Lower Tauern Central

Danger zones for slab avalanches not always recognizable

Danger zones for slab avalanches not always recognizable

Danger is generally CONSIDERABLE (3). Main problem: slab avalanches which can be very easily triggered (by 1 person) in steep terrain and then grow to dangerously large size (magnitude 2 to 3). Danger zones in all aspects are not always recognizable (fresh snow problem). For that reason, much experience in assessing avalanche dangers on-site is imperative. The dangers presented by fresh snowdrift accumulations are more visible, especially on NE/E/S facing slopes, on steep ridgeline slopes and in gullies. In extremely steep terrain below 1800 m small to medium naturally triggered glide-snow avalanches are possible. Furthermore, on extremely steep, sun-drenched slopes also loose-snow avalanches (magnitude 1 to 2) can trigger naturally. In high alpine starting zones, avalanche can develop huge powder clouds.

Since Friday there has been 30-60 cm of fresh snow registered, up to 80 cm in the Northern Alps at high altitudes. The fresh snow above the treeline has a high proneness to triggering, having been worked on by W/NW winds since Saturday afternoon. Both stability tests and already naturally released avalanches demonstrate this amply! Above all else, the cold, loose fresh snow beneath the bonded fresh snow must be seen as the riskiest weak layer with good fracture propagation potential. In high alpine regions, faceted layers in the old snowpack base were often triggered. Below 1600 to 1800 m, the snowpack is often gliding over the smooth ground.

On Saturday night the snowfall will come to an end, only a few last centimetres are expected, and the clouds will begin to disperse from the west. On Sunday, good visibility and sunshine. Final residual clouds and swaths of fog (esp. in eastern mountain ranges) will soon disperse. The NW wind will swiftly slacken off, no longer disturb. Temperatures will rise: at 2000 m from -15 to -10 degrees; at 3000 m to -17 degrees. On Sunday night, skies will be clear. During the daytime hours on Monday, adequate visibility, heavy cloud cover, diffuse light conditions, but the peaks will be free by and large. It will remain dry. The southerly wind will be light to moderate (up to 30 km/hr). Temperatures will rise further. At midday -2 to -5 degrees at 2000m; at 3000m -8 degrees.

Also on Monday, a still considerable snowdrift problem at high altitudes. As temperatures rise measurably at all altitudes the snow will settle further and proneness to triggering recede.