FXUS63 KGRB 080410 AAA
AFDGRB

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GREEN BAY WI
1010 PM CST MON DEC 7 2009

.UPDATE...MADE SOME ADJUSTMENTS TO MIN TEMPS...ESPECIALLY OVER OUR
SOUTHERN COUNTIES...WHERE PARTLY CLOUDY SKIES AND A FRESH SNOW
COVER HAD ALLOWED TEMPS TO DROP INTO THE UPPER SINGLE DIGITS AND
TEENS. MAY NEED TO MAKE ADDITIONAL ADJUSTMENTS LATE THIS EVG.

DID NOT MAKE ANY CHANGES TO THE WINTER WX HEADLINES. THE 21Z SREF
AND 00Z NAM CONTINUE TO SHOW A FARTHER WEST TRACK WITH THE SFC
LOW...TAKING IT THROUGH FAR SE WI BY 12Z/WEDS...COMPARED TO THE
00Z GFS FCST...WHICH HAS THE LOW JUST SE OF MUSKEGON MI. THIS HAS
IMPLICATIONS WITH THE QPF/SNOWFALL FCST...WITH THE NAM SUGGESTING
HIGHER AMOUNTS...ESP IN EC WI. FOR WHAT IT'S WORTH...THE GFS HAS
BEEN VERY CONSISTENT THE PAST COUPLE DAYS. HEAVIEST SNOW IS
EXPECTED LATER TUESDAY NGT INTO EARLY WEDS...AS THE DEFORMATION
ZONE WITH A DEEPENING UPPER LOW LIFTS NNE THROUGH EASTERN WI.

KIECKBUSCH
&&

.PREV DISCUSSION...ISSUED AT 351 PM CST MON DEC 7 2009...

SHORT TERM...TONIGHT AND TUESDAY.

THE MAIN FORECAST CONCERN IS SNOW WITH THE STORM SYSTEM THAT WAS
DEVELOPING OVER THE SOUTHWEST CONUS THIS AFTERNOON. 12Z MODELS
WERE IN GOOD AGREEMENT...SHOWING QPF SPREADING ACROSS THE SOUTHERN
PART OF THE FORECAST BETWEEN 12Z AND 18Z TUESDAY...THEN ACROSS THE
REST OF THE CWA BY 00Z WEDNESDAY. HPC GUIDANCE INDICATED ONE TO
TWO INCHES GENERALLY SOUTHWEST OF A MERRILL TO GREEN BAY TO
MANITOWOC LINE BETWEEN 00Z TUESDAY THROUGH 00Z WEDNESDAY.

THE 2 INCH CONTOUR FROM HPC WAS NOT FAR SOUTHWEST OF THE FORECAST
AREA AND MODELS BROUGHT QPF TO THE AREA RATHER RAPIDLY. AS A
RESULT...HAVE GONE WITH A FEW TENTHS OF AN INCH OF SNOW FOR THE
SOUTHWEST CWA DURING THE MORNING...THEN 1.0 TO 1.5 INCH FOR MOST
LOCATIONS DURING THE AFTERNOON.

TEMPERATURES ARE COLD ENOUGH BUT WINDS TONIGHT DID NOT APPEAR
FAVORABLE FOR LAKE EFFECT IN NORTH-CENTRAL WISCONSIN. THOUGHT
ABOUT LEAVING OUT ANY MENTION OF LAKE EFFECT IN THE NORTH
TONIGHT...BUT POPS WERE IN THE CHANCE CATEGORY TO THE NORTH AND
WEST...SO HAVE MENTIONED ISOLATED SNOW SHOWERS FOR VILAS THIS
EVENING...BUT NOTHING AFTER 06Z.

LONG TERM...TUESDAY NIGHT THRU NEXT MONDAY. 

AN EXTENDED PERIOD OF BELOW AVERAGE TEMPERATURES REMAINS IN STORE 
FOR THE WESTERN GREAT LAKES REGION THROUGH END OF THE WEEKEND.  
ROBUST OMEGA BLOCK OVER ALASKA WILL GRADUALLY WEAKEN BY THE END OF 
THE WEEK...AS RIDGING OVER THE ARCTIC REASSERTS ITSELF AND DISLODGES 
THE POLAR VORTEX SOUTHWARD FOR THIS WEEKEND.  HOWEVER...WITH THE 
ARRIVAL OF THE ARCTIC AIRMASS...QUIET CONDITIONS WILL RETURN AFTER 
THE POTENT LOW PRESSURE SYSTEM DEPARTS LATE WEDNESDAY.  LATEST MODEL 
RUNS LOOK TO BE IN BETTER THAN AVERAGE AGREEMENT THROUGH THIS 
EXTENDED FORECAST.  WILL THEREFORE TAKE A BLEND OF THE 00Z ECMWF AND 
06Z GFS THROUGH FRIDAY AT 12Z BEFORE TRENDING TOWARDS THE 00Z GFS 
ENSEMBLE THEREAFTER.

TUESDAY NIGHT AND WEDNESDAY...12Z GFS AND ECMWF ARE IN GOOD 
AGREEMENT WITH THE TRACK AND TIMING OF THE FIRST WINTER STORM OF THE 
YEAR.  STRONG SHORTWAVE CURRENTLY DIGGING SOUTHWARD ACROSS 
CALIFORNIA WILL MOVE FROM THE SOUTH-CENTRAL PLAINS TO THE 
MID-MISSISSIPPI VALLEY TUESDAY NIGHT BEFORE REACHING THE EASTERN 
GREAT LAKES ON WEDNESDAY.  AHEAD OF THE SHORTWAVE...A DYNAMIC 
SURFACE LOW WILL GAIN STRENGTH AS IT REACHES SOUTHERN LAKE MICHIGAN 
BY WED 12Z AND CENTRAL LAKE HURON BY 00Z THU.  SOUTHERLY TO 
SOUTHEASTERLY WINDS ALOFT AND 20-30KTS OF ISENTROPIC ASCENT ON THE 
290-295K SURFACES WITH A WIDE OPEN GULF WILL TRANSPORT MIXING RATIOS 
OF 2-3 G/KG ACROSS THE STATE...AND SHOULD SEE A LARGE AREA OF SNOW 
CONTINUE TO SURGE NORTH ACROSS THE FORECAST AREA FOR THE ENTIRE 
NIGHT.  EASTERLY 1000-850MB FLOW WITH DELTA T/S 10-12C WILL SUPPORT 
LAKE ENHANCEMENT FOR THE ENTIRE NIGHT AS WELL.  IN ADDITION...AS THE 
SHORTWAVE AND SURFACE LOW APPROACHES FROM THE SOUTHWEST...QG FORCING 
WILL INCREASE AFTER MIDNIGHT AND WIDESPREAD LIGHT SNOW WILL BECOME 
HEAVY.  THE TRACK/TIMING OF THE LOWS PASSAGE WOULD SUGGEST THE 
HEAVIEST SNOW FALLING BETWEEN WED 09-15Z BEFORE SUBSIDENCE STARTS TO 
MOVE IN BEHIND THE SHORTWAVE.  DUE TO THE LONGER DURATION OF 
POSSIBLE LAKE ENHANCEMENT (21Z TUE-15Z WED)...THE FOX VALLEY AND 
LAKE MICHIGAN SHORELINE STAND TO RECEIVE THE MOST SNOW...POSSIBLY UP 
TO 10 TO 14 INCHES USING A SNOW LIQUID RATIO OF 13:1.  SOME 
ENHANCEMENT WILL ALSO BE POSSIBLE ACROSS NORTH-CENTRAL WISCONSIN AS 
WINDS SWING AROUND FROM THE NORTHEAST TO THE NORTHWEST DURING THE 
AFTERNOON.  MORE QUESTION MARKS HERE...AS WINDS SEEM TO BE TRANSIENT 
AND SHOULD NOT GET A STATIONARY DOMINANT LAKE ENHANCED BAND.  
INSTEAD...THINK ANY DOMINANT BAND WILL HAVE POTENTIAL TO DROP A 
QUICK ONE TO THREE INCHES IN ADDITION TO THE SYNOPTIC SNOW.  OUTSIDE 
THE FOX VALLEY...HIGHER SNOW LIQUID RATIOS OF 17:1 STILL SUGGEST 
8-10 INCHES ARE POSSIBLE.  FORTUNATELY...MAX OMEGA IS NOT WELL 
COINCIDENT WITH THE DENDRITIC GROWTH ZONE AND THERE IS NOT MUCH 
ELEVATED INSTABILITY (COULD NOT FIND NEGATIVE EPV). AWAY FROM LAKE 
SUPERIOR LAKE ENHANCEMENT...SNOW WILL BE WINDING DOWN IN THE 
AFTERNOON...BUT NORTHWEST WINDS WILL BE RAMPING UP.  COULD SEE GUSTS 
UP TO 30 MPH INLAND AND 40 MPH NEAR THE LAKE SHORE WHICH WOULD LEAD 
TO BLOWING AND DRIFTING SNOW.  PHEW...ALL THIS SAID...WITH UPGRADE 
WATCH TO A WINTER STORM WARNING FOR THE ENTIRE AREA.

WEDNESDAY NIGHT...MOST OF THE SNOW SHOULD HAVE DISSIPATED/EXITED THE 
AREA BY 00Z THU EXCEPT FOR SNOW SHOWERS OVER N-C WISCONSIN AND 
POSSIBLY A FEW FLURRIES ELSEWHERE.  EVEN THE LAKE ENHANCED SNOWS 
WILL BE WINDING DOWN THOUGH...AS WINDS BACK AROUND TO THE WEST AND WILL 
CONFINE ANY BANDS TO THE UPPER PENINSULA.  MAY ACTUALLY SEE SOME 
CLEARING SKIES LATE ACROSS CENTRAL WISCONSIN.  HOWEVER...FRIGID 
ARCTIC AIR (850MB TEMPS -20C) BROUGHT IN BY BRISK WEST WINDS WILL 
DROP TEMPS NEAR ZERO DEGREES EVERYWHERE BY MORNING.  WIND CHILL 
READINGS MAY APPROACH 20 BELOW OVER CENTRAL WISCONSIN.  

THURSDAY THROUGH MONDAY...LOW PRESSURE WILL PULL AWAY TO THE EAST OR 
NORTHEAST ACROSS QUEBEC ON THURSDAY...WHILE HIGH PRESSURE MOVES 
ACROSS THE AREA.  BREEZY WEST-NORTHWEST WINDS WILL CONTINUE TO 
FUNNEL ARCTIC AIR ACROSS THE STATE...KEEPING H850 TEMPS IN THE -20 
TO -25C RANGE.  AS A RESULT...TEMPS WILL STRUGGLE TO GET OUT OF THE 
SINGLE DIGITS ABOVE ZERO AND WILL CONTINUE THE TREND OF LOWERING MAX 
TEMPS...BY ONLY A DEGREE OR TWO THOUGH.  THE COLDEST NIGHT LOOKS TO 
BE THURSDAY NIGHT AS THE PRESSURE GRADIENT SEEMS TO SLACKEN 
SOMEWHAT...BUT STILL LOOKS LIKE THERE WILL BE ENOUGH WIND TO PREVENT 
TEMPS FROM REALLY PLUMMETING (LIKE BELOW -20F).  SOME MODERATION OF 
THE ARCTIC AIR WILL OCCUR ON FRIDAY AS THE POLAR VORTEX DROPS INTO 
SOUTH-CENTRAL CANADA AND WINDS BACK TO MORE OF A SOUTHERLY DIRECTION 
AHEAD OF AN ASSOCIATED WEAK BOUNDARY.  WILL SIDE A LITTLE MORE ON 
THE WARMER SIDE OF GUIDANCE FOR FRIDAY...BUT TEMPS IN THE TEENS 
STILL LOOK APPROPRIATE.  THE ARCTIC BOUNDARY MOVES ACROSS THE REGION 
ON SATURDAY OR EARLY SATURDAY NIGHT WITHOUT MUCH MOISTURE TO WORK 
WITH.  WILL KEEP A DRY FORECAST IN TACT.  ARCTIC HIGH THEN BUILDS IN 
SUNDAY INTO MONDAY.  STILL SEEING WEAK SIGNALS OF CONFLUENT FLOW 
OVER THESE TWO DAYS...BUT NOT ENOUGH CONFIDENCE TO ADD PRECIP.  
HIGHS POSSIBLY BACK INTO THE 20S.

AVIATION...EXPECT SOME MVFR CEILINGS FROM LAKE EFFECT CLOUDS
DURING THE EVENING...BUT THESE SHOULD DIMINISH ONCE WINDS ALOFT
BACK AND NO LONGER BECOME FAVORABLE FOR THE LOWER CLOUDS AND
ASSOCIATED LIGHT SNOW SHOWERS/FLURRIES. OTHERWISE MVFR CEILINGS TO
THE SOUTH OF THE FORECAST AREA APPEARED TO BE DEPARTING TO THE
EAST. AS A RESULT...VFR CIGS/VSBYS ARE EXPECTED TO PREVAIL
THROUGHOUT THE NIGHT. AFTER THAT CIGS START TO LOWER AS THE WINTER
STORM APPROACHES. MVFR CONDITIONS WILL RAPIDLY DETERIORATE TO
IFR...MAINLY DUE TO LOWER VSBYS WITH THE SNOW...BEFORE CIGS ALSO
LOWER.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM NOON TUESDAY TO MIDNIGHT CST WEDNESDAY 
NIGHT FOR WIZ030-031-035>040-045-048>050.

WINTER STORM WARNING FROM 3 PM TUESDAY TO MIDNIGHT CST WEDNESDAY 
NIGHT FOR WIZ005-010>013-018>022-073-074.

&&

$$