Snowpack ¶

Snowpack consists of layers, rather like a cream slice. Each snowfall adds another layer. Snowpack therefore tells the history of a winter, from the oldest layers on the ground to the most recent on the surface. Some layers are so distinctive that weeks later we can link them back to specific weather events, e.g. a thick melt-freeze crust to a warm snap. Weak layers, such as snow-covered surface hoar, can increase the risk of avalanches. SLF observers therefore monitor their development closely. To improve avalanche risk forecasting, we are working to better understand and reproduce snowpack structure and the processes that occur inside it.

Changeable snowpack

Snowpack is a master of transformation: a person might sink up to their waist or walk over the top, depending on its condition. This is the result of continuous changes in the snowpack itself, most of which cannot be seen from outside. The temperature has a particularly big influence on these changes. The warmer the snow and the greater the temperature differences between the snow surface and the ground, the faster the snow layers change.

The wind also shapes the snow surface (Fig. 1). It transports the snow grains and grinds them down. It forms hard wind slabs. It blows snow from summits and ridges and fills up hollows and channels, rendering traffic routes impassable.