SWODY2
SPC AC 131726
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1126 AM CST THU NOV 13 2008
VALID 141200Z - 151200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE SERN
STATES...
...SYNOPSIS...
LARGE-SCALE TROUGH OVER THE CNTRL U.S. WILL INTENSIFY DURING THE DAY
TWO PERIOD AS STRONG SHORT WAVE TROUGH AND ASSOCIATED UPPER LEVEL
JET STREAK DIG SEWD THROUGH THE CNTRL/SRN PLAINS THROUGH THE MID AND
LOWER MS VALLEYS. AS THIS OCCURS...LOWER LATITUDE IMPULSE INITIALLY
OVER THE NWRN GULF OF MEXICO WILL WEAKEN WHILE LIFTING NEWD ALONG
THE GULF COAST AND EVENTUALLY ACROSS THE SERN STATES.
IN THE LOW LEVELS...DEEP-LAYER FORCING ASSOCIATED WITH INTENSIFYING
CNTRL U.S. TROUGH WILL SUPPORT EVENTUAL CYCLOGENESIS ALONG COLD
FRONT OVER THE OH VALLEY. TRAILING PORTION OF COLD FRONT WILL SURGE
SEWD THROUGH THE SRN PLAINS...MID SOUTH AND CNTRL GULF STATES.
DOWNSTREAM FROM THIS COLD FRONT...BAROCLINIC ZONE CURRENTLY STALLED
ACROSS SRN PARTS OF AL/GA AND THE COASTAL CAROLINAS WILL LIFT NWD IN
RESPONSE TO APPROACH OF WEAKENING...LOWER LATITUDE IMPULSE.
...SERN STATES NEWD INTO THE TIDEWATER REGION...
CURRENT SURFACE OBSERVATION AND 13/12Z SOUNDING DATA INDICATE THAT A
MOIST BOUNDARY LAYER IS PRESENT S OF STALLED FRONTAL ZONE WITH
DEWPOINTS IN THE MID 60S TO LOWER 70S AND 100-MB MEAN MIXING RATIOS
OF 14-15 G/KG. INCREASING SWLY LLJ IN ADVANCE OF APPROACHING UPPER
WAVE SHOULD SUPPORT THE NWD RETREAT OF THIS BOUNDARY...WITH AN AIR
MASS OF SIMILAR CHARACTER BECOMING ESTABLISHED FURTHER INLAND ACROSS
SERN AL...GA...AND THE CAROLINAS. WHILE RESIDUAL CLOUDINESS AND
SCATTERED TSTM ACTIVITY WILL LIMIT LAPSE RATES...THIS RICH BOUNDARY
LAYER MOISTURE AND SOME DAYTIME HEATING WILL CONTRIBUTE TO AIR MASS
DESTABILIZATION THROUGH THE DIURNAL HEATING CYCLE. THIS IS
PARTICULARLY THE CASE ACROSS SERN AL...NRN FL AND SRN GA WHERE
POCKETS OF STRONGER HEATING MAY CONTRIBUTE TO MLCAPE APPROACHING
1000-1500 J/KG.
TSTMS WILL LIKELY BE ONGOING EARLY IN THE PERIOD ALONG AND TO THE N
OF SURFACE BOUNDARY WITHIN WARM CONVEYOR AIRSTREAM WHERE ASCENT WILL
BE ENHANCED BY STRENGTHENING LLJ. INCREASED DEEP-LAYER FORCING FOR
ASCENT IN ADVANCE OF WEAKENING UPPER WAVE IS EXPECTED TO SUPPORT
MORE ROBUST WARM SECTOR STORM DEVELOPMENT BY AFTERNOON OVER PORTIONS
OF SERN AL...THE FL PNHDL AND SWRN GA. THIS ACTIVITY IS EXPECTED TO
MOVE/DEVELOP NEWD ACROSS NRN FL/GA AND THE CAROLINAS LATER FRIDAY
AFTERNOON INTO FRIDAY NIGHT AS SHORT WAVE TROUGH LIFTS NEWD ACROSS
THE REGION.
DEEP-LAYER VERTICAL SHEAR WILL STEADILY INCREASE TO 45-50 KT ACROSS
WARM SECTOR AS WIND FIELDS RESPOND TO APPROACHING UPPER TROUGH.
THIS WILL BE MORE THAN SUFFICIENT TO SUPPORT EMBEDDED SUPERCELL
AND/OR BOWING STRUCTURES IN AREAS WHERE THE STRONGER INSTABILITY CAN
DEVELOP. LATEST MODEL GUIDANCE SUGGESTS THAT THE STRONGER LOW-LEVEL
SHEAR WILL REMAIN CONFINED TO RETREATING WARM/WEDGE FRONT WHERE ONLY
MARGINAL INSTABILITY IS FORECAST. AS SUCH...THE PRIMARY SEVERE
WEATHER THREAT APPEARS TO BE DAMAGING WINDS IN ASSOCIATION WITH ANY
MORE ORGANIZED STORMS THAT CAN DEVELOP ACROSS SLIGHT RISK AREA.
..MEAD.. 11/13/2008
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