MESOSCALE DISCUSSION 1912
   NWS STORM PREDICTION CENTER NORMAN OK
   0209 PM CDT SUN JUL 20 2003
   
   AREAS AFFECTED...SERN SD...ERN NEB...WRN IA
   
   CONCERNING...SEVERE THUNDERSTORM POTENTIAL 
   
   VALID 201909Z - 202015Z
   
   ...SEVERE THUNDERSTORMS SHOULD DEVELOP WITHIN THE NEXT FEW HOURS
   ACROSS THE MID MO VALLEY REGION.  WW WILL LIKELY BE ISSUED
   SHORTLY...
   
   MID LEVEL CONVECTIVE FIELD IS EXPANDING WITHIN WARM ADVECTION ZONE
   ACROSS SERN SD.  THIS ACTIVITY APPEARS TO BE INITIATING OVER
   REMNANTS OF OLD CONVECTIVE BUBBLE HIGH WHERE BOUNDARY LAYER REMAINS
   CAPPED.  OF PARTICULAR CONCERN IS THE WEAKENING INHIBITION AXIS
   ACROSS NERN NEB INTO THIS ZONE WHERE EXTREME INSTABILITY HAS
   DEVELOPED...MLCAPES OF 4000-5000J/KG.  DEEP NWLY VERTICAL SHEAR
   APPROACHING 40-50KT WILL UNDOUBTEDLY SUPPORT SUPERCELL DEVELOPMENT. 
   STORM INITIATION MAY OCCUR AT MID LEVELS...QUICKLY BECOMING ROOTED
   WITHIN MORE UNSTABLE AIRMASS WHERE VERY LARGE HAIL AND DAMAGING
   WINDS ARE LIKELY.  WW WILL LIKELY BE ISSUED SHORTLY.
   
   ..DARROW.. 07/20/2003
   
   
   ATTN...WFO...DMX...FSD...OAX...GID...LBF...
   
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