MESOSCALE DISCUSSION 0509
   NWS STORM PREDICTION CENTER NORMAN OK
   0552 PM CDT THU APR 21 2011
   
   AREAS AFFECTED...FAR NERN UT AND S-CNTRL WY...NWRN CO
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 212252Z - 212345Z
   
   POTENT UPPER SHORTWAVE /OBSERVED IN RECENT VAPOR IMAGERY/ CURRENTLY
   POSITIONED OVER CNTRL UT CONTINUES TO PROGRESS EWD...WITH STRONG
   MOIST ASCENT AND MIDLEVEL CAA SPREADING AHEAD OF THIS FEATURE INTO
   THE CNTRL ROCKIES. THIS HAS SUPPORTED ONGOING ISO-SCT THUNDERSTORMS
   ACROSS THE REGION...WITH RECENT RADAR TRENDS INDICATING A FEW
   EXHIBITING LOW-TOPPED SUPERCELL CHARACTERISTICS AT TIMES. THE
   ENVIRONMENT NEAR THESE STORMS IS CHARACTERIZED BY STRONG EFFECTIVE
   BULK WIND SHEAR OF 50+ KTS...ALONG WITH STEEP MIDLEVEL LAPSE RATES
   OF 8-9 DEG C/KM. THE PRIMARY LIMITING FACTORS FOR MORE ROBUST
   CONVECTIVE DEVELOPMENT CONTINUE TO BE A DRY BOUNDARY LAYER /DEW
   POINTS GENERALLY IN THE 30S/ WHICH WILL ONLY YIELD MLCAPE VALUES
   AROUND 250-500 J/KG. HOWEVER...A THREAT FOR MARGINALLY SVR HAIL AND
   DMGG WIND GUSTS WILL PERSIST INTO THE EVENING HRS...BUT DUE TO THE
   EXPECTED ISOLATED COVERAGE A WW WILL NOT BE NEEDED.
   
   ..ROGERS.. 04/21/2011
   
   
   ATTN...WFO...PUB...BOU...CYS...RIW...GJT...
   
   LAT...LON   39120600 38890725 38980853 39170965 39690980 40550963
               41290845 41650702 41690635 41570587 40970509 40460488
               39890511 39470524 39120600