Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 032027
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
327 PM CDT SUN MAY 3 2015

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND MONDAY
ISSUED AT 327 PM CDT SUN MAY 3 2015

TIMING AND INTENSITY OF THUNDERSTORMS ARE THE MAIN CONCERNS DURING
THIS PART OF THE FORECAST.

A COLD FRONT MOVED INTO EXTREME NORTHWEST WISCONSIN THIS
AFTERNOON AND RADAR AND LIGHTNING DETECTION DATA INDICATED A LINE
OF THUNDERSTORMS AHEAD OF THE FRONT ACROSS THE FAR NORTHWEST PART
OF THE STATE...ALONG WITH WIDESPREAD CONVECTION IN UPPER
MICHIGAN...AT 1945Z. LOCAL MESOANALYSIS GRAPHICS WERE SHOWING
1000+J/KG OF MUCAPE IN NORTH CENTRAL WISCONSIN WITH LITTLE TO NO
CIN SINCE ABOUT 16Z. BY 19Z MUCAPE VALUES ACROSS MOST OF THE REST
OF THE AREA WERE MAINLY IN THE 250-1000J/KG RANGE...WITH LESS THAN
250J/KG GENERALLY EAST OF A LINE FROM ABOUT WAUSAUKEE TO OSHKOSH.

WOULD EXPECT STORMS TO CONTINUE AS THE FRONT REACHES THE UNSTABLE
AIR IN THE NORTHERN PART OF THE STATE. 12Z MODELS GENERALLY
SHOWED QPF SPREADING ACROSS THE ENTIRE AREA BETWEEN 18Z AND 00Z
MONDAY. BUT MESOSCALE MODELS...ARW/HRRR...DID NOT HAVE
PRECIPITATION REACHING NORTH CENTRAL WISCONSIN UNTIL SHORTLY
BEFORE 00Z MONDAY WITH ONLY ISOLATED SMALL VALUES OF QPF ACROSS
THE REST OF THE AREA. MESO MODELS APPEARED TO BE DOING A BETTER
JOB OF HANDLING THE SITUATION SO HAVE SLOWED THE PROGRESSION OF
THE CONVECTION ACROSS THE AREA.

SPC HAS KEPT THE MAJORITY OF THE AREA IN A SLIGHT RISK FOR SEVERE
STORMS THIS AFTERNOON AND EVENING. WBZ HEIGHTS AT 20Z RANGED FROM LESS
THAN 7500FT IN NORTH CENTRAL WISCONSIN TO MORE THAN 9000FT IN EAST
CENTRAL WISCONSIN. 0-6KM SHEAR ACROSS THE NORTH WAS MAINLY
25-35KTS. THERE IS NOT QUITE AS MUCH INSTABILITY AS MODELS SHOWED
YESTERDAY...SHEAR WAS NOT ALL THAT IMPRESSIVE AND THERE IS NOT A
LOT OF UPPER SUPPORT AVAILABLE...SO STRENGTH OF THE STORMS IS A
BIT UNCERTAIN.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY
ISSUED AT 327 PM CDT SUN MAY 3 2015

THE TRAILING END OF THE COLD FRONT WILL STALL OVER NORTHERN
ILLINOIS AND SERVE AS A WEAK FOCAL POINT FOR SHOWERS DURING THE
FIRST HALF OF THE WEEK AS IT GRADUALLY PUSHES NORTH-NORTHEAST OVER
WISCONSIN AND WASHES OUT. MEANWHILE...A BROAD SFC-500MB HIGH
PRESSURE RIDGE WILL SPREAD IN FROM THE WEST AS THE WEEK
PROGRESSES. THE RIDGE AXIS WILL MOVE EAST OF WISCONSIN BY THE END
OF THE WORK WEEK. GFS AND ECMWF MODELS ARE IN AGREEMENT THAT
WISCONSIN WILL THEN REMAIN UNDER THE UNSTABLE WEST SIDE OF THE
RIDGE THROUGH THE WEEKEND...ENABLING GULF MOISTURE TO ADVECT INTO
WISCONSIN FROM THE SOUTHWEST...ALONG WITH A DISTURBANCE OR TWO.



ML.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 104 PM CDT SUN MAY 3 2015

CONDITIONS WERE VFR ACROSS THE AREA AT MIDDAY AS A COLD FRONT WAS
JUST ENTERING THE NORTHWEST CORNER OF WISCONSIN. CONFIDENCE HAS
WANED WITH REGARD TO FORECAST OF CONVECTION ACROSS THE AREA THIS
AFTERNOON INTO MONDAY MORNING. ONLY MADE MINOR ADJUSTMENTS TO
TIMING FROM THE PREVIOUS FORECAST FOR NOW. THE MOST UNSTABLE
CONDITIONS APPEARED TO BE ACROSS NORTH CENTRAL WISCONSIN WHERE
MUCAPE VALUES WERE 500+ J/KG WITH LITTLE TO NO CIN THERE...BUT NO
CONVECTION WAS YET EVIDENT IN THAT AREA. SHOWERS AND ISOLATED
THUNDERSTORMS WERE CONFINED TO MINNESOTA AND EASTERN LAKE SUPERIOR
AT 1745Z. MOST OF THE 12Z MODELS SHOWED QPF WITH THE FRONT GREATLY
EXPANDING DURING THE AFTERNOON TO COVER THE ENTIRE AREA. A QUICK
LOOK AT THE 16Z HRRR INDICATED ISOLATED-SCATTERED LIGHT QPF UNTIL
A MORE SOLID AREA OF PRECIPITATION REACHES NORTH CENTRAL
WISCONSIN. THIS LOOKS LIKE ITS ON TRACK...AT LEAST RIGHT NOW...SO
MAINLY VFR AND DRY THE REST OF THE DAY IF IT REMAINS ON TRACK.

CANNOT RULE OUT CONVECTIVE DEVELOPMENT WITH SPC DAY 1 SEVERE
OUTLOOK INCLUDING MUCH OF THE AREA IN A SLIGHT RISK FOR
SEVERE...WITH POSSIBLE DAMAGING WINDS AND LARGE HAIL THIS
AFTERNOON AND TONIGHT.
&&

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

$$

SHORT TERM.....MG
LONG TERM......ML
AVIATION.......MG





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