Tens of thousands of homes in Washington state lost power Tuesday and downed wires or trees locked some highways as Northern California and the Pacific Northwest started feeling the effects of a powerful atmospheric river event,

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 is a narrow band of wind that carries immense plumes of moisture, spanning hundreds or even thousands of miles, resembling a vast river in the sky. NBC News' Chase Cain reports on the challenges this phenomenon poses for the West Coast.