Anemone occidentalis http://www.botanicalgarden.ubc.ca/forums/showthread.php?t=29244&highlight=hippies
Yes, a snow-melt plant, and therefore dependent on the elevation, aspect, etc.. You can see them in bloom into early August in the mountains around here, if you're up high enough in the moist alpine meadows where they occur... and you can see them in seed lower down on the same hike.
You'll often see them growing through the snow near the edge of its receding! They go into bloom shortly after.