SWODY1
SPC AC 091615
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1115 AM CDT THU APR 09 2009
VALID 091630Z - 101200Z
...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER
PARTS OF EASTERN OK...SOUTHEAST KS...SOUTHWEST MO AND WESTERN AR...
...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE SOUTHERN
PLAINS INTO THE MID MS VALLEY...
PREVIOUS FORECAST LOOKS ON TRACK FOR A FOCUSED BUT POTENTIALLY
SIGNIFICANT SEVERE WEATHER EVENT LATER THIS AFTERNOON/EVENING IN
ADVANCE OF THE STRONG UPPER TROUGH CURRENTLY MOVING EWD ACROSS SRN
HIGH PLAINS. AN ELONGATED SURFACE LOW ALONG KS/OK BORDER WITH
PRIMARY CENTER SWRN KS EXPECTED TO CONSOLIDATE AND MOVE EWD TO BE
LOCATED S OF ICT BY LATER THIS AFTERNOON.
...SOUTHEASTERN KS/NORTHEASTERN OK THIS AFTERNOON...
DRY LINE CURRENTLY SHARPENING UP WRN OK WILL BE PRIMARY FOCUS FOR
SEVERE THUNDERSTORM INITIATION AFTER 21Z. RAPID MOISTENING OF THE
BOUNDARY LAYER IS OCCURRING THIS MORNING AS STRONG SOUTHERLY LOW
LEVEL JET TRANSPORTS GULF AIRMASS NORTHWARD INTO OK/AR. BY MID
AFTERNOON...SURFACE DEWPOINTS IN THE MID TO UPPER 50S ARE EXPECTED
OVER MOST OF EASTERN OK EAST OF THE DRYLINE...WITH NEAR 50F
DEWPOINTS WRAPPING WESTWARD ALONG THE KS/OK BORDER NEAR THE SURFACE
LOW. THE CAPPING INVERSION WILL SUPPRESS
SURFACE-BASED CONVECTION OVER THIS REGION UNTIL EARLY THIS
AFTERNOON. HOWEVER...IT APPEARS LIKELY THAT STRONG FORCING AND
COOLING ALOFT WILL YIELD A NARROW ZONE OF WEAKENING CAP ALONG THE
OK/KS BORDER BY 19-21Z. ISOLATED THUNDERSTORMS WILL LIKELY DEVELOP
IN THIS ZONE AND TRACK NORTHEASTWARD INTO SOUTHEASTERN KS. FORECAST
SOUNDINGS IN THIS REGION SUGGEST THE RISK OF RELATIVELY LOW-TOPPED
SUPERCELLS CAPABLE OF HAIL AND ISOLATED TORNADOES.
...EASTERN OK/SOUTHWEST MO/WESTERN AR...
ONLY ADJUSTMENT IN THIS AREA WAS TO SHIFT THE INITIATION ZONE A
LITTLE FURTHER W BASED ON SUGGESTIONS BY HIGH RES MODELS AND RUC
THAT THE STRONG HEATING COULD ERODE CAP SUFFICIENTLY ALONG DRY LINE
TO REMOVE CINH PRIOR TO DRY LINE MIXING TO THE E OF A TUL/MLC LINE.
UPON DEVELOPMENT...THESE STORMS WILL MOVE INTO SOUTHWEST MO AND
WESTERN AR DURING THE EVENING. STEEP MID LEVEL LAPSE RATES AND COOL
TEMPERATURES ALOFT...COUPLED WITH SUFFICIENT EFFECTIVE SHEAR FOR
SUPERCELLS WILL PROMOTE THE RISK OF VERY LARGE HAIL IN STRONGER
CELLS. FORECAST SOUNDINGS ALSO INDICATE SUBSTANTIAL VEERING AND
INCREASING LOW LEVEL WINDS WITH HEIGHT...POSING A RISK OF
SIGNIFICANT TORNADOES OVER THE MODERATE RISK AREA THROUGH EARLY
EVENING. SURFACE DEWPOINT VALUES ARE ONLY FORECAST TO REACH THE
LOWER 60S AT BEST ACROSS THE MDT AREA...BUT RAPIDLY COOLING
TEMPERATURES ALOFT AND STRENGTH OF VERTICAL SHEAR EXPECTED TO RESULT
IN MLCAPES TO 2000 J/KG AND WIND PROFILES MORE THAN SUFFICIENT TO
SUPPORT DEVELOPMENT OF TORNADIC SUPERCELLS.
OVERNIGHT...THUNDERSTORMS WILL LIKELY INCREASE IN COVERAGE AS THEY
SPREAD EASTWARD ACROSS AR AND SOUTHERN MO INTO WESTERN KY/TN. THE
SEVERE THREAT WILL LIKELY BECOME LESS ORGANIZED...BUT STRONGER CELLS
WILL REMAIN CAPABLE OF HAIL AND DAMAGING WINDS MUCH OF THE NIGHT.
..HALES/SMITH.. 04/09/2009
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