417
FXUS65 KMSO 200807
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
207 AM MDT Sat Jul 20 2024

.DISCUSSION...A few showers and thunderstorms have occurred early
this morning along the Divide from Lost Trail Pass toward Butte.
This activity is expected to diminish toward sunrise as forcing
wanes.

Otherwise, hot temperatures rising into the 100 to 115 degree
range are still on track this weekend through the middle of next
week. The ridge of high pressure just does not want to budge,
which will allow for multiple days of persistent heat and little
in the way of overnight relief. In fact, low temperatures in
central Idaho may not even drop below 70 degrees, while most of
western Montana valleys should remain in the 60s each night
through Tuesday. Daily record high temperatures will certainly be
in jeopardy for many locations. As the ridge shifts to the east
by Tuesday and locations along the Continental Divide start to
climb into the mid to upper 90s, such as Butte, Anaconda, Seeley
Lake, etc, records could be tied or broken in these locations as
well. As such, additional Heat Warning and/or Advisories may be
issued or expanded in the coming days. There remains some
uncertainty on how dense smoke may become. In fact, some smoke modeling
brings thick smoke to the Northern Rockies by late Sunday into
Monday, originating from northern Alberta. If this occurs, then
daytime temperatures would be slightly cooler than currently
forecast.

Heat safety for both humans and animals will be crucial through
the middle of next week and should not be taken lightly. The
presence of smoke in the air will degrade air quality, adding to
the stress on the body. Those sensitive to both heat and poor air
quality should take special care to ensure their well-being.

It will also continue to be quite dry with the only threat of an
isolated shower or thunderstorm this weekend along the Divide.
There will be a couple opportunities for remnant monsoonal
moisture to be pulled across the Northern Rockies next week as an
upper trough gradually approaches the British Columbia coast.
This moisture would lead to an increase in thunderstorm chances
with Monday and Wednesday as the two days that stand out currently
but confidence is low on the timing. Also, westerly winds will
begin to increase by the middle of next week as well.

Relief is expected as the high-pressure ridge is replaced by a
low- pressure center (supported by 80% of ensemble clusters) moving
inland from the Washington coast by Friday (July 26).
Temperatures will start to cool a few degrees each day beginning
as early as Wednesday (July 24), but any major improvement will
depend on the timing and track of the low- pressure system.



&&

.AVIATION...
Hot and dry conditions will persist through the weekend, with
light winds except for typical afternoon gusts of 10-20 knots. The
only hint of an isolated shower or thunderstorm will be along the
Divide. High- density altitude will remain a concern due to the
abnormally hot temperatures. Smoke from regional and local
wildfires will create hazy skies and localized visibility
reductions.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Excessive Heat Warning until midnight MDT Tuesday night for
     Kootenai/Cabinet Region...Lower Clark Fork Region.

     Heat Advisory until midnight MDT Tuesday night for
     Flathead/Mission Valleys...Missoula/Bitterroot Valleys...
     Potomac/Seeley Lake Region...West Glacier Region.

ID...Excessive Heat Warning until 11 PM PDT Tuesday for Lower Hells
     Canyon/Salmon River Region...Northern Clearwater
     Mountains...Orofino/Grangeville Region...Southern
     Clearwater Mountains.

&&

$$