MESOSCALE DISCUSSION 0280
   NWS STORM PREDICTION CENTER NORMAN OK
   0620 PM CDT TUE MAR 13 2007
   
   AREAS AFFECTED...S CNTRL AND S THROUGH SERN TX
   
   CONCERNING...TORNADO WATCH 60...
   
   VALID 132320Z - 140015Z
   
   SEVERE THUNDERSTORM WATCH 60 WILL LIKELY BE REPLACED BY ANOTHER WW
   SHORTLY THAT WILL INCLUDE PARTS OF SOUTH...S CNTRL AND SERN TX.
   THREAT WILL EXIST FOR ISOLATED DAMAGING WIND...LARGE HAIL AND
   POSSIBLY AN ISOLATED TORNADO OR TWO.
   
   EARLY THIS EVENING NUMEROUS STORMS CONTINUE DEVELOPING OVER S CNTRL
   TX ALONG A CONVECTIVE OUTFLOW BOUNDARY THAT EXISTS ON SRN END OF
   MCS. THE ATMOSPHERE REMAINS MODERATELY UNSTABLE ALONG AND S OF THIS
   BOUNDARY WITH MLCAPE FROM 1000 TO 1500 J/KG. ESELY LOW LEVEL FLOW
   BENEATH STRONGER MID LEVEL FLOW ON THE SRN PERIPHERY OF THE CUTOFF
   LOW IS CONTRIBUTING TO SUFFICIENT SHEAR PROFILES FOR SOME STORMS TO
   DEVELOP SUPERCELL STRUCTURES. LATEST VWP DATA SHOW DEEP LAYER SHEAR
   ON THE ORDER OF 40 KT WITH 0-1 STORM RELATIVE HELICITY AROUND 150
   M2/S2. THE LOW LEVEL JET IS EXPECTED TO UNDERGO ONLY A MODEST
   INCREASE OVERNIGHT. HOWEVER...LOW LEVEL INFLOW FROM THE MODERATELY
   UNSTABLE WARM SECTOR WILL MAINTAIN STRONGEST STORMS IN VICINITY OF
   OUTFLOW BOUNDARY NEXT FEW HOURS. STORMS WILL GRADUALLY SPREAD EAST
   TOWARD THE SERN TX COAST THIS EVENING.
   
   REMAINING PARTS OF WW 60 THAT INCLUDES MUCH OF CNTRL AND N CNTRL TX
   WILL BE ALLOWED TO EXPIRE SINCE MUCH OF THIS AREA HAS BEEN
   STABILIZED BY WIDESPREAD PRECIPITATION.
   
   ..DIAL.. 03/13/2007
   
   
   ATTN...WFO...HGX...CRP...EWX...
   
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