Observations from backcountry and incoming reports about slab avalanches triggered by persons confirm the snowpack’s current high trigger sensitivity regionally. Particularly south of the Inn, avalanches can be triggered in the old snow in some places and grow to dangerously large size. Avalanche prone locations are difficult to recognize. On the Rosskopf in the eastern Tux Alps a fatal avalanche incident occurred today, Thursday, 26.12.
Avalanche situation continues to demand restraint
As reported in the last blog, fresh snow and drifts from the most recent bout of precipitation lie deposited regionally atop a shallow, weak old snowpack surface, often with marked, persistent weak layers. As was assumed from the snowpack development, it has been confirmed that particularly south of the Inn the persistent weak layer is marked. Unfolding danger situations have developed in accordance with this.
The Avalanche Bulletin for Friday 27.12 shows beyond the borders a quite uniform picture: in the northern barrier cloud regions the snowpack is consolidating steadily. In inneralpine regions the situation is improving more slowly due to the persistent weak layer problem. In the southern regions there is very little snow on the ground, frequency and size of danger zones are smaller and avalanche danger correspondingly lower.
Persistent weak layer problem in the inneralpine regions. Particularly unfavorable are very steep W/N/E facing slopes above 2200m, sunny slopes above 2400m. Sunny slopes are slowly stabilizing due to higher temperatures and solar radiation, triggerings appear increasingly unlikely for the next few days. Since the danger zones in the old snow are practically impossible to recognize, only a cautious route selection can help, i.e. circumventing terrain traps and large steep slopes, as well as consequently maintaining standard safety measures – distances between people, single descents. Thereby, the consequences of possible releases can be markedly reduced.
In the western and northern regions where snowfall has been heaviest, fresh snow and snowdrifts from the last couple of days have consolidated quite well due to warmth and sunshine. The main problem here: gliding snow.
Nevertheless, the persistent weak layer is still present even there. Particularly in very steep terrain and in transition zones from shallow to deep snow, releases can in isolated cases fracture down to more deeply embedded weak layers of the snowpack, especially above 2200m.
Otherwise, high attentiveness is required towards trigger-sensitive freshly generated snowdrifts in ridgeline terrain and behind protruberances in the landscape. Shady slopes are more unfavorable, snowdrift accumulations are consolidating more slowly there. Such danger zones can be easily recognized and should be circumvented, particularly in very steep terrain.
From the Main Alpine Ridge towards the south, snow depths diminish measurably. Stormy winds did their work up to Christmas Eve. Most of the snow lies in the form of hardened snowdrift accumulations, particularly in gullies and bowls. There, these easily recognized snowdrift masses are often triggerable, decreasingly so further southwards. This applies especially to very steep to extremely steep shady slopes. Also avalanche magnitude decreases the further south you go.
Fatal avalanche accident on Rosskopf in the Tux Alps
Thursday midday, 26.12, an avalanche incident occurred on the Rosskopf in the eastern Tux Alps in which two persons lost their lives. It was a medium-sized slab avalanche which fractured on a very steep east-facing slope at 2500m just below the summit. A precise analysis of this incident will be published in the next few days in a separate blog.
