Snow Squall Warning 4, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
249 PM MST Tue Feb 1 2022

.DISCUSSION...The arctic cold front pushed through Essex on US
Highway 2 and across eastern portions of the Glacier National
Park as of 100pm MST this afternoon. The arctic boundary will
push into the Flathead and Mission Valleys and through the
Potomac/Seeley Lake areas during the evening commute (3-6 pm). The
front will then track south and west of the I-90 corridor between
9 pm and midnight. A brief period of intense snow and strong
east- northeast winds will create difficult travel conditions as
the front passes. Widespread winter driving conditions are
expected as wet roads quickly freeze up as temperatures fall into
the teens and single digits. Snow Squall Warnings may be issued if
a line of intense snow and strong winds materialize on the
leading edge of the arctic front.

Ahead of the arctic frontal boundary, widespread snow showers
will continue across western Montana and in the Clearwater
Mountains. A cold and unstable northwesterly flow has allowed for
snowfall rates to reach 1 inch per hour at times.

Wind chill advisories have been issued across the West Glacier
region and in the Flathead and Mission valleys tonight into
Wednesday morning. Wind Chill values as low as 30 below as
expected as temperatures fall below zero and gusty northeast winds
continue overnight.

Wednesday snow showers will exit the region around noon. The
arctic air will gradually move east of the region as high pressure
builds over the Pacific Northwest and Eastern Pacific. This leaves
the Northern Rockies under a general north-northwest flow pattern.
A weak short wave will move through this flow Thursday resulting
in some snow showers over central Idaho and parts of
northwest/west central Montana. The main impact from snow will be
a couple of inches of snow over Lookout/Lolo pass.

Friday the ridge builds a little more over the region. Warmer
temperatures with a mix of sun and clouds will occur over the
region. However late Friday afternoon another short wave with a
little more energy or punch to it will move in from British
Columbia into Northwest Montana. This weather system will move
through the entire Northern Rockies Friday evening through
Saturday morning. Several inches of snow are expected over Lolo,
Lookout and Marias passes, making travel difficult.

Cold and unstable air behind this front will continue to trigger
scattered snow showers through Saturday afternoon.

Sunday and Monday dry weather will return to the region as a
ridge builds over the region. Inversions that set up will bring
fog to area valleys.

Model ensembles are pretty consistent building a strong ridge
over much of the western U.S. for the middle to end of next week.
This scenario will lead toward an extended period of strong
inversions, something favorable for valley fog and deteriorating
air quality.

&&

.AVIATION...Snow showers will impact all terminals through
02/0600z. Some showers may be strong and produce a quick inch or
two of snow. Expect quick lowering visibilities and ceilings as
snow showers pass through the region. Arctic air will move over
the Continental divide and bring gusty northeast winds to KGPI
resulting in blowing snow between 01/0300z and 01/1200z. This
weather system and scattered snow showers will linger over KMSO
and KBTM through 01/1400z.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 3 AM MST Wednesday
     Missoula/Bitterroot Valleys.

     Winter Weather Advisory until 3 AM MST Wednesday
     Flathead/Mission Valleys.

     Wind Chill Advisory from 11 PM this evening to 11 AM MST
     Wednesday Flathead/Mission Valleys.

     Winter Weather Advisory until 3 AM MST Wednesday West Glacier
     Region.

     Wind Chill Advisory from 8 PM this evening to 11 AM MST
     Wednesday West Glacier Region.

     Winter Weather Advisory until 3 AM MST Wednesday
     Bitterroot/Sapphire Mountains.

     Winter Weather Advisory until 3 AM MST Wednesday Potomac/Seeley
     Lake Region.

     Winter Weather Advisory until 3 AM MST Wednesday Butte/Blackfoot
     Region.

     Winter Weather Advisory until 3 AM MST Wednesday Lower Clark
     Fork Region.

ID...Winter Weather Advisory until 2 AM PST Wednesday Lower Hells
     Canyon/Salmon River Region...Orofino/Grangeville Region.

     Winter Weather Advisory until 2 AM PST Wednesday Northern
     Clearwater Mountains...Southern Clearwater Mountains.

&&