“Snow rollers” observed near Long Valley South Dakota
The relatively rare meteorological phenomenon creates its own snowballs on flat surfaces or down hillsides, that can range as small as a tennis ball, to the size of cars
LONG VALLEY, S.D. – Snow rollers, snow bales, snow donuts, snownuts, and wind snowballs – there are many names for this phenomenon, but few people actually bear witness to this meteorological oddity in their own backyard.
Dave Ohrtman captured a field of them on camera last Thursday night near Long Valley in Jackson County
Dave Ohrtman – Long Valley South Dakota.
Conditions have to be -just right- for snow rollers to form.
- You need a relatively thin layer of wet, loose snow that has good consistency to make snowballs
- Under the snow, you need a smooth surface that takes away the obstacle of friction. Ice is an excellent example, or a flat driveway.
- You need winds that are strong enough to initiate the snowball, and then keep it rolling. If the winds are too high, it destroys the snowball, so it has to be JUST RIGHT.
- Gravity can do much of this work on hillsides, and so they are more commonly seen on hills and embankments. Snow rollers can end up the size of cars or larger on these hillsides, sometimes ending up on roadways appearing as a giant rolled-up carpet, or a giant cinnamon roll!
Snow rollers also tend to have a hole in the middle and are often hollow, as the finer snow used to initiate the snowball in the middle gets eroded by the wind – leaving the large donut behind.
A special thanks to Dave Ohrtman for sending these in
