Polson, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

330
FXUS65 KMSO 201905
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
105 PM MDT Sun Jul 20 2025

.DISCUSSION...

KEY MESSAGES:

-  Well below normal high temperatures and increasing rain and
   storm potential on Monday

-  Monday storms could produce moderate to heavy showers with
   concerns for localized flooding/ debris flows along US-95 and
   US-12 in north-central ID

-  Widespread showers and thunderstorms on Tuesday

Similar to Saturday the region remains cooler than normal with
clouds. The exception is southwest MT where breezy afternoon winds
may combine with low humidities to produce near critical fire
weather concerns. These conditions will continue, for only
southwest MT, on Monday with the addition that any thunderstorms
that develop during the afternoon will be capable of gusty outflow
winds up to 50 mph.

This evening the first showers are expected in north-central ID.
The models continue to demonstrate a stationary boundary
developing between north-central ID and west-central MT. Afternoon
showers and thunderstorms may become enhanced along this boundary
on Monday, with high resolution models suggesting rain rates of
0.50 to 0.75 inches per hour. The models have been very consistent
demonstrating this as a very narrow boundary. For many this will
be feast or famine in regards to precipitation amounts. There is
some concern that these rates could produce localized flash
flooding or debris flows along the US-95 corridor south of
Grangeville. We will continue to monitor the evolution of future
forecasts. By Tuesday, the trough will move over northwest MT and
widespread showers and thunderstorms are expected north of I-90.

Overall precipitation amounts will depend greatly on whether your
location actually receives a shower or thunderstorm. For instance,
25% of models show ZERO precipitation for the US-95 corridor and
Camas Prairie while 25% have up to 0.75 of an inch. Higher terrain
of the Clearwater Mountains have 0 to 1" of precipitation and
most of western MT south of I-90 has a 25% chance of ZERO and 25%
have up to 0.40 inches in the highest terrain. As always, higher
amounts will be possible from a single stronger storm or training
of storms.

Confidence in precipitation amounts is highest in northwest MT
and most of the precipitation will happen overnight Monday into
Tuesday. There is a 70-80% chance of receiving greater than 0.25
inch by Tuesday afternoon and higher terrain a 50-70% chance of
receiving a 0.50 inch or more.

A trend of warming and drying returns Wednesday. Still there
remains no signal in the models of a prolonged, strong summer high
pressure ridge. In fact, expect afternoon winds to increase by
Friday as yet another Pacific trough moves closer to the region.


&&

.AVIATION...A deepening trough over the Pacific Northwest and
increasing southwesterly flow will bring rising moisture and an
unsettled pattern to north-central Idaho and western Montana
through Tuesday. Isolated showers will be possible this afternoon
from north-central Idaho into west-central Montana. While most
terminals will remain VFR, brief reductions in visibility or
ceilings are possible in showers. Winds are forecast to be lighter
today in most places, and generally in the 15-25 kts range.

By Monday, a frontal boundary and upper jet will increase lift and
instability, leading to showers and isolated thunderstorms.


&&

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

$$