Torrential rain from an atmospheric river with locally heavy convective showers brought flash flooding to portions of the northern Sierra and Motherlode foothills. The heaviest flooding was in Groveland, where 4-5 of rain fell, combining with 8-9 of rain in higher elevations upstream. There was also widespread damage in Tuolumne County to roads from debris flows, soil erosion, erosion of water conveyance systems, sewer systems that were inundated with excess water and debris. Roads damaged inluded state Highways 49 and 132. Moccasin Dam was damaged and came close to failure, with  road closures. A tornado struck an amphitheater in Wheatland and caused minor damage. Heavy snow caused travel problems over Sierra highways.

Flood in NEVADA, CALIFORNIA
From 21-MAR-18 08:00:00 to 22-MAR-18 08:00:00 (PST-8)
Location: WOLF
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Department of Highways

Combie road flooded due to overtopping of the adjacent Ragsdale Creek.

Flood in EL DORADO, CALIFORNIA
From 21-MAR-18 08:00:00 to 22-MAR-18 08:27:00 (PST-8)
Location: CLARKSVILLE
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Closed lanes on Highway 50 at Latrobe Rd/El Dorado Hills due to rockslide.

Flood in SACRAMENTO, CALIFORNIA
From 21-MAR-18 09:00:00 to 22-MAR-18 09:30:00 (PST-8)
Location: FOLSOM
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Street flooding on Dean Way east of Wales Dr. in Folsom.

Flood in EL DORADO, CALIFORNIA
From 21-MAR-18 09:00:00 to 22-MAR-18 09:37:00 (PST-8)
Location: SHINGLE SPGS ARPT
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Public

Street flooding in Cameron Park Estates Mobile Home Park. Video via Twitter.

Flood in SACRAMENTO, CALIFORNIA
From 21-MAR-18 10:00:00 to 22-MAR-18 10:08:00 (PST-8)
Location: BRIDGE HOUSE
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Vehicle stuck in a flooded roadway on Scott Rd. and Latrobe Rd.

Flood in TUOLUMNE, CALIFORNIA
From 21-MAR-18 13:00:00 to 22-MAR-18 13:06:00 (PST-8)
Location: GROVELAND PARSONS AR
Flood cause: Heavy Rain
Property damage: 8.00M
Crop damage: 0.00K
Reported by: Law Enforcement

Extensive flooding in downtown Groveland, as floodwaters ran down the main street, Highway 120. Property was damage and water rescues for stranded residents. There was significant damage done to Groveland Community Hall and Mary Laveroni Community Park. Preliminary estimates from Tuolumne County are approximately $8 million for 16 damaged sites along county maintained roads. A very large portion of these damages are seen in the sinkhole at Ferretti Road and slides and embankment loss on Priest Coulterville Road.

Funnel Cloud in YUBA, CALIFORNIA
From 21-MAR-18 16:25:00 to 21-MAR-18 16:31:00 (PST-8)
Location: WHEATLAND
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A funnel cloud was observed, weakening. Dime size hail was also observed.

Funnel Cloud in YUBA, CALIFORNIA
From 21-MAR-18 17:23:00 to 21-MAR-18 17:28:00 (PST-8)
Location: WHEATLAND
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

A funnel cloud was observed, extending halfway to the ground.

Tornado in YUBA, CALIFORNIA
From 21-MAR-18 17:40:00 to 21-MAR-18 17:45:00 (PST-8)
Location: ARBOGA
Tornado F-scale: EF0
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Tornado touchdown observed by Yuba County deputies at Yuba County. Minor damage was observed, including ripped tarps and objects knocked over. Another touchdown was observed and videoed in an open field, about a mile to the north. No damage was observed at the second touchdown location.

Heavy Snow in WEST SLOPE NORTHERN SIERRA NEVADA, CALIFORNIA
From 21-MAR-18 09:00:00 to 23-MAR-18 09:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Heavy snow fell, causing travel slowdowns disruptions over higher elevations of mountain highways including I80 and Highway 50. At Kirkwood Ski Resort, a storm total of 32 of new snow was reported, 31 at North Star, 24 at Sierra at Tahoe. There was 8 of new snow at Kingvale, elevation 6100'.

Dense Fog in NORTHERN SACRAMENTO VALLEY, CALIFORNIA
From 21-MAR-18 15:48:00 to 21-MAR-18 15:48:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

There were 5 vehicles involved in an accident attributed to dense fog. There were 7 injuries reported.

Flood in YUBA, CALIFORNIA
From 22-MAR-18 17:01:00 to 27-MAR-18 20:17:00 (PST-8)
Location: MARYSVILLE
Flood cause: Heavy Rain
Property damage: 1.00M
Crop damage: 0.00K
Reported by: Emergency Manager

Heavy rain caused a railroad bridge in Marysville to sink. The bridge spans the Yuba River. Rail traffic over the bridge was shut down. A diesel pipeline attached to the bridge also had to be shut down. Union Pacific Railroad drove in new piles to stabilize the bridge. Repairs were completed on March 27.

Flash Flood in TUOLUMNE, CALIFORNIA
From 22-MAR-18 13:30:00 to 22-MAR-18 16:00:00 (PST-8)
Location: MOCCASIN
Flood cause: Dam / Levee Break
Property damage: 43.00M
Crop damage: 0.00K
Reported by: Newspaper

A period of heavy rain upstream from Moccasin Dam, in which about three inches fell during four hours led to significant erosion and at least one landslide. It caused a massive amount of water and debris to run downhill into the Moccasin Reservoir. The water level rose to 3 times the normal reservoir capacity and the emergency spillway was utilized. There was severe erosion of the emergency spillway and potential for the dam to fail.  The Power house and staff at the Moccasin Fish Hatchery were evacuated due to potential failure. All the fish in the Moccasin Creek Hatchery were killed when it flooded from the water coming over the emergency spillway.  The National Weather Service issued a flash flood warning associated with the probable dam failure, and the sheriff advised residents to avoid the area as a matter of public safety. The warning was reduced to a watch until the reservoir was drained and then the watch was canceled once the reservoir was drained.
Cleanup and repair efforts associated with a major storm that damaged Tuolumne County's Moccasin Creek Dam in March is expected to cost roughly $43 million, according to an estimate by the San Francisco Public Utilities Commission, which owns and operates the dam. That total includes $3.2 million in damage to the state fish hatchery at Moccasin Creek, which lies downstream.