Heavy Rain in Alpine County, California

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.

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.