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WWUS20 KWNS 200343

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SPC WW 200343

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 355

NWS STORM PREDICTION CENTER NORMAN OK

1040 PM CDT SAT JUN 19 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN NEBRASKA

       SOUTHERN SOUTH DAKOTA



EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 1040 PM

UNTIL 500 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 70

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 95 MILES NORTHWEST

OF MULLEN NEBRASKA TO 25 MILES NORTHEAST OF ONEILL NEBRASKA.  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 354...



DISCUSSION...COMBINATION OF APPROACHING SHORTWAVE TROUGH AND

STRENGTHENING LOW LEVEL JET SHOULD INCREASE STORM COVERAGE IN THE

SD/NEB BORDER REGION. MUCAPES NEAR 1000 J/KG AND VERY STEEP LAPSE

RATES WILL BE FAVORABLE FOR SEVERE HAIL. ALSO...AS MORE STORMS

DEVELOP...THERE IS THE POSSIBILITY THAT THE STORM DOWNDRAFTS MAY

MERGE INTO A LINE SEGMENT...WHICH WOULD INCREASE THE POSSIBILITY FOR

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 450. MEAN STORM

MOTION VECTOR 29025.





...IMY

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