Authorities have reopened Highway 20 between Nevada City and Interstate 80 after at least 10 semi trucks and at least 20 vehicles have were stuck in accumulating snow Monday, backing up traffic for hours. The chaos began shortly after 5 a.m. when a vehicle was reported to have spun out in the higher elevations of the Seirra Nevada foothills, about 16 miles northeast of Nevada City at an estimated elevation of 5,000 feet, according to the California Highway Patrol traffic incident website. Within an hour, the roadway near the Highway 20 intersection of Omega Road was completely blocked as semis …