Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Possible
- Größe
- 2
There are multiple layers of weak snow generally in the bottom half of the snowpack. Some formed in November, some in early December, some in mid December, and some in late December. To be honest, it's hard for me to keep track of them all, but it doesn't really matter. These persistent weak layers have a layer of snow on top of them that is cohesive enough to be a slab. The photo (A. Bellomy) below shows the general snowpack structure - the bottom half is faceted and weak, the upper half is the slab. The likelihood of triggering a slide has decreased a little, but the snowpack continues to tell us it is unstable with widespread collapsing, cracking, and audible whumpfs. The trouble is that you won't experience this in many places with lots of tracks where these collapses have already been triggered.
The most likely places to trigger a slide today are slopes with some wind-loading especially on more northerly facing slopes with the weakest snow. The little extra weight of wind drifted snow keeps the buried facets stressed and ready to fracture.
Where to ride today? Two options exist:
- Ride slopes less than 30 degrees that aren't steep enough to slide.
- Ride slopes facing south where this persistent weak layer generally doesn't exist and avoid pockets of wind drifted snow. These slopes don't have much snow but have become much more supportable.