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WWUS20 KWNS 190041

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ILZ000-INZ000-WIZ000-LMZ000-190600-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 494

NWS STORM PREDICTION CENTER NORMAN OK

745 PM CDT WED JUL 18 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST ILLINOIS

       EXTREME NORTHWEST INDIANA

       EXTREME SOUTHEAST WISCONSIN

       LAKE MICHIGAN



EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 745 PM

UNTIL 100 AM 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 55

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

JANESVILLE WISCONSIN TO 25 MILES NORTH OF VALPARAISO INDIANA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU4).



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 493. WATCH NUMBER 493 WILL NOT

BE IN EFFECT AFTER 745 PM CDT. CONTINUE...WW 490...WW 491...WW

492...



DISCUSSION...MCS OVER SE WI/NRN IL SHOULD CONTINUE TO TRACK

ESEWD/SEWD ALONG THE IMMEDIATE COOL SIDE OF A LAKE-ENHANCED FRONT.

MODERATE INSTABILITY ALONG THE BOUNDARY AND SOMEWHAT STRONGER

VERTICAL SHEAR ON THE COOL SIDE WILL HELP MAINTAIN AN ORGANIZED

CLUSTER OF STORMS FOR A FEW MORE HOURS...WITH AN ATTENDANT RISK FOR

AT LEAST ISOLATED DAMAGING WINDS/LARGE HAIL.



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 30025.





...THOMPSON

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