FXUS63 KGRB 112040
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
240 PM CST FRI DEC 11 2009

.SHORT TERM...TONIGHT AND SATURDAY. FORECAST CHALLENGE TONIGHT
CENTERS ON MIN TEMPS VS CLOUD FORECASTS. AT 20Z...VARIOUS SAT
LOOPS SHOW CLEAR SKIES OVER THE STATE WITH MID LEVEL CLOUDS
GRADUALLY DEVELOPING OVER THE H8 BAROCLINIC ZONE FROM ND TO IA.
SOME PATCHY SC SHOWED UP OVER NRN WI BUT EITHER THIN OR HAS
DIMINISHED IN THE DRY AIR MASS. THIS H8 BAROCLINIC ZONE IS PROGGED
TO WORK INTO THE FORECAST AREA TONIGHT SO EXPECT SOME INCREASE IN
THE CLOUDS AS THE NIGHT WEARS ON. BUT IT APPEARS CLEARS SKIES WILL
BE MORE COMMON THIS EVENING. AS A RESULT THE LIGHT WINDS...FRESH
SNOW COVER AND DRY AIR MASS SHOULD ALLOW TEMPS TO FALL THIS
EVENING. WILL CONTINUE WITH THE GOING FORECAST OF BELOW GUIDANCE
NUMBERS TONIGHT...BUT ACKNOWLEDGE IF CLOUDS CONTINUE TO STRUGGLE
TO WORK IN OR DEVELOP TONIGHT...OVERNIGHT LOWS WILL NEED TO BE
LOWERED EVEN MORE.

CONTINUED CLOUD VS TEMP PROBLEM FOR SATURDAY. ONGOING WAA RETURN
FLOW CONTINUES TO WORK OVER THE REGION. PLENTY OF SNOW COVER TO
THE SOUTH TO INITIALLY LIMIT WARMING. WITH THE WARMING
ALOFT...USUALLY GET A HEALTHY MORNING INVERSION THIS TIME OF THE
YEAR THAT MAY PREVENT THE WARMING TO REACH THE SURFACE.  ACTUALLY
FOR THIS PATTERN THE HIGHER ELEVATION REGION OF THE NORTH MAY END
UP BEING A FEW DEGREES WARMER THAN CENTRAL WISCONSIN LOCATIONS DUE
TO BETTER CHC TO MIX DOWN A BIT MORE WARMER AIR. DEVELOPING SOUTH
WINDS WILL AID WITH HIGHER TEMPS ALONG THE LAKE.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY
WEAK SYSTEM WILL MOVE ACROSS THE REGION SATURDAY NIGHT. MODELS 
HAVE SHIFTED SYSTEM A LITTLE FURTHER SOUTH...THEREFORE WILL HAVE
THE HIGHEST CHANCES ACROSS THE SOUTH. THE PRECIPITATION SHOULD
END AS PATCHY FREEZING DRIZZLE LATE SATURDAY NIGHT OR SUNDAY 
MORNING AS MODELS INDICATED LITTLE MID LEVEL MOISTURE AS THE
SYSTEM MOVES EAST.

ATTENTION THEN TURNS TO SYSTEM FOR SUNDAY NIGHT AND MONDAY. 
THE CANADIAN AND GFS ARE FURTHER NORTH THAN THE WRF/ECMWF. 
AFTER CLOSER INSPECTION OF THE WRF/ECMWF...BELIEF IS THE MODEL
WILL BE FURTHER NORTH THAN INDICATED ON THESE TWO MODELS BASED
ON WHERE THE 850MB THERMAL GRADIENT SETS UP. WILL LEAN TOWARD
THE CANADIAN/GFS SOLUTION FOR NOW WHICH LEADS TO SEVERAL ISSUES
DURING THIS PERIOD. ACROSS THE NORTH...PRECIPITATION SHOULD BE
ALL SNOW. FROM MARINETTE TO WISCONSIN RAPIDS SOUTHWARD...PRECIPITATION
TYPE COULD BECOME AN ISSUE WITH THE POSSIBILITY OF RAIN BEING MIX IN.
THE QUESTION WILL BE HOW MUCH RAIN WILL BE MIXED IN WITH THE SNOW AND
WHAT WILL THE GROUND/ROAD TEMPERATURES BE AT THE TIME OF THE RAIN.
WILL HAVE PREDOMINATELY SNOW FOR NOW...THEREFORE DO NOT THINK RAIN
WILL BE A PROBLEM. UNTIL THE MODELS ARE IN BETTER AGREEMENT WITH
SURFACE LOW TRACK AND HOW IT HANDLE THE LOW LEVEL THERMAL FIELD...
WILL NOT INCLUDE FREEZING RAIN. ANOTHER PROBLEM OVER THE SOUTH
WILL BE THE DRY SLOT ASSUMING THE FURTHER NORTH SOLUTION. THIS
COULD LIMIT PRECIPITATION TOTALS OVER THE SOUTH. WILL MENTION 
THIS FEATURE IN THE HWO...BUT WILL NOT GET IN DETAIL WITH SPECIFICS
AT THIS POINT.

ARCTIC COLD FRONT EXPECTED PUSH ACROSS THE AREA LATE TUESDAY NIGHT
INTO WEDNESDAY MORNING. INTERESTING...THE GFS INDICATING STRONG LIFT
ALONG THE COLD FRONT. HAVE ADDED A CHANCE OF FLURRIES WITH THIS
FEATURE...BUT LATER SHIFTS MAY NEED TO WATCH TO SEE IF THERE WOULD
BE A LITTLE MORE THAN FLURRIES. ARCTIC WILL BE FIRMLY ENTRENCHED
ACROSS THE REGION ON WEDNESDAY. CURRENT BELIEF IS HIGHS WILL BE
WEDNESDAY MORNING WITH STEADY OR SLOWLY FALLING TEMPERATURES DURING
THE AFTERNOON. 

HIGH PRESSURE BUILDS INTO WESTERN WISCONSIN WEDNESDAY NIGHT. WINDS
WILL REMAIN UP OVER THE EAST...BUT WINDS OVER THE WEST WILL DECOUPLE
TOWARDS SUNRISE. THIS WILL LEAD TO BITTERLY COLD TEMPERATURES AND 
WIND CHILLS WEDNESDAY MORNING. HAVE ACCOUNTED FOR THE DECOUPLING
OF WINDS ACROSS THE WEST AND HAVE GONE WELL BELOW GUIDANCE AND 
OTHER OFFICES FOR LOWS TUESDAY NIGHT. WITH FRESH SNOW PACK...LIGHT
WINDS AND CLEAR SKIES ARE PERFECT CONDITIONS FOR RADIATIONAL
COOLING. HAVE GONE BELOW GUIDANCE FOR HIGHS WEDNESDAY DUE TO COLDER
START.
 
A WEAK CLIPPER SYSTEM MAY AFFECT THE REGION THURSDAY OR FRIDAY. HAVE
LEANED TOWARD THE THURSDAY SOLUTION ON THE ECMWF...ALTHOUGH IT HAS
BACKED OFF SOME ON ITS 12Z SOLUTIONS. TEMPERATURES SHOULD BEGIN TO 
MODERATE LATE IN THE WEEK.
&&

.AVIATION...MAINLY VFR CONDITIONS DURING THE PERIOD AS THE SFC
HIGH DRIFTS SOUTH OF THE REGION.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$
TDH/ECKBERG