Persistent Slabs
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Possible
- Dimensione
- 2–2.5
It remains possible to trigger a persistent slab avalanche today due to the weak structure and highly variable depth of our snowpack. Recent snow and strong winds from last Monday/Tuesday produced slabs on top of several buried weak layers that include near surface facets and faceted crusts from the two-week dry period. These are the main layers of concern in terms of what you can impact as a backcountry traveler, but it is also possible to impact our early season weak layers in shallower places. The wind that accompanied last week's storm made sure of this, and today's blowdown event may further exacerbate the existence of these shallow spots on and near terrain of concern that carries a slab. If you venture out today, look out for loaded areas and pay close attention to the depth of the pack -- a probe pole can be a useful tool to measure snowpack depths on the slope you plan to play on. Remember that triggering a slide close to the surface could step down into deeper weak layers, which are still present in many places. Persistent slab avalanches of this sort that fail near the ground could be very large, running well into the flats below and would most likely not be survivable.
This is an annotated snowpit from a NNE aspect near treeline that is 140cm deep. In places where the snowpack remains under 1.5 m, deeper persistent weak layers have been slow to heal and continue to remain reactive in long column tests. These shallow spots on the slope are where you're more likely to impact the deeper buried weak layers.
(2/28/2024) Photo: Andy Bond