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WWUS20 KWNS 012202

SEL1

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IAZ000-NEZ000-SDZ000-020600-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 221

NWS STORM PREDICTION CENTER NORMAN OK

500 PM CDT TUE MAY 1 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWEST IOWA

       CENTRAL THROUGH NORTHEASTERN NEBRASKA

       SOUTHEAST SOUTH DAKOTA



EFFECTIVE THIS TUESDAY AFTERNOON AND WEDNESDAY MORNING FROM 500

PM UNTIL 100 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 115

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

NORTHEAST OF YANKTON SOUTH DAKOTA TO 35 MILES SOUTHEAST OF

BURWELL NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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 217...WW 218...WW

219...WW 220...



DISCUSSION...TSTMS EXPECTED TO DEVELOP SWD ALONG NE-SE COLD FRONT

NOW CROSSING SE SD/CNTRL SD AS SFC HEATING CONTINUES TO DESTABILIZE

REGION TO ITS SE.  DEEP SHEAR AND INSTABILITY SHOULD BE SUFFICIENT

FOR A FEW SUSTAINED STORMS/SUPERCELLS WITH LARGE HAIL AND DMGG WIND.

ADDITIONAL...POSSIBLY SEPARATE STORM DEVELOPMENT MAY OCCUR LATER

THIS EVE OVER S CNTRL AND ERN NEB AS SLY LLJ BROADENS AND

STRENGTHENS IN RESPONSE TO DIURNAL CYCLE AND APPROACH OF CNTRL RCKYS

UPR IMPULSE.



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 550. MEAN STORM

MOTION VECTOR 26030.





...CORFIDI

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