The phenomenon is generally known as snow rollers. To me, many of these look more like rolls of paper towels or even hand muffs. Some have called them snow donuts or Swiss Roles. You may have seen them yourself, as they popped up overnight and appeared all over central Ohio, northeast Ohio and even Pennsylvania on the morning of January 27, 2014.
What are these strange things? They are quite simply rolls of snow. Smaller ones look just like a snowball rolled for a snowman, except instead of round like a ball, as they grow larger, they are generally cylindrical.
How do they form? We seldom see them as they require very specific weather conditions to form. Here are the criteria:
- The ground must be either a crusted, hard snow, or ice, so that the snow does not stick to the surface when it starts rolling.
- The ice or hard crust must become covered with a thin, loose, fluffy snow that is very near the melting point. In other words, good packing snow.
- There must be the perfect wind strong enough to start the ball rolling, and strong enough to keep it rolling as it grows, but not so strong as to tear the roll apart. A slight downhill, downwind slope helps and one source indicated that occasionally these will form on hills with only gravity and very little wind.
In my neighborhood of southeast Columbus, I found these in large, mowed fields after some opening that allowed the wind to build. Yet as I drove around, some quite large fields had none. In a couple of cases, they were toward the end of openings that actually funneled the wind into a narrower area, increasing the intensity of the wind. In fact, I had one small snow roller between my house and my neighbors house, where the wind whips around the buildings. So even the specific site location may be important, with lots of areas with no snow rollers, but others nearby covered with them.
As snow rollers build, the inner layer, which is the first to form and the weakest and thinnest, tends to get blown out, leaving the roll partially or even totally hollow in the center. Hence the shape become very much like a hand-warming muff but you would not want to try and warm your hands inside of one of these muffs!
When you first see these snow rollers, it almost looks like snow thrown up by a snow plow except they are generally well away from any roadway or sidewalk. You might expect these to more common much further north. However, I spent quite a few winters in Michigan, and two very cold winters in Minnesota and these are first snow rollers I've seen at all. Seeing these in central Ohio is a real treat and perhaps just a little bit of payback for the harsh winter weather to which we have been recently exposed. They are indeed a treat to enjoy.
