BRIGHAM CITY — Della Burwell noticed something strange on her way to work Tuesday morning.
The lawn outside of the Utah State University Brigham City campus entrance was full of snowballs, but there were no footprints in sight.
"It's just like there's a bazillion of them out here and on the other lawn as well," she said," pointing toward the field in a video posted to Facebook by USU Brigham City Tuesday.
After quick research into it, the university employee found that she had stumbled across a rare meteorological phenomenon known as "snow rollers."
The same phenomenon was reported to KSL by LuAn Johnson, who spotted it at the Eagle Mountain Golf Course, also in Brigham City.
So what are snow rollers? They're balls of snow created by wind. They're a phenomenon that only happens when the mixture of moisture, snow, temperature and wind is just right, according to the National Weather Service. The weather service classifies it as "rare" because the conditions have to be precise for it to happen.
"These delicate formations need just the right mix of moisture, snow, wind, and temperature. The snow has to be a light dusting, sticky enough to adhere to itself but on a surface that it won't cling to," the agency wrote about the phenomenon. "The wind has to be strong enough to encourage these mounds of snow to curl up and form their signature loop, but not so strong that the whole thing gets blown apart. Alternatively, the snow could be on a hill and gently roll downslope to form the same shape."
David Phillips, a senior climatologist for Environment Canada, told the CBC in 2018 that winds have to be at least 28 mph to trigger the snow to roll.
The weather event also has other names, such as "wind snowballs," "snow donuts" or "snow bales," according to National Geographic.
Brock Burghardt, a meteorologist for the National Weather Service, said the weather event is much more likely to happen in Utah's mountains than in the valley like what happened Tuesday. That's because of gravity.
"Snow rollers are quite common in the mountains, especially when we have a wet, heavier snow that has fallen or snowpack that's been heated by the sun and it kind of becomes a wet, heavier snowpack," he told KSL NewsRadio.
What was reported in Brigham City was something that meteorologists don't see "on a regular basis."
In this case, it was likely a mixture of a weird sequence of weather over the past few days. Burghardt explained that the warmth in Utah over the past few days likely heated the ground. Then there was the snow and strong cold front that passed through Monday night into early Tuesday morning.
"The snow fell on a warm ground, which probably resulted in it becoming kind of this denser, wetter snow," he said. "And basically the wind did the job of what gravity would usually do on a mountain slope. The wind kind of just pushed it along and because the snow had melted and it was a little more wet and dense, it was able to kind of snowball on itself."
Tiffany Mansfield, another USU Brigham City employee, also came across the peculiar weather event Tuesday. In a second video posted to Facebook, she hoisted up one of the rollers to allow people to see the hole in the snow created from the snow folding on top of itself.
"You can see the trail where the wind rolled this," she said, pointing to a streak in the lawn behind the roller where there was no snow.
As for the storm that passed through Monday night into Tuesday morning, the National Weather Service's Salt Lake City office reported that the Cache Valley northeast of Brigham City received as much as 4 inches of snow.
As for other parts of the state, the weather service also issued a wind advisory for most central and southern Utah from 2 p.m. Tuesday through midnight, ahead of a storm system expected to pass through. The agency reported southwest winds will range from 20 to 30 mph with possible gusts of 40 mph Tuesday afternoon into the night in those areas.
Contributing: Dan Bammes, KSL NewsRadio