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WWUS20 KWNS 280043

SEL4

SPC WW 280043

IAZ000-ILZ000-INZ000-WIZ000-LMZ000-280600-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 694

NWS STORM PREDICTION CENTER NORMAN OK

745 PM CDT WED JUL 27 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       EAST CENTRAL IOWA

       NORTHERN ILLINOIS

       EXTREME NORTHWEST INDIANA

       EXTREME SOUTHERN WISCONSIN

       LAKE MICHIGAN



EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 745 PM

UNTIL 100 AM CDT.



TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 35 STATUTE

MILES NORTH AND SOUTH OF A LINE FROM 40 MILES WEST SOUTHWEST OF

DUBUQUE IOWA TO 30 MILES EAST NORTHEAST OF MEIGS FIELD ILLINOIS.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU4).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.



DISCUSSION...CLUSTER OF STORMS...SOME WITH EMBEDDED SUPERCELL

STRUCTURES...WILL CONTINUE TO EXPAND ALONG THE SURFACE WARM FRONT

NEAR THE IL/WI BORDER.  STRONG INSTABILITY AND VEERING LOW-LEVEL

SHEAR PROFILES WILL SUPPORT STORM-SCALE ROTATION WITH DEVELOPING

STORMS ON THE BOUNDARY...WITH THE POSSIBILITY OF LARGE HAIL AND A

TORNADO OR TWO IN THE NEXT COUPLE OF HOURS.  UPSCALE GROWTH OF THE

CONVECTION WILL RESULT IN STRONGER COLD POOL GENERATION AND AN

ATTENDANT RISK FOR DAMAGING WINDS.



AVIATION...TORNADOES AND 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

650. MEAN STORM MOTION VECTOR 28020.





...THOMPSON

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