Persistent Slabs
- Alpin
- Limite forestière
- Sous la limite forestière
- Probabilité
- Unlikely
- Taille
- 1.5–2.5
Three or four inches of snow fell early Monday morning and you may find shallow, dense wind slabs in upper elevation start zones. Any avalanches triggered in the new snow will probably be small and relatively harmless … unless you happen to be in terrain where even small slides can be dangerous.
Surface conditions could make for challenging travel. A very firm melt or sun crust can be found on solar aspects and all aspects below treeline and observers report breakable crust on upper elevation, shaded slopes.
More interestingly, the potential to trigger an avalanche in the crust-facet layering from late January remains. The last reported human triggered avalanche on this layer was on February 5th, but four natural avalanches were observed in the last week on Shuksan, Table Mountain, Mt. Baker, and the White Chuck Glacier. Here is what we know:
- The layers are most prevalent on shady aspects above 5400 feet in elevation.
- There are 2 or more feet of new snow above the weak layer.
- Observed avalanche sizes are ~D2.
- Snowpack tests produce inconsistent results, sometimes even in the same snowpit.
- Many steep slopes - some very near avalanches which released in the same layers - have been ridden and skied with no results.
Although the likelihood of triggering one of these avalanches is low, the consequences could be high if you are in a bad spot in the terrain. Remember persistent slab avalanches can be triggered from low on the slope or remotely and factor in the consequences of triggering a large avalanche on the slope in question.
(2/12/2022)
Avalanche suspected of failing in January 30th crust-facet layers. Estimated date of occurrence between Feb 8th-11th. East-northeast aspect at 6200' or Mt. Baker/Schriebers.
Photo: Graham Clark