Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 181059
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
359 AM MST Sun Feb 18 2018

.DISCUSSION...
Prolonged widespread snowfall has brought significant
accumulations across the Northern Rockies last night into this
morning. In addition, wind gusts have continued to gust to 30-45
mph in the northern Flathead Valley and also along the Continental
Divide. Severe driving conditions from the Department of
Transportation are still in effect for some of these northern
Flathead Valley/Badrock Canyon locations due to blowing and
drifting snow and the recent heavy accumulations, and therefore
Winter Storm Warnings are still in effect. Unorganized bands of
snow showers are persisting particularly over western Montana and
north- central Idaho this morning ahead of the arctic boundary.

The arctic front continues to push south through the Mission
Valley and eastward into the rest of western Montana early this
morning. Current wind gusts along US-12 and MT-200 are gusting
over 50 mph this morning. This boundary will reach the
Missoula/Bitterroot Valleys by mid morning hours, allowing a
resurgent of snow showers to persist over the I-90 corridor and
southward through the afternoon. In addition, temperatures will
rapidly drop into the teens by this afternoon and single digits by
the overnight period. Wind gusts will continue into tonight which
will allow the wind chills to make it feel much colder. These
bitterly cold temperatures will become widespread for Monday
morning, and are expected to drop several degrees below zero
along the Divide and for much of western Montana.

The cold trough of low pressure lingers across the Northern
Rockies Monday. Gusty easterly winds are anticipated to continue
across much of the region creating dangerous wind chill readings
throughout Monday morning. The winds will steadily diminish
throughout the day. The upper level flow becomes more
northwesterly by Tuesday with the arctic air well entrenched in
the region. Monday night into Tuesday morning appears to be one of
the coldest nights of the season as most of western Montana will
be below-zero and north-central Idaho will be in single digits.

A weak disturbance drops southward into Washington and Oregon on
Wednesday night into Thursday. This disturbance is farther to the
west than previous forecasts, but should still bring a few showers
to the Northern Rockies. An active weather pattern is still
anticipated through the weekend, but details are still uncertain
at this time.

&&

.AVIATION...Scattered snow showers will continue at KGPI this
morning before tapering off this afternoon, generally after
18/1800Z. Gusty east-northeast winds of 25-35 KTS will create
blowing snow conditions until this evening when gusts decrease,
generally after 19/0000Z. As a result, poor visibility and snow
drifts could remain an issue.

For KMSO: Scattered snow showers and intermittent low visibility
down to 1/2 mile at times is likely through the morning hours. The
arctic front will rapidly shift winds from the east, gusting to
20-30 kts after 18/1500Z. Vicinity snow showers will persist, and
could obscure mountains. Blowing and drifting snow will remain
likely through tonight.

For KBTM and KSMN: Periods of low visibility and ceilings will be
common today due to passing snow showers and breezy winds. Wind
gusts increasing from the north and east of 20-30 kts for KBTM
could create blowing and drifting snow issues.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning until 5 PM MST this afternoon
     Butte/Blackfoot Region...Potomac/Seeley Lake Region.

     Winter Storm Warning until 5 PM MST this afternoon
     Bitterroot/Sapphire Mountains.

     Winter Storm Warning until 5 PM MST this afternoon
     Missoula/Bitterroot Valleys.

     Winter Storm Warning until 5 PM MST this afternoon Lower Clark
     Fork Region.

     Winter Storm Warning until 5 PM MST this afternoon
     Flathead/Mission Valleys.

     Winter Storm Warning until 5 PM MST this afternoon West Glacier
     Region.

     Winter Storm Warning until 5 PM MST this afternoon
     Kootenai/Cabinet Region.

ID...Winter Weather Advisory until 5 PM MST this afternoon Eastern
     Lemhi County...Western Lemhi County.

     Winter Weather Advisory until 4 PM PST this afternoon Northern
     Clearwater Mountains...Southern Clearwater Mountains.

     Winter Storm Warning until 4 AM PST early this morning Northern
     Clearwater Mountains...Southern Clearwater Mountains.

&&

$$


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