Butte-Silver Bow, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

309
FXUS65 KMSO 211056
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
356 AM MST Thu Nov 21 2024

.DISCUSSION...


KEY MESSAGES:

-  An atmospheric river will bring ample moisture to the mountains
of central Idaho and northwest Montana today through Saturday.

- Slight chance for pockets of freezing rain in northwest Montana
  this morning.

- Arctic air lingering along the Continental Divide this weekend.


Moisture from the atmospheric river has made its way into the
Northern Rockies last night causing widespread precipitation.
Currently snow levels are low enough across northwest Montana that
all locations have been receiving snow so far. A few higher
elevation observations across northwest Montana are starting to
creep above freezing as warm air makes its way into the region.
This warming aloft could create pockets of freezing rain for a
short period of time this morning. The remainder of the region
appears to have a fairly well mix lower atmosphere that the
precipitation will be rain or gradually changing over to rain as
the snow levels rise to around 6000 feet.

The atmospheric river will be fairly consistent through at least
Saturday with pulses of heavier precipitation, such as Friday
morning then again on Saturday. Saturday`s pulse will be
associated with a decent amount of energy breaking away from the
large low pressure system sitting off the Pacific Northwest coast.
That piece of energy has the potential to cause a secondary low
pressure system that will track along the Canadian border. The
strength and path of this disturbance will be the deciding factor
on how much arctic air will be able to be pushed over the
Continental Divide in around Glacier National Park. The bulk of
the models, around 80%, still show the very cold air staying east
of the Divide.

A low amplitude transitory ridge of high pressure slides over the
Northern Rockies Sunday into Monday causing a decrease in the
shower activity. Then the large low pressure system off the coast
is anticipated to push to the southeast into the Great Basin
region by mid next week. The path of this low will put the
Northern Rockies in a northwesterly upper level flow pattern for
Thanksgiving into the following weekend. This flow pattern
meanings cooler than average temperatures with the potential for
periods of light snow showers.

&&

.AVIATION...The atmospheric river will continue to push into the
Northern Rockies for the next 24 to 48 hours. KGPI, KSMN and KBTM
could still experience periods of light snow this morning which
will reduce visibilities. Then the snow levels will rise high
enough by this afternoon that the precipitation type will be rain.
Mountain and passes obscurations will be common throughout the
period.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 11 AM MST this morning for
     Flathead/Mission Valleys...Kootenai/Cabinet Region...Lower
     Clark Fork Region...West Glacier Region.

ID...None.
&&

$$