Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 251059
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
359 AM MST Sun Feb 25 2018

...Snow, blowing snow and gusty winds to create travel impacts
into Monday morning...

.DISCUSSION...Snow will begin to increase across central Idaho and
northwest Montana this morning, shifting into the rest of western
Montana this afternoon and evening. The heaviest precipitation is
still expected through north central Idaho and along the
Idaho/northwest Montana border where several inches of snow will
be possible for valleys and over a foot of snow is possible in the
higher terrain. Snow levels will remain low enough that most all
locations should experience snow.

Another concern with this system is for gusty southwest winds,
which will cause areas of blowing and drifting snow, especially
in the higher terrain. These winds will also act to cause
downsloping into the larger valleys today, such as the
Missoula/Bitterroot and Mission. This downsloping will limit snow
amounts in these locations. The Camas Prairie in Idaho will see
potential for gusts to near 50 mph, which could cause periods of
low visibility into the afternoon.

Forecast models still indicate favorable conditions for
potentially intense snow bands to develop across northwest Montana
late this afternoon, shifting south into north central Idaho and
the rest of western Montana this evening. Wherever these bands set
up, periods of very intense snowfall will be possible, leading to
poor visibility and rapidly changing conditions over short
distances. The exact placement of these bands is difficult to
determine at this time, however areas from Lookout Pass east to
Seeley Lake and south seem to be the most favored.

Snow showers will continue to shift southward into Lemhi County
into Monday morning, with a general drying trend from north to
south occurring through the day.

A drier airmass moving in Monday night will lead to clear skies
across southwest Montana, central Idaho, Lemhi county and parts of
west-central Montana. Tuesday morning will likely be the coldest
day of the week with morning temperatures in the low teens to
single digits across many areas. Southwest Montana and Lemhi
county could see areas with below zero temperatures Tuesday
morning.

A weak weather system is expected to move in during the day
Tuesday into Tuesday night and will likely bring light snow
accumulations across northwest Montana and west-central Montana.

By the later half of next week, a deep trough is expected to
develop over the Pacific Northwest and slowly track eastward
toward the Northern Rockies. Although the details are still
uncertain, confidence is high for more unsettled weather Thursday
through the weekend.


&&

.AVIATION...Lowering ceilings and snow will gradually spread into
northwest Montana and north central Idaho this morning, then into
the rest of western Montana this afternoon and evening. Mountains
and passes are expected to see moderate to heavy snow for much of
the day. Intense showers are forecast to organize into snow bands
during the afternoon and evening, so valley locations will also
have periods of moderate to heavy snow during the afternoon and
evening. Snow showers will gradually decrease from north to south
late tonight into Monday morning however, lowered ceilings will
likely continue to obscure the terrain into Monday morning. Winds
will increase from the southwest on ridge tops this morning, then
mix down into valleys by early afternoon. Wind gusts up to 30 kts
will be possible for many valley locations this afternoon with
gusts up to 45 kts possible near ridge tops. Wind shear of 35 to
40 kts will be possible in the lowest 2000 feet for airfields KMSO
and KBTM this morning. Winds will shift to more of a westerly
direction late this afternoon and evening, then gradually decrease
area wide overnight.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning until midnight MST tonight Lower Clark Fork
     Region.

     Winter Weather Advisory until midnight MST tonight
     Flathead/Mission Valleys...Kootenai/Cabinet Region.

     Winter Weather Advisory until midnight MST tonight West Glacier
     Region.

ID...Winter Weather Advisory until 11 PM PST this evening
     Orofino/Grangeville Region.

     Winter Weather Advisory until 11 PM PST this evening Northern
     Clearwater Mountains...Southern Clearwater Mountains.

&&

$$


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