SAN FRANCISCO, Calif. (KGO) -- The Bay Area is preparing for some heavy rain over the weekend, but what is propelling it?
Meteorologist Drew Tuma breaks down what creates the Atmospheric River and what impact it will have on the storm systems arriving this weekend that will moisture fueled by the Atmospheric River.
Watch the video in the player above to learn about the phenomenon that can dump snow and create strong storms.
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STORMWATCH: What is an Atmospheric River?