Wednesday, December 21, 2011

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 211645
SWODY2
SPC AC 211644

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1044 AM CST WED DEC 21 2011

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF LA/MS/AL...

CURRENT WATER VAPOR IMAGERY SHOWS A WELL-DEFINED SHORTWAVE TROUGH
OVER NORTHWEST MEXICO. THIS FEATURE WILL TRACK EAST-NORTHEASTWARD
ACROSS SOUTH TX TONIGHT AND INTO THE LOWER MS VALLEY ON THURSDAY. A
SURFACE BOUNDARY IS CURRENTLY STALLED JUST OFF THE LA/MS COAST...AND
SHOULD RAPIDLY RETURN NORTHWARD TONIGHT AS SOUTHERLY LOW LEVEL WINDS
STRENGTHEN AHEAD OF THE APPROACHING THROUGH. BY 22/12Z...THE
BOUNDARY IS EXPECTED TO EXTEND FROM SOUTHERN LA INTO CENTRAL MS AND
NORTHERN AL. SURFACE DEWPOINTS IN THE MID 60S WILL ALSO RETURN
NORTHWARD INTO LA/MS/AL LEADING TO THE DEVELOPMENT OF AT LEAST
MARGINAL SURFACE-BASED INSTABILITY ALONG AND SOUTH OF THE FRONT.

MODEL SOLUTIONS ARE IN GENERAL AGREEMENT THAT SURFACE CYCLOGENESIS
WILL BE OCCURRING AT THE BEGINNING OF THE FORECAST PERIOD OVER
LA/MS. THE DEEPENING LOW WILL TRACK INTO NORTHERN AL BY AFTERNOON.
DESPITE ONLY MARGINAL CAPE...BACKING AND STRENGTHENING LOW LEVEL
WIND FIELDS COUPLED WITH STRONG LARGE SCALE FORCING FOR
ASCENT...WILL PROMOTE A RISK OF STRONG TO LOCALLY SEVERE STORMS.
SUPERCELLS APPEAR TO BE THE MOST LIKELY STORM-MODE WITH DAMAGING
WINDS AND ISOLATED TORNADOES POSSIBLE. LOW LEVEL MOISTURE AND
INSTABILITY WILL WEAKEN WITH NORTHEASTWARD EXTENT INTO TN/GA WITH
DIMINISHING SEVERE WEATHER THREATS.

..HART.. 12/21/2011

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