595
FXUS65 KMSO 182024
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
124 PM MST Tue Nov 18 2025

.DISCUSSION...

KEY MESSAGES:

- Foggy Mornings: Areas of valley fog are likely each morning
  through Friday.

- Weekend Moisture: A minor Atmospheric River will bring
  widespread precipitation this weekend. Snow levels will remain
  relatively high above 5000 ft.

- Thanksgiving Week: A sharp cold front could bring some low-
  elevation snow but still a lot of uncertainty on the details.

A weak weather system may brush the region on Wednesday, bringing
increased cloud cover and a chance of light valley rain/snow and
high-elevation snow showers to northwest Montana and the Glacier
Park region. However, moisture is limited, and this system will
bring mainly light accumulations above around 3,500 feet.
Temperatures will remain mild, with valley highs generally in the
40s. However, areas with persistent fog may struggle to get out of
the 30s.

A mild weather pattern will dominate the Northern Rockies through
the end of the week. High pressure is generally overhead,
trapping air in the valleys. The primary near-term forecast
challenge will be the daily cycle of valley fog and low clouds.

The weather pattern begins to shift on Friday as the high-
pressure area weakens, allowing Pacific moisture to stream into
the region. The weekend Atmospheric River (a long plume of
moisture directed at the Pacific Northwest) will bring rain and
snow into western Montana and north-central Idaho starting
Saturday. This system is warmer, with snow levels rising to
between 4,500 and 5,500 feet. Valley locations can expect periods
of rain, while mountain passes (Lookout, Lolo, Marias) will likely
see accumulating snowfall and slushy road conditions.

Attention turns to a cold low-pressure system moving south from
the Gulf of Alaska early next week. There is strong model
agreement for a sharp cold front to pass through the region
sometime Monday or early Tuesday. This setup favors a transition
from rain to snow on valley floors, followed by temperatures
dropping closer to normal. Precipitation amounts vary greatly:
anywhere from only a dusting on mountain passes to 4 to 6 inches
of snow in the mountains through Tuesday morning.

By Wednesday, there is still a 60 to 80 percent chance that highs
could be at or below freezing across western Montana, but milder
in the lower elevations of Idaho (30s to low 40s). These chances
decrease by Thanksgiving into Friday, which suggests milder
conditions. Snow showers could persist in the mountains Tuesday
into Wednesday. This common pattern of colder air moving in after
the front could also bring periodic snow showers down to some
valley floors.

Forecast models are increasingly agreeing on a push of Pacific
moisture by the day after Thanksgiving (Friday) and/or into
Saturday. This could bring a chance for snow to the region, though
snow levels are still uncertain (ranging from 1,000 to 2,500 feet
on Friday).


&&

.AVIATION...Shower activity is widely scattered across western
Montana and north central Idaho. Localized obscurations of the
terrain and lowered visibility can be expected with showers. This
activity will generally shift focus into north-central Idaho and
southwest Montana after 19/0000z this evening. A period of lowered
visibility and ceiling may occur through roughly 19/0600z for
airfields KHRF and KBTM.

The upper level trough will pass through northwest Montana between
19/0900z and 19/1500z, bringing another round of widespread shower
activity, mainly along and north of Highway 2. A mix of rain and
snow down to roughly 3500 feet will cause widespread obstruction
of the terrain and lowered visibility, including at KGPI.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$