149
FXUS65 KMSO 062100
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
300 PM MDT Mon Oct 6 2025

.DISCUSSION...

KEY MESSAGES:

-  Widespread Freeze/ frost/ valley fog on Tuesday

-  Dry with seasonable temperatures through midweek

-  Medium to High confidence of fall-like temperatures and return
   of active weather to end of work week.

Overview: High Pressure slides over the Northern Rockies through
midweek. This will create clear skies during the afternoon,
driving high temperatures 4 to 8 degrees above normal, clear
skies and a dry air mass allows for ample overnight radiational
cooling with low temperatures just a couple degrees below normal,
and that in turn could produce a few hours of valley fog or low
stratus right around sunrise, especially along rivers and tighter
valleys.

Thursday the next Pacific trough digs south along the west coast.
Models are in consensus that this trough eventually closes off
Friday morning, unfortunately, their solutions diverge Saturday
onward with differences on how fast the low pressure progresses
eastward and whether it becomes a less organized open wave.

What do the models almost entirely agree on? Saturday and through
mid next week, the region remains cooler than normal, especially
for daytime highs. Precipitation returns as early as Friday,
potentially with thunderstorms initially. Finally, snow levels
could lower between 4000 to 5000 feet late Sunday as precipitation
winds down, producing a couple slushy inches on vegetative
surfaces. Our current forecast package has snow levels remaining
4500 feet and higher for this system, please keep checking future
forecasts as this system comes into focus.



&&

.AVIATION... High pressure dominating the region will maintain
VFR conditions with clear skies and light winds through this
evening.

However, abundant low-level moisture remains trapped in the
valleys. As a result, fog and low stratus are expected to
redevelop overnight. Given that temperatures will be well below
freezing, there is a high potential for frost and freezing fog to
form. Where fog and stratus forms, the IFR/MVFR conditions will
be persistent, with little improvement expected until after 17Z on
Tuesday. A return to VFR is anticipated by Tuesday afternoon as
surface heating mixes out the low-level moisture.

&&

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

$$