SWODY1
SPC AC 300056
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0656 PM CST SAT NOV 29 2008
VALID 300100Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SERN AL/SWRN GA AND
PORTIONS OF THE FL PANHANDLE...
...SYNOPSIS...
A DEEPENING LONG WAVE TROUGH WILL CONTINUE TO EVOLVE THIS FORECAST
PERIOD ACROSS THE FULL EXTENT OF THE MS VALLEY...AS ONE SHORT WAVE
TROUGH MOVES EWD INTO THE MID MS/LOWER OH VALLEYS AND AN UPSTREAM
SHORT WAVE TROUGH DIGS SEWD THROUGH THE PLAINS.
IN THE LOW LEVELS AT 00Z...SURFACE LOW DEVELOPMENT WAS UNDERWAY
ACROSS SERN MO/LOWER TN VALLEY IN RESPONSE TO THE DEEPENING MS
VALLEY TROUGH. A SECOND AREA OF LOW PRESSURE WAS LOCATED FURTHER SE
IN WRN/CENTRAL AL...WITH A COLD FRONT TRAILING SWWD FROM THIS LOW
THROUGH SERN LA TO THE NWRN GULF. THIS FRONT IS EXPECTED TO
PROGRESS EWD AND EXTEND FROM CENTRAL GA SWWD THROUGH FL PANHANDLE TO
NERN GULF BY 12Z SUNDAY. A WARM FRONT EXTENDED EWD FROM THE AL LOW
THROUGH CENTRAL GA TO THE SC COAST. MEANWHILE...AN OUTFLOW
BOUNDARY/SURFACE TROUGH EXTENDED NEWD FROM ITS INTERSECTION WITH THE
COLD FRONT IN THE NWRN GULF THROUGH THE WRN FL PANHANDLE TO SWRN GA.
THIS SURFACE TROUGH AND THE COLD FRONT ARE EXPECTED TO BE THE
PRIMARY FOCI FOR TSTM DEVELOPMENT THROUGH 12Z SUNDAY.
...CENTRAL/EASTERN GULF STATES...
AN EXTENSIVE AREA OF ONGOING PRECIPITATION EXTENDED FROM THE NWRN
GULF THROUGH SERN MS...SRN AL...FL PANHANDLE...SRN GA TO SRN SC.
THIS COMBINED WITH WEAK MID LEVEL LAPSE RATES WILL MAINTAIN A MORE
STABLE AIR MASS INLAND...WHILE OBJECTIVE ANALYSES INDICATED STRONGER
INSTABILITY ALONG AND S OF THE PRE-FRONTAL TROUGH IN THE NRN GULF
WITH WEAK INSTABILITY EXTENDING INTO THE FL PANHANDLE.
A PRECEDING JET STREAK...NOW LOCATED OVER THE NWRN GULF /70 KT/...
WILL TRANSLATE ENEWD THROUGH THE CENTRAL/ERN GULF COAST TO SRN
ATLANTIC STATES TONIGHT. ASCENT ATTENDANT TO THIS FEATURE AND
HEIGHT FALLS WITH THE MS VALLEY LONG WAVE TROUGH WILL SUPPORT
ADDITIONAL TSTM DEVELOPMENT THIS FORECAST PERIOD ALONG THE
PROGRESSIVE COLD FRONT AND IN THE VICINITY OF THE PRE-FRONTAL TROUGH
EXTENDING NEWD INTO THE SLIGHT RISK AREA. THIS PROCESS MAY ALREADY
BE UNDERWAY GIVEN THE RECENT INCREASE IN EARLY EVENING LIGHTNING
ACTIVITY OVER THE NWRN GULF /70-100 MILES S OF LA COAST/...WHERE
INSTABILITY WAS GREATER...AND FARTHER N INTO SERN LA/SRN MS WHERE
REGIONAL RADARS SHOWED INCREASING REFLECTIVITY.
ALTHOUGH INSTABILITY WILL BE WEAK INLAND OF THE COAST...THE SLIGHT
RISK AREA WILL BE MAINTAINED OVERNIGHT DUE TO THE EXPECTED INCREASE
IN EFFECTIVE BULK SHEAR /40-60 KT/ AS THE 70 KT JET STREAK MOVES
ACROSS THIS AREA. AND...A STRENGTHENING SSWLY LLJ /50+ KT/
DEVELOPING AFTER 06Z INTO FL PANHANDLE/SE AL/GA WILL ENHANCE LOW
LEVEL SHEAR FOR A NON-ZERO THREAT FOR TORNADOES. MODELS SUGGEST A
SQUALL LINE WITH A THREAT FOR STRONG WIND GUSTS WILL DEVELOP LATER
THIS EVENING THROUGH TONIGHT ALONG THE COLD FRONT WITH ADDITIONAL
CELLULAR/SUPERCELL DEVELOPMENT POSSIBLE OVER THE GULF WITH THIS
ACTIVITY SPREADING INLAND OVER THE FL PANHANDLE. THIS LATTER
ACTIVITY MOVING ONSHORE SHOULD POSE THE GREATEST THREAT FOR ISOLATED
TORNADOES.
..PETERS.. 11/30/2008
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