The term air mass is used frequently by meteorologists. By definition an air mass is a large volume of air that has similar properties. Those properties would include temperature and often moisture content. These air masses will develop certain characteristics over the course of many days or weeks by remaining in a certain geographic regions.
In the winter, the far northern latitudes receive little or no sunlight allowing the air in these areas to become increasingly cold. Plus, because the nearby moisture source, theArctic Ocean, is frozen over, the air also becomes very dry. Although the term Arctic is frequently used when colder air moves in, most of our colder air masses locally originate in centralCanadaand not in areas above theArctic Circle.
Therefore, by definition many of our cold snaps in the winter should be referred to as a polar air mass, notArctic. Although, the air mass the moved through a couple of days ago was of true Arctic origins originating in Siberia and interiorAlaska.