825
FXUS65 KMSO 300837
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
237 AM MDT Tue Sep 30 2025

.DISCUSSION...

KEY MESSAGES:

- Wet and cool today, with cooler and unsettled weather continuing
  through the work week

- Further cooling expected this weekend, with increasing chances
  for mountain snow, especially near the Continental Divide

A low-pressure system off the Pacific Northwest coast will maintain
southwest flow aloft over western Montana and north-central
Idaho. An embedded shortwave trough will increase showers and
isolated thunderstorms through this morning. Based on upstream
precipitation of 0.15 to 0.30 inches in central Idaho, a wet
morning is anticipated. This wave exits by midday, but a second
disturbance will enhance shower activity again from mid-afternoon
into the evening. Most locations will receive wetting rains (>
0.10"), with a 60-80% probability of receiving 0.25 inches or more
across the higher terrain of north-central Idaho and western
Montana.

This active and cool pattern continues through the work week as
the low slowly shifts inland. Temperatures will remain near
normal. Showers will persist daily, with the focus shifting toward
northwest Montana and the Idaho Panhandle on Wednesday. If skies
clear sufficiently Thursday and Friday nights, low-lying valleys
will be susceptible to sub-freezing temperatures.

Guidance continues to favor a deeper trough digging south from
Canada this weekend, advecting a colder airmass into the region.
This increases the likelihood of northeast winds across western
Montana and snow levels lowering to around 5000 feet. There is now
a ~60% probability of at least 1 inch of snow for the higher
terrain along the Continental Divide by Monday morning, and a 20%
probability for 6 inches or more. Backcountry users should prepare
for cold and wet conditions.

&&

.AVIATION...Widespread showers and isolated thunderstorms will
create challenging aviation conditions today. Expect periods of
lowered ceilings and visibility, resulting in widespread MVFR
conditions. IFR conditions are likely within heavier showers and
near any thunderstorms. The persistent precipitation focused on
the higher terrain of north-central Idaho and western Montana will
lead to extensive mountain obscuration. These impacts will be
most pronounced through this morning (30/1600z) and will
redevelop from mid- afternoon into the evening (30/2100z to
01/0400z).

&&

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

$$