Tornado in Montana, May 9, 2023

Area Forecast Discussion
National Weather Service Missoula MT
155 PM MDT Tue May 9 2023

.DISCUSSION...A well-formed low pressure circulation spinning
over southwest Montana is sending moisture into central Idaho and
western Montana this afternoon. As moisture wraps around north of
the center of the low, some deep instability will fuel a 30-50
percent chance for thunderstorms this afternoon over northwest
Montana. The lack of shear in the atmosphere will keep
thunderstorms relatively tame, featuring small hail, gusty outflow
winds, and sporadic lightning.

As the low pressure responsible for today’s rain moves east on
Wednesday, a deeper trough of low pressure moves across the Great
Basin towards the Four Corners. This feature will send some Gulf
moisture northwards. Southwest Montana will have good chance
(about 60%) for some precipitation through Thursday. Thursday will
also bring a chance for thunderstorms (about 20%) over southwest
Montana.

On Friday, the skies clear out and high pressure begins to take a
stronghold. A trough of low pressure with a stationary axis will
become quite amplified over the eastern Pacific. In the meantime,
a high amplitude ridge will set up over the western U.S. Model
ensemble solutions are in good agreement that this ridge will
remain established over the Northern Rockies through the weekend
and beyond, as an upper level blocking pattern holds it in place.
The ridge will bring unseasonably high temperatures to the entire
Northern Rockies, such as 80 degrees in the broad valleys of
Montana for Saturday and Sunday.

&&

.AVIATION...Showers and thunderstorms across the region this
afternoon are causing some intermittent obscurations. Thunder snow
has been reported at terminal KBTM this afternoon, but so far
there hasn't been any accumulation on paved surfaces. The
thunderstorms are being driven by a closed upper level low slowly
migrating across the region this afternoon. As that low migrates
northeast, the showers will dissipate from south to north and
should cease by 10/06Z.

&&

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