Persistent weak layers
- Above treeline
- Size
- 3
Stability: poor · Frequency: some
Weakly bonded old snow requires caution.
Stability: poor · Frequency: some
Weakly bonded old snow requires caution.
Single winter sport participants can release avalanches in some places. Avalanches can in some cases penetrate deep layers and reach large size. Avalanche prone locations for dry avalanches are to be found in particular on steep west, north and east facing slopes above the tree line, in isolated cases also on steep shady slopes in areas close to the tree line. The avalanche prone locations are covered with new snow and are therefore barely recognisable, even to the trained eye. Defensive route selection is appropriate. As a consequence of warming during the day and solar radiation individual wet loose snow slides are possible as the day progresses, especially on very steep sunny slopes.
Above the tree line snow depths vary greatly, depending on the infuence of the wind. The snowpack will be subject to considerable local variations at elevated altitudes. The somewhat older wind slabs of the last few days are lying on top of a weakly bonded old snowpack in particular on west to north to east facing aspects above the tree line. This also applies in isolated cases on south facing slopes in high Alpine regions. The weather conditions will foster a stabilisation of the snowpack. Steep sunny slopes below approximately 2600 m: As a consequence of mild temperatures and solar radiation a crust will form on the surface. Low and intermediate altitudes: The old snowpack is moist and its surface consists of loosely bonded snow lying on a crust that is strong in many cases. This applies in particular on shady slopes.
Weakly bonded old snow requires caution.
Bulletin data: Avalanche Warning Service Tirol, avalanche.report (CC BY 4.0)