Wind and avalanche danger

Even before the snow reaches the ground to form our beloved powder, it is often already changed in the air. The wind shatters the snow crystals, which fall to the ground as fragments. Here, the strong ground wind can transport the "debris" further and drift snow is created. Even if this snow looks very similar to powder, it reacts completely differently to loads.

1. Transformation by wind and pressure

Never forget: wind is the master builder of avalanches!

Drift snow is brittle and reacts to pressure with fractures, as it can only compensate for stresses very poorly. Even a fair weather storm can transport large amounts of drift snow to the lee side. Snow plumes on ridges and summits always indicate intensive snow drifting. Real powder snow disintegrates on a snow shovel or avalanche shovel even with a slight vibration.

Bound, i.e. wind-blown powder snow can be recognized by the fact that snowboard or ski tracks look razor-sharp. With ski tracks, a "ridge" can remain between the skis. Fresh drifting snow deposits are always suspicious of snow slabs. Be sure to ski around them! They are taut traps lying in wait for prey.

2. degrading transformation

As soon as the fresh snow has reached the ground, it begins to change as a result of degradation. You can recognize the degradative transformation by the fact that the snow cover settles and becomes denser. This process takes place through the decomposition of the complex snow stars. The fine branches break off or are drawn in by water vapor transport and re-accumulate in the middle of the crystals. The hexagonal stars become small spheres. This considerably reduces the air content of the snow cover. The snow cover solidifies as the grains touch each other in many places. When it is very cold, the transformation takes place very slowly; when temperatures are mild, it is much faster. For freeriders, this means that the risk of avalanches remains high for a long time after a snowfall and persistently cold temperatures, whereas the snowpack settles more quickly in mild temperatures and the risk of avalanches decreases. The result of the degrading transformation is round, grainy old snow that is very dense and stable. Actually, we could now plow through all the slopes to our heart's content. But unfortunately, there is a process in the snowpack that destroys the strength of the degrading transformation.

3. Constructive transformation - floating snow formation

After some time, a temperature difference builds up in the snow cover between the very cold snow surface and the relatively warm ground. The reason for this is that the ground radiates heat, while the snow surface continues to cool down on cold nights. As a result, the snowpack becomes warmer and warmer with increasing depth, similar to a mine. The ground beneath the snow cover has a temperature of + - 0° C. Like the snow walls of an igloo, the snow cover insulates so strongly that the difference between the warm ground and the cold snow surface becomes ever greater. If the temperature difference is large enough, the old snow on the ground begins to evaporate. The water vapor rises and freezes again in colder layers of snow. There, new, large and angular crystals are formed, so-called cup crystals or floating snow. This process is also known as deep frost formation. Cavities form in the layer of snow on the ground. If there is a strong build-up transformation in high winter, the later snowfalls can only bond poorly with the old snow. The snowpack foundation that has been built up and transformed often remains weak for the rest of the winter and the floating snow represents a dangerous potential avalanche slide path.
After long (cold) periods of good weather in high winter, the danger is often particularly great and can last for several weeks, as all types of frost only bond poorly and very slowly with the overlying snow. Winters with lots of snow are less dangerous - for freeriders - than winters with little snow.