Siberian Express is a shorthand meteorological term in the United States describing the arrival of an extremely cold air mass of Arctic origins. It does not necessarily refer to an origin in Siberia. The term is most commonly employed by the news media when such a frigid air mass moves into areas where it is relatively unusual, such as the Deep South or Eastern Seaboard of the United States. Meteorologically, it is typically associated with a phenomenon called the Pacific-North American teleconnection pattern (PNA).