904
FXUS65 KMSO 242101
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
201 PM MST Mon Nov 24 2025

.DISCUSSION...


KEY MESSAGES:

- Backdoor Cold Front: Across Glacier Region this evening
  producing snow, falling temperatures, and difficult travel.

- Unsettled Holiday Travel (Wednesday & Thanksgiving): Light snow
  returns Tuesday night/Wednesday morning. Snow levels rise and
  precipitation transitions to a rain/snow mix later on Wednesday
  for most valleys.

- Potential Arctic Intrusion Late Week (Nov 29-30): Please
  monitor the forecast closely if you have post-Thanksgiving
  travel plans.

Today and tonight:
A cold front passed through the region this morning, with surface
observations showing modified arctic air now banking against the
Divide in the Glacier region. The heaviest precipitation has
concentrated over the Northwest Montana ranges above 4,500-5,000
feet, where 1.00-1.50 inches of precipitation has fallen across
the Whitefish, Swan, and Cabinet Ranges.

Model guidance indicates the modified arctic front will slowly
spill over the Divide into Flathead County this evening. This will
bring periods of moderate to heavy snow and falling temperatures,
leading to difficult travel conditions for US Highway 2 from West
Glacier to Marias Pass. High-resolution models suggest the
Flathead Valley may see a brief period of snow; however, mild
surface temperatures should limit accumulations and impacts there.

Tuesday through Thanksgiving Day (Thursday):
Tuesday begins as a quiet weather day. A stream of sub-tropical
moisture will enter north-central Idaho and far northwest Montana
by evening, gradually spreading light snow across the rest of the
Northern Rockies into Wednesday morning. Snow levels are forecast
to rise from 2,000 feet Tuesday night/Wednesday morning to
3,000-3,500 feet by Wednesday afternoon along and south of the
I-90 corridor. Recent model trends suggest cold air may remain
trapped in the valleys of Northwest Montana until late Thursday
morning. Snow accumulations look light, around one inch or less
for valleys and 2 to 5 inches on the passes through Thanksgiving,
but this will be enough to cause at least minor travel impacts.

Friday through Next Week:
We are closely monitoring the Friday through Sunday timeframe,
which begins with the passage of a Pacific trough and cold front.
Snow levels will fall to valley floors across northwest Montana on
Friday, with a 70% chance for widespread accumulating snow by
evening. Mountain passes will likely see periods of moderate to
heavy snow, especially along the ID/MT border and northwest
Montana ranges.

Forecast confidence decreases Saturday into Sunday due to high model
variability regarding a potential arctic intrusion. The primary
challenge remains the depth and westward progression of this cold
air:

- Friday Evening: There is medium-to-high confidence (70% chance)
  that arctic air will bank along the Divide in northwest
  Montana.

- Saturday: Uncertainty increases regarding the westward push.
  Approximately 30% of ensemble clusters depict arctic air rushing
  across western Montana. The majority (70% of members) suggest a
  slower progression, with a 50% chance of the deeper cold air
  reaching the Flathead Valley by Saturday afternoon.

- Sunday: A secondary shortwave within the northwest flow is
  expected to help pull arctic air over the Divide Saturday night
  into Sunday (70% chance to reach the ID/MT border).

Temperature Impacts: Current probabilities indicate a 50-70% chance
of lows dipping into the single digits (or colder) along the Divide
by Sunday morning, with a 30-50% chance for remaining western
Montana valleys. This period warrants close monitoring due to the
potential for widespread travel impacts.

Extended Outlook: An active northwest flow pattern continues into
next week, bringing snow chances and additional episodes of
arctic air potentially spilling over the Divide. /AL

&&

.AVIATION...A cold front pushed through the Northern Rockies today
leaving behind gusty west winds and scattered snow showers. The
winds and shower activity is expected to diminish after sunset
this evening. The exception will be across for Flathead county
region where wrap around snow associated with the exiting system
will cause moderate to heavy snow during the evening then diminish
after sunset. This wrap around precipitation has the potential to
impact KGPI between 24/22z to 25/03z with reduced visibility and
lowered ceilings. Today`s precipitation should allow for the
development of patchy fog and/or low stratus in the valleys by
Tuesday morning.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 11 PM MST this evening for West
     Glacier Region.

ID...None.
&&

$$