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224 

WWUS20 KWNS 010249

SEL9

SPC WW 010249

IAZ000-MNZ000-NEZ000-SDZ000-010900-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 509

NWS STORM PREDICTION CENTER NORMAN OK

950 PM CDT SAT AUG 31 2013



THE NWS STORM PREDICTION CENTER HAS ISSUED A



* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

  NORTHERN IOWA

  SOUTHERN MINNESOTA

  NORTHEAST NEBRASKA

  SOUTHEAST SOUTH DAKOTA



* EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 950 PM

  UNTIL 400 AM CDT.



* PRIMARY THREATS INCLUDE...

  SEVERAL LARGE HAIL EVENTS WITH A FEW VERY LARGE HAIL EVENTS TO 2

    INCHES IN DIAMETER POSSIBLE

  SEVERAL DAMAGING WIND GUSTS TO 70 MPH POSSIBLE



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 75

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

WORTHINGTON MINNESOTA TO 30 MILES SOUTHWEST OF STORM LAKE IOWA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU9).



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.



&&



OTHER WATCH INFORMATION...CONTINUE...WW 508...



DISCUSSION...TSTMS NOW FORMING IN SW MN ARE LOCATED NEAR/ATOP

OUTFLOW BOUNDARY LEFT BY EARLIER MCS. OTHER STORMS ARE FORMING IN SE

SD ALONG COLD FRONT ASSOCIATED WITH AMPLIFYING UPR IMPULSE CROSSING

NRN MN. GIVEN DEGREE OF MID-LVL INSTABILITY/LOW-LVL MOISTURE PRESENT

OVER REGION...AND LIKELIHOOD FOR INCREASING LARGE SCALE ASCENT AS

AREA IS GLANCED BY PASSING VORT MAX...SETUP MAY YIELD A FEW STORMS

WITH SVR HAIL/LOCALLY DMGG WIND...DESPITE TIME OF DAY AND RELATIVELY

WEAK LOW-LVL FLOW.



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 31025.





...CORFIDI

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