The snow. Most winter sports enthusiasts love it. And they feel personally betrayed when it delays or when it changes to rain when the mercury is still below zero.
Posted at 11:30 a.m.
The flake factory up there is much more complex than one might imagine. Various mechanisms cause it to produce powder snow or man-made snow. Or sleet.
“The temperature is the most important factor,” recalls André Cantin, of Environment Canada. But we are not just talking about the temperature near the ground. »
The various layers of the atmosphere have different temperatures, which can have consequences for the small snowflake that wants to land on the ground.
To produce the famous snowflake, you need humidity, but also what Mr. Cantin calls “a nucleus of condensation”; a small particle, a dust, for example. Droplets or ice crystals can then clump together.
Moisture condenses randomly. This explains the multiplication of snowflake shapes. There are basic structures, but it’s never the same.
André Cantin, from Environment Canada
We can find the classic structure, the famous six-pointed star, but also plates, sticks or needles.
PHOTO MARCO CAMPANOZZI, THE PRESS
The quality snow attracts off-piste skiers.
Snow in very cold weather
It is often said that it does not snow when it is very, very cold. Moreover, days at -25°C or -30°C are often beautiful sunny days. But we can have surprises. “It’s not necessarily snow that will fall, but what we call ice crystals,” says Mr. Cantin. It can even fall from a clear sky: it’s the humidity in the air that condenses. In the sun, we will see the ice crystals shine. We see this more in the northern regions, such as Abitibi, Lac-Saint-Jean, northern Quebec. It will happen in the South, but more rarely. »
When it is slightly less cold, between -15°C and -20°C, for example, the flakes look more like sticks. This shape causes them to “pack” more on the ground than the six-pointed snowflakes. And since the humidity is lower in the atmosphere, the precipitation does not last. We are then left with weak accumulations of two, three or four centimeters.
Alain Laroche, responsible for trail maintenance, grooming and snow production at Stoneham, confirms that it can sometimes snow when it is very cold. “We had a good example this year: several times, we were in -20°C and we still had snow, he observes. It’s very dry snow, very light. »
The snow he prefers is that which falls between -8°C and -10°C. “It’s snow that gets compacted, that works,” says Mr. Laroche.
Snow that is too dry, too cold, has no volume, it does not compact. A little too wet snow is difficult to work, it sticks.
Alain Laroche, from Stoneham
Ah, that famous wet snow, the one that makes beautiful snowmen… and that forms heaps under crampons, snowshoes, cross-country skis. It forms when the temperature approaches the freezing point. It’s its high water content that allows it to stick and make good snowballs that prankster hikers will throw at carefree comrades.
PHOTO HUGO-SÉBASTIEN AUBERT, THE PRESS
Wet snow makes for beautiful snowmen, but winter sports enthusiasts tend to prefer drier snow.
The hated words
Obviously, the words “freezing rain” should not be used in front of a winter sports enthusiast. This type of precipitation occurs when a layer of warm air is positioned between the very cold layer of the upper atmosphere and a layer of cold air, near the ground. The precipitation, which first fell in the form of snow, thaws while crossing the intermediate warm layer and fails to refreeze in the lower cold layer. This very cold rain eventually freezes when it hits a surface. Obviously, the effect on a cross-country ski trail is not the happiest.
If the layer of cold air near the ground is thick enough, the drops can refreeze before reaching the ground and thus take the form of sleet. “It’s like a piece of ice, but it’s much smaller than hail in summer,” says André Cantin.
Once on the ground, the snow still undergoes several modifications. Over time, it compacts, it becomes denser. The flakes gradually lose their jagged shape and become smaller, rounder. The snow that accumulates on top speeds up the process, as does a good wind. Snow compacted by the wind is also the ideal material for building an igloo: with a snow saw, you can cut beautiful, very solid blocks that do not crumble and that you can position on top of each other.
Skiers and snowshoers will prefer powdery snow, but that doesn’t prevent them from continuing to have fun at the end of the season, when the snow melts under their soles.
“People like spring skiing even if it’s more difficult,” observes Alain Laroche. But it’s more to enjoy the sun, not the snow. »
Suggested video
Skim the Eiger
Thanks to his wingsuit (wingsuit), Daniel Darby follows the crest of the Eiger, in the Swiss Alps, and comes close to the Mittellegi refuge.
digit of the week
1927
This is the year that the Canadian National organized the first snow train, between Montreal and Shawbridge.