912
FXUS65 KMSO 200903
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
203 AM MST Sat Dec 20 2025

.DISCUSSION...

KEY MESSAGES:

 - Expanding Snow Showers: A shortwave trough will arrive this
   afternoon, causing mountain snow showers to become more
   widespread, especially north of Highway 12/200.

Current radar and satellite show orographic (terrain-forced) snow
showers continuing across the mountain passes along the ID/MT
border and throughout Northwest Montana, including the West
Glacier region.

A weak shortwave trough is currently tracking toward the region.
As it arrives this afternoon, it will tap into lingering moisture
and instability to expand shower activity. Snow showers will
become more frequent across the valleys and mountains alike. While
valley accumulations will be light and spotty, mountain passes
could see quick bursts of heavy snow, leading to rapidly changing
visibility and slick driving conditions.

As skies attempt to clear late tonight, temperatures will drop
well below freezing. Any roads that remain wet or slushy from
today`s showers have an increased risk of icy patches.

Sunday and Monday:
The next weather system is on track to arrive by Sunday afternoon,
but models are trending quicker with the arrival of the initial
moisture which may lead to valley and mountain snow during Sunday
morning. Accumulations are likely for Lolo, Lookout, and Marias
passes by Monday Morning. Rising snow levels late Sunday may
transition valley snow over to rain, creating a messy Monday
morning commute.

Tuesday through Friday:
The active weather pattern persists through next week. While no
single "major" storm is currently locked in, several smaller
disturbances will keep the region unsettled. General trends
suggest mild temperatures and continued periodic mountain snow.


&&

.AVIATION...Showers continue along the ID/MT border and through
northwest Montana, obscuring terrain and causing periodic lowered
ceilings and reduced visibility. Convective snow showers will
increase with a shortwave trough this afternoon into the evening
hours. Continued terrain obscurations and brief visibility and
ceiling reductions will linger into the evening. Southwest wind
gusts of 15-25 kts also return to most valleys by late this
morning.

&&

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

ID...Winter Weather Advisory until 10 AM PST this morning for
     Southern Clearwater Mountains.

&&

$$