What Are Those Weird Snow Mounds?
Driving along the road in winter, if you’re somewhere there’s snow, you may have come across a curious formation sitting on a field. Called a snow roller, it’s basically a snowball made by the wind. Snow art, constructed by nature.
You can see them at times dotting large fields of uninterrupted snow. To me, they look like the winter version of a hay-roll, but they’re not that big.
According to the National Weather Service, a “snowroll” or “snow roller” is a rare meteorological incident. It happens when wind blows chunks of snow along the ground, forming large, naturally-occurring snowballs.
How Are Snow Rollers Formed?
When you combine cold temperatures with snow and wind, and then place them in an ideal environment, you get snow rollers. Snow donuts, as people also know them, only occur under very specific winter weather conditions.
Basically, the wind picks up a small chunk and pushes it along, collecting more and more snow. These strange snow formations are the cold weather equivalent of tumbleweeds. As the wind pushes snow across the ground, it forms into a hollow cylinder.
The larger of these unique formations can be a few inches wide, and travel a couple feet. The balls leave trails behind them, and stand out against an otherwise flat field of snow.
Snow Rollers Require Very Specific Conditions
As mentioned, the phenomenon of snow rollers requires the right mixture of moisture, snow, temperature, and wind. In addition to these elements, the existing snow on the ground also needs to be a certain way.
For a snow roller to form, there needs to be a light dusting of snow on top of an icy layer already sitting on the ground. Then there’s the layout of the land to consider. It’s important that there are no protruding plants or objects. The snow rollers need a pathway to form.
The dusting of the snow also needs to be just wet enough so it can adhere to itself… but not get stuck on the ground. Further to this, the wind needs to be around 30 miles per hour to make the snow form its cylinder.
On top of this, the temperature must be three to five degrees above freezing. No more, no less. This temperature is ideal because it allows the rolling snow to form, but doesn’t let it melt.
Because of this, you see these neat little rolls dotting the horizon, and making you marvel at all the wonders of nature.