Thursday, June 18, 2009

Severe storm watch until 5 am

(Update: 11:00 pm. Tornado watch expires - most severe, tornadic storms formed over far southern Wisconsin and northeastern Iowa. An approaching upper level disturbance may still kick off strong/severe storms overnight, with a potential for golf ball size hail, wind gusts over 60 mph, frequent lightning and downpours).


URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 472
NWS STORM PREDICTION CENTER NORMAN OK
1050 PM CDT THU JUN 18 2009

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

PARTS OF EAST-CENTRAL AND SOUTHERN MINNESOTA

EFFECTIVE THIS THURSDAY NIGHT AND FRIDAY MORNING FROM 1050 PM
UNTIL 500 AM CDT.

HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 60
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES SOUTH
SOUTHWEST OF REDWOOD FALLS MINNESOTA TO 15 MILES NORTHEAST OF
MINNEAPOLIS MINNESOTA. FOR A COMPLETE DEPICTION OF THE WATCH SEE
THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU2).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

OTHER WATCH INFORMATION...THIS SEVERE THUNDERSTORM WATCH REPLACES
TORNADO WATCH NUMBER 467. WATCH NUMBER 467 WILL NOT BE IN EFFECT
AFTER 1050 PM CDT. CONTINUE...WW 469...WW 470...WW 471...

DISCUSSION...MOIST/MODERATELY-UNSTABLE AIRMASS PERSISTS ACROSS PARTS
OF THE SRN HALF OF MN...AHEAD OF A NE-SW BAND OF SCATTERED SHOWERS
AND THUNDERSTORMS. WHILE THIS CONVECTION HAS WEAKENED OVER THE PAST
COUPLE OF HOURS...WELL-DEFINED UPPER SYSTEM CENTERED OVER NRN MN
CONTINUES TO SHIFT SLOWLY EWD -- WHICH SHOULD CONTINUE TO SUPPORT
SOME POTENTIAL FOR CONVECTIVE REDEVELOPMENT OVER THE NEXT FEW HOURS.
WITH FAVORABLE SHEAR IN PLACE ACROSS THE AREA...ANY DEVELOPING
STORMS WOULD LIKELY BECOME SUPERCELLULAR -- ALONG WITH ASSOCIATED
POTENTIAL FOR LARGE HAIL AND DAMAGING WINDS. IN
ADDITION...LOW-LEVEL VEERING WITH HEIGHT SUGGESTS A LIMITED THREAT
FOR AN ISOLATED/BRIEF TORNADO WITH ANY SUSTAINED SUPERCELL.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 26030.

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