561
FXUS65 KMSO 071955
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
155 PM MDT Mon Sep 7 2026

.DISCUSSION...

KEY MESSAGES:

-  Significant rain event will continue for northwest Montana
   throughout the day on Tuesday.

-  Gradual drying trend develops mid-week alongside morning valley
   fog and chilly mornings. Chance of frost for high valleys of
   southwest Montana Tuesday and Wednesday mornings.

-  30 to 40 percent chance for another wet and even colder system
   next weekend with high elevation snow along the Continental
   Divide


The low pressure system that has brought widespread precipitation
to north central Idaho and western Montana has shifted into north
central Montana this afternoon. With this progression of the low,
the steady moderate to heavy rainfall has shifted northwards and
is now generally occurring across northwest Montana (north of
Highway 200). Localized one hour precipitation rates of 0.3 to 0.4
inches have been observed and will continue to be possible into
this evening. Flood watches remain in effect for portions of
northwest Montana as an additional 1 to 2 inches is anticipated
through mid day Tuesday. Minor flooding in poor drainage areas,
ponding water on roadways and rock/debris on roadways is a
concern, along with rapidly rising small streams and creeks.

South of Highway 200, precipitation will be more showery in nature
through this evening before decreasing after sunset. Showers will
be capable of brief heavy rain, but this activity is not
anticipated to be widespread.

Locations across southwest Montana may see enough clearing tonight
to allow temperatures to drop into the mid 30s, possibly allowing
for some frost development. Elsewhere, cloud cover should limit
overnight cooling.

A drying trend comes into play late Tuesday into Wednesday.
Seasonable temperatures in the mid 70s for many valley locations
are anticipated. Chilly mornings and even some fog will feel very
fall like to end the week.

Beginning on Thursday, winds will increase from the west as zonal
(westerly) flow develops ahead of the next approaching weather
system. This could cause some increased chop on local lakes as
well as possibly enhancing fire weather concerns across far
southwest Montana, which has largely been missed by the recent
precipitation event.

Forecast models still differ on how the next upper level trough
will evolve over the Northern Rockies by next weekend. A trend to
cooler and showery weather looks likely no matter the scenario.
However, 30 to 40 percent are beginning to show a cold and wet low
pressure system over the region. If this were to occur, another
round of widespread precipitation and even high elevation snow
could be a possibility.

&&

.AVIATION...Rain will continue at KGPI and the Northern Rockies
airspace north of about Interstate 90 tonight. Expect decreased
visibility and lowered ceilings to about MVFR or IFR due to rain,
mist, and possibly some early morning fog across northwest
Montana. Precipitation will also obscure terrain over all
mountain ranges of northwest and west-central Montana. South of
about I-90, the biggest impact to aviation will be increased west
or southwesterly winds to about 15-20 knots. Patchy fog may form
at terminals that received rain today and tonight.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Flood Watch through Tuesday morning for Flathead/Mission
     Valleys...Potomac/Seeley Lake Region...West Glacier Region.

ID...None.
&&

$$