California's coastline is currently facing the brunt of winter's first massive swells, as an incoming atmospheric river storm is wreaking havoc and forcing evacuations due to flooding of beach and coastal roads. Marin County residents in several areas were ordered to temporarily evacuate on Thursday morning, while Santa Cruz County issued an evacuation warning for coastal areas near Seacliff State Beach. The National Weather Service has issued a coastal flood warning for the Bay Area, citing significant flooding of beach and coastal roads caused by large breaking waves.

In Marin County, residents in the Calles Pinos, Pradero, Sierra, Onda Resaca, Ribera, and Embarcadero areas, along with Calle de Arroyo, were instructed to evacuate due to the high risk of wave damage and coastal flooding. The Stinson Beach Community Center was designated as the evacuation point. Similarly, in Santa Cruz County, an evacuation warning was issued for coastal areas near Seacliff State Beach.

The Rio del Mar Esplanade, a popular tourist spot within the evacuation area, is currently flooded with several inches of storm water. The California Highway Patrol has urged residents to avoid the area and not attempt to drive across or through it. The waves, which can reach up to 40 feet in some locations along the San Francisco Bay Area coast, have caused significant road closures and deposited large amounts of debris.

Southern California is also experiencing high surf, although the waves are not expected to be as large. In Ventura County, waves up to 12 feet have already been reported, while the Central Coast has witnessed swells ranging from 18 to 20 feet. Residents in a beachside community in Ventura watched as waves washed away trash bins and sent foaming seawater streaming into neighborhood streets.

A high surf advisory has been issued for Point Conception in Santa Barbara County and beaches in Hermosa Beach, Manhattan Beach, and Palos Verdes Peninsula in Los Angeles County. Sets of 15- to 20-foot waves and dangerous rip currents are expected in these areas.

The National Weather Service has cautioned the public to stay away from rocks, jetties, piers, and other waterside infrastructure. While no structural or road damage is anticipated, there is an increased risk of drowning due to rip currents and injuries caused by large breaking waves. The agency stressed the importance of never turning one's back to the ocean in these conditions.

As for the weather forecast, the next few days in California will be overcast, with light rain expected later in the week. The timing of a New Year's Day storm remains uncertain. Additionally, waves are expected to intensify again on Saturday with the arrival of higher swells.

The National Weather Service has also issued a coastal flood advisory, which will remain in effect until 10 p.m. Saturday. Although no structural or road damage is predicted, the risk of drowning is heightened. Swimmers and surfers should be cautious of rip currents, and the public is advised to avoid beaches and rocks. Small boat owners should also be vigilant as large waves can capsize vessels.

The storms currently impacting California's coastline are a result of strong storms over the Pacific Ocean. These storms generate strong winds, which produce the massive waves that propagate towards the coast.

While the waves continue to batter the coastline, the Los Angeles County area is not expected to see compounding effects from rainfall until early Saturday, with light showers continuing throughout the day. There is a 30% to 40% chance of rain on Sunday into Monday, but it will be in the form of light showers.

As the severe weather conditions persist, residents are urged to stay updated on official advisories and take necessary precautions to ensure their safety during this period of challenging environmental conditions.