Deep Persistent Slabs
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Possible
- Dimensione
- 2–3
This zone picked up 1-1.5" of SWE since Tuesday afternoon. We don't have direct observations of the Banner Summit Zone since skies cleared yesterday but this load was enough to cause a widespread avalanche cycle in the Sawtooths and the Smoky Mountains. Avalanches occurred on many different aspects, in both obviously wind-loaded and generally sheltered terrain. Recent avalanche activity in neighboring zones is likely to have occurred on the weak layer of sugary facets that was buried in mid-December (video).
There are some important differences in the Banner Summit Zone, primarily tied to the overall depth of this primary weak layer:
- Because the weak layer is so deep, it's getting more difficult to trigger avalanches involving this layer.
- On the flip side, avalanches you trigger on this layer may be very large—big enough to destroy vehicles and break large trees.
- Even though many slopes in this zone already avalanched during the Winter Solstice storm, a storm last week still produced some noteworthy slides (example, example).
The added snowpack depth from this storm will make evaluating stability that much more difficult. Snowpack stability tests are less trustworthy, and snowpack collapses will be less frequent. In many cases, the first obvious sign of instability can be triggering a monster avalanche. Continue to choose low angled slopes and to pay extra attention to the terrain adjacent to them. Remotely triggering an avalanche from below, above, and to the sides of steep slopes remains a very real possibility.
