951
FXUS65 KMSO 071908
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
108 PM MDT Sun Sep 7 2025

.DISCUSSION...

KEY MESSAGES:

-  Decreasing smoke/improving air quality this afternoon and
   tonight

- Thunderstorms this afternoon/evening featuring gusty outflow
  winds

- Pattern change to cooler and wetter weather Tuesday onward

Some good news as southwest flow ahead of an upper level trough is
ushering the dense smoke northward and gradually out of the
Northern Rockies. Smoke may be stubborn to completely mix out of
the valleys but certainly improvement in air quality is
anticipated into Monday.

Increasing instability will interact with mid-level moisture to
produce a round or two of showers and thunderstorms this
afternoon/early evening. The main area of focus will be from
Flathead Lake southward with gusty outflow winds of 35-45 mph as
the main concern. A few showers will likely continue into early
Monday, particularly across northwest Montana. Another round of
scattered showers and a few thunderstorms are anticipated on
Monday afternoon.

Beginning Tuesday lasting through the workweek, a large trough
will wobble across the Pacific Northwest, eventually reaching the
Northern Rockies. Southerly flow will transport abundant moisture
into the area leading to periodic showers and occasional
thunderstorms, most concentrated in the afternoons/evenings.
Locally heavy rain is a possibility with a very slight chance
(5-10%) of debris flows near burn scars or flood prone areas.
Otherwise, beneficial rain is anticipated with a 50-70% chance of
at least 0.50 inch of rain for much of the area, a slightly lower
40-50% chance in southwest Montana. Forecast models continue to
show a closed low with widespread rain by late week but much will
depend on the track as to the impact for the Northern Rockies.
Aside from the rain, daytime temperatures will cool to seasonable
levels with valley highs generally in the 70s. Most ensemble
clusters (about 80%) show another trough dropping across the
region late next weekend into the following week (Sep 14-16th),
thus the cool and showery pattern looks to continue.


&&

.AVIATION... This afternoon, increasing instability will
accompany mid-level moisture from the southwest, creating a
favorable environment for thunderstorms. Guidance is indicating
chances for outflow wind gusts of 30 to 40 knots. Thunderstorm
coverage will be throughout the Northern Rockies airspace south of
about Flathead Lake. Based on satellite, dense smoke is being
sweep northward with gradual improvement in air quality across
the Northern Rockies. Smoke may be a bit more stubborn to mix out
of the valleys, but overall less impact is expected at terminal
sites in the coming days.

A few showers will likely linger overnight, particularly in
northwest Montana. Scattered showers and a few thunderstorms are
once again anticipated later Monday, driven by afternoon
instability.



&&

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

$$