SAN FRANCISCO (CBS SF) — With 18-to-24 foot waves crashing along the northwest facing beaches along the coast early Thursday, forecasters warned San Francisco Bay Area holiday beachgoers to “stay off rocks and coastal jetties.”

The National Weather Service has issued a high surf advisory until late Thursday with waves as high as 24 feet.

“Currently coastal buoys report 13 to 15 foot waves with a 16 to 17 second period,” NWS forecasters said. “This could produce breakers of 18 to 24 feet with largest breaking waves at northwest facing beaches… It is recommended that individuals stay off rocks and coastal jetties if visiting the coastline and remain vigilant of their surroundings until a safe distance from the coast.”

Waves at the legendary big-wave surf spot Mavericks off the coast from Half Moon Bay could see waves up to 28 feet, according to the San Francisco Chronicle.

Among the areas most exposed to the northwest swells are San Francisco’s Ocean Beach; San Mateo County’s Montara State Beach; Monterey County’s Marina State Beach and Monastery Beach in Carmel.

“These large waves can be erratic and unpredictable and may injure or knock beachgoers into the cold, turbulent ocean,” forecasters warned.

While the swells were good news for surfers, they also have triggered warnings for holiday beachgoers and fishermen to be on the alert for rip currents and potentially deadly sneaker waves.

“These large waves can be erratic and unpredictable and may injure or knock beachgoers into the cold, turbulent ocean,” NWS forecasters warned.

“Rip currents can pull swimmers and surfers out to sea. Large breaking waves can cause injury, wash people off beaches and rocks, and capsize small boats near shore.”

If you do find yourself in a rip current, officials said swimmers “should swim parallel to the coast to escape the rip current before trying to swim for shore.”