SWODY1
SPC AC 230043
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0743 PM CDT SAT AUG 22 2009
VALID 230100Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS EVE ACROSS PARTS OF THE
CAROLINA PIEDMONT...
...THERE IS A SLGT RISK OF SVR TSTMS TONIGHT ACROSS PARTS OF SRN
MONTANA...
...CAROLINAS...
ISOLATED STRONG/SEVERE THUNDERSTORM DEVELOPMENT APPEARS TO REMAIN
POSSIBLE AT LEAST THROUGH THE 02-04Z TIME FRAME ACROSS PARTS OF THE
CAROLINA PIEDMONT...ROUGHLY BETWEEN COLUMBIA AND FAYETTEVILLE. THIS
IS WHERE POTENTIAL INSTABILITY REMAINS MAXIMIZED EAST OF A WEAK
SURFACE LOW WITHIN THE LEE SURFACE TROUGH. LOW-LEVEL WARM ADVECTION
ON THE NOSE OF THE MORE STRONGLY HEATED BOUNDARY LAYER ACROSS THIS
REGION MAY SUPPORT UPSCALE CONVECTIVE GROWTH INTO A CONSOLIDATING
SMALL STORM CLUSTER...AIDED BY MID/UPPER FORCING ASSOCIATED WITH A
SHORT WAVE TROUGH NOW BEGINNING TO LIFT INTO/THROUGH THE SOUTHERN
APPALACHIANS. ALTHOUGH VERTICAL SHEAR IS STILL GENERALLY
WEAK...MODEL GUIDANCE INDICATES A STRENGTHENING OF SOUTHWESTERLY 500
MB FLOW IN EXCESS OF 30 KT IS POSSIBLE THIS EVENING. THIS COULD
ENHANCE THE RISK FOR SEVERE HAIL AND POTENTIALLY DAMAGING WIND GUSTS
BEFORE BOUNDARY LAYER INSTABILITY WANES LATER THIS EVENING.
...SOUTHERN MONTANA...
SUSTAINED CONVECTIVE DEVELOPMENT IS ONGOING WITHIN A BELT OF LARGE
SCALE ASCENT SPREADING EAST NORTHEASTWARD NEAR OR JUST NORTH OF THE
MONTANA/WYOMING BORDER. WEAK INSTABILITY HAS LIMITED THE VIGOR OF
STORMS TO THIS POINT...BUT SOME INTENSIFICATION APPEARS POSSIBLE
THIS EVENING WITHIN A NARROW TONGUE OF MOIST EASTERLY LOW-LEVEL FLOW
WITH PRECIPITABLE WATER APPROACHING 1 INCH. OF PRIMARY CONCERN IS
THE STRENGTH OF THE SHEAR BENEATH 50+ KT WESTERLY MID/UPPER
FLOW...WHICH PROVIDES POTENTIAL FOR THE EVOLUTION OF AN ORGANIZED
CONVECTIVE SYSTEM. IF THIS WERE TO OCCUR...THERMODYNAMIC PROFILES
WITH SIZABLE SUB-CLOUD TEMPERATURE/DEW POINTS SPREADS WILL BE
SUPPORTIVE OF DOWNBURSTS AND SURFACE COLD POOL DEVELOPMENT CAPABLE
OF PRODUCING STRONG SURFACE GUSTS.
..KERR.. 08/23/2009
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