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000 

WWUS20 KWNS 202047

SEL3

SPC WW 202047

MNZ000-210300-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 673

NWS STORM PREDICTION CENTER NORMAN OK

345 PM CDT THU SEP 20 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       CENTRAL AND SOUTHERN MINNESOTA



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 345 PM UNTIL

1000 PM CDT.



TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 40 STATUTE

MILES NORTH AND SOUTH OF A LINE FROM 50 MILES NORTHWEST OF

REDWOOD FALLS MINNESOTA TO 25 MILES EAST NORTHEAST OF MINNEAPOLIS

MINNESOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.



DISCUSSION...ELEVATED CONVECTION CONTINUES WELL N OF THE SURFACE

WARM FRONT...WHICH HAS NOW DEVELOPED NWD INTO THE MSP AREA.  THE

BOUNDARY LAYER CONTINUES TO WARM/MOISTEN S OF THE BOUNDARY...AND

CONVECTIVE INHIBITION IS BEGINNING TO WEAKEN FOR SURFACE-BASED

PARCELS ACROSS SW AND S CENTRAL MN.  THE NEWER STORM DEVELOPMENT TO

THE W OF MSP MAY STILL BE SLIGHTLY ELEVATED...BUT IT IS VERY CLOSE

TO SURFACE BOUNDARY.  GIVEN THE STRONG VERTICAL SHEAR PRESENT...ANY

STORMS ROOTED IN THE NEAR-SURFACE LAYER WILL BE CAPABLE OF PRODUCING

TORNADOES.  OTHERWISE...LARGE HAIL AND A FEW DAMAGING GUSTS CAN BE

EXPECTED THROUGH LATE EVENING.



AVIATION...TORNADOES AND 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.





...THOMPSON

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