Rolling Snow Off the Lawn: The Snowball Trick and the Science Behind It

Instead of reaching for a shovel, Joshua Jordan knelt in his yard, pressed a small roll of snow together with his hands and started pushing. The roll grew like a carpet being rolled up, peeling the snow away in one layer and leaving a clean strip of green lawn behind it. His YouTube clip, titled "Snow shoveling West Virginia style. Life hack!", spread across US news sites in early 2015, when local TV stations and morning shows picked it up as the snow trick of the winter.

Watch the snow-rolling video

The trick takes only a few seconds to understand. Jordan starts with a snowball about the size of a cantaloupe, lays it on the snow and pushes it forward. Every turn wraps another band of snow around the roll, and within a few metres it is big enough to push standing up. Behind it the lawn appears almost completely clear.

Why the snow rolls up like a carpet

The method works only with the right kind of snow, the same "packing snow" that makes good snowmen. Two things have to come together:

• Sticky, wet snow. When the temperature at the ground sits near or just above freezing, snowflakes partly melt and carry liquid water. That water acts like glue, so each new layer bonds to the roll. Cold, powdery snow falls apart instead.
• A clean break from the ground. The snow has to stick to itself better than it sticks to the surface below. On grass that is still unfrozen, or over a thin icy layer, the whole blanket lifts away in one sheet.

Wet snow also holds a lot of water. AccuWeather notes that 5 inches of powder may melt down to about half an inch of water, while the same depth of wet snow can hold up to an inch, roughly twice as much. That extra weight is why the roll grows heavy so quickly.

Snow rollers: the natural version

Nature performs the same trick on its own. Snow rollers are cylinders of snow that form when the wind pushes chunks of wet snow across an open field, gathering more snow as they tumble, just as Jordan's roll does. Meteorologists describe a fairly precise recipe: an older, icy snow surface, a fresh layer of wet snow on top, air temperatures near or slightly above freezing, and winds of roughly 25 to 30 mph (40–50 km/h). The icy layer underneath keeps the fresh snow from sticking to the ground, so it can keep rolling. On a slope, gravity alone can start them.

Snow rollers are rare and usually short-lived, and fields of them have made local news in places such as Idaho, Michigan and Alaska. Finding them in the morning, with tracks showing where each one rolled, is a real winter treat.

Tips for trying it yourself

• Test the snow first. Squeeze a handful. If it forms a firm ball, it will roll. If it crumbles, keep the shovel.
• Start small and low. Crouch down, form a tight starter roll, and push it along the surface.
• Roll in straight lines. Work in strips, then use the finished rolls as the base of a snowman or snow fort.
• Use it on grass. Lawns work best. On paths and driveways, wet snow often leaves a slick, compacted film that still needs clearing.

Give your back a rest when the roll gets big. Wet snow is heavy, and pushing a large roll uphill takes real effort, so stop while it is still easy to move and start a new one.

Related reading

• Ice shells left by parked cars
• Faust’s lettering on New York cars

Sources