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WWUS20 KWNS 032341

SEL3

SPC WW 032341

ILZ000-INZ000-LMZ000-040500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 233

NWS STORM PREDICTION CENTER NORMAN OK

645 PM CDT THU MAY 3 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST ILLINOIS

       EXTREME NORTHWEST INDIANA

       LAKE MICHIGAN



EFFECTIVE THIS THURSDAY NIGHT FROM 645 PM UNTIL MIDNIGHT CDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 50

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 25 MILES NORTHWEST

OF MARSEILLES ILLINOIS TO 10 MILES NORTH OF VALPARAISO INDIANA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU3).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



OTHER WATCH INFORMATION...THIS SEVERE THUNDERSTORM WATCH REPLACES

SEVERE THUNDERSTORM WATCH NUMBER 230. WATCH NUMBER 230 WILL NOT

BE IN EFFECT AFTER 645 PM CDT. CONTINUE...WW 231...WW 232...



DISCUSSION...RENEWED THUNDERSTORM DEVELOPMENT IS UNDERWAY ALONG A

CONFLUENCE BAND ACROSS NE IL...WITH THE CONVECTION BEING FED BY 30

KT SWLY LOW-LEVEL FLOW AND RICHER MOISTURE/INSTABILITY ACROSS

CENTRAL IL.  THE COMBINATION OF MODERATE INSTABILITY AND EFFECTIVE

BULK SHEAR OF 30-40 KT WILL SUPPORT ORGANIZED CLUSTERS AND SUPERCELL

STRUCTURES...WITH A PRIMARY RISK OF LARGE HAIL AND DAMAGING WINDS

THROUGH EARLY TONIGHT.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 26025.





...THOMPSON

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