Yosemite Valley closes amid record snowpack and flood warnings.

Yosemite Valley will close Friday night until Wednesday due to risks of flooding from melting snow.
The Merced River could rise over 12 feet, above the flood stage of 10 feet.
Most of Yosemite National Park will close, though some areas like Hetch Hetchy will remain open.
Visitors are flocking to see Yosemite's waterfalls before the closure, though they are warned to avoid the dangerous, fast-flowing rivers.
Emergency response could be delayed due to the flooding.