Polson, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

205
FXUS65 KMSO 052321
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
521 PM MDT Fri Sep 5 2025

.DISCUSSION...

KEY MESSAGES:

- East winds continue until Saturday or Sunday, though relatively
  light

- Thunderstorms possible tomorrow across primarily north central
  Idaho, spreading into all of western Montana and north central
  Idaho by Sunday

- Confidence in a pattern change to cooler and wetter weather by
  mid week

Light east winds continue today, but have weakened considerably.
Degraded air quality continues across much of western Montana and
north central Idaho, with the thicker smoke currently occurring
through central Idaho and near the western Montana border. Little
change is anticipated through the weekend, and in fact conditions
may worsen in western Montana as winds slowly shift back towards a
westerly direction towards Sunday.

High pressure will slowly be moving eastwards this weekend placing
western Montana and north central Idaho under southwest flow
aloft. This will usher in increased moisture and disturbances
capable of producing thunderstorm activity. Initially on Saturday,
most of this activity will be focused in north central Idaho
(Lemhi, Clearwater and Idaho). While storms will likely have some
rainfall associated with them, the bigger threat will be lightning
and gusty outflow winds. The one limiting factor could be the
smoke, which may limit heating and instability enough to squash
some of the convective activity.

By Sunday, thunderstorms will be possible across all of western
Montana and north central Idaho. Atmospheric moisture will have
increased enough that storms should be capable of locally heavy
rainfall, in addition to lightning and gusty outflow winds.

Confidence in a pattern change towards the middle of next week
continues to increase, with nearly all forecast models bringing
a trough of low pressure through the region. The highest
confidence lies in much cooler temperatures (mid 60s to 70s) by
Thursday, which is roughly 5 to 10 degrees below normal for this
time of year. There is still some discrepancy in how much
precipitation will occur, but wetting rains (0.10" or more) look
likely by Thursday with a generally 60 to 90 percent chance. A
more significant rainfall event (0.50" or more) is less likely,
but probabilities for those amounts continue to increase,
particularly through north central Idaho and northwest Montana.
This pattern change towards cooler and wetter weather should also
help improve air quality by the middle to end of next week.

&&

.AVIATION...Lingering smoke will continue to obscure the terrain
and cause minor decreases in visibility area wide. Thicker smoke
is focused through north central Idaho, including near KGIC, which
may limit visibility into MVFR conditions locally. Smoke will
likely linger across the region through the weekend, and possibly
degrade conditions further across western Montana as winds turn
more westerly late Saturday into Sunday. Otherwise, generally
clear skies are anticipated into Saturday. By Saturday afternoon,
showers and thunderstorms will be possible, mainly across north
central Idaho, possibly impacting KSMN. The main threats with
storms will be gusty outflow winds and lightning.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$