DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 130552
SWODY2
SPC AC 130550

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1150 PM CST WED DEC 12 2012

VALID 141200Z - 151200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
MODELS INDICATE THAT STRONG UPPER JET INTENSIFICATION WILL CONTINUE
IN A BROAD WEST SOUTHWESTERLY ANTICYCLONIC ARC ACROSS THE CENTRAL
AND SOUTHERN TIER OF THE U.S. DURING THIS PERIOD. ALTHOUGH THE
SPREAD AMONG THE VARIOUS MODELS AND MODEL ENSEMBLES REMAINS LARGE
CONCERNING THE SHORT WAVE IMPULSE EXPECTED TO DIG TOWARD THE
SOUTHERN CALIFORNIA COAST...A STRONG DOWNSTREAM SHORT WAVE
TROUGH/CLOSED LOW APPEARS LIKELY TO ACCELERATE NORTHEASTWARD OUT OF
THE SOUTHERN U.S./NORTHWESTERN MEXICAN PLATEAU REGION. THIS LATTER
FEATURE...WITH A 90-100 KT 500 MB SPEED MAXIMUM...IS FORECAST TO
FLATTEN AMPLIFIED CENTRAL/SOUTHERN PLAINS SHORT WAVE RIDGING AS IT
PROGRESSES ACROSS THE ROCKIES TOWARD THE MID AND LOWER MISSOURI
VALLEY...ACCOMPANIED BY SIGNIFICANT SURFACE CYCLOGENESIS INITIATING
OVER SOUTHEASTERN COLORADO BY FRIDAY AFTERNOON.

WHILE THIS SHOULD RESULT IN CONSIDERABLE STRENGTHENING OF SOUTHERLY
850 MB FLOW /40-60+ KT/ ACROSS THE SOUTHERN PLAINS AND OZARK PLATEAU
FRIDAY AFTERNOON INTO FRIDAY NIGHT...SUBSTANTIVE MOISTURE RETURN OFF
THE WESTERN GULF OF MEXICO IS EXPECTED TO BE SLOW TO OCCUR. ALONG A
DEVELOPING DRY LINE ACROSS THE HIGH PLAINS...MID 50S SURFACE DEW
POINTS MAY NOT REACH WEST CENTRAL AND NORTHWEST TEXAS BEFORE
SUNSET...WITH BOUNDARY LAYER MOISTURE CHARACTERIZED BY 60F+ DEW
POINTS SLOW TO ADVECT NORTH OF CENTRAL TEXAS OVERNIGHT. DAYTIME
HEATING MAY BE SUFFICIENT TO CONTRIBUTE TO BOUNDARY LAYER
DESTABILIZATION ALONG THE DRY LINE ACROSS THE CENTRAL AND SOUTHERN
HIGH PLAINS...BUT LOW/MID AND HIGH-LEVEL CLOUD COVER...AND PERHAPS
WEAK EARLY PERIOD CONVECTIVE DEVELOPMENT...MAY FURTHER HAMPER
DESTABILIZATION ACROSS THE CENTRAL AND SOUTHERN PLAINS.

...CNTRL/SRN HIGH PLAINS INTO PARTS OF THE OZARK PLATEAU...
ALTHOUGH THERMODYNAMIC PROFILES EVIDENT IN MOST POINT FORECAST
SOUNDINGS SUGGEST THAT EVEN 5 PERCENT SEVERE PROBABILITIES MAY BE
FAIRLY GENEROUS...LOW SEVERE PROBABILITIES ARE BEING MAINTAINED
BASED LARGELY ON THE STRENGTH OF THE UPPER IMPULSE AND DEVELOPING
SURFACE CYCLONE. IN FACT...THE SEVERE PROBABILITY AREA FROM THE
PRIOR OUTLOOK FOR THIS PERIOD HAS BEEN EXPANDED TO THE NORTHWEST TO
ACCOUNT FOR POSSIBLE LATE AFTERNOON STORM INITIATION ALONG THE DRY
LINE ACROSS THE EASTERN TEXAS AND OKLAHOMA PANHANDLES INTO PARTS OF
SOUTHWEST KANSAS. EVEN WITH SURFACE DEW POINTS IN THE UPPER
40S/NEAR 50F...NAM FORECAST SOUNDINGS SUGGEST THAT BOUNDARY LAYER
DESTABILIZATION COULD BECOME SUFFICIENT FOR LOW TOPPED THUNDERSTORMS
AS STRONG DYNAMIC FORCING FOR UPWARD VERTICAL MOTION IN THE EXIT
REGION OF THE APPROACHING JET STREAK OVERSPREADS THE REGION. IN THE
PRESENCE OF STRONG SHEAR... SUPERCELLS ARE POSSIBLE...AND A TORNADO
OR TWO MAY NOT BE OUT OF THE QUESTION.

INTO THE EVENING AND OVERNIGHT HOURS...SEVERE POTENTIAL BECOMES MORE
UNCLEAR. LARGE-SCALE FORCING IS EXPECTED TO SUPPORT HIGHEST
THUNDERSTORM PROBABILITIES ACROSS THE CENTRAL PLAINS INTO THE
MISSOURI VALLEY...WHILE THE STRONGEST POTENTIAL WARM SECTOR
DESTABILIZATION /ALBEIT STILL FAIRLY WEAK...AND MOSTLY BASED ABOVE A
NEAR SURFACE STABLE LAYER/ OCCURS ACROSS THE SOUTHERN PLAINS.

..KERR.. 12/13/2012

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