MESOSCALE DISCUSSION 0853
   NWS STORM PREDICTION CENTER NORMAN OK
   0301 PM CDT WED MAY 20 2009
   
   AREAS AFFECTED...WRN NEB...NE CO
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 202001Z - 202130Z
   
   AN ISOLATED SEVERE THREAT SHOULD DEVELOP ACROSS PARTS OF WRN NEB AND
   NE CO LATE THIS AFTERNOON. LARGE HAIL AND A FEW DAMAGING WIND GUSTS
   WILL BE POSSIBLE AS CELLS STRENGTHEN AND MOVE INTO INCREASING
   INSTABILITY. A WW MAY BECOME NECESSARY.
   
   LATEST SFC ANALYSIS SHOWS A COLD FRONT ADVANCING SEWD ACROSS WCNTRL
   NEB WITH A SFC TROUGH EXTENDING WNWWD ACROSS SERN WY. SFC TEMPS HAVE
   WARMED QUICKLY INTO THE MID TO UPPER 80S F ALONG THIS TROUGH AND
   THUNDERSTORMS HAVE INITIATED NEAR THE THERMAL AXIS IN SERN WY. THIS
   CONVECTION IS BEING SUPPORTED BY AN APPROACHING SHORTWAVE TROUGH
   EVIDENT ON WATER VAPOR IMAGERY. INCREASING LARGE-SCALE ASCENT SHOULD
   RESULT IN EXPANDING STORM COVERAGE EWD INTO WRN NEB OVER THE NEXT 1
   TO 3 HOURS. FORECAST SOUNDINGS LATE THIS AFTERNOON ALONG THE TROUGH
   AND COLD FRONT SHOW MODERATE TO STRONG VERTICAL SHEAR PROFILES WITH
   A GRADUAL INCREASE IN SHEAR NWD TO THE WY STATE-LINE. THIS ALONG
   WITH STEEP MID-LEVEL LAPSE RATES ASSOCIATED WITH AN ELEVATED MIXED
   LAYER EXTENDING NEWD FROM CO SHOULD BE SUFFICIENT FOR ISOLATED
   SEVERE HAILSTORM. ALTHOUGH DEWPOINTS ALONG THE FRONT ARE GENERAL IN
   THE LOWER TO MID 50S F...LOW-LEVEL LAPSE RATES ARE QUITE STEEP WHICH
   COULD BE ENOUGH FOR A FEW DAMAGING WIND GUSTS ESPECIALLY IF A SHORT
   BOWING LINE-SEGMENTS CAN ORGANIZE.
   
   ..BROYLES.. 05/20/2009
   
   
   ATTN...WFO...LBF...UNR...BOU...CYS...
   
   LAT...LON   42480306 43310132 43570050 43429990 42869950 42030012
               41010188 40510343 40630463 41450493 41880473 42160415
               42480306