SWODY3
SPC AC 060818
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0218 AM CST THU DEC 06 2007
VALID 081200Z - 091200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
AMPLIFICATION WITHIN THE SOUTHERN BRANCH OF SPLIT POLAR WESTERLIES
APPEARS LIKELY TO CONTINUE THROUGH THIS FORECAST PERIOD.
CONSIDERABLE SPREAD EXISTS AMONG THE MODELS CONCERNING THE DETAILS
OF THE EMBEDDED SHORT WAVE IMPULSES. BUT...GUIDANCE GENERALLY
SUGGESTS THAT THE FIRST IMPULSE EMANATING FROM THE SOUTHWESTERN
TROUGH WILL ACCELERATE NORTHEAST OF THE CENTRAL ROCKIES EARLY
SATURDAY...THROUGH THE UPPER GREAT LAKES REGION BY LATE SATURDAY
NIGHT/EARLY SUNDAY. AT THE SAME TIME...THE PRIMARY UPSTREAM IMPULSE
IS FORECAST TO DIG SOUTH/SOUTHWESTWARD THROUGH SOUTHERN
CALIFORNIA...MAINTAINING THE POSITIVE TILT ORIENTATION OF THE LARGER
SCALE TROUGH...UPSTREAM OF AN UPPER RIDGE BUILDING THROUGH THE
SOUTHEASTERN STATES.
COLD AIR...REINFORCED BY NEW INTRUSIONS ASSOCIATED WITH
PERTURBATIONS IN THE NORTHERN STREAM...IS PROGGED TO LINGER ACROSS
MUCH OF THE NORTHERN TWO THIRDS OF THE NATION EAST OF THE ROCKIES.
AND...AS LOW-LEVEL WARMING OCCURS ACROSS THE SOUTH IN RESPONSE TO
DEVELOPMENTS IN THE SOUTHERN STREAM...A FRONTAL ZONE IS FORECAST TO
STRENGTHEN ACROSS THE SOUTHERN PLAINS RED RIVER VALLEY THROUGH THE
LOWER OHIO VALLEY AND SOUTHERN MID ATLANTIC STATES. A RETURN FLOW
OFF THE WESTERN GULF OF MEXICO WILL CONTINUE. BUT...THE MOISTENING
BOUNDARY LAYER TO THE SOUTH OF THE FRONTAL ZONE APPEARS LIKELY TO
REMAIN LARGELY CAPPED. AND...THIS WILL PROBABLY MINIMIZE SEVERE
POTENTIAL THROUGH EARLY SUNDAY.
..SOUTHERN PLAINS...
AN INCREASINGLY FAVORABLE ENVIRONMENT FOR SEVERE STORMS IS EXPECTED
TO DEVELOP TO THE SOUTH OF THE SURFACE FRONT BY LATE
SATURDAY...ACROSS MUCH OF CENTRAL INTO NORTHEAST TEXAS. SHEAR
BENEATH STRONG SOUTHWESTERLY MID/UPPER FLOW IS FORECAST TO BECOME
SUFFICIENT FOR SUPERCELLS...AS SURFACE DEW POINTS CLIMB THROUGH THE
LOWER/MID 60S...CONTRIBUTING TO MIXED LAYER CAPE OF 500-1000 J/KG.
BROAD ASCENT ASSOCIATED WITH WEAK LOW-LEVEL WARM ADVECTION IS ALSO
LIKELY THROUGH THE PERIOD. BUT...MID/UPPER FORCING NECESSARY TO
WEAKEN INHIBITION IS UNCERTAIN.
THERE IS INDICATION AMONG SOME MODEL GUIDANCE THAT THE INFLECTION
BETWEEN UPSTREAM TROUGH AND DOWNSTREAM RIDGE COULD SHIFT ACROSS
NORTH CENTRAL TEXAS SATURDAY NIGHT...WITH AN INCREASINGLY
DIFLUENT/DIVERGENT UPPER FLOW DOWNSTREAM. THIS COULD BECOME
SUPPORTIVE OF INCREASING CONVECTION...INCLUDING THUNDERSTORM
ACTIVITY...MOST LIKELY ALONG A SOUTHERLY LOW-LEVEL JET AXIS
EXTENDING ACROSS CENTRAL TEXAS INTO THE OZARK PLATEAU. THE BEST
CHANCE FOR STORMS IS PROBABLY IN THE ZONE OF STEEPER LOW-LEVEL
ISENTROPIC ASCENT...TO THE NORTH/COOL SIDE OF THE SURFACE FRONT.
BUT...WITH AT LEAST SOME POTENTIAL FOR STORMS INITIATING TO THE
SOUTH OF THE FRONT...ACROSS PARTS OF CENTRAL/NORTHEAST TEXAS...AT
LEAST LOW SEVERE PROBABILITIES APPEAR TO EXIST AT THE PRESENT TIME.
.KERR.. 12/06/2007
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