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Area forecast discussion
National Weather Service Missoula Montana
230 PM MST Mon Jan 22 2018

Discussion...a moist and unstable atmosphere will continue to
support scattered snow showers over north central Idaho and
western Montana this evening and tonight. A few of these showers
may organize temporarily into bands and produce isolated areas up
to one inch in the valleys (mainly between Kalispell and darby)
in the evening. In addition, Lolo and lost trail passes should see
another 2 to 3 inches this evening. As such, roads will vary from
clear and dry most areas to pockets with snow cover and be watchful.

Weak high pressure and dry condition should return Tuesday

Snow showers will begin to move west across the Idaho Panhandle
into Lincoln County, Montana by Tuesday evening. This area of showers
will extend southward through much of Idaho and Clearwater
counties of Idaho through the night, making a slow progression
eastward across the rest of western Montana during the day
Wednesday. Mountain snow will continue through at least Wednesday
night, causing a prolonged period of light to moderate snow to
steadily accumulate in terrain above 4000 feet. As a result, those
traveling over lookout, Lolo, or Marias Pass should expect
changeable conditions and periodically low visibility.

Snow that falls in valleys Tuesday night through Wednesday morning
will transition to rain, or a sloppy rain/snow mix, by Wednesday
afternoon across all of central Idaho and western Montana. Snow levels
will rise to about 5000 feet Wednesday, then lower back down to
valley floors by Thursday morning. Rain will then change back to
snow by Thursday morning, with lingering widespread snow showers
persisting thereafter. Additional snow accumulations of a few
inches are possible through Friday. All in all, Tuesday through
Friday will be quite the "weather rollercoaster".

The main storm track may shift a bit northward (still some
uncertainty on how much) Saturday and Sunday. As this occurs,
slightly warmer air will slowly work northward. However,
considerable moisture should channel across north central Idaho
and mainly northwest Montana. Snow levels should start out near
valley floors and raise slowly over the weekend to near pass

In the longer term, models are fairly consistent showing another
cold and moist trough of low pressure affecting the northern
rockies, with another round of wintry precipitation next week.

The bottom line is: a quite moist weather pattern is expected for
the next 7 to 10 days with mountains picking up significant
amounts of additional snow and valleys going back and forth from
rain and snow.


Aviation...a moist and unstable atmosphere will linger over the
northern rockies this evening and tonight with scattered snow
showers. Under the snow showers, low ceiling and visibilities with
terrain obscurations can be expected. Kmso, kgpi and kbtm will be
the airports most impacted by possible snow showers into tonight.


Mso watches/warnings/advisories...

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