Giant Waves and Rain Forecast for California Coast

Rain, coastal flooding and waves as tall as 30 feet were expected along parts of the West Coast on Friday, a day after giant waves pummeled the California shoreline and prompted some evacuation warnings.

More than six million people in coastal areas of California and Oregon were under high surf warnings overnight as breaking waves posed an “especially heightened threat to life and property,” according to the National Weather Service.

“Dangerously large” waves about 28 to 33 feet tall, and potentially up to 40 feet tall, were forecast overnight in some coastal spots in the San Francisco Bay Area and for some parts of Central California, where a few communities in Santa Cruz County had received evacuation warnings a day earlier.

A high surf warning for the Bay Area and the Central Coast expired at 3 a.m. local time. But a high surf advisory, indicating a lower level of risk, along with a coastal flood advisory, were scheduled to last for several more hours.

Separately, a high surf warning was set to remain in effect through Saturday for more than four million people along the coasts of Oregon and California. The Weather Service office in Medford, Ore., said that it expected infrastructure damage and beach erosion from breaking waves up to 30 feet tall.

In Southern California, forecasters predicted waves of up to 25 feet, and said that the threat of significant coastal flooding would last into Saturday night. For beaches in San Luis Obispo and Santa Barbara counties, northwest of Los Angeles, high surf and coastal flood warnings were in effect through 10 p.m. on Saturday. (A coastal flood warning is a notch higher than an advisory and indicates an imminent or likely threat to life and property.)

The Weather Service office in Los Angeles told surfers and beachgoers that the risk of drowning was high, and the California state parks system warned outdoor enthusiasts to be careful at the ocean. More than a dozen state parks and beaches in California were fully or partially closed because of bad weather.

The large waves were part of a storm system that was approaching the West Coast early Friday. The Weather Service said in a forecast that moderate rainfall, becoming heavy in some places, was likely for much of California later in the day. A foot or two of snow was also possible in the Sierra Nevada by Saturday night.

Some coastal areas of California, Oregon and Washington State were also under a gale warning until late Friday night, meaning that wind gusts of 39 to 54 miles per hour were imminent or already occurring.

There is evidence that the United States can expect more unusual and severe storms as the planet heats up, potentially striking in new places or at unexpected times of year.

Last winter brought some of the most ferocious weather that California had seen in decades, including many atmospheric rivers — narrow conveyor belts of water vapor in the sky — that dumped wave after wave of precipitation onto already soaking ground.

The National Oceanic and Atmospheric Administration said in October that it expected conditions to be wetter than average across much of California this winter, partly because of the weather phenomenon El Niño.