The Yosemite Bitter Root (Lewisia disepla) is one of the pleasures of Yosemite Spring. Botti (p. 248) puts it this way:
In early spring, when snow is still several feet deep in the surrounding forest, many domes above Yosemite Valley are carpeted with thousands of large, pink flowers of this Lewisia. The spectacular floral display lasts only two to three weeks, depending on elevation, and is seldom witnessed by any but the dedicated hiker or skier.
I don't know as I would characterize the 13-18mm petals as "large." In fact, I find them easy to miss nestled in the granite gravel and sand. Their life cycle is admirably adapted to the harsh dome tops they grow on. The Yosemite Bitter Root hides under the snow all winter long with fully-developed buds. As soon as the snow clears, they flower, get pollinated and produce seeds before the water in the sand and gravel shallows runs out for the summer. Summer winds disperse the seeds across the dry domes, where they lie dormant until the autumn rains. In October, the seeds germinate and the plants develop full buds in time to be covered by snow and await the spring for the buds to bloom.