923
FXUS65 KMSO 111914
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
114 PM MDT Sat Oct 11 2025

.DISCUSSION...

KEY MESSAGES:

-  Widespread winter travel impacts are expected Sunday through
   Monday in northwest Montana and over mountain passes as snow
   levels fall to valley floors, creating difficult travel for
   the Monday morning commute.

-  Damaging northeast winds gusting 40-50 mph in northwest Montana
   Sunday night into Monday threaten to cause power outages and
   falling trees, a risk amplified by heavy snow on leafy branches and
   unfrozen ground.

-  The coldest air of the season arrives Monday, creating wind chills
   in the teens and 20s.

An unseasonably cold and potent trough will bring an abrupt end
to the mild autumn conditions of late. The initial cold front has
already ushered in cooler temperatures and scattered showers.
However, a more significant push of cold, arctic air will arrive
Sunday, causing snow levels to fall to most valley floors by
Monday morning, especially in western Montana.

The primary period of concern for winter travel impacts over
mountain passes begins this evening along the Continental Divide
(Marias Pass) and spreads westwards Sunday through Monday morning.
Valleys in northwest Montana face a dual threat: slick conditions
during the initial rain-to-snow transition Sunday morning,
followed by accumulating snow and icy conditions for the Monday
morning commute. By Monday morning, accumulating snow and
difficult travel are expected to become more widespread, including
the Butte/Blackfoot region. Monday will be the coldest day, with
morning wind chills in the teens and 20s combining with gusty
winds to create areas of blowing and drifting snow, especially
near mountain passes.

Our forecast confidence is increasing for a period of high-impact,
potentially damaging winds across northwest Montana from Sunday
night into Monday. Northeasterly wind gust of 40 to 50 mph are
expected, especially through channeled terrain in the eastern
Flathead valley, southeastern portions of Flathead Lake and
through the mountainous terrain. The primary threat is exacerbated
by several unique factors. Heavy, wet snow above 3000 feet on
Sunday/Sunday night will accumulate on trees that have not yet
lost their leaves, increasing the potential for significant branch
and tree failure. This is compounded by wet, unfrozen ground,
which makes trees more susceptible to the seasonally abnormal
northeasterly wind direction. Key impacts include the potential
for widespread power outages, falling trees, and dock damage along
the southern shores of Flathead Lake.

Although temperatures begin to moderate some on Tuesday, an
overall active and cool weather pattern is anticipated for much
of next week.

&&

.AVIATION...Aviation conditions are expected to deteriorate
significantly across western Montana and north central Idaho
tonight, lasting into Monday as a potent trough and approaching
arctic airmass introduces unseasonably cold air to the region. VFR
conditions will transition to widespread MVFR/IFR with lowering
ceilings and visibility in snow. Snow levels will drop across
northwest Montana to most valley floors by 12/1200z. In addition,
northeasterly winds will develop through the day Sunday, then
strengthen Sunday night into Monday, with gusts up to 40 kts
possible. These winds will create the potential for low-level wind
shear, significant terrain-induced turbulence, and potentially
prohibitive crosswinds. The most significant impacts to local
airfields will occur at KGPI, first due to the onset of
accumulating snow early Sunday morning, then secondly due to
strong northeasterly winds gusting to 40kts Sunday night into
Monday morning.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory from 6 PM this evening to noon MDT
     Monday for Bitterroot/Sapphire Mountains...Butte/Blackfoot
     Region...Lower Clark Fork Region...Potomac/Seeley Lake
     Region.

     Winter Storm Warning from 9 PM this evening to noon MDT Monday
     for Kootenai/Cabinet Region.

     Winter Storm Warning from 6 PM this evening to noon MDT Monday
     for West Glacier Region.

     High Wind Watch from Sunday evening through Monday morning for
     Flathead/Mission Valleys.

ID...Winter Weather Advisory from 5 PM this afternoon to 11 AM PDT
     Monday for Northern Clearwater Mountains...Southern
     Clearwater Mountains.

     Winter Weather Advisory from 6 PM this evening to 6 AM MDT
     Monday for Eastern Lemhi County...Western Lemhi County.

&&

$$