FXUS65 KMSO 170253

Area Forecast Discussion
National Weather Service Missoula MT
753 PM MST Fri Nov 16 2018

.UPDATE...Winter weather advisories have been extended until mid
Saturday morning.


.DISCUSSION...A few showers continue to move through west central
Montana this evening. These showers should steadily decrease as
the evening progresses. The biggest concern will be the continued
icy conditions across the region, especially the Interstate 90
corridor from Bearmouth to Garrison junction. The winter weather
advisories have been extended until mid Saturday morning for these
icy conditions.


.AVIATION...North to east winds will remain blustery at KGPI and
KMSO through about 17/0400 UTC. A decrease in shower activity
will occur the next few hours. An isolated snow shower at KSMN,
KBTM, and KMSO can not be ruled out through 17/0400 UTC. Ceilings
will gradually increase into the VFR category for all TAF sites the
next few hours. Skies will begin to clear out tomorrow morning,
with VFR conditions expected tomorrow across the Northern Rockies.


.PREV DISCUSSION... /ISSUED 249 PM MST Fri Nov 16 2018/

DISCUSSION...Areas of snow showers are currently causing impacts
to travelers on roads across much of southwest Montana from
accumulations of 1/2 to 1 inch and quick reductions in
visibility. Impacted areas are the I-90 corridor from Bonner to
Drummond and Hwy 200 through Helmville. These showers will
continue through 8 pm. Drive with caution folks. The snow activity
is in response to a Canadian cold front that has made its way
through much of Western Montana today, especially along the
Continental Divide. The front will also bring brisk and gusty
northeast winds, if they haven't started already, through the
evening hours.

A few shower can be expected in the Missoula/Bitterroot valleys
through this evening with limited impacts, perhaps local slick
roads especially along Hellgate Canyon.

This system will move well south of the region by Saturday
morning. Expect continued easterly pressure gradient producing
light to moderate east winds through Saturday. There is a slight
potential for lake effect snow on the east side of flathead lake
along Highway 35. A quick 1-2" burst of snow may occur there. in
the late morning to afternoon.

Otherwise cold but sunny weather is expected Saturday for the
Brawl of the Wild, Cat- Griz football game. High temps will be in
the lower to mid 30s.

Temperatures are expected to plummet Saturday night due to
excellent radiational cooling under clear, dry conditions as a
result of strengthening high pressure. While records are unlikely
to be challenged, single digit low temperatures above and below
zero are likely in many valley locations. This will especially be
the case across SW Montana where there will be an added bonus;
freshly fallen snow.

Cold valley temperatures will continue through Thanksgiving
morning as high pressure remains dominant across Idaho and
Montana. Additionally, freezing fog and/or the persistent presence
of low stratus clouds are expected each day and in some places,
through the afternoon which will prevent daytime high temperatures
from warming significantly. As these inversions strengthen, air
quality will invariably start to suffer.

The ridge will be slow to breakdown on Thanksgiving Day with
slight chances for light precipitation starting in Idaho and
throughout the terrain of the Idaho/Montana border region. Better
chances for mountain snow and valley rain enter the forecast on
Friday and especially over the weekend.

AVIATION...Periods of snow showers will impact KBTM through
17/0300z. Expect mountain obscurations, lowering ceilings and
visibilities under snow showers. KMSO may also experience a snow
shower or two through mid evening as well as northeast winds
gusting to 20-25 mph through 17/0300z. KGPI can expect persistent
strong northeast winds around 20-25 mph with higher gusts through
17/1000z. Winds will gradually diminish by Saturday morning. KSMN
can expect a few showers through this evening.


MT...Winter Weather Advisory until 10 AM MST Saturday Butte/Blackfoot

Winter Weather Advisory until 10 AM MST Saturday Potomac/Seeley
Lake Region.


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