MISSOULA - Very cold with heavy snow this week.
Arctic air is in northwest Montana Monday and Tuesday. This will slide south into west-central and southwest Montana Wednesday - Friday. Highs during this time will be below zero or in the single digits. The coldest air will be Wednesday night into Thursday morning. Expect temperatures to drop to around 20-30 below zero for all of western Montana. Locations further east (Seeley Lake, Glacier, Philipsburg, Deer Lodge) could drop to 40 below zero. Wind chills will be even colder!
Light snow develops Monday night and continues through Tuesday. Snow will then pick up with heavy snow possible Tuesday afternoon into early Wednesday morning. Right now the heaviest snow looks to be across northwest Montana with snow amounts ranging from 6"-to-12". Higher amounts could develop along the Montana/Idaho border (Libby, Trout Creek, Thompson Falls, St. Regis).
For west-central and southwest Montana, a dry pocket of air looks to develop for the Bitterroot/Missoula Valley Tuesday morning through evening. If this does set up, this will lead to light snow amounts before snow picks up Tuesday night into Wednesday. Right now snow amounts of 2" to 5" looks likely.
Warmer temperatures but active weather sets up for the Christmas weekend. The source of the moisture will be coming from the Pacific Ocean. This means mountains could continue to see heavy snow while valleys see snow, rain/snow, rain or freezing rain. We'll update this as we first get through the beginning of this week.