452
FXUS65 KMSO 042133
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
233 PM MST Thu Dec 4 2025

.DISCUSSION...

KEY MESSAGES:

-  A prolonged period of winter weather lasting through at least
   the weekend

-  Heavy mountain snow, along with a wintry mix in the valleys
   will make for difficult travel conditions

-  Gusty westerly winds on Saturday

-  Unsettled winter weather will continue into next week

The first of many plumes of moisture has moved into the Northern
Rockies today. This feature is causing light to moderate snow
across north central Idaho into west central and southwest
Montana. Accumulations on roadways have been relatively light so
far, but once the sun sets anticipate an uptick of snow cover
roads. Another concern will be wet roads where temperatures are
hover near to slightly below freezing have the potential to freeze
up tonight. Snow levels are expected to steadily climb tonight,
especially across north central Idaho. Many lower locations around
Grangeville and Orofino have been experiencing light snow or a
rain/snow mix this afternoon, tonight the expectation is for the
precipitation type to change over to all snow. The higher terrain
will remain all snow with 3 to 6 inches of new snow by Friday
morning, especially along the Montana/Idaho border. Another area
that appears to receive a significant amount of snow tonight is
along the Mission Mountains down into the northern Sapphires
range, impacting HWY200 from Bonner to Clearwater Junction and
I-90 from Bonner to Clinton. Numerous winter storm warnings and
advisories have been issued for areas that are expected to have
moderate to major impacts from the snow tonight.

The precipitation activity is expected to decrease in intensity
Friday morning with just some linger higher terrain snow showers.
Then a second plume of moisture will be making its way into the
Northern Rockies late Friday into Saturday. Snow levels are
expected to rise to during the afternoon and evening, but the
intensity of the showers could be strong enough Saturday evening
to cause the snow levels to be pushed back down. HiRes models are
showing the development of snow bands Saturday evening across
portions of west central and southwest Montana that might have
major impacts to the roads.

Snow showers will continue on Saturday, but the focus of the
precipitation will be along the Montana/Idaho border up into
Glacier National Park area. The remainder of the Northern Rockies
will encountered isolate to scattered showers during this time
frame, but gusty westerly winds will be the bigger impact. Wind
gusts up to 35 mph will be experienced across most of the region
Saturday afternoon. The I-90 corridor from Garrison Junction to
Anaconda appears to have the best chance of experience cross
winds.

Another plume of moisture appears to push through the Northern
Rockies Sunday night into Monday, followed by an atmospheric
river pushing in Tuesday into Wednesday. This atmospheric river
has the potential to cause snow levels to climb creating rain on
snow in the mid slopes and valleys. This event will have to be
watched for the potential of hydrological issues.

This active weather pattern is anticipated to linger across the
Northern Rockies through the remainder of the work week into the
following weekend.


&&

.AVIATION...Widespread lowered ceilings, terrain obscurations, and
localized visibility reductions will continue through the
forecast period due to snowfall. Surface winds will remain rather
light with some gusts toward 15 knots. There will be a lull in
shower activity through midday Friday before another surge of
moisture pushes into the region. Ridgetop winds will
increase out of the west and northwest through the day on Friday
and into Saturday. Surface wind gusts are expected up to 20-35
knots. Rain will begin mixing into snow showers by Friday evening
and through Saturday. Snow levels may be temporarily driven back
down to valley floors Friday and Saturday under any heavy
convective bands that set up.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning from 5 PM this afternoon to 5 PM MST
     Saturday for Bitterroot/Sapphire Mountains...Lower Clark
     Fork Region...Potomac/Seeley Lake Region.

     Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Friday for Butte/Blackfoot Region...Flathead/Mission
     Valleys...Missoula/Bitterroot Valleys.

     Winter Storm Watch from Friday afternoon through Sunday morning
     for West Glacier Region.

ID...Winter Storm Warning from 4 PM this afternoon to 4 PM PST
     Saturday for Northern Clearwater Mountains...Southern
     Clearwater Mountains.

     Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Friday for Eastern Lemhi County...Western Lemhi County.

&&

$$