SWODY2
SPC AC 170545
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1145 PM CST FRI JAN 16 2009
VALID 181200Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
HIGH-AMPLITUDE UPPER AIR PATTERN FCST THROUGH DAY-2...FEATURING STG
ANTICYCLONE OVER NWRN CONUS AND SWRN CANADA...AND TROUGHING
DOWNSTREAM FROM GREAT LAKES SWD TO SRN APPALACHIANS AND NERN GULF.
SHORTWAVE TROUGH -- NOW DIGGING SEWD ACROSS NRN PLAINS AND UPPER
MIDWEST -- IS FCST TO PIVOT CYCLONICALLY EWD OVER UPPER GREAT LAKES
AND OH VALLEY DAY-1...LEADING TO 500 MB LOW OVER LH BY 18/12Z.
MEANWHILE...SHORTWAVE TROUGHS AND ATTENDANT VORTICITY MAXIMA -- NOW
EVIDENT IN MOISTURE CHANNEL IMAGERY AND UPPER AIR ANALYSES OVER
NUNAVUT -- WILL MOVE SSEWD ACROSS UPPER MS VALLEY...LIKEWISE
PIVOTING EWD THROUGH BASE OF MEAN TROUGH OVER OH VALLEY AND AROUND
SRN RIM OF LH CYCLONE. MID-UPPER LOW THEN SHOULD MOVE EWD ACROSS
PORTIONS SRN ONT BY END OF PERIOD.
AT SFC...PRONOUNCED TROUGH AND ACCOMPANYING COLD FRONT SHOULD MOVE
SEWD FROM TX COASTAL PLAIN INTO NRN/WRN GULF...AND EWD ACROSS TN
VALLEY AND CAROLINAS...DURING DAY-2 PERIOD. WEAK FRONTAL-WAVE
CYCLONE MAY DEVELOP DURING 19/00Z-19/06Z TIME FRAME OVER
CAROLINAS...IN RESPONSE TO SHORTWAVE TROUGH TURNING EWD FROM
MID/LOWER MS VALLEY ACROSS SRN APPALACHIANS.
...SERN CONUS...
FROM SERN LA TO SRN AL AND FL PANHANDLE...ISOLATED TO WIDELY
SCATTERED TSTMS MAY DEVELOP DURING FIRST HALF OF PERIOD ALONG OR
JUST AHEAD OF SFC COLD FRONT. ENVIRONMENT OF WEAK LAPSE RATES AND
INCOMPLETELY MODIFIED/LOW-LEVEL RETURN FLOW AIR MASS WILL RESULT IN
MRGL BUOYANCY...WITH MUCAPE REMAINING AOB 300 J/KG MOST AREAS. WITH
50-60 KT WINDS EXPECTED AROUND 500 MB OVER THIS SEGMENT OF FRONTAL
ZONE...DEEP-LAYER SPEED SHEAR WILL BE FAVORABLE FOR SVR.
HOWEVER...SWLY PREFRONTAL SFC WINDS WILL LIMIT BOTH FRONTAL
CONVERGENCE AND DIRECTIONAL SHEAR SIGNIFICANTLY. ATTM...SVR THREAT
APPEARS TOO ISOLATED AND CONDITIONAL TO INTRODUCE AOA 5-PERCENT
PROBABILITIES.
SCATTERED TSTMS MAY DEVELOP AHEAD OF FRONT DURING LATTER HALF OF
PERIOD...OVER GULF STREAM WATERS E OF CAROLINAS...WHERE INCREASING
LOW LEVEL THETAE WILL SUPPORT FAVORABLE CAPE. THIS ACTIVITY SHOULD
REMAIN OFFSHORE.
..EDWARDS.. 01/17/2009
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