Severe Thunderstorm Warning 62, NWS Green Bay, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
359 AM CDT THU SEP 18 1997

MAIN FCST CONCERN IS TSTM CHCS FOR THIS EVG AND TONIGHT...AND ASSOCIATED
RISK OF SVR WX. THIRD PERIOD OF FCST ALSO HOLDS SOME CHALLENGES.

NOT TOO SURE WHETHER TSRA WILL MAKE IT INTO NC/C WI THIS AFTERNOON.
FRONT IS ONLY FCST TO BE IN FAR NW WI BY 00Z AND WEAK CAPPING NOTED AT
850 MB ON FCST SOUNDINGS PRIOR TO ARRIVAL OF FRONT. DONT DESIRE TO
REMOVE FIRST PERIOD TSTM CHC FOR NC/C WI...BUT PREFER TOWARDS EVENING
WORDING. SVR THREAT APPEARS VERY REAL FOR THIS EVG...ESP WSTRN PART OF
MY CWA. FAVORABLE SHEAR...VERY STG MID-LEVEL FLOW AROUND 50 KTS...
STRENTHENING SFC CONVG/UPPER DIVG AND INCREASING LOW-LEVEL MOISTURE ALL
VALIDATE SPC SLGT RISK. ONLY CONCERN IS HOW FAR EAST THE
STG CONVECTION WILL MAKE IT BEFORE THE INSTABILITY WANES. ETA MODEL
CAPES DECREASE RAPIDLY BY 06Z/FRI. CURRENT FEELING IS THAT LINE OF SVR
STORMS WITH DAMAGING WINDS WILL MOVE INTO WSTRN PART OF CWA BY EARLY
EVG...THEN GRADUALLY WEAKEN AS THEY MOVE EAST. WELL SEE...

OTHER FIRST PERIOD CONCERNS ARE WINDS AND TEMPS. SFC-H8 GRADIENT
INCREASES SIGNIFICANTLY TODAY...WITH H8 WINDS INCREASING TO 40-45 KTS.
DEVELOPING CAP AT 850 MB WILL KEEP THESE VERY STG WINDS FROM MIXING
DOWN...BUT FEEL THAT GUSTS TO 30 MPH ARE LIKELY. STG SW FLOW WILL
PULL WARMER AIR INTO FA TODAY...H8 TEMPS/THICKNESS CHANGES INDICATE 5-7
DEGREES WARMER THAN YDAY. NGM MOS SEEMS IN THE BALLPARK.

NGM MOS POPS LOOK TOO LOW FOR FRIDAY...AND PREFER COOLER AND WETTER LOOK
OF FAN GUIDANCE THEN. FRONTOGENETIC NATURE OF SYSTEM...TIGHT 850 MB
BAROCLINIC ZONE AND LOCATION OF RRQ OF UPPER JET APPEAR FAVORABLE FOR
WIDESPREAD SHOWER ACTIVITY. CURRENT FCST HAS THIS WELL HANDLED.

KIECKBUSCH

WIZ005-010>013-018>022-030-031-035>040-045-048>050-181700-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREEN BAY WI
12 NOON CDT THU SEP 18 1997

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND PARTS OF CENTRAL
AND NORTH-CENTRAL WISCONSIN.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE ENTIRE
FORECAST AREA TONIGHT.

FORECAST:
A LINE OF STRONG THUNDERSTORMS IS EXPECTED TO DEVELOP ALONG A STRONG
COLD FRONT ACROSS EASTERN MINNESOTA LATE THIS AFTERNOON. SOME OF THESE
STORMS COULD BECOME SEVERE...WITH WIND GUSTS IN EXCESS OF 60 MPH AS THEY
MOVE RAPIDLY EASTWARD INTO NORTHWEST WISCONSIN DURING THE EARLY EVENING.
THE STORMS SHOULD MOVE INTO THE NORTHWEST PORTION OF THE FORECAST
AREA BY 8 OR 9 PM...THEN SPREAD EASTWARD...REACHING EASTERN SECTIONS
AROUND MIDNIGHT.

DISCUSSION:
STRONG SOUTHWEST WINDS WILL CONTINUE TO PULL MOIST AND UNSTABLE AIR INTO
THE REGION THIS AFTERNOON. A STRONG COLD FRONT WILL MOVE INTO NORTHWEST
WISCONSIN BY EARLY EVENING...TRIGGERING A LINE OF STRONG TO SEVERE
THUNDERSTORMS OUT AHEAD OF IT. FAVORABLE WIND SHEAR AND STRONG WINDS
IN THE MID-LEVELS OF THE ATMOSPHERE WILL BE CONDUCIVE TO THE DEVELOPMENT
OF DAMAGING WINDS WITH THESE STORMS.

SPOTTER ACTION:
SPOTTER ACTIVATION MAY BE NECESSARY EARLY TONIGHT...ESPECIALLY IN NORTH
CENTRAL AND CENTRAL WISCONSIN COUNTIES.

ADDITIONAL INFORMATION WILL BE AVAILABLE IN THE SHORT-TERM FORECAST.

EB