Polson, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

316
FXUS65 KMSO 172012
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
112 PM MST Fri Jan 17 2025

.DISCUSSION...


KEY MESSAGES:

-  Arctic front arriving today across western Montana will bring
   very cold conditions.

- Dangerous wind chills (-30F to -40F) near and along the
  Continental Divide Sunday night into Monday morning.

An Arctic air mass crossed the Continental Divide this morning
and afternoon and will continue to slowly spread south and west
into western Montana through the evening hours. There isn`t much
moisture associated with it, though periods of light snowfall,
with isolated higher rates, can be expected, especially in west-
central and southwest Montana. The main impact will be an increase
in northeast winds and rapidly dropping temperatures after
sunset.

Saturday will be a cold and breezy day for most of the
Northern Rockies, with scattered snow showers lingering across the
region. On Sunday, a reinforcing shot of Arctic air will move
through western Montana and portions of north-central Idaho,
bringing an even colder air mass. This surge of cold air will
result in dangerous wind chills of -30F to -40F along the
Continental Divide, though it will be bitterly cold farther west
as well. This cold surge is strong enough to spill into central
Idaho by early next week, with single-digit lows expected across
most of central Idaho on Monday morning, while temperatures in
Montana will remain below zero.

Extreme Cold Warnings for wind chills have been issued for the
Butte/Blackfoot and Potomac/Seeley Lake regions Sunday through
Monday morning. The West Glacier region, the Flathead/Mission and
Missoula valleys, and Lemhi County will all be under a Cold
Weather Advisory for wind chills ranging from -15F to -30F
during the same period. If you must travel outdoors, use extra
caution. Limit time spent outside and dress in layers, including a
hat, face mask, and gloves. Don`t forget to protect your outdoor
pets and livestock.

The cold Arctic air mass, combined with a light flow aloft and
relatively warm waters on Flathead Lake, will create a very
favorable setup for lake-effect snow on Monday. This weather
pattern typically favors the southern half of the lake, where a
few inches of snow may occur. If you plan to travel around the
lake, particularly along Highway 35, be prepared for quickly
changing conditions.

Temperatures will begin to moderate by midweek as the Arctic air
mass migrates south and east out of the region. While temperatures
will warm, they are expected to remain below normal for this time
of year.

In the longer term, beyond a week out, long-range models suggest
about a 50% chance of another strong Arctic air mass affecting
western Montana. While this probability may not seem high, it is
significant relative to how often such systems appear in
climatology, so we`re monitoring it closely. Bottom line: Be
prepared for an extended period of cold weather with below-
average, if not much below-average, temperatures.

&&

.AVIATION...

A push of Arctic air has worked into western Montana and will
gradually run out of steam into this evening with
northerly/easterly winds diminishing somewhat. Areas of light to
moderate snow showers will be common into Saturday, bringing
occasional reduced visibility, especially along the Divide and
from the I-90 corridor southward. The next push of Arctic air
arrives in Northwest Montana early Saturday (around 10Z-12Z at
KGPI) with northeasterly gusts of 25-35 kts. These easterly winds
will impact the remainder of western Montana Saturday but at
diminish speeds of 15-25 kts, although a bit stronger near canyon
gaps.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 5 PM MST Saturday for
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...
     Flathead/Mission Valleys...Lower Clark Fork Region...
     Missoula/Bitterroot Valleys...Potomac/Seeley Lake Region...
     West Glacier Region.

     Cold Weather Advisory from 5 AM Sunday to 11 AM MST Monday for
     Bitterroot/Sapphire Mountains...Flathead/Mission Valleys...
     Missoula/Bitterroot Valleys...West Glacier Region.

     Extreme Cold Warning from 5 AM Sunday to 11 AM MST Monday for
     Butte/Blackfoot Region...Potomac/Seeley Lake Region.

ID...Winter Weather Advisory until 4 PM PST Saturday for Northern
     Clearwater Mountains...Southern Clearwater Mountains.

     Cold Weather Advisory from 5 AM Sunday to 11 AM MST Monday for
     Eastern Lemhi County...Western Lemhi County.

&&

$$