FXUS63 KGRB 292104
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
304 PM CST SUN NOV 29 2009

.SHORT TERM...TONIGHT AND MONDAY
CLOUD FORECASTING TRICKY TONIGHT AS MODEL SOUNDINGS SUGGEST 
MOISTURE TRAPPED BELOW AN INVERSION. ENOUGH BREAKS IN THE 
CLOUDS THIS AFTERNOON DUE TO SUBSIDENCE BEHIND DEPARTING
SYSTEM FROM THIS MORNING. HAVE TRENDED MORE TOWARD THE CLOUDIER
MET GUIDANCE FOR TONIGHT...ESPECIALLY OVER THE NORTH WHERE SNOW
FALL FROM THIS MORNING WAS MELTING DURING THE DAY. THERE MAY 
BE MORE BREAKS IN THE CLOUDS FROM MARINETTE TO GREEN BAY AND
OSHKOSH DUE TO DOWN SLOPE EFFECTS. 

NEXT SYSTEM APPROACHES FROM THE NORTHWEST ON MONDAY. 130 KNOT JET
STREAK ENTERS THE CENTRAL UNITED STATES WITH THE REGION POSITIONED
IN THE FAVORABLE LEFT EXIT REGION OF THE JET. THIS IS ANOTHER TRAP
FORECAST LIKE THIS MORNING AS NUMERICAL GUIDANCE SUGGESTING ONLY 10
TO 20 POPS. TIME CROSS SECTIONS AND BUFKIT SOUNDINGS SUGGEST A PERIOD
OF TIME MONDAY AFTERNOON WHERE THE COLUMN WILL SATURATE AND WOULD
PRODUCE SOME LIGHT SNOW. MODELS ALSO SUGGESTING SOME STEEP MID LEVEL
LAPSE RATES AS WELL TO SUPPORT PRECIPITATION ACROSS THE AREA. HAVE
GONE SUBSTANTIALLY ABOVE GUIDANCE FOR PRECIPITATION CHANCES ON
MONDAY BASED ON THE BUFKIT SOUNDINGS. FOLLOWED THE SREF GUIDANCE
FOR HIGHS ON MONDAY AS IT HAS BEEN DOING VERY WELL OF LATE.

.LONG TERM...MONDAY NIGHT THROUGH NEXT SUNDAY...MAIN FCST CONCERNS
INCLUDE COOLER TEMPERATURES LATER IN THE WORK WEEK...AND PSBL
SIGNIFICANT LK-EFFECT SNOW IN VILAS COUNTY LATE WEDS INTO THU NGT.

A 130+ KT JET STREAK WILL BE BISECTING GRB CWA FROM NW TO SE EARLY
MONDAY EVG...WITH LGT SNOW LINGERING OVER NE WI DUE TO JET DYNAMICS.
HAVE ADDED SOME PATCHY LGT SNOW OR FLURRIES TO MAINLY THE NE HALF
OF GRB CWA DURING THE EVG. USED A BLEND OF THE TOP-PERFORMING
MOSGUIDEBC AND MAV GUIDANCE FOR MIN TEMPS.

DRY AND MILD CONDITIONS ARE ANTICIPATED ON TUES...AS SOUTH WINDS
DEVELOP AHEAD ON AN APPROACHING COLD FRONT. MIXING THROUGH 925-900
MB SUPPORT MUCH ABOVE NORMAL TEMPS RANGING FROM THE UPPER 30S FAR
NORTH TO TO THE MIDDLE 40S SOUTH.

THE COLD FRONT WILL PASS THROUGH TUES EVG...WITH LITTLE OR NO PCPN
ACCOMPANYING IT. AS AN UPPER TROF AND ASSOCIATED SECONDARY COLD
FRONT/TROF MOVE INTO OUR NW COUNTIES ON WEDS...SNOW SHOWERS WILL
BE ON THE INCREASE...ESP IN VILAS COUNTY...WHERE LK-EFFECT SNOW
SHOULD DEVELOP LATE IN THE DAY AS WINDS VEER NW.

WEDNESDAY NIGHT THROUGH NEXT SUNDAY...DUE TO MODEL DIFFERENCES IN
THE LATER PERIODS...HPC FAVORED USING A BLEND OF SEVERAL MEDIUM
RANGE MODELS TODAY. THIS SUPPORTS A LARGE UPPER TROF THAT
GRADUALLY SHIFTS EAST THROUGH THE GREAT LKS RGN DURING THE
PERIOD...ACCOMPANIED BY COLDER TEMPERATURES AND SCT SNOW SHOWERS
OR FLURRIES THROUGH THE MID TO LATE PART OF THE WORK WEEK.
CONFIDENCE IS INCREASING FOR A DECENT LK-EFFECT SNOWFALL EVENT
OVER VILAS CO...ESP DURING THE WEDS NGT/THU PERIOD.

MUCH COLDER AIR...WITH H8 TEMPS RANGING FROM -10 TO -14 C...WILL
BE ENTRENCHED OVER THE RGN FOR MOST OF THE EXTENDED PERIOD. THIS
WILL LEAD TO TEMPERATURES MUCH CLOSER TO NORMAL FOR EARLY DECEMBER.
A MINOR MODERATION IN TEMPS MAY OCCUR LATE IN THE WEEKEND AS THE
UPPER TROF SHIFTS EAST AND A BIT MORE SUNSHINE DEVELOPS. OVERALL...
STAYED FAIRLY CLOSE TO HPC/MEX GUIDANCE.

NOT EXPECTING ANY BIG SYNOPTIC-SCALE STORMS DURING THE PERIOD...
HOWEVER A POTENTIALLY SIGNIFICANT LES EVENT MAY BE SHAPING UP FOR
VILAS COUNTY WEDS NGT INTO THU. FOR THE SECOND DAY IN ROW...MODELS
SUPPORT FAVORABLE LOW-LEVEL NNW WINDS...INCREASING INSTABILITY
WITH LK-H8 DELTA-T'S AROUND 20 C...AND THE POTENTIAL FOR A PERIOD
OF SYNOPTIC ENHANCEMENT AS THE UPPER TROF AXIS SWINGS THROUGH.
HAVE BUMPED POPS UP TO LIKELY FOR VILAS COUNTY...AND PLAN TO BEEF
UP THE WORDING UP IN THE HAZARDOUS WEATHER OUTLOOK THIS AFTERNOON.
ELSEWHERE ACROSS THE CWA...THE BEST BET FOR SCT SNOW SHOWERS AND
FLURRIES SHOULD ALSO OCCUR AS THE TROF AXIS MOVES THROUGH WEDS
NGT/THU. OTHERWISE...THE GENERAL COLD AND DRY CHARACTER OF THE AIR
MASS...COMBINED WITH DOWNSLOPE NW FLOW OVER NE/EC WI...SHOULD
PRECLUDE MEASURABLE PCPN OUTSIDE OF THE LK SUPERIOR SNOWBELT
DURING THE REST OF THE LONG-RANGE PERIOD.
&&

.AVIATION...LOW CLOUD FORECASTING TONIGHT WILL BE TRICKY DUE TO 
ABUNDANT LOW LEVEL MOISTURE HANGING AROUND AND TRAPPED BELOW AN
INVERSION LAYER BASED ON MODEL SOUNDINGS. BREAKS IN THE CLOUDS THIS
AFTERNOON DUE TO STRONG SUBSIDENCE BEHIND DEPARTING SYSTEM FROM
THIS MORNING. HAVE TRENDED TOWARD THE CLOUDIER MET GUIDANCE FOR
THE 18Z TAFS DUE TO THE ABUNDANT LOW LEVEL MOISTURE HANGING AROUND
WHICH WILL BE TRAPPED BELOW THE INVERSION. WILL HAVE MVFR/IFR
CEILINGS OVER THE NORTH AND MVFR CEILINGS OVER THE SOUTH. HAVE
SEEN CASES WHERE IT HAS GONE BOTH WAYS AND THE CLOUDS DISAPPEAR
LATE AT NIGHT. SO CONFIDENCE IS NOT HIGH. NEXT SYSTEM APPROACHES
FROM THE NORTHWEST ON MONDAY. MODELS DIVERGE ON TIMING AND
LOCATION OF SOLUTION...BUT THINK BEST CHANCE OF LIGHT SNOW MONDAY
AFTERNOON WILL BE OVER THE FAR NORTH WITH A CHANCE OVER THE
SOUTHEAST. THE SNOW MAY BE MIXED WITH A LITTLE RAIN AT KGRB...KMTW...
KSUE...KATW AND KOSH. WHERE SNOW DOES DEVELOP...EXCEPT MVFR/IFR
CONDITIONS TO DEVELOP. THE SYSTEM SHOULD QUICKLY EXIT THE AREA
MONDAY EVENING. THE PRECIPITATION WILL COME TO AN END WITH 
IMPROVING CEILINGS AND VISIBILITIES AT NORTH CENTRAL AND NORTHEAST
WISCONSIN AIRPORTS.
&&

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

$$
ECKBERG/KIECKBUSCH