386
FXUS65 KMSO 040818
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
218 AM MDT Thu Sep 4 2025

.DISCUSSION...

KEY MESSAGES:

- Increased easterly winds expected Thursday into Friday.

- Pattern change to showers and thunderstorms begins this weekend.

A pattern change has begun as the ridge shifts slightly east,
setting up a period of persistent easterly to northeasterly winds.
This shift will bring several impactful weather conditions today
into tonight.

First, fire weather concerns will increase significantly as the
dry and hot conditions combine with strengthening winds. Already
dry conditions and gusty winds could allow any new fire starts to
spread.

Additionally, due to increasing confidence in the gusty east
winds, a Wind Advisory has been issued that goes in effect from 6
AM this morning to midnight tonight for the West Glacier Region
and Flathead Valley. Wind gusts could reach up to 40 mph, with
particular interest along west-facing slopes such as Highway 93
near the Whitefish Range, Highway 35 on the east side of Flathead
Lake, and the western slopes of the Swan Range. These areas may
see isolated stronger gusts, potentially leading to tree damage or
sporadic power outages.

Boaters on Flathead Lake should also be prepared for choppy waters
and hazardous conditions beginning Thursday morning. Theres a 70%
chance of wind gusts exceeding 30 mph, which may impact lake
activities throughout the day.

Lastly, this wind pattern may transport smoke from wildfires
burning in Alberta and Saskatchewan into the region. This could
result in hazy skies, reduced visibility, and localized air
quality degradation, particularly in the valleys.

Looking ahead to the weekend, the ridge will shift farther east,
allowing a return of southwesterly flow. This will bring in a
cooler and more humid airmass, with temperatures trending closer
to seasonal norms. Scattered showers and thunderstorms are also
possible, with atmospheric moisture levels reaching 150200% of
normal. This raises a marginal risk of excessive rainfall,
particularly over burn scars and steep terrain, where localized
runoff or debris flows may occur.

Extended outlooks continue to support a cooler and wetter pattern
for much of next week.

&&

.AVIATION...A backdoor cold front is moving across the region
today. This is causing a shift to east winds, and in some places
strong Foehn winds on west aspects. The incoming air mass will
also bring quite a bit of smoke from wildland fires in Canada.
Little to no precipitation is expected east of the Continental
Divide and at regional terminals.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Wind Advisory from 6 AM this morning to midnight MDT tonight for
     Flathead/Mission Valleys...West Glacier Region.

ID...None.
&&

$$