Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1–2.5
Buried surface hoar is likely becoming harder to trigger, however, consequences remain high if triggered, avalanches have potential to step down to deeper layers.
Uncertainty about buried weak layers warrants conservative terrain choices.
Buried surface hoar is likely becoming harder to trigger, however, consequences remain high if triggered, avalanches have potential to step down to deeper layers.
New snow is likely poorly bonded to underlying surfaces. Expect loose dry sluffing in steep terrain and thin but touchy storm slabs.
A layer of weak facets near the ground can be triggered by large loads or even by riders in shallow rocky areas.
Explosive control work over the past week has been consistently triggering large avalanches on buried weak layers with the most recent occurrence on Thursday in the Esplanade.
Last weekend, a skier in the Dogtooth Range was uninjured after accidentally triggering a size 2 deep persistent slab on basal facets over a smooth rock slab.
New snow continues to gradually accumulate 5-20 cm over old surfaces including crusts, facets and surface hoar. Beneath lies a complex snowpack with several layers of concern.
A layer of surface hoar is buried 40 to 70 cm deep in the Dogtooth and 60 to 90 cm deep in the Esplanade ranges. It is a concern at elevations (generally above 2000 m) where it is not bridged by a hard crust.
Weak basal facets characterize the lower snowpack, especially in alpine terrain.
Read this blog post for more details.
Snowpack depths at treeline range from 60 to 130 cm.
Friday night
Cloudy with 5-10 cm of new snow, southwest alpine wind 30 km/h, treeline temperature -10°C.
Saturday
Mostly cloudy with a few centimeters of new snow, southwest alpine wind 15 km/h, treeline temperature -7°C.
Sunday
Up to 5 cm of new snow overnight then clearing to a mix of sun and cloud, southwest alpine wind 10 km/h, treeline temperature -8 °C.
Monday
A mix of sun and cloud, southwest alpine wind 20 km/h, treeline temperature -9 °C.
More details can be found in the Mountain Weather Forecast.