They are called snow rollers and they look like something out of a Stephen King travel guide to the Arctic Circle -- weird, cylindrical snow formations created in the middle of nowhere without the benefit of human touch.
And the sight of them provides more evidence of the strange winter weather that's sweeping the country, threatening snow in the Sun Belt, thrusting Minnesota temperatures even further below zero than usual and menacing the Super Bowl during its own rare appearance in foul-weather country.
The "strange phenomena," the agency says, are created under very specific conditions: "The ground surface must have an icy, crusty snow, on which falling snow cannot stick. About an inch or so of loose, wet snow must accumulate. Gusty and strong winds are needed to scoop out chunks of snow."
Once the "seed" of the snow roller is formed, the weather service said, it begins to roll, pushed by the wind, unimpeded.
"It collects additional snow from the ground as it rolls along, leaving trails behind it," the agency said during an Illinois outbreak in 2003. "The appearance is similar to building snowmen, except the snowball is more log-shaped rather than spherical, and many times they are hollow."
And did we mention that there are no footprints?
Snow rollers range from golf-ball-sized to as big as a 30-gallon-drum, and they've been sighted all across the Internet on Tuesday, as the weather service forecast a "rare winter storm expected to impact the gulf coast, Southeast and southern Mid-Atlantic."
A so-called wintry mix of freezing rain, sleet and snow is expected from Louisiana to Florida and upward into the Carolinas, causing local officials to go on high alert.
The College of Charleston is shut down until Thursday, as the campus braces for bad weather. The school's website warned that all classes, labs and activities are canceled "due to expected ice and snow" and said that "all non-essential employees are excused from reporting to work."
The Mississippi Emergency Management Agency website warns that "snow and ice are expected to hit south Mississippi hard, [with] frigid temps statewide." The Associated Press reports that some schools and government offices in the Magnolia State are already closed.
The MEMA website laid out the warning signs of
"This is a very dangerous situation because snow and ice are very rare for extreme southern Mississippi," said MEMA Director Robert Latham. "We need everyone to have an emergency plan together for this."