Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Likely
- Größe
- 2–3
A layer of surface hoar (3/29 BSH) is buried under the storm snow that arrived Easter weekend. Storm totals are highly variable with elevation and proximity to the coast. Expect to find 6 inches-3+ feet of new snow depending upon location. The BSH layer has been observed to be widespread and intact above 3000'. The sensitivity of this layer is highly dependent upon several factors that make the current setup dangerous due to the advanced assessment skills needed to safely travel in steep terrain today.
The likelihood of triggering an avalanche today is highly dependent upon the characteristics of the slab that overlie the 3/29 BSH above 3000'. Where higher storm totals exist expect the likelihood and more so the consequence to increase. This part of the assessment challenge is fairly easy, as hasty pits should quickly reveal new snowfall totals. The more challenging part of the assessment and the most important aspect will be the cohesion of the slab (stiffness) and the bed surface. The stiffer the slab, the more prone it will be to human triggers. Slab cohesion is a highly subjective observation making assessment challenging. Slight differences may have a significant difference in stability and could be affected by previous wind effect, and settlement due to sun, temperature, and general settlement over time. The bed surface is also an important factor. East, west, and south aspects have been found to have a temperature crust just below the BSH creating a more effective sliding surface. The crust will promote wider avalanche propagations once initiated.
It is recommended to be conservative in your terrain decisions today. If you decide to venture into steep terrain today try to avoid traveling above exposure and runs that end in terrain traps just in case your assessment of a slope turns out to be wrong.
(3/28/2024)
2-6 mm Surafce Hoar on ridgetops in The Books ~5400'.
Photo: Gareth Brown
