SWODY2
SPC AC 141712
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1112 AM CST FRI NOV 14 2008
VALID 151200Z - 161200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE MID
ATLANTIC STATES INTO THE ERN CAROLINAS...
...SYNOPSIS...
DYNAMIC LARGE-SCALE TROUGH WILL ASSUME AN INCREASING NEGATIVE TILT
WHILE PROGRESSING EWD TOWARD THE ATLANTIC COAST AS 120-150 KT
UPPER-LEVEL JET STREAK DEVELOPS DOWNSTREAM FROM THE TROUGH BASE.
THIS EVOLUTION WILL RESULT IN A BROAD CORRIDOR OF SIGNIFICANT HEIGHT
FALLS SHIFTING EWD FROM THE TN AND LOWER MS VALLEYS TO ALONG THE
LENGTH OF THE ATLANTIC COAST BY SUNDAY MORNING.
IN THE LOW LEVELS...DIFFERENCES DO EXIST IN LATEST MODEL GUIDANCE IN
THE TRACK OF THE PRIMARY SURFACE LOW AND MOVEMENT ATTENDANT COLD
FRONT. NONETHELESS...IT DOES APPEAR THAT THIS SURFACE LOW INITIALLY
OVER THE CNTRL APPALACHIANS WILL DEEPEN WHILE DEVELOPING NNEWD INTO
THE ST. LAWRENCE VALLEY OR ERN/SERN QUEBEC BY THE END OF THE PERIOD.
MEANWHILE...TRAILING COLD FRONT WILL SURGE EWD FROM THE APPALACHIANS
TOWARD THE MIDDLE AND SERN ATLANTIC COASTS SATURDAY BEFORE
EVENTUALLY MOVING OFFSHORE SATURDAY NIGHT. FARTHER N...THIS FRONT
WILL MOVE THROUGH THE HUDSON VALLEY BY LATE DAY/EARLY EVENING AND
INTO ERN NEW ENGLAND BY SUNDAY MORNING.
...SRN NEW ENGLAND SWD TO PARTS OF GA/NRN FL...
DYNAMICALLY FORCED 50+ LLJ WILL ENHANCE THE NWD FLUX OF AN
INCREASINGLY MOIST BOUNDARY LAYER WITH DEWPOINTS INCREASING THROUGH
THE 60S WITHIN PRE-FRONTAL WARM SECTOR. HOWEVER... WIDESPREAD
CLOUDINESS AND PERSISTENT SHOWER/TSTM DEVELOPMENT WILL LIKELY LIMIT
DIABATIC HEATING AND RESULTANT STEEPENING OF LAPSE RATES WITH MLCAPE
REMAINING AOB 500-1000 J/KG.
AS MENTIONED ABOVE...EPISODIC TSTM DEVELOPMENT IS ANTICIPATED
THROUGH THE DAY ACROSS PRE-FRONTAL WARM SECTOR AS STRENGTHENING
LARGE-SCALE FORCING FOR ASCENT ACTS ON A WEAKLY CAPPED AIR MASS.
WITH TIME...THE WRN EDGE OF MORE INTENSE TSTM ACTIVITY MAY EVOLVE
INTO A SINGULAR OR SEGMENTED BAND WITHIN ZONE OF STRONG MESOSCALE
ASCENT ALONG COLD FRONT. FORECAST SOUNDINGS INDICATE THAT VERTICAL
SHEAR /BOTH THROUGH A DEEP LAYER AND IN THE LOW LEVELS/ WILL BE
QUITE STRONG WITH THE POTENTIAL FOR EMBEDDED SUPERCELL AND/OR
BOWING/LEWP STRUCTURES.
CORRIDORS OF DAMAGING WINDS WILL BE THE PRIMARY SEVERE WEATHER
THREAT...THOUGH A COUPLE OF TORNADOES ARE POSSIBLE WITH ANY MORE
PERSISTENT SUPERCELLS AND/OR QLCS MESOVORTICIES. THIS SEVERE
WEATHER THREAT APPEARS MOST LIKELY FROM PARTS OF ERN VA/TIDEWATER
REGION SWD ACROSS ERN NC INTO NERN SC WHERE THE STRONGEST
INSTABILITY IS FORECAST. THIS THREAT BECOMES MORE CONDITIONAL WITH
NWD EXTENT INTO THE DE RIVER VALLEY DUE TO WEAKER INSTABILITY. OVER
THE LOWER HUDSON VALLEY AND SRN NEW ENGLAND...FORECAST SOUNDINGS
SUGGEST THAT STORMS WILL LIKELY REMAIN SLIGHTLY ELEVATED ABOVE A
SHALLOW NEAR-SURFACE INVERSION. HOWEVER...THE POTENTIAL WILL EXIST
FOR ANY STRONGER DOWNDRAFTS TO TRANSLATE LOCALLY DAMAGING WINDS TO
THE GROUND. OVER GA/NRN FL...A MORE ORGANIZED SEVERE WEATHER THREAT
WILL LIKELY BE LIMITED BY WEAKENING CONVERGENCE ALONG COLD FRONT.
GIVEN THE STRONGLY SHEARED AND DYNAMICALLY-FORCED CHARACTER OF THE
SYNOPTIC PATTERN...HIGHER SEVERE WEATHER PROBABILITIES MAY BECOME
NECESSARY IN LATER OUTLOOKS SHOULD IT BECOME APPARENT THAT STRONGER
INSTABILITY WILL DEVELOP THAN IS CURRENTLY FORECAST.
..MEAD.. 11/14/2008
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