Weisseck, Muhr Valley

Slab avalanches in the snowdrifts can fracture down to deeper weak snowpack layers

The fresh fallen snow is being heftily transported. Inside the fresh snow, short-lived weak layers are forming near the surface. At high altitudes the fresh snow is falling atop a generatlly wind-compressed snowpack surface where the bonding is good. In wind-protected zones the old snowpack surface can be loosely packed and thus, constitute a weak layer. Deeper down inside the old snowpack fundament there are soft layers lodged between hard layers at high altitudes. At low and intermediate altitudes the old snowpack beneath the fresh fallen snow is melt-freeze encrusted. The snow base evidences no marked weak layers. However, the entire snowpack can start to glide over steep rock plates or grassy slopes.

On Thursday evening precipitation will spread, the focal point will come at about midnight. The snowfall level will lie initially over 1000m, then gradually drop down to the valley floors. Widespread 20-35 cm of fresh snow is anticipated. On Friday, visibility in the mountains will often be reduced due to dense clouds and snow shower. In the afternoon, intermittent dry phases are expected, even a few bright intervals. On the Main Alpine Ridge and southwards therefrom, strong-to-storm strength winds from the north. At 2000m: -9 degrees; at 3000m: -17 to -13 degrees.

Snowdrift accumulations remain prone to triggering.

Slab avalanches in the snowdrifts can fracture down to deeper weak snowpack layers

Avalanche danger above the treeline is considerable, below that altitude danger is low. Snowdrift accumulations are the main problem. Slab avalanches of medium size can in some places b e triggered even by minimum additional loading, i.e. the weight of one person. In some places they can fracture down to deeper weak layers in the old snow and therebe grow to large size. Danger zones can be difficult to recognize due to diffuse light conditions. They occur also distant from ridgelines and on slopes in all aspects. Caution required at the edges of forest zobnes. In transitions from shallow to deep snow, slab avalanches in the old snow can be triggered by one single person.