Dangerous avalanche conditions continue as storm snow continues to accumulate and stress buried weak layers.
A couple of weak layers formed in late November and early December are now sitting about 1 m plus below the surface. This layer may present as surface hoar, a crust, facets or a combination of those, depending on elevation and aspect.
Continuous snowfall and strong wind has formed touchy storm slabs. The conditions are primed for human triggered avalanches.
WEDNESDAY NIGHT: Snow, accumulations of 10-25 cm, 50 km/h wind from the south, alpine temperature drop to -8 C.
THURSDAY: Scattered flurries with another 5 cm of snow, 40 km/h wind from the south, alpine high temperatures around -5 C.
FRIDAY: 20-30 cm of snow, 40-60 km/h wind from the south, alpine high temperature -3 C.
SATURDAY: Another 15-30 cm of snow by the morning then cloudy in the afternoon, 30 km/h wind from the southwest, alpine high temperatures around -3 C.
Heavy snowfall resulted in a cycle of natural avalanches on Tuesday (and potentially on Wednesday too). Numerous natural storm slab avalanches (size 2) were reported on Tuesday, as well as human triggered storm slab and persistent slab avalanches. The human triggered storm slabs were typically 30-40 cm thick. A few larger persistent slab avalanches were triggered remotely on layers that were 40-60 cm deep. Several persistent slab avalanches were also reported last weekend on a range of aspects and elevations, suggesting the persistent slab problem is widespread.
Similar activity is expected on Thursday with more snow expected overnight and strong wind throughout the day.
A continuous pulse of storms has delivered anywhere from 20-40 cm of snow to the North Columbias over the past few days. 40-80 cm of recent snow now sits above a widespread layer of large, feathery surface hoar crystals. New snow is expected to continue to accumulate and consolidate above this layer over the next few days, maintaining a high likelihood of human-triggering.
A weak layer formed in late November is now buried around 1 m plus below the surface. This is the layer of concern relating to the persistent slab avalanche problem. The weak layer may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect. Below this, a variety of crusts from late October are buried deeper in the snowpack.
