HALF MOON BAY (CBS SF) — Flood waters flowed down Corral Reef Ave. in El Granada after a potent winter storm front roared through the San Mateo County coastline Thursday morning, quickly dumping more than an inch of rain during an intense downpour.

The National Weather Service issued a flood advisory for the area.

“Some low-water crossings may become impassable,” the weather service warned. “Ponding of water in urban or other areas is occurring or is imminent.”

“The public and local law enforcement reported ongoing flooding especially locations such as Moss Beach and Millbrae,” forecasters continued.

“Talking to some of the long-term coastside residents, they haven’t seen that kind of flooding in that area since 1982,” Coastside Fire Protection District battalion chief David Hibdon told KPIX.

“It was unexpected, it was a lot more rain than usual,” said Pierre Mugnier, who lives near one of the flooded locations.

San Mateo County provided two sand bag stations to help residents prepare for the rain expected through the weekend. Firefighters say the soil is oversaturated from all the recent precipitation and can’t absorb much more rain, contributing to the flooding.

“They still have the ‘flooded’ signs up but I don’t see as much water as I saw this morning,” said Peg Vaughn, who visited the convenience store off California Ave. hours after the street in front of it flooded. “It’s quite crazy and, as you can see, it’s quite muddy.”

At one point, authorities guided drivers single file on Highway 1 next to the Half Moon Bay Airport.

San Mateo County parks officials posted that the entire Sawyer Camp segment of the Crystal Springs Regional Trail was closed due to flooding.

The fire protection district asked that neighbors make sure their homes are ready to handle the additional rain and help avoid additional flooding.

“If you live in a neighborhood with drains, get together with your neighbors and make sure you guys keep those clean,” said Hibdon. “Just to be prepared, it’s good to be prepared, cause you never know what’s gonna happen.”

© Copyright 2021 CBS Broadcasting Inc. All Rights Reserved. KPIX 5’s Shawn Chitnis contributed to this report