770 
FXUS65 KMSO 232035
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
135 PM MST Wed Dec 23 2020

.DISCUSSION...High pressure ridging slides in tonight lasting
through Friday with fair weather overall. Valley inversions will
become established, thus temperatures will be seasonably cold.
Mostly clear nighttime skies will promote patchy freezing fog
development in the valleys, most likely in Northwest Montana. This
could make for sudden visibility changes and a few slick spots
both mornings.

The next winter weather system arrives Friday night into Saturday
with a round of snow for much of the area. Modest snow amounts
(3-6 inches) are likely on the higher terrain of North-Central
Idaho and Northwest Montana. Valley snow amounts will be light
generally a dusting, although the valleys of Northwest Montana may
pick up an inch or two. Northwest flow on Sunday will support
occasional snow showers. Prepare for periods of slick travel over
the coming weekend, especially on area passes.

The jet stream will push into the Desert Southwest early next
week, taking much of the snow-making energy with it. However, the
Northern Rockies are left under a light northwest flow which
typically results in periodic light snow showers, even when
forecast models aren’t too keen on precipitation. This could
certainly be a changeable part of the forecast in the coming days,
stay tuned.


&&

.AVIATION...Fair weather is anticipated as ridging moves in
tonight. Valley inversions will develop resulting in stable
conditions and light winds. The main aviation hazard will be the
potential of freezing fog overnight into Thursday morning. It
doesn’t appear to be a great setup for widespread fog
development but the lower valleys of Northwest Montana such as
KGPI will likely see periodic visibility reductions in fog
Thursday morning. KMSO may also experience fog, but forecast model
soundings would suggest more of a heavy frost scenario rather than
multiple hours of freezing fog.


&&

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

$$