SnowFlurry 1 2022/23 | Early winter - What you should be aware of

The first snowfalls

The weather situation should be monitored in early winter, even and especially if no avalanche bulletin has yet been issued. The first snowfalls of the season are usually of no interest for skiing yet, but they form the basis for the further course and development of the snow cover. They have a decisive influence on whether or not an early winter old snow problem develops. In the worst case, such an old snow problem can accompany us throughout the winter. It is therefore advantageous to keep an eye on developments from the first snowfalls!

Special attention must be paid to this:

At what altitude and exposure does the snow remain, where does it melt again?
Is there a blanket of snow or just a carpet of patches (no continuous snow cover)?

Webcams or snow exploration tours on foot or with snowshoes are a great tool for this.

The transformation processes are particularly strong in early winter, when there is still little snow. This is because the first snowfall is often followed by a longer period of fine weather with 2 typical scenarios:

1) In sunny, mild weather, most of the snow that has fallen melts again. In principle, this is a good thing, as no floating snow can form when there is no snow. This makes it less likely that an early winter old snow problem will develop. However, at high altitudes (2000-3000m) and high alpine (from 3000m), primarily on steep north-facing slopes, the snow tends to stay put even then, as it is colder and, depending on the exposure, there is no more direct sunlight.

2) If, on the other hand, it is sunny with cold temperatures, the snow cover begins to radiate. The drier the air is, the more this process takes place. The radiation cools the snow surface considerably. As a result, a large temperature difference can form over a few centimetres, which greatly promotes the build-up transformation. The molecules scurry between the individual snow crystals and work at full speed to produce early winter floating snow. Depending on how strongly the build-up transformation works and how long the fine weather phase lasts, loose layers of angular crystals, facets or cup crystals (floating snow) are formed. This can affect the snow surface, individual layers, but also the entire snow cover.

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Early winter floating snow foundation

Stefanie Höpperger

The temperature gradient is crucial

In the high mountains, where there is often more snow early on, weak layers tend to form in the middle part of the snow cover and on the snow surface. At lower altitudes, the entire snow cover is often affected. The snow temperature measured at the snow surface and on the ground remains the same, regardless of how thick the snow cover is. However, the temperature gradient, i.e. the change in temperature per centimetre of snow depth, is much greater at low snow depths. The greater the temperature difference over a few centimetres, the stronger the build-up transformation works. The lower the snow depth, the faster the entire snow cover is transformed.

Where there is no board, there are no avalanches. But: risk of injury!

Although the loose, unbound layers of snow form a perfect weak layer, this does not necessarily mean that there is an avalanche risk. As we know, three ingredients are needed to trigger an avalanche: A weak layer, a board (bound snow) and a sufficiently steep slope gradient.

The loose snow can of course be easily transported by the wind and form drift snow packs that are prone to disruption. Even bound fresh snow (which has fallen under the influence of wind or warmer temperatures), which comes to rest on the loose layers, can quickly form the base for a possible avalanche.

However, if there is no base of bound snow in a thin, completely built-up snowpack, the risk of injury is more problematic than the risk of avalanches. This is because the loose snow does not form a stable base and you sink through to the ground. Stones and crevasses are often only visually concealed, and you sink into the mountain pines and alpine roses or get stuck. That's why, depending on the ground conditions, skiing in early winter is simply not yet possible, even if some people keep trying. The risk of injury is high. In the best case scenario, you "only" ruin your skis.

It is therefore important to know the surface in summer! With little snow and a loose snow cover, halfway sensible skiing is only possible away from the prepared pistes on meadow slopes or in glaciated terrain. On glaciers, however, it is essential to be aware of the risk of falling into crevasses!

The nature of the ground also says something about whether the snow cover and a possible weak layer is only present in places or over a large area. This is because a variable subsoil, which is subdivided by mountain pines, alpine roses or boulder terrain, for example, has the considerable advantage that a weak layer is not connected over a large area, at least when there is little snow. A fracture can therefore not propagate over large areas and avalanches are not too big.

Thin early winter snow cover in Sellrain

Stefanie Höpperger

The second snowfall

If a period of fine weather is interrupted by further snowfall, the situation often becomes critical. In order to assess whether there is a possible avalanche risk due to the problem of old snow, you should know the crystal forms on the snow surface and also the existing weak layers in the snowpack. And preferably before they are snowed in by new snowfalls! Of course, it is also possible to determine the weak layers after the snowfall by analysing the snowpack. However, if you don't have them on your radar, it may be too late before the snow profile is created, as you have already triggered an avalanche!

To summarise:

Keep an eye on the snow cover from the first significant snowfall:

What is the exposure and altitude of the snow?
Is the snow cover contiguous or not?
What kind of subsoil (stones, meadows, mountain pines, alpine roses, etc.)?
Amount of snow?
Condition of the snowpack: What crystal forms are in the snowpack and on its surface?
Patience until there is enough snow to undertake meaningful ski tours in the terrain!