Winter Storm and Flooding in California, December 21 to 29, 2021

There were multiple reports of power outages across the Sierra high country after heavy snow and winds. Gusts across the high Sierra reached in excess of 100 mph for several days from December 22nd through the 27th. Peak gusts over the crest ranged from 113 to 136 mph. Interstate 80 was closed to traffic in both directions for a period of time due to snow and low visibility. Widespread power outages occurred with thousands of people without power some for extended periods of time in brutal winter conditions.

Sierra snow lab reported between 117.9 inches of snow accumulation for the entire period of winter weather.

Caltrans was unable to provide complete snow reports for the stormy conditions around the Holiday as provided a partial report for the 23rd to 25th of 78 inches at their Kingvale station. This was due to the immense workload caused by the series of winter storms that lead to many miles of blocked roadways due to snow, downed trees and powerlines as well as reduced visibility. Traffic was closed to through traffic on I-80 for several days as crews worked to clear snow and debris. The closure was approximately from 11:00am on December 25th through 8:30 am on December 29th. Chain controls continued into 10:30am on December 30th on I-80. When I-80 finally opened after being closed for several days, only essential travel was allowed. Most mountain roads were impacted in the Sierra with closures of HWY 50, 89, and 20. Many back roads were also reported to be impassible due to the winter conditions.

Zone 67 saw high impacts from the series of winter storms in late December. Low elevation snow created challenging conditions for Caltrans crews with snow removal required before down powerline and trees could be removed and power could be resorted. A dusting of snow was reported down to Auburn, Ca. The Twain Heart Lake Dam reach 100% capacity during the event threating a potential dam failure. Hail was reported at Applegate off I-80 at 3:55 pm on the 27th. Storm total snow reports generally ranged from 3 to 12 inches in Zone 67.

Caltrans reported that winds in combination with rain and snow caused downed trees and power lines, which led to closed and impassible roadways, hazardous driving conditions and extended power outages. tens of thousand of people were left without power in winter weather conditions, many for more than 3 days. One estimate said 50,000 customers were still without power at the end of the month of December. Peak wind gusts for the zone reached from 32 to 40 mph. Damage costs are estimated.

Caltrans was unable to provide complete snow reports for the stormy conditions around the Holiday as provided a partial report for the 23rd to 25th of 78 inches at their Kingvale station. This was due to the immense workload caused by the series of winter storms that lead to many miles of blocked roadways due to snow, downed trees and powerlines as well as reduced visibility. Traffic was closed to through traffic on I-80 for several days as crews worked to clear snow and debris. The closure was approximately from 11:00am on December 25th through 8:30 am on December 29th. Chain controls continued into 10:30am on December 30th on I-80. Most mountain roads were impacted in the Sierra with closures of HWY 50, 89, and 20. Many back roads were also reported to be impassible due to the winter conditions.

CoCoRaHS observers reported low elevation snow across the Motherlode during the storm. Here are the following reports: 6.6 miles ESE of Placerville at an elevation of 2587 feet saw 12.5 inches, 2 miles N of Tuolumne City at an elevation of 2915 feet saw 11 inches, Volcano at an elevation of 2000 feet saw 8.4 inches, East Sonora at an elevation of 2100 feet saw 5 inches, 1.3 miles WSW of Challenge-Brownsville at an elevation of 2049 feet saw 13.5 inches, 1.3 miles NNE of Grass Valley saw 19.4 inches, 1.7 miles SSE of Nevada City saw 30 inches, and 0.5 miles SE of Applegate saw 10 inches of storm total snow.

Chester reported 30 inches of storm total snow.

Yolo county reported numerous flooded and closed roadways. Reported storm total rainfall amounts in the area were around 2 to 2.5 inches.

Roadway flooding reported in multiple locations around the Sacramento metro region on 12/23/21. Reported storm total rainfall amounts in the area were in excess of 2.5 inches.

Quincy reported 13.5 inches of storm total snow.

California highway patrol reported a slide and a 30 ft wide stream of water going across the roadway on SR16. Reported storm total rainfall amounts in the general area were in excess of 2.5 inches.

A brief funnel cloud was reported over Newman, CA by the Modesto Bee on December 27th at 13:40.