28 January 2021
Seven years ago this week open fields in eastern Ohio and western Pennsylvania were graced with a rare winter phenomenon. Snow rollers!
Snow rollers are delicate snow balls made by the wind that look like snow bales or jelly rolls.
They can only happen when all of these weather conditions are met.
- First an icy layer(*) forms on top of old snow that new snow will not stick to.
- Then, a thin layer of wet, loose snow falls on the ice.
- After the wet snow falls, the wind blows just hard enough to start the balls rolling without destroying them.
- Snow rollers stop when they are too heavy for the wind to move.
The center of a snow roller, the first layer, is fragile and disintegrates easily. Even before a snow roller becomes hollow it is too fragile to pick up.
This year it’s too warm and we have don’t have much snow so I doubt we’ll see snow rollers any time soon.
Read about 2014’s rare occurrence in this vintage article: Nature’s Snowballs.
(photos from Wikimedia Commons; click on the captions to see the originals)
(*) In other climates snow rollers can form on top of powder snow and can be triggered by a snowball falling on a steep hill.