FXUS65 KMSO 211929
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
129 PM MDT Sun Jun 21 2026

.DISCUSSION...

KEY MESSAGES:

-  Showers and isolated thunderstorms along the Continental Divide
   this afternoon.

-  Warming and drying trend this week, with a 30 to 60 percent
   probability of moderate or higher HeatRisk impacts.

-  Cooler and showery conditions expected this coming weekend,
   June 27-30.

A low-pressure system over Alberta will trigger isolated
thunderstorms and scattered showers along the Continental Divide
today, primarily focusing around Glacier National Park. As this
low-pressure center slowly moves eastward, another round of
afternoon and evening thunderstorms is expected over these same
areas on Monday.

A ridge of high pressure will build over the region Tuesday
through Thursday, bringing a distinct warming and drying trend to
the Northern Rockies. Temperatures will climb well above seasonal
averages by Thursday, reaching the upper 80s to low 90s across
most valley locations. Low-elevation areas near Riggins, Idaho,
are expected to hit triple digits.

There is a 30 to 40 percent probability that moderate HeatRisk
impacts will occur in western Montana, and a 60 to 70 percent
probability for the valleys of north-central Idaho. Moderate
HeatRisk impacts affect anyone sensitive to heat, especially those
without adequate cooling or hydration.

Long-range forecasts indicate a broad trough of low-pressure will
move into the Pacific Northwest by this coming weekend, June
27th-30th. This system will bring significant cooling along with
widespread rainfall. Current ensemble forecast guidance has
afternoon temperatures topping out 10 to 15 degrees below normal
on Saturday.

&&

.AVIATION...A low-pressure system over Alberta will trigger
isolated thunderstorms and scattered showers along the Continental
Divide today, primarily focusing around Glacier National Park.
There is a 30 to 40 percent probability that showers will develop
far enough west to impact the KGPI terminal between 21/2000Z and
22/0200Z, bringing light rainfall, and a 10 to 15 percent
probability of lightning. Otherwise, breezy afternoon winds with
gusts up to 20 knots will develop across all of western Montana
and north-central Idaho.

&&

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

$$