Area Forecast Discussion
Issued by NWS Missoula, MT

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276
FXUS65 KMSO 182124
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
224 PM MST Thu Jan 18 2018

.DISCUSSION...Rain continues to fall this afternoon across
western Montana and north central Idaho below roughly 4500 feet.
Above 4500 feet, we`ve seen snow begin to accumulate on mountain
pass road surfaces (as seen via web cam imagery). Snow levels
will steadily drop through the remainder of the day, causing
valley rain to change to snow sometime this evening and overnight
into Friday morning. Light accumulations are anticipated for most
valleys, although a slick commute is likely once again Friday
morning. Since the flow pattern is favorable over the Camas
Prairie/Grangeville region of north central Idaho, valleys in this
area could see up to 5 inches of new snow Friday morning.

In the mountains, upwards of a foot of new snow is likely across
the Clearwaters, Bitterroots, Sapphire, and Anaconda/Pintler
ranges. Similar amounts are expected along the spine of the
Divide, particularly in west central Montana. Mountain passes in
these aforementioned areas should anticipate 5 to 10 inches of
snow accumulations tonight into Friday. Those with travel plans
over mountain passes should use caution and allow for extra time.

Snow showers will continue on Saturday, especially in the
mountains. Valleys will see occasional snow showers as well, but
any accumulations will be very light. Brief high pressure will
bring drying late Saturday into Sunday with shower activity
diminishing.

By early Monday, the active weather pattern will begin again and
is expected to last all of next week with several disturbances
bringing bouts of wintry weather. Mountains and passes will see
frequent periods of light to moderate snow above 5000 feet, while
valley snow will be more focused on the timing of the
disturbances. As such, snow showers will likely be quite variable
in the valleys, leading to the potential for localized heavier
accumulations. The best chances for widespread precipitation look
to be Sunday night into Monday, and again on Wednesday. However,
the main take-away message continues to be that roadways will stay snow
packed and slippery at times, especially over mountain passes
throughout the coming week.

&&

.AVIATION...Rain will continue to periodically cause visibility
reductions at KMSO through this evening, when rain is this
expected to transition to snow. In fact, snow will occur at all
terminals tonight, beginning after 19/0400Z and continuing through
at least 19/1500Z. Terminals KMSO and KGPI will see the most
impacts to aviation from snow (reduced vis/ceil).

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 11 AM MST Friday
     Bitterroot/Sapphire Mountains.

     Winter Weather Advisory until 11 AM MST Friday Potomac/Seeley
     Lake Region.

     Winter Weather Advisory until 11 AM MST Friday Butte/Blackfoot
     Region.

ID...     Winter Weather Advisory until 11 AM MST Friday Western Lemhi
     County.

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

     Winter Weather Advisory until 10 AM PST Friday ABOVE 3000 FEET
     for the Orofino/Grangeville Region.

     Winter Weather Advisory from 8 PM this evening to 11 AM MST
     Friday Eastern Lemhi County.

     Winter Weather Advisory until 10 AM PST Friday Southern
     Clearwater Mountains.

&&

$$



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