Giant nature-made snowballs have been spotted across Pennsylvania and Ohio this week, mystifying onlookers unfamiliar with the meteorological phenomenon.
The rare snowballs, called snow rollers, are formed when gusty winds roll snow along the ground, similar to how snow might be rolled to create a snowman. The result, however, is typically cylindrical and hollow.
Snow rollers do not form after every winter storm because they require specific conditions.
First, the ground must be covered by a layer of ice, then have wet, loose snow on top, with a temperature near freezing. Next, winds need to be strong enough to get the snow rolling, but not too strong that they dismantle the weak inner layers of the roller.
Gusty winds after a big storm help to create snow rollers like this one found in Stow, Ohio. (Facebook Photo/Angela English)
An open snowy field provides a conducive environment for the formation of snow rollers, like these found in Lexington, Ohio. (Facebook Photo/Benjamin Lee)
Snow rollers have been being reported across parts of Ohio consistently over the past week. (Facebook Photo/Mike Fuerst)
Snow rollers can vary in size, depending on the strength of the gusting wind, the type of snow and other factors. (Facebook Photo/Mike Fuerst)
Gusty winds Monday morning helped create these rollers in northwestern Pennsylvania. (AccuWeather Photo/Jordan Root)
Rollers were spotted across Crawford County, Pa., this week. (AccuWeather Photo/Jordan Root)