MESOSCALE DISCUSSION 0674
   NWS STORM PREDICTION CENTER NORMAN OK
   1026 PM CDT FRI MAY 17 2013
   
   AREAS AFFECTED...NE WYOMING..SE MONTANA...WRN AND CENTRAL SOUTH
   DAKOTA
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 167...169...
   
   VALID 180326Z - 180430Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
   167...169...CONTINUES.
   
   SUMMARY...ISOLATED STRONG/SVR TSTMS CONTINUE TO PERSIST/DEVELOP
   ACROSS PORTIONS OF ERN WYOMING AND NRN NEBRASKA. AN ISOLATED
   HAIL/WIND THREAT MAY PERSIST FOR THE NEXT FEW HOURS...AT LEAST
   ACROSS WRN NEBRASKA.
   
   DISCUSSION...AT 03 UTC...A BROAD WAA REGIME WAS HELPING TO MAINTAIN
   SEVERAL CLUSTERS OF TSTMS ACROSS PORTIONS OF WW167/WW169. EMBEDDED
   IN THIS WAA REGIME STRONG/SVR TSTMS WERE ONGOING ACROSS NERN WYOMING
   /WESTIN AND CROOK COUNTIES/ AND NWRN NEBRASKA /CHERRY AND GRANT
   COUNTIES/. THE LARGE SCALE ENVIRONMENT IN WHICH THESE STORMS ARE
   DEVELOPING/MAINTAINING IS CHARACTERIZED BY MUCAPE VALUES BETWEEN
   500-1000 J/KG AND DEEP LAYER SHEAR AOA 35 KTS. GIVEN THE CONTINUED
   MAINTENANCE/DEVELOPMENT OF TSTMS IN SUCH A FAVORABLE
   ENVIRONMENT...THE SVR THREAT MAY PERSIST PAST THE EXPIRATION OF
   WW167 /04 UTC/. A LOCAL EXTENSION MAY BE REQUIRED.
   
   FARTHER E...ACROSS PORTIONS OF WW169...EARLIER CONVECTION HAS
   ACCELERATED EWD...WEAKENED...AND SHOULD EXIT WW169 IN THE NEXT 1-2
   HRS. UNLESS OBSERVATIONAL TRENDS SUGGEST AN UPTICK IN CONVECTIVE
   INTENSITY...OR THE DEVELOPMENT/INTENSIFICATION OF NEW CONVECTION
   WW169 COULD BE CANCELLED EARLY AS CONVECTION MOVES TO THE EAST.
   
   ..MARSH.. 05/18/2013
   
   
   ATTN...WFO...FSD...OAX...ABR...LBF...UNR...CYS...BYZ...
   
   LAT...LON   44970598 45079872 42819812 41190226 42610488 44970598