MESOSCALE DISCUSSION 0577
   NWS STORM PREDICTION CENTER NORMAN OK
   0521 PM CDT MON APR 25 2011
   
   AREAS AFFECTED...PORTIONS N-CENTRAL/NE TX THROUGH SERN OK.
   
   CONCERNING...TORNADO WATCH 201...
   
   VALID 252221Z - 252315Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 201 CONTINUES.
   
   ORIGINAL WW IS SCHEDULED TO EXPIRE AT 23Z...AND MAY BE ALLOWED TO DO
   SO OVER MOST AREAS EXCEPT FAR SRN PORTIONS.  WW SHOULD BE EXTENDED
   IN TIME AT LEAST FOR REMAINING COUNTIES BENEATH/AHEAD OF N-CENTRAL
   TX CONVECTION.
   
   SFC MESOANALYSIS SHOWS THERMAL GRADIENT/OUTFLOW BOUNDARY FROM
   EARLIER CONVECTION EXTENDING FROM NEAR PSN WNWWD TOWARD TSTM COMPLEX
   S OF DAL.  THIS CONVECTION...INCLUDING PREVIOUSLY TORNADIC
   SUPERCELL...WILL MOVE ESEWD ACROSS PORTIONS NAVARRO/HENDERSON
   COUNTIES DURING NEXT 2 HOURS...NEAR THAT BOUNDARY WHERE LOW-LEVEL
   SHEAR/VORTICITY AND STORM-RELATIVE INFLOW SHOULD BE MAXIMIZED. 
   MODIFIED RAOBS AND RUC SOUNDINGS SUGGEST 2000-2500 J/KG MLCAPE IN
   IMMEDIATE INFLOW REGION OF THIS CONVECTION...SUPPORTED BY SFC TEMPS
   80S F AND DEW POINTS UPPER 60S TO 70 F ALONG/S OF BOUNDARY.  AMBIENT
   STORM ENVIRONMENT WILL REMAIN FAVORABLE KINEMATICALLY AS WELL...WITH
   EFFECTIVE SHEAR MAGNITUDES 50-60 KT.  ONCE THIS ACTIVITY EXITS WW
   AREA...DRYLINE AND COLD FRONTAL PASSAGE WILL RESULT IN THREAT FOR
   TORNADIC TSTMS SHIFTING EWD INTO WW 205 AND SWD OVER WW 204. 
   QUASI-LINEAR ACTIVITY FARTHER NE ACROSS NE TX AND SE OK WILL BE
   COVERED BY WW 205.
   
   ..EDWARDS.. 04/25/2011
   
   
   ATTN...WFO...SHV...TSA...FWD...
   
   LAT...LON   31789811 32499696 33409614 34189520 33679534 32839556
               32019556 31789811