Hail in Wisconsin, August 21, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
340 PM CDT WED AUG 21 2013

.VERY SHORT TERM...TONIGHT AND THURSDAY.

CONVECTION IS FIRING UP ALONG THE SURFACE COLD FRONT FROM NORTHWEST
WI THROUGH THE TWIN CITIES AREA. THIS LINES UP WELL WITH THE NCEP
4KM WRF-NMM SIMULATED RADAR REFLECTIVITY. THAT MODEL BRINGS A LINE
OF CONVECTION SOUTHEAST INTO THE MKX FORECAST AREA 01Z-02Z...THEN
ALLOWS IT TO WEAKEN. IT SHOWS A SLIGHTLY STRONGER AREA OF CONVECTION
CONTINUING IN SOUTHEAST WI BUT MUCH LESS CONVECTION IN SOUTH CENTRAL
WI. SOME OF THE OTHER MODELS ARE SHOWING THIS SPLIT AS WELL..SO IT
WILL BE SOMETHING TO WATCH OUT FOR. MEANWHILE...THE 18Z HRRR MODEL
RUN SHOWS THAT CONVECTION IN NORTHWEST WI...BRINGS IT EASTWARD AS A
BLOB...AND NEVER EXTENDS ANY CONVECTION DOWN INTO SOUTHERN WI AT
ALL.

MOST CONVECTION WILL LIKELY BE ALONG THE IL BORDER BY 06Z AND ENDING
SHORTLY THEREAFTER. MID LEVEL DRY AIR MOVES IN QUICKLY BEHIND THE
FRONT AND ANY SEVERE THREAT WILL BE GONE BY 06Z.

AS FOR SEVERE POTENTIAL...THE BEST RISK OF SEVERE WEATHER WILL BE
OVER NORTH CENTRAL WI. THIS IS WHERE THE SPC STORM SCALE ENSEMBLE OF
OPPORTUNITY BULLSEYES THE HIGHEST 24-HOUR PROBABILITY OF HIGH
UPDRAFT HELICITY AND HIGH UPDRAFT SPEED. THIS IS ALSO WHERE THERE IS
A SEVERE THUNDERSTORM WATCH IN EFFECT RIGHT NOW.

SPC HAS THE SLIGHT RISK INCLUDING MADISON AND WEST BEND. THIS SEEMS
REASONABLE BASED ON MODEL FORECAST REFLECTIVITIES. ANY STRONGER AND
ORGANIZED STORMS THAT DEVELOP OVER CENTRAL WI COULD SWEEP SOUTH AND
SOUTHEAST WITH A DAMAGING STRAIGHT-LINE WIND THREAT INTO THE
NORTHERN MKX FORECAST AREA. WITH CAPE VALUES EXCEEDING 3000 J/KG AND
MODERATE 0-3 AND 0-6KM SHEAR...LARGE HAIL WILL BE POSSIBLE AS WELL.

AS STORMS MAKE IT FURTHER INTO SOUTH CENTRAL AND SOUTHEAST WI LATER
THIS EVENING...SURFACE BASED CAPE AND BULK SHEAR VALUES DECREASE
GIVEN THE TIME OF DAY AND THE SURFACE TROUGH LOSING DEFINITION. ALSO
THE 850MB LEADING EDGE OF THE LOW LEVEL JET AND WARM AIR ADVECTION
WILL BE SHIFTING EAST OVER LAKE MICHIGAN.

THERE IS ANOTHER SHORTWAVE THAT WILL TRACK ALONG THE 850MB
BAROCLINIC ZONE THROUGH NORTHERN IOWA AND EVENTUALLY INTO NORTHERN
IL LATE TONIGHT/THU MORNING. CONVECTION WITH THIS FEATURE MAY CLIP
SOUTHERN WI SO LEFT A SMALL CHANCE FOR THUNDER THROUGH THU MORNING.

SUNSHINE IS EXPECTED LATER THURSDAY...ALLOWING MAX TEMPS IN THE
UPPER 70S AND LOWER 80S WITH A NORTH TO NORTHEAST BREEZE.

.SHORT TERM...THURSDAY NIGHT THROUGH SATURDAY.

A QUIET PERIOD IS ANTICIPATED AS HIGH PRESSURE AT THE SURFACE AND
ALOFT CONTINUES TO BUILD INTO THE WESTERN GREAT LAKES TO CENTRAL MS
VALLEY.  LIGHT WINDS BELOW SHALLOW INVERSION SHOULD ALLOW PATCHY FOG
TO DEVELOP IN THE WI RIVER VLY LATER THU NIGHT.  BOUNDARY LAYER
MIXING JUST ABOVE INVERSION SHOULD PREVENT SIGNIFICANT FOG ELSEWHERE
HOWEVER. WARMER AIR STARTS TO RETURN ON SATURDAY AS LOW LEVEL WINDS
TURN MORE SOUTH.  ANY CONVECTION ASSOCIATED WITH PUSH OF WARM AIR
AND WEAK SHORT WAVE IS EXPECTED TO REMAIN TO THE NORTH OF CWA ON
SAT.

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY.

MEDIUM RANGE GUIDANCE IN GOOD AGREEMENT ON EXPANSIVE HIGH PRESSURE
RIDGE OVER SOUTHERN CONUS EXPANDING NORTHWARD AND ENVELOPING
SOUTHERN WI ON SATURDAY AND PERSISTING THROUGH THE FIRST PORTION OF
NEXT WEEK.  500H HEIGHTS INCREASE TO AROUND 591 METERS WHILE 85H
TEMPS INCREASE TO 19 TO 22C.  HENCE A VERY WARM PERIOD IS EXPECTED
WITH DAYTIME READINGS MOSTLY IN THE UPPER 80S TO MIDDLE 90S.
DAYTIME HEAT INDICIES MAY REACH 95 TO 100 SEVERAL DAYS.

500H GFS 5 DAY ANOMOLIES SHOW HEIGHTS 50-70 METERS ABOVE NORMAL
THROUGH THE END OF AUGUST...WITH MORE ZONAL FLOW SETTLING OVER
NORTHERN CONUS FOR START OF SEPT.

STILL A POTENTIAL FOR SEVERAL MID-LEVEL SHORT WAVES BREAKING THROUGH
CAPPING INVERSION OVER NORTHERN/CENTRAL WI...WITH CONVECTION
CARRYING SWD INTO PORTIONS OF SRN WI FROM SAT NIGHT INTO TUE.  MOST
OF THE PERIOD WILL REMAIN DRY AND WARM HOWEVER.

&&

.AVIATION /00Z TAFS/...THUNDERSTORMS ARE LIKELY ALONG A COLD FRONT
MOVING SOUTHEAST ACROSS CENTRAL AND SOUTHERN WI THIS EVENING. SOME
IFR CONDITIONS IN STORMS. STORMS WILL BE MORE WIDESPREAD EARLY THIS
EVENING AND THEN BECOME MORE SCATTERED LATER IN THE EVENING. SEVERE
THUNDERSTORMS POSSIBLE NORTH OF A LINE FROM PLATTEVILLE TO MADISON
TO WEST BEND. DAMAGING WINDS AND SMALL HAIL ARE THE THREATS. SEVERE
POTENTIAL DIMINISHES AFTER 06Z AND PRECIP CHANCES DIMINISH SHORTLY
THEREAFTER AS WELL.

THERE COULD BE A PERIOD OF MVFR CIGS AND VSBYS JUST BEHIND FRONT
OVERNIGHT. DRIER AIR WITH WINDS OUT OF THE NORTHEAST WILL SETTLE
INTO SOUTHERN WI BY EARLY THU AFTERNOON.

&&

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

&&

.CONFIDENCE...
TONIGHT AND THURSDAY...MEDIUM TO HIGH.
THURSDAY NIGHT THROUGH SATURDAY...HIGH.
SATURDAY NIGHT THROUGH WEDNESDAY...MEDIUM.

VERY SHORT TERM/AVIATION...MRC
SHORT TERM/LONG TERM...MBK

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
630 PM CDT WED AUG 21 2013

WIZ046-047-051-052-056>060-062>072-222330-
MARQUETTE-GREEN LAKE-FOND DU LAC-SHEBOYGAN-SAUK-COLUMBIA-DODGE-
WASHINGTON-OZAUKEE-IOWA-DANE-JEFFERSON-WAUKESHA-MILWAUKEE-
LAFAYETTE-GREEN-ROCK-WALWORTH-RACINE-KENOSHA-
630 PM CDT WED AUG 21 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL
WISCONSIN...SOUTH CENTRAL WISCONSIN AND SOUTHEAST WISCONSIN.

.DAY ONE...TONIGHT

A COLD FRONT WILL SAG THROUGH SOUTHERN WISCONSIN FROM LATE
EVENING THROUGH THE OVERNIGHT HOURS. SCATTERED TO NUMEROUS
THUNDERSTORMS ARE EXPECTED ALONG THE FRONT. THERE IS A SLIGHT RISK
OF SEVERE THUNDERSTORMS ROUGHLY ALONG AND NORTH OF A LINE
EXTENDING FROM SHEBOYGAN...WEST BEND...MADISON TO DODGEVILLE.
DAMAGING WINDS WILL BE THE PRIMARY HAZARD.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH WEDNESDAY

THERE IS A SMALL CHANCE OF THUNDERSTORMS THURSDAY MORNING ALONG
AND SOUTH OF A LINE FROM MILWAUKEE TO MINERAL POINT.

HEAT INDEX READINGS ARE EXPECTED TO REACH THE 90 TO 100 DEGREE RANGE
DURING THE DAYS FROM SUNDAY THROUGH TUESDAY.

THERE IS A SMALL CHANCE FOR THUNDERSTORMS FROM SUNDAY NIGHT
THROUGH TUESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TONIGHT.

LMZ643>646-222330-
SHEBOYGAN TO PORT WASHINGTON WI-
PORT WASHINGTON TO NORTH POINT LIGHT WI-
NORTH POINT LIGHT TO WIND POINT WI-
WIND POINT WI TO WINTHROP HARBOR IL-
630 PM CDT WED AUG 21 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE MICHIGAN.

.DAY ONE...TONIGHT

WINDS AND WAVES WILL CONTINUE TO APPROACH SMALL CRAFT CRITERIA
LATE THIS AFTERNOON.

THUNDERSTORMS ARE LIKELY TONIGHT AS A COLD FRONT DROPS SOUTHEAST
ACROSS LAKE MICHIGAN. THERE IS A SLIGHT RISK OF SEVERE
THUNDERSTORMS NORTH OF NORTH POINT LIGHT.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH WEDNESDAY

THERE IS A CHANCE OF THUNDERSTORMS THURSDAY MORNING FROM MILWAUKEE
SOUTH TO WINTHROP HARBOR.

THERE IS A SMALL CHANCE FOR THUNDERSTORMS FROM SUNDAY NIGHT
THROUGH TUESDAY.

REM
WWW.WEATHER.GOV/MKX