281
FXUS65 KMSO 132105
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
205 PM MST Mon Jan 13 2025

.DISCUSSION...

KEY MESSAGES:

-  High confidence (70 to 90%) for the coldest air mass of the
   season to descend upon the Northern Rockies next weekend

Water vapor imagery indicates that moisture continues to
circulate around the ridge and into the Northern Rockies. Stratus
cloud cover remains in place, and the influx of additional
moisture supports ongoing chances for flurries or light snow
showers through this evening. However, cloud cover is expected to
decrease overnight south of I-90 as drier air moves in,
accompanied by strengthening surface high pressure. This clearing
will allow for colder temperatures to develop in these areas
overnight.

Westerly flow remains on track to bring mild and breezy
conditions on Thursday as a trough approaches the region.

The primary focus continues to be the Arctic frontal passage
expected on Friday, which could bring snow impacts initially and
much colder temperatures over the weekend. Forecast uncertainty
remains regarding the upper-level flow and the intensity of the
Arctic intrusion, as model clusters suggest three potential
scenarios:

1. A well-defined trough digging west of the region, pulling very
cold air into the Northern Rockies.

2. A northerly flow pattern that brings cold conditions, but not
overly extreme.

3. A northwesterly flow pattern, the mildest of the three, which
would lead to cooler temperatures, only 5-10 F below normal.

Despite these differences, all scenarios support below-average
temperatures, and confidence remains high for a significant
cooldown. Models consistently agree that the coldest temperatures
will occur before Tuesday, January 21, with a gradual warming
trend and increased chances for snow thereafter.

Snowfall predictions vary widely from late Thursday through
Friday, with general expectations ranging from a trace to 3
inches, while a few outlier models suggest locally higher
amounts.

Preparedness Recommendations

1. Slick Roads: Light snow and freezing temperatures may create
icy conditions. Drive cautiously, allow extra travel time, and
maintain safe distances.

2. Cold Temperatures: Prepare for frigid conditions, with
temperatures dropping below zero over the weekend. Protect pipes,
ensure heating systems are functional, and dress warmly.

3. Livestock Protection: Provide shelter and windbreaks for
newborn and vulnerable livestock. Ensure access to feed and water
to minimize cold-related stress.


&&

.AVIATION...Improvement in the cloud cover is expected by tonight
across the region. Satellite imagery in southeastern British
Columbia shows clearing this afternoon. There is an increased
chance for fog development in the valleys through Tuesday morning.
With valley inversions continuing on Tuesday, some locations will
be VFR, while others could have residual stratus that hangs on
throughout the day.

&&

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

$$