The melting of this year’s record snowpack is continuing to create problems, with authorities warning of more flooding in Yosemite National Park and fast-moving, high water at a popular Central Valley river. The National Weather Service issued a flood warning Tuesday as Yosemite’s Pohono Bridge was expected to be swamped overnight. By 4 a.m. Wednesday, the Merced River probably will reach its flood stage of 10 feet, said Christine Riley, a weather service meteorologist in Hanford, Calif.