MESOSCALE DISCUSSION 1770
   NWS STORM PREDICTION CENTER NORMAN OK
   1249 PM CDT THU AUG 16 2007
   
   AREAS AFFECTED...SE IL AND SRN INDIANA
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 602...
   
   VALID 161749Z - 161845Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 602
   CONTINUES.
   
   THE MCS IN CENTRAL IL MAY PERSIST INTO THE AFTERNOON...WITH AN
   ATTENDANT THREAT FOR DAMAGING WINDS.  AN ADDITIONAL SEVERE
   THUNDERSTORM WATCH MAY BE NEEDED BY 19Z ACROSS SRN INDIANA.
   
   SHORT TERM RADAR/SATELLITE TRENDS SUGGEST THAT THE SMALL MCS OVER
   CENTRAL IL HAS WEAKENED SOME SINCE 17Z.  HOWEVER...STRONG SURFACE
   HEATING IS OCCURRING IN ADVANCE OF THIS CONVECTION...ALONG AND S OF
   A REMNANT OUTFLOW BOUNDARY ACROSS SE IL AND SRN INDIANA.  THIS
   HEATING/MIXING IS RESULTING IN STEEP LOW-LEVEL LAPSE RATES AND THE
   POTENTIAL FOR STRONG DOWNDRAFTS...AS WELL AS STRONG INSTABILITY
   ALONG THE BOUNDARY /MLCAPE IN EXCESS OF 3000 J/KG/.  DESPITE THE
   SHORT TERM TRENDS...THE POTENTIAL WILL EXIST FOR THE ONGOING STORMS
   TO INTENSIFY...OR FOR NEW CONVECTION TO FORM ALONG THE OUTFLOW
   BOUNDARIES.  DAMAGING WINDS AND ISOLATED LARGE HAIL WILL BE THE
   PRIMARY SEVERE THREATS...AND AN ADDITIONAL SEVERE THUNDERSTORM WATCH
   MAY BECOME NECESSARY BY 19Z ACROSS SRN INDIANA.
   
   ..THOMPSON.. 08/16/2007
   
   
   ATTN...WFO...ILN...LMK...IND...PAH...ILX...
   
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