MESOSCALE DISCUSSION 1713
   NWS STORM PREDICTION CENTER NORMAN OK
   0351 PM CDT TUE AUG 13 2013

   AREAS AFFECTED...PORTIONS OF WRN SD AND NERN WY

   CONCERNING...SEVERE THUNDERSTORM WATCH 491...

   VALID 132051Z - 132215Z

   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 491
   CONTINUES.

   SUMMARY...THE SVR POTENTIAL CONTINUES ACROSS WW 491.

   DISCUSSION...MODERATE TO STRONG INSTABILITY EXISTS ACROSS AREAS VOID
   OF PRIOR CONVECTIVE OVERTURNING...WITHIN A CORRIDOR OF MODESTLY RICH
   LOW-LEVEL MOISTURE ACROSS THE MCD AREA. WITH AROUND 30-35 KT OF
   0-6-KM BULK SHEAR AND A VERTICALLY VEERING WIND PROFILE SAMPLED BY
   UDX VWP DATA...THE POTENTIAL FOR ORGANIZED SVR CONVECTION CONTINUES.

   CONVECTIVE CLUSTERS WITH EMBEDDED INTENSE CORES/POSSIBLE SUPERCELLS
   CONTINUE TO SPREAD SEWD ACROSS FAR WRN SD. MERGING COLD POOLS APPEAR
   TO HAVE BEEN ASSOCIATED WITH SOME INCREASE IN THE COVERAGE OF THIS
   ACTIVITY FROM SRN BUFFALO COUNTY INTO BUTTE COUNTY SD...WITH
   ADDITIONAL DEVELOPMENT ALONG THE SWRN FLANK OF RELATED COLD POOLS
   INTO CROOK COUNTY WY. THIS ACTIVITY WILL ADVANCE SEWD/PERHAPS SSEWD
   DURING THE NEXT COUPLE OF HOURS...AND COULD EVENTUALLY APPROACH THE
   RAPID CITY AREA. BASE VELOCITY DATA FROM RAPID CITY WSR-88D INDICATE
   SMALL...BUT INTENSE...REAR-INFLOW JETS ACCOMPANYING THIS
   CONVECTION...AND SVR WIND GUSTS WILL BE POSSIBLE WITH THIS ACTIVITY.
   ALSO...NSSL WDSS-2 MESH DATA INDICATE MAXIMUM HAIL SIZES
   MEETING/EXCEEDING SVR THRESHOLDS WITH THE MOST INTENSE CORES...AND
   SVR HAIL WILL CONTINUE TO BE A CONCERN. STORMS NEAR THE BLACK HILLS
   MAY ALSO POSE A SVR THREAT IN THE SHORT TERM AS THEY SLOWLY MOVE
   SEWD.

   ..COHEN.. 08/13/2013


   ATTN...WFO...UNR...

   LAT...LON   43210327 44010477 44660477 45020370 45680298 45540214
               44510140 43600101 43160139 43210327