Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 171634
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1134 AM CDT WED SEP 17 2014

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 334 AM CDT WED SEP 17 2014

A BACKDOOR COLD FRONT WILL DROP SOUTH ACROSS THE REGION LATER
THIS AFTERNOON AND TONIGHT. MOISTURE IS LACKING SO EXPECT ONLY CLOUDS AS
THE FRONT GOES BY. TEMPERATURES MAY FALL LATE IN THE AFTERNOON IN
THE FAR NORTH BUT OTHERWISE HIGHS WILL BE IN THE 60S TO NEAR 70.
THE FRONT WILL MOVE SOUTH OF THE AREA TONIGHT BUT EXTENT OF
CLEARING IS UNCERTAIN. IF SKIES CLEAR TEMPERATURES WILL FALL INTO
THE UPPER 20S TO LOW 30S IN THE FAR NORTH RESULTING IN A FROST OR
FREEZE. THURSDAY SHOULD BE PARTLY SUNNY AND A LITTLE COOLER
ESPECIALLY NEAR THE LAKE AND BAY.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 334 AM CDT WED SEP 17 2014

MODELS STILL IN FAIRLY DECENT AGREEMENT WITH THE OVERALL PATTERN
ACROSS THE CONUS THROUGH THE PERIOD. TROUGHS OVER THE EAST AND
WEST COAST WITH RIDGING OVER THE CENTRAL U.S. WILL BE REPLACED
BRIEFLY WITH ZONAL FLOW OVER THE NORTHERN U.S. ON FRIDAY INTO
SATURDAY. A STRONG RIDGE IS THEN FORECAST TO DEVELOP OVER THE
ROCKIES/ALBERTA/SASKATCHEWAN EARLY NEXT WEEK...WITH A DEEP TROUGH
DIGGING INTO THE EASTERN GREAT LAKES. MODELS HAVE TRENDED TOWARD
THE LESS PROGRESSIVE ECMWF...AND SHOW A CLOSED/CUT OFF LOW
PRESSURE SYSTEM...OR NEARLY CLOSED/CUT OFF LOW...SITTING OVER THE
EASTERN GREAT LAKES EARLY NEXT WEEK. TEMPS LOOK TO BE NEAR OR
SLIGHTLY ABOVE NORMAL AS THE FLOW BECOMES MORE ZONAL...THEN WILL
FALL BACK BELOW NORMAL EARLY NEXT WEEK.

SURFACE HIGH PRESSURE WILL BE SLIDING EAST OF THE AREA THURSDAY
NIGHT...WITH STRONG RETURN FLOW SETTING UP ON THE BACK SIDE OF THE
HIGH. 850MB TEMPS CLIMB TO BETWEEN 15-20C BY EARLY SATURDAY
MORNING. FRIDAY LOOKS TO BE A BREEZY DAY AS SOUTH/SOUTHWEST WINDS
PICK UP AT THE SURFACE AND ALOFT. AS THE SOUTHERLY FLOW
STRENGTHENS AND MOISTURE INCREASES...WILL SPREAD POPS FROM MAINLY
NORTH CENTRAL WI FRIDAY MORNING...ACROSS THE ENTIRE AREA BY FRIDAY
EVENING. DO THINK THE MAJORITY OF THE WIDESPREAD PRECIP THROUGH
FRIDAY AFTERNOON WILL REMAIN NORTHWEST OF THE FORECAST
AREA...CLOSE TO THE APPROACHING COLD FRONT...SHORTWAVE...LOW LEVEL
JET...AND HEIGHT FALLS. AS THESE FEATURES APPROACH AND CROSS THE
AREA...WILL CONTINUE WITH LIKELY POPS ON FRIDAY NIGHT INTO
SATURDAY. IT SHOULD BE NOTED THE 00Z ECMWF...AND TO SOME EXTENT
THE 00Z GEM AND 00Z GFS ARE SHOWING THE MAJORITY OF THE PRECIP
ENDING BY EARLY SATURDAY MORNING AS THE FRONT PUSHES THROUGH.
LATER FORECASTS MAY HAVE TO TRIM BACK POPS ON SATURDAY IF THIS
REMAINS THE CASE. 925MB TEMPS SUPPORT HIGHS IN THE LOW 80S ACROSS
THE SOUTH ON SATURDAY...BUT WILL NOT GO THAT WARM AS TOO MUCH
CLOUD COVER THE CHANCES FOR PRECIP WILL LIMIT SURFACE HEATING
AHEAD OF THE FRONT. HOWEVER...IF THERE IS SOME CLEARING...THE WARM
TEMPS ALOFT WOULD ALLOW TEMPS TO REALLY CLIMB EVEN BEHIND THE
FRONT.

SOME LOCALLY HEAVY RAINS WILL BE POSSIBLE FRIDAY NIGHT INTO
SATURDAY AS PRECIPITABLE WATER VALUES CLIMB TO OVER 1.5 INCHES.
SOME OF THIS MOISTURE MAY ACTUALLY BE FROM THE REMNANTS OF
TROPICAL STORM ODILE...WHICH IS GETTING PULLED OUT OF THE
SOUTHWEST U.S. IN THE STRONG SOUTHWEST FLOW AT MID-UPPER LEVELS.
AS FOR SEVERE WEATHER CHANCES...MODELS CONTINUE TO SHOW SOME
INSTABILITY...ANYWHERE BETWEEN 500-1000 J/KG...DECENT DEEP LAYER
SHEAR OF 35-50 KTS...AND POTENT SHORTWAVE TROUGH CROSSING THE
WESTERN GREAT LAKES ON SATURDAY. STILL THINK THE AMOUNT OF
INSTABILITY WILL BE LIMITED THROUGH...DUE TO MORNING CONVECTION
AND CLOUD COVER. LATEST TIMING OF THE FRONT WOULD SUPPORT THE
STRONGER STORMS STAY SOUTH OF THE FORECAST AREA AS WELL.

CYCLONIC FLOW WILL SET UP SATURDAY NIGHT INTO SUNDAY NIGHT...AS
THE UPPER TROUGH DIGS OVER THE GREAT LAKES REGION...AND A SURFACE
LOW TRACKS/DEEPENS AS IT EXITS INTO EASTERN CANADA. PLENTY OF
LINGERING MOISTURE IN THE NORTHWEST/CYCLONIC FLOW...SO WILL KEEP
SOME SMALL CHANCES FOR SHOWERS...ALONG WITH SOME CLOUDS...
ESPECIALLY OVER THE NORTH. HIGH PRESSURE WILL SETTLE OVER THE AREA
NEXT TUESDAY AND WEDNESDAY...WITH DRY WEATHER AND SLOWLY
MODERATING TEMPS EXPECTED.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1133 AM CDT WED SEP 17 2014

A BACKDOOR COLD FRONT WILL DROP SOUTH ACROSS THE REGION
LATE THIS AFTERNOON AND EVENING. MOISTURE IS LACKING SO EXPECT ONLY
CLOUDS AS THE FRONT GOES BY. PLENTY OF MVFR CIGS BEHIND THE
FRONT...AND THINK THESE CIGS WILL MAKE IT INTO THE NORTH-CENTRAL AND
CENTRAL WISCONSIN TAF SITES.  SOME CLEARING IS LIKELY ACROSS
NORTH-CENTRAL WISCONSIN LATE...WHICH WILL RESULT IN A FROST OR
FREEZE. SKIES WILL BECOME MOSTLY CLOUDY ONCE AGAIN THURSDAY
MORNING OVER N-C WISCONSIN WITH MVFR CIGS...BUT PARTLY SUNNY
FARTHER EAST.

&&

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

$$

SHORT TERM.....RDM
LONG TERM......BERSCH
AVIATION.......MPC





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