MESOSCALE DISCUSSION 1582
   NWS STORM PREDICTION CENTER NORMAN OK
   0316 AM CDT THU JUL 26 2007
   
   AREAS AFFECTED...NE IL/NW IN
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 260816Z - 260945Z
   
   LATEST RUC GUIDANCE INDICATES GENERALLY WEAK INSTABILITY.  BUT...
   CONVECTIVE ACTIVITY HAS INTENSIFIED DURING THE PAST FEW HOURS OVER
   SOUTHERN LAKE MICHIGAN...WHERE WARMER LAKE WATER TEMPERATURES MAY BE
   SUPPORTING A BIT GREATER INSTABILITY THAN CURRENTLY PROGGED.  THIS
   DEVELOPMENT APPEARS TO BE STRONGLY FORCED BY A MID-LEVEL
   IMPULSE...WHICH IS IN THE PROCESS OF MIGRATING AROUND THE
   SOUTHWESTERN PERIPHERY OF THE CUT-OFF LOW.  PAST SEVERAL RUNS OF THE
   RUC HAVE INDICATED THAT THIS BELT OF UPWARD VERTICAL MOTION WILL
   FINALLY SHIFT TO THE SOUTH/WEST OF LOWER LAKE MICHIGAN BY THE 
   10-11Z TIME FRAME.  AND...MID-LEVEL SUBSIDENCE IN ITS WAKE SHOULD
   CONTRIBUTE TO DIMINISHING THUNDERSTORM ACTIVITY.  UNTIL THIS
   OCCURS...THUNDERSTORMS WILL CONTINUE TO AFFECT COASTAL AND
   SOUTHEASTERN PORTIONS OF THE GREATER CHICAGO AREA...PERHAPS WITH
   GUSTY WINDS...MAINLY WITH LOCALLY HEAVY DOWN POURS AND CLOUD TO
   GROUND LIGHTNING STRIKES.
   
   ..KERR.. 07/26/2007
   
   
   ATTN...WFO...IWX...LOT...
   
   42498717 42128694 41298682 41188730 41448764 41808773
   42078774 42438758