140
FXUS65 KMSO 171948
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
148 PM MDT Mon Aug 17 2026

.DISCUSSION...

KEY MESSAGES:

-  Shower and thunderstorm activity will continue each afternoon
   through Tuesday.

-  Warming and drying latter part of next week under a ridge of
   high pressure.

-  Tropical moisture surge late week.

Another round of afternoon thunderstorms is expected today and
Tuesday. In general, the storms today will remain south of I-90
and along the Continental Divide. With similar atmospheric
moisture to previous days, brief but heavy rain can be expected
with gusty outflow winds from any storm.

Early morning Tuesday, a weak wave moves through the ridge of high
pressure and may be a sufficient catalyst for a few showers or
thunderstorms in the Bitteroot or Phillipsburg Valleys, and Butte
region. Then during the afternoon isolated thunderstorms are
again possible along the Continental Divide and south of I-90.

Wednesday will be the driest day this week and produce elevated
fire weather concerns, please exercise caution with outdoor, open
flames. An isolated, dry thunderstorm will also be possible as
instability continues to push into the region from the southwest.

Thursday and Friday will be the warmest days this week, as north-
central Idaho warms close to 110F in Hells Canyon and western MT
warms into the mid and upper 90s. Additionally, remnant moisture
from Tropical Storm Lala, which recently hit Hawaii as a
hurricane, is pulled into the northern Rockies as a Pacific upper
level trough moves into British Colombia Canada. Friday will
result in increased southwesterly breezes with showers and storms
that could produce strong outflow gusts. The wild card is
Saturday, does the moisture overwhelm the atmosphere and result in
cooler and cloudy conditions or is there sufficient afternoon
heating, resulting in area wide showers and thunderstorms. More
to come on this system.

&&

.AVIATION...Scattered showers and thunderstorms will develop this
afternoon across western Montana and north-central Idaho. KHRF,
KBTM and KSMN will have the highest probability for activity, with
the best timing between 17/2000Z - 18/0200Z this evening. Brief
heavy rain, occasional lightning and gusty winds between 20-30kts
will be the main threats. Isolated showers will be possible across
the Bitterroot and Saphirre Ranges through early Tuesday morning.

&&

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

$$