Highway 253, also known as the Boonville Ukiah Road, is closed after Caltrans vehicles were unable to clear the roadway of 40-50 vehicles stuck in the roadway due to snow, as per the California Highway Patrol Traffic Information page.
Scanner traffic indicates personnel are staged in the area slowing down traffic
https://twitter.com/CaltransDist1/status/1354256018260152320?s=20
UPDATE 9:51 a.m.
Highway 253 has reopened to thru traffic confirmed by both the Caltrans Quickmap and a California Highway Patrol dispatcher.