254
FXUS65 KMSO 101957
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1257 PM MST Wed Dec 10 2025

.DISCUSSION...

KEY MESSAGES:

- Heavy rain and flooding threats shift further north towards NW
  Montana.

- Record warm overnight lows will aid in snow melt through Friday
  morning.

- Northwest Montana concerns due to high winds and wet soils in
  the mountains tonight.

- Snow returns to northwest Montana, and especially the Seeley-
  Swan Valley Friday night.

The atmospheric river over the region has drifted north over
northwest Montana today giving central Idaho a break from the
moisture. It will remain there through tonight and drift southward
again tomorrow causing more rain in central Idaho through Friday.
The break in precipitation for central Idaho will allow the rivers
and streams to drain some of the recent excess moisture and
recover before the next wave arrives. Further, the next wave is
forecast to be much less intense than previous waves of moisture,
so we`ve cancelled the flood watch for Idaho county. Clearwater
county is getting less of a break, so we`ll let the watch continue
there. However, it will continue to rain, and standing water and
potential rock falls remain a threat for that area.

Northwest Montana will continue to receive moderate to heavy rain
with the next peak in rain rates expected late tonight. Thus far
the landscape has been able to absorb enough of the run-off that
no negative impacts from flooding has been reported. However, as
the soils become more saturated, the warm nights start to melt
more snow, and the rain continues, flooding does remain a concern
there, and the flood watch continues.

Record warm lows in the 40s are forecast for western Montana for
Thursday and Friday morning. On its own, this is of little impact.
However, with the snow pack warming up and starting to melt and
the rains on it, this is a significant contributing factor in
areas with flooding potential.

Atmospheric rivers have two main components, moisture and wind.
This one has a very strong wind component. Stable conditions due
to the rain have been keeping the winds from reaching the valleys,
but the mountains and higher elevation exposed areas are a
different story. Northwest Montana will see exceptional wind
speeds above the valley tonight with wind speeds over 60 mph
within just a few thousand feet of the valley floor. More exposed
areas in the mountains and foothills around the valleys will
intermittently catch some of these strong gusts, with isolated
high elevation mountain locations getting blasted by the wind. The
locations that will consistently see damaging winds are remote, so
we`ve decided against a warning there. We`ve issued advisories for
the rest of the area. Due to the stable conditions winds will
become light at times, and then be followed by periods of a few
minutes to half an hour or so of strong gusts. The winds will be
very erratic. This in combination with very wet soils is cause for
concern about trees coming down and potential power outages,
especially in mid and upper elevation rural areas.

By Friday evening temperatures will start coming down, and any
remaining moisture will fall as snow. High end forecasts (90th
percentile) have 1-2 inches in the valleys of northwest Montana by
Saturday morning. The mountains and the Seeley-Swan Valley will do
much better with 4-6 inches of snow for the high end forecast.

Finally, in the long term some ensembles are starting to turn
colder. Not a lot colder, but cold enough for more snow by
Christmas. Right now this is a minority of models, but it`s the
first sign that the atmosphere is getting ready for a change.
We`ll keep watching, but so far the majority of long term
forecasts remain warmer and wetter than average.



&&

.AVIATION...An atmospheric river continues to impact the region,
with the heaviest precipitation currently focused over northwest
Montana. The primary aviation hazard over the next 24hrs will be
increasing southwesterly winds and degraded visibility from
persistent light to moderate rainfall. The strongest winds this
afternoon and evening (through 11/0200Z) is expected for areas
along and south of I-90, where wind gusts are anticipated to range
between 25-35kts, with isolated higher gusts. Overnight tonight,
northwest Montana will see their strongest gusts of 25-35kts
through 11/1400Z tomorrow morning. KMSO, KHRF and KBTM will see
another round of gusty winds up to 30 kts after 11/1300Z and
lasting through 11/1700Z. Expect turbulent conditions and
mountains obscurations throughout the Northern Rockies for the
next 24 hours.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Flood Watch through Thursday afternoon for Flathead/Mission
     Valleys...Kootenai/Cabinet Region...Lower Clark Fork
     Region...Potomac/Seeley Lake Region...West Glacier Region.

     Wind Advisory until 8 AM MST Thursday for Flathead/Mission
     Valleys...Kootenai/Cabinet Region...Potomac/Seeley Lake
     Region...West Glacier Region.

     Wind Advisory until 7 PM MST this evening for Butte/Blackfoot
     Region...Missoula/Bitterroot Valleys.

ID...Flood Watch through Thursday afternoon for Northern Clearwater
     Mountains...Orofino/Grangeville Region.

&&

$$