Anaconda-Deer, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

836
FXUS65 KMSO 130759
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1259 AM MST Tue Jan 13 2026

.DISCUSSION...

KEY MESSAGES:

- High Pressure to bring prolonged dry pattern next 7-10 days

- Valley stratus and fog development Wednesday into Thursday.

A blocking ridge of high pressure will be the dominant weather
feature for the next 7-10 days across the Western US and Northern
Rockies. Satellite imagery this morning shows the ridge centered
across northern California, with the ridge axis positioned along
the OR/WA coast. This leaves the Northern Rockies under a north-
northwest flow aloft, with waves of mid-upper level cloud cover
moving overhead. This trend will continue through today into
Wednesday morning. Temperatures will run well above normal as
valleys reach into the 40s and low-50s this afternoon.

Model guidance is in strong agreement for the ridge axis to move
inland near the ID/MT border by Wednesday afternoon. Valley
inversions will strengthen, driven by warming temperatures aloft
and clear skies contributing to efficient radiational cooling
Wednesday night into Thursday morning. Areas of fog and stratus
will begin to expand during this period, especially near river
systems and large bodies of water such as Flathead Lake. This
pattern typically leads to widespread stratus clouds across the
Flathead and Mission valleys, with current model guidance
supporting this solution. The stagnant conditions will lead to areas
of degrading air quality. Air stagnation advisories may be issued
in the coming days to address this concern.

Global ensembles suggest this ridge pattern will persist through
the weekend into early next week. The latest long-term model
guidance is now showing a 70% chance of this ridge finally
breaking down by mid next week (January 21-22).

&&

.AVIATION...VFR conditions will continue under a ridge of high
pressure. Satellite imagery early this morning shows the ridge
centered over northern California, with waves of mid-upper level
clouds streaming over the Northern Rockies from the northwest.
This will remain the theme through today into Wednesday morning. A
45-55kt mid-level jet near mountain crest height will cause
mountain wave activity and mechanical turbulence through the
early afternoon, before winds aloft begin to decrease into the
evening and overnight hours.

&&

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

$$