Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 010347
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1047 PM CDT SAT APR 30 2016

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND SUNDAY
ISSUED AT 243 PM CDT SAT APR 30 2016

NORTHWARD PROGRESS AND TIMING OF RAIN...THAT WAS ACROSS SOUTHERN
WISCONSIN AT 19Z...ARE THE MAIN CONCERNS DURING THIS PART OF THE
FORECAST.

SURFACE AND 500MB LOWS APPROACHING THE GREAT LAKES REGION FROM
THE PLAINS BROUGHT RAIN TO SOUTHERN WISCONSIN TODAY. THE FORECAST
AREA WAS ALSO IN THE RIGHT ENTRANCE REGION OF A 100+KT 250MB JET
MAX...PROVIDING UPPER LEVEL DIVERGENCE.

DRY AIR IN PLACE OVER THE FORECAST AREA...AS SEEN ON THE 12Z GRB
SOUNDING...WAS CAUSING RAIN TO THE SOUTH TO MAKE SLOW NORTHWARD
PROGRESS TODAY...EVEN WITH APPROACHING 500MB/SFC LOWS AND JET
DYNAMICS. 12Z MODEL RUNS BROUGHT QPF TO AROUND HIGHWAY 29 BY 00Z
SUNDAY...THEN PUSHED IT A LITTLE FARTHER NORTH OVERNIGHT AND KEPT
IT ACROSS ABOUT THE SOUTHERN HALF OF THE STATE FOR AT LEAST SUNDAY
MORNING.

THINK THAT THE DRY AIR ACROSS CENTRAL AND NORTHERN WISCONSIN WILL
SLOW THE RAIN`S NORTHWARD PROGRESS AND KEEP IT FROM GETTING AS FAR
NORTH AS MOST OF THE MODELS PROJECT. AS A RESULT...CHANCE OR
HIGHER POPS WERE GENERALLY CONFINED TO THE SOUTHERN HALF OF THE
FORECAST AREA LATE TODAY THROUGH EARLY SUNDAY MORNING.

CLOUDS AND SOME WIND SHOULD KEEP ANY FROST FROM DEVELOPING...AND
MOST LOCATIONS WILL BE A BIT TOO WARM FOR FROST ANYWAY.
TEMPERATURES INLAND FROM THE LAKE SHOULD BE NEAR NORMAL ON SUNDAY
BUT CLOUDS AND EAST/NORTHEAST SURFACE FLOW WILL KEEP THINGS QUITE
A BIT COOLER CLOSER TO LAKE MICHIGAN.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY
ISSUED AT 243 PM CDT SAT APR 30 2016

MAIN FCST CONCERNS INCLUDE TIMING AND PCPN CHANCES ASSOCIATED WITH
A STRONG COLD FRONTAL PASSAGE IN THE MIDDLE OF THE WEEK...AND
TEMPERATURES THROUGHOUT THE PERIOD.

AN UPPER TROF WILL STILL BE MOVG THROUGH OUR SE COUNTIES ON SUNDAY
EVENING...SO HAVE MATCHED UP WITH SURROUNDING OFFICES AND PLACED
SMALL POPS OVER EAST CENTRAL WI. CLEARING SKIES ARE ANTICIPATED
OVERNIGHT.

HAVE MAINTAINED A DRY FCST ON MONDAY AND MONDAY NIGHT...FOLLOWING
THE NAM/ECMWF IDEA OF KEEPING THE MAIN UPPER LEVEL ENERGY TO OUR
WEST AND SOUTHWEST. HAVE DISCOUNTED THE GFS SOLN...WHICH HAS A
MORE ROBUST S/W TROF MOVG THROUGH THE CWA IN THE AFTERNOON AND
EVENING.

MODELS ARE STILL STRUGGLING WITH THE TIMING OF AN UPPER LOW
DROPPING INTO THE GREAT LAKES REGION AND ASSOCIATED STRONG COLD
FRONTAL PASSAGE DURING THE MIDWEEK PERIOD. ALTHOUGH TRENDS SEEM TO
SUPPORT A FASTER ARRIVAL OF THE FRONT...THE GFS LOOKS TOO FAST
BRINGING IT INTO SOUTHERN WI BY 00Z/WED. HAVE USED A BLEND OF
MODELS...BRINGING THE BEST POPS INTO NORTHERN WI TUES AFTERNOON...
AND ACROSS THE REST OF THE CWA IN THE EVENING.

THE REST OF THE WEEK LOOKS MAINLY DRY...WITH NORTH WINDS BRINGING
MODIFIED CANADIAN AIR INTO THE REGION. AS THE UPPER LOW SLOWLY
DRIFTS EAST LATE IN THE WEEK...INITIALLY COOL TEMPERATURES WILL
MODERATE AND RETURN TO ABOVE NORMAL BY THE WEEKEND.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1047 PM CDT SAT APR 30 2016

MAINLY VFR CIGS AND VSBYS EXPECTED TONIGHT INTO SUNDAY.
TIGHTENING PRESSURE GRADIENT IN THE BOUNDARY LAYER WILL PRODUCE A
PERIOD OF LLWS CONDITIONS OVERNIGHT FOR THE TAF SITES. THIS EVEN
INCLUDES RHI FOR A FEW HOURS. LLWS CONDITIONS BEING CREATED BY A
STORM SYSTEM TRACKING OVER THE MID MISSISSIPPI VALLEY REGION AND
HIGH PRESSURE EXTENDING INTO THE NORTHERN GREAT LAKES. A DECREASING
BAND OF RAIN OVER THE SOUTH HALF OF THE STATE WILL DEPART LATE
SUNDAY MORNING. PATCHES OF MVFR CIGS MAY ALSO EXTEND INTO AREAS
SOUTH OF HIGHWAY 29 OVERNIGHT BEFORE DEPARTING LATER SUNDAY.
&&

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

$$

SHORT TERM.....MG
LONG TERM......KIECKBUSCH
AVIATION.......TDH



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