This image comes courtesy of NASA's Terra satellite. Taken on January 27, it clearly shows streams of air moving south and east across the Great Lakes. Those ribbons of white are called cloud streets—yes, that is the technical term—and they're right in line with the prevailing winds. Cloud streets are bands of cumulus clouds that form when a layer of cold air gets sandwiched between (relatively) warm water below and air above. The water gives off heat, causing thermal columns to rise up and then roll back onto themselves, forming kind of a long jelly roll of moist air. Those jelly rolls are the cloud streets (you can see a diagram here).