Background: on Sunday 10.02 there was rainfall/wet snowfall in Tirol up to about 1600-2200 m. Subsequently, temperatures plummeted. The rain turned to snowfall. Thereafter it was persistently cold.Tthe weather is currently subject to great temperature fluctuations each day. During the clear nights, the upper layers of the snowpack cool off significantly. The measurable temperature disparities between the previously moist snowpack surface and the cold layers of snow deposited on top of it cause a melt-freeze crust to form, on top of which are faceted crystals in some places. Reports have come in from Ausserfern about a striking weak layer of faceted crystals on a north-facing slope at 2150 m (Fallesinspitze).
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| Notable: warm temperatures initially, precipitation starts, initially rain then snow. Significant drop in temperature - those are the prerequisites for Danger Pattern “cold on warm” (dp.4) |
We are currently of the opinion that these are isolated danger zones. Focal point: very steep, shady slopes in a narrowly defined altitude band (the altitudes are still difficult to pinpoint; we assume approximately 1800-2200 m). What is significant is that the weak layer occurs only where sufficient amounts of bonded snow lie deposited on top of it. That means the regions where recent snowfall has been heaviest – Arlberg, Ausserfern, Northern Alps and Kaiser Massif. Due to the persistently beautiful weather the snow deposited on top of the weak layer will gradually lose its inherent tensions (provided winds do not transport it).
Upshot: a presumably isolated and small-spread problem on very steep, shady slopes which needs to be observed for a brief spell. The problem might disappear before long.
