MESOSCALE DISCUSSION 1718
   NWS STORM PREDICTION CENTER NORMAN OK
   1121 AM CDT SUN JUL 24 2011
   
   AREAS AFFECTED...IL
   
   CONCERNING...HEAVY RAINFALL 
   
   VALID 241621Z - 241815Z
   
   EXCESSIVE RAINFALL RATES OF UP TO 2 INCHES PER HOUR SEEM QUITE
   POSSIBLE ACROSS SECTIONS OF WESTERN AND CENTRAL IL OVER THE NEXT
   COUPLE OF HOURS.
   
   INGREDIENTS APPEAR TO BE COMING TOGETHER FOR A HEAVY TO EXTREME
   CONVECTIVE RAINFALL EVENT OVER IL AS TWO WELL-DEFINED OUTFLOW
   BOUNDARIES AND A WEAK MESOLOW AID ASCENT ACROSS THE REGION. RECENT
   INCREASE IN LIGHTNING ACTIVITY AND RAPID CLOUD TOP COOLING NEAR THE
   MESOLOW IN WRN IL ATTEST TO THE INCREASE IN FORCING AMIDST VERY
   MOIST AIRMASS WITH PW VALUES IN EXCESS OF 2 INCHES. THICKNESS
   DIFFLUENCE OVER THE AREA AND DEEP WARM CLOUD LAYER /OVER 4KM AOA 0C/
   PER ILX 12Z SOUNDING WILL PROVIDE ADDITIONAL SUPPORT FOR BOTH SLOW
   STORM MOTION AND EFFICIENT PRECIPITATION PROCESSES RESULTING IN
   LOCALLY EXTREME RAINFALL RATES OF AT LEAST 2 INCHES PER HOUR. THE
   GREATEST POTENTIAL SHOULD EVOLVE FROM FULTON...MASON...CASS...MENARD
   AND SANGAMON COUNTIES EAST ACROSS LOGAN...MACON...AND CHRISTIAN
   COUNTIES BASED ON CURRENT RADAR TRENDS AND MESOLOW EVOLUTION.
   
   ..CARBIN.. 07/24/2011
   
   
   ATTN...WFO...ILX...
   
   LAT...LON   39698873 39528918 39598949 39758985 40139019 40369042
               40569030 40608997 40388952 40308928 40118892 39698873