309
FXUS65 KMSO 070938
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
238 AM MST Fri Nov 7 2025

.DISCUSSION...

KEY MESSAGES:

- Cold frontal passage this morning; short burst of heavy snow
  and gusty winds over mountain passes.

- High pressure builds this weekend; risk for fog and low clouds
  Sunday and Monday mornings.

Surface observations and regional radar imagery this morning
highlights a quick moving cold front sweeping across eastern
Washington and the Idaho Panhandle. Wind gusts of 30-50 mph have
been widespread as of 2AM MST this morning across eastern
Washington, with temperatures and snow levels falling quickly
behind the front. Given these trends, confidence is medium-high
for a burst of moderate-heavy snow, and gusty winds across area
mountain passes this morning. The front will reach Lost Trail,
MacDonald Pass, the Montana Highway 1 corridor, Butte, and
Homestake Pass between 700-900 AM MST. Local research has shown
these areas are more vulnerable to snow squalls and this threat
will be watched closely.

The front will push east of the divide by early afternoon, with
westerly wind gusts of 20-30 mph in valley areas and 30-45 mph
along the divide and higher terrain. Scattered showers will
continue along the Idaho/Montana border and Clearwater Mountains,
with most areas drying out following the frontal passage.

High pressure builds in Friday night into Saturday morning. Stable
conditions this weekend may lead to low clouds and fog, especially
Sunday into Monday as the ridge strengthens. Areas with persistent
fog will be 5-10 degrees cooler than currently forecast, though
pinpointing specific locations remains difficult.

Ensemble guidance indicates the ridge may begin to flatten next
week, with most guidance suggesting the Monday afternoon into
Tuesday timeframe. As a ridge flattens, a decaying plume of
Pacific moisture may move overhead, leading showers and light
high elevation snow (6000-7000 ft).

&&

.AVIATION...The primary aviation hazard early this morning will
be significant mechanical turbulence as southerly winds have
developed over the higher terrain and Camas Prairie (near
Grangeville, ID) ahead of a strong cold front quickly moving
across eastern Washington and the Idaho Panhandle. Gusts exceeding
30 to 35 kts have been observed, which will generate turbulence,
especially over ridges and through mountain passes. Low-Level Wind
Shear (LLWS) will also be a threat for terminals near terrain,
including KGIC and KBTM, as strong southerly flow remains just
above the surface. Winds will gradually shift and become more
westerly after 07/1200z, with gusts to 25 kts becoming more
widespread area wide through this afternoon.

The cold front will move rapidly northwest to southeast across
western Montana and north central Idaho, introducing widespread
flight hazards this tomorrow morning (10z to 17z). Northwest MT
and North-Central ID (KGPI, KMSO, KGIC) can expect widespread
MVFR conditions to develop as the main precipitation band moves
through. Ceilings and visibilities will drop in snow and
rain/snow mix. For Southwest MT (KBTM, KSMN), the front will
transition to a more convective, showery nature. Vigorous snow
showers will develop from Lolo Pass south and east around sunrise
(12Z-15Z) for elevations above 4,000 feet. These showers will be
capable of producing rapid, short-duration reductions to IFR or
LIFR (visibility one half mile or less) in heavy snow, accompanied
by gusty SW/W winds.

&&

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

$$