SWODY1
SPC AC 251946
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0246 PM CDT THU MAR 25 2010
VALID 252000Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MID-SOUTH/TN
VALLEY...
...MID-SOUTH/TN VALLEY...
AS A SHORTWAVE TROUGH QUICKLY ADVANCES NORTHEASTWARD FROM THE MS
RIVER/MID-SOUTH TO THE TN VALLEY TONIGHT...ARCING/BROKEN BANDS OF
LOW-TOPPED TSTMS/INCLUDING SOME SEVERE WILL CONTINUE TO DEVELOP
ALONG/EAST OF LOWER OH VALLEY SURFACE LOW AND ASSOCIATED SOUTHWARD
EXTENDING OCCLUDED FRONT. PRIMARY THREAT WOULD APPEAR TO BE DAMAGING
WINDS...WITH SOME CONCERN FOR SEVERE HAIL/PERHAPS A BRIEF TORNADO
RISK AS WELL LATE THIS AFTERNOON. CONSIDERABLE DRYING ALOFT PER
WATER VAPOR IMAGERY AND WEAKENING LOW LEVEL CONVERGENCE LIMITS
CONFIDENCE IN THE SOUTHWARD EXTENT OF DEVELOPMENT ACROSS EASTERN MS
AND AL TOWARD/SOUTH OF I-20...BUT AT LEAST A CONDITIONAL SEVERE
THREAT WILL EXIST IN THESE AREAS THROUGH LATE AFTERNOON/EARLY
EVENING.
...FL...
NORTHEAST-SOUTHWEST ORIENTED SQUALL LINE WILL CONTINUE TO PROGRESS
EASTWARD ACROSS THE FL PANHANDLE/ADJACENT GULF OF MEXICO THIS
AFTERNOON. THE PRE-SQUALL LINE AIRMASS WILL NOT HAVE THE OPPORTUNITY
TO APPRECIABLY MOISTEN/DESTABILIZE ACROSS FL...BUT THE
SEMI-ORGANIZED NATURE OF THE CONVECTIVE LINE AND STRENGTHENING DEEP
LAYER FLOW THROUGH TONIGHT IMPLIES SOME POTENTIAL FOR A SEVERE
THREAT TO INCREASE LATE THIS AFTERNOON...OR MORE SO TONIGHT ACROSS
FL PENINSULA. NOTHING MORE THAN LOW SEVERE PROBABILITIES APPEAR
WARRANTED HOWEVER.
..GUYER.. 03/25/2010
.PREV DISCUSSION... /ISSUED 1122 AM CDT THU MAR 25 2010/
...LOWER MS AND TN VALLEYS...
SRN PLAINS VIGOROUS MID LEVEL VORT/COLD POOL HAS MOVED AT 15Z INTO
SWRN AR AND WILL TRACK ENEWD ACROSS LOWER MS VALLEY THIS AFTERNOON.
ASSOCIATED SURFACE LOW NRN AR WILL MOVE INTO SWRN KY WITH SOME
DEEPENING THIS AFTERNOON AS COLD FRONT SWEEPS EWD ACROSS MS RIVER
INTO WRN TN VALLEY.
INITIAL LIMITING PARAMETER FOR SEVERE THUNDERSTORMS TODAY IS
INSTABILITY. HOWEVER WITH THE CLEARING THAT HAS SPREAD EWD INTO WRN
MS AND NERN AR IN THE DRY SLOT AHEAD OF COLD FRONT...COMBINED WITH
THE STRONG COLD ADVECTION AND VIGOROUS LARGE SCALE ASCENT ASSOCIATED
WITH THE MID LEVEL VORT/UPPER LOW...IT NOW APPEARS THAT PRIOR TO
FROPA THIS INSTABILITY WILL BE SUFFICIENT TO SUPPORT LOW TOPPED
THUNDERSTORMS WITH THE STRONG VEERING SHEAR PROFILES RAISING THE
CONCERN FOR SUPERCELLS.
AS TEMPS WARM THRU THE 60S ACROSS MS INTO SWRN TN AND DEWPOINTS
REMAIN IN THE MID/UPPER 50S...MLCAPES WILL INCREASE TO ABOVE 500 J/G
WHICH UNDER THE STRONG MID LEVEL COLD ADVECTION WILL REMOVE ANY CINH
BY EARLY/MID AFTERNOON. THUNDERSTORMS WILL DEVELOP ALONG/AHEAD OF
THE FRONT AS IT CROSSES MS RIVER INTO SWRN TN/NRN MS WITH WIND
DAMAGE THE PRIMARY THREAT GIVEN THE 60-70KT OF DEEP LAYER SHEAR AND
NOTICEABLE MID LEVEL DRYING ACCOMPANYING THE 90KT 500 MB WIND MAX.
HOWEVER IT NOW APPEARS THERE WILL BE SUFFICIENT INSTABILITY
AVAILABLE TO RAISE THE THREAT OF AT LEAST AN ISOLATED
SUPERCELL/TORNADO THREAT THIS AFTERNOON INTO PORTIONS OF TN/NRN AL
AND NERN MS.
ON THE SOUTH SIDE OF THE POLAR JET...LAPSE RATES WILL BE WEAKER AND
INSTABILITY LESS. THIS SHOULD PRECLUDE AN ORGANIZED SEVERE THREAT
WITH THE COLD FRONT NEARER THE GULF COAST.
VIGOROUS THUNDERSTORMS OVER NRN GULF SHOULD PRIMARILY REMAIN
OFFSHORE GIVEN THE EXPECTED LIMITED AMOUNT OF INSTABILITY THAT WILL
BE ABLE TO DEVELOP WITH LITTLE IN THE WAY OF SURFACE HEATING AND THE
UPPER SYSTEM WELL TO THE N.
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