Riggins, Idaho Weather Forecast Discussion

463
FXUS65 KMSO 010942
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
342 AM MDT Wed Oct 1 2025
.DISCUSSION...
KEY MESSAGES:
- Breezy with periods of showers today.
- Cooler, showery pattern continues through the week.
- Mountain snow potential increasing Sunday into early next week
A broad upper-level trough off the Pacific Northwest coast will
maintain a cool, unstable southwest flow across western Montana
and north central Idaho. Embedded shortwaves rotating through the
trough will trigger intermittent showers and isolated
thunderstorms, particularly during daytime heating. An approaching
jet streak will increase winds aloft this afternoon and evening,
resulting in breezy surface conditions. Widespread gusts up to 20
mph are expected, with localized gusts to 30 mph possible along
the Continental Divide and across southwest Montana and Lemhi
County.
The upper level pattern evolves this weekend as the broad trough
closes off into a cutoff low over the western U.S. While
ensembles initially favored a more southerly track, a recent
northward trend in guidance increases the potential for more
persistent precipitation across southwest Montana and Lemhi County
by Saturday. Initially, snow levels will remain high, generally
above 7000 feet.
Confidence is increasing in a secondary, colder trough digging
south from Canada Sunday into Monday. This feature is expected to
advect a colder airmass into the region, lowering snow levels to
near 5000 feet by Sunday morning. Probabilistic guidance indicates
a ~70% chance of at least 1 inch of snow and a ~20% chance of 6
inches or more for the higher terrain of Glacier National Park and
along the Continental Divide. Backcountry travelers should be
prepared for cold, windy conditions and accumulating mountain snow
from Sunday into early next week.
&&
.AVIATION...Localized valley fog has produced some brief IFR
conditions at terminals like KGPI this morning, but should
dissipate as the next round of showers moves into the area
through 01/1600z. With diurnal heating, a cool and unstable
southwest flow will trigger scattered showers and isolated
thunderstorms this afternoon. These will bring periods of
lowered ceilings and visibility into the MVFR range. Mountains
are likely to become obscured at times.
Surface winds will increase significantly this afternoon and
evening as a jet streak moves overhead. Expect widespread gusts
of 15 knots, with localized gusts up to 25 knots near the
Continental Divide. Winds will diminish with sunset.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$

NWS MSO Office Area Forecast Discussion