What makes storm a nor’easter? What’s an atmospheric river?

The Associated Press

A winter storm carrying heavy, wet snow — a true nor’easter — battered parts of the northeastern U.S. on Tuesday. Meanwhile, the latest in a string of atmospheric rivers dumped more moisture on California, a state where crippling drought has given way to a series of deluging and damaging rain events. A nor’easter is the term used by the National Weather Service for storms that either exit or move north along the East Coast, producing winds blowing from the northeast. And an atmospheric river is a long and wide plume of moisture that forms over an ocean and flows through the sky over land.