MESOSCALE DISCUSSION 0490
   NWS STORM PREDICTION CENTER NORMAN OK
   0836 PM CDT THU APR 16 2009
   
   AREAS AFFECTED...TX SOUTH PLAINS AND LOW ROLLING PLAINS SWD INTO THE
   PERMIAN BASIN AND CONCHO VALLEY
   
   CONCERNING...TORNADO WATCH 157...
   
   VALID 170136Z - 170300Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 157 CONTINUES.
   
   THROUGH 03Z...IT APPEARS THAT THE GREATEST THREAT FOR SUPERCELLS
   CAPABLE OF LARGE HAIL AND PERHAPS A TORNADO OR TWO WILL EXIST FROM
   MARTIN AND HOWARD COUNTIES NEWD INTO KENT AND STONEWALL COUNTIES. 
   FARTHER W...WIDESPREAD STORMS WILL YIELD LOCALLY EXCESSIVE RAINFALL
   /HOURLY RATES APPROACHING 1-2 INCHES/ IN ADDITION TO SOME HAIL. 
   THESE THREATS WILL GRADUALLY SPREAD EWD TOWARD THE I-27 CORRIDOR
   THROUGH 03Z.
   
   AS OF 0120Z...RADAR IMAGERY INDICATED THE MOST INTENSE STORMS
   /SUPERCELLS/ OVER MARTIN AND ERN GARZA/WRN KENT COUNTIES MOVING NEWD
   AT AROUND 30 KT.  THESE STORMS ARE SITUATED ALONG THE ERN FRINGE OF
   MORE WIDESPREAD TSTMS DEVELOPMENT...WITHIN A STRENGTHENING ESELY
   LOW-LEVEL FLOW REGIME.  MODIFICATION OF 00Z MAF SOUNDING FOR CURRENT
   BOUNDARY LAYER CONDITIONS WITHIN IMMEDIATE INFLOW REGION TO THESE
   STORMS SUGGESTS THAT ENVIRONMENT REMAINS MODERATELY UNSTABLE WITH
   SBCAPE OF 1000-1500 J/KG.  GIVEN THE STRENGTHENING LOW-LEVEL SHEAR
   AND LOW LCL HEIGHTS...A TORNADO OR TWO REMAINS POSSIBLE PRIOR TO
   NOCTURNAL STABILIZATION OF THE BOUNDARY LAYER.  OTHERWISE...EXPECT
   LARGE HAIL TO BE THE MAIN SEVERE WEATHER HAZARD.
   
   ELSEWHERE...TSTMS HAVE BECOME WIDESPREAD FROM NEAR AND W OF LBB TO
   NW OF MAF...DUE IN PART TO THE ARRIVAL OF STRONG DEEP-LAYER ASCENT
   ASSOCIATED WITH SHORT WAVE TROUGH LIFTING NNEWD THROUGH ERN NM/WRN
   TX.  THIS LARGE-SCALE FORCING IS BEING AUGMENTED BY MESOSCALE ASCENT
   IN THE LOW-LEVELS ALONG/E OF COMPOSITE OUTFLOW BOUNDARY SURGING WWD
   TOWARD THE TX/NM BORDER.  IN ADDITION TO SEVERE HAIL...EXCESSIVE
   RAINFALL WILL BECOME INCREASINGLY PROBLEMATIC OWING TO ECHO TRAINING
   AND/OR BACKBUILDING STORM DEVELOPMENT.
   
   ..MEAD.. 04/17/2009
   
   
   ATTN...WFO...OUN...SJT...LUB...AMA...MAF...
   
   LAT...LON   32150314 33000314 33020270 34870275 34879985 32899991
               32770009 31890006 31650021 31360046 31000061 30970259
               31160287 32150314