SWODY1
SPC AC 011619
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1119 AM CDT TUE JUN 01 2010
VALID 011630Z - 021200Z
...THERE IS A MDT RISK OF SVR TSTMS MUCH OF ERN NE/WRN IA AND PARTS
OF NWRN MO AND SERN SD...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL PLAINS INTO
THE MID/UPPER MS VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS PARTS OF SOUTHERN NEW
ENGLAND...
...CENTRAL PLAINS INTO MID MS VALLEY...
FAST ZONAL FLOW WITH EMBEDDED S/WV TROUGHS EXTENDS FROM PAC NW TO
NERN U.S. IMPULSE MOVING EWD ACROSS WY/NRN CO THIS AFTERNOON WILL
DEEPEN LEE TROUGH/SFC LOW CENTRAL HIGH PLAINS FURTHER ENHANCING THE
SHEAR PROFILES THIS AFTERNOON IN AN ALREADY FAVORABLE ENVIRONMENT
FOR SEVERE THUNDERSTORMS.
ELEVATED SEVERE THUNDERSTORMS DEVELOPED THIS MORNING AS A VERY
UNSTABLE AIR MASS SPREAD NWD OVERNIGHT ACROSS THE CENTRAL PLAINS.
WITH MID LEVEL LAPSE RATES NEAR 8C/KM AND MLCAPES AOA 3000
J/KG...ALONG WITH 30-40 KT OF SHEAR...LARGE HAIL IS ALREADY A THREAT
ALONG AND AHEAD OF THE COLD FRONT SAGGING SEWD FROM CENTRAL MN WSWWD
TO WRN NEB.
DAYTIME HEATING COUPLED WITH THE EXPECTED INCREASE IN THE LOW LEVEL
JET RESPONDING TO DEEPENING LEE LOW CENTRAL PLAINS...PARAMETERS WILL
BECOME FAVORABLE FOR SURFACE BASED SUPERCELLS BY MID AFTERNOON
ACROSS MUCH OF ERN NEB AND INTO WRN IA. AS LOW LEVEL WINDS BACK
ACROSS ERN NEB IN RESPONSE TO PRESSURE FALLS TO THE W...POTENTIAL
FOR TORNADO'S ALONG WITH VERY LARGE HAIL WILL INCREASE BY MID/LATE
AFTERNOON ACROSS ERN NEB...AND INTO WRN IA/NWRN MO BY THIS EVENING.
HAVE UPGRADED TO A MDT MUCH OF ERN NEB/WRN IA FOR THE RISK OF VERY
LARGE HAIL GIVEN THE EXPECTED EXTREME INSTABILITY. BY EVENING SHEAR
PROFILES BECOME INCREASING FAVORABLE FOR TORNADIC SUPERCELLS SERN
NEB/SWRN IA WITH POSSIBLY A STRONG TORNADO.
STORMS EXPECTED TO DEVELOP UPSCALE INTO ONE OR MORE FORWARD
PROPAGATING MCS/S EARLY TONIGHT MOVING EWD ACROSS MID MS VALLEY WITH
AN INCREASING CONCERN FOR DAMAGING WINDS.
...SRN NEW ENGLAND...
THUNDERSTORMS ARE BEGINNING TO INTENSIFY ACROSS SE NY ALONG AN AXIS
OF MODERATE INSTABILITY WHERE OBJECTIVE ANALYSIS SHOWS SBCAPE VALUES
IN THE 1500 TO 2000 J/KG RANGE. THIS MODERATE INSTABILITY EXTENDS
EWD ACROSS MOST OF SRN NEW ENGLAND WHERE SFC DEWPOINTS ARE IN THE
MID 60S F. INCREASING LARGE-SCALE ASCENT ASSOCIATED WITH A SUBTLE
SHORTWAVE TROUGH EVIDENT ON WATER VAPOR IMAGERY SHOULD RESULT IN A
GRADUAL EXPANSION OF CONVECTIVE COVERAGE. THE BOSTON WSR-88D VWP
ESTIMATES 40 KT OF FLOW AT 1 TO 2 KM AGL WHICH COMBINED WITH
INCREASING INSTABILITY AND STEEPENING LOW-LEVEL LAPSE RATES THIS
AFTERNOON SHOULD RESULT IN AN ISOLATED WIND DAMAGE THREAT. HAIL WILL
ALSO BE POSSIBLE ESPECIALLY IF A SUPERCELL CAN ORGANIZE ACROSS THE
ERN PART OF SRN NEW ENGLAND WHERE VERTICAL SHEAR IS STRONGER THAN
AREAS TO THE WEST.
ANY SEVERE THREAT THAT DEVELOPS SHOULD QUICKLY MOVE OFFSHORE BY
EVENING.
..HALES/JIRAK.. 06/01/2010
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