MESOSCALE DISCUSSION 0515
   NWS STORM PREDICTION CENTER NORMAN OK
   0143 PM CDT SAT APR 18 2009
   
   AREAS AFFECTED...PORTIONS OF E-CENTRAL/SE TX
   
   CONCERNING...TORNADO WATCH 165...
   
   VALID 181843Z - 182015Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 165 CONTINUES.
   
   HIGH PRECIPITATION SUPERCELL STRUCTURES HAVE BEEN OBSERVED WITH
   STORMS OCCURRING ALONG A LINE FROM 10 S OF HOU TO 50 N OF PSX...WITH
   OCCASIONAL INTENSIFICATION OF LOW LVL ROTATION INDICATED BY KHGX SRV
   DATA. OTHER STORMS /ONE ENTERING POLK COUNTY...AND A SECOND PASSING
   NE OF THE HOUSTON METRO AREA/ HAVE ALSO DISPLAYED STRENGTHENING LOW
   LVL ROTATIONAL SIGNATURES. RUC/SFCOA GUIDANCE SUGGESTS THESE STORMS
   ARE OCCURRING WITHIN A ZONE OF STRONG LOW LVL WAA...WHICH IS
   SUPPORTED BY RECENT SURFACE PRESSURE FALLS /2-4 MB PER 2 HRS/ OVER
   THE REGION. GIVEN THE FAVORABLE ASCENT /WHICH IS FORECAST TO
   GRADUALLY SHIFT TOWARD THE TX-LA BORDER THROUGH MID AFTERNOON/ AND
   VERY MOIST LOW LVL INFLOW...STORMS SHOULD CONTINUE TO MAINTAIN
   STRENGTH AS THEY MOVE ENE AT AROUND 20-25 KT.
   
   MODIFIED RUC SOUNDINGS INVOF OF HOU INDICATE MLCAPE VALUES RESIDING
   AROUND 1000 J/KG AND MLLCL HEIGHTS NEAR 500 M. IN ADDITION...AREA
   VWP DATA DISPLAYS LARGE LOW LVL HODOGRAPH STRUCTURE...WITH 0-1 KM
   SHEAR AOA 35 KT AND 0-1 KM SRH NEAR 500 M2/S2. THIS ENVIRONMENT WILL
   CONTINUE TO SUPPORT STORMS PRODUCING STRONG LOW LVL ROTATION WITH A
   THREAT OF TORNADOES.
   
   ..GARNER.. 04/18/2009
   
   
   ATTN...WFO...LCH...SHV...HGX...CRP...
   
   LAT...LON   28589666 29969639 30679530 31799506 32029468 31919424
               30489447 29139474 28599503 28499582 28509632 28589666