A deep layer of monsoonal moisture pushed northwest and north into California, Sierra, and western Nevada in a southerly upper flow that marked the western margins of an area of strong high-pressure ridging into the Great Basin region.  Thickening mid-level moisture coupled with steep afternoon lapse rates and warmer surface heating initiated deep columns of slow-moving moisture-laden showers and thunderstorms with torrential rains over the 2021 Tamarack burn scar. This resulted in widespread flash flooding and debris flows in Alpine County CA that created a number of impacts. Rainfall rates of 2.22 inches per hour were observed during the peak of the storm in Markleeville, CA which corresponds to at least a 500 year recurrence interval and possibly 1000 year, per NOAA 14 atlas.

Heavy Rain in ALPINE, CALIFORNIA
From 03-AUG-22 15:00:00 to 03-AUG-22 16:00:00 (PST-8)
Location: MARKLEEVILLE
Property damage: 791.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station (MKEC1) located in Markleeville, CA, reported heavy rain total of 1.82 inches. Utility Mesonet sensor also located in Markleeville, CA, reported 2.49 inches in 90 minutes and 2.22 inches in 60 minutes.

Debris Flow in ALPINE, CALIFORNIA
From 03-AUG-22 16:00:00 to 03-AUG-22 17:00:00 (PST-8)
Location: MARKLEEVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Severe flooding was reported along State Route 89 in and out of Markleeville, CA with numerous debris flows. Roadway damage was also reported, along with reports of vehicles starting to get swept away.

Debris Flow in ALPINE, CALIFORNIA
From 04-AUG-22 17:00:00 to 04-AUG-22 18:00:00 (PST-8)
Location: LOOPE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy rain in the vicinity of the Tamarack Fire Burn Scar caused a slide over State Route 4 that was reported by CHP to be 3-4 feet deep and closed the highway in both directions. No rainfall reports in the exact location, but estimates of 0.5-1 were reported to the south and 2-3 to the north, which occurred in a few hours. This is in addition to the heavy rainfall the day before.

Heavy Rain in MONO, CALIFORNIA
From 05-AUG-22 19:00:00 to 05-AUG-22 20:00:00 (PST-8)
Location: MAMMOTH LAKES
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station DW5868 located at Mammoth lakes, CA., reported a rainfall total of 1.01 inches.

Heavy Rain in MONO, CALIFORNIA
From 03-AUG-22 18:00:00 to 03-AUG-22 19:00:00 (PST-8)
Location: WALKER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station (LVTC1) located 1.1 mi S of Leavitt Meadows (SNOTEL) reported 0.60 inches total rainfall.

Debris Flow in ALPINE, CALIFORNIA
From 03-AUG-22 15:07:00 to 03-AUG-22 15:11:00 (PST-8)
Location: MARKLEEVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Grover Hot Springs state park staff reported debris flow over Hot Springs RD due to intense, heavy rainfall. Depth and damage were unknown at this time. Also, Caltrans and CHP reported boulders and rocks in the area with one part of Hot Springs RD starting to wash out.  Another road was reported impassible.

Heavy Rain in MONO, CALIFORNIA
From 05-AUG-22 13:00:00 to 05-AUG-22 14:00:00 (PST-8)
Location: WALKER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

AWOS station (KBAN) located at the Marine Corp Mountain Warfare Training Center (MCMWTC) reported heavy rainfall total of 1.49 inches.

Heavy Rain in MONO, CALIFORNIA
From 05-AUG-22 18:00:00 to 05-AUG-22 19:00:00 (PST-8)
Location: CRESTVIEW
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station (CRVC1) located near Crestview, CA., and Mesonet station (DEXC1) located 13 mi ENE of Crestview, CA, (near 2021 Dexter fire scar) reported rainfall totals of 0.92 and 3.33 inches respectively.

Heavy Rain in MONO, CALIFORNIA
From 03-AUG-22 16:45:00 to 03-AUG-22 19:15:00 (PST-8)
Location: BRIDGEPORT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station EW3821 located in Bridgeport, CA reported 0.81 inches total rainfall between 5:45 and 8:15 pm.