Why Are Ski Runs Groomed?

by Simon Knott | Updated: October 27th, 2022 |  Skiing Articles

We have all looked out of our chalet or hotel windows at night to see the headlights of snowcats (piste machines), as they roam the runs throughout the night at impossible angles. What are they doing? It can’t just be cosmetic.

Runs are groomed to ensure the snow is kept in the best condition, stopping the formation of ice and moguls. If snow cannons are used on the run to make artificial snow it is the snow groomer that needs to spread this snow away from the canon and across the piste. Grooming also gives the snow a better definition because of the ridges. This gives skiers a better grip and makes it easier to see the contours of the piste.


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How Does Grooming Change The Snow?

When new snow falls it is exceptionally light and as the flakes stick together, they trap a lot of air. As the snow is not very dense it cannot support much weight.

Over time the snow settles and gradually hardens but this compacting can take up to 2 days. Part of the process of grooming the snow helps to level out and compact this light top layer into something more substantial.

Snow Grooming

How Does Grooming Stop The Formation Of Mogul Fields?

At the end of a skiing day, skiers will have churned up the snow on the run. If it has also been sunny this will have also softened the snow, leaving the piste with an uneven surface with ridges and gullies.

If this process was allowed to continue without grooming, then larger and larger moguls will form. Each successive skier follows the tracks of the previous skier around each mogul, creating deeper tracks and larger moguls. So, moguls are an entirely man-made feature.

Skiing down a mogul field is quite a technique and a lot of fun but if all runs were like this it would quickly become tiresome. Snow groomers (piste bashers in the UK) use their machines to chop the top half of each mogul off. This snow is then chopped and pushed into the valleys between moguls, resulting in a once more, smooth run.

Does Artificial Snow From Snow Canons Help The Grooming?

Early and late in the season snow canons are often used to artificially create snow for the runs. A combination of water and air under pressure is fired from the nozzle up into the freezing air. This creates tiny droplets, which freeze instantly as they fall to the piste as tiny snowflakes.

Generally, the canons can’t disperse the snow over a wide area, leaving it to build up around the canon. It is then the Snow groomer’s job to spread the new snow across the piste and compact it.

What Makes The Pattern On A Groomed Run?

It’s been proven that grooming runs lead to fewer accidents on the slopes. The stripes of the grooming pattern, called corduroy, help skiers navigate the run by creating definition.

This is particularly useful on overcast days and on patches of the piste that are in shadow. On days like this, the definition of shadows is poor, so it is difficult to work out the height of the terrain. Wearing yellow goggles or sunglasses will also help with definition on days like these.
A groomed run will also give the skier better grip and any ice, which has formed on the run, will be broken up making for safer skiing.
With the first snowfalls at the beginning of the ski season, it’s the run basher’s job to spread the available snow to create the runs. With each successive snowfall, new layers are gradually built up.

The aim is to create as much depth as practical to extend the skiing season into spring when the sun will quickly melt the snow. The physics of snow is complex but over time the lower layers come harder and more compacted from the weight of new snow on top.


Why Do Snow Groomers Just Work At Night?

It is only possible to work with the run machines at night-time when the runs are closed to skiers. It’s obvious the combination of heavy machinery and fast-moving skiers isn’t a good mix! Night-time is also the best time to condition the snow. After grooming the runs there are still night-time hours for the snow to harden before skiers return.

Snowcats first evolved at the beginning of the 1960s, as skiing became a more mainstream tourist activity. Prior to the first heavy diesel machines, teams of horses pulling rollers was the only way to prepare the runs.

How Does A Snowcat Machine Work?

The snowcat has a snow plough at the front, which is used to plough and drag the snow, evening out the surface. At the back, it has a unit consisting of a rotating blade, which breaks up hard clumps of snow. At the same time, the caterpillar tracks lend a hand breaking up the lumps.

After a particularly heavy fall of snow, a pressure roller is also used to compact the snow surface. Lastly, at the back of the machine is a pressure pad for the final packing down of snow. A long comb pushes down into the surface, making it suitably firm and creating the corduroy effect at the same time.

On some exceptionally steep sections of run, the machine is tethered to an anchor point by a strong cable higher up the mountain. Winching this cable in and out enables the driver to negotiate the steep terrain easily.

Learning the process of snow grooming is quite involved and a three-year training programme is not unusual.

Skiing communities and companies are fully aware of their environmental responsibility. Their very livelihood depends on it! With no snow, they don’t have a business. With this in mind a German company, Pisten Bully, has taken the plunge by inventing a fully electric rechargeable snowcat. A 6½ hour charge will leave it capable of working for up to 3 hours on the runs with no emissions.