Snow rollers are nature’s way of making snowballs, that can sometimes be as large as a foot or two in diameter. Wherever these wintry miracles of nature occur, they make headlines, and they have been reported in states from Oregon to Vermont.
It is unlikely that most people have ever seen a snow roller, or even heard of them, for that matter. These very rare meteorological creations can only develop under specific conditions, but have been reported in most every state that is cold enough to have snow. Once only thought of as an Alaskan or Arctic occurrence, they have been reported in the last few years from Washington and Oregon, to Ohio, and Vermont.
First of all, in order for them to form, there needs to be a large open expanse of terrain, covered first with snow that has crusted over, and, secondly, with two or three inches of wet, packing snow. The crusted, icy snow beneath the wet packing snow enables the rollers to roll along, growing as they go. The ideal temperature for this is about 32 degrees F. A strong wind is also needed. Normally, the wind is somewhere between 20 and 40 mph. A stronger wind might break the rolls apart, but rollers have been found in areas where the wind speed exceeded 70 mph.
Somewhere, a little snow packs together into a sphere, and begins to roll in the wind, bouncing along on the wet snow, and crossing the terrain ,picking up more and more snow as it rolls along. Since there is no actual pressure put on the roll, as you would in making a snowman, the inside of the sphere is weakened and breaks up, leaving a doughnut shape when it comes to a stop, or something that looks a lot like manicotti.
Besides the terrain snow rollers, there are those that actually travel down hills, gaining momentum, and snow, as they go. It is believed that these particular snow rollers get their start from a lump of snow falling from a rock or a tree, before starting it’s trip downhill.
Bouncing along like tumbleweeds, they were a source of mystery and amazement to early pioneers and settlers. Originally, they were believed to be chunks of sod that had been caught in the wind, and began collecting snow. However, they were found to be all snow, and, by the time they stop, their interiors are virtually gone, leaving them to resemble hollow logs.
Even today, these miracles of nature are fascinating and mysterious wherever they form, only proving once again, that nature still has some tricks that we cannot control or duplicate.
http://www.crh.noaa.gov/gid/?n=news_13
