DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 080601
SWODY2
SPC AC 080600

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1200 AM CST SAT DEC 08 2012

VALID 091200Z - 101200Z

...THERE IS A SLGT RISK OF SVR TSTMS LATE SUN AFTN AND SUN EVE
ACROSS PARTS OF CNTRL/SRN AND ERN AR...NE TX...NRN LA...NW MS AND
WRN TN...

...SYNOPSIS...
WITHIN LARGE-SCALE UPPER TROUGHING ENCOMPASSING MUCH OF INTERIOR
NORTH AMERICA...IT STILL APPEARS THAT SOME PHASING OF EMBEDDED SHORT
WAVE IMPULSES WILL LEAD TO SHARPENING ALONG A POSITIVELY TILTED AXIS
EXTENDING FROM NORTHWESTERN ONTARIO THROUGH THE TEXAS BIG BEND
REGION BY 12Z MONDAY. SIZABLE SPREAD PERSISTS AMONG THE MODELS AND
MODEL ENSEMBLES CONCERNING THE DETAILS OF THE SHORT WAVE
DEVELOPMENTS...BUT IT APPEARS THAT THE LEAD IMPULSE SHIFTING EAST OF
THE NORTHERN PLAINS EARLY IN THE PERIOD MAY REMAIN MOST PROMINENT AS
IT CONTINUES EAST NORTHEASTWARD ACROSS THE UPPER MIDWEST AND GREAT
LAKES REGION. THIS FEATURE IS EXPECTED TO SUPPORT PRIMARY SURFACE
CYCLOGENESIS...MAINLY EAST OF THE MIDDLE MISSISSIPPI VALLEY INTO
SOUTHERN ONTARIO LATE IN THE PERIOD.

A SIGNIFICANT COLD INTRUSION PROBABLY WILL SURGE MORE RAPIDLY
SOUTHWARD THROUGH THE SOUTHERN PLAINS THAN EASTWARD INTO THE LOWER
MISSISSIPPI VALLEY...AS A SOUTHERLY RETURN FLOW OFF THE WESTERN GULF
OF MEXICO CONTRIBUTES TO PRE-FRONTAL MOISTENING. A NARROW CORRIDOR
OF PRECIPITABLE WATER IN EXCESS OF 1 INCH MAY REACH THE UPPER OHIO
VALLEY/LOWER GREAT LAKES REGION BY LATE SUNDAY NIGHT...WITH VALUES
OF 1.25 TO 1.5 INCHES ACROSS THE WESTERN GULF COAST INTO THE LOWER
MISSISSIPPI VALLEY. COUPLED WITH INCREASING FORCING FOR UPWARD
VERTICAL MOTION...DESTABILIZATION PROBABLY WILL BE SUFFICIENT TO
SUPPORT CONSIDERABLE THUNDERSTORM ACTIVITY FROM PORTIONS OF THE
SOUTHERN PLAINS INTO THE LOWER OHIO AND TENNESSEE VALLEYS...AND
PERHAPS PARTS OF THE LOWER GREAT LAKES REGION.

...CNTRL/SRN AND ERN AR...NE TX...NRN LA...NWRN MS...WRN TN...
ALTHOUGH SOUTH/SOUTHWESTERLY LOW-LEVEL JET STRENGTHENING LIKELY WILL
BE STRONGEST TO THE NORTHEAST OF THE REGION LATE IN THE
PERIOD...MODEST STRENGTHENING OF 850 MB FLOW TO 30-40 KT STILL
APPEARS POSSIBLE ACROSS PARTS OF THE ARKLATEX REGION INTO UPPER
PORTIONS OF THE LOWER MISSISSIPPI VALLEY SUNDAY EVENING. THIS IS
EXPECTED TO OCCUR AS A SHORT WAVE IMPULSE /LIKELY DIGGING UPSTREAM
THROUGH MUCH OF THE DAY SUNDAY/ FINALLY BEGINS TO ACCELERATE EAST OF
THE SOUTHERN ROCKIES. THIS MAY ALSO CONTRIBUTE TO AN INCREASINGLY
DIVERGENT UPPER FLOW FIELD ACROSS SOUTHERN/EASTERN ARKANSAS AND
ADJACENT STATES...WHERE VERTICAL SHEAR AND FORCING FOR UPWARD
VERTICAL MOTION MAY SUPPORT SQUALL LINE EVOLUTION. A WINDOW OF
OPPORTUNITY APPEARS TO EXIST FOR POTENTIALLY DAMAGING WIND
GUSTS...AS WELL AS LARGE HAIL...BEFORE ACTIVITY SPREADS INTO A LESS
STABLE ENVIRONMENT TO THE EAST AND WEAKENS OVERNIGHT.

PEAK BOUNDARY LAYER DESTABILIZATION IS EXPECTED DURING THE LATE
AFTERNOON AND EARLY EVENING HOURS ALONG A PRE-FRONTAL CORRIDOR
ACROSS THE ARKLATEX INTO CENTRAL ARKANSAS. BEFORE STRONGER FORCING
DEVELOPS...SCATTERED DISCRETE STORM DEVELOPMENT IS POSSIBLE IN THE
PRESENCE OF 500-1000 J/KG OF MIXED LAYER CAPE. FORECAST SOUNDINGS
ARE SUGGESTIVE OF STRONG...BUT MOSTLY UNIDIRECTIONAL VERTICAL SHEAR.
HOWEVER...LOW-LEVEL HODOGRAPHS MAY BECOME SUFFICIENTLY LARGE TO
SUPPORT AT LEAST SOME TORNADIC POTENTIAL.

..KERR.. 12/08/2012

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