Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 192107

Area Forecast Discussion
National Weather Service Missoula MT
307 PM MDT Thu Apr 19 2018

.DISCUSSION...A low pressure system moving over Utah could cause
enough instability across Lemhi county up into southwest Montana
to produce a few isolated showers this afternoon and evening.
These showers will be short-lived and dissipate after sunset. A
ridge of high pressure builds back over the region on Friday
allowing for some of the warmest temperatures felt this year under
mostly clear skies.

This nice day will be short-lived as a fairly strong cold front is
anticipated to swing through the Northern Rockies on Saturday.
This front will cause breezy to windy conditions across the
region. The strongest will be experienced across west central
Montana up into northwest Montana. West winds could gust as high
as 45 mph by late morning through the afternoon on Saturday. Any
precipitation associated with this front will be mainly confined
to northwest Montana. These winds will cause choppy conditions
particularity on Flathead lake. The winds and shower activity
will be diminishing during the evening and overnight.

The next significant weather feature for the Northern Rockies will
arrive Sunday night, with snow levels dropping to mountain pass
elevations across Lemhi County Idaho and southwest Montana. 2 to 4
inches snow accumulation Sunday night over 5500 feet, including
Gilmore Summit, Lost Trail Pass, Homestake Pass, and MacDonald
Pass. Roads will be slick through midday Monday due to snow and
slush accumulation.

The wintry conditions for the passes will be shortlived, as high
pressure develops over the Northern Rockies Tuesday and Wednesday.
Long term models suggest that a ridge of high pressure just off
the west US coast will direction weak storm systems over the
Northern Rockies for the remainder of next week, however
temperatures are not anticipated to be significantly cooled. Also,
moisture appears to be lacking with these systems, resulting in
more of a "cloud storm" that lack precipitation over high terrain.


.AVIATION...Enough instability across Lemhi county into southwest
Montana could cause a few showers this afternoon and evening. KSMN
has the best shot of being impacted by these showers. The
remainder of the terminals are anticipated to have fair flying
conditions over the next 24 hours.



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