MESOSCALE DISCUSSION 1267
   NWS STORM PREDICTION CENTER NORMAN OK
   0629 PM CDT SUN JUN 21 2009
   
   AREAS AFFECTED...PARTS OF NERN WY / SERN MT
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 212329Z - 220030Z
   
   A POSSIBLE ISOLD LARGE HAIL THREAT MAY DEVELOP AND LINGER FOR THE
   NEXT FEW HOURS.  A WW IS UNLIKELY.
   
   SATELLITE IMAGERY SHOWS SCATTERED TSTMS HAVE INITIATED AROUND THE
   HIGHER TERRAIN OF THE BIG HORN MTNS.  THIS AREA IS WITHIN A
   DIFFLUENT UPPER FLOW REGIME AHEAD OF MID-LEVEL MOISTENING--LIKELY
   AIDED BY WEAK LARGE SCALE ASCENT BY LEFT EXIT REGION OF WRN U.S.
   UPPER JET.  KBLX SINGLE SITE DATA IN THE PAST HOUR HAS SHOWN A
   RIGHT-MOVING SUPERCELL OVER SHERIDAN/CAMPBELL COUNTY WY WITH IT
   WEAKENING RECENTLY...WHEREAS A MORE RECENT STORM SPLIT OCCURRED OVER
   SERN BIG HORN COUNTY MT.  23Z SURFACE MESOANALYSIS INDICATES A
   PRESSURE TROUGH EXTENDS SWWD FROM WRN ND TOWARDS THE BIG HORN
   RANGE...WHERE LOWER 50S DEWPOINTS ARE LOCATED.
   
   STRAIGHT-LINE AND SEEMINGLY SUFFICIENT DEEP LAYER FLOW PROFILES
   /30-40 KTS EFFECTIVE SHEAR/ ACCORDING TO RUC FORECAST SOUNDINGS ARE
   SUPPORTING STORM ORGANIZATION WITHIN A RATHER STEEP LAPSE
   RATE/MODESTLY UNSTABLE AIRMASS /UP TO 1000 J/KG SBCAPE/.  AS A
   RESULT...THE STRONGER UPDRAFTS EXHIBITING ROTATION MAY IN TURN BE
   CAPABLE OF ISOLD LARGE HAIL.
   
   ..SMITH.. 06/21/2009
   
   
   ATTN...WFO...UNR...BYZ...RIW...
   
   LAT...LON   44510621 44700679 45050742 45480763 45770742 46000700
               46110651 46070561 45640481 45230471 44790486 44540543
               44510621