Backdoor cold front
A backdoor cold front, or backdoor front, is a cold front moving south or southwest along the northeast of the Atlantic seaboard in North America, particularly in the Northeastern United States and the Great Lakes. Typically occurring in spring, the front drives cool Atlantic air from the east or northeast into northeastern US that supersedes the warmer continental air. The front is termed "backdoor" because it arrives from the east, meaning it originates from the opposite direction of a typical cold front and therefore comes through the region's "back door." Formation A backdoor cold front occurs when the clockwise motion around a high-pressure system pulls in colder air toward the south and west of it. This is where a synoptic wind motion creates a wind flow from the cool North Atlantic Ocean that brings in the backdoor front. A cold front, however, approaches from the north, northwest or west, and its wind direction will generally be from those directions (since most weather moves west to east), except this does not happen with a backdoor cold front. Rather, a back door cold front arrives from a particular direction, where it will move in an opposite direction, unlike a regular cold front.