Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 4
Our deep slab avalanches, while becoming increasingly stubborn, can roar back to life with any additional stress, ie: heavy snowfall, strong winds, etc. Cornices may also be a good trigger for these larger avalanches. We haven't heard of any avalanches into this old layering 3-6' deep for a week or so, but they very much remain central to my route selection. These deeper slabs exist on all aspects at the upper elevations and on west to north to southeast facing slopes at the mid elevations. You are more likely to trigger these in steep, thin, rocky terrain or areas that may have avalanched during previous cycles.
These avalanches are tricky insofar that immediate signs of instability are often not present and it's easy to be lured onto slopes with other tracks, particularly when snow depths and snow tests might point "stable". The problem is the wide spatial variability across many slopes where you might hit the trigger point here (where the slab is thinner) but not there (where the slab is thicker).
My travel advice is to continue to avoid being on or beneath steep terrain where the facets in the basement exist. See Trent holding onto the weak sugary faceted snow he's pulled out of the bottom of the snowpack.
