Glockner Group Central

Persistent weak layer in high alpine regions

Persistent weak layer in high alpine regions

Avalanche danger above 2300 m is CONSIDERABLE, below that altitude danger is LOW. Weak layers inside the old snowpack can on shady slopes above approximately 2300 m still be triggered, particularly on wind-protected slopes at the foot of rock walls or behind abrupt discontinuties in the terrain. Avalanches can attain medium size. In addition, fresh snowdrift accumulations are prone to triggering, particularly on steep (>30°) N/E facing slopes above 2200 m. Danger zones occur behind abrupt discontinuities in the terrain, in gullies and bowls, the size and trigger-sensitivity increasing with ascending altitude. Fractures down to deeper layers is possible. Small glide-snow avalanches are still possible. Reports from the relevant regions with regard to the persistent weak layer are few and far between currently (due to the snow situation); for that reason, these estimates are uncertain.

There has been 10-15 cm of fresh snow registered, amid strong-to-stormy winds which transported the snow in highly irregular fashion. The snowdrifts were deposited in gullies and bowls; the crests and ridges are snowblown bare. The snowdrifts lie particularly atop soft layers, on shady slopes at high altitudes. On high-alpine north-facing slopes the layer above 2300 m is often unfavourable due to a sequence of melt-freeze crusts and faceted crystals. This applies particularly to wind-protected slopes. Below 2300 m the precipitation often fell as rain, which is leading to increasingly frequent wet-snow and glide-snow avalanches. Du to the dropping temperature on Saturday, the snowpack has stabilised. On Sunday it will be quite mild, the zero-degree level will ascend to above 3000 m. Thereby the snowdrifts will rapidly consolidate. Below 1800 m there is little snow on the ground.

Sunday: On Christmas Day, very fine weather with lots of sunshine. Residual cloud and fogbanks will recede, visibility will be unhindered. Winds wil be light. It will be very mild. At 2000 m: 2-7 degrees; at 3000 m at midday, 0 degrees. Monday: Above the layers of fog, visibility on Boxing Day will be very good, only some cirrus clouds far above summit level. Winds will be mostly light except on the Main Tauern Ridge (30-40 km/hr) from the south. Still mild: at 2000 m at midday 4 degrees, at 3000 m 0 degrees.

Avalanche danger will decrease somewhat. Snowdrift accumulations are prone to triggering only in isolated cases in high alpine regions.