Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 221855
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1255 PM MDT Fri Mar 22 2024

.DISCUSSION...Showery conditions will persist across western
Montana and north central Idaho this afternoon and tonight.
Relatively warm surface temperatures and the light nature of
expected precipitation should keep accumulating snow at a minimum.
A backdoor Canadian cold front will remain stalled in northwest
Montana along the Continental Divide. This feature could allow for
slightly higher accumulations, mainly along the Highway 2
corridor from Essex eastward to Marias Pass.

On Saturday, a significant shortwave will accompany a passing
Pacific cold front. This will bring a more intense period of
shower activity. Mountain passes area wide will likely see some
snow cover, especially along the cold frontal boundary as it
passes late morning into early afternoon. Valleys may also see
some snow, possibly mixing with graupel due to the convective
nature of precipitation. However, accumulations will be limited
due to warm ground temperatures and the timing of precipitation
during daylight hours.

On Saturday night into Sunday, the Canadian cold front which has
been banked up along the Continental Divide will begin to cross
into western Montana and north central Idaho. A noticeable drop in
temperature is expected along with another round of snowfall.
This timeframe will see snow levels lower to most valleys bottoms
and thus winter travel conditions will likely return for most
areas due to light snowfall accumulations. Valleys of western
Montana have a roughly 60 to 80 percent chance of receiving at
least one inch of snowfall in this timeframe. Mountain passes,
especially along the Continental Divide will see more focused
snowfall, with rates up to one inch per hour possible Saturday
evening into Sunday morning.

Another concern with this Canadian cold front will be for a rapid
freeze up situation on the roadways. This is especially
problematic across southwest Montana, where warm temperatures
during the day Saturday will rapidly drop Saturday evening, along
with falling wet/slushy snowfall. Ensemble guidance still shows
the potential for a closed low to develop (70 percent chance)
across southwest Montana into Sunday morning, which would further
focus snowfall. If you live near the I90 corridor from Homestake
Pass to Garrison Junction, or have plans to travel in this area,
be prepared for potentially very slick conditions.

For north central Idaho, cooler temperatures will be noticeable.
However, snowfall will mainly be limited to the higher terrain
with lower valleys seeing little to no accumulations.

An active weather pattern with seasonable temperatures will remain
over the Northern Rockies early next week. The mountains will
continue to increase their snowpack with light accumulations in
the valleys of western Montana during the overnight hours.


&&

.AVIATION...In northwest Montana, particularly from KGPI and
extending east over the Divide, the northeasterly pressure
gradient persists. This setup continues to usher in light showers
within the cooler airmass in the Glacier Region, resulting in
light snow accumulations. Meanwhile, across central Idaho and
western Montana, seasonal temperatures prevail along with a mix of
sunshine and clouds in the absence of significant weather
disturbances.

As we progress through the evening, radar projections suggest an
uptick in shower activity as a weak disturbance passes through.
Looking ahead, a more substantial shortwave trough is poised to
make its way into the Northern Rockies by Saturday. This system is
anticipated to bring widespread showers to the region.
Simultaneously, colder air will advance westward over the Divide,
leading to a drop in temperatures and a subsequent decrease in
snow levels by Saturday evening.





&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 6 AM MDT Sunday for West Glacier
     Region.

     Winter Weather Advisory from 3 PM Saturday to noon MDT Sunday
     for Butte/Blackfoot Region...Potomac/Seeley Lake Region.

ID...None.
&&

$$


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