Fresno — Tall grass from a deluge of winter rains is fueling wildfires throughout the Western US, damaging more than a dozen homes in Nevada and forcing residents from communities on the outskirts of Yosemite National Park in California, authorities said on Tuesday.Yosemite remains open to visitors, but flames threaten more than 300 homes and buildings in mountain communities southwest of the park, clearing out the small town of Mariposa.The fire burning since Sunday also puts at risk powerlines providing electricity to the park, and it has closed roads travelled by tourists, officials said.Gov. Jerry Brown on Tuesday declared an emergency, bolstering the state's resources to battle the fire that he said has forced thousands of residents to flee and is expected to continue burning.Record rain and snowfall in the mountains this winter was celebrated for bringing California's five-year drought to its knees, but it has turned into a challenge for firefighters battling flames feeding on dense vegetation, officials said."There's ample fuel and steep terrain," said California Department of Forestry and Fire Protection spokesperson DeeDee Garcia. "It makes firefighting difficult."Smoke from the fire in Mariposa County has drifted more than 150 miles away to Reno.In a remote north-eastern corner of Nevada, roughly 14 homes were damaged or destroyed by a wildfire that started on Monday.Officials have lifted an evacuation advisory, allowing hundreds of people to return home and assess damage, authorities said.In Nevada, wind is driving the flames through invasive cheat grass — growing twice the norm, US Bureau of Land Management spokesperson Greg Deimel said."It is very thick, very dense," he said. "You get the winds and the density of the grass, the fire just goes."This summer's high temperatures follow a very wet winter that dumped more than 60 feet of snow at ski resorts in the Sierra west of Reno.The California blaze near Lake McClure east of Modesto, has charred more than 77 square km. Officials report having it 5% contained.It's burning near Highway 49, a historical route winding its way up California foothills of the western Sierra Nevada dotted with communities and landmarks that sprouted up during the state's Gold Rush.To the south, crews have increased containment of a 72-square-km blaze burning for a 10th day in the mountains of Santa Barbara County. It is 62% contained after destroying 16 homes.