A strong atmospheric river event produced a major heavy rain, high wind, and high elevation snow event for much of the region. Record-setting rainfall amounts for many areas of the Sierra into western Nevada. NWS Reno received multiple reports of mud and rock slides in the Sierra along I-80 near the summit, and CA 70 and CA 89 in Sierra, Plumas, and Lassen Counties.

Debris Flow in LASSEN, CALIFORNIA
From 24-OCT-21 00:00:00 to 25-OCT-21 12:00:00 (PST-8)
Location: (SVE)SUSANVILLE MUNI
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported several areas with debris in the roadway, and the culvert under the railway is plugged.

Debris Flow in PLUMAS, CALIFORNIA
From 24-OCT-21 00:00:00 to 24-OCT-21 15:00:00 (PST-8)
Location: GRAEAGLE
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

California Highway Patrol reported large rocks in roadway on Gold Lake road above Graeagle Lodge.

Debris Flow in PLUMAS, CALIFORNIA
From 24-OCT-21 00:00:00 to 24-OCT-21 09:00:00 (PST-8)
Location: VINTON
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

California Highway Patrol reported rocks, mud in road near Chilicoot Campground.

Debris Flow in PLUMAS, CALIFORNIA
From 24-OCT-21 00:00:00 to 24-OCT-21 11:00:00 (PST-8)
Location: TWO RIVERS
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

California Highway Patrol reported a large (larger than a basketball) boulder in the road on State Highway 70 near Camp Layman Road.

Debris Flow in EL DORADO, CALIFORNIA
From 24-OCT-21 00:01:00 to 24-OCT-21 16:15:00 (PST-8)
Location: ECHO LAKE
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

US Highway 50 is closed due to a late night rock fall near Echo Summit.

Debris Flow in MONO, CALIFORNIA
From 24-OCT-21 00:01:00 to 24-OCT-21 17:15:00 (PST-8)
Location: MONO LAKE
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

California Highway Patrol reported the left lane on us 395 at Conway Ranch Road is closed due to a large rock in the roadway.

Debris Flow in SIERRA, CALIFORNIA
From 24-OCT-21 00:01:00 to 24-OCT-21 20:00:00 (PST-8)
Location: SIERRAVILLE DRWTR AR
Flood cause: Heavy Rain / Burn Area
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

California Highway Patrol reported a large boulder in the middle of the westbound lane of US Highway 89.

Heavy Rain in SIERRA, CALIFORNIA
From 24-OCT-21 08:00:00 to 25-OCT-21 10:00:00 (PST-8)
Location: SIERRAVILLE DRWTR AR
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Several CoCoRahs Observers and Mesonet/ASOS sites reported rainfall amounts ranging from 0.4-1.0 near Independence Lake, 2.0-4.0 in and around Portola, CA, and 4.0-6.0 west of Verdi, NV.

Flash Flood in LASSEN, CALIFORNIA
From 24-OCT-21 00:01:00 to 24-OCT-21 09:00:00 (PST-8)
Location: DOYLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

California Highway Patrol reported 3.5 feet of water over the road on the north end of Constantia Road making the roadway impassable.

Flash Flood in NEVADA, CALIFORNIA
From 24-OCT-21 00:01:00 to 24-OCT-21 12:30:00 (PST-8)
Location: SODA SPGS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

California Highway Patrol reported ton of rocks and water come off the mountain side of old 40, (Donner Pass Rd between Truckee and Donner Summit.) the road is now closed as it is not safe to pass due to erosion and falling debris.

Heavy Snow in GREATER LAKE TAHOE AREA, CALIFORNIA
From 24-OCT-21 00:01:00 to 24-OCT-21 07:15:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Broadcast Media and PG&E reported several inches of heavy wet snow around the South Lake Tahoe area. Echo Summit received up to a foot of new snow. PG&E reported about 5 inches of snow which resulted in a power outage in the South Lake Tahoe area.

Heavy Snow in GREATER LAKE TAHOE AREA, CALIFORNIA
From 23-OCT-21 22:00:00 to 24-OCT-21 14:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law Enforcement in Nevada County reported 25 inches of snow near soda springs or 7 mi W of Truckee, CA, since 10 PM on 23OCT.

Heavy Rain in MODOC, CALIFORNIA
From 22-OCT-21 17:00:00 to 25-OCT-21 17:00:00 (PST-8)
Location: LAKE CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

COOPs observers and Mesonet/ASOS sites reported rainfall amounts ranging from 0.3-1.0 in the far NE corner of Modoc county in and around Fort Bidwell, CA, as well as 1.0 -2.0 within the area from Cedarville, CA  to Lake City, CA.

Heavy Rain in MONO, CALIFORNIA
From 22-OCT-21 10:00:00 to 25-OCT-21 10:00:00 (PST-8)
Location: MONO LAKE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

COOP and CoCoRahs observers, as well as Mesonet/ASOS sites, reported rainfall amounts ranging from 1.0-3.0 around Walker, CA, to the Lee Vining/Mono Lake area with 4.0-6.0 around the Crestview to Mammouth Lakes, CA region.

Heavy Snow in GREATER LAKE TAHOE AREA, CALIFORNIA
From 23-OCT-21 15:00:00 to 24-OCT-21 15:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter in Placer County, 1.0 mi NNW of Homewood, CA measured 12 inches of snow along with 6.4 inches of liquid over the previous 24 hours.

Heavy Snow in GREATER LAKE TAHOE AREA, CALIFORNIA
From 23-OCT-21 20:30:00 to 24-OCT-21 08:30:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported 18 inches of snow at Lake Davis in Plumas, County.

High Wind in MONO, CALIFORNIA
From 25-OCT-21 01:39:00 to 25-OCT-21 01:39:00 (PST-8)
Magnitude: 138.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A peak wind gust of 159 mph was recorded from the summit of Mammoth Mountain at an elevation of 11,053 feet.

Heavy Rain in PLUMAS, CALIFORNIA
From 24-OCT-21 08:00:00 to 25-OCT-21 10:00:00 (PST-8)
Location: BECKWOURTH
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Several Mesonet/ASOS sites reported rainfall amounts ranging around 1.0 near Cromberg, CA; 2.0-4.0 west of Janesville, CA; and 4.0-6.0 SE of Frenchman Lake.

Heavy Rain in PLACER, CALIFORNIA
From 24-OCT-21 08:00:00 to 25-OCT-21 08:19:00 (PST-8)
Location: TAHOE PINES
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRahs Observers, trained spotters, and Mesonet/ASOS sites reported rainfall amounts ranging from 1.0-2.0 near Alpine Meadows ski resort, 2.0-5.0 in and around Homewood, CA, and as much as 6.0 at Tahoe City, CA.

Heavy Rain in LASSEN, CALIFORNIA
From 22-OCT-21 10:00:00 to 25-OCT-21 10:00:00 (PST-8)
Location: LEAVITT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

CoCoRahs Observers, trained spotters, and Mesonet/ASOS sites reported rainfall amounts ranging from 0.5-3.0 in the area between Janesville to Susanville, CA; 3.0-4.0 in the Westwood to Lake Almanor region; and up to 6.0 about 3.0 mi SSW of Susanville, CA.
Trained spotter in Doyle at an elevation of 4500 feet reported 7.28 inches of rain as of midnight (24 hour period starting 24/0001 LST) with an additional 1.49 inches falling since midnight.  The spotter also reported that snow was falling around midnight but not accumulating. Total rainfall amount of 8.77 was reported at this site.

Heavy Rain in NEVADA, CALIFORNIA
From 24-OCT-21 07:00:00 to 25-OCT-21 10:00:00 (PST-8)
Location: HOBART MILLS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

COOP and CoCoRahs observers, trained spotters, and Mesonet/ASOS sites reported rainfall amounts ranging from 1.0-3.0 in the area of Glenshire-Devonshire/Donner Peak, CA, and 4.0-6.0 in and around Truckee, CA.

Heavy Rain in ALPINE, CALIFORNIA
From 24-OCT-21 10:00:00 to 25-OCT-21 10:00:00 (PST-8)
Location: MARKLEEVILLE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

About 4.38��� of rainfall reported by mesonet station MKEC1 located 0.88mi SW of Markleeville, CA.

Heavy Rain in EL DORADO, CALIFORNIA
From 22-OCT-21 17:00:00 to 25-OCT-21 17:00:00 (PST-8)
Location: FALLEN LEAF
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRahs Observers, trained spotter, and Mesonet/ASOS sites reported rainfall amounts 1.0-2.0 around Echo Lake, 2.0-4.0 from Echo Summit to Meyers, CA; and 6.0-8.0 reported from Meyers, CA to South Lake Tahoe, CA.
A trained spotter located 2.0mi NW of Meyers, CA (COCORAHS STATION CA-ED-20) reported 24 hour total for rain-snow melt of 8.40 inches. The trained spotter also reported 4 inches of snow fell with SWE of 1.14 inches.