MISSOULA — Very mild air remains in place over the northern Rockies Monday. High temperatures will top out in the 40s with even some low 50s possible for areas in the Bitterroot Valley. Polson is another location that could reach the 50 degree mark by the afternoon. Expect sunshine during the morning with increasing clouds by the afternoon.
A weak cold front will bring slightly cooler temperatures along with scattered mountain snow and valley rain/snow showers Tuesday. No snow accumulation is expected in the valleys during the day Tuesday as highs again top out in the low to mid 40s.
The best chance to see some minor valley snow accumulation will be Tuesday night into Wednesday morning in west-central and southwest Montana. Lingering precipitation along with cooler temperatures may allow for light snow to make it down to valley floors during this time. With that being said snow amounts will generally stay around half an inch or less.
For the end of the week and weekend, a cold arctic air mass will move south on the east side of the Continental Divide. This cold air mass looks to bring the coldest air of the winter season to the mid-west and northern plains (Dakotas, Minnesota, Wisconsin, Michigan). The further west you travel the more this cold air looks to moderate.
For locations in Montana east of the divide, highs will stay in the 40s through Thursday then take a quick drop into the teens and 20s by Friday and continue into Saturday before warming back into the 30s Sunday.
For us here west of the divide, the main question is how far west will this cold air travel? Right now, the cold air looks to spill into northwest Montana by Saturday with highs only topping out in the 20s for areas from the Flathead Valley east. All other locations look to see highs fall into the low to mid 30s by Saturday.
After this, models have us potentially seeing a warm up Sunday (mid 30s to low 40s) as the cold air retreats back to the east side of the divide, before moving west again as we move into next week. Basically, a lot of uncertainty with this forecast. Stay tuned for updates as we move through the week.