DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 230557
SWODY1
SPC AC 230554

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1154 PM CST MON DEC 22 2008

VALID 231200Z - 241200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
UPPER TROUGH INITIALLY OVER THE ROCKIES WILL BE KICKED EWD INTO THE
CENTRAL U.S. THROUGH THE END OF THE PERIOD BY A SECOND TROUGH
DIGGING QUICKLY SEWD ACROSS THE ERN PACIFIC.

AS THE INITIAL UPPER TROUGH SHIFTS EWD...A SURFACE LOW INVOF THE
TX/OK PANHANDLE REGION DURING THE AFTERNOON SHOULD MOVE ENEWD ALONG
THE SURFACE BAROCLINIC ZONE WITH TIME. BY THE END OF THE PERIOD
THIS LOW SHOULD RESIDE INVOF MO...WITH THE TRAILING COLD FRONT
EXTENDING ACROSS OK/NRN AND WRN TX.

...FAR ERN TX/NRN AND WRN LA/SERN AR/W CENTRAL MS...
A LARGE ZONE OF SLY LOW-LEVEL FLOW AND RESULTING STRONG WARM
ADVECTION IS FORECAST ACROSS THE CENTRAL THIRD OF THE COUNTRY THIS
PERIOD...AHEAD OF THE ADVANCING STORM SYSTEM. MODELS FORECAST
AGGRESSIVE LOW-LEVEL MOIST ADVECTION AS WELL...THOUGH ONSHORE
DEWPOINTS REMAIN QUITE LOW ACROSS THE GULF COAST REGION ATTM --
RANGING FROM THE 40S IN COASTAL S TX TO THE 20S ACROSS SRN LA.

THOUGH IT WOULD APPEAR THAT THE DEGREE OF MOIST RETURN INTO THE
LOWER MS VALLEY REGION IS OVERDONE IN THE MODELS...SREF DATA
INDICATES 90% PROBABILITY OF 60 DEGREE DEWPOINTS REACHING NRN
LA/CENTRAL MS BY THE END OF THE PERIOD.

PRESUMING THIS DEGREE OF MOISTURE RETURN...CAPE WOULD LIKELY BECOME
MINIMALLY-SUFFICIENT FOR A FEW THUNDERSTORMS TO EVOLVE OUT OF
WIDESPREAD SHOWERS INCREASING THROUGH THE PERIOD AS A RESULT OF
PERSISTENT WARM ADVECTION/ISENTROPIC LIFT. GIVEN SURFACE-BASED
STORMS...DEGREE OF SHEAR -- FORECAST TO BE QUITE SUFFICIENT FOR
ORGANIZATION/LOW-LEVEL ROTATION -- WOULD SUPPORT A RISK FOR AN
ISOLATED TORNADO OR TWO ALONG WITH LOCALLY-GUSTY WINDS.

WHILE IT IS ANTICIPATED THAT MODELS ARE OVERDONE WITH BOTH THE
DEGREE OF MOISTURE RETURN FORECAST...AND THAT WIDESPREAD
PRECIPITATION WILL HINDER ANY POTENTIAL FOR EVEN MODEST
DESTABILIZATION...SEVERE THREAT APPEARS MINIMAL.
NONETHELESS...OWING TO SREF CERTAINTIES OF 60-PLUS DEGREE DEWPOINTS
AND 250 TO 500 J/KG MOST-UNSTABLE CAPE...WILL MAINTAIN A
LOW-PROBABILITY SEVERE POTENTIAL FROM THIS AFTERNOON THROUGH THE
OVERNIGHT HOURS.

..GOSS.. 12/23/2008

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