Heat Advisory 4, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
404 AM MDT Wed Aug 11 2021

.DISCUSSION...Looking at the water vapor loop early this morning
several features stand out. Besides the two tropical storms south
and west of Mexico, a large upper level trough encompasses all of
the Bering Sea and Aleutian Islands with a frontal boundary
further east that extends north towards Alaska. This large trough
is bringing much warmer air from the subtropics and helping to
strengthen the downstream upper level ridge of high pressure that
is very prominent over the northeast Pacific extending over
British Columbia and the Pacific Northwest. This time yesterday
morning, there was a plethora of mid to high level clouds that
tracked south out of Canada. This morning, the satellite shows
much less cloudiness which will mean more sunshine today besides
the wildfire smoke in the region.

It will be another summer day today as temperatures rise well
into the 80s and 90s across western Montana and 90s to low 100s in
north- central Idaho. Expect breezy west winds between 15 and 25
mph this afternoon, similar to yesterday.

Tonight, a dry and weak cold front, originating from Alberta,
Canada, will traverse west across Glacier National Park and then
stall and weaken by daybreak Thursday. The main impact from this
feature will be gusty easterly winds which will be the strongest
late night into the early morning hours. Wind speeds will range
between 10 and 20 mph in Glacier National Park, Columbia Falls and
also along the western foothills of the Swan and Whitefish Range.
There is a chance that winds could gust over 30 mph in a few of
these places. Night-time low temperatures will stay mild.

From Thursday through Saturday the heat will continue and possibly
top out at 100 degrees for a few locations over western Montana.
Isolated thunderstorms could be possible from the Clearwater
Mountains east and south to Lemhi County over the weekend.

The ridge will start to break down a little bit on Sunday. It will
remain warm, but the flow aloft becomes stronger and more
westerly. This will result in gusty winds across the region.
Depending on how dry we'll be able to get, it could end up being
a critical fire weather day. There is the potential for wind gusts
to exceed 25 or 30 mph in valley locations.

An upper level trough continues to be possible for early next week
and this could bring slightly below normal temperatures and
unsettled weather.

&&

.AVIATION...Gusty west winds between 20 to 25 kts will be common
at KGPI, KMSO, and KBTM, diminishing by 12/0300z. Variable winds
are expected for SMN. Wildfire smoke may cause terrain obscurities
and reduced visibility. A weak backdoor cold front will track west
across Glacier National Park after 12/0300Z and then stall. The
main impact with this feature will be gusty east winds between 20
and 30 knots at ridge-top over the park, Whitefish Range and Swan
Range between 12/0500Z and 12/1100Z. Be careful as there could be
a downslope component within a few miles west of the ridgelines.
The east winds will weaken by daybreak Thursday. Winds on Thursday
are expected to be a little weaker area-wide but have more of a
northerly component in the afternoon and evening.

&&

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