Wednesday, November 21, 2007

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 211724
SWODY2
SPC AC 211721

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1121 AM CST WED NOV 21 2007

VALID 221200Z - 231200Z

..NO SVR TSTM AREAS FORECAST...

..SYNOPSIS...
BROADLY CYCLONIC FLOW WILL COVER MUCH OF WRN AND CENTRAL CONUS
THROUGH PERIOD. EMBEDDED SHORTWAVES WILL INCLUDE TROUGH NOW EVIDENT
IN MOISTURE CHANNEL IMAGERY AND PROFILER ANALYSES FROM WRN/CENTRAL
KS SWWD ACROSS TX PANHANDLE. THIS FEATURE SHOULD EJECT NEWD ACROSS
LH AND DOWN ST LAWRENCE VALLEY EARLY IN PERIOD...AS UPSTREAM
PERTURBATION NOW OVER MT DIGS SEWD DOWN MO RIVER VALLEY TOWARD
MKC/STL.

IN SRN STREAM...POSITIVELY TILTED SHORTWAVE TROUGH IS EVIDENT FROM
NRN LA SWWD ACROSS TX COASTAL PLAIN TO NERN MEX. THIS FEATURE IS
EXPECTED TO REMAIN AHEAD OF SFC COLD FRONT DESCRIBED BELOW...AS IT
MOVES ENEWD ACROSS GA/AL EARLY IN PERIOD...THEN OFFSHORE
GA/CAROLINAS BEFORE 23/00Z. UPSTREAM TROUGH -- NOW EVIDENT AS
CLOSED CYCLONE OFF SRN CA -- SHOULD MOVE EWD AND WEAKEN...REMAINING
WELL BEHIND SFC FRONT THROUGH PERIOD.

SFC COLD FRONT -- NOW ANALYZED FROM SRN IL SWWD ACROSS OZARKS AND TX
HILL COUNTRY -- WILL MOVE EWD AND SEWD FROM SRN APPALACHIANS DURING
DAY-2. ATTACHED/DIFFUSE SFC LOW IS ANALYZED OVER SRN MO ATTM...BUT
IS FCST TO REDEVELOP/MOVE NEWD AND STRENGTHEN AHEAD OF NRN STREAM
SHORTWAVE TROUGH. LOW SHOULD MOVE ENEWD FROM PA ACROSS MAINE DURING
FIRST HALF OF PERIOD.

..TIDEWATER REGION TO ERN GA...
WIDELY SCATTERED TO SCATTERED TSTMS ARE POSSIBLE ALONG/AHEAD OF SFC
FRONT...SOME OF WHICH MAY PRODUCE STG WIND GUSTS CAPABLE OF ISOLATED
DAMAGE. FACTORS PRECLUDING CATEGORICAL OUTLOOK ATTM INCLUDE WEAK
INSTABILITY AND LACK OF MORE ROBUST DEEP-LAYER SHEAR...HOWEVER SOME
SUBSET OF SWATH FROM MID ATLANTIC TO GA MAY NEED HIGHER
PROBABILITIES IN LATER OUTLOOKS IF EITHER OF THOSE FACTORS APPEARS
TO BE MORE FAVORABLE.

DEEP-LAYER WIND PROFILES AHEAD OF FRONT ARE FCST TO BE NEARLY
UNIDIRECTIONAL THROUGH MOST OF TROPOSPHERE...INCLUDING SFC SWLYS
OVER MAJORITY OF WARM SECTOR. ALTHOUGH THIS WILL LIMIT NEAR-FRONTAL
CONVERGENCE...WEAKNESS OF SBCINH STILL SHOULD PERMIT SFC-BASED
DEVELOPMENT WHEREVER POCKETS OF ENHANCED HEATING CAN OCCUR. WHILE
DIRECTIONAL SHEAR WILL BE VERY LIMITED...35-45 KT 850 MB WINDS ARE
EXPECTED FROM NEAR GA/SC BORDER NEWD INTO MID-ATLANTIC REGION...WITH
ENOUGH LOW LEVEL BULK SHEAR TO SUPPORT SOME POTENTIAL FOR
ORGANIZATION WITH ANY SUSTAINED/SFC-BASED ACTIVITY.
MEANWHILE...BUOYANCY AHEAD OF SFC FRONT WILL BE
LIMITED...PARTICULARLY WITH NEWD EXTENT AWAY FROM GULF COAST...BY
1. PRESENCE OF MRGLLY UNSTABLE AMBIENT LAPSE RATES IN MID/UPPER
LEVELS AND
2. LIKELIHOOD OF BROAD BELT OF MULTILEVEL CLOUDS WITH EMBEDDED AREAS
OF PRECIP...RESTRICTING DIURNAL/DIABATIC HEATING.

SVR POTENTIAL WILL DIMINISH FARTHER NE ACROSS MID-ATLANTIC BECAUSE
OF LACK OF INSTABILITY...AND FARTHER SW TOWARD ERN GULF COAST AND
NRN FL BECAUSE OF WEAKER SHEAR AND LIFT.

.EDWARDS.. 11/21/2007

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