ACUS01 KWNS 170554
SWODY1
SPC AC 170552
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1152 PM CST THU FEB 16 2012
VALID 171200Z - 181200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS DEEP S TX....
...SYNOPSIS...
UPPER-AIR PATTERN OVER WRN/CENTRAL CONUS WILL EVOLVE AWAY FROM SPLIT
FLOW THIS PERIOD...AS WELL-DEFINED MID-UPPER CYCLONE NOW OVER NWRN
MEX EJECTS ENEWD. THIS PERTURBATION SHOULD DEAMPLIFY TO STG
OPEN-WAVE TROUGH AROUND 18/00Z-18/06Z TIME FRAME...AS IT MOVES
ACROSS CHIHUAHUA TOWARD SW TX. NRN PORTION OF TROUGH SHOULD CROSS
TX BIG-BEND REGION OVERNIGHT...REACHING NRN COAHUILA/SERRANIAS DEL
BURRO REGION AROUND 18/12Z.
IN RESPONSE...OVERNIGHT/LEE-SIDE SFC CYCLOGENESIS SHOULD OCCUR E OF
MEX MOUNTAINS...WITH DEEPENING LOW CROSSING LOWER RIO GRANDE VALLEY
REGION AND DEEP S TX DURING 18/06Z-18/12Z PERIOD. WARM FRONT --
DENOTING NRN FRINGE OF MARINE BOUNDARY-LAYER AIR MASS -- WILL EXTEND
FROM LOW EWD ACROSS DEEP S TX AND NWRN GULF.
...S TX...
LOW-LEVEL WAA AND MOISTURE ADVECTION SHOULD FOSTER RECOVERY OF
BOUNDARY-LAYER AIR MASS FROM ANY PRIOR OVERNIGHT/MORNING CONVECTION
OVER DEEP S TX. THIS WILL COMBINE WITH SFC DIABATIC HEATING AND 7-8
DEG C/KM MIDLEVEL LAPSE RATES TO BOOST AFTERNOON MLCAPE INTO
1500-2500 J/KG RANGE. PRESENCE OF CAPPING INVERSION AT BASE OF
ELEVATED MIXED LAYER...COMBINED WITH LACK OF APPARENT BOUNDARY-LAYER
FOCI...MAY LIMIT CONVECTIVE POTENTIAL DURING DAYLIGHT HOURS.
STILL...ISOLATED TO WIDELY SCATTERED TSTMS MAY FORM THIS AFTERNOON
ALONG WARM FRONT OR ANY OUTFLOWS FROM EARLIER ACTIVITY...WITH
POTENTIAL FOR STG/DAMAGING GUSTS OR LARGE HAIL ATOP WELL-MIXED
BOUNDARY LAYER. WEAK LOW-LEVEL WINDS WILL LIMIT HODOGRAPH
SIZE...UNTIL AFTER DARK WHEN ISALLOBARIC FORCING ASSOCIATED WITH LEE
CYCLOGENESIS RESULTS IN BACKED/STRENGTHENING LOW-LEVEL FLOW NEAR
WARM FRONT.
MORE ROBUST CONVECTIVE COVERAGE ON BOTH SIDES OF WARM FRONT WILL BE
OVERNIGHT...AS STRONGEST DEEP-LAYER ASCENT AND SFC CYCLONE MOVE
ACROSS AREA. PRIMARY THREATS OVER WARM SECTOR WILL BE DAMAGING
GUSTS AND LARGE HAIL...THOUGH A TORNADO CANNOT BE RULED OUT.
OVERALL SVR RISK SHOULD DIMINISH WITH NWD EXTENT N OF SFC LOW AND
WARM FRONT...WHERE EFFECTIVE INFLOW PARCELS WILL BE PROGRESSIVELY
MORE ELEVATED. STILL...STRENGTHENING MID-UPPER WINDS WITH APCH OF
TROUGH ALOFT WILL BOOST EFFECTIVE SHEAR MAGNITUDES...CONTRIBUTING TO
POTENTIAL FOR ORGANIZED ELEVATED CONVECTION...SOME OF WHICH MAY
OFFER SVR HAILSTONES AND STG GUSTS.
...MID-UPPER TX AND SWRN LA COASTS...
ATTM...CONSENSUS OF SREF AND OPERATIONAL PROGS INDICATES WARM FRONT
WILL REMAIN BARELY OFFSHORE OF THIS COASTAL STRETCH UNTIL EARLY
DAY-2 PERIOD WHEN LOW PASSES. HOWEVER...EVEN MINOR/MESOBETA SCALE
NWD SHIFT IN LOW TRACK COULD RESULT IN SFC-BASED EFFECTIVE
PARCELS...AND ACCOMPANYING WIND/TORNADO RISK...BRUSHING COASTAL
AREAS DURING LAST FEW HOURS OF PERIOD. FOR NOW...THREAT APPEARS TOO
MRGL FOR CATEGORICAL THRESHOLDS OF UNCONDITIONAL SVR PROBABILITIES.
..EDWARDS/DEAN.. 02/17/2012
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