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000 

WWUS20 KWNS 091923

SEL8

SPC WW 091923

ILZ000-LMZ000-100100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 498

NWS STORM PREDICTION CENTER NORMAN OK

225 PM CDT MON JUL 9 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST ILLINOIS

       LAKE MICHIGAN



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 225 PM UNTIL 800

PM CDT.



HAIL TO 1.5 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 40

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 55 MILES NORTHEAST

OF MEIGS FIELD ILLINOIS TO 30 MILES SOUTH OF ROCKFORD ILLINOIS.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU8).



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 494...WW 495...WW

496...WW 497...



DISCUSSION...THUNDERSTORMS ALONG A COLD FRONT AND OUTFLOW BOUNDARY

WILL DEVELOP SEWD FROM WI INTO NE IL THIS AFTERNOON.  THE STORMS

WILL BE FED BY A VERY MOIST AND UNSTABLE AIR MASS...WHICH WILL

SUPPORT A THREAT FOR AT LEAST MARGINALLY SEVERE HAIL AND DAMAGING

DOWNBURSTS...DESPITE RATHER WEAK VERTICAL SHEAR.



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

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM

MOTION VECTOR 28020.





...THOMPSON

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