textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Cool, wet weather with winter storm along the Continental Divide continues through the weekend.

- Hard freeze in valleys of western Montana early this week.

- Warming up to above average conditions in the long term.

The upper level low over the Pacific northwest continues to pump moisture up from the south where it interacts with a cold air mass from the north today. The main area where the two air masses collide is along the Continental Divide, and there's a broad area of winter storm warnings and winter weather advisories many miles either side of the Continental Divide as a result. Overnight snow started accumulating on roadways in the mountains and even some lower elevation areas like Garrison Junction. The further west, the weaker the interaction and the less moisture to work with, and in the valleys of central Idaho there has been little to no impact from this system.

East winds along the Continental Divide are also causing impacts. As the cold air spills over the mountains and accelerates down hill it has been causing frequent gusts around 40 mph on the east shores of Flathead Lake and Badrock Canyon. Those conditions are expected to continue today, but to a lesser extent as the valleys of western Montana start to fill up with colder air.

Much colder air will be in the place over the region once the upper level low moves out of the region early this week. As a result, many locations in western Montana will cool into the low 20s and a few of the typically colder spots down into the teens Monday through Wednesday mornings. In central Idaho, conditions will be more mild with valleys cooling into the 30s and low 40s.

Ensembles still agree well on a ridge building in quickly mid to late next week, and as a result by the end of the week afternoon temperatures will be above average again. However, due to a drier air mass in place at that time and longer nights, we do expect cold mornings to continue through the week.

AVIATION

Low ceilings and poor visibility are in the region due to a stream of moisture from the south interacting with a cold air mass from the north over our region. Most of the action is along the Continental Divide, and terminal KBTM will be impacted the most. Other area terminals, especially KGPI will continue to see elevated east winds through today. Snow is unlikely but possible at KGPI and KMSO, however, lower expected snow rates and a warm ground mean little to no impact is expected as the snow will melt quickly once it falls, if it falls at those terminals at all. Mountain obscurations due to the low cloud cover will last through the weekend.

MSO WATCHES/WARNINGS/ADVISORIES

MT...Winter Weather Advisory until 6 AM MDT Monday for Bitterroot/Sapphire Mountains...Potomac/Seeley Lake Region...West Glacier Region.

Wind Advisory until 3 PM MDT this afternoon for Flathead/Mission Valleys.

Winter Storm Warning until 6 AM MDT Monday for Butte/Blackfoot Region.

ID...None.