Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 042153

Area Forecast Discussion
National Weather Service Missoula MT
253 PM MST Sun Dec 4 2016



The high terrain has been seeing good snow accumulations since
last night but it has taken longer for many valley locations to
see snow. The transition to cooler and more unstable is currently
taking place which is now resulting in the formation of snow
bands. An impressive snow band has been moving south through the
Flathead and Mission valleys with 2.5 inches of snow being
reported as falling in less than 30 minutes in Bigfork. Current
satellite loops show widespread snow bands forming this afternoon,
so this afternoon and evening is the timeframe where places that
haven`t seen big impacts will see accumulating snow and slick
roadways. We are still concerned that main travel corridors will
become snow packed and icy with a combination of moderate to heavy
snow, increased wind, and falling temperatures during the evening.

The main front is still working its way into northern Montana
this afternoon and is forecast to pass late this evening through
tonight. Snow is being observed with this front so snow will
continue to be possible region-wide into tonight. Lingering snow
is likely to keep roadways slick for the Monday morning commute so
advisories and warnings remain for the evening through Monday
morning impacts. Colder temperatures are still expected tonight
with little change in temperature expected from Monday morning
through afternoon.

The main shot of arctic air will move into the region from the
east on Monday night. By Tuesday morning temperatures will drop to
the coldest of the season thus far along with very cold wind
chills of -10 to -20 degree to be common. Cold air will continue
to move into north central Idaho and western Montana on Tuesday so
temperatures will not warm much and become even colder for
Wednesday morning. Very cold wind chills will remain a factor
through Wednesday morning with 25 degree below zero wind chills
possible. The cold will remain through Thursday morning with many
valley locations to have their coldest morning of this week.

Besides the very cold temperatures, a disturbance moving in Monday
night will likely bring accumulating snow to central Idaho with
the greatest amounts expected to be in Idaho county. Whitebird
Grade is expected to see steady moderate snow with 3 to 6 inches
of snow possible on Tuesday. Even low elevation valleys such as
Riggins could see a few inches of snow. For western Montana, some
light snow showers will be possible on Tuesday mainly along and
south of the I-90 corridor.

The forecast becomes increasingly interesting for Thursday
through the end of the week. Model guidance remain in agreement
for Pacific moisture to move into the region for the end of the
week. The cold air that will be in place will make for a very
favorable, widespread snow pattern. If the weather pattern holds,
this could be a big snow producer for valleys and mountains. A
snowy pattern may even remain through the weekend.


.AVIATION...North central Idaho and western Montana are
transitioning into an unstable atmosphere as cold air moves in
from the north. Strong showers, some of which are organized into
snow bands, will pass through the region through late this
evening. Periods of moderate to heavy snow and gusty winds are all
likely into tonight. Snow intensities are forecast to decrease
overnight in most locations, although, northwest Montana,
including KGPI, can plan on snow and northeast winds with the
first piece of the arctic front. Winds will then become light for
Monday morning and model cross sections show enough moisture for
snow to continue through Monday morning.


MT...Winter Weather Advisory until 11 AM MST Monday Butte/Blackfoot

     Winter Storm Warning until 11 AM MST Monday Bitterroot/Sapphire

     Winter Weather Advisory until 11 AM MST Monday
     Missoula/Bitterroot Valleys.

     Winter Storm Warning until 11 AM MST Monday Lower Clark Fork

     Winter Weather Advisory until 11 AM MST Monday Flathead/Mission

     Winter Storm Warning until 11 AM MST Monday West Glacier Region.

     Winter Weather Advisory until 11 AM MST Monday Kootenai/Cabinet

     Winter Storm Warning until 11 AM MST Monday Potomac/Seeley Lake

ID...Winter Storm Warning until 11 AM MST Monday Eastern Lemhi
     County...Western Lemhi County.

     Winter Weather Advisory until 10 AM PST Monday ABOVE 3000 FEET
     for the Lower Hells Canyon/Salmon River Region...
     Orofino/Grangeville Region.

     Winter Storm Warning until 10 AM PST Monday Northern Clearwater
     Mountains...Southern Clearwater Mountains.


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