MESOSCALE DISCUSSION 1237
   NWS STORM PREDICTION CENTER NORMAN OK
   0154 PM CDT FRI JUN 19 2009
   
   AREAS AFFECTED...ERN IA INTO NRN IL
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 477...
   
   VALID 191854Z - 192030Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 477
   CONTINUES.
   
   TSTMS ARE EXPECTED TO SPREAD EWD ACROSS WW AREA LATER THIS AFTERNOON
   AND EVENING AND A NEW WW WILL BE REQUIRED PRIOR TO 20Z.
   
   LATEST TRENDS IN SURFACE OBSERVATIONAL DATA INDICATE THAT
   CONSIDERABLE BOUNDARY LAYER WARMING AND SOME MOISTENING HAS OCCURRED
   SINCE MID MORNING IN THE WAKE OF EARLIER...NOCTURNAL TSTM
   DEVELOPMENT.  THIS IS GENERALLY SUPPORTED BY THE ENHANCED CUMULUS
   FIELD OBSERVED OVER PORTIONS OF SERN IA INTO PARTS OF IL S OF THE
   I-80 CORRIDOR.
   
   WHILE IT REMAINS UNCERTAIN AS TO WHETHER IN SITU STORM FORMATION
   WILL OCCUR WITHIN DESTABILIZING AIR MASS ACROSS WW AREA...LATEST
   RADAR TRENDS AND NUMERICAL GUIDANCE BOTH SUGGEST A HIGH PROBABILITY 
   OF TSTMS MOVING INTO THE AREA FROM THE WEST LATER THIS AFTERNOON
   INTO EVENING.  GIVEN MODERATE INSTABILITY AND 50-60 KT OF DEEP-LAYER
   SHEAR...THE POTENTIAL WILL EXIST FOR BOWING CONVECTIVE STRUCTURES
   CAPABLE OF MAINLY DAMAGING WINDS AND HAIL.
   
   ..MEAD.. 06/19/2009
   
   
   ATTN...WFO...LOT...ILX...DVN...DMX...
   
   LAT...LON   41809226 42299197 42519129 42478915 42458824 41938779
               41108773 40738784 40658857 40629019 40709147 41129221
               41809226