486
FXUS65 KMSO 081945
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
145 PM MDT Thu Oct 8 2026

.DISCUSSION...


KEY MESSAGES:

-  Gusty west winds Friday afternoon will create near-critical
   fire weather conditions across southwest Montana, choppy
   conditions at area lakes, and hazardous crosswinds for high-
   profile vehicles on I-90 from Deer Lodge to Butte, and I-15
   south of Butte.

-  Strong northeast winds will develop Saturday, causing choppy
   waves that could pose a danger to docks and boats on the
   southwestern portion of Flathead Lake. Isolated power outages
   are possible across northwest Montana through Saturday night.

-  The first winter storm of the season is expected to bring wet,
   heavy snow, cold temperatures, and gusty northeast winds to the
   mountains and high valleys of west-central, southwest, and
   central Montana late Saturday through Sunday night. This heavy
   snow could damage trees and power lines, and will significantly
   impact backcountry recreation, hunters, and travel.

Thursday and Friday will be the last summer-like days for a while. On
Friday, a relatively dry cold front will move across the region. Southwest
winds will increase to 15 to 25 mph, bringing a 1 to 2 foot chop to
Flathead Lake. Stronger winds of 20 to 30 mph with gusts up to 45 mph are
possible from Lemhi County to southwest Montana. In addition to dangerous
crosswinds on north-south highways, the dry and windy conditions will
create near-critical fire weather conditions across southwest
Montana.

On Saturday, as a low pressure system moves onshore over Washington and
Oregon, northeast winds will increase across much of the region. At the
same time, cold, below-freezing air will push south from Alberta, Canada,
further increasing the northeast winds. Flathead Lake will again experience
choppy conditions, but from the northeast by Saturday afternoon. Northeast
winds of 15 to 25 mph with gusts to 35 mph could pose a danger to docks and
boats from Yellow Bay south and west toward the Narrows and Big Arm.

Moisture wrapping around the low pressure system over Oregon will move over
the cold air pushing south across western Montana Saturday night. Snow
levels will fall to the valley floors along and west of the Divide. The
cold air will weaken as it reaches the Idaho/Montana border, so snow levels
in central Idaho will remain higher, generally above 4000 feet.
Temperatures falling into the 20s at MacDonald Pass, combined with gusty
northeast winds and wet, heavy snow, will overcome the warm ground and make
travel conditions slick. This wet, heavy snow may also cause impacts to
power lines and trees. Other locations, including Georgetown Lake, Butte,
and Homestake Pass, could also experience winter-like conditions. The
highest probabilities for 3 inches of snow or greater exist in
these areas.

The heaviest precipitation will be with a narrow band that is currently
forecast to be over the Anaconda/Pintler Range and spreading east over
Homestake and MacDonald Passes. If this band were to shift further north,
areas around Seeley Lake and the Bob Marshall Wilderness could see a higher
impact, which would also allow rain to change over to snow in places like
Missoula. However, impacts should be minimal in the lower elevations, aside
from the chill.

With the latest information this morning, we decided to go with a Winter
Storm Watch for areas encompassing Homestake and MacDonald Passes and the
Georgetown Lake area near the Anaconda/Pintler Ranges. Lower elevations,
including Butte and Anaconda, will also see accumulating snow, though to a
lesser extent. For the mountains north and west of this region, including
the Bitterroot and Sapphire Ranges and the Seeley-Swan region, Winter
Weather Advisories were also issued.

In a rare circumstance, moisture from the remnants of Hurricane Rachel will
track northeast from California and Nevada toward the Yellowstone and
Wyoming area. We will be on the edge of this moisture, with lingering snow
possible Sunday into Sunday night. For example, Butte and Homestake Pass on
I-90 may continue to see snow Sunday night.

As the weather system pulls away, Monday may bring the first widespread
hard freeze of the season. Western Montana may see lows in the upper teens
to low 20s, while the lower elevations in north-central Idaho get close to
freezing.

&&

.AVIATION...VFR conditions will continue across the Northern Rockies
terminals through today under high pressure. Light terrain-driven winds and
mostly clear skies are expected, with a few passing high clouds. Strong
valley inversions will promote the development of localized morning
mist/fog near bodies of water, including area rivers and lakes on Friday
morning. A dry cold front will bring gusty west to southwest winds on
Friday afternoon. Terminals GPI, MSO, and BTM may experience the strongest
gusts between 25 and 35 knots.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Lake Wind Advisory from noon to 9 PM MDT Friday for
     Flathead/Mission Valleys.

     Winter Weather Advisory from 6 PM Saturday to 6 PM MDT Sunday
     for Bitterroot/Sapphire Mountains...Potomac/Seeley Lake
     Region.

     Winter Storm Watch from Saturday evening through Sunday
     afternoon for Butte/Blackfoot Region.

ID...None.
&&

$$