Butte-Silver Bow, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

953
FXUS65 KMSO 132121
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
221 PM MST Tue Jan 13 2026

.DISCUSSION...

KEY MESSAGES:

- High Pressure to bring prolonged dry pattern next 7-8 days.

- Valley stratus and fog development begins Wednesday into
  Thursday.

- Trend toward a major pattern shift to colder and wetter starting
  Jan 21-22.

A blocking ridge of high pressure will remain the dominant
weather feature across the Western US and Northern Rockies for the next
7-8 days. Satellite imagery shows the ridge centered over
Northern California with the axis along the Pacific Coast. This
setup maintains north-northwest flow aloft over the Northern
Rockies, sending waves of mid-to-upper level clouds across the
region through Wednesday morning. Despite the cloud cover,
temperatures will remain well above normal to near or eclipsing
record values, with afternoon valley highs reaching the 40s and
50s! As of 2 pm MST, Missoula was already 53 degrees which has
broken the previous record of 50 degrees set back in 1983. Butte
is on its way of reaching the previous record of 52 set back in
1996. Kalispell hasn`t been able to get any wind to mix out the
temperature inversion there, and they are about 5 degrees cooler
than they were yesterday at this time. Hamilton is 59 at the
airport which is crazy for this time of year! We saw robins here
at the airport this afternoon, which is unheard of. The
Stevensville Airport is sitting at 64 degrees! Over in north-
central Idaho, temperatures are approaching 50 degrees. The only
place with strong temperature inversions is the Salmon Valley
where highs may only touch the freezing mark. Spring in the
Northern Rockies...oh wait, it`s early January!

Model guidance is in strong agreement that the ridge axis will shift
inland toward the ID/MT border by Wednesday afternoon. As
temperatures warm aloft and clear skies enhance radiational
cooling, valley inversions will significantly strengthen Wednesday
night into Thursday. This will lead to expanding fog and stratus,
particularly near river systems and large bodies of water like
Flathead Lake. Widespread stratus is likely across the Flathead
and Mission valleys, a solution strongly supported by current
guidance. These stagnant conditions will result in degrading air
quality with initial concern for lower elevations of north-central
Idaho thus Air Stagnation Advisories were issued. Additional air
stagnation advisories may be required in the coming days across
western Montana but the pattern is less favorable at least
initially for immediate concerns.

Global ensembles indicate this pattern will persist through early
next week. However, latest long-range guidance now suggests high
likelihood, near 70% chance of the ridge breaking down by mid-next
week (January 21-22). Details still vary on how far west colder
air will reach and the amount of moisture available for
precipitation production. Overall, this pattern is favorable for
colder air spilling over the Divide with both mountain and valley
snow across Northwest Montana. Impacts to areas further west and
south are less certain given the variability mentioned earlier.
Stay tuned as this would be a major shift from the mild and dry
weather through early next week.

&&

.AVIATION...VFR conditions will prevail into tonight as high
pressure remains in control. Mid and high-level clouds will
continue to stream overhead in northerly flow, though clearing
skies by early Wednesday morning will support the development of
valley fog and stratus. While some improvement is expected
Wednesday afternoon, the ridge axis shifting overhead will
strengthen valley inversions. This will likely result in more
expansive and persistent fog and stratus development on Thursday
morning.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...ID...Air Stagnation Advisory until 10 AM PST Friday for Northern
     Clearwater Mountains...Orofino/Grangeville Region...
     Southern Clearwater Mountains.

&&

$$