843
FXUS65 KMSO 020814
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
214 AM MDT Tue Sep 2 2025

.DISCUSSION...

KEY MESSAGES:

-  Hot and dry conditions through mid-week with elevated HeatRisk

-  Increased easterly winds expected Thursday into Friday

-  Pattern change to showers and thunderstorms begins this weekend

The dominant ridge of high pressure will shift slightly westward
over the next couple of days, amplifying the ongoing heatwave
across the Northern Rockies. This will continue the warming and
drying trend through Thursday. High temperatures combined with
warm overnight lows will elevate the HeatRisk to moderate or
major levels for the lower valleys of north-central Idaho and
northwest Montana (including Riggins, Orofino, Thompson Falls, and
Libby). The current Heat Advisory for Idaho will likely be
extended; however, the extent of local and regional smoke could
limit just how hot temperatures get.

A key feature of this weather pattern will be a shift in our wind
direction. As the ridge centers itself just to our west, a period
of persistent easterly to northeasterly winds become notable from
Thursday into Friday when widespread increased winds are now
expected. This wind pattern has the potential to transport smoke
from fires burning in Alberta and Saskatchewan southwestward into
our region.

Looking ahead to the weekend, forecast models continue to indicate
the ridge will shift eastward, allowing a more southwesterly flow
to develop over the region. This will bring a slight cooling
trend, though temperatures are expected to remain above average
for this time of year. More importantly, this pattern will
reintroduce enough moisture and instability to bring a renewed
chance for showers and thunderstorms.

&&

.AVIATION...High density altitude and widespread haze will be the
primary focuses through Wednesday. Easterly winds in the terrain,
above inversions this morning will switch to west-northwest this
afternoon. MVFR conditions can be expected near local fires,
especially during the morning hours.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Heat Advisory from noon today to midnight MDT Wednesday night
     for Kootenai/Cabinet Region...Lower Clark Fork Region.

ID...Heat Advisory until 9 PM PDT this evening for Lower Hells
     Canyon/Salmon River Region...Orofino/Grangeville Region.

&&

$$