315
FXUS65 KMSO 041841
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1241 PM MDT Mon Aug 4 2025

.DISCUSSION...

KEY MESSAGES:

- KMSX radar (Missoula, MT local weather radar) will remain
 offline due to scheduled maintenance through the rest of this
 week.

- FLOOD WATCH: Thunderstorms with heavy rainfall, strong winds,
 and hail Monday afternoon and evening.

- Drying and warming midweek, before cooler and wetter weather to
  end the week.

Current:

Radar and satellite imagery this afternoon shows our shortwave
trough pushing through northeastern Oregon and into west-central
Idaho. This feature will be the primary lifting mechanism for
showers and thunderstorms through the rest of the day and into the
overnight. Total precipitable water derived from satellite
indicates between 0.7 and 1.0 inches in the region which is
anomalously high for the area during this time of year.

This afternoon through tomorrow morning:

High resolution convective allowing models are indicating an
increase in shower and thunderstorm development during the early
afternoon hours moving in from the west and southwest as the
shortwave feature approaches from North-Central Idaho. Convection
will likely become more widespread as storms cross over the
Bitterroot range into West-Central Montana.

These storms will be capable of producing multiple rounds of
heavy localized rainfall along with hail and scattered strong /
isolated severe wind gusts. The main concern is for steep terrain,
especially in disturbed areas of wildfire burn scars and urban
areas, not being able to handle the intense rainfall rates. As
reported in the last several days, with similar forecast rainfall
rates, multiple roads, hiking trails, and low-lying urban areas
have seen issues with flooding, debris flows, and rock fall. As a
result, Flood Watches have been issued. Make sure you have a way
to stay alert and heed any further advisories or warnings that may
be issued.

As the shortwave trough continues to evolve and track
northeastward through the evening and overnight, there is the
potential for wraparound moisture and instability to develop
somewhere near the continental divide. The concern is that if this
occurs west of the divide, then locations in northwest Montana
such as Lake, Flathead, and even Sanders and eastern portions of
Lincoln counties could see multiple hours of steady moderate-to-
heavy rainfall into Tuesday morning. This would also cause
concerns for localized aforementioned impacts due to excessive
rainfall. No watches have been issued for these areas at this time
and will leave that decision for successive shifts as we track
the development and progression of storms this afternoon and
evening.

Tuesday and into Wednesday:

Drying and warming trends will take over. Wednesday will likely
end up as the warmest day this week, though the range of potential
highs is rather large (likely range: low 80s to low 90s),
anticipate increased sunshine and temperatures that would be near
if not slightly above normal for this time of year.

End of the week:

A cool pacific trough moves in, dropping temperatures 10-15
degrees and increasing chances for rain and afternoon
thunderstorms. Drying and warming conditions slowly work back
into the region heading toward Sunday.


&&

.AVIATION...A shortwave approaching the region in southwest flow
will cause widespread thunderstorms affecting all area terminals
this afternoon/evening. These storms will bring heavy rain, small
hail, gusty winds, and a lot of lightning. Currently, high
resolution models show maximum potential wind gusts around 55 mph,
though the HREF indicates a 25 percent chance or less of getting
wind gusts over 40 mph for any location including terminals. Brief
visibility reductions are also likely with heavier showers and
thunderstorms.

Precipitation shifts northward into the overnight hours focusing
over northwest Montana but showers still linger in other areas.
Tuesday will be a much drier day but afternoon cloud buildups will
be common.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Flood Watch until 9 PM MDT this evening for Bitterroot/Sapphire
     Mountains...Butte/Blackfoot Region...Lower Clark Fork
     Region...Missoula/Bitterroot Valleys...Potomac/Seeley Lake
     Region.

ID...Flood Watch until 5 PM PDT this afternoon for Lower Hells
     Canyon/Salmon River Region...Orofino/Grangeville Region...
     Southern Clearwater Mountains.

&&

$$