MESOSCALE DISCUSSION 0499
   NWS STORM PREDICTION CENTER NORMAN OK
   1238 PM CDT FRI APR 17 2009
   
   AREAS AFFECTED...PORTIONS S TX.
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 159...
   
   VALID 171738Z - 171815Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 159
   CONTINUES.
   
   NEW WW -- EITHER REPLACEMENT OR ADD-ON -- WILL BE REQUIRED BEFORE
   SCHEDULED 18Z EXPIRATION OF WW 159...IN ORDER TO REFINE SVR THREAT
   NEXT SEVERAL HOURS TO AREAS ALONG AND S OF CURRENT SRN SEGMENT OF
   MCS.
   
   DESPITE PERSISTENT LOW CLOUD OVER...INFLOW-LAYER AIR MASS FROM S OF 
   COMPLEX WILL CONTINUE TO EXPERIENCE STEADY HEATING FOR ANOTHER FEW
   HOURS.  THIS WILL COMBINE WITH SFC DEW POINTS NEAR 70 F TO BOOST
   MLCAPE INTO 2000-2500 J/KG RANGE.  ALTHOUGH STRONGEST LOW LEVEL
   SHEAR WILL REMAIN FARTHER E -- IN CLOSER PROXIMITY TO LLJ MAX AND
   WARM FRONT AND IN WW 160 -- 0-1 KM SRH 100-200 J/KG ACROSS THIS AREA
   INDICATE SOME POTENTIAL FOR ROTATING STORMS AND RELATED HAIL THREAT.
    TORNADO POTENTIAL CANNOT BE RULED OUT...BUT IS MODE DEPENDENT ON
   STORM-SCALE PROCESSES THAN FARTHER E.  FAVORABLE STORM-RELATIVE
   INFLOW IS FCST TO CONTINUE ACROSS THIS REGION -- 25-35 KT IN LOWEST
   2 KM AGL.  REF HEAVY RAINFALL MESOSCALE DISCUSSION 498 FOR THAT
   HAZARD.
   
   ..EDWARDS.. 04/17/2009
   
   
   ATTN...WFO...HGX...CRP...EWX...
   
   LAT...LON   28229957 29519834 29539757 29829670 28859675 28069701
               27959819 27979908 28229957