July 27: Tornado Watch #694 (N. IL, E. IA) (Until 1 AM CDT)

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.