MESOSCALE DISCUSSION 0414
   NWS STORM PREDICTION CENTER NORMAN OK
   0440 PM CDT WED APR 21 2004
   
   AREAS AFFECTED...CENTRAL AND WRN AR
   
   CONCERNING...TORNADO WATCH 99...
   
   VALID 212140Z - 212315Z
   
   THREAT OF TORNADOES AND VERY LARGE HAIL CONTINUES ACROSS CENTRAL AND
   WRN AR...WITHIN WW 99 AREA.  
   
   TWO LARGE...POTENTIALLY TORNADIC SUPERCELLS HAVE BECOME ESTABLISHED
   ALONG A SURFACE BOUNDARY EXTENDING FROM 30 N LIT WEST TO NEAR FORT
   SMITH. EASTERNMOST SUPERCELL WAS LOCATED OVER ERN LOGAN AND NRN YELL
   COUNTIES IN AR AT 2130Z...MOVING ESEWD ALONG THE BOUNDARY AT 20-25
   KT. UPSTREAM SUPERCELL IS LOCATED JUST NORTHEAST OF FSM AT 2130Z.
   WITH MLCAPE VALUES AROUND 1000 J/KG...AND DEEP LAYER SHEAR REMAINING
   AROUND 40 KT THROUGH THIS EVENING...ENVIRONMENT WILL REMAIN
   FAVORABLE FOR TORNADOES AND VERY LARGE HAIL ACROSS THE WATCH AREA.
   LOCALLY HIGHER LOW-LEVEL SRH AND LOW LCL HEIGHTS IN VICINITY OF
   MESOSCALE BOUNDARY WILL ENHANCE TORNADO THREAT FROM FSM TO N OF LIT
   DURING THE NEXT 1-3 HOURS.
   
   ..BANACOS.. 04/21/2004
   
   
   ATTN...WFO...JAN...LZK...SHV...TSA...
   
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