“Snow rollers” observed near Vale, SD Tuesday morning
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 sometimes the size of cars
Snow rollers, snow bales, snow donuts, snownuts and wind snowballs – there are many names to this phenomenon but few people actually bear witness to this meteorological oddity in their own backyard. The Schubauer’s woke up this morning just southeast of Vale, SD to a field of these self-propelling snowballs Tuesday morning.
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 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.
Conditions Tuesday morning near the Black Hills match perfectly with the conditions required for these to form, with a fast moving snow band dropping a thin layer of wet snow followed by some good sustained winds.
It was pointed out to me that I can’t *prove* that it wasn’t gnomes or little elves pushing these things around… And I will admit they tend to be more frequent during the Christmas Holiday…
A special thanks to Allison Schubauer for sending these in – what a pleasant surprise this morning!