Wildfires burning near Northern California vineyards and in the Yosemite National Park area were threatening hundreds of homes even as crews worked to contain them. The Sand Fire in the Sierra Nevada foothills east of Sacramento was 50 percent surrounded as of late Sunday, after burning 13 homes and 38 outbuildings. It has scorched roughly 6 square miles of rugged grassland and timber near wine-growing regions in Amador and El Dorado counties.