599
FXUS65 KMSO 170721
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
121 AM MDT Thu Jul 17 2025

.DISCUSSION...


KEY MESSAGES:

- Breezy, warm and dry days are expected through the weekend.

- There`s a 75 percent probability that a cool, wet and breezy
  weather system could impact northwest Montana on Monday.


A west to southwest flow pattern will promote warm, dry and breezy
conditions today and through the weekend. The windier locations
will be along and south of I-90 in western Montana, including
Lemhi County. Southwest Montana and Lemhi County will have a 60 to
70 percent probability for gusts in excess of 25 mph through this
evening. Also this evening, a weak shortwave will bring a few
thunderstorms to Glacier National Park in the afternoon and
evening.

Friday, will be the warmest day this week and the weekend, as
highs will reach the 90s across western Montana, and lower 100s in
the lower valleys of north-central Idaho. A wave may initiate a
few thunderstorms across southwest Montana in the afternoon.
Strong wind gusts, heavy rainfall, small hail and lightning would
be the main threats, generally affecting Silver Bow County
southwards.

A weak cool and dry front will move through Friday night across
the region. Highs Saturday will be 5 to 8 degrees cooler than
Friday. But it will kick up the westerlies by the
afternoon...generally up to 25 mph in the western Montana valleys,
but closer to 30 mph from Lemhi County to Butte. This could make
lakes in those regions, like Georgetown Lake, kind of choppy and
hazardous for small craft.

By Sunday, an anomalously deep trough will be over the Pacific
Northwest. This will cause temperatures to be a few degrees
cooler, but keep it breezy.

On Monday, ensemble guidance depicts a cutoff low developing over
Washington and Oregon State. This setup is eerily similar to the
storm that we just encountered on Monday and Tuesday. There could
be a cold front passage from Canada, and it could bring wet
conditions across northwest Montana. The latest NBM depicts 50 to
60 percent probability for wetting rains (>0.10) for locations
along and north of the Highway 2 corridor in northwest Montana,
and 20 to 30 percent for the rest of western Montana and north-
central Idaho. Stay Tuned.

&&

.AVIATION... A west to southwest flow will develop over the
Northern Rockies today, promoting warm, mostly dry and breezy
conditions across the region. Westerly winds with gusts between
20-25 kts are expected for KMSO, KHRF, KBTM and KSMN this
afternoon by 17/2100Z. Winds are expected to relax after 18/0300Z
this evening. A weak shortwave along the Canadian/US border will
bring a 15 to 20 percent probability for thunder in the Glacier NP
region from 17/2000Z to 18/0000Z.



&&

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

$$