Post by Briella - Houma on Dec 24, 2012 11:36:43 GMT -6
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1122 AM CST MON DEC 24 2012
VALID 251200Z - 261200Z
...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF LA...CENTRAL/SRN
MS...AND WRN AL...
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN TX ACROSS THE GULF
COAST/LOWER MS VALLEY AND SRN APPALACHIANS...
...SIGNIFICANT SEVERE WEATHER EVENT EXPECTED FOR CHRISTMAS DAY OVER
PARTS OF THE GULF COAST STATES...
...SYNOPSIS...
AN ENERGETIC FLOW PATTERN IS EVIDENT IN SATELLITE IMAGERY FROM THE
EASTERN PACIFIC ACROSS THE CONUS AS A SERIES OF VIGOROUS UPPER
TROUGHS PROGRESS EWD. THE PRIMARY SYSTEM ASSOCIATED WITH A MAJOR
SEVERE WEATHER THREAT TOMORROW IS CURRENTLY OVER THE GREAT BASIN.
WITH LATEST UPPER AIR DATA INDICATING THE STRONGEST MID/UPPER LEVEL
WINDS DIGGING INTO THE SWRN PORTION OF THE TROUGH...MODEL CONSENSUS
INDICATES THE SYSTEM WILL AMPLIFY/DEVELOP INTO A PROGRESSIVE CLOSED
LOW MOVING ACROSS THE SRN PLAINS DURING THE DAY REACHING THE MIDDLE
MS VALLEY BY 26/12Z. AT THE SURFACE...A BROAD LOW PRESSURE REGION
OVER CENTRAL/ERN TX EARLY IN THE PERIOD IS FORECAST TO CONSOLIDATE
INTO A DEEPENING LOW MOVING ACROSS NRN LA DURING THE AFTERNOON AND
CONTINUING INTO MIDDLE TN BY THE END OF THE PERIOD. AN EAST-WEST
ORIENTED WARM FRONT FROM SERN TX ACROSS THE SRN PARTS OF MS/AL AND
GA WILL SLOWLY LIFT NWD AS THE LOW MOVES NEWD...WHILE A COLD FRONT
EXTENDING SWWD FROM THE LOW IS EXPECTED TO ACCELERATE EWD
/ESPECIALLY DURING THE NIGHT/ ACROSS THE LOWER MS VALLEY REACHING AL
BY 26/12Z.
...GULF COAST REGION/LOWER MS VALLEY...
AREAS OF STRONG/SEVERE THUNDERSTORMS ARE EXPECTED TO BE ONGOING FROM
ERN TX INTO THE LOWER MS VALLEY AT THE START OF THE PERIOD AS
INTENSE LARGE SCALE ASCENT IN THE LEFT EXIT REGION OF THE UPPER
LEVEL JET COINCIDES WITH FOCUSED LOW LEVEL CONVERGENCE/WARM
ADVECTION ALONG/NORTH OF THE WARM FRONT. SOUTH OF THE WARM
FRONT...SURFACE DEW POINTS IN THE LOW/MID 60S F WILL BE RETURNING
NWD ACROSS A BROAD WARM SECTOR EXTENDING ACROSS MUCH OF THE GULF
COAST REGION. THIS WILL CONTRIBUTE TO AN UNSTABLE ENVIRONMENT WITH
MLCAPE RANGING FROM 1000-1250 J/KG NEAR THE COAST TO AOB 500 J/KG
NORTH OF THE WARM FRONT.
STRONG WINDS IN THE MID AND UPPER LEVELS /70-90 KT AT 500 MB AND
110+ KT AT 250 MB/ WILL RESULT IN DEEP LAYER SHEAR SUPPORTIVE OF
ROTATING UPDRAFTS...INCLUDING ELEVATED SUPERCELLS NORTH OF THE WARM
FRONT. AS THE DAY PROGRESSES...FORCED ASCENT ALONG THE ADVANCING
COLD FRONT IS EXPECTED TO RESULT IN QLCS DEVELOPMENT CONTAINING
EMBEDDED FAST-MOVING BOW ECHOES AND POSSIBLE
SUPERCELLS/MESO-VORTICES AS IT MOVES EWD ACROSS LA AND THE SRN HALF
OF SRN MS. THERE WILL ALSO BE CONTINUED POTENTIAL FOR A FEW
DISCRETE SUPERCELLS IN THE WARM SECTOR AND ALONG THE WARM FRONT
AHEAD OF THE QLCS. LOW LCL HEIGHTS AND CLOCKWISE TURNING LOW LEVEL
HODOGRAPHS /SRH VALUES OF 200-400 M2 PER S2/ INDICATE POTENTIAL FOR
TORNADIC SUPERCELLS. THE POSSIBILITY EXISTS FOR SEVERAL LONG-TRACK
STRONG TORNADOES ASSOCIATED WITH ANY LONG-LIVED FAST-MOVING
SUPERCELLS...ALONG WITH MORE WIDESPREAD DAMAGING WINDS ALONG THE
MOST INTENSE PARTS OF THE BOWING QLCS. DESPITE GRADUALLY DECREASING
INSTABILITY AS BOUNDARY LAYER COOLING OCCURS AFTER DARK...A SEVERE
THREAT IS EXPECTED TO SPREAD EWD/NEWD ACROSS PARTS OF AL...SRN TN
AND WRN GA DURING THE NIGHT AS THE SYSTEM CONTINUES TO STRENGTHEN.I
