672
FXUS65 KMSO 211818
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1218 PM MDT Fri Jun 21 2024

.DISCUSSION...Unstable conditions aloft over northwest Montana
has allowed for some convection today. With a trough exiting the
region, mid and upper level stability has increased through the
day, while the sunshine has warmed and destabilized the lower
levels. The balance of the two will result in some thunderstorm
development this afternoon over the Flathead Valley and along the
Continental Divide, but it will be limited in strength due to the
increasing stability aloft. Once the storms move east of the
Continental Divide and catch up with the upper level trough, they
will blossom into much stronger storms. The NWS Forecast Office in
Great Falls will be watching those storms east of the Divide for
some potentially severe weather today.

Sunday, a trough moves along the Canadian border. Most of the
rain with it will stay north of the border as well. An associated
cold front to the south will cause increased winds across western
Montana, especially southwest Montana. Ensembles are wavering on
how strong the winds will be and after trending stronger last
night, have trended a little weaker again today. We`ll continue to
watch it closely to see if it warrants a Lake Wind Advisory for
Flathead Lake, but at this time it appears there is only a 20
percent chance that winds will gust over 30 mph on Flathead Lake
Sunday. Current timing of the front in the models suggests the
peak winds would only occur with the frontal passage around 5 PM
Sunday evening on the lake.

Next week, a ridge builds in and temperatures will peak on
Wednesday near 90 degrees in western Montana and reach near 100
degrees in Riggins, ID. Along with the warming trend comes a
drying trend with relative humidity dropping into the mid teens.

Late next week on Thursday and Friday, ensembles have come into
better agreement on a trough digging into the region with another
cold front. Most of the remaining uncertainty is related to how
deep the trough will dig, and whether it will become a cutoff low
or not. The cut off low pattern typically brings more rain, but
recent model trends are towards an open wave, or trough type
pattern. This would bring some rain in the form of thunderstorms
and also more wind.



&&

.AVIATION...A trough leaving the region today has allowed for some
lingering convection this afternoon. Thunderstorms will mainly
affect the vicinity of terminal KGPI, while the building ridge
behind the trough keeps other area terminals clear.


&&

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

$$