They appeared overnight, as mysteriously as crop circles, only unlike that phenomenon, humans did not turn out to be their creators.
People all over the windswept plains in the middle of the county are awakening to the sight of hollowed-out cylinders of snow seemingly rolled into tubes overnight by some enterprising entity. But the maker of these eerie wonders turns out to be none other than the very forces of nature, according to weather scientists. It takes a precise combination of temperatures, winds, duration and flat space for these snow rollers, as the rare formations are called, to come into being.
“Snow rollers are an unusual meteorological phenomenon where large shaped snowballs form as wind blows the snow on the ground, causing the snow to form a ball and increase in size as it collects snow, similar to how snowmen are made,” the National Weather Service said in a statement. “Snow rollers have a more log-shaped appearance than the spherical shape of a snowman, and a snow roller may be hollow in the middle. Snow rollers can be as small as a golf ball, or as large as a 30-gallon drum, but they typically average 10 to 12 inches in diameter.”
Specific weather conditions are needed for them to form, the National Weather Service said. The ground must be swathed in a layer of icy, crusty snow that new snowfall cannot stick to. Then an inch or so of loose, fluffy yet wet snow must accumulate on top of that. Then there is the wind requirement: It must be gusty and strong enough to scoop out snow chunks and then consistent enough to roll them along. And lastly, temperatures must be freezing.
Snowfalls of one to two inches, along with 15- to 25-mph winds gusting to 35 mph did the trick in south central Nebraska and north central Kansas on January 9–10, the National Weather Service said. But conditions were similar enough across the U.S. to spark numerous sightings of the rare phenomenon nationwide, including Pennsylvania, Ohio, Michigan and elsewhere. Here are a few videos of the almost-spooky vista afforded by nature’s sculptures. The local ABC News station in Cleveland, Newsnet5, has posted hundreds of viewer photos, as well.