SWODY2
SPC AC 311728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT SUN MAY 31 2009
VALID 011200Z - 021200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL
PLAINS...MID TO UPPER MS VALLEY AND NRN OH VALLEY...
...CNTRL PLAINS/MID TO UPPER MS VALLEY/NRN OH VALLEY...
A WEST NORTHWEST FLOW PATTERN ACROSS THE NRN U.S. WILL GRADUALLY
BECOME MORE WESTERLY MONDAY. AT THE SFC...A COLD FRONT IS FORECAST
TO MOVE SWD ACROSS THE UPPER MIDWEST INTO THE SRN GREAT LAKES
REGION. THE WWD EXTENSION OF THE FRONT SHOULD BE LOCATED ACROSS THE
CNTRL PLAINS ATTENDANT TO A SFC LOW. ALTHOUGH A FEW STORMS COULD BE
ONGOING ALONG THE BOUNDARY MONDAY MORNING...MODEL FORECASTS DEVELOP
MOST OF THE CONVECTION IN THE AFTERNOON AS SFC TEMPS WARM AND
LOW-LEVEL CONVERGENCE BECOMES FOCUSED ALONG AND SOUTH OF THE
BOUNDARY. ALL THE MODELS ARE FAIRLY SIMILAR INCREASING STORM
COVERAGE BY EARLY EVENING WITH A LINEAR MCS DEVELOPING FROM ERN NEB
EWD ACROSS SRN IA INTO CNTRL IL. ALTHOUGH INSTABILITY WEAKENS WITH
SPATIAL EXTENT FROM IND EWD ACROSS OH...NW PA AND WRN
NY...THUNDERSTORMS SHOULD ALSO INITIATE THERE LATE MONDAY AFTERNOON.
ALTHOUGH THE STRONGER MID-LEVEL FLOW WILL REMAIN NWD ACROSS THE
GREAT LAKES REGION...NAMKF FORECAST SOUNDINGS ALONG THE BOUNDARY IN
ERN NEB AT 00Z SHOW SUBSTANTIAL VEERING WITH HEIGHT. IN ADDITION...A
PLUME OF STEEP MID-LEVEL LAPSE RATES IS FORECAST FROM WRN KS NEWD
INTO SW IA. CELLS IN THIS CNTRL PLAINS ENVIRONMENT MAY HAVE A
TENDENCY TO REMAIN DISCRETE. SUPERCELLS WITH LARGE HAIL AND AN
ISOLATED TORNADO THREAT WILL BE POSSIBLE BEFORE A TRANSITION TO
LINEAR MODE BY EARLY EVENING. FURTHER EAST ACROSS IL AND
IND...CONFIDENCE IS GREATER THAT LINEAR WILL BE THE DOMINANT MODE.
VEERED LOW-LEVEL WINDS ALONG WITH ABOUT 30 KT OF VERTICAL SHEAR AND
STEEP L0W-LEVEL LAPSE RATES SHOULD SUPPORT A WIND DAMAGE THREAT IN
THE LATE AFTERNOON AND EARLY EVENING. HAIL WILL ALSO BE POSSIBLE
WITH THE STRONGER CELL ELEMENTS IN THE LINE.
...SRN PLAINS AND CNTRL HIGH PLAINS...
A RELATIVELY WEAK FLOW PATTERN WILL BE IN PLACE ACROSS THE HIGH
PLAINS MONDAY AS A COLD FRONT ADVANCES SWD ACROSS SW NEB INTO NW KS
MONDAY AFTERNOON. SCATTERED THUNDERSTORMS SHOULD DEVELOP ALONG THE
FRONT IN WRN NEB AND SWD ALONG A SFC TROUGH INTO WRN KS...WRN OK AND
WEST TX. STEEP MID-LEVEL LAPSE RATES AND MODERATE INSTABILITY
EVIDENT ON FORECAST SOUNDINGS SHOULD BE SUFFICIENT FOR HAIL DURING
THE LATE AFTERNOON WHEN INSTABILITY WILL BE MAXIMIZED. ISOLATED
SEVERE WIND GUSTS SHOULD ALSO BE POSSIBLE. THE AREA WITH THE
GREATEST POTENTIAL FOR SEVERE STORMS SHOULD EXIST IN SWRN NEB WHERE
MODERATE VERTICAL SHEAR IS FORECAST. FURTHER SOUTH IN THE LUBBOCK
AND MIDLAND AREAS FORECAST SOUNDINGS SHOW 25-30 KT OF 0-6 KM SHEAR
WITH MUCAPE VALUES OF 2000-2500 J/KG. IF ISOLATED THUNDERSTORMS CAN
DEVELOP IN THIS ENVIRONMENT THEN A FEW LARGE HAIL REPORTS AND
MARGINALLY SEVERE WIND GUSTS WILL BE POSSIBLE.
...ORE/NRN CA/NW NV...
AN UPPER-LEVEL TROUGH IS FORECAST TO REMAIN OFF THE COAST OF CA
MONDAY. AT THE SFC...A TROUGH SHOULD BE IN PLACE ACROSS NRN CA INTO
WRN ORE WITH 50S F SFC DEWPOINTS IN THE LOWER ELEVATIONS. SCATTERED
THUNDERSTORMS SHOULD DEVELOP ALONG THE TROUGH AND IN THE HIGHER
TERRAIN MONDAY AFTERNOON. FORECAST SOUNDINGS ALONG THE INSTABILITY
AXIS SHOW MODERATE VERTICAL SHEAR PROFILES AND STEEP MID-LEVEL LAPSE
RATES. THIS WILL LIKELY BE FAVORABLE FOR AT LEAST MARGINALLY SEVERE
STORMS WITH HAIL AND STRONG WIND GUSTS. ONCE THIS SEVERE POTENTIAL
BECOMES MORE CERTAIN...AN UPGRADE TO SLIGHT RISK MAY BECOME
NECESSARY.
..BROYLES.. 05/31/2009
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