MESOSCALE DISCUSSION 1603
   NWS STORM PREDICTION CENTER NORMAN OK
   0510 PM CDT SAT JUL 10 2004
   
   AREAS AFFECTED...CNTRL/ERN SD
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 596...
   
   VALID 102210Z - 110015Z
   
   CONTINUE WW 596...SEVERE THREAT WILL EVENTUALLY INCREASE EAST OF WW
   596 BY THE 11/00-02Z TIME FRAME.
   
   EVOLUTION OF VIGOROUS CONVECTIVE CLUSTER IS UNDERWAY...AND APPEARS
   TO BE ASSOCIATED WITH FORCING NEAR WEAK MID-LEVEL JET STREAK/SHORT
   WAVE TROUGH...EMBEDDED WITHIN SUBTROPICAL WESTERLIES AND MIGRATING
   OUT OF THE NORTH CENTRAL ROCKIES THIS AFTERNOON.  ONLY SLOW EASTWARD
   PROGRESSION OF UPPER SYSTEM IS PROGGED BY MODELS THROUGH THE MID
   EVENING HOURS...AND CLUSTER OF STORMS WILL CONTINUE TO EXPAND
   THROUGH 11/00Z IN UNSTABLE BOUNDARY LAYER WITH MEAN MIXED LAYER CAPE
   OF 1500 TO 3000 J/KG.  
   
   THERMODYNAMIC ENVIRONMENT WITH DEEP MIXED BOUNDARY LAYER ACROSS
   CENTRAL SOUTH DAKOTA WILL REMAIN SUPPORTIVE OF DOWNBURSTS NEAR
   STRONGER CELLS...WITH EVENTUAL EVOLUTION OF SIGNIFICANT SURFACE COLD
   POOL AND BROADER SCALE DAMAGING WIND THREAT LIKELY AFTER 11/00Z. 
   UNTIL THIS OCCURS...EVOLVING CONVECTIVE SYSTEM WILL BE SLOW TO
   ADVANCE EAST OF PIERRE AND SURROUNDING AREAS OF CENTRAL SOUTH
   DAKOTA.
   
   ..KERR.. 07/10/2004
   
   
   ATTN...WFO...FSD...ABR...LBF...UNR...
   
   45160067 45859970 45579818 45019723 43949771 43279856
   42970043 43340138 44110067