Atmospheric river set to slam California with rain, wind and welcome snow

SAN FRANCISCO (CN) — An atmospheric river taking aim at the Golden State promises rain and snow, both welcome but raising concerns about flooding, dangerous coastal conditions and power outages.

The atmospheric river on its way is a low pressure system already causing light rain showers over the northern coast. San Francisco meteorologists for the National Weather Service said Wednesday morning that wind gusts of up to 70 mph have already been recorded in some areas. The San Francisco station said those winds post a danger this afternoon, with the entire coast under a high wind warning and on watch for downed trees and power outages.

The high winds are also raising eyebrows in Southern California, as the service’s Los Angeles station warned of hazardous ocean conditions and peak surf heights up to 12 feet in Ventura and Los Angeles Counties, and up to 18 feet along the Central Coast.

While forecasters have lowered expectations on how much rain will fall, coastal mountain ranges could see up to 5 inches of rain while up to 2 inches could fall in the valleys. Because it will fall in a relatively short period of time, there could be problems.

“Given the already soggy nature of area soils this is well enough to result in nuisance flooding issues on roadways and streams, along with shallow landslides, and rises on mainstem rivers (with a few potentially breachingflood stage),” the meteorologists said. “Steadier coverage of showers should persist into the evening hours with coverage gradually waning by morning. Winds will ease during the early morning hours as well.”

The National Weather Service’s Sacramento station said in a discussion Wednesday morning that southeasterly winds with gusts of 40 to 55 mph will drive the approaching storm into the valley.

Across Northern California, heavier rain is expected to arrive in the late afternoon and last through the night into early Thursday. The Sacramento Valley could see up to 2 inches of rain with up to 4 inches falling in foothill locations. A flood watch is in effect through Thursday night for much of the north state, including throughout the Sacramento Valley and Delta.

Heavy snow is also possible through this period in the mountains above 6,000 feet with up to 2 feet of snow possible in the Sierra. A winter storm warning is in effect through Thursday morning.

Meteorologists say that the wet, windy pattern is likely to continue through the next several weeks, causing above normal precipitation across the state. This is particularly likely for Southern California and comes on the heels of flash floods in San Diego after more than 150 billion gallons of water fell on San Diego County over three days, submerging streets and freeways. The region is under a high wind watch, and further north the mountains of San Bernardino and Riverside counties are under a winter weather warning with snow as low as 4,500 feet expected by Thursday.

That promising outlook for fresh powder is welcome. State scientists said in a snow survey Tuesday that California’s snowpack is below average for the winter season, particularly in the southern San Joaquin valley range. The state needs to see strong storms in February and March to make good headway on the coming year and avoid drought.

Given the concerns about flooding and power outages, Governor Gavin Newsom said in a statement Tuesday afternoon that the State Operations Center in Mather was activated to coordinate a unified response to the storm, as was the Flood Operations Center.

“The state is working around the clock with our local partners to deploy life-saving equipment and resources statewide,” Newsom said. “With more storms on the horizon, we’ll continue to mobilize every available resource to protect Californians.”

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