MESOSCALE DISCUSSION 0593
   NWS STORM PREDICTION CENTER NORMAN OK
   1046 PM CDT SUN APR 26 2009
   
   AREAS AFFECTED...PORTIONS W-CENTRAL/SW TX.
   
   CONCERNING...TORNADO WATCH 196...
   
   VALID 270346Z - 270545Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 196 CONTINUES.
   
   SVR AND POTENTIALLY TORNADIC SUPERCELLS WILL CONTINUE TO MOVE ESEWD
   GENERALLY ALONG I-10 FROM JCT AREA TOWARD ERV-FREDERICKSBURG REGION.
    ADDITIONAL DEVELOPMENT IS OCCURRING AND REMAINS POSSIBLE FARTHER NW
   BETWEEN SJT-MAF AND WWD TOWARD RETREATING DRYLINE DENOTED IN MCD
   GRAPHIC.
   
   DEEP-LAYER AND LOW-LEVEL SHEAR WILL REMAIN FAVORABLE...WITH
   EFFECTIVE SHEAR AROUND 50-60 KT EXPECTED TO PERSIST OVER REGION. 
   VWP FROM NEAR DRT HAS SHOWN STEADY STRENGTHENING AND DEEPENING OF
   LLJ DURING LAST COUPLE HOURS...WITH 40-45 KT FLOW COMMON THROUGH
   LOWEST 3 KM EXCEPT AT SFC...WHERE SELYS CONTRIBUTE TO ENLARGED
   HODOGRAPHS.  0-1 KM SRH DERIVED FROM THAT VWP IS IN GOOD GEN
   AGREEMENT WITH 350-400 J/KG VALUES IN RUC FCST SOUNDINGS.  BOTH SHOW
   PRONOUNCED WEAKNESSES IN FLOW JUST ABOVE LLJ THAT INDICATES
   MAINTAINING HIGH-REFLECTIVITY DISTRIBUTIONS AROUND BACK SIDE OF
   MESOCYCLONES.
   
   THERMODYNAMIC SIGNALS ARE SOMEWHAT MORE MIXED.  PRIMARY FAVORABLE
   FEATURE REMAINS RICH LOW LEVEL MOISTURE...WITH SFC DEW POINTS MID
   60S F BETWEEN JCT-DRT...AND NEAR 70 ABOUT 75 NM UPSTREAM FROM
   SAT-UVA...925 MB DEW POINTS 18-19 C UPSTREAM...850 MB DEW POINTS
   AROUND 14 C...AND 15-16 G/KG MIXING RATIOS.  MODIFIED DRT RAOB AND
   RUC FCST SOUNDINGS INDICATE ML PARCELS REMAIN ROOTED AT SFC OVER
   EDWARDS PLATEAU AND SRN HILL COUNTRY...BUT CINH INCREASES GREATLY
   EWD TOWARD AUS-SAT-HDO CORRIDOR.  SBCINH ALSO IS INCREASING OVER
   RETREATING DRYLINE...PER MODIFIED RAOBS AND PRESENCE OF
   INVERSION-AIDED A.P. IN REFLECTIVITY IMAGERY.  ALTHOUGH TIMING
   REMAINS UNCERTAIN GIVEN OBVIOUS STRENGTH OF SUPERCELLS AROUND
   JCT...PRIND THIS ACTIVITY EVENTUALLY WILL ENCOUNTER CINH TOO STG TO
   CONTINUE.  IF NECESSARY...A FEW COUNTIES MAY BE ADDED LOCALLY TO
   SERN FRINGE OF WW DEPENDING ON CONVECTIVE TRENDS AROUND 05-06Z.
   
   ..EDWARDS.. 04/27/2009
   
   
   ATTN...WFO...FWD...EWX...SJT...MAF...
   
   LAT...LON   29759891 30090042 30590171 31300186 32360132 32800007
               32659909 31479869 30189818 29759891