Over a month’s worth of rain, hurricane-force wind gusts and feet of mountain snow are coming to parts of the Pacific Northwest and Northern California.

An atmospheric river and bomb cyclone are what make this storm so powerful — but what do those terms mean? What is an atmospheric river? Atmospheric rivers are no strangers to the western U.S., especially during the fall and winter months.

While atmospheric rivers and bomb cyclones can bring intense precipitation and strong winds, they are distinct meteorological phenomena with different implications for weather patterns.