Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 261058

Area Forecast Discussion
National Weather Service Missoula MT
358 AM MST WED NOV 26 2014

...Arctic cold front bringing much colder temperatures and
potentially heavy snow Friday night into Saturday...

.DISCUSSION...The band of precipitation that brought light to
moderate snow across north central Idaho and west-central/southwest
Montana overnight will continue to shift northward into northwest
Montana through the day. This will bring a gradual decrease in
precipitation from south to north, with northwest Montana
maintaining precipitation through much of the day. Snow levels
will be on the rise today, so with time valley locations will
largely change over to rain, or a rain snow mix. Valleys of
northwest Montana will remain snow the longest and thus could
continue to accumulate another 1-4 inches through early
afternoon. Travel impacts due to snow and slick roads will
continue, particularly through the morning hours, and thus winter
weather highlights will continue.

Thanksgiving continues to look to be the most mild day of the
week, with fairly warm temperatures for late November. Showers
will continue, especially across northwest Montana.

Beginning on Friday, a more complicated weather scenario will
begin to pan out. An upper level trough and Pacific cold front
will begin to move through the region. A good feed of moisture
will produce widespread precipitation, which could become
moderate to heavy at times. Initially snow levels will start
rather high, above most valley locations. However, mountain passes
look to be affected by accumulating snow during the day. By Friday
night, an arctic cold front will begin to move south out of
Canada, causing snow levels to crash to the valley floors first in
northwest Montana late Friday night, then into the rest of western
Montana and north central Idaho through the day Saturday. The
moisture feed will still be in place as snow levels crash, which
could lead to some significant snowfall amounts in the valleys
Saturday. Exact amounts are very dependent on the timing of cold
air, however widespread travel impacts are possible. In addition
to the snow, roads may also be impacted by a flash freeze of
moisture to the roadways as the cold air surges through the area.
Gusty winds may also develop for a time, causing areas of blowing
snow, lowered visibility and low wind chill values, especially
through tight canyons such as Hellgate (near Missoula) and Badrock
(near Columbia Falls).

Precipitation should largely exit the region by Sunday, however a
much colder airmass will be left in its wake. Single digits to
even below zero temperatures are possible by Sunday morning in
western Montana. Idaho will also see colder temperatures, though not
quite as cold as in Montana. Thankfully, the cold airmass is not
expected to linger for long, and we should see a gradual warm up
through the early part of next week.


.AVIATION...Snow currently falling at KMSO, KGPI, and KBTM is
expected to change to rain from south to north this morning as
temperatures rise above freezing, with KGPI being the last to let
go of snow showers in the early afternoon. KSMN should hold onto
fog through the morning, and with recent moisture, patchy fog is
not out of the question for other area TAF sites. Model profiles
show the atmosphere drying somewhat during the afternoon, but
remaining moisture will keep chances for rain around for Montana
terminals throughout the day. Winds will be light, below 10kts.


MT...WINTER WEATHER ADVISORY until 11 AM MST this morning
     Missoula/Bitterroot Valleys.

     WINTER WEATHER ADVISORY until 11 AM MST this morning Lower Clark
     Fork Region.

     WINTER WEATHER ADVISORY until 11 AM MST this morning
     Flathead/Mission Valleys...Kootenai/Cabinet Region.

     WINTER STORM WARNING until 11 PM MST this evening West Glacier

     WINTER WEATHER ADVISORY until 11 AM MST this morning
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region.

     WINTER STORM WARNING until 11 AM MST this morning Potomac/Seeley
     Lake Region.

ID...WINTER WEATHER ADVISORY until 4 AM PST early this morning ABOVE
     4000 FEET for the Northern Clearwater Mountains...Southern
     Clearwater Mountains.


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