Polson, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

441
FXUS65 KMSO 192005
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
205 PM MDT Wed Aug 19 2026

.DISCUSSION...

KEY MESSAGES:

- A ridge of high pressure will cause hot temperatures through
  the remainder of the work week. Elevated heat risk for lower
  valleys of north central Idaho

- Thunderstorm chances increase Friday evening through Saturday,
  potentially linger into Sunday.

High pressure will strengthen across western Montana and north
central Idaho through Friday. This pattern will allow for a
noticeable warming trend, with temperatures peaking Friday
afternoon in the 90s for western Montana valleys and low 100s for
lower valleys of north central Idaho. Elevated heat risk will be a
concern for the lower valleys of north central Idaho where
overnight relief will be minimal due to low temperatures only
dropping into the low 70s. With more stable conditions under the
ridge of high pressure, we do anticipate air quality will degrade
somewhat due to ongoing local and regional wildfire smoke.

Forecast models continue to show the potential for some monsoon
moisture to make it into Lemhi County and southwest Montana by
Friday afternoon and evening. This will reintroduce the chance of
showers and thunderstorms with the main threat being gusty outflow
winds. By late Friday night into Saturday morning, this moisture
may spread as far north as northwest Montana. This could favor
some isolated to scattered nocturnal lightning, which may bring a
risk of additional fire starts.

On Saturday, forecast models continue to bring a trough of low
pressure onshore in the Pacific Northwest. The dynamics with this
wave will phase with the increased moisture across the region to
produce widespread showers and thunderstorms. Lightning and breezy
winds will continue to be threats, with storms likely moistening
with time.

A cold front will likely move through the region sometime Saturday
evening into Sunday morning (there are still some timing
differences), creating breezy and much drier conditions. The
threat of thunderstorms will end for most areas, other than across
southwest Montana. Temperatures will drop several degrees, closer
to normal for this time of year.

The latest long term models are indicating another ridge of high
pressure building over the region for the first half of next week.

&&

.AVIATION...A ridge of high pressure will be building over the
region causing mainly fair flying conditions. The biggest impact
to area terminals will be smoke from local and regional fires
causing a reduction in visibility over the next 24 hours.

&&

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

$$