FXUS63 KGRB 070433 AAA
AFDGRB

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GREEN BAY WI
1033 PM CST SUN DEC 6 2009

.UPDATE...MAIN SFC LOW CURRENTLY MOVG INTO CNTRL MO...WITH BEST
PRESSURE FALLS HEADING TOWARD THE OHIO VALLEY. MAIN S/W AND JET
ENERGY ALSO APPEARS POISED TO PASS TO OUR SOUTH. SFC OBS SHOW
DEVELOPING NORTH WINDS...WITH VERY DRY AIR SITUATED UPSTREAM
OVER NE WI...WHERE DEW POINTS ARE IN THE SINGLE DIGITS. AREA
SOUNDINGS ALSO SHOW MEAGER MOISTURE...WITH PRECIPITABLE WATER
VALUES ONLY IN THE 0.20-0.30 RANGE. RADAR AND OBS INDICATED
WIDESPREAD LGT SNOW OVER IA...WITH MOST LOCATIONS REPORTING VSBYS
IN THE 1-2SM RANGE. MOST OF THE EVG SNOWFALL REPORTS FROM IA
INDICATED ACCUMS OF 2 INCHES OR LESS. 00Z MODELS ARE IN GOOD
AGREEMENT...AND FOCUS THE BEST QPF A BIT FARTHER SOUTH...OVER
OUR FAR SOUTHEAST COUNTIES.

GIVEN THE CURRENT OBSERVATIONAL AND MODEL TRENDS...HAVE OPTED TO
TRIM OUTAGAMIE...BROWN AND DOOR OUT OF THE ADVISORY...WITH ACCUMS
ONLY EXPECTED TO BE IN THE 1-2 INCH RANGE. SLIPPERY CONDITIONS
WILL STILL OCCUR IN THESE COUNTIES FOR THE MORNING COMMUTE...BUT
ACCUMS ARE A BIT TOO LOW TO JUSTIFY KEEPING THE ADVISORY. FARTHER
SOUTH...STILL SEE ENOUGH SUPPORT TO WARRANT KEEPING THE ADVSY...
ESP OVER SOUTHERN WINNEBAGO...SOUTHERN CALUMET...AND KEWAUNEE AND
MANITOWOC COUNTIES...WHERE SOME LK-ENHANCEMENT SHOULD OCCUR LATE
TONIGHT INTO MONDAY MORNING. WOULD NOT BE SURPRISED TO SEE LCL
5 INCH AMOUNTS IN MANITOWOC COUNTY.

NEW MODELS ALSO SHOW STRONG SUPPORT FOR THE TUES/WEDS WINTER STORM
WATCH...WITH 24 HOUR QPF AMOUNTS AROUND AN INCH OVER EC WI DURING
THE HEART OF THE EVENT.

KIECKBUSCH
&&

.PREV DISCUSSION...ISSUED AT 335 PM CST SUN DEC 6 2009...

SHORT TERM...TONIGHT AND MONDAY. 

FORECAST FOCUS IS ON SNOW FOR LATE TONIGHT AND MONDAY MORNING.

AT 18Z A WEAK SURFACE FRONT EXTENDED FROM NEAR CEDAR GROVE TO
OKLAHOMA. CLOUDS...THAT PRODUCED SOME FLURRIES EARLY THIS
MORNING...DEPARTED THE FORECAST AREA. CLOUDS AND FLURRIES FROM
LAKE SUPERIOR SPREAD ACROSS THE NORTHERN PART OF THE
AREA...OTHERWISE PARTLY CLOUDY TO MOSTLY SUNNY CONDITIONS
PREVAILED. 

12Z MODELS CONTINUED TO SHOW A WEAK LOW PRESSURE SYSTEM MOVING
NORTHEAST ALONG THE FRONT AND PASSING SOUTHEAST OF THE CWA ON
MONDAY. SHORT WAVE ENERGY WAS FORECAST TO REMAIN SOUTH OF THE
FORECAST AREA. MODELS HAD THE NORTHERN EDGE OF THEIR QPF FIELDS
SLIGHTLY NORTH OF GREEN BAY AND COORDINATION GRAPHICS FROM HPC
KEPT THEIR 1 INCH CONTOUR BETWEEN GREEN BAY AND APPLETON. LAKE
EFFECT IN EASTERN WISCONSIN REMAINS QUESTIONABLE SINCE SURFACE TO
850MB HAS TOO MUCH SHEAR...SO LAKE EFFECT IS LIKELY TO BE RATHER
LOW TOPPED...SURFACE TO 925MB HAS SIGNIFICANT DELTA T VALUES WITH
LESS SHEAR. CONTRIBUTION FROM LAKE EFFECT IS LIKELY TO BE GREATEST
IN MANITOWOC COUNTY AND SOUTHERN KEWAUNEE COUNTY. KEPT THE SNOW
ADVISORY GOING THAT WAS ISSUED YESTERDAY. THE FACT THAT THIS
SHOULD BE THE FIRST ACCUMULATING SNOW IN THE MOST POPULOUS PART
OF THE FORECAST AREA DURING THE MORNING COMMUTE HOURS TIPPED ME
OVER TO THE ADVISORY SIDE OF THE FENCE.

EXPECT A CHANCE OF SNOW SHOWERS IN VILAS COUNTY THROUGH MONDAY
WITH 850MB COLD ADVECTION AND SOME FLURRIES ALREADY FALLING THERE.
WINDS BACK DURING THE AFTERNOON ON MONDAY...SO ANY LAKE EFFECT
SHOULD BE WINDING DOWN LATER IN THE DAY.

LONG TERM...MONDAY NIGHT THROUGH NEXT SUNDAY.

THE UPPER AIR PATTERN ACROSS NORTH AMERICA LOOKS AMPLIFIED IN 
TYPICAL WINTER TIME FASHION OVER THE NEXT WEEK.  LARGE OMEGA 
BLOCKING OVER ALASKA AND NW CANADA WILL LEAD TO DOWNSTREAM TROUGHING 
OVER THE WESTERN CONUS INTO THE GREAT LAKES REGION UNTIL THE END OF 
THE WEEK BEFORE THE AXIS OF LOWER HEIGHTS RETREATS NORTH INTO CANADA.  
AS A RESULT...TEMPERATURES THIS UPCOMING WEEK LOOK NEAR OR BELOW 
NORMAL...WITH THE POTENTIAL FOR THE SEASON'S FIRST MAJOR WINTER 
STORM (MORE DETAILS BELOW).  WILL TAKE A BLEND OF THE 00Z ECMWF AND 
06Z GFS WEDNESDAY THROUGH FRIDAY BEFORE LEANING MORE ON THE GFS ENSEMBLE 
MEAN.

MONDAY NIGHT...HIGH PRESSURE WILL BE PRESENT IN THE LOW LEVELS 
WITHIN A LIGHT WIND REGIME.  THESE WINDS MAY BE TOO LIGHT FOR LAKE 
EFFECT OFF LAKE SUPERIOR AND WILL TRIM BACK SOMEWHAT (STILL LEAVE 
SOME FLURRIES).  AFTER MIDNIGHT...WILL START TO SEE HIGH AND 
MID-CLOUDS ARRIVE AHEAD OF A DEVELOPING STORM SYSTEM OVER THE 
PLAINS.  

TUESDAY AND TUESDAY NIGHT...HIGH PRESSURE WILL BE INITIALLY IN 
CONTROL...BUT TROUBLE WILL BE LURKING UPSTREAM OVER THE WEST-CENTRAL 
PLAINS.  A VIGOROUS SHORTWAVE AND ASSOCIATED SURFACE LOW WILL BE 
EJECTING OUT OF THE ROCKIES BY TUESDAY AFTERNOON...INTO THE CENTRAL 
PLAINS BY TUESDAY EVENING...AND THE MID-MISSISSIPPI VALLEY BY 
TUESDAY NIGHT.  AHEAD OF THE LOW...SW FLOW ALOFT WILL BRING IN MID 
AND UPPER LEVEL MOISTURE AND WILL BE SEEING CLOUDS THICKEN AND LOWER 
THROUGH THE MORNING.  20-30KTS OF ISENTROPIC ASCENT ON THE 280-295K 
SURFACES WILL INCREASE DURING THE AFTERNOON WITH CONDENSATION 
PRESSURE DEFICITS FALLING TO LESS THAN 5 MB BY 00Z WED. AS 
RESULT...EXPECT SNOW TO MOVE INTO THE REGION IN TIME FOR RUSH HOUR 
TUESDAY AFTERNOON WITH LOCATIONS SOUTH OF AUW/GRB POSSIBLY PICKING 
UP TO AN INCH OF SNOW.  THE SNOW THEN SPREADS NORTHWARD TUESDAY 
EVENING ACROSS ALL OF NORTH-CENTRAL AND NORTHEAST WISCONSIN.  MIXING 
RATIOS INCREASE ON THE 290K SURFACES BETWEEN 2 AND 2.5 G/KG...WHICH 
WOULD EQUATE TO 2 TO 4 INCHES OF SNOW.  HIGHER AMOUNTS SHOULD FALL 
OVER THE FOX VALLEY AND THE LAKE SHORE OF LAKE MICHIGAN (3-6 
INCHES?)DUE TO LAKE ENHANCEMENT WHERE A PERSISTENT SE TO EAST FLOW 
WILL BE FOUND.  ON THE DOWN SIDE...DO NOT SEE A PERSISTENT 
CROSS-HAIR SIGNATURE IN BUFKIT PROGGED SOUNDINGS...AND ELEVATED 
INSTABILITY IS ALSO QUESTIONABLE.  BUT WITH A OPEN GULF OF MEXICO 
AND DURATION OF FORCING LEADS ME TO SIDE WITH HIGHER AMOUNTS.  

WEDNESDAY THROUGH SUNDAY...OPERATIONAL MODEL COMPOSITE WOULD BRING 
THE STRONG SHORTWAVE AND ASSOCIATED SURFACE LOW ACROSS NORTHEAST 
ILLINOIS AND CENTRAL LOWER MICHIGAN ON WEDNESDAY. QG FORCING WILL BE 
THE STRONGEST DURING THE MORNING HOURS...AND WILL GRADUALLY 
TRANSITION TO DEFORMATION/FGEN FORCING AS WINDS TRANSITION TO THE 
NORTH AND NORTHWEST BY AFTERNOON.  STRONG WINDS WILL ALSO DEVELOP BY 
AFTERNOON WITH THE INFILTRATION OF ARCTIC AIR LEADING TO BLOWING AND 
DRIFTING OF SNOW.  THE GARCIA METHOD WOULD SUGGEST A 4-8 INCH SNOW 
AMOUNT WOULD BE POSSIBLE AS LONG AS THE TRACK/TIMING SUSTAINS 
ITSELF...WHICH IS NOT EXACTLY A CERTAINTY GIVEN THE SHORTWAVE IS 
JUST OFF SHORE OF THE NW PAC COAST.  THERE ARE ALSO QUESTIONS WITH 
STABILITY ALOFT (ECMWF CONSIDERABLY MORE STABLE THAN THE GFS)...BUT 
IT MAY NOT MATTER GIVEN A PROLONGED EASTERLY FLOW (12 HRS?) LEADING 
TO LAKE ENHANCEMENT (DELTA T/S 10-12C).  HIGHEST TOTAL AMOUNTS LOOK 
TO BE NEAR THE LAKE MICHIGAN SHORE LINE (6-10 INCHES?) BY WEDNESDAY 
AFTERNOON IF THE ABOVE DETAILS HOLD TRUE TO FORM.  SOME ENHANCEMENT 
MAY ALSO OCCUR OVER FAR N-C WISCONSIN WEDNESDAY AFTERNOON AS WINDS 
SHIFT TO THE NW...BUT THINK THIS WILL BE SHORT IN DURATION AS THE 
WIND DIRECTION WILL BE SHIFTING.

IN COLLABORATION WITH SURROUNDING OFFICES...WILL HOIST A WINTER 
STORM WATCH FOR THE ENTIRE AREA...AND WILL KEEP IT SIMPLE BY 
STARTING THE WATCH AT 00Z.  LATER SHIFTS CAN REFINE THE TIMING BASED 
ON THE LATEST MODEL AND OBSERVATIONAL TRENDS.  THE LEAST CHANCE OF 
SEEING WARNING CRITERIA SNOW WILL BE ACROSS CENTRAL AND 
NORTH-CENTRAL WISCONSIN...BUT STAY TUNED TO LATER FORECASTS FOR ANY 
CHANGES.

THE SURGE OF ARCTIC AIR WILL CONTINUE TO WRAP INTO THE REGION 
WEDNESDAY NIGHT DROPPING 850MB TEMPS TO AROUND -20C ALONG WITH A 
30-35KTS AT THIS HEIGHT.  DEFINITELY LOOKING AT SOME LOW WIND CHILLS 
WEDNESDAY NIGHT INTO THURSDAY...PERHAPS NOT ADVISORY CRITERIA BUT IT 
COULD BE CLOSE.  HIGHS THOUGH WILL STRUGGLE TO REACH INTO THE TEENS 
ON THURSDAY THOUGH.  THE FRIGID AIR REMAINS IN PLACE THURSDAY NIGHT 
BEFORE MODERATION SLOWLY OCCURS FRIDAY INTO SATURDAY WITH HIGH 
PRESSURE IN CONTROL.  QUIET CONDITIONS WILL CONTINUE INTO 
SUNDAY...BUT WILL HAVE TO WATCH FOR CONFLUENT MID-LEVEL FLOW OVER 
THESE DAYS WHICH COULD LEAD TO LIGHT PRECIP.  CONFIDENCE JUST ISNT 
THERE YET TOO INCLUDE LIGHT PRECIP CHANCES FOR LATER PERIODS.

AVIATION...MAINLY VFR CONDITIONS THIS EVENING AWAY FROM LAKE SUPERIOR.
CLOUDS WILL INCREASE AND LOWER DURING THE NIGHT AS THE LOW
MOVES INTO NORTHERN ILLINOIS. SNOW EXPECTED OVER SOUTHERN TAF SITES BY
MIDNIGHT...WITH VIS/CIGS LAKESHORE TO FOX VALLEY DROPPING INTO
IFR/LIFR RANGE AROUND 06Z.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL NOON CST MONDAY FOR WIZ040-048>050.

WINTER STORM WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY 
EVENING FOR WIZ005-010>013-018>022-030-031-035>040-045-048>050-
073-074.

&&

$$