DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 230830
SWODY3
SPC AC 230829

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0229 AM CST SUN DEC 23 2012

VALID 251200Z - 261200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN
PLAINS...LOWER MS VALLEY AND CNTRL GULF COAST STATES...

...GULF COAST STATES...
AN IMPRESSIVE UPPER-LEVEL SYSTEM IS FORECAST TO MOVE EWD INTO THE
SRN PLAINS EARLY TUESDAY MORNING AS THE EXIT REGION OF A POWERFUL
MID-LEVEL JET MOVES INTO THE GULF COAST STATES. AHEAD OF THE
SYSTEM...MOISTURE IS FORECAST TO RETURN NWD INTO THE LOWER MS VALLEY
AND CNTRL GULF COAST STATES WITH MODERATE INSTABILITY DEVELOPING
ACROSS THE SRN AND WRN PART OF THE SLIGHT RISK AREA EARLY IN THE DAY
ON TUESDAY. A CLUSTER OF THUNDERSTORMS OR SQUALL-LINE MAY BE ALREADY
DEVELOPED BY DAYBREAK ON TUESDAY ACROSS EAST TX WITH ADDITIONAL
STORMS POSSIBLY ONGOING ACROSS THE LOWER MS VALLEY. MODEL FORECASTS
INCREASE CONVECTIVE COVERAGE ACROSS THE LOWER MS VALLEY AND APPEAR
TO MOVE A WELL-DEVELOPED MCS EWD ACROSS THE REGION DURING THE DAY.

FORECAST SOUNDINGS AT MIDDAY TUESDAY IN THE LOWER MS VALLEY DEVELOP
AN IMPRESSIVE SHEAR ENVIRONMENT AS THE MID-LEVEL JET APPROACHES THE
REGION FROM THE WEST. NAM FORECAST SOUNDINGS VALID TUESDAY AT 21Z
JUST SOUTHWEST OF JACKSON MS SHOW MLCAPE VALUES AROUND 1500 J/KG
WITH ABOUT 60 KT OF DEEP LAYER SHEAR. THIS COMBINED WITH 0-3 KM
STORM RELATIVE HELICITIES AROUND 400 M2/S2 COULD BE FAVORABLE FOR
SUPERCELLS AND TORNADOES. IF MANY CELLS CAN REMAIN DISCRETE...THEN
CONDITIONS COULD ALSO BE FAVORABLE FOR STRONG TORNADOES AS THE
LOW-LEVEL JET MOVES EWD ACROSS THE CNTRL GULF COAST STATES FROM
TUESDAY MORNING INTO THE AFTERNOON. AT THIS POINT...THE POTENTIAL
FOR WIDESPREAD WIND DAMAGE APPEARS JUST AS VIABLE. THE MAGNITUDE OF
THESE THREATS MAY DEPEND UPON THE DOMINANT STORM MODE. IF THE
FAVORED MODE ENDS UP BEING LINEAR...THEN WIND DAMAGE COULD BE THE
GREATER THREAT.

FORECAST SOUNDINGS ACROSS THE LOWER MS VALLEY AND CNTRL GULF COAST
STATES TUESDAY INTO TUESDAY NIGHT SHOW POTENTIAL FOR A SUBSTANTIAL
SEVERE WEATHER EVENT. THE COMBINATION OF SHEAR AND INSTABILITY
COMBINED WITH A POTENT WEATHER SYSTEM SUGGESTS A 30 PERCENT
PROBABILITY AND SIGNIFICANT SEVERE HATCHED AREA ARE WARRANTED. THE
SEVERE THREAT SHOULD CONTINUE INTO TUESDAY EVENING AND POSSIBLY INTO
THE OVERNIGHT PERIOD AS THE UPPER-LEVEL TROUGH MOVES QUICKLY EWD
ACROSS THE GULF COAST STATES.

..BROYLES.. 12/23/2012

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