Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 182128
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
228 PM MST Sun Feb 18 2018

...POOR TRAVEL CONDITIONS CONTINUE INTO TONIGHT...
...WIND CHILLS OF NEGATIVE 20 TO NEGATIVE 35 TONIGHT THROUGH
MONDAY MORNING...

.DISCUSSION...Cold air moving into western Montana and Idaho is
producing gusty north and east winds. These winds will spread
through north-central Idaho overnight and remain in western
Montana through much of Monday. Snow showers have been heavy at
times today, and are expected to maintain their strength through
the afternoon. Visibility beneath these showers has been very low
due to wind combining with moderate to heavy snow. Travel
conditions are extremely poor throughout western Montana and
improvements will be slow to occur. Snow showers are going to
taper from north to south, but travel impacts along the I-90
corridor and southward will continue due to snow and blowing snow
and snow-covered and icy roadways so the current Winter Storm
Warnings have been extended.

While snow decreases in western Montana tonight, north-central
Idaho will see another round of snow. Those that have only seen a
little snow so far in this storm are expected to receive
accumulations during Monday morning, and possibly into the
afternoon.

Besides the snow and poor travel conditions, very cold wind
chills are the next element to create impacts. Wind chill values
will flirt with the -30 degree range along the Continental Divide
tonight, with values in the -10 to -25 degree range further to the
west, including most of western Montana. North central Idaho may
not see as strong of a push of winds, thus wind chills will be
less of a concern there. That being said, temperatures are going
to be very cold come Monday morning with or without the addition
of wind, so take measures now to protect yourselves, your pets,
and your livestock that could be at risk.

The cold air continues into Tuesday, however the wind will finally
decrease and become calm by then. Instead of dealing with wind
chills, the region will become just downright cold. Ambient
temperatures will drop well into the negatives across western
Montana, especially in valleys of northwest Montana and along the
Continental Divide. Valleys along a line from Polebridge, Essex,
Seeley Lake, Ovando, and south to Butte could see temperatures
lower into the -20 to -35 degree range. (This is not wind chill
value: this is actual ambient temperature). The further west you
go, the "warmer" the temperatures are expected. Single digits to
-15 degrees are expected for mostly everywhere else in the
forecast area Tuesday morning.

While Tuesday should definitely be our coldest morning, Wednesday
morning will also be quite cold. High temperatures will struggle
to warm much during the day Tuesday, but will start to improve
greatly by Wednesday and Thursday.

The weather turns more active once again towards the end of the
week, with more snow likely across the Northern Rockies going into
next weekend.

&&

.AVIATION...Blowing snow with reduced visibility will continue at
KGPI and KMSO this evening and overnight as well. High winds up to
35 knots will continue to plague both of these terminals well into
Monday. In addition, scattered snow showers - which could be
moderate to heavy at times - will impact KMSO, KBTM, and KSMN now
through roughly 19/0600Z before precipitation finally tapers off.
Winds will remain gusty through the day Monday and will finally
decrease in intensity through Monday evening.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning until midnight MST tonight Butte/Blackfoot
     Region...Potomac/Seeley Lake Region.

     Wind Chill Advisory from midnight tonight to 1 PM MST Monday
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...
     Potomac/Seeley Lake Region.

     Winter Storm Warning until midnight MST tonight
     Bitterroot/Sapphire Mountains.

     Winter Storm Warning until midnight MST tonight
     Missoula/Bitterroot Valleys.

     Wind Chill Advisory from midnight tonight to 1 PM MST Monday
     Missoula/Bitterroot Valleys.

     Winter Storm Warning until midnight MST tonight Lower Clark Fork
     Region.

     Wind Chill Advisory from midnight tonight to 1 PM MST Monday
     Lower Clark Fork Region.

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

     Wind Chill Advisory until 1 PM MST Monday Flathead/Mission
     Valleys.

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

     Wind Chill Advisory until 1 PM MST Monday West Glacier Region.

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

     Wind Chill Advisory until 1 PM MST Monday Kootenai/Cabinet
     Region.

ID...Winter Weather Advisory until 1 PM MST Monday Eastern Lemhi
     County...Western Lemhi County.

     Winter Weather Advisory from 7 PM this evening to noon PST
     Monday Lower Hells Canyon/Salmon River Region...
     Orofino/Grangeville Region.

     Winter Weather Advisory until noon PST Monday Northern
     Clearwater Mountains...Southern Clearwater Mountains.

&&

$$



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