950
FXUS65 KMSO 170830
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
230 AM MDT Tue Jun 17 2025

.DISCUSSION...

KEY MESSAGES:

- Above normal temperatures, with plentiful sunshine today and
  Wednesday.

- Scattered showers and thunderstorms return across Lemhi County
  and southwest Montana Thursday.

- Growing confidence for widespread precipitation, with cooler
  temperatures and high elevation snow this weekend (June 21-22).

A weak ridge of high pressure will settle across the western US
through Wednesday, with above normal temperatures expected into
Thursday. A dry zonal flow will promote plentiful sunshine along
with breezy westerly winds today and Wednesday afternoon, with
gusts of 15-25 mph in the valleys and 25-30 mph across the higher
terrain.

Showers and thunderstorms return into the forecast Thursday across
southwest Montana and Lemhi County, as southwesterly flow
transports Pacific moisture and instability into the region.
Elevated convection will favor thunderstorms capable of producing
gusty outflow winds along with small hail. Shower and thunderstorm
coverage will become widespread Friday as a broad Pacific trough
moves inland.

Global ensemble models remain in strong agreement for a large
upper level low to bring much cooler temperatures and increased
chances for widespread precipitation next weekend (June 21-22).
Much will depend on how the trough evolves either as a closed low
or an open wave, as closed lows often result in higher
precipitation amounts and lower snow levels. Guidance has been
trending towards the closed low solution in the last 24hrs, with
probabilities for >0.25 inches of precipitation >80% across
northwest Montana and 50-60% across the rest of the Northern
Rockies. Models suggest the highest precipitation will focus
across Flathead County where probabilities for one inch of
precipitation reach 50%. The middle of the road snow level
forecast suggests accumulating snow down to 6,000 feet Saturday
night into Sunday. Those with plans in backcountry and/or high
elevations of Glacier National Park should begin to prepare for
cold temperatures, accumulating snow, and cold and raw conditions.
Gardeners may need to be aware of frost by Monday morning as
well, mainly along the Divide. Stay tuned!

&&

.AVIATION...VFR conditions are expected under mostly sunny skies
and high pressure. Deep mixing will allow for breezy westerly
winds this afternoon, with gusts of 15-20kts after 17/1900Z.

&&

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

$$