Snowmelt is expected to cause the Merced River in Yosemite Valley to rise above flood stage this weekend.
The Merced River at Pohono Bridge has crested at a higher point each night this week and is expected to reach flood level -- about 10 feet -- early Sunday morning, said National Weather Service forecaster Kevin Durfee. The river will rise to flood stage, or just beyond it, for several days.
"There's an awful lot of snowpack to melt this year," Durfee said. A cooler spring has helped prevent more snowmelt until now, but temperatures at Yosemite will be in the 80s this weekend. "With a dense snowpack, you'll get higher flows in rivers throughout the Sierra."
Yosemite spokeswoman Kari Cobb said the park doesn't typically open campsites affected by seasonal flooding -- specifically, Lower Pines and North Pines -- until later in the season.
The lower Merced River through the Central Valley could rise but it won't reach flood levels, Durfee said.
Yosemite will not charge an entrance fee on Saturday and Sunday as a celebration of National Trails Day, so park officials expect more visitors than normal this weekend. Cobb said visitors should be cautious around rivers and waterfalls, because water in the park is cold and fast-moving.