SWODY1
SPC AC 010600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1200 AM CST TUE DEC 01 2009
VALID 011200Z - 021200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SERN LA...SERN MS AND
SWRN AL TUESDAY EVENING/NIGHT...
...SYNOPSIS...
00Z NAM/GFS AND 12Z ECMWF ARE IN AGREEMENT WITH TRACK OF NRN MEXICO
CLOSED LOW/ASSOCIATED TROUGH INTO TX THIS FORECAST PERIOD. THIS
FEATURE IS EXPECTED TO BE LOCATED OVER CHIHUAHUA MEXICO AT 12Z
TODAY...AND WILL DEEPEN AS IT TAKES ON A NEGATIVE TILT LATER IN THE
FORECAST PERIOD...REACHING E TX BY 12Z WEDNESDAY. THIS PROCESS WILL
SUPPORT A TIGHTENING OF THE DOWNSTREAM MID/UPPER LEVEL HEIGHT
GRADIENT FROM THE WRN GULF TO THE LOWER MS VALLEY/ CENTRAL GULF
COAST STATES.
IN THE LOW LEVELS...A SURFACE LOW FORMING OVER THE WRN GULF OF
MEXICO /E OF BRO/ BY 12Z TODAY SHOULD MOVE NEWD REACHING THE SRN LA
COAST /S OF LFT/ EARLY TUESDAY EVENING...AND THEN TRACK INLAND TO
FAR SRN MS LATE TUESDAY NIGHT/EARLY WEDNESDAY MORNING. THIS
SCENARIO FAVORS THE 00Z NAM/12Z ECMWF...WHILE THE 00Z GFS BRINGS THE
SAME LOW INTO SRN AL BY 12Z WEDNESDAY. THIS OUTLOOK IS BASED MORE
SO ON THE FORMER TWO MODELS.
...LOWER MS VALLEY/CENTRAL GULF COAST REGION...
SURFACE PRESSURE FALLS ARE EXPECTED ACROSS THE NWRN GULF INTO THE
LOWER MS VALLEY THIS FORECAST PERIOD AS THE NRN MEXICO MID/UPPER
LEVEL LOW APPROACHES CENTRAL/E TX. THIS COMBINED WITH A
STRENGTHENING SLY LLJ WILL ALLOW AN E-W ORIENTED SURFACE BOUNDARY
OVER THE GULF TO SPREAD NWD REACHING THE LA COAST BY 02/00Z.
INITIALLY...INCREASING WARM/MOIST ADVECTION WILL CONTRIBUTE TO
CONSIDERABLE SHOWERS/TSTMS THAT SHOULD REINFORCE THE BAROCLINIC
ZONE...BUT AN EVENING/OVERNIGHT SURGE OF THIS BOUNDARY IS EXPECTED
BRINGING THE WARM SECTOR OVER SERN LA/MS TO SWRN AL AFTER DARK.
DESPITE GENERALLY WEAK LAPSE RATES ACROSS THIS REGION THROUGH THE
FORECAST PERIOD...THE INTRUSION OF THE WARM SECTOR IS EXPECTED TO
SUPPORT A THERMODYNAMIC PROFILE FAVORABLE FOR SURFACE BASED STORMS
WITH MLCAPE RANGING FROM 250-500 J/KG BETWEEN 02/00Z TO 02/12Z.
THIS COMBINED WITH INCREASING DEEP LAYER AND LOW LEVEL SHEAR VALUES
AS MID LEVEL WINDS INCREASE TO 50-75 KT ATOP A 60-70 KT SSWLY LLJ IS
EXPECTED TO SUPPORT ORGANIZED STORMS/SUPERCELLS. THE STRONG LLJ
WILL RESULT IN LARGE CURVED HODOGRAPHS FAVORING A THREAT FOR
TORNADOES...WHILE DAMAGING WINDS WILL ALSO BE POSSIBLE...ESPECIALLY
AS A TRAILING COLD FRONT SPREADS EWD ACROSS SERN LA/SERN MS LATE
TUESDAY NIGHT.
..PETERS.. 12/01/2009
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