SWODY2
SPC AC 171707
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1207 PM CDT WED SEP 17 2008
VALID 181200Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
IN MID-UPPER LEVELS...MEAN ERN TROUGH/WRN RIDGE PATTERN WILL BE
MAINTAINED THROUGH PERIOD...BUT WITH LOWER AMPLITUDE THAT AT
PRESENT. RIDGING SHOULD EXTEND FROM OH VALLEY WNWWD TOWARD ID.
PERSISTENT/QUASISTATIONARY/DIFFUSE UPPER TROUGH AND CYCLONIC SHEAR
ZONE WILL EXTEND FROM CO SEWD ACROSS TX PANHANDLE...MS...AND NERN
FL/SERN GA. WEAK LOW MAY DEVELOP ALONG THIS TROUGH OVER SRN HIGH
PLAINS. FARTHER W...MID-UPPER LEVEL LOW -- NOW EVIDENT IN MOISTURE
CHANNEL IMAGERY INVOF 43N138W -- IS EXPECTED TO MOVE EWD TOWARD NRN
CA/SRN ORE COAST. STG CONSENSUS EXISTS AMONG LATEST OPERATIONAL
GUIDANCE AND SREF MEMBERS WITH THIS LOW BEING JUST OFFSHORE NWRN CA
AT 19/12Z. ALTHOUGH NRN STREAM JET MAX SHOULD REMAIN N OF CANADIAN
BORDER...SRN STREAM UPPER JET -- WITH 55-65 KT FLOW AT 250 MB -- IS
EXPECTED TO EXTEND FROM NERN MEX EWD ACROSS S TX AND NRN GULF...THEN
SEWD OVER SERN GULF.
AT SFC...PERSISTENT FRONTAL ZONE NOW OVER NRN FL IS EXPECTED TO
DRIFT SWD OVER NRN/CENTRAL FL THEN BECOME QUASISTATIONARY...WITH
WEAK FRONTAL-WAVE DEVELOPMENT POSSIBLE OVER CENTRAL/NERN GULF. SFC
COLD FRONT -- NOW ANALYZED FROM NRN QUE SWWD ACROSS LH AND LOWER MI
AND CENTRAL IA -- IS EXPECTED TO MOVE OFFSHORE NEW ENGLAND AND OVER
MID-ATLANTIC REGION THIS PERIOD...BECOMING DIFFUSE AMIDST BUILDING
SFC ANTICYCLONE AND NLY WINDS ON BOTH SIDES OF FRONT. BY
19/00Z...ANTICYCLONE SHOULD BE CENTERED INVOF SERN ONT/SWRN
QUE...WITH PRONOUNCED RIDGING SWWD ACROSS SRN PLAINS AND LOWER RIO
GRANDE VALLEY. ASSOCIATED CONTINENTAL TRAJECTORIES WILL PRECLUDE
SUBSTANTIAL MOISTENING OVER MOST OF CONUS E OF ROCKIES NW OF FL/GULF
FRONTAL ZONE.
...SERN CONUS...
WIDELY SCATTERED TO SCATTERED TSTMS ARE POSSIBLE WITHIN AND S OF
FRONTAL ZONE. GREATEST COVERAGE IS EXPECTED DURING AFTERNOON AS STG
SFC HEATING AND SFC DEW POINTS LOW-MID 70S F OFFSET MODEST LAPSE
RATES ALOFT...TO YIELD MLCAPES 1000-2000 J/KG. STRONGEST UPPER
LEVEL FLOW IS FCST TO REMAIN W OF THIS AREA ACROSS GULF...LIMITING
ORGANIZATION OF MULTICELLULAR CONVECTION AND RESTRICTING SVR
POTENTIAL. SMALLER SCALE EFFECTS SUCH AS BOUNDARY INTERSECTIONS MAY
YIELD ENHANCED/LOCALIZED POTENTIAL FOR STG GUSTS...BUT ORGANIZED SVR
POTENTIAL APPEARS TOO WEAK/CONDITIONAL FOR PROBABILITIES AOA 5
PERCENT.
...WRN CONUS...
WIDELY SCATTERED TSTMS SHOULD DEVELOP AMIDST STEEP LOW-MIDLEVEL
LAPSE RATES AND POCKETS OF AT LEAST MRGL LOW LEVEL
MOISTURE...PRIMARILY OVER HIGHER TERRAIN DURING MID-LATE AFTERNOON
HEATING. ADDITIONALLY...WEAK COLD FRONT IS FCST TO MOVE EWD OVER
DAKOTAS AND NRN MN...BUT AIR MASS SHOULD BE TOO DRY/CAPPED TO
SUPPORT APPRECIABLE THUNDER POTENTIAL EXCEPT INVOF TRAILING PORTION
OF FRONT OVER N-CENTRAL HIGH PLAINS AND BLACK HILLS. WEAK
LOW-MIDLEVEL WINDS AND LACK OF VERTICAL SHEAR WILL LIMIT
ORGANIZATION OF THIS ACTIVITY...HOWEVER WELL-MIXED SUBCLOUD LAYER
MAY FOSTER LOCALIZED STG GUSTS.
..EDWARDS.. 09/17/2008
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