Watch: Ice jam flows down New York river

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Cameras monitoring the Au Sable River in Au Sable Forks, New York captured an ice jam Friday afternoon. 

The U.S. National Weather Service in Burlington, Vermont released time-lapse video of the river rising, filling with ice, and then falling. 

The video starts at noon (17:00Z) and goes to 3 p.m. (20:00Z).

"This is why we urge caution around rivers when ice jams may occur. They happen fast!" the National Weather Service posted with the video on its Facebook page.

The river's stage gained about a half-foot during that time.

Ice jams occur when river water freezes into a dam and then breaks away, releasing massive blocks of ice and the water behind.