DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 161257
SWODY1
SPC AC 161255

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0655 AM CST SUN DEC 16 2012

VALID 161300Z - 171200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SE TX TO CENTRAL AL...

...SYNOPSIS...
PROGRESSIVE MID-UPPER LEVEL PATTERN FCST THROUGH DAY-1. SERIES OF
SHORTWAVES WILL CONTRIBUTE TO EWD SHIFT OF SYNOPTIC-SCALE TROUGHING
FROM ROCKIES/INTERMOUNTAIN W ACROSS GREAT PLAINS. SHORTWAVE TROUGHS
ARE EVIDENT ATTM IN MOISTURE CHANNEL IMAGERY OVER SERN CO/NERN
NM/NWRN TX PANHANDLE REGION...AND SOMEWHAT WEAKER ONE OVER LOWER
PECOS RIVER REGION OF W TX. EACH WILL EJECT ENEWD TO NEWD AND
WEAKEN TODAY WHILE ESSENTIALLY PHASING. THESE PERTURBATIONS SHOULD
REACH CENTRAL IL AND WRN TN RESPECTIVELY BY 00Z. MEANWHILE...
ANOTHER SHORTWAVE TROUGH CURRENTLY OVER WRN AZ WILL MOVE EWD TO SRN
HIGH PLAINS BY 00Z...THEN ARKLATEX REGION AROUND END OF PERIOD.
PERTURBATION NOW EVIDENT OVER ID IS FCST TO CONTINUE MOVING ESEWD
ACROSS NRN ROCKIES WITH SOME AMPLIFICATION PSBL...REACHING PORTIONS
KS...NEB AND SD BY END OF PERIOD.

AT SFC...RESIDUAL/QUASISTATIONARY FRONTAL ZONE HAS BEEN REINFORCED
ALL NIGHT BY CONVECTION OVER MID TN...NWRN AL...NRN MS...SERN AR AND
NRN LA. BOUNDARY EXTENDS SWWD ACROSS TX COASTAL PLAIN FROM NEAR LFK
TO BETWEEN VCT-SAT...THEN SSWWD BETWEEN MFE-LRD. FARTHER N...WEAK
COLD FRONT FROM IL SWWD ACROSS NRN OK WILL MOVE SLOWLY SEWD
TODAY...BUT SHOULD REMAIN WELL NW OF PRIMARY ZONE OF CONVECTIVE
POTENTIAL ASSOCIATED WITH SRN BOUNDARY. FARTHER S...WARM/MARINE
FRONT OVER LA COASTAL WATERS AND SE TX SHOULD MOVE NEWD/INLAND
THROUGH PERIOD...ACROSS SRN LA/MS/AL/FL PANHANDLE.

...SE TX TO MS/AL...
HEIGHT-GRADIENT ENHANCEMENTS S AND SE OF AFOREMENTIONED SHORTWAVE
TROUGHS WILL CONTRIBUTE TO CORRIDOR OF ENHANCED DEEP-LAYER WINDS AND
SHEAR OVER THIS SWATH THROUGHOUT PERIOD. MEANWHILE...LOW-LEVEL
CONVERGENCE WILL BE MAINTAINED INVOF REMNANT FRONTAL ZONE.
LOW-LEVEL WAA...MOISTURE ADVECTION AND MOISTURE TRANSPORT WILL
OCCURS S OF FRONT...RESULTING IN PROGRESSIVELY MORE NEWD/INLAND
PENETRATION OF HIGH-PW AIR MASS -- 1.5-1.75 INCHES -- NOW APPARENT
OVER NWRN GULF.

IN THIS REGIME...AT LEAST TWO PRIMARY ROUNDS OF CONVECTION WILL POSE
SOME SVR THREAT...MAINLY IN FORM OF DAMAGING GUSTS. TORNADO/HAIL
POTENTIAL IS MORE MRGL/CONDITIONAL OVER MOST OF AREA.

1. ONGOING RISK FROM SE TX ACROSS CENTRAL LA...SHIFTING INTO
PORTIONS WRN/CENTRAL MS DURING DAY. FOR MORE DETAILED/NEAR-TERM
GUIDANCE...REF SPC WW 682 AND ACCOMPANYING MESOSCALE DISCUSSIONS.

2. CONTINUED OR REJUVENATED POTENTIAL OVERNIGHT ACROSS PORTIONS SERN
LA AND SRN MS...EXPANDING/SHIFTING INTO CENTRAL/SRN AL AS LOW-LEVEL
AIR MASS MOISTENS/DESTABILIZES VIA ADVECTIVE PROCESSES. NEARLY
SFC-BASED EFFECTIVE INFLOW PARCELS SHOULD OVERSPREAD PROGRESSIVELY
LARGER PROPORTION OF THIS AREA OVERNIGHT...AS THETAE ADVECTION
OFFSETS DIABATIC SFC COOLING. MID-UPPER LEVEL WIND PROFILES WILL
STRENGTHEN WITH 65-85 KT 500-MB WINDS...AS WELL AS MEAN-WIND AND
DEEP-SHEAR VECTORS...ALIGNED NEARLY PARALLEL TO WSW-ENE ALIGNED
FRONTAL ZONE. SWLY LLJ ALSO IS FCST TO INTENSIFY OVERNIGHT AS IT
SHIFTS EWD ACROSS ERN AL...WITH OUTLOOK AREA ALONG ITS WRN RIM. AS
SUCH...LOW-LEVEL SHEAR SHOULD REMAIN FAVORABLE AFTER 06Z DESPITE
SOME VEERING OF SFC WINDS. RELATIVE MAX IN TORNADO PROBABILITIES
MAY APPEAR OVER PORTIONS ERN MS AND CENTRAL/SRN AL OVERNIGHT BASED
ON RELATED INCREASE IN SIZE OF BOUNDARY-LAYER HODOGRAPHS.

...AFTERNOON/EARLY EVENING...SRN AL AND WRN FL PANHANDLE REGION...
ALTHOUGH MAIN SVR THREAT APPEARS TO BE FARTHER N AND NW...AT LEAST
MRGL POTENTIAL FOR STG/SVR TSTMS MAY EXIST ALONG AND S OF
WARM/MARINE FRONT MOVING INLAND. FCST SOUNDINGS SUGGEST INCREASING
THETAE WITH WARM FROPA...COMBINED WITH SFC DIABATIC HEATING...SHOULD
OFFSET WEAK MID-UPPER LEVEL LAPSE RATES ENOUGH TO YIELD WEAKLY
CAPPED MLCAPE 250-800 J/KG THIS AFTERNOON. SUFFICIENT VEERING WITH
HEIGHT SHOULD EXIST ALONG WARM FRONT AND SWD NEAR AL/WRN FL
PANHANDLE COAST TO SUPPORT CURVED LOW-LEVEL HODOGRAPHS AND AROUND
150-200 J/KG EFFECTIVE SRH...AMIDST 40-50 KT EFFECTIVE SHEAR
MAGNITUDES. AS SUCH...OCNL SUPERCELL STRUCTURES MAY
DEVELOP...SUPPORTING LOBE OF AT LEAST MRGL TORNADO POTENTIAL.

...PORTIONS LOWER OH VALLEY REGION...
NARROW CORRIDOR OF AT LEAST MRGL MUCAPE WILL DEVELOP FROM THIS
AFTERNOON ONWARD ACROSS CORRIDOR FROM WRN TN NEWD OVER PORTIONS OH
RIVER REGION...INITIATED BY AFTERNOON/DIABATIC SFC HEATING THEN
MAINTAINED BY LOW-LEVEL THETAE ADVECTION BETWEEN FRONTAL ZONES.
HEIGHT FALLS AHEAD OF NWRN TROUGH SHOULD IMPINGE ON THIS AIR MASS
MAINLY DURING LATTER HALF OF PERIOD...WITH TSTMS POTENTIAL PRIMARILY
LATE AFTERNOON ONWARD. ISOLATED HAIL NEAR SVR LEVELS IS
POSSIBLE...THOUGH ORGANIZED SVR EVENT APPEARS UNLIKELY ATTM.

..EDWARDS/SMITH.. 12/16/2012

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