Mesoscale Discussion 571

Issued

Apr 20, 2012, 12:35 PM CDT (17:35 UTC)

Expired

Apr 20, 2012, 3:00 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

The Houston radar (KHGX), 87 km from the middle of the area, began a volume at 17:35 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

• Severe Thunderstorm Watch 184Apr 20, 1:00 PM CDT

052 
ACUS11 KWNS 201735
SWOMCD
SPC MCD 201735 
LAZ000-TXZ000-202000-

MESOSCALE DISCUSSION 0571
NWS STORM PREDICTION CENTER NORMAN OK
1235 PM CDT FRI APR 20 2012

AREAS AFFECTED...PORTIONS MIDDLE-UPPER TX COASTAL PLAIN...WRN LA.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 201735Z - 202000Z

ELEVATED CONVECTION BEARING HAIL RISK HAS INCREASED IN
COVERAGE/INTENSITY OVER PORTIONS E TX AND SHOULD MOVE INTO WRN LA
WITH CONTINUED/SPORADIC RISK OF SVR HAIL.  POTENTIAL IS INCREASING
FOR MORE ORGANIZED/SFC-BASED TSTMS FARTHER SW ACROSS MID-UPPER TX
COASTAL PLAIN...WITH RISK FOR DAMAGING GUSTS AND OCNL LARGE HAIL.

16Z SFC MESOANALYSIS SHOWED SFC COLD FRONT FROM SWRN AR AND NE TX
SWWD ACROSS CENTRAL TX BETWEEN ACT-CLL...JUST S HDO...THEN RIO
GRANDE VALLEY BETWEEN DRT AND EAGLE PASS.  SEPARATE TROUGH/WIND
SHIFT LINE WAS DRAWN FROM SAT AREA SSWWD ACROSS LRD TO NEAR MMMY. 
FRONT SHOULD CONTINUE SEWD...IMPINGING ON BOUNDARY LAYER THAT WILL
BE DESTABILIZING AND WEAKENING CINH WITH TIME.  MOISTURE CHANNEL
IMAGERY AND OVERLAID VWP/PROFILER DATA SHOW WELL-DEFINED SHORTWAVE
TROUGH ACROSS CENTRAL OK...TX HILL COUNTRY AND RIO GRANDE VALLEY
NEAR DRT.  AS RELATED PLUME OF LARGE-SCALE ASCENT SHIFTS ESEWD OVER
DISCUSSION AREA...AND AS POCKETS OF RELATIVELY STG SFC DIABATIC
HEATING CONTINUE...INITIALLY STG CAPPING WILL ERODE RAPIDLY.  THIS
WILL LEAVE BOUNDARY LAYER PRONE TO RAPID DEVELOPMENT AND UPSCALE
GROWTH OF TSTMS...ESPECIALLY ALONG COLD FRONT...BUT PERHAPS INVOF
LOCALIZED SEA-BREEZE CONVERGENCE MAXIMA AS WELL.  RESULTANT
STEEPENING OF LOW-MIDDLE LEVEL LAPSE RATES...JUXTAPOSED WITH SFC DEW
POINTS MAINLY MID-60S F...YIELD MLCAPE 2000-3000 J/KG IN MODIFIED
RAOBS AND RUC FCST SOUNDINGS.  

EFFECTIVE SHEAR IS RATHER WEAK OVER MOST OF DISCUSSION AREA...DUE TO
STG VEERING/BACKING PROFILE IN LOW-MIDDLE LEVELS AND LACK OF MORE
ROBUST BOUNDARY-LAYER WINDS INLAND.  THIS SHOULD REMAIN TRUE OVER
MID-UPPER TX COASTAL PLAIN...THOUGH VERTICAL SHEAR MAY BECOME MORE
FAVORABLE THIS AFTERNOON IN AREA OF DEEP S TX TO BE COVERED IN
SEPARATE MCD LATER.  EFFECTIVE SHEAR ALSO WILL BE STRONGER FOR
CONVECTION BEHIND SFC FRONT.  CLUSTERED AND LINEAR STORM MODES
APPEAR MOST PROBABLE...WITH GREATER WIND THREAT ALONG/AHEAD OF FRONT
AND HAIL RISK WITH CONVECTION ON BOTH SIDES OF FRONT.

..EDWARDS.. 04/20/2012

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

ATTN...WFO...LCH...SHV...HGX...CRP...EWX...

LAT...LON   29019828 29469753 30739596 31289454 31899404 31889283
            30759294 29889367 29329476 28839543 28369638 28069685
            28089723 28309813 28599871 29019828

Mesoscale Discussions in Texas, 2012Mesoscale Discussions in Louisiana, 2012Every mesoscale discussion in 2012

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.