DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 240548
SWODY1
SPC AC 240545

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1145 PM CST SUN NOV 23 2008

VALID 241200Z - 251200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...

MID/UPPER-LEVEL LOW OVER MANITOBA/WRN ONTARIO AS OF 24/05Z WILL
DEVELOP SEWD THROUGH THE GREAT LAKES...RESULTING IN OVERALL
INTENSIFICATION OF LONGWAVE TROUGH OVER THE ERN HALF OF THE NATION.
AN EMBEDDED SHORT WAVE TROUGH /CURRENTLY MOVING THROUGH THE CNTRL
PLAINS/ WILL PRECEDE THIS UPPER LOW EWD THROUGH THE TN/OH
VALLEYS...EVENTUALLY REACHING THE MID ATLANTIC COAST BY TUESDAY
MORNING.

IN THE LOW LEVELS...PRIMARY SURFACE CYCLOGENESIS WILL COINCIDE WITH
THE TRACK OF UPPER LOW OVER THE OH VALLEY INTO LOWER GREAT LAKES.
TRAILING COLD FRONT WILL SURGE EWD FROM THE MID MS VALLEY TO ALONG
THE MID ATLANTIC COAST BY THE END OF THE PERIOD. THE SWRN EXTENSION
OF THIS BOUNDARY WILL MOVE MORE SLOWLY SEWD THROUGH THE GULF COAST
STATES.

...LOWER MS VALLEY...

A BAND OF ELEVATED TSTMS IS EXPECTED TO BE ONGOING AT THE ONSET OF
THE FORECAST ALONG AND/OR IN ADVANCE OF SURFACE COLD FRONT FROM THE
ARKLATEX INTO LOWER OH VALLEY. WHILE PRE-FRONTAL AIR MASS IS
EXPECTED TO BE ONLY MARGINALLY UNSTABLE...DEEP-LAYER ASCENT FOCUSED
ALONG SRN FRINGE OF ABOVE-MENTIONED SHORT WAVE TROUGH SHOULD
MAINTAIN THESE ELEVATED STORMS THROUGH THE MORNING OVER PORTIONS OF
ERN TX INTO THE LOWER MS VALLEY.

WHILE SWLY LLJ WILL GRADUALLY DEVELOP NEWD AWAY FROM THE REGION...
PERSISTENT SLY/SWLY FLOW WITHIN PRE-FRONTAL WARM SECTOR WILL
CONTINUE TO SUPPORT THE NWD FLUX OF UPPER 50S/LOWER 60S DEWPOINTS
INTO LA AND SRN MS. IN SPITE OF THE MOISTURE INCREASE...LATEST
MODEL GUIDANCE REMAINS CONSISTENT IN SUGGESTING THAT CONSIDERABLE
CLOUDINESS WILL TEND TO LIMIT DAYTIME HEATING AND RESULTANT AIR MASS
DESTABILIZATION WITH MLCAPE AOB 500 J/KG.

THE COMBINATION OF MESOSCALE CONVERGENCE ALONG COLD FRONT AND
BROADER-SCALE ASCENT INTO RIGHT ENTRANCE REGION OF UPPER-LEVEL JET
STREAK ARE EXPECTED TO CONTRIBUTE TO AN INCREASE IN SURFACE-BASED
STORM DEVELOPMENT BY AFTERNOON FROM SERN TX INTO PARTS OF LA AND MS.
THE WEAK LAPSE RATES AND RESULTANT INSTABILITY ARE EXPECTED TO LIMIT
A MORE ORGANIZED SEVERE WEATHER THREAT. HOWEVER...THE PRESENCE OF
30-35 KT OF DEEP-LAYER SHEAR SUGGESTS THE POTENTIAL FOR A FEW
PERSISTENT/ROTATING UPDRAFTS EMBEDDED WITHIN LARGER CONVECTIVE
CLUSTER. LOCALLY STRONG WIND GUSTS APPEAR TO BE THE PRIMARY HAZARD
WITH ANY MORE INTENSE STORMS...THOUGH A BRIEF TORNADO CANNOT BE
RULED OUT GIVEN 20-25 KT OF 0-1 KM SHEAR.

..MEAD/BRIGHT.. 11/24/2008

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