DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 211959
SWODY1
SPC AC 211957

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CDT THU MAR 21 2013

VALID 212000Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER NWRN TX AND EXTREME SRN
OK...

...TX/OK...
AS EXPECTED...EARLY AFTERNOON SURFACE ANALYSES INDICATED A
SUB-1000MB LOW DEEPENING ACROSS THE TX PANHANDLE WITH A STRONG WARM
FRONT EXTENDING ESEWD THROUGH SWRN OK TO E TX. TRENDS IN VISIBLE
SATELLITE IMAGERY SHOWED CU TRYING TO DEVELOP AND BECOME SUSTAINED
IN NW TX /INVOF AND S FROM WILBARGER COUNTY TX/...WHICH IS NEAR THE
INTERSECTION OF THE WARM FRONT/DRY LINE. ASIDE FROM THESE
OBSERVATIONS AND GRADUAL DESTABILIZATION...THE FORECAST FOR THIS
REGION REMAINS ON TRACK AND NO CHANGES ARE NEEDED WITH THIS OUTLOOK
ISSUANCE.

..PETERS.. 03/21/2013

.PREV DISCUSSION... /ISSUED 1121 AM CDT THU MAR 21 2013/

...SYNOPSIS...
LARGE SCALE PATTERN FEATURES AN EXTENSIVE POLAR VORTEX ACROSS GREAT
LAKES/NORTHEAST AND ERN CANADA WITH RELATIVELY WEAKER RIDGING ACROSS
THE CENTRAL U.S. AND A SERIES OF SHORTWAVE IMPULSES SPREADING ACROSS
THE WRN U.S. EMBEDDED WITHIN CONFLUENT/SPLIT FLOW. DISTURBANCES
WITHIN AN ACTIVE ZONAL SRN STREAM JET WILL CONTINUE TO UNDERCUT THE
MID-LEVEL RIDGE CENTERED ACROSS THE PLAINS AND SUPPORT THE
DEVELOPMENT OF A WEAK FRONTAL WAVE CYCLONE THAT WILL TRACK FROM NWRN
TX TO THE ARKLATEX THROUGH EARLY FRIDAY.

...TX/OK...
LATE AFTERNOON SURFACE MAP SHOULD FEATURE A SUB-1000MB DEEPENING
SURFACE LOW ACROSS THE TX PNHDL AND A WARM FRONT EXTENDING SEWD
ALONG THE RED RIVER. SHARPENING DRYLINE SHOULD MIX EWD COINCIDENT
WITH THE SURFACE LOW CONSOLIDATING AND RIPPLING EAST ALONG THE WARM
FRONT FROM CDS TO NEAR SPS BY EVENING. LARGE SCALE AND MESOSCALE
DYNAMICS AND DIURNALLY STEEP LAPSE RATES APPEAR TO COME TOGETHER AND
CONTRIBUTE TO SURFACE-BASED...AND LIKELY ISOLATED...CONVECTIVE
INITIATION NEAR THE TRIPLE-POINT LOW IN THE 21-00Z TIME FRAME.
ASCENT...MOISTENING...AND CONVECTION WILL INCREASE FROM LATE EVENING
THROUGH OVERNIGHT NORTH OF THE SURFACE LOW AND WARM FRONT...FROM ERN
OK TO THE ARKLATEX.

WHILE THE POTENTIAL FOR MARGINALLY SEVERE HAIL WILL PERSIST THROUGH
THE NIGHT WITH EXPANDING CONVECTION NORTH AND ALONG THE WARM FRONT
FROM ERN OK TO THE ARKLATEX...A SOMEWHAT GREATER SEVERE WEATHER
THREAT IN THE FORM OF DAMAGING WINDS AND LARGE HAIL IS INITIALLY
EXPECTED FROM SURFACE-BASED SUPERCELLS BY LATE AFTERNOON/EARLY
EVENING OVER NRN TX AND THE RED RIVER VALLEY/SRN OK. AS STATED IN
PREVIOUS OTLKS...DESPITE THE PATTERN...TIME OF YEAR...AND SUPPORTIVE
DYNAMICS...THE PRIMARY AND SUBSTANTIAL LIMITING FACTOR FOR MORE
SIGNIFICANT SEVERE WILL BE THE LACK OF GREATER MOISTURE RETURN INTO
ZONE OF CONCENTRATED ASCENT AND STRONG VERTICAL SHEAR THROUGH LATE
AFTERNOON. GIVEN THE CONSISTENCY OF GUIDANCE INDICATING NO MORE THAN
500 J/KG MLCAPE NEAR/AHEAD OF THE TRIPLE-POINT LOW BUT STRONG SHEAR
SUPPORTING UPDRAFT ROTATION AND SUSTENANCE AROUND DIURNALLY
FAVORABLE TIME FOR STORM INITIATION...EXPECT ONE TO A FEW STORMS
CAPABLE OF PRODUCING LARGE HAIL AND STRONG TO DAMAGING WINDS IN THE
HIGHER PROBABILITY/SLGT RISK AREA. SURFACE-BASED CONVECTION WILL
SPREAD EAST BEYOND ITS MORE SUPPORTIVE INITIATION ZONE AND LIKELY
WEAKEN AFTER SUNSET AS WITH THE ONSET OF NOCTURNAL COOLING WHILE
MARGINAL HAIL/GUSTY WIND THREAT PERSISTS WITH MORE ELEVATED STORMS
TO THE NORTH AND EAST.

HAVE REMOVED HIGHER TSTM WIND PROBABILITIES FROM PARTS OF THE NERN
TX PNHDL GIVEN LIMITED SIGNAL IN LATEST GUIDANCE FOR DEEP CONVECTION
IN THIS AREA. WHILE VERY HIGH BASED SCATTERED SHOWERS AND PERHAPS
ISOLATED TSTMS REMAIN POSSIBLE...OVERALL COVERAGE SHOULD REMAIN TOO
LIMITED TO SUPPORT DAMAGING WINDS.

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