SWODY1
SPC AC 131243
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0743 AM CDT THU MAR 13 2008
VALID 131300Z - 141200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER ERN PARTS OF THE SRN
PLAINS INTO THE LOWER MS VALLEY...
..SRN PLAINS INTO THE LOWER MS RIVER VALLEY/MID SOUTH...
MODELS ARE IN AGREEMENT IN TAKING FAST MOVING SHORTWAVE TROUGH EWD
ACROSS THE SRN PLAINS TODAY AND OVER THE MS RIVER VALLEY TONIGHT.
SMALL AREA OF ENHANCED WSWLY MID LEVEL FLOW /H5 WINDS AOA 50 KT/
WILL DEVELOP OVER ERN TX INTO THE LOWER MS RIVER VALLEY ASSOCIATED
WITH THIS SYSTEM. IN ADDITION...SWLY LLJ WILL STRENGTHEN BY LATE
TODAY OVER ERN TX WHICH WILL INTENSIFY AND BECOME MORE WLY ACROSS
THE LOWER MS RIVER VALLEY OVERNIGHT. AT THE SURFACE...LOW TAKING
SHAPE OVER SWRN OK/NWRN TX ATTM WILL BECOME BETTER DEFINED AND SHIFT
ENEWD ACROSS OK TODAY WITH TROUGH/DRY LINE EXTENDING SSWWD AS IT
MOVES ACROSS CENTRAL TX.
ALTHOUGH LARGE SCALE PATTERN WILL BECOME INCREASINGLY SUPPORTIVE OF
THUNDERSTORM DEVELOPMENT OVER THIS REGION...SYSTEM WILL BE
RELATIVELY DRY WITH PW/S OF HALF-INCH OR LESS AND SURFACE DEW POINTS
BELOW 50F EARLY THIS MORNING. STRENGTHENING RETURN FLOW AT LOWER
LEVELS WILL SUPPORT MODEST MOISTURE RETURN FOR THIS TIME OF YEAR
WITH SURFACE DEW POINTS LIKELY APPROACHING 60F ACROSS ERN TX AND MID
50F READINGS DEVELOPING INTO ERN OK/WRN AR BY 00Z. DESPITE
MOISTENING LOW LEVELS...MODEL SOUNDINGS /SUPPORTED BY 12Z SOUNDINGS
AT OUN AND FTW/ INDICATE SUBSTANTIAL ELEVATED MIXED-LAYER IN PLACE
OVER THE SRN PLAINS. THIS WILL EFFECTIVELY CAP MUCH OF THE REGION
UNTIL LATE TODAY.
..ERN OK/NERN TX INTO THE MID SOUTH...
COMBINATION OF HEATING AND INCREASING DEEP ASCENT EXPECTED TO
SUPPORT THUNDERSTORMS OVER NERN TX/ERN OK/WRN AR LATE TODAY...WHICH
WILL INCREASE IN COVERAGE AND DEVELOP ENEWD OVERNIGHT. LOW LEVEL
SHEAR WILL BE RELATIVELY STRONG AND CERTAINLY SHOULD SUPPORT THE
POTENTIAL FOR LOW LEVEL ROTATION/ISOLATED TORNADOES WHERE STORMS
REMAIN ROOTED NEAR THE SURFACE. HOWEVER...DEEP LAYER SHEAR IS
FORECAST TO REMAIN MARGINAL FOR SUSTAINED SUPERCELLS AND ACTIVITY
MAY EVOLVE INTO SEVERAL MULTICELL CLUSTERS WITH EMBEDDED SUPERCELLS.
LARGE HAIL WILL BECOME PRIMARY SEVERE THREAT AS STORMS BECOME
ELEVATED DUE TO STABILIZING BOUNDARY LAYER AFTER SUNSET...ALTHOUGH
VERY STEEP LAPSE RATES MAY SUPPORT A FEW VERY LARGE HAIL STONES.
..ERN TX ACROSS THE LOWER MS RIVER VALLEY...
DIURNAL DEVELOPMENT INTO ERN TX IS MORE CONDITIONAL THAN POINTS
FARTHER NORTH GIVEN PRONOUNCED CAPPING AND QUESTIONABLE MOISTURE
RETURN. HOWEVER SHOULD CAP BREAK NEAR/EAST OF APPROACHING SURFACE
TROUGH...PARAMETERS WILL BE FAVORABLE FOR SUPERCELLS /SOME
LONGER-LIVED/ GIVEN THE ENHANCED EML AND STRONGER SHEAR PROFILES IN
PLACE. MODELS ARE NOT CONSISTENT IN QPF OVER THIS REGION THIS
AFTERNOON...BUT COME INTO BETTER AGREEMENT LATER THIS EVENING IN
DEVELOPING WIDESPREAD THUNDERSTORMS FROM SERN TX ACROSS LA/MS
OVERNIGHT. SURFACE BASED/TORNADO-WIND THREATS WILL REMAIN DEPENDANT
ON DEGREE OF MOISTURE RETURN. HOWEVER...FORECAST SOUNDINGS SUGGEST
ACTIVITY WILL BECOME ELEVATED WITH PRIMARY THREAT OF LARGE HAIL
DIMINISHING AS ACTIVITY OVERSPREADS THE LOWER MS RIVER VALLEY LATER
TONIGHT.
.EVANS/SMITH.. 03/13/2008
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