576
FXUS65 KMSO 242104
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
204 PM MST Sun Nov 24 2024

.DISCUSSION...


KEY MESSAGES:

-  Another round of snow in northwest Montana, especially north of
   Highway 2 tonight through Monday morning.

- Widespread light snow Tuesday through Wednesday morning.

After a brief break in precipitation today, another round of
light snow is forecast to reach northwest Montana tonight as a
weak disturbance ejects from the low-pressure system off the west
coast. Snow accumulations are expected along and north of Highway
2 through Monday morning, potentially causing winter driving
conditions. This light snow is projected to persist into Monday
morning.

South of I-90, clearing skies may lead to fog development in the
valleys of north-central Idaho and west-central Montana through
Monday morning.

The trough and associated low-pressure center are forecast to
move eastward on Monday, bringing a shortwave trough across the
Northern Rockies Tuesday and Tuesday night. Ahead of the system,
high-resolution models indicate increasing showers in north-
central Idaho on Monday, spreading to the broader region by Monday
night. Moisture levels are expected to reach near-normal levels,
with snowfall projections from the NBM ranging from 1 to 4 inches
along the Idaho-Montana border and near Marias Pass, while most
valleys are likely to receive only a trace to 1 inch of snow by
Tuesday evening.

This trough is expected to continue to move through the region
Tuesday night into Wednesday, producing additional showers.
However, limited moisture will likely result in modest snow
amounts, generally 1-2 inches in the mountains and less than 1
inch in the valleys of central Idaho and western Montana.

By mid-week, a broad, strong trough will develop over the U.S.
West Coast, setting up northwest flow into the Northern Rockies.
Although models do not indicate significant moisture due to the
downstream ridge, this pattern often results in over performing
snow showers. While these showers typically have low water
content, their low snow densities can lead to a few inches of
accumulation. Localized snow bands may form under this pattern,
with persistent bands potentially producing several inches of snow
in specific areas.

Ensemble models agree that by next weekend, the large ridge will
gradually drift eastward. As this occurs, air stagnation could
become a concern, though this is still over a week away.


&&

.AVIATION...Afternoon satellite imagery shows clearing skies
south of I-90, with lingering cloud cover and showers persisting
in northwest Montana. A weak high-pressure ridge, responsible for
the decreasing cloud cover, is expected to move over the Northern
Rockies tonight. This may lead to fog development in the valleys
of north-central Idaho and west-central Montana. Model output
statistics indicate a high likelihood of dense fog forming at KMSO
by sunrise.

Farther north, in northwest Montana, moisture is forecast to pass
through the ridge, bringing another round of snow. This will
likely result in lowered ceilings and reduced visibility,
particularly north of Highway 2 and in areas near KGPI.

&&

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

$$