TRUMBULL COUNTY, Ohio - They might be called the winter version of "crop circles," except there is no mystery as to how they are formed. 

The first "snow rollers" were spotted over the weekend across areas of the Midwest. Several viewers sent photo's to the Storm Tracker 21 Weather Center of snow rollers in their yard or farm field.

"We've gotten a lot of pictures from not only North East Ohio but Western Pennsylvania.  A lot of pictures of open fields where the wind is particularly strong" said 21 WFMJ Chief Meteorologist Eric Wilhelm.

Wilhelm says snow rollers are the result of a rare combination or conditions.

"You need a few different circumstances to all come together, you need a lot of wind, which of course we had last night, and then you need a layer of wet snow on top of a layer of dry snow," Wilhelm said.

The dry snow allows the wind to push the wet snow and it rolls up leaving what often looks like a doughnut or swiss roll. They can be as small as a tennis ball or in some cases as large of two feet across, depending on how strong the wind is and how smooth the surface of the snow is.

Gravity can also assist snow roller formations if it's on an inclined surface.