455
FXUS65 KMSO 221006
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
406 AM MDT Wed May 22 2024

...Heavy Snow in the Higher Terrain Across Lemhi County into
Southwest Montana by Thursday Morning...

.DISCUSSION...The strong low pressure system is currently moving
into Washington this morning. The low is still anticipated to
slide towards southern Idaho by tonight then lift towards the
northeast on Thursday over Yellowstone National Park. The path of
this low will bring widespread precipitation to the Northern
Rockies with most locations experiencing rainfall totals in excess
of a half of an inch over the next 48hrs. Snow levels will drop
tonight to around 4500-5500 feet. The bulk of the precipitation
will be across Lemhi county into southwest Montana by Thursday
morning during the lowest snow levels causing significant
snowfall. The Bitterroot, Sapphires and mountains of southwest
Montana are expected to receive over a foot of new snow by
Thursday morning. Lost Trail and Homestake along with portions of
Highway 1 have a 60-80% chance of receiving over 6 inches of new
snow tonight into Thursday morning. The uncertain of this system
is how low will the snow levels become by Thursday morning and
which communities will be impacted by heavy snow. Areas that are
being closely monitored is Philipsburg to Georgetown Lake, Deer
Lodge to Butte and Tendoy to Gilmore Summit.

A second low pressure system is still expected to move through the
region on Saturday causing more widespread precipitation. The
latest guidance is indicating more of a broad system keeping the
snow levels higher, but impacts to mountain passes could be an
issue by Sunday morning.

A ridge of high pressure is still anticipated to for the first
half of next week causing a warming and drying trend.


&&

.AVIATION...The low pressure system is being to make its way into
Washington this morning then track into southern Idaho tonight.
Rain showers are already being experienced in northwest Montana
tonight, even impacting KGPI. The precipitation will be increasing
in coverage and intensity throughout the day along with lowering
ceilings. All terminals will be impacted by this system over the
next 24 hours. Snow levels will be lowering causing the
precipitation to change over to snow tonight for KBTM.


&&

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

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

&&

$$