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039 

WWUS20 KWNS 050047

SEL5

SPC WW 050047

IAZ000-MNZ000-NEZ000-SDZ000-050700-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 615

NWS STORM PREDICTION CENTER NORMAN OK

745 PM CDT TUE SEP 4 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWEST IOWA

       SOUTHWEST MINNESOTA

       NORTHEAST NEBRASKA

       SOUTHEAST SOUTH DAKOTA



EFFECTIVE THIS TUESDAY NIGHT AND WEDNESDAY MORNING FROM 745 PM

UNTIL 200 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 EAST AND WEST OF A LINE FROM 15 MILES NORTH OF

BROOKINGS SOUTH DAKOTA TO 15 MILES EAST SOUTHEAST OF SIOUX CITY

IOWA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED

WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).



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 614...



DISCUSSION...BAND OF CONVECTION OVER NE NEB/SE SD IS EXPECTED TO

PERSIST OVERNIGHT AS LOW-LEVEL FLOW/WAA STRENGTHEN IN RESPONSE TO A

SHORTWAVE TROUGH MOVING EWD OVER THE DAKOTAS.  THE 00Z OAX SOUNDING

AND SURFACE OBSERVATIONS CONFIRM A FEED OF INSTABILITY FROM THE S

INTO THIS AREA...THUS THE RISK FOR LARGE HAIL/DAMAGING WINDS SHOULD

PERSIST FOR THE NEXT FEW HOURS WITH MAINLY ELEVATED STORMS INTO NW

IA/SW MN.



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 27025.





...THOMPSON

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