MESOSCALE DISCUSSION 1675
   NWS STORM PREDICTION CENTER NORMAN OK
   1249 PM CDT THU JUL 21 2011
   
   AREAS AFFECTED...IL...WI
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 211749Z - 211845Z
   
   FOR THE SHORT-TERM...A WATCH DOES NOT APPEAR LIKELY AHEAD OF WEAK
   COLD FRONT/OUTFLOW MOVING ACROSS NERN IL AND THE SRN END OF LM.
   HOWEVER...ISOLATED TSTM DEVELOPMENT TRENDS OVER THE AREA WILL
   CONTINUE TO BE MONITORED.
   
   EXTREME INSTABILITY HAS DEVELOPED IN A HOT AND VERY MOIST AIRMASS
   ACROSS NRN IL...SERN WI...AND THE SRN END OF LM. A PERSISTENT BUT
   WEAKLY ORGANIZED TSTM WAS MOVING EAST ALONG/AHEAD OF
   OUTFLOW-REINFORCED COLD FRONT OVER MCHENRY COUNTY ATTM. DESPITE
   MAGNITUDE OF INSTABILITY /MLCAPE 4000-5000 J PER KG/...ADDITIONAL
   DEVELOPMENT NEAR THE FRONT/OUTFLOW IS UNCERTAIN DUE TO WEAK LARGE
   SCALE SUPPORT FOR ASCENT AND LIMITED LOW LEVEL CONVERGENCE ALONG THE
   FRONT. VERY WARM MID-LEVEL TEMPS MAY ALSO BE CONTRIBUTING TO A LARGE
   DEGREE OF CONVECTIVE INHIBITION ACROSS THE REGION.
   
   DESPITE THESE LIMITATIONS...EVEN ISOLATED CONVECTION DEVELOPING
   ACROSS THE REGION THIS AFTERNOON WILL COME WITH THE THREAT OF
   DAMAGING DOWNBURST WINDS DUE TO EXTREME THERMODYNAMIC REGIME. LATEST
   ANALYSIS OF SHORT-TERM MODEL GUIDANCE WOULD SUGGEST THAT STORM
   ACTIVITY SHOULD REMAIN TOO ISOLATED/SHORT-LIVED TO SUPPORT THE
   ISSUANCE OF A WATCH.
   
   ..CARBIN.. 07/21/2011
   
   
   ATTN...WFO...LOT...MKX...DVN...
   
   LAT...LON   42548855 42558784 42028767 41808776 41448930 41638927
               42548855