Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Possible
- Größe
- 1–2
An overall poor snowpack structure exists on many Northwest through East slopes above treeline. It's on these slopes that you're most likely to find hard slabs resting over very weak fragile faceted snow. These hard slabs formed from a strong wind event prior to Christmas and have decomposing faceted snow from the end of December storm on top. The persistent weak layers of concern are found below the hard slab. You may not see obvious signs of instability like recent avalanches, collapsing, and shooting cracks. If you find yourself on a hard supportable slab, it's almost guaranteed that weak faceted snow exists beneath.
You are most likely to trigger an avalanche on these slopes over areas where the slab is thinnest such as around rock outcroppings and on the margins of the slab. You can mitigate this hazard by avoiding slopes greater than 35 degrees.
In our travels we got this slope to collapse on 1/11 on a NE slope above treeline. In extended column tests, facets just below the hard slab failed with easy force with the ability to propagate