Debris Flow — Sierra, California

2021-10-24 · near Sierraville Drwtr Ar, Sierra, California

Event narrative

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

Wider weather episode

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.

View location on OpenStreetMap → (39.5500, -120.3200)

Source: NOAA Storm Events Database, event_id 987333. Narrative written by the NWS forecast office that issued the report.