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000
FXUS63 KMKX 171626 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1126 AM CDT FRI MAY 17 2013

.UPDATE...

ELEVATED SHOWERS AND THUNDERSTORMS CURRENTLY FROM THE DELLS THROUGH
MILWAUKEE...ASSOCIATED WITH 850MB FRONTOGENESIS/WARM AIR
ADVECTION...WILL VERY GRADUALLY LIFT NORTH THROUGH THE DAY. MODELS
TEND TO MOVE THIS TYPE OF BOUNDARY NORTHWARD TOO QUICKLY BECAUSE
THEY ARE UNDER-DOING THE STRENGTH OF THAT HIGH PRESSURE AREA OVER
SOUTHERN ONTARIO AND LAKE SUPERIOR. SO INCREASED POPS OVER FOND DU
LAC AND SHEBOYGAN AREAS THROUGH THE REST OF THE AFTERNOON. PRECIP
SHOULD TAPER OFF UP THERE THIS EVENING AS THE BOUNDARY CONTINUES
NORTH.

SURFACE WIND SHIFT/DEWPOINT/TEMP GRADIENT BOUNDARY OVER EASTERN IOWA
AND NORTHERN IL WILL LIFT SLIGHTLY NORTHWARD TODAY. HI-RES MODELS
ARE SHOWING THE POTENTIAL FOR SCATTERED SHOWERS AND THUNDERSTORMS TO
DEVELOP ALONG THIS SURFACE BOUNDARY DURING THE LATE AFTERNOON IN
SOUTH CENTRAL WI. THE SMALL AMOUNT OF CAPE AND WEAK SHEAR SUPPORTS
SLOW-MOVING THUNDERSTORMS BUT NOTHING SEVERE. THESE WOULD BE
DIURNALLY DRIVEN AND DIMINISH IN THE EVENING.

TEMPS ARE STARTING OUT COOL THIS MORNING BUT SHOULD GET INTO THE
LOWER 70S IN THE SOUTHWEST FORECAST AREA AND MID 60S NEAR MADISON BY
THE AFTERNOON AS THE CLOUDS SCATTER OUT MORE AFTER THE CONVECTION
LIFTS NORTHWARD.

&&

.AVIATION/18Z TAFS/...

THUNDERSTORMS ASSOCIATED WITH AN UPPER LEVEL FRONT ARE MOVING NORTH
OF MADISON AND MILWAUKEE LATE THIS MORNING. GUSTY EAST WINDS FOR A
COUPLE OF HOURS ARE LIKELY IN THE WAKE OF THESE THUNDERSTORMS. THE
UPPER LEVEL FRONT WILL VERY SLOWLY MOVE NORTH THIS AFTERNOON...SO
SHOWERS AND ISOLATED THUNDER CAN BE EXPECTED IN FOND DU LAC AND
SHEBOYGAN AREAS PROBABLY THROUGH THE REST OF THE AFTERNOON. THIS
RAIN SHOULD MOVE NORTH WITH THE BOUNDARY INTO NORTHERN WI OVERNIGHT.

THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS DURING THE MID TO
LATE AFTERNOON AGAIN SOUTH AND WEST OF MADISON AS A SURFACE FRONT
APPROACHES. THIS WOULD END IN THE EVENING.

THERE IS A CHANCE THAT SCATTERED SHOWERS AND THUNDERSTORMS WILL
DEVELOP ONCE AGAIN SATURDAY AFTERNOON ALONG THE SURFACE BOUNDARY
WEST OF WAUKESHA...BUT AFFECTING MADISON AND JANESVILLE.

&&

.MARINE...

A FEW WIND GUSTS OF 20 TO 25 KNOTS WILL BE POSSIBLE THROUGH EARLY
AFTERNOON IN THE WAKE OF THUNDERSTORMS SLOWLY MOVING NORTH AND EAST
THROUGH THE AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 313 AM CDT FRI MAY 17 2013/

TODAY AND TONIGHT...FORECAST CONFIDENCE IS MEDIUM.

BAROCLINIC ZONE IS STRETCHED ACROSS THE AREA TODAY. COMBO OF WARM
ADVECTION/FRONTOGENESIS WITHIN THIS ZONE AND THE PASSAGE OF A WEAK
MID LEVEL SHORT WAVE WILL RESULT IN SHOWERS AND STORMS ACROSS THE
AREA TODAY. WE SHOULD HAVE TWO MAIN AREAS. THE FIRST...AND HIGHEST
PROBABILITY TODAY...WILL BE A ZONE OF WARM ADVECTION THAT SHOULD SET
UP MOSTLY NORTH OF MILWAUKEE AND MADISON THIS MORNING. THIS IS
STARTING TO TAKE SHAPE OVER NORTHEAST IOWA AND SOUTHERN MINNESOTA
EARLY THIS MORNING. THAT ACTIVITY WILL ROLL EAST NORTHEAST THIS
MORNING. ISENTROPIC CONDENSATION PRESSURE DEFICITS DEPICT THE AREA
OF SATURATION RATHER NICELY. MOST OF THE HIGHER RESOLUTION MODELS
ARE IN AGREEMENT WITH THE FOCUS ACROSS THAT AREA WITH THIS WAA
PRECIP. THAT PRECIP SHOULD LIFT NORTH OF THE FORECAST AREA BY EARLY
AFTERNOON. THE SECOND FOCUS FOR PRECIP WILL BE THIS AFTERNOON WITH
SCATTERED SHOWERS AND STORMS DURING THE HEAT OF THE DAY MAINLY
ACROSS THE SOUTHERN/SOUTHWEST CWA. THE HIGHEST SFC DEWPOINTS WILL BE
LOCATED IN THIS AREA WITH SOME CAPE SHOWING UP HERE AS WELL. THE
LOWEST CHANCE FOR PRECIP TODAY WILL BE THE FAR SOUTHEAST
CORNER...MAINLY FROM MILWAUKEE SOUTH TO THE STATE LINE. AS WE HEAD
INTO THE EVENING HOURS...DIURNAL TRENDS SHOULD MORE OR LESS END
EVERYTHING...SO WILL DIMINISH POPS QUICKLY.

EASTERLY WINDS TODAY WILL KEEP IT QUITE A BIT COOLER THAN PREVIOUS
DAYS ACROSS THE SOUTHEAST.  THE COOL TREND CONTINUES TONIGHT.

SATURDAY - CONFIDENCE...MEDIUM
LINGERING SURFACE/850 RIDGE STILL WITH SOME CONTROL ESPECIALLY ON
THE GFS AND ECMWF. THE NAM PULLS US MORE INTO THE SOUTHERLY FLOW
REGIME WITH SOME INSTAB SHRA DEVELOPING IN CENTRAL SECTIONS OF THE
CWA. THE NAM SOUNDINGS HAVE CAPE OVER 500 J/KG WHILE THE GFS PROFILE
IS MUCH MORE STABLE. WILL GO WITH DRY FORECAST GIVEN LACK OF QG
FORCING WITH THESE RIPPLES AND A RELATIVELY MORE STABLE INFLUENCE OF
THE SURFACE/850 RIDGE.

SUNDAY AND SUNDAY NIGHT - CONFIDENCE...MEDIUM
UPPER TROUGH IN THE PLAINS DRAWS CLOSER. ENERGY ROUNDING EASTERN
SIDE HAS GREATEST INFLUENCE TO OUR WEST AND SOUTH DURING THE DAY.
AGAIN...NAM MODEL IS THE ONLY ONE GENERATING PRECIP...WITH THE GFS
AND ECMWF SHOWING THE DRY LOOK. NEGATIVE TILT SHORTWAVE ENERGY
ARRIVES SUNDAY NIGHT AND THIS WILL BRING WITH IT A BETTER CHANCE OF
ORGANIZED CONVECTION...SO BOOSTED POPS ACCORDINGLY.

MONDAY - CONFIDENCE...MEDIUM
UPPER CIRCULATION CENTER VICINITY NW IA/SW MN. SW 500 MILLIBAR FLOW
ACROSS THE CWA. INCREASING WIND FIELDS NOTED AT 850 AND 250
MILLIBARS AS WELL. SEEING SOME POTENT PARAMETERS...SOME LIFTED
INDICES AS LOW AS -14. 0-1KM AND 0-6 KM SHEAR LOOKS DECENT. BUFKIT
SOUNDINGS SHOWING SOME WIDE/THICK CAPE WITH VALUES EXCEEDING 1500 J/KG.
GFS CWASP NUMBERS WELL INTO THE 80S...WITH ECMWF STILL SHOWING
HEFTY 70S. SO CLEARLY A DAY TO KEEP FOCUSING ON FOR SEVERE STORM
POTENTIAL.

TUESDAY AND WEDNESDAY - CONFIDENCE...MEDIUM
500 MILLIBAR LOW WILL BE SLOW TO MOVE EAST SO KEPT TSRA CHANCES
GOING. CWASP NUMBERS IN THE MID 60S TO LOW 70S TUESDAY...THEN DROP
OFF WEDNESDAY AS AIRMASS STABILIZES. 12Z ECMWF SHOWED THE SURFACE
LOW RIDING EAST ALONG A WARM FRONTAL BOUNDARY WITH ROUNDS OF QPF
WITH PERSISTENT VORT MAXES PIVOTING AROUND THE 500 LOW. 00Z ECMWF
QUICKER ON PLUNGING THE FRONT SOUTH OF WI TUE NGT...SO THUNDER
CHANCES MAY TRANSITION TO MORE OF A STABLE SHOWERY PATTERN IF THIS
QUICKER FROPA TAKES SHAPE.

THURSDAY - CONFIDENCE...MEDIUM
LOW LEVEL TROUGH STILL ENOUGH TO KEEP CHANCES FOR SHRA. 500 MILLIBAR
CLOSED LOW OPENS UP AND SHIFTS EAST. COLD ADVECTION MORE PRONOUNCED
VIA THE 12Z ECMWF WITH 0C 850 CONTOUR TOUCHING SHEBOYGAN BY DAYS
END. HOWEVER 00Z ECMWF RUN NOW LOOKS LIKE THE GFS SHOWING COLDEST
850 TEMPS AROUND 6C.

AVIATION/12Z TAFS/...VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD.
THUNDERSTORMS ARE LIKELY MAINLY NORTH OF MILWAUKEE AND MADISON
THIS MORNING...THOUGH IT WILL BE A CLOSE CALL AS TO WHETHER THEY
CLIP THESE TAF SITES. OTHERWISE...THERE IS A CHANCE OF SHOWERS AND
THUNDERSTORMS MAINLY DURING THE AFTERNOON...DIMINISHING OR ENDING
THIS EVENING.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&

$$

UPDATE...MRC
TODAY/TONIGHT AND AVIATION/MARINE...DAVIS
SATURDAY THROUGH THURSDAY...COLLAR