Deep Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Unlikely
- Size
- 3
A layer of faceted snow 4-8' deep is likely behind very large avalanches that occurred the past two weeks. Though there is a better chance you will see small slab or loose snow avalanches on Wednesday, the rare deep slab avalanche will be much more dangerous if you happen to be in the way. It’s quite unlikely a single person could trigger one of these avalanches but they could still be provoked by a big load like cornice fall, slab, or loose snow avalanche from above. Overall the danger from these is diminishing as colder temperatures make for less cornice fall and other natural activity. That being said it’s still a good idea to not linger on big, northerly alpine slopes below cornices or other hazards.
(3/27/2022)
Very large (D3) deep slab avalanche below Hidden Lake Lookout in North Cascades National Park. Likely triggered by a chunk of cornice falling from above. Northeast aspect at 6700'.
Photo: John Scurlock