Snow Rollers

Is Old Man Winter whittling a shiv? Is Frosty the Snowman rolling up the bodies of all the children that didn't believe in him in giant ice-rugs for later disposal?

Nope. Those are "Snow Rollers," and the name is pretty self-explanatory. For a snow roller to form, the ground must be covered by a layer of ice that snow will not stick to, the layer of ice must be covered by wet, loose snow with a temperature near the melting point of ice, the wind must be strong enough to move the rollers, but not strong enough to blow them apart and, finally, the ground must have a slope, to start the rolling.