703
FXUS65 KMSO 160655
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1255 AM MDT Wed Sep 16 2026

.DISCUSSION...

KEY MESSAGES:

-  Warm and dry today with sunny skies by this afternoon; breezy
   easterly winds developing into tonight.

-  Shower and thunderstorms Thursday into Friday, generally south
   of Highway 12. Storms will be capable of brief heavy rain and
   small hail.

-  Another warming and drying trend Sunday through early next
   week.

Short lived high pressure over the region today will feature
pleasant, sunny, and near-seasonable weather, with high
temperatures reaching the 70s in western Montana and the 80s in
Idaho. A pressure gradient will generate northeast winds of 10 to
20 mph during the day. Tonight, this gradient will tighten,
increasing the potential for easterly wind gusts exceeding 20 to
25 mph, particularly in channeled terrain along and west of the
Continental Divide.

A low-pressure system will approach southwest Idaho on Thursday,
drawing a surge of abundant monsoon moisture into the area.
Combined with strong wind shear, this system will trigger
thunderstorms capable of producing heavy rain, lightning, gusty
winds, and small hail. On Friday, potential afternoon heating
could increase atmospheric instability, elevating the threat for
stronger storms capable of producing larger hail. The highest
probabilities for these thunderstorms will focus across central
Idaho and west-central to southwest Montana, while northwest
Montana will experience much lower chances for precipitation.

As the low-pressure system exits the region on Saturday, the focus
for showers and thunderstorms will shift east of the US-93
corridor into central Montana, leaving the lower valleys of Idaho
mostly dry with moderating temperatures. High pressure will then
build across the region from Sunday into early next week. Expect
patchy morning fog in river valleys followed by afternoon highs
potentially reaching the 80s in Missoula and the lower valleys of
Idaho. By mid-week, there is a 40 percent chance that a passing
frontal system could bring breezy conditions and temper the early-
week warmth.

&&

.AVIATION...VFR conditions will prevail across the western Montana
and north-central Idaho airspace today under transient high
pressure. A tightening pressure gradient will lead to sustained
north to northeast surface winds of 10 to 15 kts by this
afternoon. Tonight, this gradient will increase further bringing
stronger easterly winds, reaching 15 to 20 knots through channeled
terrain along and west of the Continental Divide, which will
likely result in localized mechanical turbulence for general
aviation. Aviation hazards will increase on Thursday as an
approaching low-pressure system draws in abundant monsoon
moisture. This setup, combined with strong wind shear, will
trigger widespread thunderstorm activity capable of producing
localized MVFR to IFR conditions in heavy rain, erratic gusty
winds, small hail, and mountain obscuration. Thunderstorms will be
most likely along and south of Highway 12, potentially impacting
KMSO, KHRF, KBTM and KSMN.

&&

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

$$