MESOSCALE DISCUSSION 0877
   NWS STORM PREDICTION CENTER NORMAN OK
   0935 PM CDT SUN MAY 22 2011
   
   AREAS AFFECTED...EXTREME SERN WI THROUGH NRN IL
   
   CONCERNING...TORNADO WATCH 327...
   
   VALID 230235Z - 230330Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 327 CONTINUES.
   
   SEVERE THREAT MAY PERSIST A COUPLE HOURS BEYOND WW 327 EXPIRATION
   TIME OF 03Z ACROSS NRN IL INTO EXTREME SERN WI. PRIMARY THREAT HAS
   TRANSITIONED TO DAMAGING WIND AND HAIL...BUT AN ISOLATED TORNADO OR
   TWO CANNOT BE RULED OUT. PER COORDINATION WITH WFO CHICAGO...WW 327
   WILL BE LOCALLY EXTENDED FOR NRN IL UNTIL AROUND 05Z.
   
   CONVECTIVE OUTFLOW MERGING WITH PACIFIC FRONT HAS RESULTED IN RAPID
   UPSCALE LINEAR GROWTH FROM EXTREME SERN WI SWWD THROUGH NWRN IL.
   PREVIOUS AND ONGOING CONVECTION AND ONSET OF NOCTURNAL COOLING HAVE
   STABILIZED THE BOUNDARY LAYER EAST OF SQUALL LINE AND SHOULD POSE A
   LIMITING FACTOR FOR A MORE ROBUST SEVERE/TORNADO THREAT.
   NEVERTHELESS...VERTICAL SHEAR AND LOW LEVEL HODOGRAPHS REMAIN
   FAVORABLE FOR EMBEDDED ORGANIZED STORM STRUCTURES INCLUDING
   SUPERCELLS AND BOWING SEGMENTS AS ACTIVITY CONTINUES EWD NEXT COUPLE
   HOURS.
   
   ..DIAL.. 05/23/2011
   
   
   ATTN...WFO...LOT...ILX...MKX...DVN...
   
   LAT...LON   42818815 41998781 41428726 40678775 40948891 41678958
               42818815