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SnowFlurry 4 2019/20 | What happened to the snow cover during the long period of good weather?

Clear nights favor the restorative transformation

by Stefanie Höpperger • 12/14/2019
Despite the warmer temperatures in the fine weather phase, the snow surface on shady slopes remained mostly loose. On the other hand, slopes exposed to strong sunlight - especially at lower altitudes - became damp on the surface and a cover could form due to cooling.

Clear nights allowed the snow surface to cool down considerably, which favored the accumulating transformation. Angular crystals have formed in the upper 20 cm (fresh snow around 2.12.) of the snow cover. That's why it crunched so nicely when skiing recently, as if you were skiing on sugar.

This layer poses a certain problem after the fresh snowfall on 9 December and the following days. The bound fresh snow or drift snow came to rest on soft, angular layers and thus formed a weak layer.

Snow profile Längental from 7.12.19, 2133m, NW


Rounded crystals lie close to the ground. This snow originates from the end of October - beginning of November.

The low temperature gradient in the lower layers favors the decomposing transformation. This means that the crystals transform more and more into round, small grains and create a good base. The layers close to the ground are generally negligible in this profile, as they would hardly be disturbable with a snow thickness of 150 cm.


The following layers are from the precipitation in mid-November and are very compact.

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Green + yellow + grey

The next two layers were transformed during the fine weather phase at the end of November and presumably also after the snowfall at the beginning of December due to the high temperature difference in the upper layers.

A light cover formed on the surface of a fairly warm snow surface (fractured snow period), which then cooled down considerably on clear nights. This resulted in a high temperature difference in the layers close to the surface, which favored the build-up transformation - the formation of angular crystals. The lid is also in the process of undergoing a constructive transformation. This can be recognized by the fact that angular crystals are mixed with the round grains.


A very soft layer (can be penetrated with a fist) of angular and felt-like crystals is located above the cap, from the fresh snow at the beginning of December. The cold snow surface and the high temperature gradient slows down or stops the decomposing transformation and favors the building up transformation. As a result, even after several days of fine weather with warmer temperatures, we still find felted crystals, which would otherwise undergo a very rapid decomposition transformation.


Wind cover, drift snow.


A thin layer of angular crystals can be seen on the surface, which was caused by the above-mentioned radiation on clear nights.

The yellow layers are responsible for the ECTN result. A partial fracture occurred in both weak layers.


In total, the snowpack was compact at the time of the profile, with only isolated, rather negligible weak layers in the layers close to the surface. After the precipitation of the last few days, these layers should be kept in mind in addition to the fresh drift snow, as well as the angular crystals that formed on the former snow surface during the fine weather period.

This article has been automatically translated by DeepL with subsequent editing. If you notice any spelling or grammatical errors or if the translation has lost its meaning, please write an e-mail to the editors.

Show original (German)

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