481
FXUS65 KMSO 030742
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
142 AM MDT Wed Sep 3 2025

.DISCUSSION...

KEY MESSAGES:

-  Hot and dry conditions continue today with elevated HeatRisk

-  Increased easterly winds expected Thursday into Friday

-  Pattern change to showers and thunderstorms begins this
   weekend

The ongoing heatwave peaks today as a robust ridge of high
pressure centers over the region, continuing the hot and dry
trend. High temperatures and warm overnight lows will keep the
HeatRisk at moderate to major levels in the lower valleys of
north-central Idaho and northwest Montana, including Riggins,
Orofino, Thompson Falls, and Libby. As a result, the Heat Advisory
for north-central Idaho and parts of northwest Montana remains in
effect through this evening.

A change arrives Thursday as the ridge`s position establishes a
period of persistent easterly to northeasterly winds. This shift
will have several notable impacts:

 - Fire Weather: the combination of hot, dry conditions with
   these increasing easterly winds will elevate fire weather
   concerns on Thursday through Thursday night.

 - Recreation: The increase in winds will create choppy
   conditions on Flathead Lake by Thursday afternoon and evening,
   with a 25% chance of gusts reaching 25 mph.

 - Increasing smoke: This wind pattern has the potential to
   transport smoke from wildfires burning in Alberta and
   Saskatchewan southwestward into our region.

The pattern is set to change this weekend as forecast models
consistently show the ridge shifting eastward, allowing a
southwesterly flow to return. This will usher in a slightly
cooler, but more humid, airmass with temperatures returning closer
to seasonal averages. This pattern will also reintroduce enough
instability for a renewed chance of showers and thunderstorms.
With atmospheric moisture climbing to 150-200% of normal, there is
a marginal risk for excessive rainfall, which could create runoff
impacts on recent burn scars and in steep terrain.


&&

.AVIATION...Expect another day of high density altitude impacting
all area airfields, especially during peak afternoon heating.
Widespread haze and smoke, with localized MVFR or below near fires
is expected again today. A significant shift to easterly winds on
Thursday will introduce increasing concerns for mountain wave
turbulence and lowered visibility from Canadian wildfire smoke.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Heat Advisory until midnight MDT tonight for Kootenai/Cabinet
     Region...Lower Clark Fork Region.

ID...Heat Advisory until 11 PM PDT this evening for Lower Hells
     Canyon/Salmon River Region...Orofino/Grangeville Region.

&&

$$