Arctic air will spread south over the Great Plains of the United States later this week and move into Colorado for the weekend. There are a couple things to know about arctic airmasses:

Arctic air masses back in from the northeast

Very small transition area means large temperature differences over a small area

Arctic air is shallow and can’t often push up over mountain passes into the mountain valleys

Mountain areas typically end up warmer than the plains

They can occasionally bring a brief round of flurries as they arrive

They are tough to completely scour our of the eastern plains and usually take an extra day from what computer models show