666
FXUS65 KMSO 091958
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
158 PM MDT Tue Jul 9 2024

...This Afternoon and Wednesday Afternoon Will Be The Two Hottest
Days This Week...

.DISCUSSION...A strong ridge of high pressure will continue to
strengthen over the Northern Rockies, peaking in strength
tomorrow (Wednesday). As such, dangerously hot conditions,
especially in north-central Idaho will continue. While
temperatures will remain hot and well above normal Thursday onward
this week, the Excessive Heat Warnings and Heat Advisories have
been trimmed back to highlight primarily the most extreme days,
and now expire Wednesday evening. Many western Montana valleys,
such as Libby, Thompson Falls, Missoula, and Stevensville, just to
name a few, have around a 60-70% probability of reaching the
century mark this afternoon, and up to 70-80% for Wednesday.
Locations where Excessive Heat Warnings are currently in effect in
north- central Idaho, will see temperatures ranging from 100-110F

A subtle disturbance will pass through the region on Thursday
causing the ridge to flatten. This feature will cause temperatures
to cool slightly, around 5 degrees, but afternoon readings will
still be extremely warm for this time of year. The disturbance
will also cause increased westerly winds Thursday afternoon and
evening. The combination of winds and low humidity readings will
be approaching critical fire weather conditions, especially across
southwest Montana. There is also an outside chance (10-15% chance),
that isolated dry thunderstorms will develop Thursday afternoon
and evening across southwest Montana.

The ridge axis nudges to the east Friday into the weekend. This
shift in the ridge will place the Northern Rockies in subtle
southwesterly flow aloft. This flow appears to allow some
monsoonal moisture to make its way up into the region by Saturday
afternoon causing isolated high-based storms over southwest
Montana and Lemhi County.

&&

.AVIATION...VFR conditions are expected the next 24-36 hours.
Well above normal temperatures will continue for all aviation
sites this week. There is around a 70% Probability temperatures
will reach or exceed 100F at KMSO this afternoon as well as for
Wednesday. The probabilities are much lower, around 20%, at KGPI.
Smoke from regional wildfires in Oregon and Washington will
further create hazy conditions across the region, especially
tonight into Wednesday.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Heat Advisory until 11 PM MDT Wednesday for Flathead/Mission
     Valleys...Kootenai/Cabinet Region...Lower Clark Fork
     Region...Missoula/Bitterroot Valleys.

ID...Heat Advisory until 10 PM PDT Wednesday for Northern Clearwater
     Mountains.

     Excessive Heat Warning until 10 PM PDT Wednesday for Lower Hells
     Canyon/Salmon River Region...Orofino/Grangeville Region...
     Southern Clearwater Mountains.

&&

$$