SPC AC 221629
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 AM CDT MON OCT 22 2007
VALID 221630Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE LOWER MS VALLEY
THROUGH TONIGHT...
...LOWER MS VALLEY AREA THROUGH TONIGHT...
THE DEEP MID LEVEL TROUGH OVER W TX/OK WILL MOVE EWD AND EVOLVE INTO
A CLOSED LOW OVER SE OK/NE TX BY LATE TONIGHT. AN ASSOCIATED WEAK
SURFACE CYCLONE NOW NEAR SHV WILL MOVE ENEWD TOWARD THE MS/TN/AL
BORDER REGION LATE TONIGHT...WHILE A TRAILING COLD FRONT PROGRESSES
EWD ACROSS LA/MS.
A MARITIME TROPICAL AIR MASS /BOUNDARY LAYER DEWPOINTS IN THE 70S/
HAS SPREAD NWD INTO CENTRAL LA AND SRN MS/AL TO THE S OF A
RETREATING MARINE FRONT...AND E OF THE COLD FRONT APPROACHING THE
TX/LA BORDER. RELATIVELY WIDESPREAD CONVECTION IS ONGOING OVER THE
N CENTRAL GULF INTO SE LA WITHIN THE SWATH OF STRONGEST MOISTURE
TRANSPORT...AND THIS CONVECTION WILL LIKELY SPREAD NNEWD THROUGH
TONIGHT WHILE GRADUALLY CONSOLIDATING INTO A BAND NEAR THE COLD
FRONT. A CORRIDOR OF STRONGER SURFACE HEATING WILL OCCUR TODAY FROM
SW MS INTO SRN LA...WHERE AFTERNOON MLCAPE VALUES WILL LIKELY REACH
1000-1500 J/KG AS SURFACE TEMPERATURES WARM INTO THE 80S. FARTHER
E/NE...THE CLOUDS/RAINFALL WILL LIMIT INSTABILITY THROUGH THE
PERIOD.
DESPITE THE MODERATE MLCAPE VALUES ACROSS SRN LA...MID LEVEL LAPSE
RATES WILL BE AOB 6 C/KM...AND LOW-LEVEL WINDS/SHEAR IN THE MOST
UNSTABLE PORTION OF THE WARM SECTOR WILL BE RATHER WEAK AS A RESULT
OF MINIMAL SURFACE CYCLOGENESIS. THE MORE FAVORABLE
SUPERCELL/TORNADO WIND PROFILES ARE EXPECTED FARTHER E ACROSS SE MS
AND AL TODAY INTO TONIGHT IN CONJUNCTION WITH THE LLJ...WHERE
INSTABILITY WILL BE MARGINAL. THEREFORE...THE OVERALL THREAT FOR
SUPERCELL TORNADOES AND/OR DAMAGING WINDS WITH EMBEDDED BOW ECHOES
IS CORRESPONDINGLY MARGINAL.
..THOMPSON/GRAMS.. 10/22/2007
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
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