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505
FXUS65 KMSO 191907
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
107 PM MDT Thu Sep 19 2024

.DISCUSSION...
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The region remains under the influence of a broad
trough, but most of the energy in the trough is associated with a
closed low in the base of the trough over southern California and
the US Southwest. That leaves the northern Rockies in a split flow
pattern, with a cool air mass and little moisture to work with.

Within that pattern, a shortwave trough will move through and
along the Canadian border this evening and overnight. It will
mainly cause increased cloud cover and some showers, mainly in the
mountains, over northwest Montana.

For the weekend, zonal flow sets up. These means there isn`t
really a trough or a ridge over the region. That will help keep
things cool and breezy with partly cloudy skies in the afternoon.

By Monday, another trough arrives. Ensembles are fairly split on
this one. As the trough digs over the northern Rockies, a ridge
will be building upstream over the Canadian Pacific coast. How far
west that ridge and trough pattern forms will determine how much
moisture makes it into the northern Rockies and how much gets
pushed farther east onto the plains. Right now, around 60% of
ensembles are pushing most of the moisture farther east.

From next Tuesday onward, ensembles agree well on a ridge building
over the region with most of next week being above average
temperatures with mostly clear skies.
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&&

.AVIATION...
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Expect VFR conditions today with a dry northwest flow
pattern over the region. A shortwave will pass by northwest
Montana and the Canadian border this evening and overnight.
However, it won`t have much moisture to work with, so the main
impacts will be increased cloud cover and isolated showers,
especially over the mountains.
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&&

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

$$