White Clintonia [Clintonia umbellulata] found near the Blue Ridge Parkway, milepost 437, Glassy Mine Overlook, along the Mountains-to-Sea Trail, on 30 May 2015. It’s a member of the Lily (Liliaceae) family. Newcomb’s Wildflower Guide, pages 338-339, says its flowers bloom in spring and early summer.
USDA Plants Listing: Clintonia umbellulata