Deep Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2–3.5
Sometime around January 16, an approximately 1.5m thick (possibly thicker) hard slab avalanche occurred in the Silverton Avalanche Path on a northeasterly slope of Fremont. See photo, and get more information here. This avalanche likely failed in depth hoar near the ground, similar to the HS-N-R3-D3-O avalanche on Fremont, during the New Year’s storm cycle. So far this season, three known persistent slab avalanches have occurred on northeasterly slopes, with starting zones between ~11,400' and ~11,800'.
Near and above treeline, avoid all wind loaded slopes, pillowed slopes and cornices. Avoid steep convex rollovers.
"Deep Persistent Slabs are very difficult to predict and manage. They are low-probability high-consequence events. If you are caught in one, you are unlikely to survive. Often the only evidence of the problem arrives too late as a large, deadly, and unexpected avalanche. The only real effective risk management strategy is to avoid areas where you suspect a Deep Persistent Slab. They are most commonly triggered from shallow spots in the snowpack [usually located at the margins of the slab or slope]. Avoiding these areas is one way to reduce risk. Give yourself a wide safety buffer to handle the uncertainty, potentially for the remainder of the season." - CAIC
(1/18/2023) Estimated at HS-N-R2-D2-U. Likely failed at depth hoar near the ground, and likely occured on MLK day, January 16, 2023. Photo: Troy Marino
