658
FXUS65 KMSO 311823
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1223 PM MDT Sun Aug 31 2025

.DISCUSSION...


KEY MESSAGES:

-  Warming and drying trend into next week, potential heat impacts
   through Wednesday.

A significant warm up is underway as high pressure continues to
build over western Montana and north central Idaho. The warmest
temperatures are anticipated to be Monday through Wednesday, with
valleys reaching into the mid to upper 90s in western Montana and
100 to 107 in the lowest valleys of north central Idaho. This is
roughly 15 degrees above normal for this time of year. Heat risk
will be increasing through the week as hot daytime temperatures
are coupled with warm overnight temperatures. Though heat impacts
are possible for both western Montana and north central Idaho, the
most pronounced effects are anticipated from Orofino south to
Riggins. Heat related products have been issued for the
aforementioned areas in Idaho. They may need to be expanded to
cover portions of northwest Montana by Tuesday and/or Wednesday.
Current forecasts have the lower valleys in Lincoln County
reaching 100 degrees. If this occurs, it will be the first time
since 1998 the Libby area reached 100 degrees in the month of
September.

The one complication may come from additional wildfire smoke, both
from local fires and also regional fires in Oregon. Smoke can have
a large impact on daytime temperatures, especially this time of
year as the solar angle begins to decrease. Areas that see thicker
wildfire smoke may see temperatures as much as 3 to 8 degrees
cooler than the current forecast shows. In addition, easterly
winds will be in place much of this week. Though they are not
expected to be overly strong, it could be a consideration for
going wildfires in the region.

Forecast models continue to show a slight cooling (5 to 8 degrees)
towards the end of the week. There are also hints at increasing
moisture, which could allow for a few showers and thunderstorms.

&&

.AVIATION...Fair flying conditions are expected at the terminals
for the next 24 hrs with generally light, terrain driven winds.
Winds are expected to become more easterly this evening. Smoke
from regional fires will continue to create hazy conditions
throughout the forecast period.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...Heat Advisory from noon Monday to 9 PM PDT Tuesday for Lower
     Hells Canyon/Salmon River Region...Orofino/Grangeville
     Region.

&&

$$