549
FXUS65 KMSO 182034
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
234 PM MDT Fri Jul 18 2025

.DISCUSSION...

KEY MESSAGES:

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

-  A 75 percent probability exists for a cool, wet, and breezy
   weather system early next week.

Today will be the warmest day into the weekend. Temperatures in
western Montana will range from the upper 80s to low 90s, while
north-central Idaho will see highs in the low 100s in the lower
elevations. There will be just enough instability and moisture for
isolated thunderstorms to develop over Lemhi County and southwest
Montana this afternoon and evening. There are some cloud streets
that have formed over the Flathead Valley area, so we have
introduced a slight chance for showers this afternoon. Otherwise,
mostly dry conditions will prevail, with wind gusts around 20 to
25 mph across the Northern Rockies. The weak front that will
traverse across north-central Idaho this evening and tonight will
create elevated fire weather conditions.

Saturday will be slightly coolerpossibly even a few degrees
below normalbut will remain dry and breezy across the region.
Minimum relative humidity values dropping into the upper teens and
low 20s, combined with gusty winds, will create near-critical
fire weather conditions, particularly across southwest Montana and
north-central Idaho. Currently, there is a 50 to 70 percent
probability that gusts will exceed 25 mph across western Montana.
A shortwave trough across the Canadian border may bring just
enough instability and lift for a few isolated showers and
thunderstorms in northwest Montana, north of Highway 2.

On Sunday there will be increasing high clouds, breezy afternoon
conditions, and mild temperatures. The greater chance(50-70%) for
wind gusts exceeding 20 mph is found along the Divide, Southwest
Montana and Lemhi County.

By Monday, a slow-moving cut-off low pressure system will be
situated over central Washington into Oregon. The frontal zone
associated with this feature will be quasi-stationary from
north-central Idaho into western Montana. It could be a good setup
for post-frontal showers that could be light to moderate in
intensity Monday morning. Depending on how much sun we get, will
determine how intense the thunderstorms will be. The University of
WA WRF that goes out to 120 hours depicts scattered storms across
northwest Montana Monday evening, but an isolated supercell
thunderstorm across southwest Montana.

As the upper trough begins to eject to the northeast by Tuesday
morning, the stronger lift associated with it will induce more
widespread showers and thunderstorms, mainly across northwest
Montana. This is the area where the NBM has the highest
probability for precipitation amounts greater than 0.09" (50-75%
chance). There could be northeast winds that develop in this
region, but right now they don`t look to be as strong as what
was experienced this past Monday and Tuesday.

A general warm-up is expected later next week into the following
weekend. With the upper level flow oriented in a southwesterly
direction, this could bring possible thunderstorms back to the
region.

&&

.AVIATION...A west to southwest flow will remain over the
Northern Rockies today, promoting warm, mostly dry, and breezy
conditions across the region. Westerly winds with gusts between
2025 kts are expected at KMSO, KHRF, KBTM, and KSMN this
afternoon by 18/2100Z. Winds are expected to relax after 19/0300Z
this evening. Weak instability will allow for isolated convection
over Lemhi County and southwest Montana this afternoon,
potentially impacting KSMN and KBTM between 18/2100Z and 19/0200Z.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...Red Flag Warning until 10 PM PDT this evening for Palouse/Hells
     Canyon.

&&

$$