MESOSCALE DISCUSSION 1868
   NWS STORM PREDICTION CENTER NORMAN OK
   0129 PM CDT THU JUL 17 2003
   
   AREAS AFFECTED...SRN WI...NRN IL...EXTREME NERN IA
   
   CONCERNING...SEVERE THUNDERSTORM POTENTIAL 
   
   VALID 171829Z - 172000Z
   
   ...SEVERE THUNDERSTORMS SHOULD DEVELOP THIS AFTERNOON ACROSS THE
   REGION...WW MAY BE REQUIRED IN THE NEXT FEW HOURS...
   
   STRONG BOUNDARY LAYER HEATING ACROSS IA...SRN WI AND NRN IL HAS
   ALLOWED INHIBITION TO GRADUALLY WEAKEN...ESPECIALLY FROM SERN WI
   INTO EXTREME NRN IL.  RECENT CU FIELD EXPANSION SUPPORTS CONTINUED
   DESTABILIZATION ACROSS WARM SECTOR...AHEAD OF SWD-MOVING COLD FRONT.
    
   
   ALTHOUGH ISOLATED ELEVATED THUNDERSTORMS HAVE AT TIMES FLARED UP
   ACROSS CENTRAL IL...AND ALONG/BEHIND IMMEDIATE WIND SHIFT FROM NEAR
   GRB...EWD INTO LOWER MI...IT APPEARS MORE ROBUST CONVECTION WILL
   INITIATE IN THE NEXT FEW HOURS OVER SRN WI.  VERTICAL SHEAR PROFILES
   INDICATE ROTATION IS LIKELY AND SUPERCELLS MAY BE THE EARLY DOMINANT
   MODE.  WITH TIME...STORM MERGERS AND CLUSTERING SHOULD OCCUR AS
   ACTIVITY DROPS SWD INTO IL.  WWD EXTENT INTO IA WILL OCCUR LATE THIS
   AFTERNOON OR EVENING...ALTHOUGH CONVECTION WILL BE FIGHTING A STRONG
   CAP.
   
   ..DARROW.. 07/17/2003
   
   
   ATTN...WFO...GRB...LOT...MKX...DVN...ARX...
   
   44199018 43258740 41658746 42109066 43089169