California storm updates: 'This storm continues … take precautions,' mayor warns

A storm system continues to slam Southern California, with an atmospheric river bringing a plume of moisture all the way from the tropical Pacific Ocean.

The National Weather Service has flood watches in effect Tuesday morning for California as well as Nevada and Arizona. Winter storm warnings and snow alerts were also in effect for nine western states, from Montana to California, as this storm spreads into the Rocky Mountains.

As of early Tuesday, up to 3 feet of snow had already fallen on the Sierra Nevada mountain range.

The threat of flash floods on Tuesday will be mostly from Los Angeles to San Diego in California and from Yuma to Phoenix in Arizona. Locally, less than 1 inch of rain is in the forecast for Los Angeles, but the foothills around the city could get an additional 1 to 2 inches of rain.

On Wednesday, another storm system -- much weaker -- is expected to move through California from the San Francisco Bay Area to Los Angeles by the evening hours. The storm could dump an additional 1 inch of rain on southern California.

-ABC News' Max Golembo

President Joe Biden told California Gov. Gavin Newsom and Los Angeles Mayor Karen Bass he is committed to helping communities impacted by the monster storms with "any and all federal support requested."

Los Angeles Fire Department personnel rescued a man and his dog from the Los Angeles River Monday.

Around 2:45 p.m. PT, authorities received a report from a bystander that a man had jumped into the water to rescue his dog. Fire crews responded and found that the dog had managed to swim to the edge and escape the rapids.

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Firefighters rescue man who was trying to save dog from rushing water

Los Angeles firefighters rescued a man who got caught in fast-moving water while trying to save his dog.

The LAFD Air Operations lowered a rescuer into the water and they were able to grab the man, who was still conscious. They were hoisted into the aircraft, LAFD said, and the patient was taken to a local hospital.

The dog was taken to a shelter for temporary care.

At a press conference Monday night, officials said LA County Fire had rescued 16 people from flooding conditions and five cats.

-ABC News' Marilyn Heck

A flash flood warning that covers the Los Angeles-area cities of Glendale, Pasadena and Santa Clarita has been extended until 6 p.m. local time.

A flood advisory covering all of LA County is in effect until 3 p.m. local time.