Debris Flow — Mariposa, California

2022-12-27 · near Foresta, Mariposa, California

Event narrative

Yosemite National Park employees reported two people were killed by a rockslide near the intersection of SR 140 and Big Oak Flat Road in Yosemite National Park.

Wider weather episode

A strong upper low pressure system moved through California on December 27. This system had abundant moisture associated with it as it pulled up a deep fetch of moisture of tropical origin. This system brought widespread moderate to heavy precipitation to the area between the early morning until the early evening of December 27. The heavy rainfall produced a rockslide in Yosemite National Park which resulted in two fatalities. The precipitation tapered off by the early morning of December 28. Much of the higher Sierra Nevada picked up between an inch and a half and three inches of liquid precipitation with the precipitation mainly falling as snow above 7500 feet where many stations picked up between 18 and 30 inches of new snowfall. The snow level briefly lowered to around 6000 feet during the evening of December 27 and some light snowfall was observed between 6000 and 7500 feet. The Sierra foothills generally received between 1 to 2 inches of rain while 0.75 to 1.5 inches of rain fell in the San Joaquin Valley and the Tehachapi Mountains. Several reports of nuisance flooding were reported by law enforcement and on social media. Rain shadowing effects limited precipitation in the Kern County Deserts to a quarter inch or less. This system also brought some strong wind gusts to the mountains as several stations measured gusts exceeding 40 mph and a few low impact stations had brief gusts above 60 mph.

View location on OpenStreetMap → (37.7188, -119.6805)

Source: NOAA Storm Events Database, event_id 1061849. Narrative written by the NWS forecast office that issued the report.