SWODY1
SPC AC 271630
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1030 AM CST SUN FEB 27 2011
VALID 271630Z - 281200Z
...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT FROM
AR NEWD TO THE LOWER OH VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS FROM SRN KS...NRN AND ERN
OK...AND NE TX NEWD INTO THE OH VALLEY...
...MID SOUTH/LOWER OH VALLEY THIS AFTERNOON THROUGH TONIGHT...
THE AXIS OF RICHEST LOW-LEVEL MOISTURE EXTENDS NEWD FROM SE TX TO NW
MS AND ERN AR...ALONG THE LLJ AXIS. CONTINUED NWD/NEWD EXPANSION OF
THE WARM SECTOR AND SOME SURFACE HEATING IN CLOUD BREAKS WILL RESULT
IN SUFFICIENT DESTABILIZATION /MLCAPE OF 1000-1500 J PER KG/ FOR
SEVERE STORMS IN THE WARM SECTOR BY MID-LATE AFTERNOON. VERTICAL
SHEAR PROFILES WILL BE FAVORABLE FOR SUPERCELLS WITH EFFECTIVE BULK
SHEAR IN EXCESS OF 50 KT AND EFFECTIVE SRH AOA 300 M2/S2.
THE PRIMARY CONCERNS THIS AREA DURING THE AFTERNOON WILL BE A FOCUS
FOR STORM INITIATION...THE INFLUENCE OF CLOUDS ON SURFACE
HEATING...AND EWD EXPANSION OF THE ELEVATED MIXED LAYER/CAP.
ASSUMING A FEW STORMS CAN FORM THIS AFTERNOON FROM NE AR INTO WRN
TN...THE ENVIRONMENT WILL BE FAVORABLE FOR TORNADIC SUPERCELLS...AND
THE POTENTIAL FOR A STRONG TORNADO OR TWO. OTHERWISE...AN INCREASE
IN THUNDERSTORMS IS EXPECTED OVERNIGHT IN ADVANCE OF THE EJECTING
MIDLEVEL TROUGH AND ALONG THE LLJ CORRIDOR...ALONG/IN ADVANCE OF THE
COLD FRONT MOVING EWD FROM OK ACROSS AR. THE PRE-FRONTAL CONVECTION
MAY CONTAIN SUPERCELLS WITH A CONTINUED TORNADO RISK OVERNIGHT INTO
THE LOWER OH VALLEY...WHILE A MORE LINEAR CONVECTIVE MODE IS
EXPECTED TO EVOLVE ALONG THE COLD FRONT BY 09-12Z. DAMAGING WINDS
WILL BE THE MAIN THREAT WITH THE FRONTAL CONVECTIVE BAND...THOUGH
QLCS TORNADOES WILL ALSO BE POSSIBLE.
...KS/OK BORDER THIS EVENING INTO NRN MO/IL OVERNIGHT...
THE INITIAL LEE CYCLONE IN SE CO WILL DEVELOP EWD ALONG THE KS/OK
BORDER THIS EVENING INTO EARLY TONIGHT IN RESPONSE TO THE MIDLEVEL
SHORTWAVE TROUGH THAT WILL EJECT ENEWD OVER THE SRN HIGH PLAINS.
SLY FLOW INDUCED BY THE LEE CYCLONE HAS RESULTED IN AN INCREASE IN
LOW-LEVEL MOISTURE IN THE WARM SECTOR INTO OK...WITH BOUNDARY LAYER
DEWPOINTS EXPECTED TO HOLD IN THE LOW 60S THROUGH THE AFTERNOON.
SURFACE HEATING WILL BE INHIBITED BY LOW STRATUS AND A SEPARATE BELT
OF MID-HIGH CLOUDS NOW OVERSPREADING THE ERN TX PANHANDLE/NW TX AND
WRN OK. HOWEVER...CLEARING FROM THE W IS EXPECTED OVER THE DRYLINE
AND TRIPLE POINT BY ABOUT 21Z...AND THIS SURFACE HEATING WILL
CORRESPOND WITH INCREASING LOW-LEVEL ASCENT AND LOCAL WEAKENING OF
CONVECTIVE INHIBITION. THUS...AT LEAST ISOLATED THUNDERSTORM
DEVELOPMENT IS EXPECTED IN THE 22-00Z TIME FRAME NEAR THE TRIPLE
POINT INVOF THE KS/OK BORDER...W OF I-35.
A COMBINATION OF 7-8 C/KM MIDLEVEL LAPSE RATES ABOVE BOUNDARY LAYER
DEWPOINTS OF 58-62 F...AND AFTERNOON SURFACE TEMPERATURES IN THE LOW
70S...WILL SUPPORT MLCAPE NEAR 1500 J/KG. EFFECTIVE BULK SHEAR OF
50-70 KT WILL FAVOR SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL...AND
A COUPLE OF TORNADOES WILL BE POSSIBLE BEFORE STORMS CROSS INTO THE
COOL AIR N OF THE WARM FRONT. OTHERWISE... ELEVATED THUNDERSTORMS
WILL EXPAND NEWD ACROSS SRN AND ERN KS INTO MO AND IL OVERNIGHT IN
ADVANCE OF THE SURFACE LOW...WITH A CONTINUED RISK FOR LARGE HAIL.
..THOMPSON/SMITH.. 02/27/2011
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