Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 132257
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
557 PM CDT SAT SEP 13 2014

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND SUNDAY
ISSUED AT 305 PM CDT SAT SEP 13 2014

NO SIGNIFICANT CHANGES TO PREVIOUS FORECAST THROUGH SUNDAY
AFTERNOON.

LARGE AREA OF SCT-BKN SC THAT DEVELOPED BY EARLY AFTERNOON UNDER
THERMAL TROUGH SHOULD GRADUALLY WANE TOWARD EVENING. BKN CLOUDS
DID HOLD TEMPERATURES DOWN A FEW DEGREES THIS AFTERNOON WITH MOST
AREA REACHING THE MIDDLE 50S.

SURFACE HIGH PRESSURE RIDGE WILL CONTINUE TO DRIFT EAST OF THE
FORECAST AREA OVERNIGHT WITH LIGHT SOUTHERLY RETURN FLOW
DEVELOPING AHEAD OF APPROACHING SHORTWAVE TROUGH AND ASSOCIATED
COLD FRONT. SURFACE LOW CURRENTLY LOCATED NEAR LAKE WINNIPEG WITH
TRAILING COLD FRONT EXTENDING SOUTH ACROSS THE EASTERN DAKOTAS LATE
THIS AFTERNOON. EXPECT TO SEE GRADUALL INCREASE IN HIGH CLOUDS
OVERNIGHT AS THIS SYSTEM APPROACHES. SHORT TERM MODEL GUIDANCE IN
FAIRLY GOOD AGREEMENT ON TIMING OF FRONTAL BOUNDARY ACROSS THE
FORECAST AREA DURING THE DAY ON SUNDAY. AS PREVIOUSLY
ADVERTISED...STRONGEST UPPER-LEVEL Q/G FORCING SHOULD REMAIN NORTH
OF THE WISCONSIN-MICHIGAN BORDER WITH PRIMARILY SHALLOW FORCING
ASSOCIATED WITH COLD FRONT. DESPITE VERY LIMITED
MOISTURE...MAJORITY OF MODEL GUIDANCE CONTINUES TO INSIST ON SCT
AREA OF LIGHT SHOWER ACTIVITY...GENERALLY NORTH OF HIGHWAY 29...TO
DEVELOP AHEAD OF THE COLD FRONT FORECAST TO MOVE ACROSS THE AREA
BETWEEN ABOUT 15Z SUNDAY AND 00Z MONDAY. THIS SEEMS QUITE
REASONABLE. FOCUSED SMALL POPS ACROSS ESSENTIALLY THE NORTHERN
THIRD OF THE FORECAST AREA SUNDAY AFTERNOON. AGAIN...SHOWER
ACTIVITY IS EXPECTED TO BE QUITE LIGHT AND SCATTERED AT BEST.
DECENT WAA AHEAD OF THIS SYSTEM SHOULD ALLOW 850 TEMPS TO REACH 5
TO 6 C BY 00Z. THUS...DAYTIME HIGHS SHOULD BE ABLE TO REACH
PERHAPS THE MIDDLE 60S...ESPECIALLY OVER THE SOUTHERN TWO TIERS OF
COUNTIES ON SUNDAY AFTERNOON. OVERALL A FAIRLY PLEASANT DAY WITH
AN INCREASING SOUTHWEST BREEZE OF 10 TO 15 MPH.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY
ISSUED AT 305 PM CDT SAT SEP 13 2014

PCPN TRENDS SUNDAY NIGHT INTO MONDAY...AND TEMPERATURES THROUGH THE
PERIOD...ARE THE MAIN FCST CONCERNS.

A WEAK COLD FRONT AND LFQ OF A 90+ JET MAY GENERATE SCT SHOWERS OVER
FAR NE WI SUNDAY EVENING. THERE WILL BE A BETTER CHANCE OF SHOWERS
OVER OUR SOUTHERN COUPLE TIERS OF COUNTIES (C/EC WI) LATER SUNDAY
NIGHT INTO MONDAY...AS A BAND OF MID-LEVEL FRONTOGENETIC FORCING
SETS UP...FOLLOWED BY A POTENT S/W TROF MOVG THROUGH SOUTHERN WI
ON MONDAY. HAVE BOOSTED POPS A BIT FROM 06Z-18Z/MON...BUT COULD
SEE A NEED TO INCREASE TO LIKELY CATEGORY OVER OUR SOUTHERN TIER
BEFORE ALL IS SAID AND DONE.

HIGH PRESSURE WILL BUILD INTO THE RGN MONDAY NIGHT INTO TUESDAY...
WITH A WEAK COLD FRONT SAGGING SOUTH INTO THE UPPER PENINSULA OF
MICHIGAN LATE TUESDAY AFTERNOON. THIS SHOULD BE A DRY PERIOD...
WITH COOL TEMPERATURES...AND SOME POTENTIAL FOR PATCHY FROST OVER
NC/FAR NE WI.

THE GFS SHOWS THE WEAK COLD FRONT EDGING SOUTH THROUGH GRB CWA
TUESDAY NIGHT INTO WEDNESDAY...THROUGH THE ECMWF IS ABOUT 6 HOURS
SLOWER. ALTHOUGH A FEW LIGHT SHOWERS OR SPRINKLES ARE POSSIBLE...
CONFIDENCE IS TOO LOW TO MENTION POPS ATTM.

HIGH PRESSURE SHOULD REESTABLISH ITSELF OVER THE AREA LATE
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. PATCHY FROST MAY OCCUR
AGAIN OVER THE NORTHWOODS WEDNESDAY NIGHT. MODELS ARE STRUGGLING
WITH THE TIMING OF AN UPPER TROF AND ASSOCIATED COLD FRONT
HEADING TOWARD THE WESTERN GREAT LAKES FRIDAY INTO SATURDAY.
THE 00Z ECMWF HELD OFF THE PCPN THROUGH SATURDAY...BUT THE 12Z
RUN IS MUCH MORE AGGRESSIVE BRINGING PCPN INTO THE REGION THURSDAY
NIGHT AND FRIDAY. WILL NEED TO WATCH TRENDS OVER THE NEXT DAY OR
TWO TO GET A BETTER HANDLE ON THE TIMING.

COOLER THAN NORMAL TEMPS ARE EXPECTED FOR MOST OF THE PERIOD...
WITH A MODEST WARMUP EXPECTED AHEAD OF THE APPROACHING COLD FRONT
LATE IN THE WEEK.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 556 PM CDT SAT SEP 13 2014

ANTICIPATE DIURNAL VFR SCT-BKN CLOUDS TO DIMINISH THIS EVENING.
PATCHY MVFR VSBYS DUE TO FOG POSSIBLE LATE TONIGHT UNDER CLEARING
SKIES...OTHERWISE VFR CONDITIONS EXPECTED TONIGHT INTO SUNDAY. A
WEAK FRONT SLIDING OVER THE AREA ON SUNDAY AFTERNOON AND EVENING
MAY GENERATE A FEW LIGHT SHOWERS OVER MAINLY NORTHERN WISCONSIN.
&&

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

$$

SHORT TERM.....ESB
LONG TERM......KIECKBUSCH
AVIATION.......TDH






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