In the Handy Book of Meteorology, 1868, by Alexander Buchan, pg. 202: Alexander Buchon observed how the snow, covering the ground rolled up into large barrel style mass. He had seen this pile once before in February, 1847. The following description is how the snow rollers formed, “In calm weather, a temperature near the freezing point, so as to give adhesion to the snow, while it is not so warm to thaw it; a good breeze of wind to spring up when the other circumstances are favorable to their formation.” Snow rollers are a phenomena seen by exceptionally few people. Chemists wrote about it in early journals of meteorology, as they write today in meteorology journals.
Most meteorologists have not seen snow rollers. The majority of snow blown by the wind ends up as snowdrifts. Every so often, the gleeful wind decides to play with the snow and roll it into a cylindrical ball. The balls may be small or large. They are all hollow in the center.
The balls leave behind it a series of intricate sastruga that have to be seen before the new snow falls and covers them. The ridges have all types of patterns that are geometric. Some people think that like the crop circles, aliens, who have come to earth create the snow rollers.
Snow rollers are not common. It takes the right conditions for them to be created. Perfect snow-rollers need a flat surface. They can range from two inches to the size of a barrel. The optimum conditions need to be met:
*A layer of ice must cover the ground. This acts as coating so the snow will not stick to it.
*Light, fluffy snow needs to fall on the ice.
*The temperature needs to rise a little – close to the melting point of the ice 32 degrees F to 39.5 degrees F). This makes the snow slightly sticky.
*Wind is what makes the snow move. If it is too slow, nothing will happen. If it is too hard, it will carry the snow off into a snowdrift. The wind should be a steady rush, at least 25mph, to begin the formations of the form.
*The blast of wind snatches up a nugget of snow and rolls it. The wind continues to push and the new snow keeps collecting. The glaze of ice underneath the snow helps the wind and snow keep the momentum going.
The result of this phenomenon in nature brings awe and excitement to all who see it.