102
FXUS65 KMSO 221046
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
346 AM MST Fri Nov 22 2024

.DISCUSSION...

KEY MESSAGES:

-  Valley rain and mountain snow through Friday night.

-  Falling snow levels on Saturday creating winter driving
   conditions.


The atmospheric river continues over the Northern Rockies with the
next pulse of moisture making its way into the region this
morning. North central Idaho into northwest Montana will once
again receive the bulk of the precipitation.

Later tonight into Saturday a piece of energy from the upper
level low off the Pacific Northwest coast is still anticipated to
move from eastern Washington into southern Alberta. This
disturbance will cause another pulse of moisture to stream into
the region, but will also bring in colder air allowing snow levels
to drop. This disturbance could also permit some arctic air to be
pulled eastward over the Continental Divide by Saturday night. The
models continue to disagree on how far east this arctic air will
intrude northwest Montana. The over all lowering of the snow
levels along with the second pulse of moisture should cause
additional winter driving conditions especially to mountain passes
and northwest Montana. The valleys of northwest Montana should
expect a half to 2 inches of snow accumulation by Sunday morning.
While Lookout, Lolo, Lost Trail and Marias passes are anticipated
to receive 5 to 9 inches. Homestake and MacDonald passes could
receive 2 to 5 inches by Sunday morning.

A transitory ridge is still expected for Sunday into Monday
causing a decrease in shower activity. The latest model guidance
has trended slightly farther to the north with the passing of the
low pressure system next week. The path appears to be over
southern Idaho which might bring decent snow to areas south of the
I-90 corridor. After the passage of this low the upper level flow
will become northwesterly which will keep cooler temperatures and
scattered showers over the Northern Rockies.


&&

.AVIATION...All the moisture from this atmospheric river is
causing low ceilings at times foggy conditions. The next pulse of
moisture is expected to move into the region this morning which
will lower the ceilings once again at KGPI, KMSO and KHRF. Once
again KBTM and KSMN will be dealing with scattered showers around
the terminals.

&&

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

$$