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WWUS20 KWNS 161923

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MTZ000-WYZ000-170300-



URGENT - IMMEDIATE BROADCAST REQUESTED

Severe Thunderstorm Watch Number 511

NWS Storm Prediction Center Norman OK

125 PM MDT Tue Jul 16 2019



The NWS Storm Prediction Center has issued a



* Severe Thunderstorm Watch for portions of

  South central and southeast Montana

  Parts of northwest and north central Wyoming



* Effective this Tuesday afternoon and evening from 125 PM until

  900 PM MDT.



* Primary threats include...

  Scattered large hail likely with isolated very large hail events

    to 2.5 inches in diameter possible

  Scattered damaging wind gusts to 70 mph likely

  A tornado or two possible



SUMMARY...Thunderstorms are developing over the high terrain along

the Idaho/Montana border, and these storms should expand in coverage

and increase in intensity this afternoon while spreading eastward

across southern Montana and northern Wyoming.  The storm environment

will support supercells capable of producing large hail initially,

and an isolated tornado or two cannot be ruled out.  Later this

evening, storm mergers should lead to upscale growth into a cluster,

with an increasing threat for damaging winds into southeast Montana.



The severe thunderstorm watch area is approximately along and 70

statute miles north and south of a line from 75 miles northwest of

Cody WY to 65 miles east of Broadus MT. For a complete depiction of

the watch see the associated watch outline update (WOUS64 KWNS

WOU1).



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.



&&



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

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

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

27030.



...Thompson

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