Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 222138

Area Forecast Discussion
National Weather Service Missoula MT
238 PM MST Wed Feb 22 2017


Periodic snow shower activity will exist over the Northern Rockies
through the end of the week. For much of the region, snow shower
activity will by maximized during afternoon heating. Convection
aside, subtle features in the upper level pattern will lead to
limited snow impacts to roads, mainly over mountain passes.
However, the Camas Prairie of Idaho, Lemhi County in Idaho, and
southwest Montana appear to have favorable patterns for snow
accumulations causing travel impacts for populated areas (e.g.,
Grangeville, Salmon, Butte) through Thursday. Temperatures will
slowly cool over time, particularly by Friday, when overnight
radiation cools valley locations down to the teens and single

Friday night into Saturday, a low pressure system will slide down
the West Coast. Although the main system will be well to our
west, snow showers will increase in coverage across the Northern
Rockies during this timeframe as the trough axis moves overhead.
This system will bring cool east winds, which will cause weekend
temperatures to run about 10 to 15 degrees below normal. Given
these cold temperatures, all showers are expected to be snow

On Sunday night into Monday, a second similar system slides south
along the same track. This system looks to bring more widespread
snow to the Northern Rockies, and accumulations of a few inches
look possible for valleys, although details are still hazy, given
model inconsistency.

From Tuesday through late next week, a northwest flow pattern
keeps temperatures below normal, but slowly moderating, with
daily chances for showers, especially during afternoons.
Confidence remains low in any push of colder arctic air past the
day 7 forecast, with some models now keeping colder air well to
the east.



Snow showers will be present over the Northern Rockies air space
during the next 24 hours. KBTM will experience the most disruption
from snow, producing decreased ceilings and visibility 22/2100Z
through 23/0500Z, and then again 23/1000Z through 23/1800Z. KMSO
will experience numerous snow showers moving past the terminal;
however, there is a low probability of prolonged snow occurring
right at the terminal. KSMN and KGPI have marginal chances of
snow showers near their respective terminals. Occasional terrain
obscurations will exist associated with snow showers.



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