SWODY2
SPC AC 130558
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CDT FRI APR 13 2007
VALID 141200Z - 151200Z
..THERE IS A MDT RISK OF SVR TSTMS ACROSS SERN LA...SERN MS...SRN
AL...SWRN GA...AND THE FL PANHANDLE...
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS SURROUNDING AREAS OF THE
SOUTHEASTERN U.S....
..SYNOPSIS...
HIGHLY-AMPLIFIED/PROGRESSIVE UPPER PATTERN IS FORECAST ACROSS THE
CONUS THIS PERIOD. WHILE A STRONG UPPER TROUGH IS FORECAST TO MOVE
ONSHORE/INLAND ACROSS THE WRN CONUS THROUGH THE PERIOD...THE MAIN
FEATURE WITH RESPECT TO THE SEVERE CONVECTIVE FORECAST WILL BE A
SECOND LARGE TROUGH FURTHER E. THIS TROUGH -- INITIALLY EXTENDING
FROM ONTARIO SWWD INTO W TX -- WILL SHIFT EWD WITH TIME...WHILE
TAKING ON A MORE NEUTRAL TILT. BY THE END OF THE PERIOD...THE
TROUGH AXIS SHOULD EXTEND FROM ROUGHLY JAMES BAY SWD INTO THE ERN
GULF OF MEXICO.
AT THE SURFACE...A WEAK LOW IS INITIALLY FORECAST OVER THE MS DELTA
REGION...WITH A COLD FRONT EXTENDING SWWD INTO SERN TX. THE LOW IS
FORECAST TO DEEPEN SLOWLY WITH TIME...WHILE IT AND THE ASSOCIATED
COLD FRONT MOVE EWD ACROSS THE SOUTHEAST THROUGH THE FIRST HALF OF
THE PERIOD. DURING THE SECOND HALF OF THE PERIOD...THIS LOW IS
FORECAST TO DEEPEN MORE RAPIDLY...WHILE MOVING NEWD ACROSS THE
ATLANTIC COAST STATES TO VA BY THE END OF THE PERIOD.
..THE SOUTHEAST...
STRONG TO SEVERE THUNDERSTORMS ARE FORECAST TO BE ONGOING
ALONG/AHEAD OF COLD FRONT AT THE START OF THE PERIOD...FROM WRN MS
SWWD TO SWRN LA. MEANWHILE...BROAD REGION OF SLY SURFACE WIND IS
FORECAST TO BE ADVECTING RICH BOUNDARY-LAYER MOISTURE NWD OFF THE
GULF INTO THE GULF COAST STATES. THOUGH WEAK LAPSE RATES SHOULD
LIMIT THE OVERALL POTENTIAL FOR WARM SECTOR DESTABILIZATION...MID
60S TO LOW 70S DEWPOINTS SPREADING ACROSS THE SRN HALVES OF THE GULF
COAST STATES BY MIDDAY COMBINED WITH DAYTIME HEATING SHOULD RESULT
IN 500 TO 1000 J/KG MEAN-LAYER CAPE BY MIDDAY/EARLY AFTERNOON.
STORMS SHOULD INTENSIFY WITHIN THE LINEAR COMPLEX ALONG/AHEAD OF
COLD FRONT THROUGH MIDDAY...WHILE A FEW ISOLATED STORMS MAY DEVELOP
AHEAD OF THE MAIN CONVECTIVE LINE NEAR SUBTLE LOW-LEVEL BOUNDARIES
POSSIBLY ASSOCIATED WITH WEAK LEAD MID-LEVEL FEATURE.
THOUGH MAIN UPPER TROUGH AND ASSOCIATED COOLING ALOFT SHOULD REMAIN
WELL TO THE W OF THE SURFACE FRONT...STRONG SWLY LOW-LEVEL WIND
FIELD BENEATH DIFFLUENT 60 TO 70 KT SWLY MID-LEVEL FLOW ACROSS THE
WARM SECTOR WILL RESULT IN SHEAR FAVORABLE FOR ORGANIZED/SUPERCELL
STORMS. WHILE IT APPEARS THAT FLOW FROM ROUGHLY 850 MB AND ABOVE
WILL BE ROUGHLY UNIDIRECTIONAL...SLY SURFACE WINDS VEERING TO SWLY
AT 850 MB SHOULD YIELD SUFFICIENT SHEAR FOR LOW-LEVEL UPDRAFT
ROTATION. THIS COMBINED WITH MOIST BOUNDARY LAYER -- PARTICULARLY
WITH SWD EXTENT TOWARD THE GULF COAST -- AS WELL AS THE OVERALL
INTENSITY OF THIS SYSTEM SUGGEST THAT SEVERAL TORNADOES WILL BE
POSSIBLE. IN ADDITION...STRENGTH OF DEEP-LAYER WIND FIELD AND
ANTICIPATED LINEAR ORGANIZATION OF CONVECTION ALONG THE COLD FRONT
ALSO APPEARS SUPPORTIVE OF WIDESPREAD DAMAGING WINDS.
A SECONDARY AREA OF STORMS MAY DEVELOP NEAR THE WARM FRONT --
ANTICIPATED OVER GA/SC DURING THE AFTERNOON...WHERE AN ASSOCIATED
POTENTIAL FOR SEVERE STORMS/TORNADOES WOULD EXIST. OVERNIGHT...THE
COLD FRONT SHOULD SHIFT EWD ACROSS GA/THE CAROLINAS/NRN FL...ALONG
WITH AN INCREASE IN STORM COVERAGE AND A CONTINUATION OF THE SEVERE
THREAT THROUGH THE END OF THE PERIOD.
.GOSS.. 04/13/2007
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