MESOSCALE DISCUSSION 1889
   NWS STORM PREDICTION CENTER NORMAN OK
   0716 PM CDT TUE SEP 17 2013

   AREAS AFFECTED...PARTS OF THE ERN GREAT BASIN AND CNTRL ROCKIES

   CONCERNING...SEVERE THUNDERSTORM WATCH 526...

   VALID 180016Z - 180145Z

   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 526
   CONTINUES.

   SUMMARY...OVERALL SEVERE THREAT APPEARS TO HAVE PEAKED WITHIN MOST
   OF WW 526 AS CONVECTIVE OUTFLOWS HAVE AIDED IN INCREASED
   SURFACE-BASED STABILIZATION. GREATEST SHORT-TERM POTENTIAL FOR
   SEVERE HAIL/WIND APPEARS PRIMARILY NEAR THE UT/CO/WY BORDER...BUT
   THIS CONVECTION SHOULD WEAKEN AS IT SHIFTS EWD THIS EVENING.

   DISCUSSION...MID-LEVEL REFLECTIVITY CORES HAVE WEAKENED WITH MUCH OF
   THE CONVECTION WITHIN/NEAR WW 526. STRONGER CELLS HAVE BECOME
   CONFINED TO NEAR THE UT/CO/WY BORDER AREA. HOWEVER...WITH DOWNSTREAM
   AIR MASS HAVING BEEN COOLED BY EARLIER CONVECTION /SURFACE
   TEMPERATURES LARGELY NOW IN THE 60S/...THESE STORMS WILL LIKELY
   WEAKEN GIVEN ONLY PERIPHERAL INFLUENCE OF LARGE-SCALE ASCENT.

   FARTHER N...MORE WIDESPREAD CONVECTION AND OVERTURNING HAS YIELDED
   SUBSTANTIAL STABILIZATION IN THE PAST HOUR...WITH THIS TREND LIKELY
   CONTINUING THIS EVENING. STRONGER FORCING FOR ASCENT SHOULD STILL
   SUSTAIN CONVECTION FOR SEVERAL MORE HOURS...BUT THE LACK OF GREATER
   BUOYANCY/INSTABILITY WILL LIKELY HAMPER SEVERE POTENTIAL BEYOND A
   MARGINAL/LOCALIZED THREAT.

   ..GRAMS.. 09/18/2013


   ATTN...WFO...BOU...CYS...BYZ...RIW...GJT...SLC...PIH...

   LAT...LON   41650629 40320695 40070829 39990981 40201045 40451084
               40931178 41171248 41441270 41861268 43041207 44181127
               44811053 45280980 45390906 45240777 44390653 41650629