Most of us have seen wave patterns on sand dunes; until one winter day in Yosemite, I had never seen them on snow! And I've never seen them on snow since, at least not like this. But there they were, pretty as you please, created by gentle winds blowing over fresh powder in Yosemite Valley.
Usually, snowfall in the Valley (elevation 4000 feet) does not linger long, nor is deep. These patterns were made probably the previous day, and then the sun helped melt the tips of the ridges and the snow surface, and the cold night froze the patterns into place for this early morning photo.
Then the sun did its work again, and by day's end the intricate waves had softened like melted butter.