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938 

WWUS20 KWNS 110611

SEL7

SPC WW 110611

IAZ000-MNZ000-NEZ000-SDZ000-111200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 297

NWS STORM PREDICTION CENTER NORMAN OK

115 AM CDT FRI JUN 11 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWEST IOWA

       SOUTHWEST MINNESOTA

       EXTREME NORTHEAST NEBRASKA

       SOUTHEAST SOUTH DAKOTA



EFFECTIVE THIS FRIDAY MORNING FROM 115 AM UNTIL 700 AM CDT.



HAIL TO 1 INCH 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 55

STATUTE MILES EAST AND WEST OF A LINE FROM 20 MILES NORTH OF

BROOKINGS SOUTH DAKOTA TO 20 MILES WEST OF SIOUX CITY IOWA.  FOR

A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU7).



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

SEVERE THUNDERSTORM WATCH NUMBER 295. WATCH NUMBER 295 WILL NOT

BE IN EFFECT AFTER 115 AM CDT. CONTINUE...WW 296...



DISCUSSION...MERGING STORM CLUSTERS WILL CONTINUE TO SPREAD EWD FROM

NE NEB/SE SD TOWARD SW MN/NW IA THROUGH THE EARLY MORNING HOURS.

THE CONVECTION WILL BE MAINTAINED BY AN INFLUX OF 68-70 F BOUNDARY

LAYER DEWPOINTS ON THE NOSE OF A 30-40 KT LLJ.  DAMAGING WINDS WILL

BE THE PRIMARY SEVERE THREAT FOR THE NEXT FEW HOURS...BEFORE

INCREASING CONVECTIVE INHIBITION AND WEAKENING INSTABILITY WITH EWD

EXTENT EVENTUALLY LEAD TO WEAKEN OF THE STORMS AND SEVERE THREAT.



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

TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS.

A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM MOTION

VECTOR 27030.





...THOMPSON

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