MESO: Mesoscale Discussion 0495

ACUS11 KWNS 202247
SWOMCD
SPC MCD 202247
TXZ000-202345-

MESOSCALE DISCUSSION 0495
NWS STORM PREDICTION CENTER NORMAN OK
0547 PM CDT WED APR 20 2011

AREAS AFFECTED...CNTRL TX

CONCERNING...SEVERE THUNDERSTORM WATCH 171...

VALID 202247Z - 202345Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 171
CONTINUES.

ONGOING CLUSTER OF THUNDERSTORMS ACROSS CNTRL TX CONTINUES TO
DISPLAY THE POTENTIAL FOR PRODUCING LARGE HAIL AND DAMAGING WIND
GUSTS...AND PERHAPS AN ISOLATED TORNADO. MIDLEVEL ROTATION HAS BEEN
OBSERVED IN MANY OF THESE STORMS...WITH SEVERAL LEFT SPLITTING
STORMS PROGRESSING NWD INTO A MORE STABLE ENVIRONMENT...EVIDENT IN
WEAKENING RADAR REFLECTIVITY TRENDS WITH STORMS OVER COLEMAN/TOM
GREEN COUNTIES OVER THE PAST 1-2 HRS. LATEST SFC SUBJECTIVE ANALYSIS
PLACES A WEAK SFC LOW JUST W OF JCT...WITH EFFECTIVE FRONT SLOWLY
SHIFTING SWD...REINFORCED BY THUNDERSTORM OUTFLOW. LOW-LEVEL
CONVERGENCE WILL CONTINUE TO BE MAXIMIZED IN THE VICINITY OF THE SFC
LOW AND ALONG THE COLD FRONT...WHICH SHOULD FOCUS ADDITIONAL
THUNDERSTORM DEVELOPMENT...WHILE THUNDERSTORMS N OF THE FRONT REMAIN
DRIVEN MAINLY BY BOUNDARY INTERACTIONS. THE THREAT FOR LARGE HAIL
AND DAMAGING WINDS WILL LIKELY CONTINUE INTO THIS EVENING...THOUGH
THUNDERSTORM ACTIVITY SHOULD DIMINISH WITH TIME WITH THE ONSET OF
DIABATIC COOLING.

FARTHER E...WEAK LOW-LEVEL CONVERGENCE ALONG THE NEARLY STATIONARY
FRONT HAS FAILED TO INITIATE CONVECTION...UNABLE TO OVERCOME WEAK
CINH AS THUNDERSTORM ANVILS HAVE SPREAD OVERHEAD. WITH THE LOSS OF
DIABATIC HEATING...IT APPEARS THAT THE POTENTIAL FOR ANY
THUNDERSTORM DEVELOPMENT WILL REMAIN LOW INTO THE LATE EVENING.

..ROGERS.. 04/20/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FWD...EWX...SJT...MAF...

LAT...LON 29400172 31140173 31979805 30259803 29400172

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