Here's a weather phenom that appears almost mysteriously, as if someone started building a snowman and then left the rolled balls of snow in the field. Closer inspection shows no footprints in the newly fallen snow. What are they? They're called snowrollers
Hi, I'm Bryan Yeaton and this is The Weather Notebook/
Snowrollers are molded by strong, gusty surface winds. They look like a rolled-up carpet or small muff and are often hollow. They can be as small as a golf-ball or as large as a 30-gallon drum,.but usually snowrollers are about 10-12 inches in diameter and a foot wide.
Snowrollers appear in open fields under specific weather conditions, often present following the passage of a strong winter storm.
First, the ground surface must have an icy, crusty snow, on which new falling snow cannot stick.
On top of this, about an inch of loose, wet snow, the sticky kind that makes good snowballs, must accumulate. The optimum air temperature appears to be around freezing, from 28 to 34 F.
Finally, a gusty and strong wind, usually 25 mph or higher, is needed to build the snowroller.
Snowroller formation begins when the wind scoops chunks of snow out of the snowfield, they roll, bounce and tumble, like snowy tumbleweeds, downwind. Additional snow then adheres to this seed, and the snowroller grows until it finally becomes too large for the wind to push, leaving behind a characteristic track linking the snowroller's origin to its final resting spot.
Because snowrollers have not been widely reported in the past, many consider them a rare event. But across North America, their formation is likely frequent. In fact, a snow-covered field may sport hundreds of individual snowrollers seemingly waiting for someone to stack them up.
Thanks today to contributing writer Keith Heidorn who watches the weather in Victoria, British, Columbia. For more on Snowrollers, go to our website at mountwashington.org.
Pictures of snowrollers