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280 

WWUS20 KWNS 311956

SEL7

SPC WW 311956

MNZ000-NDZ000-SDZ000-WIZ000-LSZ000-010200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 507

NWS STORM PREDICTION CENTER NORMAN OK

250 PM CDT SAT AUG 31 2013



THE NWS STORM PREDICTION CENTER HAS ISSUED A



* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

  MUCH OF MINNESOTA

  FAR SOUTHEAST NORTH DAKOTA

  PARTS OF EASTERN SOUTH DAKOTA

  PORTIONS OF NORTHWESTERN WISCONSIN

  LAKE SUPERIOR



* EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 250 PM UNTIL

  900 PM CDT.



* PRIMARY THREATS INCLUDE...

  SEVERAL LARGE HAIL EVENTS WITH A FEW VERY LARGE HAIL EVENTS TO

    2.5 INCHES IN DIAMETER POSSIBLE

  SEVERAL DAMAGING WIND GUSTS TO 70 MPH POSSIBLE

  A FEW TORNADOES POSSIBLE



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 120

STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES WEST

NORTHWEST OF ELY MINNESOTA TO 5 MILES SOUTHWEST OF SIOUX FALLS

SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).



PRECAUTIONARY/PREPAREDNESS ACTIONS...



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.



&&



DISCUSSION...THUNDERSTORMS ARE SLOWLY DEVELOPING ATTM FROM

NORTHWESTERN MINNESOTA/NORTHEASTERN NORTH DAKOTA SOUTHWARD INTO

NORTH CENTRAL AND NORTHEASTERN SOUTH DAKOTA...AHEAD OF AN ADVANCING

COLD FRONT AND ASSOCIATED UPPER SYSTEM CROSSING THE SOUTHERN

CANADIAN PRAIRIE.

WITH ADDITIONAL DESTABILIZATION OF THE PRE-FRONTAL AIRMASS...EXPECT

AN INCREASE IN STORM COVERAGE AND INTENSITY OVER THE NEXT FEW HOURS

-- AIDED BY MODERATELY STRONG MID-LEVEL WLYS.  INITIAL MIXED-MODE

CONVECTION IS LIKELY TO GROW UPSCALE LINEARLY...WITH LARGE HAIL AND

DAMAGING WINDS THE MAIN SEVERE RISK -- THOUGH AN ISOLATED TORNADO

WILL ALSO BE ALSO POSSIBLE.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 28040.





...GOSS

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