FXUS65 KMSO 010756
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
156 AM MDT Mon Jun 1 2026

.DISCUSSION...

KEY MESSAGES:

- Through Tuesday: A slow moving weather system will bring
  prolonged, light to moderate rainfall, focused along the divide
  and in Glacier Park region.

- River, stream, and creek rises from widespread rain and snow
  melt, leading to the risk of minor flooding across northwest
  Montana.

Satellite and radar observations this morning show a closed low
remaining nearly stationary in central Montana east of the
divide. Widespread rain continues north of I-90 and along and east
of US-93 early this morning. Observations show the heaviest
precipitation totals over the last 72 hours across Flathead and
Lake Counties, where generally 1-2 inches has fallen in valley
areas and 2-4 inches in the mountains. This rainfall, combined
with snowmelt is leading to significant rises on small streams,
creeks, and rivers. An elevated risk exists for minor flooding
from small streams and creaks from the Mission and Swan Mountain
ranges. Flood watches remain in effect for the Flathead River near
Colombia Falls and Clark Fork above Missoula, with these river
systems expected to peak later this evening into early Tuesday
morning.

Widespread rain will spread westward through the morning into the
afternoon, reaching the Montana/Idaho border and I-90 corridor in
west-central Montana. Precipitation rates will increase across
Flathead and Lake Counties during this period, with valley areas
seeing locally moderate rainfall. By the afternoon, widespread
rain will transition into showers across the I-90 corridor and
near the Idaho/Montana border as the low moves slightly north and
east. By tonight into Tuesday morning, high resolution models
suggest the low will wobble northwestward, bringing a return of
widespread rain for all areas along and north of the I-90
corridor. Finally, the low will begin to move eastward Tuesday
night into Wednesday morning as a Pacific trough moves onshore in
the Pacific Northwest, introducing rising heights and building
high pressure as we look ahead to Wednesday across the Northern
Rockies.

Snow levels will be 6,500-7,500 feet through Tuesday, with wet
snow accumulating along the divide in northwest Montana. For those
considering adventuring in the higher terrain, be prepared for
cold and raw backcountry conditions. By the end of this
precipitation event, valley areas along the US-93 corridor north
of Missoula can expect another 0.50-1.00 inches of precipitation,
with the higher terrain along the divide, including the Swan and
Mission Mountains seeing another 1.00-2.50 inches.

A quick warm up brings us back to normal temperatures or slightly
above normal by Wednesday. Late Wednesday into Thursday and again
Saturday into Sunday, could bring more unsettled weather
producing showers and thunderstorms. More to come on the evolution
of these systems; stay tuned!

&&

.AVIATION...A large upper low will wobble around central Montana
into Monday bringing periods of precipitation into the Northern
Rockies. The heaviest precipitation will be north of I-90 and
along and east of US-93, with mountain obscurations remaining
common, and visibility and ceilings down to MVFR at times
(infrequently to IFR) at KGPI and occasionally KMSO. Other
terminal sites and across north-central Idaho will see lower
precipitation chances and lesser aviation impacts. West to
northwest winds of 15-20 kts will return this afternoon.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Flood Watch until noon MDT today for West Glacier Region.

ID...None.
&&

$$