Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 262200
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
300 PM MST Sun Feb 26 2017

.DISCUSSION...A southwest moving, "back door" Canadian cold front
continues to move across Western Montana resulting in snow and
gusty winds to the Continental Divide. This has especially been
the case in Kalispell and throughout the Flathead Valley where
snow totals of 2 to 3 inches with winds gusting to 30 mph have
been common. However conditions there and farther north and west
will likely continue to improve heading into this evening. Thus
the Winter Weather Advisories will continue until their planned
expiration at 11pm MST.

However farther to the south the situation continues to evolve as
the cold front further interacts with deepening moist flow aloft.
This has resulted in the development some some fairly impressive
linearly shaped snow showers. Areas outside these showers are
seeing periods of light snow but under the showers we`re seeing
periods of moderate snowfall that could quickly accumulate on area
roadways. The previously issued Winter Weather Advisories appear
sufficient to highlight the potential public impacts for this
evening. However further evaluation of the latest data suggests
that this snowfall, albeit lighter at times, will continue
overnight and through Monday morning and thus the Advisories
issued for SW Montana, North Central Idaho & West Central Montana
mountains have been extended thru 11am MST/10am PST Monday
morning.

Some models are showing subtle indicators that a period of
heavier snow may be possible across the Camas Prairie & Hells
Canyon areas starting very early Monday morning. While it`s low
confidence at this point, it`s possible that we may need to
upgrade to a warning should the modeled upper level wave over
coastal Oregon and strengthening surface low actually develop over
the region.

Snow showers are unlikely to cease on Monday, but they slowly
weaken and become less frequent. After this potential brief lull
a second upper level wave will help kick off another round of more
intense snowfall across the Northern Rockies late Monday night
and persist through Tuesday. An additional 1 to 3 inches (locally
up to 5 inches) are possible across most valleys with 6 to 12
inches across the higher terrain. Unstable conditions behind a
passing cold front will help produce some fairly intense snow
showers along with winds gusting to 30 mph at times Tuesday
afternoon.

Snow showers continue Wednesday with increasing winds during the
late morning through the evening. A strong jet stream aloft
combined with atmospheric mixing to about 10k ft above ground will
likely lead to widespread surface winds in the 20 to 30 mph
range, with gusts in the 30s and 40s. Areas around Butte, Deer
Lodge, Anaconda, all terrain above 6000 ft are a locations that
will be especially windy. Wind combined with snow showers will
make for periods of low visibility and difficult travel.

Scattered showers in northwest flow with breezy afternoons
continues Thursday & Friday. Temperatures become more mild by the
end of the week with highs approaching seasonal averages, roughly
upper 30s to upper 40s. Friday night into Saturday, models are
still showing a strong cold front coming through, with a round of
widespread rain transitioning to snow for much of the Northern
Rockies. Winds would again be breezy as this front comes through,
gusting in the 40 - 50 mph range. I-90 from Butte to Deer Lodge
could see strong crosswinds affecting high profile vehicles. Along
with the wind, this system looks to usher in colder air from the
northwest, bringing below average temperatures back into the
forecast.

&&

.AVIATION...Periods of snow, reduced visibility and lowered ceilings
are expected to continue through tonight at the majority of area
air fields. Gusty winds at KGPI will slowly draw down this evening
with light snow gradually tapering off as well. However snow
showers will continue to increase at KMSO and KBTM through this
evening and likely persisting overnight. KSMN will experience some
showers and breezy winds, but overall the potential for aviation
impacts remains low here.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until noon MST Monday
     Bitterroot/Sapphire Mountains.

     Winter Weather Advisory until 11 PM MST this evening
     Flathead/Mission Valleys.

     Winter Weather Advisory until 11 PM MST this evening West
     Glacier Region.

     Winter Weather Advisory until 11 PM MST this evening
     Kootenai/Cabinet Region.

     Winter Weather Advisory until noon MST Monday Butte/Blackfoot
     Region...Potomac/Seeley Lake Region.

     Winter Weather Advisory until noon MST Monday Lower Clark Fork
     Region.

ID...Winter Weather Advisory until 11 AM PST Monday Lower Hells
     Canyon/Salmon River Region...Orofino/Grangeville Region.

     Winter Weather Advisory until 11 AM PST Monday Southern
     Clearwater Mountains.

     Winter Weather Advisory until 11 AM PST Monday Northern
     Clearwater Mountains.

&&

$$



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