SWODY1
SPC AC 131628
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1128 AM CDT THU MAR 13 2008
VALID 131630Z - 141200Z
..THERE IS A SLGT RISK OF SVR TSTMS LATE TODAY INTO TONIGHT FOR ERN
OK/E TX/AR/LA...
..ERN OK/WRN AR/NE TX AREA THIS AFTERNOON INTO TONIGHT...
A MID LEVEL SHORTWAVE TROUGH IS MOVING EWD OVER W TX/THE PANHANDLE
AND WILL CONTINUE EWD OVER N TX/OK TODAY...REACHING THE LOWER MS AND
TN VALLEYS BY THE END OF THE PERIOD. AN ASSOCIATED SURFACE CYCLONE
WILL MOVE GENERALLY EWD ACROSS CENTRAL OK THIS AFTERNOON TO NRN
AR/SRN MO OVERNIGHT. S OF THE SURFACE LOW...A DRYLINE WILL
CONSOLIDATE ACROSS CENTRAL TX THIS AFTERNOON...BUT THIS BOUNDARY
SHOULD MOVE ONLY SLOWLY EWD TONIGHT.
LOW-LEVEL MOISTURE RETURN IS UNDERWAY FROM THE WRN GULF OF MEXICO TO
THE SRN AND ERN TX. THE MAGNITUDE OF THE BOUNDARY LAYER DEWPOINTS
SHOULD BE LIMITED TO THE LOW-MID 60S NEAR THE COAST AND 55-60 F
INLAND ACROSS CENTRAL/E TX INTO SE OK THIS AFTERNOON...WHILE THE
MARINE BOUNDARY LAYER CONTINUES TO MODIFY IN THE WAKE OF A PRIOR
FRONTAL INTRUSION. OF GREATER CONCERN IS THE RELATIVELY WARM
ELEVATED MIXED LAYER OVER TX/OK DEPICTED BY 12Z SOUNDINGS. SURFACE
TEMPERATURES WILL NEED TO WARM INTO THE RANGE OF 82-86 F TO MINIMIZE
CONVECTIVE INHIBITION THIS AFTERNOON ALONG THE DEVELOPING
DRYLINE...GIVEN THE MODEST BOUNDARY LAYER MOISTURE. IT APPEARS THE
MORE PROBABLE AREA FOR CONVECTIVE INITIATION LATE THIS
AFTERNOON/EVENING WILL BE CLOSER TO THE SURFACE LOW ACROSS ERN
OK...IN THE REGION OF SUSTAINED ASCENT AND A COOLER ELEVATED MIXED
LAYER COMPARED TO AREAS FARTHER S IN TX.
VERTICAL SHEAR WILL BE SUFFICIENT FOR SUPERCELLS ACROSS THE WARM
SECTOR...WITH SOMEWHAT WEAKER DEEP LAYER SHEAR N OF THE MID-UPPER
JET CORE /NEAR AND N OF I-40/. THE COMBINATION OF MLCAPE AOA 1500
J/KG...0-6 KM BULK SHEAR OF 40-50 KT...MID LEVEL LAPSE RATES GREATER
THAN 8 C/KM...AND RELATIVELY COLD MID LEVEL TEMPERATURES WILL FAVOR
LARGE HAIL PRODUCTION. THE TORNADO THREAT IS MORE UNCERTAIN.
STILL...ANY PERSISTENT SUPERCELLS WILL HAVE SOME TORNADO POTENTIAL
GIVEN 0-1 KM SRH OF 150-250 M2/S2 AND REASONABLY LOW LCL HEIGHTS
THIS EVENING.
..SE TX THIS AFTERNOON INTO SRN LA TONIGHT...
THE MAJORITY OF SHORT TERM MODEL FORECASTS SHOW A CLUSTER CONVECTION
FORMING OVER SE TX BY LATE AFTERNOON...AND THE CONVECTION IS
FORECAST TO SPREAD EWD OVER SRN LA TONIGHT. THIS MODEL SIGNAL
APPEARS TO BE RELATED TO MOISTENING NEAR AND ABOVE THE SURFACE...IN
ADVANCE OF A WEAK LEAD SHORTWAVE TROUGH EJECTING NEWD FROM NE
MEXICO. THERE WILL BE SOME THREAT FOR SURFACE-BASED STORMS ACROSS
SE TX LATE THIS AFTERNOON IN PROXIMITY TO THE AXIS OF RETURN FLOW
MOISTURE AND JUST E OF THE WARMEST ELEVATED MIXED LAYER PLUME.
HOWEVER...THE MAJORITY OF THE CONVECTION OVERNIGHT WILL LIKELY
REMAIN ELEVATED...ESPECIALLY TONIGHT OVER LA AS THE LOW LEVELS MAY
BE SLOW TO RECOVER GIVEN THE INITIAL CONDITIONS AND THE ONSET OF
PRECIPITATION PRIOR TO INLAND RETURN OF THE MORE MODIFIED MARINE
BOUNDARY LAYER. LARGE HAIL SHOULD BE THE PRIMARY SEVERE THREAT.
.THOMPSON/JEWELL.. 03/13/2008
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