944
FXUS65 KMSO 102001
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
201 PM MDT Fri Oct 10 2025

.DISCUSSION...

KEY MESSAGES:

- Scattered showers and isolated thunderstorms this evening
  through Saturday.

- Widespread mountain snow begins late Saturday night into Sunday
  morning, with heaviest amounts above 4,500-5,000 feet.

- Snow levels drop to valley floors along the divide and in
  northwest Montana Sunday night into Monday morning.


Southwesterly flow aloft will persist over the Northern Rockies
tonight allowing some weak disturbances to move through the
region. These features will kick off a few light showers and
potential thunderstorms. The first couple rounds of showers could
create gusty outflow winds.

A trough of low pressure will move across the Northern Rockies on
Saturday. This trough will bring significantly cooler air and
scattered rain showers. The heaviest precipitation appears to be
draped across Lemhi county into southwest Montana.

An arctic airmass is anticipated to drop southward out of central
Canada Saturday night causing upslope flow along the Continental
Divide. This flow pattern will enhance the precipitation around
Glacier National Park into the Bob Marshall wilderness. Snow
levels will be dramatically drop to around 3000 feet by Sunday
morning around the park. The area will receive several inches of
new snow by Sunday morning with a high potential for wet roads
experiencing a flash freeze during the overnight hours as
temperatures drastically drop.

A secondary low pressure system digs into Washington on Sunday
causing a stream of precipitation over the Northern Rockies
especially northwest Montana. Sunday night as the low digs
southward into Oregon, the arctic air will be pulled further into
western Montana causing gusty easterly winds. The combination of
easterly winds at the surface along with moisture stream into from
the west due to low pressure system will create an overriding snow
event with extreme northwest Montana have the best potential for
high impacts. The valleys of northwest Montana could experience 1
to 4 inches of snow Sunday night into Monday morning while the
higher terrain could receive up to a foot or two of snow. The
heavy wet snow this time of year could create broken tree branches
and power outages due to the extent of leaves that remain on the
trees.

The low pressure system digs down into California Monday into
Tuesday. The placement of this system will limit the shower
activity over the Northern Rockies, but the cold air will remain
in place. Clearing skies and relaxing winds should allow
temperatures to drop dramatically Monday night into Tuesday
morning. Most valleys of Northern Rockies should have Tuesday
morning temperatures readings in the teens to mid 20s while the
low valleys of north central Idaho being in the 30s to low 40
degrees.

&&

.AVIATION...Widespread VFR weather conditions today will begin to
deteriorate this afternoon with the onset of showers and isolated
thunderstorms which could create brief gusty outflow up to 30
knots mainly after 10/2200z. The strongest winds and greatest
threat for thunderstorms will be near KBTM with surface gusts
above 20 knots are expected into the evening. Sustained southerly
ridgetop winds will remain in the 15-20 knot range, becoming
increasingly southwesterly into tomorrow. There is potential for
lowered ceilings and valley fog especially near KGPI, KMSO, by
Saturday morning after 11/1200z. Scattered shower chances continue
for most areas through the day on Saturday with snow/freezing
levels lowering through 6,000 ft MSL.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory from 6 PM Saturday to noon MDT Monday
     for Bitterroot/Sapphire Mountains...Butte/Blackfoot
     Region...Lower Clark Fork Region...Potomac/Seeley Lake
     Region.

     Winter Storm Watch from Saturday evening through Monday morning
     for Kootenai/Cabinet Region.

     Winter Storm Warning from 6 PM Saturday to noon MDT Monday for
     West Glacier Region.

ID...Winter Weather Advisory from 5 PM Saturday to 11 AM PDT Monday
     for Northern Clearwater Mountains...Southern Clearwater
     Mountains.

     Winter Weather Advisory from 6 PM Saturday to 6 AM MDT Monday
     for Eastern Lemhi County...Western Lemhi County.

&&

$$