SWODY1
SPC AC 301236
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0736 AM CDT WED SEP 30 2009
VALID 301300Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CENTRAL
PLAINS THIS AFTERNOON THROUGH TONIGHT...
...CENTRAL PLAINS...
MORNING WATER VAPOR LOOPS CONFIRM A LARGE AND DEEP UPPER TROUGH
ROTATING ACROSS THE GREAT BASIN. THIS TROUGH WILL PROGRESS ACROSS
THE ROCKIES AND INTO THE CENTRAL PLAINS DURING THIS FORECAST PERIOD.
MEANWHILE...SURFACE CYCLOGENESIS WILL ENSUE BY EARLY AFTERNOON OVER
EASTERN CO. THIS WILL RESULT IN STRENGTHENING SOUTHERLY LOW LEVEL
WINDS ACROSS THE HIGH PLAINS...WITH RAPID NORTHWARD TRANSPORT OF
GULF MOISTURE FROM TX INTO WESTERN KS. A NARROW AXIS OF AT LEAST
MARGINAL INSTABILITY WILL BE IN PLACE BY LATE AFTERNOON ALONG THE
SURFACE DRYLINE FROM THE TX PANHANDLE INTO SOUTHWEST NEB/NORTHEAST
CO. MODEL FORECAST SOUNDINGS SUGGEST A RATHER STRONG CAP WILL BE IN
PLACE TO THE EAST OF THE DRYLINE. HOWEVER...STRONG HEATING AND
MOISTENING IMMEDIATELY ALONG THE DRYLINE APPEARS LIKELY TO RESULT IN
ISOLATED SEVERE STORMS BY 00Z. EFFECTIVE SHEAR VALUES OF 40-50
KNOTS AND STEEP MID LEVEL LAPSE RATES WILL PROMOTE SUPERCELL STORM
STRUCTURES WITH A RISK OF LARGE HAIL /POSSIBLY VERY LARGE/ AND
DAMAGING WINDS. RATHER LARGE SURFACE T-TD SPREADS AND THE STRONG
CAP ALONG THE DRYLINE WILL LIKELY MITIGATE THE TORNADO THREAT.
STORMS WILL TRACK EAST-NORTHEASTWARD ACROSS PARTS OF KS/NEB THROUGH
THE EVENING WITH A CONTINUED RISK OF HAIL/WIND. EASTWARD PROGRESS
OF SEVERE STORMS WILL BE LIMITED BY WEAK INSTABILITY AS STORMS
APPROACH THE MO RIVER OVERNIGHT.
...WESTERN CO...
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS AFTERNOON OVER
THE WESTERN CO PLATEAU AS THE UPPER TROUGH MOVES ACROSS THE AREA.
COLD TEMPERATURES ALOFT AND STEEP LAPSE RATES WILL PROMOTE A RISK OF
HAIL IN STRONGER CORES...ALONG WITH POSSIBLE GUSTY/DAMAGING WINDS.
LACK OF GREATER LOW LEVEL MOISTURE SHOULD PRECLUDE AN ORGANIZED
SEVERE EVENT.
...WEST TX...
THE SURFACE DRYLINE WILL BECOME ESTABLISHED FROM THE TX PANHANDLE
SOUTHWARD INTO THE BIG BEND REGION BY LATE AFTERNOON. A CAPPING
INVERSION WILL BE IN PLACE ALONG THE DRYLINE TODAY. HOWEVER...FULL
SUNSHINE AND WEAK CONVERGENCE MAY BE SUFFICIENT FOR AN ISOLATED
STORM OR TWO DURING THE EVENING. ANY STORM THAT CAN DEVELOP WOULD
POSE A RELATIVELY BRIEF RISK OF HAIL AND DAMAGING WINDS.
..HART/GRAMS.. 09/30/2009
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