Helmville Montana Weather Forecast Discussion

842
FXUS65 KMSO 080817
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
217 AM MDT Wed Oct 8 2025
.DISCUSSION...
KEY MESSAGES:
- Fair weather today and Thursday
- A cold, wet system will bring rain and mountain snow Saturday.
- Late Saturday or Sunday, snow levels will drop causing a
  transition to snow.
Upper level flow turns southwesterly today as a ridge of high
pressure departs the region and a trough of low pressure deepens
off the coast. Clear skies will persist today through Friday
morning with a slight increase in winds. Cloud cover will increase
on Friday as the Pacific low starts to move inland. This system
will bring a wet and snowy weekend for the Northern Rockies. Snow
levels will start to fall on Saturday after it starts raining
earlier in the day. By Sunday morning, expect snow levels to drop
below 5,000 ft across the Northern Rockies.
Median snow forecasts for Monday morning include 6-10 inches of
storm total snow in the Mission, Swan, and Whitefish mountains
with around a foot in the higher elevations of Glacier National
Park. Further south in the Bitterroot Mountains, expect 4-8 inches
of new snow including Lookout and Lost Trail passes. The median
forecast for Lolo Pass is 2-4 inches. High end forecasts (90th
percentile) have 18-24 inches in the mountains of northwest
Montana and around 12 inches in the Bitteroot mountains for storm
total snows.
This is the first winter system of the year that has the potential
to impact travel over mountain passes. Lookout, Lost Trail, Lolo,
and Marias passes are expected to be the hardest hit, but Rogers,
and MacDonald passes also have a chance (10-20%) of picking up a
few inches of snow. Current forecasts for Homestake Pass show a
few tenths of an inch to 2 inches of snow. A major concern with
snow on the passes this time of year is melting and refreezing,
causing very icy conditions. Even if the snow is melting on the
roads, once the sun goes down or the temperature drops just enough
the roads can become icy in a matter of minutes. If you`re
traveling this weekend or early next week, be prepared for winter
conditions in the mountains.
While ensembles agree well on the arrival of the trough and colder
air, there is considerable disagreement on how it exits the region
early to mid next week. Once it starts to move out of the region,
it will start interacting more strongly with any tropical systems
in the Atlantic basin, and currently there`s quite a bit of
uncertainty in those long term forecasts, which translates to a
lot of uncertainty for mid next week.
&&
.AVIATION... Skies will remain mostly clear today. Southerly winds
will increase this afternoon, focused on the southern portion of
the Northern Rockies airspace. Expect gusts of 15-20 kts at KHRF
and KSMN starting late morning to early afternoon.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$

NWS MSO Office Area Forecast Discussion