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WWUS20 KWNS 180424

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SPC WW 180424

ILZ000-WIZ000-180800-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 340

NWS STORM PREDICTION CENTER NORMAN OK

1125 PM CDT THU JUN 17 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EXTREME NORTHERN ILLINOIS

       SOUTHERN WISCONSIN



EFFECTIVE THIS THURSDAY NIGHT AND FRIDAY MORNING FROM 1125 PM

UNTIL 300 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 60

STATUTE MILES EAST AND WEST OF A LINE FROM 55 MILES NORTH OF

MADISON WISCONSIN TO 35 MILES WEST OF ROCKFORD ILLINOIS.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU0).



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 336...WW 337...WW

338...WW 339...



DISCUSSION...QUASI-LINEAR MCS WITH TWO WELL ORGANIZED BOWING

SEGMENTS OF DEEP CONVECTION EXPECTED TO CONTINUE EAST ACROSS SRN WI

THROUGH EARLY MORNING HOURS FRIDAY. LATEST SYSTEM MOTION WAS OVER

40KT AND THIS SHOULD BRING THE STORMS TO WRN SHORE OF LAKE MI BEFORE

3 AM CDT.

WHILE AIRMASS OVER THE WATCH AREA IS NOT PARTICULARLY UNSTABLE AND

THIS MAY TEND TO INHIBIT STRONGER CONVECTIVE OVERTURNING AND SEVERE

WIND GUSTS WITH TIME...RADAR APPEARANCE AND LARGE SCALE FORCING AND

SHEAR SUGGEST THAT THE WIND DAMAGE THREAT REMAINS NON-NEGLIGIBLE AND

SHOULD CONTINUE AT LEAST INTO PARTS OF SOUTH-CENTRAL WI AND EXTREME

NRN IL NEXT FEW HOURS.



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 450. MEAN STORM

MOTION VECTOR 26040.





...CARBIN

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