These strange-looking images of rolled snow above are called “snow rollers” and yes, they are formed naturally! A rare occurrence, snow rollers only form during limiting conditions.
The National Geographic describes this weather phenomena as the weather equivalent of tumbleweeds. This hints that wind is what pushes the snow into these rolls. But why doesn’t this happen more often? Snow rollers only form when weather conditions have “the right mixture of moisture, snow, wind, and temperature.” The National Geographic further describes these conditions as there having to be a layer of ice with a layer of light snow on top and it must be wet enough for the snow to stick to itself. Also, winds must be around 30 mph.
Not only can snow rollers be formed by wind but, in some cases they form, by rolling downhill. As a snow rollers accumulate snow, it leaves a track behind, showing where they’ve traveled. The formation of a snow roller is very similar to the way snowmen are made. Some have compared snow rollers to the giant snowballs that roll downhill in a cartoon. They have been referred to as “snow donuts” or “snow bails”.
Some snow rollers form with a hollow center and some are packed in a swirl, similar to a cinnamon bun! Here are some pictures of the two different forms.
(A hollow snow roller.)
(A packed snow roller.)
To learn about documented snow roller events, The National Weather Service archives a few articles regarding the phenomenon.These articles include the event of December 2008 in eastern Washington and the event of March 2009 in Idaho. Some pictures the National Weather Service posted of these snow rollers can be seen below.
(Picture from the December 2008 event.)
(Picture from the March 2009 event.)
Snow rollers are just nature's anomaly. They are never dangerous, just a rare but pretty weather phenomenon.
Credit: The National Geographic and The National Weather Service
© 2019 Weather Forecaster Brittany Connelly