Area Forecast Discussion
Issued by NWS Missoula, MT

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730
FXUS65 KMSO 172059
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
159 PM MST Wed Jan 17 2018

.DISCUSSION...Fog and low cloud cover has been slow to lift today
but improvements are beginning to show up on latest satellite
loops with the trend to continue through this afternoon. Cloud
cover is spreading into the region ahead of the next precipitation
producing weather system.

Freezing rain remains a concern in the valleys of northwest
Montana tonight and Thursday morning, so Winter Weather Advisories
have been issued with primary concern being black ice on
roadways. Temperatures warm during Thursday morning so travel
conditions are expected to improve by late morning.

The overall setup for Thursday and Thursday night`s trough has
not changed much other than precipitation to have a many hour
delay for the onset of precipitation and a general slower movement
of the entire weather system. Snow levels are likely to remain
above most valley floors for much of Thursday and the main
transition from rain to snow should occur during the evening for
most. North- central Idaho above 3000 feet, including the Camas
Prairie have a better chance for rain to change to snow during
the afternoon so Winter Weather Advisories have been issued for
the development of slick roadways during the evening and
overnight. Snow may also linger into Friday morning.

Once the precipitation arrives to southwest Montana during by
early evening, rain or wet snow is expected to freeze on roadways
including I-90 from Clinton to Butte and Homestake Pass. The
worst conditions are most likely during the late evening and into
the overnight. Conditions through Lemhi County are also to be
similar to southwest Montana but snow will take longer to develop
in Salmon. Winter Weather Advisories have been issued to account
for the change from wet to snow covered and icy roadways. Snow is
likely to linger through Friday morning.

Snow showers will continue on Saturday under a westerly flow,
especially across the mountains along the Montana/Idaho border.
Valleys will see occasional snow showers as well but any
accumulations will be light. Brief high pressure will bring drying
late Saturday into Sunday with shower activity diminishing.

An active weather pattern is expected all of next week with
several disturbances bringing bouts of wintry weather. Snow levels
will be down to valley floors much of the week but as is typical,
the majority of snowfall will be across the higher terrain. At
this point, significant storm systems are not anticipated but
Sunday night into Monday and again mid week stand out as the best
chances for precipitation. The main take-away message is roadways
will snow packed and slippery at times, especially over the
passes throughout the coming week.


&&

.AVIATION...Low stratus with ceilings ranging between 500 and 1000
feet have plagued the Mission and Flathead Valleys this afternoon.
High clouds are currently moving over the region which has helped
to improve surface fog and stratus at KMSO and KSMN, but stratus
still hangs on at KGPI. The next weather system is expected to
bring light freezing rain from Interstate 90 west of Alberton,
Highway 200 west of Plains and from Troy to Kalispell to Whitefish
to West Glacier between 18/0900Z and 18/1500Z. A cold front will
bring lowering snow levels to around 4,000 feet by Thursday
afternoon and to 3,000 feet by Thursday night which will obscure
mountain ranges and passes. KBTM and KSMN will experience the best
chances for rain changing to snow with gusty winds with the
frontal passage between 19/0300Z and 19/0800Z.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory from 5 PM Thursday to 11 AM MST Friday
     Butte/Blackfoot Region.

     Winter Weather Advisory from 5 PM Thursday to 11 AM MST Friday
     Bitterroot/Sapphire Mountains.

     Winter Weather Advisory from 2 AM to 9 AM MST Thursday Lower
     Clark Fork Region.

     Winter Weather Advisory from 2 AM to 9 AM MST Thursday
     Flathead/Mission Valleys.

     Winter Weather Advisory from 2 AM to 9 AM MST Thursday West
     Glacier Region.

     Winter Weather Advisory from 11 PM this evening to 9 AM MST
     Thursday Kootenai/Cabinet Region.

     Winter Weather Advisory from 5 PM Thursday to 11 AM MST Friday
     Potomac/Seeley Lake Region.

ID...Winter Weather Advisory from 8 PM Thursday to 11 AM MST Friday
     Eastern Lemhi County.

     Winter Weather Advisory from 5 PM Thursday to 11 AM MST Friday
     Western Lemhi County.

     Winter Weather Advisory from 1 PM Thursday to 10 AM PST Friday
     ABOVE 3000 FEET for the Lower Hells Canyon/Salmon River
     Region.

     Winter Weather Advisory from 4 PM Thursday to 10 AM PST Friday
     ABOVE 3000 FEET for the Orofino/Grangeville Region.

     Winter Weather Advisory from 4 PM Thursday to 10 AM PST Friday
     Southern Clearwater Mountains.

&&

$$



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