Whitefish Mountain

000
FXUS65 KMSO 301826
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1226 PM MDT Fri Oct 30 2026

.DISCUSSION...

KEY MESSAGES:

-  Valley rain and mountain snow Sunday into Monday morning,
   focused along and south of I-90. 

-  High pressure bringing stable conditions and valley fog next
   week. 

GOES Satellite imagery this afternoon highlights a closed low
spinning off the Oregon and Washington coastline, with southerly
flow aloft sending mid-high level clouds over the Northern
Rockies. Regional radar imagery shows shower activity across 
south-central Idaho, with high-resolution guidance suggesting this
activity will shift northward through Lemhi County and west-
central Montana into this evening. Overall, this shower activity 
will bring hit or miss rain amounts of a trace to up to 0.10 
inches.

On Saturday, the aforementioned closed low begins to move
southeastward along the California coast. Shower activity will
shift south of the area, with the majority of locations seeing
mostly cloudy skies and dry conditions for Halloween activities.
The exception will be across southern portions of Idaho and Lemhi
Counties and along the divide in southwest Montana, where
scattered showers will bring light precipitation amounts. 

The closed low will move across the Great Basin on Sunday, with
moisture and lift focusing precipitation along and south of the 
I-90 corridor. The majority of precipitation will fall with snow 
levels ranging from 6,000-7,000 feet during the day on Sunday. As 
the low begins to pivot eastward into the central Rockies Sunday 
night, cold air advection aloft under northwesterly flow will 
bring lower snow levels, with snow falling down near 5,000 feet as
precipitation rates begin to decrease through Monday morning. 
Overall, this doesn't appear to be a significant snow event, with 
minor snow amounts (trace to locally up to 4 inches) above 6,000 
feet across southwest Montana and Lemhi County. This includes 
the US-93 and I-90 corridor over Lost Trail and Homestake Passes. 

Ensemble model guidance is in strong agreement for high pressure
to build across the western US Monday night into midweek. This
stable pattern will lead to morning fog and stratus across many
valley areas. The weather pattern through much of the week will 
be characterized by a split flow regime, with weaker systems 
attempting to break through the ridge of high pressure by 
Thursday into Friday, perhaps bringing periodic showers to the 
area. No significant and/or strong systems are currently on the 
horizon through next weekend. 

&&

.AVIATION...A disturbance is on track to pass through western 
Montana and north-central Idaho this afternoon and evening. This 
will bring scattered showers, lowering ceilings, and terrain 
obscuration across the region. As the disturbance exits tonight 
decreasing mid-level clouds will combine with a stable, saturated
boundary layer. This environment points to a return of a mix of 
fog and low stratus developing overnight impacting sites like 
KGPI, KMSO, and KHRF. 


&&

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

$$