238
FXUS65 KMSO 010928
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
228 AM MST Mon Dec 1 2025

.DISCUSSION...


KEY MESSAGES:

-  Widespread Winter Travel Impacts (TodayTue): Snow is expected
   to cover roads, creating slick conditions.

-  Active Pattern Continues (Late Week): A mix of moisture and
   cold ground temperatures could bring additional rounds of slick
   travel.

Confidence continues to increase regarding a widespread snow event
developing this afternoon and persisting through Tuesday. Snow is
expected to begin across northwest Montana as early as Monday
morning, becoming more likely by the afternoon. A primary concern
is the potential for wet surfaces to freeze rapidly after sunset
this evening; fresh snowfall on top of this ice could result in
hazardous travel conditions. Winter Weather Advisories have been
issued for northwest Montana to address this early onset. Snow
accumulations are likely to range between 2 to 5 inches. Flathead
Lake could enhance snowfall rates from Bigfork into the Many
Lakes Region and the foothills of the northern Swan Range this
evening.

Further south, the modified arctic airmass remains in place in
the Missoula and Bitterroot Valleys. Light snow is expected to
begin this afternoon, though impacts due to the snow will be
minor. As a second round of moisture arrives night snowfall rates
will intensify as the moisture overruns the much colder air in
place. The Tuesday morning commute is expected to be slick, with
snow- covered roads. Due to the expected impacts, Winter Weather
Advisories have been issued and go into effect this evening,
through Tuesday afternoon. Highway 12 in Idaho county has been
added to the advisories as well, with snow accumulations expected
from Lowell to Lolo Pass.

By Tuesday, a northerly flow will favor the lower elevations in
Idaho, particularly the Camas Prairie. As the trough shifts
southward, lingering snow showers could create additional slick
spots or black ice scenarios. Confidence isn`t as high for
accumulations in these areas, though advisories may need to be
issued here as well.

Following a brief lull Wednesday, active weather returns late
Thursday. A deep trough over the central Pacific will direct a
long fetch of subtropical moisture toward the Northern Rockies by
Friday and Saturday. Forecast details regarding precipitation type
remain complex. Both ECMWF and GFS ensembles suggest cold air
will remain entrenched across much of the regionexcept for
southern Idaho and Lemhi Countieswhile overrunning precipitation
erodes the cold dome. This setup creates the potential for a messy
mix of freezing rain, snow, and rain, alongside gusty winds. As
temperatures moderate and potentially cool again by Saturday, snow
levels may lower. Additionally, the prevailing northwest flow
could favor significant snow production in both valleys and
mountains, while leaving the Glacier Region vulnerable to
continued Arctic air intrusions.

&&

.AVIATION...A low stratus deck has developed over most of the
Northern Rockies this morning, with ceilings under 2000ft for
KPGI, KMSO and KHRF. The stratus is likely to remain in place
today as moisture slides south out of Canada this afternoon. This
will set the stage for at least light snow falling for several
hours this afternoon through Tuesday afternoon. For KGPI, light
snow is expected by 01/2000Z, and 02/0000Z for KMSO and KHRF. Snow
fall intensities will increase this evening and overnight, with 1
to 4 inches of snow accumulating by Tuesday afternoon for KGPI,
KMSO and KHRF.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory from 8 PM this evening to 5 PM MST
     Tuesday for Bitterroot/Sapphire Mountains.

     Winter Weather Advisory from 1 PM this afternoon to noon MST
     Tuesday for Kootenai/Cabinet Region.

     Winter Weather Advisory from 2 PM this afternoon to 5 PM MST
     Tuesday for Potomac/Seeley Lake Region...West Glacier
     Region.

     Winter Weather Advisory from 2 PM this afternoon to noon MST
     Tuesday for Flathead/Mission Valleys...Lower Clark Fork
     Region.

     Winter Weather Advisory from 8 PM this evening to 2 PM MST
     Tuesday for Missoula/Bitterroot Valleys.

ID...Winter Weather Advisory from 7 PM this evening to 4 PM PST
     Tuesday for Southern Clearwater Mountains.

&&

$$