SWODY1
SPC AC 091205
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0705 AM CDT THU APR 09 2009
VALID 091300Z - 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...
CURRENT WATER VAPOR LOOPS SHOW A POWERFUL AND PROGRESSIVE UPPER
TROUGH OVER CO/NM. THIS FEATURE IS FORECAST TO TRACK EASTWARD INTO
THE CENTRAL PLAINS TODAY WHILE DEEPENING AND BECOMING NEGATIVELY
TILTED. MEANWHILE...A DEEP SURFACE LOW WILL MOVE ALONG THE KS/OK
BORDER WITH A DRYLINE EXTENDING SOUTHWARD ACROSS OK INTO TX. THIS
SHOULD SET THE STAGE FOR A FOCUSED BUT ACTIVE SEVERE WEATHER EVENT
THIS AFTERNOON AND EVENING.
...SOUTHERN KS/NORTHERN OK THIS AFTERNOON...
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 THROUGH THE MORNING HOURS.
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 SOUTHERN KS. FORECAST SOUNDINGS IN THIS
REGION SUGGEST THE RISK OF RELATIVELY LOW-TOPPED SUPERCELLS CAPABLE
OF HAIL AND ISOLATED TORNADOES.
...SOUTHEAST KS/EASTERN OK/SOUTHWEST MO/WESTERN AR...
LATER THIS AFTERNOON...INCREASING LARGE SCALE FORCING OVER THE WARM
SECTOR WILL ERODE THE MID LEVEL CAP AND LEAD TO ISOLATED SUPERCELL
THUNDERSTORMS ALONG THE DRYLINE OVER EASTERN OK. THESE STORMS WILL
MOVE INTO EXTREME SOUTHEAST KS...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 GIVE SUFFICIENT
CONFIDENCE TO UPGRADE REGION AT THIS TIME.
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.
..HART/HURLBUT.. 04/09/2009
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