Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 061152
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
652 AM CDT WED MAY 6 2015

UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 405 AM CDT WED MAY 6 2015

PCPN TRENDS...TEMPERATURES AND FOG/STRATUS POTENTIAL ARE THE MAIN
FCST CONCERNS.

A H8 WARM FRONT WAS LIFTING NORTH ACROSS THE REGION EARLY THIS
MORNING...AND GENERATING SCT/NMRS SHOWERS OVER THE FORECAST AREA.
HAVE NOT SEEN ANY LIGHTNING ANYWHERE IN THE STATE...THOUGH A FEW
STRIKES WERE NOTED IN IOWA. HIGH PRESSURE WAS SHIFTING EAST
THROUGH THE GREAT LAKES...WITH STRONG RETURN FLOW BRINGING
MOISTURE INTO THE UPPER MISSISSIPPI VALLEY. DEW POINTS IN THE
50S AND LOWER 60S WERE REPORTED IN IN SOUTHERN MN...IOWA AND
ILLINOIS...ALONG WITH WIDESPREAD LOW STRATUS AND FOG.

THE ELEVATED WARM FRONT WILL SHIFT NORTH OF GRB CWA LATER THIS
MORNING...SO SHOWERS SHOULD GRADUALLY LIFT NORTH AND WEAKEN.
MODELS CONTINUE TO SHOW INSTABILITY INCREASING OVER OUR SW
COUNTIES THIS AFTERNOON...WHICH MAY LEAD TO SCT TSTM DEVELOPMENT
LATER IN THE DAY. THIS WILL BE DEPENDENT ON WHETHER OR NOT THERE
ARE ENOUGH BREAKS IN THE STRATUS CLOUDS TO ALLOW SUFFICIENT
HEATING. USED A BLEND OF THE TOP PERFORMING GUIDANCE SETS FOR MAX
TEMPS...BUT LOWERED READINGS A FEW DEGREES IN THE SOUTH DUE TO
STRATUS CONCERNS.

ANY LINGERING CONVECTION IN OUR SW COUNTIES SHOULD TEND TO WEAKEN
AFTER SUNSET...BUT AN INCREASING LOW-LEVEL JET AND A WEAK S/W TROF
WILL KEEP A SMALL CHC OF SHRA/TSRA GOING ACROSS OUR WESTERN
COUNTIES OVERNIGHT. LOW TEMPERATURES WILL BE MAINLY IN THE
50S...WITH MID TO UPPER 40S IN FAR NE WI AND ALONG THE LKSHR.

A 35-45 KT LOW-LEVEL JET WILL RESIDE OVER THE REGION ON THURSDAY...
WITH DAYTIME MIXING LEADING TO WINDY CONDITIONS BY LATE MORNING.
MOISTURE AND INSTABILITY WILL INCREASE ACROSS OUR NW COUNTIES
DURING THE AFTERNOON...AS A COLD FRONT APPROACHES FROM MN. HAVE
TRENDED POPS FROM LIKELY NW TO SLIGHT CHC OR DRY IN FAR EASTERN
WI. THE STRONG SOUTH WINDS WILL PULL WARMER AIR INTO THE REGION...
ALLOWING TEMPS TO RISE INTO THE UPPER 70S AND LOWER 80S BEFORE THE
SHOWERS ARRIVE.

HAVE ADDED SOME FOG TO LAKE MICHIGAN AND SOME OF THE SHORELINE
AREAS LATER TODAY THROUGH THURSDAY...AS LOW-LEVEL MOISTURE
ADVECTS OVER THE COLD WATERS. CONFIDENCE IS NOT HIGH ENOUGH TO
ISSUE MARINE FOG ADVISORIES YET. HAVE HELD OFF ON MENTIONING
FOG FOR THE REST OF THE INLAND AREAS...AS MOS GUIDANCE SHOWS
SUBSTANTIAL TEMP/DEW POINT SPREADS CONTINUING OVERNIGHT...AND
BOUNDARY LAYER WINDS INCREASING TO 25 TO 30 KTS. THIS SHOULD
SUPPORT CONTINUED STRATUS DEVELOPMENT INSTEAD OF WIDESPREAD FOG.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 405 AM CDT WED MAY 6 2015

FOCUS WAS GIVEN IN THE LONG TERM FORECAST TO THE THURSDAY NIGHT
AND FRIDAY PERIOD TO TRY AND RESOLVE PCPN CHANCES WITH A FRONTAL
PASSAGE. AFTER FRIDAY...THE LONG TERM BECOMES MUDDLED AND COULD
NOT ADD MUCH DETAIL WITH CERTAINTY.

A SFC COLD FRONT WILL BE PASSING THROUGH THE GREAT LAKES REGION
THURSDAY NIGHT AND FRIDAY. MODELS CONTINUE TO HAVE ISSUES WITH PCPN
AHEAD OF THE FRONT THURSDAY NIGHT. WITHOUT ANY SIGNIFICANT FORCING
AND A BROAD WAA REGIME IN PLACE OVER THE STATE...CANNOT PROVIDE
MUCH DETAIL FROM PREVIOUS FORECAST. THE BETTER CHANCES FOR SHOWERS
AND THUNDERSTORMS LOOKS TO BE IN NORTH CENTRAL WI BEFORE MIDNIGHT
AS A WEAKEN SHORTWAVE PASSES THROUGH AND WASHES OUT.

MODELS HAVE AT LEAST SOME AGREEMENT ON THE TIMING OF A COLD FRONT
ON FRIDAY...WITH THE LATEST GFS40/GEFS BEING A GOOD COMPROMISE.
THE 00Z ECMWF IS STILL A BIT FAST...AND THE NAM80 IS TOO STRONG
BASED ON THE LACK OF UPPER LEVEL SUPPORT. BEST CHANCES FOR PRECIP
FRIDAY MORNING THROUGH EARLY AFTERNOON WITH THE ACTUAL FRONTAL
PASSAGE. DRY AIR NEAR THE SFC SHOULD RESULT IN JUST LIGHT PCPN.
BUFKIT SOUNDINGS THROUGH THURSDAY NIGHT AND FRIDAY MORNING DO SHOW
A MODERATE MIDLEVEL INSTABILITY...THOUGH THE AMOUNT OF INSTABILITY
AND THE STRENGTH OF A CAPPING INVERSION VARIES FROM MODEL TO MODEL.
SOME OF THE STORMS THURSDAY NIGHT AND FRIDAY MORNING COULD BE
STRONG...WITH HIGHER WIND GUSTS POSSIBLE...BUT WITHOUT ANY STRONG
FORCING MECHANISM THE SEVERE THREAT REMAINS MINIMAL.

AFTER THE FRONT SWEEPS THROUGH THE STATE...WEAKENING AS IT MOVES
EAST...IT SHOULD THEN STALL OUT AND SETTLE SOMEWHERE IN NORTHERN
IL THROUGH LOWER MICHIGAN. THE REST OF THE FORECAST WILL DEPEND ON
THE PLACEMENT OF THIS WEAK BOUNDARY AND WAVES OF LOW PRESSURE
RIDING NORTHEAST ALONG IT OUT OF THE SOUTHERN PLAINS. EXPECT
ACTIVE WEATHER WITH OCCASIONAL PRECIP STARTING THIS
WEEKEND...HOWEVER IT DOESNT LOOKS LIKE A WASH OUT THROUGH THE
BEGINNING OF NEXT WEEK THOUGHT NOT ENOUGH CONFIDENCE IN WHEN THIS
WOULD OCCUR TO HIGHLIGHT A DRIER PERIODS. THE UPPER LEVELS ALSO
BECOME MORE UNSETTLED AND WOULD SUPPORT MORE WIDESPREAD AND
HEAVIER RAINS WITH ANY ROUNDS OF PRECIP THAT DO MOVE THROUGH.
GIVEN THE PLACEMENT.

AFTER ONE LAST DAY WITH WELL ABOVE NORMAL CONDITIONS
FRIDAY...TEMPS SHOULD FALL BACK TO NEAR NORMAL AFTER THE COLD
FRONT SWEEPS THROUGH FRIDAY NIGHT AND WILL STAY NEAR NORMAL INTO
NEXT WEEK.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 639 AM CDT WED MAY 6 2015

A BAND OF SHOWERS WILL CONTINUE TO SHIFT NORTH THIS MORNING...AND
SHOULD LIFT INTO THE UPPER PENINSULA OF MICHIGAN BY MIDDAY. ADDITIONAL
SHOWERS AND ISOLD TSTMS ARE POSSIBLE IN CENTRAL AND PARTS OF NORTH
CENTRAL WI LATER THIS AFTERNOON AND TONIGHT...BUT PCPN CHANCES ARE
SMALL. INCREASING LOW-LEVEL MOISTURE AND OVERNIGHT SHOWERS HAVE
CAUSED CIGS TO LOWER TO MVFR ACROSS CENTRAL AND PARTS OF NORTH
CENTRAL AND EAST CENTRAL WI. THE LOW CIGS SHOULD PERSIST FOR
MUCH OF THE MORNING BEFORE DAYTIME HEATING CAUSES THEM TO LIFT TO
VFR.

EXPECT WIDESPREAD MVFR/IFR STRATUS TO DEVELOP AGAIN TONIGHT AS
MOISTURE CONTINUES TO INCREASE. SOME FOG IS ALSO POSSIBLE...BUT
STRONG BOUNDARY LAYER WINDS MAY PREVENT VSBYS FROM DROPPING TOO
MUCH AT INLAND LOCATIONS. MARINE FOG WILL LIKELY IMPACT THE LAKE
MICHIGAN SHORELINE LOCATIONS...INCLUDING THE MTW TAF SITE...
LATER TODAY INTO TONIGHT...AND CONDITIONS COULD DROP TO IFR/LIFR
TONIGHT.

HAVE ADDED SOME LLWS TO THE RHI/AUW/CWA TAF SITES LATE TONIGHT...
AS SSW WINDS INCREASE TO 35 KTS JUST OFF THE SURFACE.

&&

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

$$

SHORT TERM.....KIECKBUSCH
LONG TERM......ALLEN
AVIATION.......KIECKBUSCH






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