When I was taking this I thought it some kind of runt C. affinis. Turns out it's a new-to-me Clarkia. I need to stop blaming my botanical incompetence on the plants.
I was out that way to re-survey a population in Alameda County, but sadly I couldn't find it. Or it wasn't blooming. Or they're all dead. Finding this group at least convinced me that they are blooming in the region and that I am capable of noticing them.
Clarkia is a genus within the flowering plant family Onagraceae. Over 40 species are currently classified in Clarkia; almost all are native to western North America, though one species (Clarkia tenella) is native to South America.