MESOSCALE DISCUSSION 1777
   NWS STORM PREDICTION CENTER NORMAN OK
   0619 PM CDT TUE AUG 04 2009
   
   AREAS AFFECTED...ERN WY/WRN SD/NEB PANHANDLE
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 660...
   
   VALID 042319Z - 050015Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 660
   CONTINUES.
   
   THREAT OF SEVERE WINDS/HAIL AND AN ISOLD/BRIEF TORNADO REMAINS FOR
   WW660.
   
   FAVORABLE POST-FRONTAL UPSLOPE AND SUBTLE FORCING ALOFT HAS
   INFLUENCED THUNDERSTORM DEVELOPMENT IN A MOIST AND WEAKLY UNSTABLE
   ENVIRONMENT. NUMEROUS SURFACE BOUNDARIES WILL LIKELY CONTINUE TO BE
   A FOCUS FOR INITIAL/ONGOING DEVELOPMENT...INCLUDING THE FRONT ITSELF
   EXTENDING ROUGHLY FROM GILLETTE WY SWD TOWARDS CHEYENNE...AND E-W
   ORIENTED AREAS OF SURFACE CONVERGENCE NOTED ON THE LOWEST TILT JUST
   N AND S OF RIVERTON...AND A NW-SE ORIENTED ONE JUST N OF LARAMIE.
   ELY/SELY LOW LEVEL WINDS VEERING TO WLY AT ABOUT 40-50 KT AT
   MIDLEVELS WILL CONTINUE TO SUPPORT ROTATING UPDRAFTS...WITH STEEP
   LOW/MID LEVEL LAPSE RATES CONDUCIVE TO LARGE HAIL. LARGE TEMPERATURE
   DEW POINT SPREADS WILL LIKELY ENHANCE WIND SPEEDS AT THE SURFACE AS
   EVAPORATIVE COOLING STRENGTHENS DOWNBURST WINDS...WITH COLD POOLS
   GENERALLY ACCELERATING EWD.
   
   ..HURLBUT.. 08/04/2009
   
   
   ATTN...WFO...LBF...UNR...CYS...BYZ...RIW...
   
   LAT...LON   41020215 41010552 42360576 42790629 44320663 44820794
               45020429 44700375 44700324 45070271 45020198 41020215