595
FXUS65 KMSO 131911
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
111 PM MDT Sat Jul 13 2024

.DISCUSSION...A broad ridge of high pressure will remain centered
over the Four Corners area of the western US, resulting in hot and
dry conditions continuing for the Northern Rockies. The
combination of hot daytime highs and warm nights will keep the
lower Salmon and Snake River valleys, including Riggins, under a
Heat Advisory.

This afternoon, a branch of the upper level jet in British
Columbia will slightly flatten the apex of the ridge of high
pressure, resulting in a predominately westerly flow over the
Northern Northern Rockies. An increasingly unstable atmosphere
along with the strong upper level winds, will allow for gusty
winds to mix down to the surface, producing gusts between 20-30
mph between 3PM-8PM. These winds will be mostly realized across
areas along and south of I-90. With the hot and dry conditions in
place, along with the increase in winds, critical fire weather
conditions will be present across southwest Montana and Lemhi
County through this evening.

The center of the ridge of high pressure will drift ever-so slightly
to the east tomorrow, which will introduce more of a southwesterly
flow pattern over the region locally. This will open the door for
modest amounts of SW Monsoonal moisture to enter the region, allowing
for scattered thunderstorm development over Lemhi County and
southwest Montana in the afternoon and evening. Given the dry
antecedent conditions, some of these storms will be dry in these
locations.

Daytime and overnight temperatures will remain above normal for
the entire region early next week, with highs in the low to mid 90s
in western Montana and upper 90s and low 100s in north-central
Idaho. The ridge of high pressure is expected to amplify once
again by mid-week into next weekend, that will increase the
probabilities (60-70%) for max temperatures to once reach or
exceed 100 degrees in the Missoula/Bitterroot Valleys as well as
the Lower Clark Fork and Kootenai regions.

&&

.AVIATION...VFR conditions are anticipated for the next 24 hours
at all terminals. Wildland fires in northern Oregon may cause
smoke to drift over KSMN and KBTM at times causing a reduction in
visibility. Breezy west- northwest winds will develop this
afternoon for KMSO, KBTM, KHRF and KBTM, where gusts are expected
to be between 25-30kts from 13/2200Z-14/0200Z this evening.
Scattered thunderstorms will be possible for KSMN and KBTM Sunday
afternoon and evening.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Red Flag Warning until 9 PM MDT this evening for Deerlodge/West
     Beaverhead...East Beaverhead.

ID...     Heat Advisory until 10 PM PDT Sunday for Lower Hells
     Canyon/Salmon River Region.

&&

$$