MESOSCALE DISCUSSION 1658
   NWS STORM PREDICTION CENTER NORMAN OK
   0704 PM CDT MON JUL 18 2011
   
   AREAS AFFECTED...WRN SD/SWRN ND
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 659...
   
   VALID 190004Z - 190100Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 659
   CONTINUES.
   
   THREAT OF DMGG WINDS...LARGE HAIL...AND PERHAPS AN ISOLATED TORNADO
   CONTINUE ACROSS PORTIONS OF THE DAKOTAS.
   
   CONVECTION INCREASED THROUGH THIS EVENING AHEAD OF A WEAK UPPER
   IMPULSE...OBSERVED ON 2345Z WV IMAGERY NEAR THE WRN SD/ND BORDER.
   LOW LEVEL WARM ADVECTION REGIME IN COMBINATION WITH VERY STEEP MID
   LEVEL LAPSE RATES WILL LIKELY CONTINUE TO SUPPORT NEARLY STATIONARY
   DEVELOPMENT THROUGH THE EVENING...WITH STRONG CLOUD BEARING SHEAR
   AND VEERING WINDS WITH HEIGHT FAVORABLE FOR OCCASIONALLY SPLITTING
   SUPERCELLS. EXPANSIVE ANVIL BLOW OFF FROM CURRENT CONVECTION APPEARS
   TO BE CONTRIBUTING TO RELATIVELY LESSENING INSTABILITY EAST OF THE
   CURRENT STORM NEAR HEI. HOWEVER...IF AN ORGANIZED COLD POOL BECOMES
   EVIDENT...EXTREME INSTABILITY STILL REMAINS FARTHER E DESPITE THE
   AFOREMENTIONED CLOUD COVER...AND COULD LEAD TO A MORE WIDESPREAD
   DMGG WIND EVENT. CONFIDENCE IN AN ORGANIZED COLD POOL DEVELOPING
   REMAINS LOW AT THIS TIME.
   
   ..HURLBUT.. 07/19/2011
   
   
   ATTN...WFO...GYX...BTV...ALY...
   
   LAT...LON   44967507 45017153 45247134 45287109 43917106 43887158
               43687157 43557200 43597231 43787234 43947283 43827299
               43787415 44077427 44087512 44487581 44967507