Polson, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

870
FXUS65 KMSO 251924
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
124 PM MDT Mon May 25 2026

.DISCUSSION...

KEY MESSAGES:

 - Potentially strong thunderstorms each afternoon/evening today
   through Wednesday

 - Primary threats from thunderstorms will be strong, gusty
   winds. For tonight, there will be about a 10-15% chance of
   thunderstorm gusts exceeding 50 mph

 - A cool and wet pattern arrives Tuesday, lowering temperatures
   and bringing widespread rain through Friday.

Satellite imagery this afternoon is depicting an elongated low
pressure circulation approaching the coast of the Pacific
Northwest. This feature will be a key player in the weather over
the next several days. In the near term, flow aloft ahead of this
circulation over the Northern Rockies will be southwesterly this
afternoon, turning southerly tonight as the low moves south and
east. South and southwesterly flow are effective in transporting
warmer air and Pacific moisture, key ingredients for convective
storms, into the Northern Rockies. Clear skies ahead of the warm,
moist air will aid in low-level heating necessary to kick off
convection later in the day. Model soundings indicate good
instability and a dry lower atmosphere, indicating a primary
threat of strong outflow winds.

High resolution models indicate showers and thunderstorms
developing over Idaho, Lemhi, and southern Ravalli counties by
about 2 pm MDT. Storms track to the north or northeast, reaching
west-central and southwest Montana (including Hamilton, Missoula,
Butte, and I-90 east of about Missoula) by about 3 pm, and lasting
until about 8 pm before continuing north through Lake, Powell,
and Flathead counties including Flathead Lake. Storms will produce
strong, gusty winds of about 40 mph with about a 10-15% chance of
exceeding 50 mph. Small hail and frequent lightning will
accompany these storms. Tonight, a cold front associated with the
main low pressure circulation will enhance chances for overnight
convection from about 8 pm to midnight MDT. This second round of
storms will be focused further west, including north-central Idaho
and northwest Montana.

The low becomes positioned to the southwest of the Northern
Rockies on Tuesday. Expect another round of afternoon convection,
along with more stratiform rain through Wednesday. Most model
guidance keeps the low over Nevada into later this week before
ejecting northeast this weekend. That scenario will keep a
southwesterly moisture feed available in the Northern Rockies,
and unsettled weather will accompany that moisture feed.


&&

.AVIATION...Radar returns and lightning detection systems are
already showing convection developing over southern Lemhi County
early this afternoon. Moisture and warm air from the southwest
will be conducive to widespread convective storms this afternoon
and tonight. Model soundings indicate ample instability and shear
with a dry lower atmosphere. The resulting storms will pose a
threat of strong, erratic outflow winds, small hail, brief heavy
rain decreasing visibility, and frequent lightning. Expect
thunderstorm gusts of about 40 knots, with about a 10% chance of
exceeding 50 knots. Convective-allowing models indicate storm
development will take place from south to north, starting in Lemhi
and Idaho counties as early as 25/2000Z, moving north to
Hamilton, Missoula, and Butte by about 25/2100Z, Kalispell by
about 25/2200Z. A second round of convection will arrive overnight
as a cold front will enhance instability (26/0200Z to 26/0600Z).
Another round of thunderstorms are in the forecast for Tuesday
afternoon/evening.

&&

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

$$