637
FXUS65 KMSO 052140
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
240 PM MST Wed Feb 5 2025

.DISCUSSION...

KEY MESSAGES:

- Snow showers tonight will bring some more snow, mainly to west
  central and northwest Montana.

- Another round of snow is on the way for central Idaho, Lemhi
  County, ID and portions of western Montana.

- Longer term, an active, snowy weather pattern remains over the
  region through at least next week.

Finally some patches of blue sky are starting to show this
afternoon across the region, but it`s filling in pretty quickly.
Some shallow snow showers can be seen on the radar coming off the
Bitterroot mountains and starting to spread to the north. We
expect minimal impacts from these showers as they don`t have much
moisture to work with, though the western portions of Lincoln
county and Sanders counties in Montana could pick up a quick 2-4
inches of new snow by tomorrow morning. We looked at the high
resolution model ensemble and found a 60 percent chance for
moderate to heavy snow showers along Highway 200 northwest of
Thompson Falls to Heron.

Gusty westerly winds between 25 and 40 mph are possible along and
west of the Divide this evening which could bring patchy areas of
blowing and drifting snow. As of the time of this discussion, the
winds were gusting close to 35 mph west of Anaconda, Elk Park
north of Butte was gusting to 30 mph, and MacDonald Pass and
Marias Pass were gusting in the 20s.

The current trough over the region stretches out over the next 24
hours and connects with a low pressure system spinning of the
Washington coast. That connection will help to feed some moisture
in to the region Thursday night and Friday morning. Meanwhile, a
trough dropping in out of the northwest from Canada will interact
with that band of moisture causing moderate to heavy snow in
portions of western Montana and central Idaho.

Current probabilistic forecast systems and ensembles have focused
most of the moisture in southern Idaho county and Lemhi county in
Idaho. Significant moisture will also affect west central and
southwest Montana including Ravalli, Missoula, and Granite
counties from this storm. Some of the more recent deterministic
model runs are showing a northward trend which may require a
change to the forecast tomorrow. In the meantime, the main areas
with the most impact we expect from this incoming storm are the
hills above Highway 95 and Riggins in southern Idaho county. There
is less certainty in the impacts to the lower elevations of Lemhi
county, Idaho, but the higher elevations will probably pick up
another 4-6 inches of snow on Friday. Similar snow amounts are
expected in the southern portions of Ravalli County, MT.

Farther north in Montana, the recent cold front failed to blast
all the cold air out of the valleys, so cold pools remain. Weather
models have a very difficult time resolving these cold pools, and
so sometimes they overdo the amount of down-slope flow that
causes rain shadows in the valleys. That is the case now, and
Missoula could see several inches of new snow come with this short
wave on Friday. Current forecasts for the Missoula area range
from about an inch and a half up to 7 or 8 inches. The most likely
forecast is around 4 inches. We expect this to be pretty light,
fluffy snow.

It`s important to remember there`s still an unusual amount of
variability in the track of the upper level trough and the
moisture plume that are coming in, so while we expect the general
forecast of snow amounts to remain similar, which locations and
how much they get could change pretty quickly with tomorrow`s
forecast. So if snow is a problem (or a benefit!) for you, please
stay tuned to the forecast.

In the long term, the region remains under a broad region of
troughing, so snow showers will be a common occurrence through at
least next week. After that, ensembles start to show more
confidence in a warming trend around or just after mid-month.

&&

.AVIATION...Unstable conditions behind the cold front from last
night and today are allowing some showers to form, especially over
the terrain this afternoon. We expect the showers to dissipate
this evening. Some of the more southern terminals in our area
including KHRF and KSMN will likely see some clear periods tonight
while mid-level ceilings remain over most of western Montana.
Thursday will bring a break from some of the winter weather, but
another trough from the northwest on Friday will interact with
some Pacific moisture coming in from the west, and another round
of snow is expected for Friday.



&&

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

$$