By Brendan O’Brien and Rich McKay (Reuters) – After forcing thousands of Californians to evacuate and burning more than 100 structures, a stubborn wildfire burning northwest of Los Angeles on Friday challenged firefighting crews working to snuff it out even as fierce winds in the area calmed. Overnight, the area scorched by the blaze – dubbed the Mountain Fire – remained at about 20,000 acres (8,100 hectares) in Ventura County.