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963
FXUS65 KMSO 201835
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1235 PM MDT Fri Sep 20 2024

.DISCUSSION...
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Satellite imagery early this afternoon is showing a
trough of low pressure moving through western Canada north of
Montana and the Idaho Panhandle. South of the low, a dry cold
front is moving through western Montana. The frontal passage is
leaving increased southwesterly or westerly winds in its wake.
Expect these westerly winds to continue through this evening,
especially on and in the vicinity of Flathead Lake, where boaters
can expect gusts of about 20 mph and choppy conditions. As the
Canadian low moves east, it digs south along the east slope of the
Continental Divide. Northwesterly flow with limited moisture will
create chances for light precipitation over eastern Flathead
County tonight, especially along the Divide in Glacier National
Park. Snow levels behind the cold front will drop to about 6500
feet, so any precipitation that develops will produce a dusting
of snow on the higher peaks in the park.

High pressure will build back for this weekend. Cooler overnight
low temperatures have prompted Frost Advisories for the valleys of
west-central and northwest Montana that have not seen freezing
weather so far this year. Protect sensitive vegetation overnight
tonight and Saturday night. Dry northwesterly flow takes over
again on Saturday. Sunday night, a fast-moving shortwave trough
will bring chances for rain across much of the Northern Rockies.
Model output has weakened this system since previous forecasts,
and ensemble guidance is now only giving about a 20 to 30 percent
chance for measurable precipitation.

Temperatures rebound through midweek, with daytime highs reaching
10 to 15 degrees above normal by Wednesday. The next chance for
precipitation will be later next week through the following
weekend, though model guidance is not at all on the same page
regarding timing and intensity.
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.AVIATION...
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Expect mostly clear skies this afternoon and tonight
for most Northern Rockies airfields. Westerly winds will continue
into this evening with gusts to about 20-25 knots and will relax
by about 21/0100Z. Saturday will feature mostly clear skies with
light and variable winds.
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&&

.MSO WATCHES/WARNINGS/ADVISORIES...
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MT...Frost Advisory from midnight tonight to 9 AM MDT Saturday for
     Flathead/Mission Valleys...Kootenai/Cabinet Region...Lower
     Clark Fork Region...Missoula/Bitterroot Valleys.

     Frost Advisory from midnight Saturday night to 9 AM MDT Sunday
     for Flathead/Mission Valleys...Kootenai/Cabinet Region...
     Lower Clark Fork Region...Missoula/Bitterroot Valleys.

ID...None.
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&&

$$