A very cold air mass will penetrate the Northwest this weekend, and it willremain extremely cold into next week. Montana will feel the worst of it withtemperatures dropping into the teens and single digits Sunday, then subzeroweather is likely at night.Washington, Oregon and Idaho will also feel the sting of this bone-chilling airmass. In Spokane, for instance, highs will be in the middle 20s Sunday andMonday, and overnight lows will be in the single digits. The cold pockets ofeastern Washington, eastern Oregon and northern Idaho will drop below zero bothSunday and Monday nights.

The invasion of cold air will not trigger a snowstorm, but light amounts ofsnow are expected from Alberta to Wyoming.

Story By AccuWeather.com Senior Meteorologist John Kocet.