

704 

WWUS20 KWNS 250400

SEL1

SPC WW 250400

ILZ000-INZ000-250800-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 621

NWS STORM PREDICTION CENTER NORMAN OK

1100 PM CDT FRI JUL 24 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EAST CENTRAL AND NORTHEAST ILLINOIS

       EXTREME NORTHWEST INDIANA



EFFECTIVE THIS FRIDAY NIGHT AND SATURDAY MORNING FROM 1100 PM

UNTIL 300 AM CDT.



HAIL TO 1 INCH 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 55

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 15 MILES WEST

SOUTHWEST OF BLOOMINGTON ILLINOIS TO 45 MILES NORTHEAST OF

DANVILLE ILLINOIS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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 620...



DISCUSSION...WELL-DEVELOPED BOW ECHO HAS ACCELERATED TOWARD THE SE

AT 45-50 KT ACROSS IL...AND WILL LIKELY MOVE INTO THE WATCH AREA

WITHIN THE NEXT 30-60 MINUTES.  THOUGH INSTABILITY WEAKENS WITH

EWD/SEWD EXTENT...THE ORGANIZED STORM STRUCTURE SUGGESTS THAT SOME

WIND DAMAGE THREAT WILL PERSIST FOR AT LEAST ANOTHER 2-3 HOURS AND

POTENTIALLY SPREAD INTO INDIANA.



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

TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS.

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

VECTOR 31045.





...THOMPSON

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