DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 260543
SWODY1
SPC AC 260541

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1141 PM CST SUN NOV 25 2012

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS FOR PARTS OF ERN
TX...NRN/CNTRL/WRN LA...FAR SRN AR...SWRN/W-CNTRL MS...

...SYNOPSIS...
LOW-AMPLITUDE SHORTWAVE TROUGHS WILL BE EMBEDDED WITHIN A BELT OF
ZONAL TO BROADLY CYCLONIC FLOW IN THE MID/UPPER LEVELS E OF THE
ROCKIES. THE COMBINED EFFECTS OF THESE FEATURES WILL BE ASSOCIATED
WITH THE EWD/SWD-MOTION OF A STRONG COLD FRONT THROUGH THE SRN
PLAINS AND LOWER MS VALLEY AT THE LEADING EDGE OF A SPRAWLING
ANTICYCLONE OVER THE CNTRL UNITED STATES. RICH GULF MOISTURE LEADING
THE FRONT WILL ADVANCE NWD INTO SRN/ERN TX EWD INTO THE ARKLAMISS
REGION...AIDED BY THE FLOW AROUND A WEAK SFC CYCLONE TRACKING FROM
N-CNTRL TX TO NRN AL. THE FRONT WILL EXTEND FROM THE DELMARVA TO THE
NW GULF OF MEXICO BY EARLY TUE MORNING.

...CNTRL/SRN/ERN TX EWD TO THE LOWER MS VALLEY THIS AFTERNOON INTO
TONIGHT...
THE RETURN OF RICH LOW-LEVEL MOISTURE IN ADVANCE OF THE COLD FRONT
AMIDST POCKETS OF INSOLATION WILL SUPPORT MLCAPE VALUES OF
500-1200 J/KG WHERE DEWPOINTS CLIMB INTO THE LOWER TO THE MIDDLE
60S. ISOLATED THUNDERSTORMS WILL BE POSSIBLE THROUGHOUT MUCH OF THE
DAY WITHIN THE WARM SECTOR GIVEN THE WEAK LOW-LEVEL WAA REGIME
AMIDST WEAKLY CONFLUENT SFC FLOW. STORM INTENSITY MAY GRADUALLY
INCREASE THROUGH THE AFTERNOON AS INFLOW DESTABILIZES WITH DIURNAL
HEATING. THE RELATIVELY HIGHER POTENTIAL FOR SVR STORMS WILL EXIST
DURING THE LATE AFTERNOON AND ESPECIALLY THE EVENING HOURS...AS ONE
SHORTWAVE TROUGH EMERGES OVER SRN TX AND THE NWRN GULF OF
MEXICO...ANOTHER SHORTWAVE TROUGH APPROACHES THE ARKLATEX
REGION...AND THE FRONT ADVANCES SEWD.

ONLY 20-35 KT OF EFFECTIVE BULK SHEAR ARE ANTICIPATED ACROSS THE
WARM SECTOR GIVEN ITS SWD DISPLACEMENT FROM THE STRONGER MID-LEVEL
FLOW. MULTICELL STORMS AND SHORT LINE SEGMENTS SHOULD BE THE
PREDOMINANT CONVECTIVE MODE...WITH SVR WINDS/HAIL POSSIBLE. LINEAR
FORCING ALONG THE FRONT MAY BE THE FOCUS FOR A MORE ORGANIZED SQUALL
LINE WITH SVR WINDS DURING THE EVENING.

A FEW TRANSIENT SUPERCELL STRUCTURES AND PERHAPS A BRIEF TORNADO
WILL BE POSSIBLE WHERE SFC WINDS REMAIN RELATIVELY BACKED WELL AHEAD
OF THE FRONT...BENEATH A 20-30-KT SWLY LOW-LEVEL JET MAX E/SE OF THE
SFC CYCLONE. THIS CONCERN IS GREATEST ACROSS FAR ERN
TX...NRN/CNTRL/WRN LA...FAR SRN AR...AND SWRN/W-CNTRL MS.
HOWEVER...A WEAKNESS IN THE HODOGRAPH WITHIN THE 2-5.5-KM-AGL LAYER
PER FORECAST SOUNDINGS SHOULD LIMIT THE POTENTIAL FOR PERSISTENT
SUPERCELLS AND THE TORNADO THREAT.

THE SVR THREAT IS EXPECTED TO BE GREATEST DURING THE EVENING ACROSS
PARTS OF ERN TX...NRN/CNTRL/WRN LA...FAR SRN AR...AND SWRN/W-CNTRL
MS...WHERE THE OVERLAP OF MODESTLY ENHANCED MID-LEVEL ASCENT AND
RICH MOISTURE/MODEST BUOYANCY IS ANTICIPATED. FOR LOCATIONS
SURROUNDING THE SLIGHT-RISK AREA...THE SVR THREAT WILL BE LIMITED
/1/ TO THE W BY CAPPING ASSOCIATED WITH A WARM LAYER ALOFT.../2/ TO
THE N/E BY THE LACK OF LOW-LEVEL MOISTURE/BUOYANCY...AND /3/ TO THE
S BY THE ARRIVAL OF THE FRONT LATE IN THE NIGHT WHEN NOCTURNAL
STABILITY WILL BE PRONOUNCED.

..COHEN/GOSS.. 11/26/2012

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