A rare meteorological phenomenon in which large snowballs are formed by the wind, which blows the snow on the ground, picking it on its way, in the same way as children mold snowmen.
Typically they cylindrical hollow interior layers, among which the first layer – the weak and thin compared to the outer layers, and they are easily blown away.
Conditions necessary for the acquisition forms Snow rolls: the land must be covered with a layer of ice to which snow will not stick. layer of ice must be covered with wet, loose snow with temperatures near the melting point of ice.
Wind must be strong enough to move the snow roll, but not strong enough to blow them up too quickly. (Google Translate).