Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 200915

Area Forecast Discussion
National Weather Service Missoula MT
315 AM MDT Fri Oct 20 2017

.DISCUSSION...Widespread precipitation in eastern Oregon and
Washington is slowly moving westward toward the Northern Rockies.
This rain will move into northwest Montana and west central Idaho
in the next few hours and into much of west central Montana by mid
to late morning. Snow levels are starting off pretty high but
will lower as the front moves through today. Gusty westerly winds
also develop as the front moves through today. Heavy rain may
have impacts such as mudslides to areas in central Idaho.

The tricky part of the forecast today will be potential impacts
from snow. Snow levels will lower throughout today from west to
east. It`s looking like by the time snow levels lower to mountain
pass levels the heaviest precipitation will have ended which will
limit the amount of snow accumulations. A quarter to one half
inch of rain is expected below snow levels.

A more significant jet stream will move over the region late
Saturday through Monday. The timing of the weekend weather system
from computer model runs has been pretty consistent for rain and
stronger wind to develop first in Idaho late Saturday afternoon,
then spread farther east by Sunday morning. Snow levels will be
somewhat higher around 6000 feet this weekend with rain amounts in
the terrain below this level in the 1 to 3 inch range resulting
in local mud and rock slides.  The winds in the higher terrain
will also increases the chance of falling trees in recent burn
areas. After Monday it looks generally drier, though a weather
system midweek moving into the Plains may brush northwest Montana.

Models are starting to show signs of a cold arctic system by late
next week but there is quite a bit of uncertainty especially since
it is 7 days out.


.AVIATION...A cold front will bring a west to east progression of
lower ceilings and reduced visibilities associated with rain and
mountain snow above 5,000 feet. Wind shift from southerly to more
northerly is expected with the front.



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