Who needs drones and aliens when you can have this in the sky ... Roll clouds form when a cooler, denser airmass pushes under another airmass, causing this rising and 'rolling' motion on the ...

the sky over Bismarck turned into a series of snow-covered hills. A rare form of clouds blossomed over the city Friday afternoon, creating the illusion of rolling hills covered in snow.

The pleasant rhythm of waves lapping at the lake shore is caused by wind blowing over the water at a faster speed than the ...