Backdoor cold front

"[1][2] 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.

On occasion, that air can move south out of high pressure area in the Canadian Maritimes and southward down the New England coast or the northern states.

The high pressure system's clockwise flow directs cold moist air southward and westward into Northeast US.

They are mostly shallow, with much of the maritime air only reaching a few thousand feet aboveground and thus would rarely pass the over the Appalachian Mountains.

The clouds associated with the backdoor cold front stretch from southern Illinois to North Carolina.

[7] Back door cold fronts are common from southeast Canada to New Jersey, due to cool Atlantic water lingering near the coast in spring.