Hamilton, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

945
FXUS65 KMSO 220855
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
155 AM MST Mon Dec 22 2025

.DISCUSSION...

KEY MESSAGES:

 - Slick Travel Conditions: Trapped cold air in the valleys will
   lead to a messy mix of snow and wintry mix through this
   morning. Expect slick condition at times including the threat
   for black ice on roads and overpasses.

 - Unsettled Holiday Week: A series of disturbances will keep the
   region wet and unsettled through Christmas. A stronger cold
   front on Friday will likely transition all valley precipitation
   back to snow.

 - New Year`s Eve Outlook: A potential atmospheric river could
   bring milder, wetter, and windier conditions to end the year.

A complex weather pattern continues across the Northern Rockies
as moist Pacific air overrides stubborn, cold air trapped in the
valleys. This setup will create a variety of precipitation types
and travel hazards through the early part of the week, followed by
a series of storms leading into the Christmas holiday.

The primary concern today is the persistent "cold pool" in the
valleys. While weather models often try to wash this cold air out
too quickly, local observations show it remains firmly in place.
This means that many valleys, including the Salmon, Missoula,
northern Bitterroot, and Flathead Valleys, will deal with snow and
a wintry mix.

Winter Weather Advisories remain in effect through this morning
to account for slushy accumulations and the development of black
ice on cold pavement. By Tuesday, another pulse of moisture
arrives. This will bring more light snow to the mountain passes
and a likely wintry mix to the valleys Tuesday night. Temperatures
will remain marginal, making the difference between a wet road
and an icy road very narrow.

Wednesday through Sunday: The pattern remains very active through
the Christmas holiday. A deep "dip in the jet stream" (trough)
over the eastern Pacific will eject several waves of moisture into
the region.

Christmas Eve/Day: We are watching for a "wedge" of Arctic air to
potentially spill over the Continental Divide. If this happens,
areas near Marias Pass and Essex could see a sharp drop in
temperatures and an increase in snow. For the rest of the area,
expect periodic rain and snow showers to continue through the
holiday.

Friday Front: A more robust cold front is forecast to sweep
through on Friday. This will bring a much cleaner transition to
snow for the valley floors as snow levels lower.

Next Weekend: Conditions look to turn cooler with persistent
mountain snow showers, though the heavy, organized precipitation
may take a brief break before a potential "Atmospheric River"
targets the region for New Years Eve.


&&

.AVIATION...The main concern is the persistence of low ceilings
and mixed precipitation types. With the forecast trending colder,
terminals such as KSMN, KGPI, and KMSO are more likely to see
periods of snow or wintry mix rather than a clean switch to rain.
Expect IFR/LIFR conditions to dominate as the low levels remain
saturated. Mountain obscuration will be widespread. Low- Level
Wind Shear (LLWS) may be present at times as strong westerly flow
aloft overrides the trapped valley cold pools after 1200Z this
morning across southwest Montana and along the Divide. Expect more
consistent improvements to visibility and ceiling heights after
around 1800Z, along with valley wind gusts of 12-22 knots through
the afternoon.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 11 AM MST this morning for
     Butte/Blackfoot Region...Flathead/Mission Valleys...
     Kootenai/Cabinet Region...Lower Clark Fork Region...
     Missoula/Bitterroot Valleys...Potomac/Seeley Lake Region...
     West Glacier Region.

     Winter Weather Advisory until 9 AM MST this morning for
     Bitterroot/Sapphire Mountains.

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

     Winter Weather Advisory until 9 AM MST this morning for Eastern
     Lemhi County...Western Lemhi County.

&&

$$