The last day of summer could bring snow to the Sierra, weather forecasters say. Thursday morning will see near-freezing temperatures and a 20 to 30 percent chance of precipitation in Sierra locales including Truckee, South Lake Tahoe, Reno and the higher elevations of Yosemite. Friday morning will be a little colder, under clear skies. Closer to the coast, a frost advisory has been issued for 3 to 8 a.m. Thursday in parts of Trinity and Mendocino counties, including Weaverville and Willits, the National Weather Service said. Temperatures there are expected to be in the low 30s.