There is uncertainty about whether the new snow has increased the potential for triggering large avalanches on buried weak layers. This uncertainty is best managed with conservative terrain choices.
There is uncertainty about how easy it could be to trigger a large avalanche on one of several crusts and weak layers in the lower snowpack. Choosing conservative terrain is the best way to manage this uncertainty.
30-40 cm of recent snow has formed slabs that will remain primed for human triggering in steep and wind affected terrain.
SUNDAY NIGHT: Clear with cloudy periods, 20-30 km/h wind from the northwest, alpine temperatures drop to -10 C.
MONDAY: Mix of sun and cloud, 20-30 km/h wind from the northwest, alpine high temperatures around -6 C.
TUESDAY: Mix of sun and cloud, 20-30 km/h wind from the northwest, alpine high temperatures around -6 C.
WEDNESDAY: Mix of sun and cloud, 30-50 km/h wind from the northwest, alpine high temperatures around -4 C.
Numerous storm slab and persistent slab avalanches were reported during the stormy weather on Saturday. Explosive control in the Lizard Range produced numerous large slab avalanches (size 2-2.5) at treeline and alpine elevations. The avalanches ran on the mid-November crust layer 40-80 cm deep. Smaller (size 1) skier triggered slabs were also reported, including this MIN report from Harvey Pass. Preliminary reports from Sunday suggest more large persistent slab avalanches (size 3) were triggered with explosives.
While avalanche activity likely peaked during the storm, triggering storm slab and persistent slab avalanches remains a concern as the snowpack adjusts to the weight of the new snow.
30-40 cm of fresh snow is settling into a storm slab at upper elevations. Crust layers from November and October can be found 40-80 cm below the surface and have recently produced large avalanches with explosive triggers. While these layers are likely widespread across the terrain, we are uncertain about whether they could also be triggered by humans. Snowpack depths range between 50-100 cm at higher elevations and taper rapidly below treeline.
