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afdmso

Area forecast discussion
National Weather Service Missoula Montana
237 PM MST Tue Feb 19 2019

..significant snow accumulations for north central
Idaho tonight through Wednesday...

Discussion...a winter storm will impact north central Idaho
tonight through Wednesday as an area of low pressure tracks across
eastern Washington into the Camas Prairie and the Clearwater
Mountains overnight tonight. Winter storm warnings are in effect
given an expected period of prolonged moderate to heavy snowfall
across the lower elevations of north central Idaho. Locations
along US 12 from Orofino to Lowell can expect to receive up to 8
inches of snow, although isolated higher amounts are possible.
Higher elevations areas along Highway 11, including Pierce should
see up to 10 inches or more of snow. Grangeville and vicinity,
including whitebird grade along US 95, will see a combination of
snow and blowing snow tonight as southwesterly winds increase
this evening. The lowest elevations around Riggins will not be
left out either, where 3 to 5 inches of snow is expected.

A period of light to moderate snowfall is also expected across
western Montana tonight through Wednesday and winter weather
advisories are in effect. Snow will develop tonight and continue
through Wednesday morning and will create a slick morning
commute. A relatively cold and moist air mass will become unstable
tomorrow afternoon and snow showers are expected to continue, with
snow briefly becoming heavy at times under these showers.
Attention then turns to an Arctic cold front which will move
across the Continental Divide Wednesday afternoon and will move
across western Montana by the evening hours. Breezy easterly
winds will develop behind the Arctic front and a few areas of
blowing snow will be a concern, especially along US 2 in Badrock
Canyon near Columbia Falls.

Thursday into Friday will continue with well below normal
temperatures and scattered snow showers under an upper level
trough.

Another active period of unseasonably cold and snowy weather is
anticipated late Friday through early next week (probably most of
next week as well). Several disturbances and associated moisture
will stream in from the west and interact with Arctic air ebbing
and flowing over The Divide. This will likely lead to periods of
light to moderate snow accumulations for all elevations but snow may
occasionally be heavy. Blowing and drifting snow may also be a
concern especially for northwest Montana and along The Divide. Travelers
should plan for periods of changeable, slick roadways and
difficult travel. Those expecting Newborn livestock should prepare
for more problematic times due to the cold and wind.



&&

Aviation...moisture is increasing from the west and producing
widespread snow as it encounters cold temperatures throughout the
region. Lowering ceilings and visibility, and continued widespread
obscured terrain are forecast by model cross sections through
tonight. Snow will continue through much of Wednesday morning in
north-central Idaho and western Montana. A low pressure center,
that is forecast to pass through north-central Idaho, will focus
the heaviest snow near the triple Point of WA/OR/ID. High
resolution guidance show snow to become showery during Wednesday
afternoon and a band of snow is likely to develop along the
leading edge of an Arctic boundary, which will move west of The
Divide during Wednesday afternoon and evening.




&&

Mso watches/warnings/advisories...
Montana...Winter Weather Advisory from 8 PM this evening to 9 PM MST
Wednesday Butte/Blackfoot region.

Winter Weather Advisory until 9 PM MST Wednesday
Bitterroot/Sapphire Mountains...Missoula/Bitterroot
valleys...Potomac/Seeley Lake region.

Winter Weather Advisory until 5 PM MST Wednesday Lower Clark
Fork region.

Winter Weather Advisory until 9 PM MST Wednesday
Flathead/mission valleys...West Glacier region.

Winter Weather Advisory until 9 PM MST Wednesday
Kootenai/Cabinet region.

Idaho...Winter Weather Advisory until 4 PM PST Wednesday northern
Clearwater Mountains.

Winter Storm Warning until 4 PM PST Wednesday lower Hells
Canyon/Salmon river region.

Winter Weather Advisory until 4 PM PST Wednesday southern
Clearwater Mountains.

Winter Weather Advisory until 5 PM MST Wednesday western Lemhi
County.

Winter Storm Warning until 4 PM PST Wednesday

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