140
FXUS65 KMSO 040927
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
327 AM MDT Sat May 4 2024

.DISCUSSION...Today should be the warmest day of the week even
though high to mid level clouds will be steadily increasing.
Temperatures are still anticipated to be 5 to 10 degrees above
seasonal averages.

A significant low pressure system will move on shore near the
California/Oregon border and track across southern Idaho Saturday
night into Sunday night. Cooler temperatures and widespread shower
activity is expected over the Northern Rockies during this time
frame. Then the low starts to track to the northeast across
southwest Montana into eastern Montana on Monday. This path
appears to enhance the precipitation across Lemhi county into
southwest Montana. Snow levels will be lowering to around 5000
feet by Monday morning, causing accumulating snow on Lost Trail,
Homestake and MacDonald Passes along with Gilmore Summit and
Georgetown Lake. These locations have a 50 to 80% chance of
receiving over 2 inches of snow by Monday morning.

The low appears to settle along the Montana and North Dakota
border and intensify Tuesday into Wednesday. This amplification
of the low will create north to northeasterly flow over the
Northern Rockies. This flow pattern is conducive to upslope flow
along the Continental Divide, especially around Glacier National
Park. Marias pass has a 90% chance of receiving over 2 inches of
new snow Tuesday into Wednesday and even a 60% chance for greater
than 4 inches.

The bulk of the low pressure system will move off to the east
while a portion of energy drifts back to the Great Basin region
during the latter part of the work week. This pattern shift will
leave the Northern Rockies in a weak northerly to easterly upper
level flow Wednesday through Friday. Temperatures will gradually
warm, but still remain below seasonal averages. Shower activity is
expected to decrease in coverage and intensity each day.

A ridge of high pressure is still expected to build over the
region during the weekend causing a warming and drying trend.


&&

.AVIATION...A ridge of high pressure will be the dominant feature
over the region today, but high level clouds will be steadily
increase as the next system approaches the region. Precipitation
is expected to start moving into north central Idaho and Lemhi
county this evening with rain showers potentially impacting KSMN
after 05/03z.





&&

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

$$