DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191234
SWODY1
SPC AC 191231

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0631 AM CST WED DEC 19 2012

VALID 191300Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS MO TO ARKLATEX AND MS
DELTA REGIONS...

...SYNOPSIS...
PROGRESSIVE UPPER-AIR PATTERN WILL FEATURE PROMINENT SHORTWAVE
TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER PORTIONS
UT/AZ. THIS SYSTEM IS FCST TO MOVE EWD TO CENTRAL/SRN HIGH PLAINS
AROUND 00Z...THEN REACH NRN/WRN MO...ERN OK AND N-CENTRAL TX BY END
OF PERIOD.

RELATED AREA OF SFC LOW PRESSURE NOW OVER SERN CO WILL DEEPEN
CONSIDERABLY OVER NEXT FEW HOURS. THEN...AS HEIGHT FALLS AND
LARGE-SCALE ASCENT PRECEDING MID-UPPER TROUGH SPREAD ACROSS
CENTRAL/SRN PLAINS...LOW WILL SHIFT EWD...BRACKETED BY FRONTOGENESIS
TO ITS S AND NE. BY 00Z...STRENGTHENING SFC CYCLONE SHOULD BE
CENTERED OVER AVK/P28 AREA...WITH COLD FRONT SWD ACROSS WRN OK AND
W-CENTRAL TX...THEN SWWD OVER COAHUILA. WARM FRONT AT THAT TIME
SHOULD EXTEND ENEWD OVER SERN KS AND EWD ACROSS SRN MO. LOW SHOULD
MOVE NEWD TO WRN IL BY 12Z...WITH COLD FRONT SWD OVER SERN
MO...AR/MS BORDER REGION AND CENTRAL/ERN LA COAST.

...MO TO ARKLATEX AND MS DELTA REGIONS...
BAND OF LOW-TOPPED CONVECTION WITH AT LEAST ISOLATED TO WIDELY
SCATTERED EMBEDDED TSTMS IS FCST TO DEVELOP INVOF SFC COLD FRONT
AFTER DARK BETWEEN SRN MO AND E TX. ACTIVITY WILL SHIFT EWD ACROSS
LA/AR...PORTIONS WRN TN AND NRN/WRN MS BY END OF PERIOD. MAIN
THREAT IS DAMAGING WIND. DESPITE APPARENT DOMINANCE OF LINEAR
FORCING...STG LOW-LEVEL SHEAR AND LARGE HODOGRAPHS ARE EXPECTED OVER
NARROW CORRIDOR OF SFC-BASED WARM-SECTOR INFLOW IMMEDIATELY
PRECEDING FROPA. AS SUCH...SPORADIC TORNADO THREAT EXISTS...WHETHER
WITH SUPERCELLULAR STRUCTURES OR QLCS CIRCULATIONS.

FCST SOUNDINGS SUGGEST WEAKER LAPSE RATES ALOFT WITH SWD
EXTENT...OFFSET JUST ENOUGH BY INCREASING MOISTURE TO MAINTAIN
NARROW BELT OF 300-700 J/KG MLCAPE...AMIDST 250-400 J/KG EFFECTIVE
SRH AND 40-50 KT EFFECTIVE SHEAR MAGNITUDE. PRIMARY LIMITING FACTOR
WITH THIS SYSTEM REMAINS WEAKNESS OF LOW-LEVEL MOISTURE RETURN AND
RELATED MARGINALITY OF THETAE WHERE FRONTAL AND SYNOPTIC-SCALE LIFT
WILL BE GREATEST...ACROSS PORTIONS MO/AR. HOWEVER...GIVEN STRENGTH
OF DEEP-LAYER WIND FIELDS OVER BROAD AREA...MAINTENANCE OF MOST OF
PREVIOUS OUTLOOK AREA APPEARS WARRANTED ATTM.

GIVEN ITS SLGT POSITIVE TILT...STRONGEST MIDLEVEL DCVA PRECEDING
TROUGH ALOFT WILL REMAIN BEHIND SFC COLD FRONT...EXCEPT INVOF SFC
LOW AND PERHAPS ACROSS PORTIONS SWRN/S-CENTRAL MO. VERY NARROW
JUXTAPOSITION OF MOST FAVORABLE LARGE-SCALE ASCENT/COOLING ALOFT
WITH NWRN FRINGE OF WARM SECTOR MAY BE BARELY ADEQUATE FOR 100-300
J/KG MLCAPE...WITH SFC-BASED/NEUTRALLY STABLE EFFECTIVE INFLOW
PARCELS FRONTALLY FORCED INTO CONVECTIVE PLUME. UNCERTAINTY
REGARDING UNCONDITIONAL WIND THREAT INCREASES WITH NWD EXTENT FROM
OZARKS AS THETAE DECREASES.

..EDWARDS/ROGERS.. 12/19/2012

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