MESO: Mesoscale Discussion 0575

ACUS11 KWNS 281827
SWOMCD
SPC MCD 281827
TXZ000-282000-

MESOSCALE DISCUSSION 0575
NWS STORM PREDICTION CENTER NORMAN OK
0127 PM CDT SUN APR 28 2013

AREAS AFFECTED...BIG BEND AREA NNEWD INTO W-CNTRL TX

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 281827Z - 282000Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...HIGH BASED THUNDERSTORM CLUSTERS ARE FORECAST TO DEVELOP
THIS AFTERNOON FROM THE BIG BEND AREA NNEWD INTO W-CNTRL TX.
ISOLATED STRONG/SEVERE DOWNBURSTS WILL BE POSSIBLE. THREAT IS
EXPECTED TO BE TOO MARGINAL FOR A WW.

DISCUSSION...TRENDS IN SURFACE OBSERVATIONS SHOW DEWPOINTS HAVE
RISEN INTO THE 50S ACROSS W TX DUE TO A COMBINATION OF SLY RETURN
FLOW W OF A SURFACE HIGH CENTERED OVER NERN TX/SWRN AR...AND
DOWNWARD MIXING OF GREATER MOISTURE LOCATED JUST ABOVE THE SURFACE.
HOWEVER...AS TEMPERATURES WARM INTO THE MID/UPPER 80S THIS
AFTERNOON...DEWPOINTS ARE FORECAST TO MIX BACK DOWN INTO THE 30S AND
40S. DESPITE THE DECREASE IN DEWPOINTS WITH TIME...MLCAPE VALUES
WILL REMAIN NEAR 500 J/KG DUE TO THE PRESENCE OF VERY STEEP MIDLEVEL
LAPSE RATES. LOW-LEVEL FOCUS FOR THUNDERSTORM INITIATION IS NOT
CLEAR ATTM...WITH THE EXCEPTION OF OROGRAPHIC FORCING FOR ASCENT
OVER THE MOUNTAINOUS TERRAIN IN THE TX TRANS-PECOS.
NEVERTHELESS...STRONG BOUNDARY LAYER DESTABILIZATION IS STARTING TO
AID IN DEEPENING CUMULUS DEVELOPMENT...AND HI-RES MODEL GUIDANCE
INDICATES THIS WILL LEAD TO A FEW HIGH BASED THUNDERSTORM CLUSTERS
THIS AFTERNOON. DEEPLY MIXED BOUNDARY LAYER PROFILES WILL SUPPORT
ISOLATED DAMAGING DOWNBURST WINDS.

..GARNER/HART.. 04/28/2013

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

ATTN...WFO...SJT...LUB...MAF...

LAT...LON 33300259 34110154 33800017 32589984 29740259 29180296
29110352 29620447 30100464 31570303 33300259

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.