DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 110538
SWODY2
SPC AC 110536

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1236 AM CDT THU OCT 11 2012

VALID 121200Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS FRI/FRI NIGHT ACROSS PARTS OF
THE CNTRL AND SRN HIGH PLAINS...

...SYNOPSIS...
TO THE SOUTH OF A BROADLY ANTICYCLONIC BRANCH OF STRONGER
WESTERLIES...MODELS CONTINUE TO INDICATE A LINGERING CYCLONIC BRANCH
CURVING OFF THE PACIFIC...THROUGH CALIFORNIA...INTO THE INTERIOR
U.S. DURING THIS FORECAST PERIOD. WITHIN THIS SOUTHERN STREAM...THE
REMNANT CLOSED LOW...NOW NEAR THE CALIFORNIA COAST...APPEARS LIKELY
TO FINALLY ACCELERATE NORTHEASTWARD OUT OF THE SOUTHWEST...REACHING
THE CENTRAL HIGH PLAINS BY LATE FRIDAY NIGHT/EARLY SATURDAY. AS
THIS OCCURS...A COLD SURFACE HIGH... INITIALLY CENTERED OVER THE
UPPER MISSISSIPPI VALLEY...BUT WITH A RIDGE AXIS EXTENDING
SOUTHWESTWARD INTO THE CENTRAL HIGH PLAINS...IS EXPECTED TO RETREAT
EASTWARD...GIVING WAY TO A DEVELOPING LEE SURFACE TROUGH...AND
EVENTUALLY SIGNIFICANT SURFACE CYCLOGENESIS. 11/00Z NAM...GFS AND
ECMWF ALL APPEAR INCREASINGLY SIMILAR... INDICATING STRONGER SURFACE
PRESSURE FALLS BECOMING CENTERED OVER THE CENTRAL HIGH PLAINS FRIDAY
EVENING. LOW PRESSURE IS THEN EXPECTED TO DEEPEN ALONG A RETREATING
SURFACE FRONT ACROSS PARTS OF WESTERN KANSAS AND NEBRASKA OVERNIGHT.


THE FRONTAL ZONE...INITIALLY EXTENDING FROM THE TEXAS/OKLAHOMA
PANHANDLE REGION INTO THE TENNESSEE VALLEY...MAY BE PROVIDING A
FOCUS FOR CONSIDERABLE THUNDERSTORM ACTIVITY AT 12Z FRIDAY. BUT
THIS IS EXPECTED TO GENERALLY WEAKEN/DIMINISH AS MID-LEVEL HEIGHTS
RISE DOWNSTREAM OF THE CLOSED LOW...AND SUPPORTING LOWER/MID
TROPOSPHERIC WARM ADVECTION WEAKENS. NEW CONVECTIVE DEVELOPMENT
LATER IN THE DAY IS THEN EXPECTED TO FOCUS IN THE PRESENCE OF
STRENGTHENING WARM ADVECTION...NEAR THE INTERSECTION OF THE CENTRAL
PLAINS WARM FRONT AND THE LEE SURFACE TROUGH ACROSS THE HIGH
PLAINS...THEN FRIDAY NIGHT ALONG THE STRENGTHENING SOUTHERLY
LOW-LEVEL JET AXIS ACROSS THE PLAINS INTO THE UPPER MISSISSIPPI
VALLEY.

ADDITIONAL SCATTERED THUNDERSTORM ACTIVITY IS EXPECTED FRIDAY
BENEATH THE MID-LEVEL COLD POOL ASSOCIATED WITH THE CLOSED
LOW...ACROSS LARGE PORTION OF THE GREAT BASIN AND CENTRAL SOUTHERN
ROCKIES.

...CENTRAL/SOUTHERN HIGH PLAINS...
BOUNDARY LAYER MODIFICATION OVER THE CENTRAL AND SOUTHERN HIGH
PLAINS REMAINS THE PRIMARY UNCERTAINTY CONCERNING SEVERE WEATHER
POTENTIAL FOR FRIDAY/FRIDAY NIGHT. A SHALLOW COOL/STABLE NEAR
SURFACE LAYER MAY PERSIST ACROSS MUCH OF WESTERN KANSAS...AND AREAS
NORTHWARD...THROUGH THE DAY...AND PERHAPS THROUGH MUCH OF THE
PERIOD. SOUTH OF THE FRONT...GUIDANCE IS SUGGESTIVE THAT DAYTIME
HEATING BENEATH AT LEAST MODESTLY STEEP MID-LEVEL LAPSE RATES WILL
CONTRIBUTE TO MIXED LAYER CAPE IN EXCESS OF 1000 J/KG ...WITH
SURFACE DEW POINTS AT OR ABOVE 60F.

AS A CYCLONIC 70+ KT 500 MB JET STREAK NOSES ACROSS THE
ROCKIES...TOWARD THE CENTRAL HIGH PLAINS...ASSOCIATED FORCING FOR
UPWARD VERTICAL MOTION AND STRENGTHENING SHEAR ARE EXPECTED TO
SUPPORT STRONG/SEVERE STORM DEVELOPMENT. THIS PROBABLY WILL INCLUDE
A FEW SUPERCELLS...BOTH ALONG THE SLOWLY EASTWARD ADVANCING DRY LINE
AND NORTHWARD ADVANCING WARM FRONT ACROSS THE PANHANDLE REGION.
ENLARGING CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS THROUGH THE LATE
AFTERNOON AND EARLY EVENING HOURS SEEMS LIKELY TO SUPPORT AT LEAST
THE RISK FOR TORNADOES. OTHERWISE...UNLESS THE BOUNDARY LAYER
DESTABILIZES MORE THAN CURRENTLY ANTICIPATED...LARGE HAIL MAY BECOME
THE MORE PROMINENT SEVERE WEATHER THREAT DURING THE
EVENING/OVERNIGHT HOURS...AS THE MOST VIGOROUS STORMS SPREAD WITH
STRONGER LARGE SCALE FORCING OR THERMAL/MOISTURE ADVECTION ACROSS
PARTS OF WESTERN AND CENTRAL KANSAS...PERHAPS SOUTH CENTRAL
NEBRASKA.

..KERR.. 10/11/2012

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