Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–2.5
We can’t write off the potential for triggering large avalanches that break on weak, faceted snow buried under Saturday’s 8 to 12 inches of snow. Observations are limited since Sunday, however, the nature of a persistent slab avalanche is tricky. These avalanches may break wider than expected or higher on the slope above you. You may be able to trigger avalanches remotely—from gentler terrain below, above, and to the sides of steep slopes. You can significantly reduce your risk by steering clear of steep, shaded aspects (northwest-north-east) above 6500 feet.
As time passes, we anticipate that this problem will become less reactive. Digging into the snow to evaluate the new/old interface is a good step in understanding this problem. Other evidence – lack of propagation in tests, lack of collapses, or lack of avalanches - suggests the problem is becoming less reactive and more isolated. Giving yourself a safety margin to avoid being surprised.
(4/2/2023)
Slide was triggered from a 32 degree ridgeline. The slab propagated roughly 600 feet and wrapped into two separate drainages.
Photo: Cam