Storm batters Big Sur coast; Isolated thunderstorms possible in Bay Area Monday

BIG SUR -- A rare September weather front battered the Big Sur coast line over the weekend, which triggered some flooding, and shut down Highway 1 after the storm spewed debris onto the popular coastal roadway.

According to Caltrans, flooding shutdown northbound Highway 1 overnight at Ragged Point while southbound traffic was being held at Point Lobos at least until 8 a.m.

The National Weather Service said that during height of the storm on Sunday the intense downpours were "lining up almost perpendicular to the coastal hills of Big Sur, leading to enhanced precipitation rates on a very localized scale."

"This narrow strip of heavy rain produced anywhere from 0.5 to 2 inches of rain along Highway 1 from Big Sur up to Watsonville in a 2-3 hour timeframe," the weather service said.

 A Flood Advisory expired Monday morning but not before the weather service got reports of "localized minor flooding on the Monterey Peninsula."

In the Bay Area, the storm front dumped some impressive totals over the last 24 hours, particularly in the Santa Cruz Mountains where Ben Lomond got 1.97 inches and Los Gatos 1.05.

The weather service tweeted the totals were "more like spring or late fall rainfall amounts."

Elsewhere, St. Helena has gotten 1.20 inches, Angwin 1.44, Mt. Diablo 1.75, Anderson Reservoir 1.34 and San Francisco 0.33 of an inch.

While the totals neared record levels in some locations, it fell far short in San Francisco. The record for the 18th came in 1959 with 2.01 inches of rain.

"While we can get rain in September, it is typically our third driest month," the weather service said. "Climate normals for September for the area ranges from 0.05 inches to 0.15 inches, so we have been seeing some areas(such as the coastal mountains) exceeding 1000% of September normals."

Here's a broad 24 hour rain total summary (from 3 AM Sunday to 3 AM Monday):

• North Bay Coastal Mountains: 2" to 3.5" 
• Santa Cruz Mountains: 1.5" to 2.2" 
• Big Sur/Santa Lucias: Varying greatly from 0.5" further inland to up to 3.75" near Mining Ridge. Most values along Highway 1 near Big Sur were around 1 to 2 inches.
• Bay Area: 0.1" to 0.8" with San Francisco Downtown reporting 0.33 inches, Oakland Museum reporting 0.15, and SJC reporting 0.52 inches.   

Meanwhile, snow and ice in the eastern Sierra Nevada led officials to close State Route 108 high up over the Sonora Pass, the California Department of Transportation said Sunday.

The 119-square-mile Mosquito Fire in the Sierra foothills northeast of Sacramento was 38% contained after downpours on Sunday, allowing sheriff's officials in two counties to lift or downgrade some evacuation orders. It's the state's largest wildfire of the year so far.

More rain was expected, which fire spokesman Scott McLean called a mixed blessing for firefighters.

"It did help a bit to stifle that aggressive fire," McLean said. "But we're going to have new safety issues now with all the mud that's out there. And the ground moisture could cause some of those damaged trees to fall over."

Lingering showers over the Mosquito Fire will increase the risk of ash and mud flows, the National Weather Service said.