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Atmospheric river brings record rains to Northwest

A satellite image shows how water gets channeled into a stream of moisture flowing toward the Northwest
A satellite image shows how water gets channeled into a stream of moisture flowing toward the Northwest

What happens when a river runs into a mountain?

An atmospheric river, carrying dense clouds of moisture from the tropical Pacific, has been colliding with our mountains, and all that moisture has been dropping like a waterfall.

"Virtually every one of our flood events or record-setting daily rainfall events is associated with an atmospheric river," says KPLU weather expert Cliff Mass.

On Thursday, many cities across Washington set all-time records for rain that day. And this March is sure to be in the top-10 for overall rainfall. Mass says Seattle will end up double what it typically gets for the month.

Mass explains how this all works, in his weekly weather conversation.

Despite a partial break today, it looks like that atmospheric river will keep flowing our direction for at least another week. Mass is predicting light but steady rain on Saturday, and another storm arriving on Sunday afternoon or evening.

The weekly KPLU feature "Weather with Cliff Mass" airs every Friday at 9 a.m. immediately following BirdNote, and repeats twice on Friday afternoons during All Things Considered. The feature is hosted by KPLU’s Science and Health reporter Keith Seinfeld. Cliff Mass is a University of Washington Professor of Atmospheric Sciences and renowned Seattle weather prognosticator. You can also subscribe to a podcast of this and previous "Weather with Cliff Mass" shows.

Keith Seinfeld is a former KNKX/KPLU reporter who covered health, science and the environment over his 17 years with the station. He also served as assistant news director. Prior to KLPU, he was a staff reporter at The Seattle Times and The News Tribune in Tacoma and a freelance writer-producer. His work has been honored by the American Association for the Advancement of Science (AAAS) and the Knight Science Journalism Fellowships at Massachusetts Institute of Technology.