Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2–3
Triggering a 2-3' thick persistent slab avalanche is possible on steep slopes. Persistent weak layers (sugary facets, surface hoar, or crusts) exist on most aspects and elevations. The widespread nature of this problem is unusual. You could trigger a large, dangerous avalanche on a variety of slopes including lower elevations and in terrain sheltered from the wind.
Wind and snow over the past few days created fresh wind slabs (see below). The added weight is stressing the buried weak layers, especially at middle and upper elevations where thicker, heavy wind drifts are more common. Yesterday near Red Fish Lake, JP experienced collapsing each time he stepped off of the skin track. This "red flag" warning sign of instability is becoming much less common. This a sign that the snowpack is slowly stabilizing but we're not out of the woods yet. Remember that you could trigger slides remotely—from gentler terrain above, below, and to the sides of steep slopes. These avalanches may break wider than expected or higher on the slope above you.
Unfortunately, avoiding slopes steep enough to slide is the only way to effectively manage this problem. I'll be sticking to lower-angled, wind-sheltered slopes to reduce my risk.
(12/13/2022) Very large avalanche on a W and SW face at 10,400' at the head of Murdock Ck NE of Ketchum.