Whitefish Mountain

000
FXUS65 KMSO 311829
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1229 PM MDT Sat Oct 31 2026

.DISCUSSION...

KEY MESSAGES:

-  Valley rain and mountain snow Sunday into Monday morning,
   focused along and south of I-90. Northwest Montana stays mostly
   dry.  

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

-  Potential return to unsettled pattern with chances for mountain
   snow by next weekend (Nov. 7-8).

A broad low pressure system continues to spin along the Pacific
Northwest coast this morning, with southerly flow transporting
atmospheric moisture and cloud cover across the Northern Rockies.
Shower activity has been observed across Lemhi County, ID into 
southwest Montana (along the divide) this morning and that trend 
will continue through the evening. Most locations along and north
of the I-90 will stay dry this evening.

Heading into Sunday, the low pressure system will push south and
east, moving towards the Four Corners region. Forecast guidance
has trended this low further south over the last few days and
forecast precipitation and mountain snow amounts have decreased
since the last forecast cycle. Nonetheless, widespread
precipitation will develop along and south of I-90 Sunday, with
the highest precipitation totals focused along the divide and in Lemhi
County, ID. Valley areas will generally see less than 0.10 
inches, with up to 0.50 inches in the mountains. 

As discussed previously, snow levels will be around 7000 feet
during the day Sunday, but lower to 5000 feet Sunday evening. 
This will bring minor snow accumulations to Lost Trail Pass, 
Georgetown Lake, Homestake Pass, and passes along the Divide in 
Lemhi County (i.e. Lemhi Pass), where lows by Monday morning will 
be near freezing. Impacts will primarily be slushy accumulations 
at these locations.

High pressure builds by Monday morning, but fog and low clouds
could again be impactful, especially areas that received rain the
day before: West-central and southwest Montana, parts of central 
Idaho, and Lemhi County. 

Chances for fog or low clouds continue Tuesday and Wednesday 
mornings, while daytime temperatures climb to slightly above-
average readings. The pattern becomes progressively more unsettled
by the end of the week. Late week mountain snowfall will depend on
how much moisture and dynamical energy can break off from a
longwave trough over the northeast Pacific and move onshore, 
similar to what we have been experiencing lately. 


&&

.AVIATION...Stratus continues to linger across the valleys of the
Northern Rockies. Some improvement will occur where sunshine is
able to diminish the low clouds from the top and showers will 
create some mixing and stratus lifts but other areas will simply 
remain shocked in at least through tonight. Showers will pass 
through Lemhi County and Southwest Montana this afternoon and 
evening with more widespread precipitation by early Sunday 
morning, generally from I-90 southward. 

&&

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

$$