MESOSCALE DISCUSSION 1253
   NWS STORM PREDICTION CENTER NORMAN OK
   1240 PM CDT SAT JUN 20 2009
   
   AREAS AFFECTED...SRN/ERN NV AND WRN UT
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 201740Z - 201915Z
   
   STRONG THUNDERSTORM WIND GUSTS AND LARGE HAIL ARE POSSIBLE OVER
   SRN/ERN NV INTO WRN UT DURING THE REMAINDER OF THIS MORNING AND INTO
   THE AFTERNOON. THE AREA IS BEING MONITORED FOR A WW.
   
   12Z UPPER AIR ANALYSIS AND RECENT WV IMAGERY DEPICT A COMPACT BUT
   RATHER POTENT S/W TROUGH MOVING E INTO THE GREAT BASIN. STRONG UVV/S
   OCCURRING AHEAD OF THIS FEATURE ARE FOCUSING A CONCENTRATED AREA OF
   THUNDERSTORM DEVELOPMENT OVER SRN/ERN NV. A COLD MID LEVEL AIRMASS
   /AOB -12 DEG C/ IS ALSO ADVANCING E WITH THE UPPER TROUGH...AND IS
   AIDING IN STEEPENING LOW TO MID LEVEL LAPSE RATES. SURFACE
   TEMPERATURES SOUTH AND EAST OF A BAND OF CLOUDINESS POSITIONED OVER
   CENTRAL INTO ERN/NERN NV ARE EXPECTED TO CONTINUE WARMING INTO THE
   70S AND 80S. THIS HEATING COMBINED WITH MODEST SURFACE DEWPOINTS
   /MAINLY IN THE LOW TO MID 40S/ RESIDING ALONG AND TO THE COOL SIDE
   OF A COLD FRONT POSITIONED FROM NEAR SLC TO JUST N OF LAS...WILL AID
   IN THE DEVELOPMENT OF 1000 J/KG MLCAPE. THE COMBINATION OF FAVORABLE
   LARGE SCALE ASCENT...FRONTAL FORCING...AND INCREASING POTENTIAL
   INSTABILITY SHOULD MAINTAIN CURRENT STORMS OVER SRN NV...WITH A
   POSSIBLE EXPANSION IN COVERAGE NEWD INTO UT.
   
   RUC FORECAST GUIDANCE AND VWP DATA INDICATE A BAND OF 40 KT MID
   LEVEL FLOW POSITIONED ALONG THE SRN AND ERN FRINGE OF THE MID/UPPER
   LEVEL TROUGH. THIS FLOW WILL FAVOR SUFFICIENT VERTICAL WIND SHEAR
   FOR ORGANIZED THUNDERSTORM DEVELOPMENT...INCLUDING SUPERCELLS.
   RELATIVELY COLD MID LEVEL TEMPERATURES AND STEEP LAPSE RATES MAY
   YIELD STORMS POSING A LARGE HAIL THREAT...WHILE STEEPENING LOW LEVEL
   LAPSE RATES AND MODERATELY STRONG FLOW ALOFT COULD ALSO RESULT IN A
   DAMAGING WIND THREAT.
   
   ..GARNER.. 06/20/2009
   
   
   ATTN...WFO...SLC...VEF...LKN...
   
   LAT...LON   36441621 36881680 38221662 40491425 40861301 40371250
               39451238 38381302 37061430 36391549 36441621