The biggest storm in two years was on track to inundate the Bay Area with heavy rain and high winds Sunday, sparking some relief from drought-weary residents and a slew of stern emergency warnings for those living near wildfire burn scars.

Across Northern California, meteorologists and county officials told residents to prepare for flash flooding, downed power lines and possible life-threatening mudslides in places that have yet to recover from wildfires — even as they cheered the prospect of badly needed rain across the region.

“If we don’t have too much in terms of flash or nuisance flooding, this could be a pretty good win in terms of making up some of that rainfall,” said Brayden Murdock, a National Weather Service meteorologist.

The weekend forecast showed a slight slowdown of the system’s intensity compared to predictions earlier in the week, but the basic outcome was the same: “The first significant, significant rain that many places have seen since January,” Murdock said.

Starting late Saturday afternoon, the category 5 storm — the most severe on the scale of 1 to 5 — was expected to douse the North Bay hills with up to 10 inches of rain. As the system travels south, San Francisco could see 3-4 inches, with up to 8 inches at the top of Mount Tamalpais and other points of high elevation. San Jose and most of the East Bay, including eastern Contra Costa County and the Diablo Range, were forecast to see the least downpour with about 1-2 inches total.

Bay Area storm: Map shows where the rain is now.

For thousands of residents from Santa Cruz to Sacramento, the combination of sudden rainfall and ashy buildup within wildfire burn scars could create dangerous debris flows and mudslides, officials warned. The National Weather Service issued a flash flooding warning starting at 5 a.m. Sunday in the North Bay, 1 p.m. in the Santa Cruz Mountains and 5 p.m. in Monterey County.

MOUNTAIN VIEW, CALIF. – OCT. 23: A mackerel sky spreads over Mountain View, Calif., Saturday morning, Oct. 23, 2021, during a short break in the string of storms hitting California this week. (Karl Mondon/Bay Area News Group) 

In Santa Cruz County, where the CZU Complex Fire burned last August, the sheriff’s officeissued evacuation orders starting at 8 a.m. Sunday to residents near Año Nuevo State Park, Swanton and Ben Lomond.

A spokesperson for utility Pacific Gas & Electric said that field personnel will monitor for potential mudslides near the River, McFarland, Caldor, Dixie, Monument, Glass, Kincade and CZU burn zones, while the utility also plans to stage about 350 distribution crews and more than 200 inspectors to manage possible power outages.

Even in places without active burn scars, preparation was well underway Saturday to prevent urban flooding and protect vulnerable residents from the worst of the downpour. In San Francisco, outreach teams worked to alert unhoused people to a pop-up shelter open at the Moscone Center Sunday and Monday. Public works and utility workers have meanwhile been delivering sandbags to low-lying areas, including in the Mission District, and putting up flood barriers, said Department of Emergency Management Executive Director Mary Ellen Carroll.

In San Jose and Oakland, residents took advantage of the cool, sunny weather Saturday to stock up at sand bag giveaways.

“I feel pretty confident that we’re doing everything we can to mitigate as much impact as we can — but there’s little we can do once a certain amount of rain comes in such a short amount of time,” Carroll said.

OAKLAND, CA – OCTOBER 23: John Wessenberg picks up sandbags at the Drainage Services Facility in Oakland, Calif., on Saturday, Oct. 23, 2021. The National Weather Service issued a flash flood watch as powerful storms with heavy rains and gusty winds are expected to hit the Bay Area on Saturday night and Sunday. (Ray Chavez/Bay Area News Group) 

California Highway Patrol Officer Ross Lee said that the office did not plan to staff up more than usual due to the storm, but urged residents to drive slow and leave extra room between cars, particularly on winding mountain roads such as Highway 17 and along flat stretches of Highway 101 and Interstate 280, where standing water may build up and cause cars to hydroplane.

“You get into a level of familiarity or comfort in your daily routine, but in a situation where we have bad, inclement weather, it’s incumbent that we give ourselves a little extra time and understand that the weather can change that road,” Lee said.

Despite the possible risks, some Bay Area residents waited for the storm with a mix of trepidation and excitement. In Oakland, Myra Wheeler walked around Lake Merritt with her chihuahua, ChaCha, during the last hours of rain-free weather.

“I usually like to come out here and take a walk when it’s rainy,” Wheeler said, motioning toward the lake. “But not this evening.”

The impending rain meant several more hours on the job for Micah Vassau, who planned to “batten down the hatches” at his construction site, putting up a tarp and hauling equipment inside. He couldn’t remember the last time it poured heavily in the East Bay.

“I hate the winter,” he said, “but I love the rain.”

OAKLAND, CA – OCTOBER 23: Alec Rosenberg picks up sandbags at the Drainage Services Facility in Oakland, Calif., on Saturday, Oct. 23, 2021. The National Weather Service issued a flash flood watch as powerful storms with heavy rains and gusty winds are expected to hit the Bay Area on Saturday night and Sunday. (Ray Chavez/Bay Area News Group)