474
FXUS65 KMSO 222107
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
207 PM MST Sat Feb 22 2025

.DISCUSSION...


KEY MESSAGES:

-  Increased snowmelt and runoff tonight into Monday, bringing
   the risk of minor flooding to low-lying and poor drainage areas
   and to small streams and creeks from potential ice jam
   releases.

-  Widespread rain and high elevation mountain snow expected
   Sunday into Monday.

-  Areas of refreeze of wet roads tonight through Sunday morning
   across western Montana with cold subsurface ground temperatures
   in place.

Light precipitation has already started to move through the
Northern Rockies today causing some snow accumulations in the
higher terrain (above 6000 feet) and scattered light rain in lower
elevations/valleys.

The head of the atmospheric river is currently pushing into
western Washington and is expected to enter the Northern Rockies
later tonight and last into Monday and possibly Tuesday. The
forecast still appears to be on track for rising snow levels with
warm, wet and breezy conditions in the lower elevations. The main
concern continues to be be rapid snow melt runoff, creating
flooding in poor drainage areas. Another concern will be the break
up of ice on small streams and creeks across the region. The
higher mountain peaks along the Montana/Idaho border and around
Glacier National Park are anticipated to receive 6 to 18 inches
of new snow during this time.

A low pressure system is expected to move through the Northern
Rockies late Monday into Tuesday. This low will bring another
round of widespread precipitation, but amounts will not as
significant as what is expected during the atmospheric river. Snow
levels will start off fairly high and then are still expected to
drop to around 3500 feet by Tuesday morning. The cold front is
expected to bring breezy conditions on Tuesday which is expected
to keep temperatures above seasonal averages for this time of
year.

A fairly strong ridge of high pressure is being depicted in the
majority of the extended models by mid week and lasting into the
weekend. This ridge will keep fairly mild conditions over the
region with the potential for fog and low stratus to develop in
the valleys.

&&

.AVIATION...Expect lowering ceilings and visibility due to
incoming atmospheric river moisture from the west tonight and into
the early morning hours Sunday. Blustery south to southwest winds
will predominantly affect KHRF, KGPI, and KBTM through the late
evening, with dissipating speeds overnight. With such strong
upper level winds in place over the Northern Rockies, the presence
of low level wind shear at terminals may occur today into
tonight. Expect widespread rain and areas of fog throughout the
day Sunday across all of the Northern Rockies.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Flood Watch through Monday afternoon for Bitterroot/Sapphire
     Mountains...Butte/Blackfoot Region...Flathead/Mission
     Valleys...Kootenai/Cabinet Region...Lower Clark Fork
     Region...Missoula/Bitterroot Valleys...Potomac/Seeley Lake
     Region...West Glacier Region.

     Winter Weather Advisory from 11 PM this evening to 8 AM MST
     Sunday for Flathead/Mission Valleys...Kootenai/Cabinet
     Region...Lower Clark Fork Region...Potomac/Seeley Lake
     Region...West Glacier Region.

ID...Flood Watch through Monday afternoon for Lower Hells
     Canyon/Salmon River Region...Northern Clearwater
     Mountains...Orofino/Grangeville Region...Southern
     Clearwater Mountains.

&&

$$