Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 211028
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
428 AM MDT Sat Oct 21 2017

.DISCUSSION...

High based snow showers will slowly diminish across the Northern
Rockies this morning. These showers have produced enough snow to
lightly and temporarily cover some area mountain pass roadways
this morning. Beware of hazardous winter driving conditions
briefly this morning at the mountain passes.

A surge of relatively warm moisture and an upper level jet streak
will combine to bring widespread low elevation rain and high
mountain snow to the Northern Rockies this afternoon through much
of Sunday. The liquid water content of the rain/snow mix of
precipitation over the next couple of days will exceed 2.5 inches
for portions of the Clearwater Mountains in north central Idaho.
Many of the broad valleys of the region, such as the Missoula
Valley, will see quite a bit of downslope flow during the moisture
surge, thereby keeping total rainfall expectations below one half
inch. The snow level rising from 3500 feet this morning to over 7000
feet by Sunday morning will limit the impact of snow on roadways
to the highest mountain passes and above. Precipitation chances
quickly recede to the mountains overnight Sunday, as the jet
streak exits the region. Temperatures will warm closer to seasonal
normals into Monday, as high pressure develops overhead.

Starting Wednesday afternoon, chances of precipitation will begin
to increase as a shortwave trough moves through the region.
Precipitation is expected to begin increasing over northwest
Montana Wednesday afternoon and then spread southward into central
Idaho, west-central and southwest Montana. Mountain passes will
likely see periods of moderate snow especially along the
Continental Divide on Wednesday night. For valleys, the best
chance for snow accumulation will be across southwest Montana
valleys and valleys near the Continental Divide. For west-
central Montana, models are in good agreement with moderate
precipitation Wednesday night, but there is a lot of uncertainty
in the snow levels at the moment. Stay tuned for more info.

&&

.AVIATION...

Rain and snow showers will slowly diminish across the Northern
Rockies through 21/1400Z. Occasional terrain obscurations in low
clouds and snow will be present during this time. After 21/2100Z,
widespread rain and snow will develop near area terminals. Low
ceilings and obscured terrain will become common for the remainder
of the next 24 hours. Gusty surface winds will accompany the
incoming precipitation this afternoon, particularly for KGVL (up
to 35 kts) and KBTM (up to 25 kts). Snow levels will rise from
around 3500 feet now to 6000 feet by 21/2100Z and continue rising
thereafter.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$



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