MESOSCALE DISCUSSION 0639
   NWS STORM PREDICTION CENTER NORMAN OK
   0927 PM CDT WED APR 29 2009
   
   AREAS AFFECTED...CNTRL AND NRN NEB...ERN SD
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 300227Z - 300400Z
   
   A SEVERE THREAT SHOULD DEVELOP FROM CNTRL NEB NNEWD INTO NERN SD AS
   STORMS INITIATE AND EXPAND IN COVERAGE LATE THIS EVENING. HAIL AND
   ISOLATED WIND DAMAGE WILL BE THE PRIMARY THREATS. ALTHOUGH THE
   THREAT SHOULD REMAIN ISOLATED...A WATCH CAN NOT BE RULED OUT.
   
   SFC ANALYSIS CURRENTLY SHOWS A COLD FRONT MOVING SEWD ACROSS NRN NEB
   AND ECNTRL SD WITH A MOIST AXIS AHEAD OF THE BOUNDARY WITH MID TO
   UPPER 50S F DEWPOINTS. THE RUC SUGGESTS LOW-LEVEL CONVERGENCE IS
   INCREASING ALONG THE BOUNDARY AND THIS HAS HELPED INITIATE
   THUNDERSTORMS IN NRN NEB. THE THUNDERSTORMS IN NERN SD ARE
   DEVELOPING AHEAD OF THE BOUNDARY ON THE NRN END OF AN AXIS OF WEAK
   INSTABILITY. AS THE FRONT MOVES SEWD...THUNDERSTORM COVERAGE SHOULD
   INCREASE WITH A LINE OF CONVECTION EVENTUALLY ORGANIZING LATE THIS
   EVENING. STRONG VERTICAL SHEAR PROFILES EVIDENT ON FORECAST
   SOUNDINGS AND STEEP MID-LEVEL LAPSE RATES SUGGEST A THREAT FOR HAIL
   WILL EXIST WITH THE STRONGER CELLS EMBEDDED IN THE DEVELOPING LINE.
   FORECAST SOUNDINGS ALSO SHOW A SLIGHT CAPPING INVERSION WHICH SHOULD
   KEEP THE CONVECTION ELEVATED RESULTING IN ONLY A MARGINAL WIND
   DAMAGE THREAT.
   
   ..BROYLES.. 04/30/2009
   
   
   ATTN...WFO...FSD...ABR...GID...LBF...UNR...
   
   LAT...LON   42699860 41979874 41479892 41049953 40860010 40870056
               41040103 41650108 42480044 43129995 43489977 44509963
               45159929 45659867 45609791 45309756 44499779 43359844
               42699860