Regions
Northwest Coastal.
Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Sunday: Mostly dry. Treeline temperatures around -4C. Winds mostly light southwesterly. Monday: 20-30 cm new snow. Temperatures around -6C. Strong southwesterly winds gusting to 60 km/h. Tuesday: Moderate or heavy snowfall with temperatures around -8C. Moderate or strong southwesterly winds.
Avalanche Summary
A cycle of natural and human-triggered (including remotely-triggered and helicopter-remote) avalanches of up to size 2.5 has been observed across the region. This pattern is ongoing. Storm snow is propagating easily on buried surface hoar and facets. Skiers recently triggered avalanches that resulted in wide propagation in the Shames Backcountry, highlighting the surprising reactivity of the snowpack.
Snowpack Summary
30-70cm of recent storm snow is bonding very poorly, with very touchy reactivity on buried surface hoar, especially near Terrace. This layer is being triggered naturally or remotely and propagating widely. Recent strong southwesterly to southeasterly winds have set up wind slabs in many exposed lee areas. There are two surface hoar layers in the upper snowpack. The upper one formed at the end of December and is buried approximately 30 cm below the surface. This one is particularly reactive at present. The lower one formed at the beginning of December and is buried approximately 90 cm below the surface. Hard, planar compression tests have been reported on this layer. Near the base of the snowpack, a crust/facet layer continues to give hard, sudden results to no results in snowpack tests. This weakness is unlikely to be triggered by a single person, but it remains possible with a very heavy load (e.g. cornice fall) or from a thin-spot trigger point.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.