California Landslides During the ATmospheric River Storm Over the Last Four Month: Implications for California and the Sierra Nevada
SACRAMENTO, Calif. — Landslides of rock and mud closed roadways Friday across California as heavy rains kicked off what will be a series of storms poised to usher in the new year with downpours and potential flooding across much of the state and multiple feet of snow in the Sierra Nevada.
The atmospheric river storm, a long and wide plume of moisture pulled in from the Pacific Ocean, began sweeping across the northern part of the state Friday and was expected to bring more rain through Saturday, according to the National Weather Service in Sacramento.
There was a winter storm warning in effect for the upper elevations of the Sierra where as much as 5 feet of snow is possible at higher altitudes.
Northern California and the central California coast received 2 to 4 inches of rain over the last week. The cumulative effect of multiple Pacific storm systems with moist water from a river will make impacts like flash floods more likely.
Landslides already had closed routes in the San Francisco Bay Area, between Fremont and Sunol, as well as in Mendocino County near the unincorporated community of Piercy and in the Mendocino National Forest, where crews cleared debris into Friday night.
The earthquake in Humboldt County resulted in the beginning of flooding, according to the National Weather Service. A bridge that was temporarily closed last week due to earthquake damage may be closed again if the Eel River, which it crosses, gets too high, officials said.
The weather predictions have put the amount of rain expected in central and northern California in the 2 to 4 inch range.
The fire department in Sacramento was going to broadcast warnings about flooding from a helicopter and a boat along the American River, where many unhoused people live.
“Strong winds could cause tree damage and lead to power outages and high waves on Lake Tahoe may capsize small vessels,” the weather service in Reno said.
On the Sierra’s eastern front, flood watches and warnings continue into the weekend north and south of Reno, Nevada, where minor to moderate flooding was forecast along some rivers and streams into the weekend.
At Susanville, California about 85 miles (137 kilometers) north of Reno, the Susan River was forecast to rise from about 5 feet (1.5 meters) Friday to a foot (30 centimeters) above the flood stage of 12 feet (3.6 meters) by Saturday morning, causing moderate flooding that could affect some homes, roads and bridges, the National Weather Service said.
In Southern California, moderate-to-heavy rain was forecast for Saturday. On New Year’s Day, the region will dry out, and the Rose Parade in Pasadena will not be affected by rain.
US Highway 101, one of California’s most famous routes, is closed “indefinitely” as heavy precipitation and snow melt flooded roads, especially in the northern half of the state, officials said.
The roadway in South San Francisco had closed in both directions, officials from the California Highway Patrol had previously said. In an evening update, CHP added there was no estimated time of reopening as “water is not receding due to non-stop rainfall & high tides preventing the water to displace.”
There was a partial road closure of I-80 near the Nevadaline at noon on Saturday due to multiple spin outs. Driving through the mountain pass in the Sierra Nevada range has required tire chains for much of this month due to heavy snowfall.
Sacramento County Sheriff’s Office issued a state of emergency for flooding in the Wilton area during a strong storm Friday through Saturday. Flood warnings for northern California
A strong storm that brought a lot of heavy rain Friday through Saturday was causing a flood threat for a lot of Northern and Central California.
“Downtown San Francisco is now at 5.45 inches, just 9 hundredths of an inch away from the daily (midnight to midnight) record of 5.54 inches,” the National Weather Service said in a 5 p.m. update on Twitter.
Several small communities in northern California were under evacuation orders and warnings Saturday due to flooding. The communities of Paradise Park and Felton were ordered to evacuate due to the rising levels of the San Lorenzo River, while three other communities nearby were told to leave due to creek flooding.
Neighborhoods near the Santa Rita Creek in Monterey County were put under a warning Saturday afternoon because of concerns the creek “will spill over its banks,” according to the sheriff’s office.
“Rising water has made roads impassable in the area,” Sacramento County officials said on Facebook, urging those who were already on the road to head to safety and those who were home to “stay at home.”
A state of emergency was issued by the county on Saturday due to the atmospheric river it has been experiencing causing transportation impacts, rising creek levels and flooding in the Wilton area.
“If you have to travel, use caution. City crews are working through a mountain of reports of flooding.