMWF INCLUDES A
STRONGER SHORT WAVE SLIDING SOUTHWARD AND DEEPENING IN LONG WAVE
TROUGH. MOISTURE WILL BE MINIMAL AND NEITHER GEM OR GFS SHOWING
THIS STRONGER FEATURE. MEDIUM RANGE ENSEMBLE POPS ALSO REMAIN LESS
THAN 10 PERCENT. HENCE WL CONTINUE DRY FORECAST FOR NOW THROUGH THE
HOLIDAY WEEKEND.
WL NEED TO KEEP ONE EYE ON DEVELOPING LOW PRESSURE OVER SOUTHEAST
CONUS XMAS EVE AS IT TRACKS NORTHEAST ON XMAS DAY...HOWEVER
PREDOMINANT WEST TO NORTHWEST FLOW OVER NORTHERN CONUS SHOULD KEEP
THIS SYSTEM WELL TO THE SOUTHEAST.
LONG WAVE TROUGH CONTINUES ITS TREK EWD LATE IN THE WEEKEND AND
EARLY MONDAY...WITH ZONAL FLOW RETURNING FOR THE FIRST PART OF THE
WEEK. GFS 5DAY 500H MEANS INDICATES THIS FLOW WL CONTINUE THROUGH
THE LAST DAYS OF THE YEAR WITH GRADUALLY LOWERING HEIGHTS. EXPECT
WEAK SHORT WAVES TRAVERSING WESTERLIES TO OCCASIONALLY THREATEN SRN
WI WITH LIGHT PRECIP DURING THIS PD.
&&
.AVIATION /00Z TAFS/...BAND OF LIGHT RAIN AND LIGHT SNOW SHOWERS
WILL AFFECT KENOSHA UNTIL AROUND 00Z WEDNESDAY. QUESTIONABLE IF IT
WILL MAKE IT TO MILWAUKEE...WAUKESHA AND MADISON WITH DRIER AIR TO
THE NORTH SLOWING ITS ADVANCE. FOR NOW...WILL MENTION VICINITY IN
TAFS BUT NOT PREVAILING. SOME MVFR CEILINGS AND VISIBILITIES
POSSIBLE IN THIS BAND...ALONG WITH A DUSTING OF SNOW ON RUNWAYS.
MVFR CEILINGS AND VISIBILITIES ARE EXPECTED TO SHIFT NORTHWARD TO
TAF SITES DURING THE EVENING. LIGHT DRIZZLE IS EXPECTED AT THE
EASTERN SITES BETWEEN 03Z TO 15Z WEDNESDAY...WITH LIGHT RAIN
POSSIBLE AT KENOSHA. PATCHY LIGHT FREEZING DRIZZLE IS POSSIBLE AT
MADISON BETWEEN 09Z AND 13Z WEDNESDAY...BUT WILL LEAVE OUT OF TAFS
FOR NOW DUE TO SOME UNCERTAINTY WITH HOW FAR NORTHWEST THE DRIZZLE
WILL REACH.
VFR CONDITIONS SHOULD RETURN BY 15Z TO 16Z WEDNESDAY ACROSS TAF
SITES...AND REMAIN THROUGH THE REST OF THE DAY. LIGHT SOUTH WINDS
TODAY WILL BECOME VARIABLE TONIGHT...THEN SOUTHWEST TO WEST BY
MIDDAY WEDNESDAY.
&&
.CONFIDENCE...
TONIGHT AND WEDNESDAY...MEDIUM.
WEDNESDAY NIGHT AND THURSDAY...LOW TO MEDIUM.
THURSDAY NIGHT AND FRIDAY...MEDIUM TO HIGH.
FRIDAY NIGHT THROUGH TUESDAY...MEDIUM.
&&
.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&
$$
SHORT TERM/LONG TERM...MBK
VERY SHORT TERM/AVIATION/MARINE...WOOD