Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 182053

Area Forecast Discussion
National Weather Service Missoula MT
253 PM MDT Sun Mar 18 2018

.DISCUSSION...Snow showers will continue to spread across west-
central Montana and Idaho through the evening. Some of these
showers do have the potential to form into snow bands, that will
produce heavy snow for a short period of time. The most likely
locations to see these bands, will be along I-90 from Lookout
Pass, through Missoula and into Butte. An additional 1 to 2 inches
of snow will be possible for locations mentioned above. Use
caution when driving this evening. Roads will change from wet or
dry, to snow and ice covered in a relatively short distance.

As the showers diminish over west-central Montana this evening,
another piece of energy sliding south out of Alberta will initiate
periods of moderate to heavy snow overnight to the Glacier region.
2 to 5 inches of snow is possible for lower elevation areas such
as West Glacier and Polebridge. The higher terrain, including US-2
from Essex to Marias Pass, should see 7 inches or more of
additional snow. So a Winter Weather Advisory has been issued
which goes in effect at 9PM MDT and ending at noon tomorrow.

Spring like weather will persist tomorrow and Tuesday with
slightly warmer temperatures and showers, especially across
northwest Montana and through the Clearwater Mountains in Idaho.
High pressure builds briefly over the area Wednesday, however
forecast models show that an increase in cloud cover and some
light precipitation will be possible ahead of the next approaching
weather system.

An approaching low pressure system on Thursday will push a
relatively strong cold front through western Montana and central
Idaho Thursday afternoon into Thursday night. Enough instability
will be present that fairly widespread showers will develop. There
is even the potential for even a few thunderstorms in the
afternoon, mainly across central Idaho into portions of west
central and southwest Montana. Snow levels will initially start at
around 5000 to 6000 feet Thursday afternoon, but drop to near the
valley floor by Friday morning. Accumulating snow will be
possible on mountain passes, which could cause a period of slower
travel Friday morning. Breezy conditions can also be expected
Thursday night into Friday as the front passes.

Cooler and unsettled conditions will continue into the weekend as
the low pressure system lingers over the region. Below normal
temperatures and periods of snow, even at times down into the
valleys, will be possible.


.AVIATION...Scattered snow showers will continue to impact KMSO
and KBTM through the evening hours, until around 19/0300Z. Little
further accumulations are expected, though visibility could be as
low as 1/2SM in the heavier showers. KGPI will see impacts due to
snow from a shortwave sliding south out of Alberta after 19/0600Z
tonight, with snow continuing into Monday morning. 1 to 2 inches
of snow will be possible for KGPI through tomorrow morning.


MT...Winter Weather Advisory from 9 PM this evening to noon MDT
     Monday West Glacier Region.


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