Not either clarkia or checkermallow. This is not a bushy plant at all, it's much more vinelike, or a better description is stringy. Perhaps it isn't in full bloom, you can see unopened flowers on that particular branch. I took the photo near Stampede Reservoir along Henness Pass Road. These flowers were open Sunday 7/18 but not the previous Sunday. The flower is about half inch to three-quarters inch wide.