Georgetown, Montana Weather Forecast Discussion

761
FXUS65 KMSO 100954
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
354 AM MDT Wed Sep 10 2025
.DISCUSSION...
KEY MESSAGES:
- Thunderstorms each day through Friday featuring gusty outflow
  winds and heavy rain, focused in the afternoon/evening hours
- Temperatures cooling through Saturday, returning closer to
  seasonal normals
- Turning wetter most areas Thursday-Saturday, improving air
  quality
The very slow moving upper level low pressure system over northern
California will begin to shift northeastwards over the next 72
hours. As it does so, spokes of moisture and energy will rotate
around the low into western Montana and north central Idaho.
Showers and thunderstorms will be common through Thursday,
especially focused in the afternoon and evening hours. The main
threats with storms will be gusty outflow winds up to 40 mph,
lightning and heavy rain. Measurable rainfall will not be uniform
across the region through Thursday due to the convective nature of
precipitation. Most areas may only see a light sprinkle, while
locations directly under a storm may see 0.30 to 0.75" of rain in
a short period of time. Flood prone areas and recent fire burn
scars may be prone to debris flows and flash flooding if they take
a direct hit, but overall confidence in this occurring is less
than 10 percent for any one locations.
For this morning, there may be a few showers across northwest
Montana. By this afternoon, there is a higher probability that
showers and thunderstorms will develop over Idaho County and
across the southern Bitterroot Valley. Northwest Montana will be
drier. This shower activity will track to the north during the
evening hours, then weaken as it moves towards Flathead Lake. As
mentioned before, rinse and repeat on Thursday but the shower
activity will have more of a southeast to northwest movement to
them.
There is considerable uncertainty for Friday...Just imagine how
hard it might be to try to predict a swirling eddy in the bend of
a river. A few models depict one of these eddies wobbling west
towards western Montana later Friday(wetter), while others keep it
further east of us(drier). One way to capture this uncertainty is
to look at the 50th percentile total rainfall from the NBM. It
depicts that the focus for heavier rainfall amounts could extend
from Clearwater County east and north towards Polson and Marias
Pass with 0.10 to 0.20 inches. Outside of that swath, rainfall
ranges from Zero to several hundredths. Now if we`re able to get a
few thunderstorms into the mix, then any one location could get
more.
Fog could develop in areas that receive rainfall Friday and
Saturday night.
Another trough with clouds and showery weather is possible by
Monday.
&&
.AVIATION...A few showers are possible across the Bob Marshall
Wilderness and Glacier National Park this morning. By the
afternoon showers and thunderstorms are possible across north-
central Idaho into southwest Montana. Expect gusty outflow winds
to 40 kts, small hail, heavy rain, lightning, and brief terrain
obscuration. The terminals that could be most impacted are MSO and
HRF between 22z and 0300Z Thursday(4pm to 9 pm MDT today). Watch
for patchy valley fog development tonight, especially where rain
occurs today. Showers and thunderstorms are expected again on
Thursday and Friday.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$

NWS MSO Office Area Forecast Discussion