Valley temperatures to plummet overnight

How low will it go? Probably below zero, and then some.

Meteorologists at the National Weather Service in Missoula predict low temperatures in the Flathead Valley will dip to about minus 15 Thursday night, with even colder readings in some locations.

A shot of Arctic air was expected to descend from Canada across Northwest Montana on Wednesday night, lowering already cold temperatures another 10 to 15 degrees by Thursday morning.

Add in the wind, and conditions will be down right dangerous, the Weather Service warned.

A wild chill warning is in effect for the Flathead and Mission valleys through Thursday afternoon. Wind chill readings between minus 20 and minus 40 are likely, while an extreme wind chill reading of minus 50 to minus 60 is possible in places like Polebridge and the higher terrain of Glacier National Park.

Skiers should note that the upper mountain chair lifts at Whitefish Mountain Resort were closed Thursday, with a high temperature of minus 12 and a wind chill as low as minus 50 likely.

The wind chill is based on the rate of heat loss from exposed skin by the combination of wind and cold, the Weather Service explained. As wind increases, heat is carried away from the body at an accelerated rate, driving down the body temperature.

People are advised to cover all exposed skin when heading outside during these frigid conditions. Dangerously cold wind chills could cause frostbite on exposed skin in as little as 5 to 10 minutes. Pets and livestock should also be protected from extreme cold exposure, the Weather Service warned.

Overnight lows will remain below zero on Friday and Saturday.

The Arctic air is expected to back out of the area by Sunday, with more seasonable high temperatures in the 20s returning for President's Day.