National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
ACUS11 KWNS 212254
SWOMCD
SPC MCD 212254
LAZ000-ARZ000-TXZ000-220000-

MESOSCALE DISCUSSION 0760
NWS STORM PREDICTION CENTER NORMAN OK
0554 PM CDT TUE MAY 21 2013

AREAS AFFECTED...PARTS OF SRN AR / NWRN LA / NERN TX

CONCERNING...TORNADO WATCH 201...205...

VALID 212254Z - 220000Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 201...205...CONTINUES.

SUMMARY...ISOLD DAMAGING WINDS WILL BE THE PREDOMINATE THREAT THIS
EVENING OVER THE ARKLATEX REGION.  LINEAR CONVECTIVE MODE IS
CONSIDERABLY LIMITING THE TORNADO THREAT.

DISCUSSION...22Z SURFACE ANALYSIS PLACES AN ARCING OUTFLOW BOUNDARY
FROM THE LOWER MS VALLEY SQUALL LINE WWD NEAR THE AR/LA BORDER AND
INTERSECTING THE GUST FRONT OVER NERN TX FROM THE TX/AR QLCS.  THE
AREA N OF THE OUTFLOW BOUNDARY HAS STABILIZED APPRECIABLY AT THE
SURFACE BUT IS STILL SUPPORTIVE OF STRONGER GUSTS PENETRATING THE
SURFACE...ESPECIALLY IN CLOSER PROXIMITY TO THE OUTFLOW BOUNDARY
WHERE THE COLD POOL DEPTH IS MORE SHALLOW.  A RECENTLY MEASURED 44
KT ASOS GUST AT KTXK ILLUSTRATES THIS WELL.

FARTHER SOUTH...THE QLCS CHARACTERISTICS OVER NERN TX SHOW A LOOSELY
ORGANIZED STRUCTURE BUT THE GUST FRONT HAS SURGED WELL AHEAD OF THE
DEEPER UPDRAFTS LOCATED WITHIN THE MAIN CONVECTIVE BAND.  AS
SUCH...EXPECTING THE TORNADO RISK NEAR THE QLCS-OUTFLOW BOUNDARY
INTERSECTION TO REMAIN QUITE LOW UNLESS DEEPER UPDRAFTS CAN BETTER
PHASE WITH THE LEADING EDGE OF THE COLD POOL AND STRETCH/AUGMENT LOW
LEVEL VORTICITY NEAR THIS BOUNDARY.  THE AREA AHEAD OF THE QLCS OVER
E-CNTRL TX EWD INTO NWRN LA LIKELY POSES THE GREATEST POTENTIAL FOR
ISOLD STRAIGHT-LINE WIND DAMAGE GIVEN THE UNDISTURBED MOIST/UNSTABLE
BOUNDARY LAYER.

..SMITH.. 05/21/2013

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

ATTN...WFO...LZK...SHV...FWD...

LAT...LON   33989377 33739233 32589216 32039287 31629474 31589588
            31859638 32669580 33989377