SPC AC 160058
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0658 PM CST FRI FEB 15 2008
VALID 160100Z - 161200Z
...THERE IS A SLGT RISK OF SVR TSTMS LARGE PART OF TX EXCEPT
PANHANDLE...FAR W AND DEEP S PORTIONS...
...SYNOPSIS...
DURING REMAINDER PERIOD...MAIN UPPER AIR FEATURE FOR CONVECTIVE
FORECAST WILL BE MID/UPPER LEVEL LOW -- LOCATED AT 00Z OVER ERN
PORTION AZ/MEX BORDER. THIS LOW WILL PROCEED EWD TOWARD ELP THROUGH
END OF PERIOD. WEAK PRECURSORY PERTURBATION -- NOW EVIDENT IN
MOISTURE CHANNEL IMAGERY FROM TX PANHANDLE SWD ACROSS PERMIAN BASIN
INTO COAHUILA -- WILL LIFT NEWD ACROSS PORTIONS RIO GRANDE VALLEY OF
S TX...AS WELL AS CENTRAL/NW TX AND OK THROUGH 16/09Z.
AT SFC...COMPLEX PATTERN IS EVIDENT WITH ARCTIC FRONT FROM ARKLATEX
REGION SWWD TO BETWEEN AUS-SAT...THEN WWD INTO FRONTAL-WAVE CYCLONE
BETWEEN UVA-DRT. SFC DATA AND REFLECTIVITY ANIMATIONS INDICATE
BOUNDARY ARCS SWD ACROSS MAVERICK COUNTY TX THEN SWWD INTO MEX
MOUNTAINS...RE-EMERGING AGAIN IN DRY AIR OVER CENTRAL OR SRN
PORTIONS BREWSTER/PRESIDIO COUNTIES. THIS FRONT MAY MOVE SWD
SOMEWHAT ACROSS BIG BEND REGION AND MEX...BUT SHOULD BECOME
QUASISTATIONARY OVER MOST OF AREA AS BROADER SCALE CYCLOGENESIS --
NOW EVIDENT IN MEX HIGHLANDS S/SW OF BIG BEND...CONTINUES. DRYLINE
INTERSECTS ARCTIC FRONT ON MEX PIEDMONT W OF EAGLE PASS AND EXTENDS
SWD. SEPARATE BAROCLINIC ZONE -- ASSOCIATED WITH
DIFFERENTIAL/DIURNAL HEATING/MIXING -- IS ANALYZED FROM W-CENTRAL
COAHUILA EWD ACROSS LRD AREA...BECOMING DIFFUSE FARTHER E. THIS
BOUNDARY SHOULD WEAKEN FROM E-W ACROSS RIO GRANDE OVERNIGHT AS
MOISTENING AND SLIGHT DECOUPLING OF BOUNDARY LAYER CONTRIBUTES TO
MORE HOMOGENEOUS VERTICAL AND HORIZONTAL THETAE FIELDS.
MEANWHILE....MARINE FRONT -- ANALYZED INITIALLY FROM ABOUT 75 S LCH
WWD TO BETWEEN GLS-PSX...INTERSECTS ARCTIC FRONT NEAR CLL. THIS
BOUNDARY SHOULD DRIFT NWD THROUGH 12Z.
...S-CENTRAL/SW TX...
THIS PORTION OF OUTLOOK IS CONDITIONAL...SEVERE BEING QUITE LIKELY
IF SFC-BASED STORM INITIATION CAN OCCUR IN NEXT FEW HOURS FROM
SAT/COT AREA WSWWD INTO MEX MOUNTAINS. ANY TSTM THAT CAN MOVE ALONG
OR INTERACT WITH SFC FRONT WOULD POSE GREATEST SVR THREAT.
HOWEVER...GIVEN CONSIDERABLE UNCERTAINTY STILL REMAINING ON
SFC-BASED CONVECTIVE INITIATION...WILL MAINTAIN MRGL
TORNADO/WIND/HAIL PROBABILITIES FOR CATEGORICAL SLGT RISK ATTM.
VERY FAVORABLE DEEP-LAYER SHEAR FOR SUPERCELLS IS EVIDENT IN
MID/UPPER LEVEL WINDS FROM DRT RAOB/VWP DATA...AS WELL AS
INTERPOLATED/MODIFIED RUC SOUNDINGS BETWEEN EAGLE PASS AND
HIGH-ELEVATION/POINT-FORECAST SOUNDING SITE IN CENTRAL COAHUILA.
THIS SHOULD CONTINUE THROUGH REMAINDER EVENING AS BACKED AND
ISALLOBARICALLY STRENGTHENED LOW LEVEL FLOW INVOF FRONTAL ZONE
UNDERLIES TIGHTENING MID/UPPER LEVEL HEIGHT GRADIENTS.
...W TX...S-CENTRAL/SERN NM...
TEMPORARY LULL IN CONVECTIVE POTENTIAL MAY EXIST FOR A FEW HOURS
BEHIND INITIAL/WEAK SHORTWAVE TROUGH. HOWEVER...SELY LLJ WILL
INTENSIFY ACROSS THIS REGION DURING NEXT SEVERAL HOURS...ENHANCING
ELEVATED WAA/MOISTURE TRANSPORT REGIME ALREADY IN PLACE NW OF SFC
FRONT. THIS REGIME WILL BE IMPINGED UPON BY INCREASING
MIDLEVEL/LARGE-SCALE ASCENT AS UPPER LOW APCHS LATE TONIGHT. AS
THIS OCCURS...STEEPENING DEEP-LAYER LAPSE RATES WILL YIELD ELEVATED
MUCAPES 500-1000 J/KG ISENTROPIC ASCENT TO LFC AND STRENGTHENING
MID/UPPER LEVEL WINDS. NET RESULT WILL BE
INITIATION/INTENSIFICATION OF TSTMS ACROSS POTENTIALLY BROAD SWATH
OF W TX BY 12Z....SOME OF WHICH SHOULD PRODUCE LARGE HAIL AMIDST
FAVORABLE DEEP-LAYER THERMODYNAMIC AND SHEAR PROFILES.
...CENTRAL/E TX...SWRN LA...
WIDELY SCATTERED TO SCATTERED TSTMS SLOWLY HAVE BEEN BUILDING IN
OVERALL COVERAGE AND INTENSITY DURING PAST FEW HOURS...CONCENTRATION
BEING GREATEST ALONG AND N OF SFC FRONT FROM NEAR AUS EWD TOWARD
I-45 WHERE LOW LEVEL ASCENT IS MOST FAVORABLE. THIS AREA WILL
REMAIN E OF STRONGEST ELEVATED MIXED-LAYER AIR MASS...WHICH WILL
KEEP MUCINH MINIMIZED BUT WHICH ALSO WILL BE CHARACTERIZED BY
RELATIVELY WEAK LAPSE RATES. FAVORABLE LOW LEVEL MOISTURE -- E.G.
SFC DEW POINTS 68-72 F ALONG AND S OF FRONT AND 850 MB DEW POINTS UP
TO NEAR 13 DEG C -- WILL OFFSET WEAKER LAPSE RATES ALOFT ENOUGH TO
MAINTAIN MUCAPES 1000-1500 J/KG NEAR FRONT...TRENDING DOWNWARD WITH
NWD EXTENT ACROSS E AND N TX. ALONG AND S OF FRONT...CRP RAOB AND
RUC SOUNDINGS INDICATE SFC THETAE WILL REMAIN HIGH ENOUGH FOR
EFFECTIVE LIFTED PARCELS TO BE ROOTED AT OR VERY NEAR SFC THROUGH
MUCH OF TONIGHT...AMIDST FAVORABLE DEEP-LAYER SHEAR PROFILES FOR
SUPERCELLS. THEREFORE SOME POTENTIAL EXISTS FOR HAIL OR DAMAGING
GUSTS FROM ANY SUSTAINED WARM SECTOR TSTMS. EFFECTIVE SHEAR
PROFILES N OF FRONT WILL BE FAVORABLE FOR TSTMS TO ROTATE ALOFT AND
PRODUCE OCCASIONAL HAIL.
..EDWARDS.. 02/16/2008
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