Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 242037

Area Forecast Discussion
National Weather Service Missoula MT
237 PM MDT Mon Apr 24 2017

.DISCUSSION...The Northern Rockies continue to be cool and showery
for the next 24 to 48 hours. The best shower activity will be
during the afternoon and evening as the atmosphere becomes
unstable. A minor threat of lightning exists this afternoon across
southwest Montana, while tomorrow lightning might be possible east
of Highway 93. Temperatures continue to be around 5 degrees below
normal for this time of year.

Still expecting a Pacific trough on Wednesday, so there will be a high
chance for precipitation throughout the day. Snow levels will fall
from 6000 feet down to 2500 feet by Thursday morning. Expect high
temperatures to be 5 to 10 degrees below normal. A few inches of
snow are possible at mountain passes Wednesday night into Thursday
morning which could be a surprise to those traveling on I-90,
US-12, US-2 at Marias Pass or US-93.

Highs on Thursday will struggle to get out of the 40s in some
places which would equate to 10 to 16 degrees below normal. We`ll
be under a broad scale trough which will cause numerous rain and
snow showers. Also it could be quite breezy by Thursday afternoon
across southwest Montana making it feel close to wintry-like.(ie.
in Butte, it could be cloudy with snow showers at times,
temperatures in the upper 30s with gusty winds to 25 mph).
Thursday night there will be another round of snow for area passes
especially along the Continental Divide including Marias Pass and
also along the Idaho and Montana border.

After starting the morning off with snow at mountain passes, Friday
will continue to be cloudy with showers and colder than normal,
although it will be less breezy. On Friday night, a shortwave
ridge will move over the region allowing for more stable
conditions to develop, but there will continue to be a chance for
a few mountain showers across southwest Montana and Lemhi County.
Temperatures will generally cool towards freezing across western
Montana and central Idaho valleys (high valleys will be in the

On Saturday an upper level disturbance will help to trigger mainly
mountain showers in the afternoon, while valley locations may be
able to stay dry for much of the day. It could turn out to be a
pleasant day with patches of sunshine and temperatures in the 50s
in the valleys (which is still 5 to 8 degrees below normal).

There are discrepancies in model solutions for precipitation Sunday
so confidence is low. Confidence is good that temperatures will
be slightly below normal.

For early next week, it still looks like the stationary upper
level ridge over the eastern Pacific (west of California) doesn`t
want to budge. This means that we will start the month of May
with at least one or two cool and moist Pacific weather systems.
There is one ray of hope for drier and milder weather as ensemble
modeling systems are hinting at a possible upper ridge by mid to
late week next week, but confidence of course is low.


.AVIATION...Unstable atmosphere this afternoon will allow for an
increase of showers activity across the Northern Rockies. These
showers will be capable of producing low ceilings and visibility.
The mountains around the region will be obscured at times. The
terminals could potentially be hit by a shower which would reduce
flight categories to MVFR for a brief period. The shower activity
will decrease during the overnight hours.



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