SWODY2
SPC AC 181730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CST SUN DEC 18 2011
VALID 191200Z - 201200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS CENTRAL/SOUTHEAST TX TO
FAR WESTERN LA...
...SYNOPSIS...
WHILE THE PRIMARY WESTERLIES PERSIST OVER CANADA/CONUS NORTHERN
TIER...THE CLOSED/SLOW-MOVING UPPER LOW CURRENTLY CENTERED OVER
NORTHERN BAJA/FAR NORTHWEST MEXICO WILL BEGIN TO MODESTLY ACCELERATE
EAST-NORTHEASTWARD AS IT REACHES THE SOUTHERN PLAINS BY MONDAY
AFTERNOON/NIGHT.
...CENTRAL/EAST TX TO WESTERN LA...
AS THE AFOREMENTIONED UPPER LOW EMERGES FROM NORTHWEST MEXICO/DESERT
SOUTHWEST...A PERSISTENTLY STRONG 50-60 KT SOUTHERLY LOW LEVEL JET
WILL AID IN THE NORTHWARD TRANSPORT OF A PARTIALLY MODIFIED GULF
AIRMASS INTO THE SOUTHERN PLAINS ON MONDAY. EAST OF A GRADUALLY
DEEPENING SOUTHERN HIGH PLAINS SURFACE LOW AND A
DRYLINE/EASTWARD-MOVING PACIFIC FRONT...THIS WILL GENERALLY RESULT
IN SURFACE DEWPOINTS IN THE LOWER TO MIDDLE 60S ACROSS
CENTRAL/SOUTHEAST TX BY AFTERNOON...WITH MIDDLE TO UPPER 50S F
DEWPOINTS INTO NORTH-CENTRAL TX/FAR SOUTHERN OK.
WITH SHOWERS/TSTMS LIKELY TO BE ONGOING EARLY MONDAY ACROSS WEST TX
INTO PARTS OF NORTH/CENTRAL TX AND OK...WIDESPREAD LOW CLOUDS MAY
LIMIT APPRECIABLE DESTABILIZATION INTO EARLY AFTERNOON.
NONETHELESS...CONTINUED THETA-E ADVECTION AND DIURNAL HEATING/MIXING
SHOULD YIELD A WEAKLY CAPPED BOUNDARY LAYER WITH A CORRIDOR OF
MLCAPE OF 500-800 J/KG ACROSS CENTRAL/SOUTHEAST TX BY MID/LATE
AFTERNOON TO THE EAST OF THE DRYLINE/PACIFIC FRONT. ALONG WITH
ARRIVAL OF MORE APPRECIABLE FORCING FOR ASCENT...THIS SHOULD RESULT
IN AN AFTERNOON/EVENING INCREASE OF SURFACE BASED TSTMS.
GIVEN THE DEGREE OF FORCING...EXPECTED EASTWARD PROGRESSION OF THE
PACIFIC FRONT ACROSS TX...AND CURRENTLY FORECAST VEER-BACK-VEER LOW
TO MID-LEVEL WIND PROFILES...THE PRIMARY CONVECTIVE MODE IS EXPECTED
TO BE LINEAR ESPECIALLY ACROSS CENTRAL INTO NORTH TX.
NONETHELESS...ASIDE FROM DAMAGING WINDS...AT LEAST SOME TORNADO
THREAT WILL EXIST GIVEN THE DEGREE OF LOW LEVEL SHEAR/SRH. SUCH A
TORNADO THREAT COULD BE THE CASE WITH INITIAL WARM SECTOR STORMS
EAST OF THE PACIFIC FRONT...ANY QLCS-EMBEDDED CIRCULATIONS THAT
EVOLVE...AND/OR WITH QLCS-SOUTH PERIPHERAL STORMS THAT SHOULD BE OF
A MORE DISCRETE NATURE /FORCING FOR ASCENT WILL BE A BIT MORE
SUBTLE/ WITHIN A HIGHER MOISTURE CONTENT AIRMASS ACROSS SOUTHEAST
TX. AT LEAST AN ISOLATED/MARGINAL DAMAGING WIND/TORNADO THREAT
SHOULD CONTINUE THROUGH MONDAY NIGHT AND INTO EARLY TUESDAY ACROSS
SOUTHEAST/EAST TX INTO WESTERN/SOUTHWEST LA.
...NORTHWEST TX/SOUTHWEST OK...
EVEN WITH A COOL/MARGINALLY MOIST BOUNDARY LAYER...LOW-TOPPED TSTMS
CAPABLE OF HAIL TO AROUND SEVERE LEVELS AND/OR PERHAPS A TORNADO
COULD DEVELOP EARLY/MID AFTERNOON MONDAY IN CLOSE PROXIMITY TO THE
NEARLY STACKED SOUTHERN HIGH PLAINS CYCLONE. SHOULD
MODEST/SUFFICIENT HEATING OCCUR...THIS COULD INITIALLY BE THE CASE
ACROSS NORTHWEST TX INCLUDING THE TX SOUTH PLAINS/SOUTHERN TX
PANHANDLE VICINITIES. GIVEN THE LIMITED NATURE OF THE
MOISTURE/BUOYANCY AND EXPECTED COLD FRONTAL PROGRESSIONS...ANY
STRONG/SEVERE TSTM THREAT SHOULD REMAIN MARGINAL AND OF A RELATIVELY
LIMITED DURATION.
..GUYER.. 12/18/2011
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