A WIND CHILL WARNING in effect tonight through tomorrow morning for the following counties: Flathead, Sanders, Lake, Lincoln, Missoula, Mineral, Ravalli, Granite, Powell, Deer Lodge, and Silver Bow.
Strong winds above 20 mph may push wind chill values between -20° and -30°. In Southwest Montana values may reach towards -40°. Winds will remain between 15 and 25 miles an our in the Missoula and Flathead Valleys overnight. Winds will be lighter east of the divide, between 5 and 10 mph, but static air temperatures will be much colder.
With these cold conditions, frostbite and hypothermia will come quickly to people exposed outdoors. Frostbite can occur in these conditions in as little as 10 minutes. Livestock and pets should be moved inside or under shelter from the wind. If you must venture outside, make sure to cover exposed areas and keep extremities warm.
Additional snow is expected across the region today. This will mostly be a mountain event. However, light accumulations are possible in the valleys of southwest Montana. The snow will be very dry and powdery, and will primarily pose a visibility risk with blowing snow on Saturday.
With a fresh jolt of cold air across the region, the weekend will be the coldest it has been on average during this cold snap. It's likely that this will be the third or fourth coldest first ten days in December on record when it's all said and done. We will slowly warm up towards average temperatures next week, but our chance of snow will increase as well.