Area Forecast Discussion
Issued by NWS Missoula, MT
FXUS65 KMSO 092139
Area Forecast Discussion
National Weather Service Missoula MT
239 PM MST TUE FEB 9 2016
.DISCUSSION...A ridge of high pressure continues to be the
dominant feature over the Northern Rockies for the next several
days. Tonight, high level clouds appear to move over the region
which will keep temperatures from dropping as much as last night.
This more mild night should hinder fog development, especially in
the Missoula and Butte locations. Air quality continues to
diminish as valley inversions remain in place. Daytime
temperatures will run above normal for this time of year,
particularly in the higher terrain and high elevation valleys.
The ridge breaks down at the end of the week causing a cooler and
wetter weekend. A cold front Friday night will lower snow levels
and cause some impacts to travel. Area passes will certainly be
impacted by snow, and it is possible that snow will briefly impact
the valleys as well.
However, early next week a warm front will cause snow levels to
rise quickly, with an atmospheric river coming into the Northern
Rockies. Even though there will be plenty of moisture in the
atmosphere, most of the good dynamic energy will go north into
Canada, keeping the heaviest precipitation north of the region.
Most precipitation south of the Canadian border will fall in
northwest Montana and central Idaho. Over a 48-hour period
starting on Sunday, it`s likely that over an inch of precipitation
could fall in the Clearwater and Bitterroot mountains of central
Idaho and also in Glacier National Park and the Bob Marshall
Wilderness in Montana.
Lemhi county in Idaho and west central Montana locations such as
Butte and Anaconda will see less precipitation as most of the
energy and moisture moves to the northeast. However, ample cloud
cover and some increased winds with the fronts will help these
areas warm up.
.AVIATION...Valley inversions will remain across the region for
the next several days. Hazy conditions are anticipated at KSMN and
KMSO. Higher level clouds tonight should keep fog from becoming as
widespread, but patchy freezing fog and low stratus is expected
near rivers and open bodies of water. Any fog that does develop
should diminish by late Wednesday morning.
.AIR STAGNATION...Increasing cloud cover and a series of fronts
this weekend will give most of the region a good chance of
ventilating this coming weekend. Until then, conditions will
remain very stable with the stage set for worsening air quality
through the rest of the week. Lemhi county in Idaho will likely
ventilate this weekend with the fronts, however, this area will
likely return to stable conditions around Tuesday of next week.