Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 012148
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
247 PM MST SUN FEB 1 2015

...Periods of winter driving conditions throughout this week...

.DISCUSSION...Precipitation continues to spread eastward into
western Montana and north central Idaho this afternoon dropping
accumulating snow down to the valleys of Montana, including
Missoula and Kalispell. Lookout, Lolo, and other mountain passes
have also become impacted this afternoon, and will see a few
inches of additional snow through Monday morning. Roads that
become snow-covered could be slick through Monday morning,
especially mountain roads. Snow intensity is still expected to
increase this evening with the approach of the upper level jet
stream, mainly for the higher terrain. Downsloping effects for the
larger valleys are likely, generally for the I-90 corridor and
south.

Snow showers are expected to taper off for central Idaho and
western Montana by Monday morning. The next wave of appreciable
precipitation is expected to move in by Monday evening into
Tuesday morning. This system will produce additional accumulating
snow for the mountains and mountain passes including Lookout,
Lolo, and Marias passes, with a chance of a rain/snow mixture or
rain for the valleys. Valley roads that remain wet overnight
Monday night could develop black ice and become hazardous if
untreated.

Forecast uncertainty is unusually high for Tuesday night and
Wednesday. Some model runs have been showing a resurgence of the
arctic front into Western Montana with a low pressure system in
central and southern Idaho. This is a great set up for a lot of
snow in the southern Bitterroot through Georgetown Lake, Anaconda,
and Butte. However, the most recent model runs have decreased the
strength of this system significantly. If this were to happen, it
would be a big change to the forecast. We have raised the
probability of precipitation in the forecast and increased the
snow during this time period. At this point it is likely there
will be at least a light snow event Tuesday night and Wednesday,
with an outside chance of six inches in Butte and more over
Homestake Pass.

Northwest Montana and north central Idaho should remain wet and
snowy with residual moisture throughout the day on Thursday, but
Friday into Saturday look to be the wettest period yet as a strong
atmospheric river from the Pacific makes an impressive push into
the area. Snow should stay near pass levels, so valleys should see
mainly rain. In additional to hazardous travel conditions over
passes, the quantity of rain could pose issues for roadways with
rock outcrops, such as Highway 12 from Lolo to Kooskia. Also with
the cool rain in valleys, newborn livestock will likely be at risk
during this period. The atmosphere dries out on Sunday, but
moisture looks to return for early next week.

&&

.AVIATION...Snow showers are impacting much of the northern
Rockies this afternoon causing reduced ceilings and visibility at
area terminals. Expect showers to continue through the evening,
when downsloping will start to reduce but not eliminate them at
area terminals. Expect mountain obscurations and snow to continue
through the night.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY until 9 AM MST Monday
     Flathead/Mission Valleys...Missoula/Bitterroot Valleys.

     WINTER WEATHER ADVISORY until 9 AM MST Monday
     Bitterroot/Sapphire Mountains...Lower Clark Fork Region.

     WINTER WEATHER ADVISORY until 9 AM MST Monday Potomac/Seeley
     Lake Region...West Glacier Region.

     WINTER WEATHER ADVISORY until 9 AM MST Monday Kootenai/Cabinet
     Region.

     WINTER WEATHER ADVISORY until 9 AM MST Monday Butte/Blackfoot
     Region.

ID...WINTER WEATHER ADVISORY until 8 AM PST Monday ABOVE 3000 FEET
     for the Northern Clearwater Mountains...Southern Clearwater
     Mountains.

     WINTER WEATHER ADVISORY until 9 AM MST Monday ABOVE 4500 FEET
     for the Eastern Lemhi County.

&&

$$




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