MESOSCALE DISCUSSION 1207
   NWS STORM PREDICTION CENTER NORMAN OK
   0117 PM CDT THU JUN 18 2009
   
   AREAS AFFECTED...ERN IA INTO CNTRL IL
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 462...
   
   VALID 181817Z - 181945Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 462
   CONTINUES.
   
   THE THREAT FOR MAINLY DAMAGING WINDS AND HAIL CONTINUES WITH ONGOING
   STORM OVER CNTRL PART OF WW AREA.  ADDITIONAL TSTM DEVELOPMENT IS
   POSSIBLE UPSTREAM OVER ERN IA LATER THIS AFTERNOON.
   
   AS OF 18Z...RADAR IMAGERY INDICATED A STORM WITH A HISTORY OF
   PRODUCING SEVERE HAIL AND WIND DAMAGE OVER HENRY COUNTY IL MOVING
   305/35-40 KT.  LATEST MESOANALYSIS SUGGESTS THAT THIS STORM REMAINS
   DISPLACED TO THE NE OF COMPOSITE OUTFLOW BOUNDARY WITH IMMEDIATE
   DOWNSTREAM SURFACE TEMPERATURES STILL IN THE 70S.  HOWEVER DSM VWP
   AND WINCHESTER IL PROFILER INDICATE THE PRESENCE OF WAA OCCURRING
   NEAR AND E OF SURFACE BOUNDARY ALONG AXIS OF 20-30 KT SWLY/WSWLY
   LLJ.  THUS...ONGOING STORM WILL LIKELY CONTINUE TO INGEST SLIGHTLY
   ELEVATED PARCELS ORIGINATING FROM WARM/MOIST LOW-LEVEL AIR MASS IN
   PLACE OVER THE LOWER MO VALLEY.  VERTICAL SHEAR WILL REMAIN
   FAVORABLE FOR UPDRAFT ORGANIZATION/ROTATION WITH SEVERE THREAT
   SPREADING SEWD INTO CNTRL IL.
   
   STRENGTHENING LOW-LEVEL WAA IN ADVANCE OF MIDLEVEL SHORT WAVE TROUGH
   CRESTING THE RIDGE AXIS OVER SD/NEB MAY SUPPORT ADDITIONAL UPSTREAM
   STORM DEVELOPMENT THIS AFTERNOON N OF PRIMARY SURFACE BOUNDARY OVER
   WRN PORTION OF WW AREA.
   
   ..MEAD.. 06/18/2009
   
   
   ATTN...WFO...LOT...ILX...DVN...DMX...
   
   LAT...LON   40669122 41249196 41719226 42399204 42639148 42519081
               41868934 41208835 40528842 39998923 40049007 40669122