Whitecaps are often generated on the Potomac River near the Naval Research Laboratory by wind fields associated with the passage of cold fronts. When the fronts clear the air so that sunshine prevails during the morning hour, usually about midday scattered cumulus clouds begin to appear....
Schooley, Allen H.. 1972. "Whitecap suppression by cloud shadows on the Potomac River." Journal of Marine Research 30, (3). https://elischolar.library.yale.edu/journal_of_marine_research/1248