MESOSCALE DISCUSSION 2040
   NWS STORM PREDICTION CENTER NORMAN OK
   1131 AM CDT SAT AUG 20 2005
   
   AREAS AFFECTED...MUCH OF OH...PORTIONS ERN/SRN INDIANA...NRN
   KY...EXTREME SERN IL
   
   CONCERNING...SEVERE THUNDERSTORM POTENTIAL 
   
   VALID 201631Z - 201800Z
   
   TSTMS MAY DEVELOP AND QUICKLY BECOME SEVERE WIND PRODUCERS AS THEY
   MOVE EWD ACROSS DISCUSSION AREA...WHERE WW MAY BE REQUIRED IN NEXT
   1-2 HOURS.
   
   PROSPECTIVE INFLOW AIR OVER INDIANA/OH/NRN KY SOON WILL BECOME
   EXTREMELY UNSTABLE...WITH ADEQUATE VERTICAL SHEAR TO SUPPORT
   ORGANIZED DAMAGING WIND EVENT...POSSIBLY DERECHO CALIBER.  VIS
   IMAGERY SHOWS NE-SW ORIENTED BAND OF LOW-MIDDLE LEVEL CLOUDS...FROM
   NERN INDIANA SWWD ROUGHLY ALONG HUF...MVN...CGI LINE...MOVING EWD
   APPROXIMATELY 35 KT.  SWRN PORTION OF THIS LINE OVER IL BECOMES
   COLOCATED WITH PROGRESSIVE OUTFLOW BOUNDARY FROM EARLIER
   ACTIVITY...STILL CHARACTERIZED BY SFC PRESSURE RISES TO ITS W. 
   CONVECTIVE CLOUDS ARE DEEPENING AND INCREASING IN COVERAGE OVER SRN
   IL PORTION OF THIS BAND...AND ALSO OVER SEGMENT NNE IND.  DURING
   NEXT 2-3 HOURS...TSTMS MAY DEVELOP WITHIN BAND AND MOVE INTO RAPIDLY
   DESTABILIZING AIR MASS CHARACTERIZED BY TEMPS RISING INTO LOW 90S F
   AND SFC DEW POINTS LOW-MID 70S.  DESPITE WARM MIDLEVEL TEMPS...VERY
   HIGH BOUNDARY LAYER THETAE YIELDS DEEPLY BUOYANT PROFILE WITH VERY
   WEAK CINH...MLCAPES NEAR 4000 J/KG AND DCAPE ROUGHLY 1000 J/KG. 
   GIVEN MIDLEVEL WINDS UP TO 60 KT -- PER WLC PROFILER -- AND AT LEAST
   40 KT ALOFT OVER MUCH OF AREA...THIS SHOULD SUPPORT EVOLUTION OF
   ORGANIZED DAMAGING WIND EPISODE.
   
   ..EDWARDS.. 08/20/2005
   
   
   ATTN...WFO...PBZ...RLX...CLE...JKL...ILN...LMK...IWX...IND...PAH...ILX...
   
   38028578 37878685 37798790 37898858 38168875 38668794
   39338677 39868580 40578514 41608468 41718396 41608289
   41658144 40908105 39628154 38848255 38208400 38068532