MESOSCALE DISCUSSION 0557
   NWS STORM PREDICTION CENTER NORMAN OK
   0406 PM CDT FRI APR 04 2008
   
   AREAS AFFECTED...TX UPPER COASTAL PLAIN AND SW LA
   
   CONCERNING...TORNADO WATCH 164...
   
   VALID 042106Z - 042230Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 164 CONTINUES.
   
   THREAT FOR ISOLATED DAMAGING WINDS...LARGE HAIL...AND PERHAPS A
   TORNADO WILL PERSIST THE NEXT FEW HOURS IN EXTREME SERN TX AND SWRN
   LA.  CLUSTER OF ONGOING STORMS IN SE TX WILL MOVE INTO SW LA THROUGH
   2230 UTC.  AN ISOLATED TORNADO THREAT APPEARS MOST PROBABLE ALONG AN
   WEST TO EAST ORIENTED OUTFLOW BOUNDARY.
   
   A CONVECTIVELY-INDUCED OUTFLOW BOUNDARY HAS SURGED SOUTH ACROSS
   PORTIONS OF SERN TX AND SWRN LA OVER THE PAST SEVERAL HOURS. 
   ONGOING ORGANIZED CONVECTION HAS BEEN CONFINED TO
   HARDIN...JASPER...AND LIBERTY COUNTIES IN TX OVER THE LAST HOUR ON
   THE PERIPHERY OF A WEAKLY UNSTABLE AIRMASS /AOB 250 J/KG MLCAPE/. 
   THE LATEST OBJECTIVE ANALYSIS SUGGESTS A SHALLOW STABLE LAYER EXISTS
   IMMEDIATELY NORTH OF THE OUTFLOW BOUNDARY.  RADAR TRENDS OVER THE
   PAST FEW HOURS INDICATE SUPERCELLS HAVE INITIATED NEAR THE WESTERN
   EDGE OF THIS BOUNDARY...THEN WEAKENED AS THEY MOVE NEWD INTO THE
   DEEPER STABLE AIRMASS.  HOWEVER...DEEPER LAYER SHEAR ON THE ORDER OF
   50 KTS...WILL ACT TO SUSTAIN ANY UPDRAFTS ROOTED IN OR NEAR THE
   SURFACE LAYER.  STORMS THAT CAN PROPAGATE EWD ALONG THE BOUNDARY
   WILL BE CAPABLE OF A LOCALLY ENHANCED SEVERE THREAT.
   
   ..SMITH.. 04/04/2008
   
   
   ATTN...WFO...LCH...HGX...
   
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