Heavy Rain in Lassen County, California

A trained spotter located 5.0 mi WNW of Susanville, CA, and a trained spotter located 6.0 mi SSE of Susanville, CA, reported total rainfall amounts of 1.23 inches and 2.90 inches respectively.

The weather pattern changed on the 20th with the approach of an upper level storm system that hovered off the Pacific NW. This allowed for a deep plume of moisture, aka atmospheric river (AR), to be advected towards northern CA for the second half of the week. This enhanced the primary hazard being heavy precipitation across the region with projected liquid storm totals of 2.5-3.0 inches for the Sierra crest, 0.75-1.00 inch for the foothills, and 0.10-0.75 from the Basin and Range into far western Nevada. The secondary hazard that was expected with this system was gusty southwest to south winds. Projected gusts of 30-40 mph in the valleys across the region were complemented with gusts exceeding 70-80 mph across the Sierra crest. Blended guidance showed a 30-50% chance of 50+ mph gusts, while ECMWF Extreme Forecast Index (EFI) also indicated an anomalous event. Other wind impacts included turbulence, hazardous boating conditions, and fire weather concerns.