DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 140546
SWODY1
SPC AC 140544

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1144 PM CST TUE NOV 13 2007

VALID 141200Z - 151200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER MS/TN
VALLEYS...

..SYNOPSIS...
AMPLIFICATION OF THE UPPER PATTERN IS FORECAST ACROSS THE CONUS THIS
PERIOD...AS LARGE UPPER TROUGH DIGS SEWD ACROSS THE CENTRAL AND INTO
THE ERN CONUS. MEANWHILE...UPSTREAM RIDGE WILL PROGRESS EWD ACROSS
THE ROCKIES AHEAD OF A SECOND TROUGH APPROACHING THE W COAST.
ELSEWHERE...CUTOFF UPPER LOW IS EXPECTED TO DRIFT TOWARD THE CENTRAL
BAJA COAST.

AT THE SURFACE...A SHARP COLD FRONT INITIALLY EXTENDING FROM THE
GREAT LAKES REGION WSWWD INTO THE SRN PLAINS WILL SHIFT
SEWD...CROSSING THE APPALACHIANS AND REACHING THE GULF COAST BY THE
END OF THE PERIOD.

..LOWER MS/TN VALLEY REGION...
THUNDERSTORMS ARE FORECAST TO BEGIN DEVELOPING BY MIDDAY/EARLY
AFTERNOON ACROSS PARTS OF THE MID MS/TN VALLEY REGION INVOF
ADVANCING COLD FRONT...AS DAYTIME HEATING OF SEASONABLY-MOIST
PRE-FRONTAL BOUNDARY LAYER COMBINES WITH RELATIVELY WEAK LAPSE RATES
TO YIELD MARGINAL DESTABILIZATION. STORM COVERAGE SHOULD GRADUALLY
INCREASE THROUGH THE AFTERNOON...EXPANDING SEWD ACROSS AR/NRN
LA/MS/NRN AL.

WHILE THE STRONGEST FLOW ALOFT WILL REMAIN WELL TO THE COOL SIDE OF
THE SURFACE FRONT...40 TO 50 KT WLYS AT MID-LEVELS SHOULD SPREAD
ATOP THE WARM SECTOR. THOUGH ONLY WEAK VEERING WITH HEIGHT IS
ANTICIPATED AS BOUNDARY-LAYER WIND FIELD SHOULD REMAIN SWLY AHEAD OF
THE FRONT...DEEP-LAYER SPEED SHEAR SHOULD INCREASE TO ROUGHLY 40 KT
ACROSS THIS REGION -- AMPLE FOR ORGANIZED/ROTATING STORMS. WHILE
DEGREE OF BOUNDARY-LAYER MOISTURE AND LOW-LEVEL SPEED SHEAR MAY
SUPPORT THE POTENTIAL FOR A TORNADO OR TWO...MAIN SEVERE THREAT IS
FORECAST TO BE LOCALLY-DAMAGING WINDS WITH SMALL-SCALE LINES OR
BOWING SEGMENTS.

AS STORMS CONTINUE ESEWD INTO GA AND SEWD ACROSS AL/MS THROUGH THE
EVENING...LOW-LEVEL COOLING/STABILIZATION SUGGESTS THAT SEVERE
THREAT SHOULD SLOWLY WANE...LIKELY DIMINISHING ALTOGETHER AFTER
MIDNIGHT.

.GOSS/GRAMS.. 11/14/2007

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