377
FXUS65 KMSO 202030
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
230 PM MDT Mon May 20 2024

.DISCUSSION...Much like yesterday, satellite and radar loops show
showers and isolated thunderstorms developing this afternoon in
an unstable environment aided by daytime heating. After peak
heating, radar projections indicate showers will decrease in
coverage this evening. Moisture profiles show a return of cloud
cover for Tuesday morning, especially in western Montana. High-
resolution models predict another round of showers Tuesday
afternoon, but with less overall coverage than today.

The focus remains on the low-pressure system expected to impact
the region on Wednesday and Thursday. Models show strong agreement
that the low will spread rain throughout north-central Idaho and
northwest Montana starting early Wednesday. By Wednesday
afternoon, widespread rain is expected to reach western Montana as
the low-pressure center moves in.

As the low-pressure center passes through the region Wednesday
night and Thursday, snow levels are forecast to drop. Confidence
is high for snow accumulations above 6,000 feet by midday
Thursday, likely impacting travel over passes such as Lost Trail,
Homestake, and MacDonald. Some models suggest snow levels could
fall to valley floors, but confidence in snow below 5,000 feet is
low. If snow does reach lower elevations, it could damage trees
and cause power outages due to sagging vegetation or broken limbs.

A weak ridge will build over the region on Friday, bringing a
slight warming and drying trend. However, this ridge will be
short-lived as all model clusters indicate another low-pressure
system will impact the Northern Rockies on Saturday. Following
this system, models suggest a ridge of high pressure will build
over the region by early next week.


&&

.AVIATION...Radar projections indicate that showers and
thunderstorms will continue to affect north-central Idaho and
western Montana until around sunset. After some clearing this
evening, model cross-sections and soundings suggest that cloud
cover will return for Tuesday morning. High-resolution models
predict another round of showers Tuesday afternoon, but with less
coverage than today.



&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Watch from Wednesday evening through Thursday
     morning for Bitterroot/Sapphire Mountains...Butte/Blackfoot
     Region.

ID...Winter Storm Watch from Wednesday evening through Thursday
     morning for Eastern Lemhi County...Western Lemhi County.

&&

$$