DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 181242
SWODY1
SPC AC 181240

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0740 AM CDT FRI OCT 18 2013

VALID 181300Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON/EVENING FOR
PARTS OF THE TX BIG COUNTRY AND EDWARDS PLATEAU...

...TX AREA THROUGH TONIGHT...
AS PART OF A LARGE-SCALE TROUGH OVER MUCH OF NORTH AMERICA...AN
EMBEDDED SHORTWAVE TROUGH OVER CO THIS MORNING WILL PROGRESS TO
KS/OK BY THIS EVENING...AND REACH THE MS VALLEY BY SATURDAY MORNING.
AN ASSOCIATED REINFORCING COLD FRONTAL SURGE WILL MOVE SEWD FROM OK
TO CENTRAL TX BY EARLY TONIGHT...AND TO THE TX COAST BY THE END OF
THE PERIOD. THE COLD FRONT WILL ENCOUNTER A NARROW CORRIDOR OF
RETURN FLOW MOISTURE...WITH PW VALUES AOA 1 INCH AND BOUNDARY LAYER
DEWPOINTS NEAR 60...BY LATE AFTERNOON/EVENING ACROSS THE BIG
COUNTRY/EDWARDS PLATEAU IN TX. THUNDERSTORM DEVELOPMENT WILL BECOME
MORE PROBABLE NEAR OR AFTER 21Z AS SURFACE HEATING IN CLOUD BREAKS
REDUCES CONVECTIVE INHIBITION...AND THE SRN FRINGE OF THE
LARGER-SCALE FORCING FOR ASCENT COINCIDES WITH THE LOW-LEVEL LIFT
ALONG THE SURFACE COLD FRONT.

MLCAPE IS EXPECTED TO INCREASE TO 1000-1500 J/KG WITHIN THE MOISTURE
CORRIDOR BY 21Z...WHERE RELATIVELY STRAIGHT HODOGRAPHS AND SPEED
INCREASES ALOFT WILL CONTRIBUTE TO EFFECTIVE BULK SHEAR OF 40-50 KT.
THESE FACTORS WILL BE SUFFICIENT FOR ORGANIZED LINE SEGMENTS AND
SOME EMBEDDED SUPERCELL STRUCTURES WITH THE INITIAL STORM
DEVELOPMENT THIS EVENING...WHEN THE RISK FOR ISOLATED LARGE HAIL
WILL BE GREATEST. THEREAFTER...THE THREAT WILL BE LIMITED PRIMARILY
TO ISOLATED DAMAGING WINDS WITH CONVECTION THAT ENDS UP BEING
SLIGHTLY UNDERCUT BY THE SURFACE COLD FRONT...WITH THE SEVERE THREAT
DIMINISHING BY 03-06Z IN CENTRAL TX. OTHERWISE...A FEW WEAKLY
ROTATING STORMS WILL BE POSSIBLE NEAR THE MIDDLE AND LOWER TX COAST
TODAY...ALONG A WEAK SURFACE COASTAL TROUGH AND IN ASSOCIATION WITH
A WEAK LEAD SHORTWAVE TROUGH EJECTING ENEWD FROM NE MEXICO THIS
MORNING.

..THOMPSON/GARNER.. 10/18/2013

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