

000 

WWUS20 KWNS 220334

SEL0

SPC WW 220334

NEZ000-SDZ000-220900-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 160

NWS STORM PREDICTION CENTER NORMAN OK

1035 PM CDT SAT APR 21 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTH CENTRAL INTO PART OF NORTHEASTERN NEBRASKA

       SOUTHEASTERN SOUTH DAKOTA



EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 1035 PM

UNTIL 400 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 45 MILES NORTH OF

BROOKINGS SOUTH DAKOTA TO 35 MILES WEST OF BURWELL NEBRASKA.  FOR

A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU0).



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

TORNADO WATCH NUMBER 154...TORNADO WATCH NUMBER 155. WATCH NUMBER

154 155 WILL NOT BE IN EFFECT AFTER 1035 PM CDT. CONTINUE...WW

157...WW 158...WW 159...



DISCUSSION...MODERATE INSTABILITY AND STRONG EFFECTIVE BULK SHEAR

WILL PERSIST ACROSS MUCH WW TONIGHT.  STORMS WILL LIKELY REMAIN

SLIGHTLY ELEVATED...THOUGH SUPERCELLS AND SMALL BOWING STRUCTURES

CAN BE EXPECTED.  THIS WILL INCREASE THE THREAT OF LARGE

HAIL...ALONG WITH ISOLATED DAMAGING WINDS.



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 24025.





...EVANS

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