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470 

WWUS20 KWNS 242313

SEL3

SPC WW 242313

ILZ000-INZ000-MIZ000-MOZ000-OHZ000-250700-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 803

NWS STORM PREDICTION CENTER NORMAN OK

605 PM CDT WED AUG 24 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WEST CENTRAL THROUGH MUCH OF EASTERN ILLINOIS

       WESTERN AND NORTHERN INDIANA

       FAR SOUTHERN LOWER MICHIGAN

       EAST CENTRAL MISSOURI

       NORTHWEST OHIO



EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 605 PM

UNTIL 200 AM 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 115

STATUTE MILES EAST AND WEST OF A LINE FROM 70 MILES EAST

NORTHEAST OF SOUTH BEND INDIANA TO 30 MILES SOUTHEAST OF ALTON

ILLINOIS.  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...CONTINUE...WW 802...



DISCUSSION...TSTMS EXPECTED TO INCREASE IN COVERAGE / STRENGTH OVER

WW AREA OVER THE NEXT FEW HOURS AS LARGE SCALE ASCENT INCREASES

ALONG AND AHEAD OF COLD FRONT ASSOCIATED WITH AMPLIFYING SHORTWAVE

TROUGH NOW OVER WI.  CINH WILL INCREASE FOR NEAR-SFC PARCELS WITH

SUNDOWN.  BUT COMBINATION OF STRONG INSTABILITY ABOVE THE BOUNDARY

LAYER...MODEST LOW LVL CONVERGENCE / LARGELY LINEAR LOW LVL FORCING

ALONG/AHEAD OF FRONT...AND SEASONABLY STRONG WIND FIELD /ESPECIALLY

IN NRN HALF OF WW/ SUGGESTS POTENTIAL FOR A FEW SUPERCELLS/SUSTAINED

MULTICELL CLUSTERS WITH SVR WIND/HAIL.  THESE MAY EVOLVE INTO ONE OR

TWO LARGER MCSS WITH EMBEDDED BOWING SEGMENTS LATER THIS EVE/EARLY

THU.



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 550. MEAN STORM

MOTION VECTOR 31525.





...CORFIDI

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