373
FXUS65 KMSO 161857
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1257 PM MDT Sun Aug 16 2026

.DISCUSSION...

KEY MESSAGES:

-  Shower and thunderstorm activity will continue each afternoon
   through Tuesday.

-  Warming and drying latter part of next week under a ridge of
   high pressure.

Visible on satellite imagery this afternoon is a circulation of
low pressure off the coast of California, along with a smaller,
weaker circulation near the Olympic Peninsula. These low pressure
systems to the west are keeping the Northern Rockies in southwest
flow, resulting in the transport of moist air from the Pacific
into our region. For this afternoon, that means afternoon showers
and thunderstorms will develop as they did yesterday. The
geographic focus for thunderstorm formation will be north-central
Idaho (including Lemhi County), west-central Montana (including
the Bitterroot Valley), and southwest Montana (including Butte).
High resolution models have backed off somewhat for convection
over northwest Montana (including Kalispell and Glacier Park) from
previous runs, but certainly not ruling out a heavy rainer or
two. Region-wide, model soundings indicate some deep instability
with modest shear conducive to heavy rain. The lower atmosphere
looks dry enough to support outflow gusts of 30-40 mph. Frequent
lightning and small hail will round out the list of threats from
this afternoon`s round of convection.

On Monday, the southwesterly moisture feed will continue, bringing
another round of convective showers in the afternoon. The
geographical focus will also remain north-central Idaho, along
with west-central and southwest Montana. Upper level flow
flattens out on Tuesday, becoming more westerly, as the Northern
Rockies sits atop a broad ridge of high pressure over the
southwestern U.S. through midweek. Expect increased shower
activity and westerly winds. That ridge amplifies later in the
week, putting the Northern Rockies under the ridge and into drier
conditions and above-normal temperatures for Thursday and Friday.


&&

.AVIATION...Today will be much like yesterday for aviators in the
Northern Rockies. Satellite imagery is showing mostly clear skies
south of about Interstate 90 early this afternoon. Expect
increasing clouds as the afternoon evolves, along with chances
form thunderstorms at all Northern Rockies terminals. There will
be better chances (about 30%) for thunderstorms at KBTM, KHRF, and
KSMN. Expect a little less chances for KMSO and KGPI. Storms that
do form will be capable of heavy rain reducing visibility down to
about 3 SM, gusty winds of about 30-40 knots, and frequent
lightning. Fog will again be an issue in the morning at any
terminal that experiences rain tonight. KSMN and KHRF have been
experiencing visibility reductions of around 1/4 SM or less, if
these locales see rain tonight, those same conditions will likely
be present on Monday morning.


&&

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

$$