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893 

WWUS20 KWNS 122057

SEL9

SPC WW 122057

COZ000-KSZ000-NEZ000-SDZ000-130500-



URGENT - IMMEDIATE BROADCAST REQUESTED

Severe Thunderstorm Watch Number 449

NWS Storm Prediction Center Norman OK

300 PM MDT Sat Aug 12 2017



The NWS Storm Prediction Center has issued a



* Severe Thunderstorm Watch for portions of

  Eastern Colorado

  Northwest Kansas

  Western Nebraska

  Southern South Dakota



* Effective this Saturday afternoon and evening from 300 PM until

  1100 PM MDT.



* Primary threats include...

  Scattered large hail likely with isolated very large hail events

    to 3 inches in diameter possible

  Isolated damaging wind gusts to 70 mph possible

  A tornado or two possible



SUMMARY...Multiple corridors of severe thunderstorms are expected to

continue to increase across the region through the remainder of the

afternoon into evening. The environment will support supercells

capable of large hail. Clusters of southeastward-moving storms will

also evolve with damaging winds and additional concern.



The severe thunderstorm watch area is approximately along and 90

statute miles east and west of a line from 65 miles north of

Valentine NE to 25 miles west southwest of Burlington CO. For a

complete depiction of the watch see the associated watch outline

update (WOUS64 KWNS WOU9).



PRECAUTIONARY/PREPAREDNESS ACTIONS...



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 447...WW 448...



AVIATION...A few severe thunderstorms with hail surface and aloft to

3 inches. Extreme turbulence and surface wind gusts to 60 knots. A

few cumulonimbi with maximum tops to 500. Mean storm motion vector

31025.



...Guyer

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