Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 041134
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
434 AM MST Sun Dec 4 2016

...SNOW...WIND...AND COLD TEMPERATURES TO IMPACT NORTHERN ROCKIES
THROUGH THE COMING WEEK...

.DISCUSSION...

The first in a series of storm systems will move across the
Northern Rockies today, impacting area travel. Snow will continue
to be present across much of the region, with area mountain
passes and other high elevation areas receiving up to a foot of
accumulation. The combination of snow covered roadways, occasional
wind, and low visibility will create hazardous winter driving
conditions. No location will be completely spared from snow
covered roads, including high population areas of western Montana.
The snowfall will be followed by a brief period of relatively
cold air moving west of the Continental Divide overnight.

A more significant push of cold air from the east is anticipated
to arrive Monday evening and continue through Tuesday. Strong east
winds will develop through terrain gaps, such as Bad Rock Canyon
(near Kalispell) and Hellgate Canyon (near Missoula). Wind chill
temperature will cool to well below zero within corridors near the
Continental Divide for much of Tuesday. Locations east of
Kalispell along Highway 2 may experience wind chill as cold as 25
below zero during this time. It takes very little time for
frostbite to occur at this cold of wind chill.

Cold air will have infiltrated most of the Northern Rockies by
Wednesday morning, with air temperatures dropping well below zero
as east winds rapidly diminish.

Very cold air will be firmly over the Northern Rockies until
Thursday afternoon, when a surge of Pacific moisture is
anticipated to arrive overhead. The relative warmth from this
moisture surge will quickly moderate temperatures, as well as
increase the potential for heavy snow to develop. Models have been
fairly consistent depicting this moisture surge, which would
result in a widespread snow impact Thursday night through Friday.
Stay tuned because this scenario is one of the most reliable heavy
snow patterns for the Northern Rockies.

Even beyond next weekend, the pattern remains very active, with
several additional feet of mountain snowfall appearing quite
likely. Temperatures will return to near the seasonal average
during this time as well.

&&

.AVIATION...Periodic snow showers will move across Northern
Rockies air space during the next 24 hours and beyond. Much of
snow activity will be concentrated at high elevations. However,
there will be a threat of temporary reductions in ceiling and
visibility due to snowfall intensity overcoming a relative drying
(downslope) effect for all major area terminals. The surface
pressure gradient will increase northwesterly wind gusts to 25
knots at KBTM 04/1800Z through 05/0300Z. Also, northeast winds
will gust to 20 knots at KGPI 05/0000Z through 05/1000Z. Terrain
obscurations will be commonplace during the next 24 hours.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Watch from 11 AM MST this morning through Monday
     morning Butte/Blackfoot Region...Missoula/Bitterroot
     Valleys.

     Winter Storm Warning until 11 AM MST Monday Bitterroot/Sapphire
     Mountains.

     Winter Storm Warning until 11 AM MST Monday Lower Clark Fork
     Region.

     Winter Weather Advisory until 11 AM MST Monday Flathead/Mission
     Valleys.

     Winter Storm Warning until 11 AM MST Monday West Glacier Region.

     Winter Weather Advisory until 11 AM MST Monday Kootenai/Cabinet
     Region.

     Winter Storm Warning from 11 AM this morning to 11 AM MST Monday
     Potomac/Seeley Lake Region.

ID...Winter Storm Warning from 8 AM this morning to 11 AM MST Monday
     Eastern Lemhi County...Western Lemhi County.

     Winter Weather Advisory until 10 AM PST Monday ABOVE 3000 FEET
     for the Lower Hells Canyon/Salmon River Region...
     Orofino/Grangeville Region.

     Winter Storm Warning until 10 AM PST Monday Northern Clearwater
     Mountains...Southern Clearwater Mountains.

&&

$$


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