SWODY1
SPC AC 210556
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT SUN OCT 21 2007
VALID 211200Z - 221200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
LATEST MODEL SOLUTIONS ARE TRENDING TOWARD A SIMILAR SCENARIO FOR A
FULL LATITUDE TROUGH TO EVOLVE ACROSS THE CENTRAL U.S. THROUGH THE
DAY 1 FORECAST PERIOD AS MID/UPPER FLOW BECOMES HIGHLY AMPLIFIED.
THESE MODELS ARE ALSO INDICATING A SLOWER EWD PROGRESSION OF THIS
TROUGH THAN INDICATED BY EARLIER RUNS...WITH THE TROUGH EXTENDING
FROM CENTRAL CANADA SSWWD TO THE SRN HIGH PLAINS BY 12Z MONDAY.
LIKEWISE...THE NAM HAS CONTINUED TO SLOW THE EWD/SEWD PROGRESSION OF
THE COLD FRONT. THIS BOUNDARY SHOULD EXTEND FROM THE WRN GREAT
LAKES REGION SWWD THROUGH WRN MO TO CENTRAL OK AND INTO SWRN TX BY
22/00Z.
GREATEST PROBABILITY FOR WIDESPREAD TSTM COVERAGE AND SOME SEVERE
WEATHER THREAT LATE IN THE DAY 1 PERIOD EXISTS WITH THE NWD TRACK OF
A MID/UPPER LEVEL CIRCULATION CENTER AS IT MOVES INLAND ACROSS THE
CENTRAL/ERN GULF COAST STATES AHEAD OF THE AMPLIFYING TROUGH.
..LOWER MS VALLEY TO CENTRAL GULF COAST REGION...
SLY LOW LEVEL FLOW DEVELOPING FROM THE GULF INTO THE LOWER MS VALLEY
AND EWD INTO THE GULF COAST STATES DURING THE LATTER HALF OF THE
FORECAST PERIOD WILL ALLOW MOISTURE TO SPREAD NWD AND MOISTEN THE
EXISTING DRY AIR MASS AS INDICATED BY THE 00Z OBSERVED SOUNDINGS.
CONVECTION WITH EMBEDDED TSTMS ATTENDANT TO NWD MOVING GULF
CIRCULATION CENTER ARE EXPECTED TO APPROACH THE GULF COAST FROM SERN
LA TO FL PANHANDLE LATE THIS AFTERNOON. ACTIVITY SHOULD THEN SPREAD
FARTHER INLAND TONIGHT AND INCREASE IN COVERAGE WITHIN WARM CONVEYOR
BELT IN RESPONSE TO INCREASING ASCENT ATTENDANT TO HEIGHT FALLS
AHEAD OF APPROACHING UPPER TROUGH AND WITH INLAND TRACK OF GULF
IMPULSE. ALTHOUGH INSTABILITY SHOULD BE WEAK...AN ISOLATED TORNADO
THREAT WILL BE POSSIBLE IN THE VICINITY OF A BOUNDARY/WARM FRONT
MOVING NWD INTO SERN LA TO WRN FL PANHANDLE LATE THIS AFTERNOON.
STRENGTHENING SLY LLJ THIS EVENING MAY SUPPORT AN ISOLATED SEVERE
THREAT TO DEVELOP INLAND FROM THE COAST THROUGH TONIGHT.
..ERN TX NWD TO ERN KS/WRN MO...
SLOWER EWD MOTION OF COLD FRONT WILL ALLOW MORE TIME FOR BOUNDARY
LAYER MOISTURE TO INCREASE AHEAD OF THIS BOUNDARY...BUT POTENTIAL
FOR SURFACE BASED DEVELOPMENT IN SRN OK/NRN TX IS UNCERTAIN DUE TO
STRENGTH OF CAP /ELEVATED MIXED LAYER/ ADVECTING NEWD AHEAD OF THE
FRONT. GREATER POTENTIAL FOR TSTM DEVELOPMENT IS EXPECTED IN THE
POST-FRONTAL AIR MASS WHERE STRONGER UPPER FORCING WILL BE LOCATED
BEGINNING THIS EVENING THROUGH 12Z MONDAY.
.PETERS/CROSBIE.. 10/21/2007
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