MESOSCALE DISCUSSION 0497
   NWS STORM PREDICTION CENTER NORMAN OK
   0956 AM CDT FRI APR 17 2009
   
   AREAS AFFECTED...PORTIONS S-CENTRAL/SE TX.
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 159...
   
   VALID 171456Z - 171630Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 159
   CONTINUES.
   
   ANOTHER WW MAY BE REQUIRED WITHIN AN HOUR FARTHER E ACROSS PORTIONS
   SE TX.  MEANWHILE CONTINUE WW 159 BENEATH/AHEAD OF WRN MCS. 
   
   SFC MESOANALYSIS SHOWS MARINE/WARM FRONT FROM GLS BAY WNWWD ACROSS
   HOU METRO AREA TO BETWEEN SAT-AUS...INTERSECTING SRN PORTION OF
   CONVECTIVE COMPLEX JUST ABOVE BALCONES ESCARPMENT NNW OF SAT.  THIS
   BOUNDARY MAY DRIFT NWD SLIGHTLY BEFORE BEING OVERTAKEN BY MCS OR
   PRECURSORY CONVECTION DISCUSSED BELOW.  INITIAL MCS CONTINUES TO
   MOVE EWD OUT OF ERN PORTIONS HILL COUNTRY...AND IS EXPECTED TO CLEAR
   MOST OF ESCARPMENT AND I-35 BETWEEN ACT-AUS WITHIN NEXT 1-2 HOURS. 
   ACTIVITY IS BEING AIDED BY ASCENT N OF WARM FRONT...BUT BOUNDARY IS
   SUFFICIENTLY SHALLOW THAT STG-SVR GUSTS GENERATED ALOFT STILL MAY
   REACH SFC IN DAMAGING FORM.  WITH NWD EXTENT...INFLOW-LAYER PARCELS
   BECOME PROGRESSIVELY/GRADUALLY MORE ELEVATED...AND MUCAPE GRADUALLY
   DIMINISHES FROM AROUND 2000 J/KG NEAR WARM FRONT TO APPROXIMATELY
   1000 J/KG JUST N OF WW.  WIND THREAT LESSENS AND MRGL-SVR HAIL IS
   PRIMARY CONCERN FROM NRN FRINGES OF WW TOWARD I-20.
   
   CONVECTION CONTINUES TO DEEPEN AND INCREASE IN COVERAGE E OF
   MCS...ACROSS ERN PORTIONS WW AND JUST W OF CLL-VCT LINE.  THIS
   ACTIVITY MAY TURN RIGHTWARD AND CONGEAL/DEVELOP INTO LEADING MCS
   WITH TIME.  POTENTIAL EXISTS FOR ANY RELATIVELY SUSTAINED/DISCRETE
   ACTIVITY TO ROTATE AND PERHAPS PRODUCE TORNADOES WITHIN WARM FRONTAL
   ZONE...WHERE NRN PORTION OF MOST UNSTABLE SFC-BASED INFLOW OVERLAPS
   FAVORABLY BACKED SFC WINDS AND ENLARGED BOUNDARY LAYER HODOGRAPHS
   BENEATH 40-55 KT LLJ.  MODIFIED VWP/PROFILER WINDS AND RUC SOUNDINGS
   EACH INDICATE 0-1 KM SRH 300-400 J/KG IN FRONTAL ZONE.  CAPPING
   SHOULD REMAIN PROGRESSIVELY STRONGER SWD FROM FRONT...PER MODIFIED
   CRP RAOB AND RUC FCST SOUNDINGS...LIMITING BACKBUILDING POTENTIAL
   FROM TX COASTAL BEND AREA SWD.
   
   ..EDWARDS.. 04/17/2009
   
   
   ATTN...WFO...LCH...SHV...HGX...FWD...CRP...EWX...
   
   LAT...LON   28219937 28200028 29190065 29919844 30629765 31729755
               32059660 31719479 31149381 30519368 29679384 29699401
               29409467 29299474 29029515 28539606 28319644 28139676
               28219937