939
FXUS65 KMSO 251851
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1251 PM MDT Fri Jul 25 2025

.DISCUSSION...

KEY MESSAGES:

-  Thunderstorm chances will gradually increase each day, moving
   from south to north, beginning today and continuing into next
   week. If you`re planning outdoor activities, be prepared to
   seek shelter or find a safe place if you hear thunder.

-  Strong outflow wind threat (50+ mph) with any thunderstorms
   this afternoon through the weekend.

Beginning today and continuing through much of next week, a transition to
southwesterly flow aloft will become established. This pattern
will support the arrival of periodic weak disturbances and
increasing mid-level moisture, leading to a gradual northward
expansion of daily thunderstorm coverage. Thunderstorm coverage
today will be across Lemhi County and southwest Montana (perhaps
even the southern Bitterroot Valley), shifting northward into the
Bitterroot Valley and I-90 corridor east of Missoula by Saturday
afternoon, and even more widespread on Sunday.

Due to elevated cloud bases, convective development will likely
produce gusty outflow winds, particularly this afternoon/evening
and Sunday. In fact, today there remains a 20% probability for
isolated wind gusts exceeding 50 mph from Georgetown Lake through
Deer Lodge, southward to Butte, as well as across Lemhi County.
The majority of the wind gusts are expected to remain in the range
of 30 to 40 mph. Something to watch out for on Saturday afternoon
will be a strong push of southerly outflow winds through the
Bitterroot Valley, well away from any thunderstorms.

The overall risk of flash flooding remains low over recent burn
scars and flood-prone terrain due to sufficient steering flow for
today through Sunday. However, isolated runoff issues cannot be
entirely ruled out.

By the middle of next week, ensemble guidance continues to indicate an
increase in atmospheric moisture associated with anonymously high
Pacific moisture. Simultaneously, a large-scale trough is
forecast to move onshore over the Pacific Northwest, enhancing
wind shear and destabilizing the environment. Precipitable water
values are projected to range from 150-170 percent of
climatological normals, increasing the potential for more
efficient rainfall production. Under these conditions, the threat
for runoff, debris flows, and localized flash flooding over steep
terrain and burn scars will increase. Additional hazards could
include frequent lightning, small hail, and strong wind gusts.

Individuals with outdoor plans today through next week should
stay weather-aware and be prepared to modify activities in
response to increasing thunderstorm potential across western
Montana and north-central Idaho.


&&

.AVIATION...VFR conditions will prevail again today under southwesterly flow
aloft. Expect typical afternoon gusts in the 20-25 kt range due
to daytime mixing.

By mid-afternoon, scattered showers and thunderstorms will develop across
Lemhi County and southwest Montana, including terminals KSMN and KBTM.
Activity is expected to persist through around sunset. Seasonally warm
temperatures and elevated cloud bases will favor strong convective
downdrafts, with isolated outflow wind gusts exceeding 50 mph possible (20%
chance) in association with the more robust storms.

&&

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

$$