MESOSCALE DISCUSSION 0501
   NWS STORM PREDICTION CENTER NORMAN OK
   0145 PM CDT FRI APR 17 2009
   
   AREAS AFFECTED...PORTIONS SE TX.
   
   CONCERNING...TORNADO WATCH 160...
   
   VALID 171845Z - 172045Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 160 CONTINUES.
   
   THOSE PORTIONS OF THIS WW BENEATH AND AHEAD OF ONGOING MCS SHOULD BE
   CONTINUED FOR TIME BEING.
   
   SFC MESOANALYSIS SHOWS MARINE FRONT NOW QUASISTATIONARY FROM
   OFFSHORE SABINE PASS WNWWD ACROSS SRN GLS BAY AREA TO ITS
   INTERSECTION WITH CONVECTIVE COMPLEX OVER AUSTIN COUNTY.  LOW LEVEL
   SHEAR IS FAVORABLE...AND WILL REMAIN SO...INVOF FRONTAL ZONE.  STG
   LLJ OF 50-55 KT REMAINS EVIDENT IN HGX/LCH VWP...PERHAPS EXAGGERATED
   SOMEWHAT BY MOTION OF BIRDS/BUGS IN THAT LAYER...BASED ON
   SEMICIRCULAR ANNULUS OF REFLECTIVITY IN THAT LAYER FROM HGX RADAR
   AND COMPARISONS WITH PRE-STORM LDB PROFILER WINDS AND AREA RUC
   SOUNDINGS.  STILL...45-50 KT FLOW IS LIKELY WITHIN APPROXIMATELY 1
   KM AGL...KEEPING HODOGRAPHS ENLARGED AND 300-400 J/KG SRH IN THAT
   LAYER.  THICKENING ANVIL CLOUD COVER HAS MITIGATED SFC
   HEATING...CONTRIBUTING TO TENDENCY OF SBCINH TO INCREASE EWD ACROSS
   WW AREA INTO LA...AND MAKING EWD EXTENT OF SVR THREAT MORE
   UNCERTAIN/CONDITIONAL.  STILL...MODIFIED RUC SOUNDINGS SUGGEST
   1000-1500 J/KG MLCAPE OVER AND JUST S OF FRONT.  TORNADO POTENTIAL
   HAS BECOME MORE CONDITIONAL GIVEN INCREASED CINH AND MESSY STORM
   STRUCTURES...BUT DOES STILL EXIST...ESPECIALLY WHERE STORMS CROSS
   THROUGH FRONTAL ZONE.  SVR POTENTIAL IS FCST TO DIMINISH WITH NWD
   EXTENT FROM FRONT AS INFLOW-LAYER PARCELS BECOME
   PROGRESSIVELY/GRADUALLY MORE ELEVATED...AND AS MUCAPE DECREASES.
   
   ..EDWARDS.. 04/17/2009
   
   
   ATTN...WFO...LCH...HGX...CRP...EWX...
   
   LAT...LON   28429639 29069690 29279654 29639686 29889618 30479593
               30829581 30819561 30749528 30769507 30509488 30549403
               30219412 30239371 29849377 29809393 29689383 29429468
               29289477 28939531 28429639