Severe Thunderstorm Warning 59, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
233 PM CDT WED AUG 22 2001

FORECAST CONCERNS FOCUS ON POPS EARLY PERIODS AS WELL AS THREAT OF
SEVERE WEATHER TONIGHT. WARM FRONT PUSHED INTO SOUTHERN WISCONSIN
AND IS NOW STATIONARY ALONG WI/IL BORDER SOUTHWEST INTO CENTRAL IA.
WINDS HAVE RECOVERED BACK TO S/SW WITH TEMPS INTO THE 80S AND
DEWPOINTS WELL INTO THE 70S. ONLY BOUNDARY DETECTED LIES ACROSS
SOUTHERN FA BUT OTHERS LIKELY ABOUT AFTER MORNING CONVECTION.

DIFFERENCES SHOWING UP IN THE MODELS THIS RUN. AT 18Z...AVN SEEMS TO
HAVE BEST HANDLE ON SURFACE WINDS/LOCATION OF FRONT AS WELL AS
POSITION OF LOW ACROSS NE IA. AVN ALSO DID A BETTER JOB WITH
LOCATION OF CONVECTION THIS MORNING OVER SOUTHERN WI AND SOUTHWEST
MI. BY 00Z ETA LOOKS TOO FAR SOUTH WITH FRONT AND QPF. AVN FARTHER
NORTH AND LOOKS OVERALL BETTER WITH INSTABILITY. WILL TREND TOWARD
THE AVN AND NOW WITH SVR WX BOX OUT WILL GO CAT ENTIRE FA. WILL END
POPS LATE TONIGHT NORTHERN AREA AND CONTINUE POPS ALL NIGHT WITH
HEAVY RAIN MENTIONED ACROSS SOUTHERN FA. WILL ALSO KEEP LOW CHANCE
POP FOR ANY LEFT OVER RAIN SOUTHERN FA.

HIGH PRESSURE BUILDS IN ON THURS FROM UPPER LAKES AND WILL DRY
THINGS OUT UNTIL SAT WHEN NEXT SYSTEM APPROACHES. WILL REMOVE POPS
FROM FRI...KEEP FOR SAT AND INTRODUCE ON SUN. WILL STAY CLOSE TO
GUIDANCE EARLY PERIODS AND TREND WARMER TOWARD MAV LATER PERIODS.

.CHI...NONE.

CMS

ILZ003>006-008-010>014-019>023-032>033-039-INZ001>002-010>011-019-
231100-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO IL
1200 PM CDT/EST WED AUG 22 2001

FOR NORTH CENTRAL AND NORTHEAST ILLINOIS AND NORTHWEST INDIANA...

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

LOW PRESSURE WAS OVER NORTHERN IOWA LATE THIS MORNING...WITH A
STATIONARY FRONT EXTENDING ACROSS FAR NORTHERN ILLINOIS.
THUNDERSTORMS THAT DEVELOPED ALONG THIS FRONT THIS MORNING HAVE
DISSIPATED. OUTFLOW BOUNDARIES FROM THESE THUNDERSTORMS HAVE PUSHED
SOUTH ACROSS NORTHERN AND CENTRAL ILLINOIS.

THIS STATIONARY FRONT WILL SLOWLY MOVE SOUTH AS A WEAK COLD FRONT
LATER THIS AFTERNOON AND THIS EVENING. THUNDERSTORMS ARE EXPECTED TO
REDEVELOP THIS AFTERNOON AHEAD OF THIS FRONT...ACROSS NORTHERN
ILLINOIS...AND MOVE SOUTHEAST INTO CENTRAL ILLINOIS AND NORTHWEST
INDIANA THIS EVENING. THE MAIN SEVERE WEATHER THREAT FROM THESE
THUNDERSTORMS WILL BE DAMAGING WINDS ALONG WITH HEAVY RAINFALL.

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND THIS EVENING.

STAY TUNED TO NOAA WEATHER RADIO...OR OTHER MEDIA OUTLETS...FOR
LATER STATEMENTS FROM THE NATIONAL WEATHER SERVICE.

CMS