SWODY2
SPC AC 231701
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1101 AM CST WED DEC 23 2009
VALID 241200Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE LOWER MS
VALLEY TO THE NERN GULF COAST...
...SYNOPSIS...
A QUITE DYNAMIC LARGE-SCALE PATTERN IS EXPECTED TO CONTINUE THROUGH
THE DAY TWO PERIOD AS LARGE...DEEP-LAYER LOW IS ESTABLISHED OVER THE
CNTRL PART OF THE NATION. OF GREATEST INTEREST IS INTENSE VORTICITY
MAXIMUM AND ASSOCIATED 100+ KT MIDLEVEL JET STREAK WHICH WILL LIFT
RAPIDLY NEWD THROUGH THE ARKLATEX...MID SOUTH INTO THE OH VALLEY
WITH 12-HR 500 MB HEIGHT FALLS OF 150-200 M ALONG SYSTEM TRACK.
AT THE SURFACE...CYCLONE OVER THE ARKLATEX AT 24/12Z WILL UNDERGO
CONSIDERABLE DEEPENING WHILE DEVELOPING NNEWD THROUGH THE OZARKS AND
EVENTUALLY TO NEAR OR N OF THE MO/IA BORDER BY 25/12Z.
MEANWHILE...TRAILING COLD FRONT WILL SURGE FROM ERN TX EWD ACROSS
THE GULF COAST STATES. THIS BOUNDARY WILL SERVE AS THE PRIMARY
FOCUS FOR STRONG TO SEVERE TSTM DEVELOPMENT THROUGH THE DAY TWO
PERIOD.
...LOWER MS VALLEY TO THE NERN GULF COAST...
PERSISTENT AND PRONOUNCED SURFACE RIDGING FROM ONTARIO ESEWD ALONG
THE ATLANTIC COAST WILL CONTINUE TO LIMIT THE BREADTH AND NWD EXTENT
OF SYSTEM WARM SECTOR DESPITE THE RAPID DEEPENING OF SURFACE
CYCLONE. AS SUCH...EXPECT A WEDGE OF MODIFIED CONTINENTAL AIR TO
NARROW WITH TIME OWING TO PROGRESSIVE NATURE OF COLD FRONT WITH THE
STRONGEST INSTABILITY /I.E. MLCAPE OF GENERALLY LESS THAN 500 J PER
KG/ REMAINING CONFINED TO ALONG AND S OF THE I-10 CORRIDOR.
DESPITE THE LIMITED INSTABILITY...STRONG DEEP-LAYER ASCENT WITHIN
ZONE OF DCVA AHEAD OF MIDLEVEL VORTICITY MAXIMUM WILL LIKELY SUSTAIN
A NARROW BAND OF FORCED CONVECTION ALONG COLD FRONT. THE NRN
EXTENSION OF THIS BAND MAY REMAIN RATHER SHALLOW IN DEPTH AND
SLIGHTLY ELEVATED WHILE RAPIDLY LIFTING NEWD THROUGH THE I-40
CORRIDOR. GIVEN THE STRONG...AMBIENT WIND FIELD...DAMAGING WIND
GUSTS WILL BE POSSIBLE WITH ANY CONVECTIVE DOWNDRAFTS THAT CAN REACH
THE SURFACE.
CONVECTION SHOULD BECOME PROGRESSIVELY DEEPER AND MORE INTENSE WITH
SWD EXTENT ALONG THE BAND AS THE SRN FRINGE OF STRONGER HEIGHT
FALLS/DYNAMIC FORCING FOR ASCENT ACTS ON MORE MOIST/UNSTABLE
BOUNDARY LAYER. BOTH LOW AND DEEP-LAYER SHEAR WILL REMAIN RATHER
STRONG AND SUPPORTIVE OF SUPERCELLS AND/OR BOWING STRUCTURES
EMBEDDED WITHIN FORCED LINE. DAMAGING WINDS AND ISOLATED TORNADOES
WILL BE THE PRIMARY SEVERE WEATHER THREATS WITH THE MOST INTENSE
STORMS.
THE TORNADO/WIND THREAT WILL LIKELY NARROW WITH TIME TO THE
IMMEDIATE GULF COAST FRIDAY NIGHT AS PROGRESSIVE COLD FRONT OUTPACES
THE BETTER LOW-LEVEL MOISTURE RETURN.
..MEAD.. 12/23/2009
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