Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Likely
- Größe
- 1.5–2
What and where is it: You could trigger soft and hard, 1-3 foot thick slabs where wind formed drifts or stiffened the snow surface, most likely near ridgelines over about 9000'. Triggering an avalanche is far less likely—but not out of the question—on steep slopes that are sheltered from the wind. Where slabs exist, they rest above a variety of weak layers (facets, crust + facet combinations, and possibly surface hoar). The widespread nature of the weak layers means avalanches are possible on many aspects.
How can you recognize it: Snowpack cracking (photo), and collapsing or whumphing, are clear signs of unstable conditions. Watch for snow pillows, dunes, and ripples (photo), and feel for stiff snow under your feet or sled. These are signs the wind has been at work transporting snow. Assume the weak layers exist on most slopes.
How can you manage it: You can avoid steep, wind-loaded slopes to significantly reduce your chances of triggering an avalanche. Persistent Slabs can release in surprising ways, break wider than expected, and release above or hundreds of feet away from where they are triggered. Remotely triggering an avalanche from flat terrain below steep slopes remains possible. Keep a close eye on your partner and the terrain that's above you.
(12/21/2024) Skier-triggered avalanche near 9800' on a NE aspect in the northern Boulder Mtns.