Mesoscale Discussion 653, Regarding WW 204

MESOSCALE DISCUSSION 0653
NWS STORM PREDICTION CENTER NORMAN OK
05:49 PM CDT THU APR 17 2008
AREAS AFFECTED...PARTS OF CENTRAL/ERN OK SWD THROUGH NRN AND CENTRAL
TX
CONCERNING...SEVERE THUNDERSTORM WATCH
204
...
VALID 172249Z - 172345Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 204
CONTINUES.
PARTS OF CENTRAL TX TO THE S OF WW 204 ARE BEING MONITORED FOR AN
ADDITIONAL WW.
LATE AFTERNOON SURFACE ANALYSIS/REGIONAL RADAR DATA SHOWED A BROKEN
LINE OF TSTMS LOCATED ALONG AN EWD MOVING COLD FRONT WITH MORE
ROBUST ACTIVITY OVER WRN N TX EXTENDING NNEWD INTO CENTRAL OK. TSTM
ACTIVITY OVER WRN N TX INTO FAR SRN OK HAS BEEN MORE SUPERCELLULAR
GIVEN DEEP LAYER SHEAR VECTORS CROSSING THE COLD FRONT AT A GREATER
ANGLE THAN FARTHER N INTO CENTRAL OK WHERE ACTIVITY IS MORE LINEAR
IN STRUCTURE WITH SHEAR VECTORS MORE PARALLEL TO THE BOUNDARY.
GREATER INSTABILITY /MLCAPE AROUND 1000 J/KG/ OVER CENTRAL AND NRN
TX COMBINED WITH EFFECTIVE BULK SHEAR OF 50+ KT WILL SUPPORT
ADDITIONAL SUPERCELLS WITH ATTENDANT THREAT FOR LARGE HAIL AND
STRONG WIND GUSTS. STEEP LOW LEVEL LAPSE RATES WILL FAVOR AN
ENHANCED WIND THREAT...AND MAY TEND TO LIMIT THE TORNADO THREAT
DESPITE THE DEVELOPMENT OF ROTATIONAL COUPLETS WITH THE SUPERCELLS.
FARTHER S INTO PARTS OF CENTRAL/SOUTH CENTRAL TX...VISIBLE IMAGERY
SHOWED A LINE OF CU CONTINUING TO DEVELOP SWWD ALONG THE DRY LINE
TOWARD THE TX BIG BEND REGION. MLCAPE VALUES E OF THIS BOUNDARY ARE
RANGING FROM 500-1000 J/KG. AIR MASS ALONG THE DRY LINE IS DEEPLY
MIXED WITH STEEP LAPSE RATES WHERE SURFACE HEATING HAS BEEN
STRONGER. DAMAGING WINDS MAY BE THE INITIAL THREAT...WITH THE
POTENTIAL FOR STORMS TO BECOME MORE ROBUST AS THEY INGEST A MORE
MOIST AND UNSTABLE AIR MASS LOCATED ACROSS CENTRAL/SOUTH CENTRAL TX.
FORCING FOR ASCENT WITH SRN EXTENT OF UPPER TROUGH WILL CONTINUE TO
SPREAD EWD AND SHOULD SUPPORT TSTM DEVELOPMENT WITH SWD EXTENT THIS
EVENING ALONG THE DRY LINE AND AS COLD FRONT MERGES WITH THE DRY
LINE.
PETERS.. 04/17/2008