Lake Effect Snow Advisory 2, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
310 PM MST Fri Dec 16 2016

.DISCUSSION...Gusty east to northeasterly winds, snow, and
blowing snow continue to create issues with roads across
southwestern Montana and Lemhi County this afternoon, and will
continue into the early evening. The current Winter Weather
Warnings remain in place until 5PM MST this evening.

The Flathead/Missoula/Bitterroot Valleys continue to see gusty
easterly winds creating blowing snow from the snow that fell
yesterday, and has lowered visibility to less than one quarter
mile at times. This will continue to until around 5PM MST this
evening. This is also when the current Winter Weather Advisories
expire. Other current impacts from the cold and wind are the wind
chills. Currently (2PM MST), wind chills are 20 to 25 degrees
below zero in the Butte/Blackfoot region and 5 to 10 below zero
across the remainder of the advised valleys mentioned above in
western Montana.

Later this evening and overnight when the northeasterly winds
diminish, we are expecting a fairly intense lake effect snow band
to develop over Flathead Lake that could produce locally heavy
snow on the south and eastern side of the lake. 3 to 6 inches of
snow will be possible overnight with locally higher amounts.
Winter highlights may be needed if the band does begin to develop.

Along with the winds diminishing overnight, we are also expecting
skies to partially clear. Due to all the recent snow across the
region and an arctic air-mass in place, we are expecting
dangerously cold temperatures for the mountains and valleys along
the Continental Divide. Butte/Avon/Elliston, just to name a few,
will be as cold as they have been in 2 or 3 years, with 30 below
zero or lower expected. The remaining valleys of western Montana
will likely be below zero as well, but not quite as cold, though
some will see their first subzero temperatures of the season. Even
a slight breeze tomorrow morning will feel extremely cold and
will cause frostbite to exposed skin in just a few minutes.
Weekend high temperatures will struggle to make it out of the
single digits and teens for many.

By Sunday into Monday, a return to an active weather pattern will
resume with some slightly warmer temps. In fact, three systems
with quite a bit of precipitation will move through the Northern
Rockies. The first one will arrive Sunday night and last into
Monday; the second system looks to be the wetter of the three and will
move into the region Tuesday into Wednesday morning, while
another system is expected by next Thursday into Friday. In
between each system, expect persistent mountain snow showers.
This westerly flow weather pattern is favorable for ABUNDANT
MOUNTAIN SNOWS.

Various impacts to the valleys are possible across the region. A
west to northwest influence could bring snow banding to western
Montana. As it gets a bit warmer, it's even possible a little
freezing rain could occur in some of the valleys of far NW MT.
Details for impacts to the valleys next week will come as we get
closer to each storm.

Models are hinting at another surge of cold Canadian air around
Christmas weekend. The main message is: NEXT WEEK WILL CONTINUE TO
RECEIVE ACTIVE WINTER WEATHER STORMS.

&&

.AVIATION...The biggest issue for all terminals through early to
mid evening will be breezy east to northeast winds producing
blowing snow and reduced visibilities; light snow showers are
also possible. After 17/0400z, snow showers and winds will have
diminished and very cold temperatures will settle into the region.
Subzero temps will occur at all terminals, with KBTM having the
coldest temps around -20 to -30F. KGPI, KMSO, KSMN will record
low temps from -10 to -20F degrees through 17/1600z

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 5 PM MST this afternoon
     Missoula/Bitterroot Valleys.

     Winter Weather Advisory until 5 PM MST this afternoon
     Flathead/Mission Valleys.

     Winter Weather Advisory until 5 PM MST this afternoon West
     Glacier Region.

     Winter Weather Advisory until 5 PM MST this afternoon
     Potomac/Seeley Lake Region.

     Winter Storm Warning until 5 PM MST this afternoon
     Butte/Blackfoot Region.

ID...Winter Weather Advisory until 4 PM PST this afternoon Northern
     Clearwater Mountains...Southern Clearwater Mountains.

     Winter Weather Advisory until 4 PM PST this afternoon Lower
     Hells Canyon/Salmon River Region...Orofino/Grangeville
     Region.

     Winter Storm Warning until 5 PM MST this afternoon Eastern Lemhi
     County.

&&