Coquihalla area: The danger is CONSIDERABLE at treeline for Tuesday due to enhanced recent snowfall in that part of the region.
Confidence
Poor - Timing, track, or intensity of incoming weather is uncertain on Wednesday
Weather Forecast
Tuesday: 5-10cm snow. Strong westerly winds. Freezing level at valley floor.Wednesday/Thursday: Three weather models show very different outcomes. Anything's possible - from dry conditions to moderate (locally heavy) snowfall, with strong westerly winds and a slight rise in temperature. Confidence is poor. Check in tomorrow for an update.
Avalanche Summary
Skiers triggered slabs up to size 2 in the Coquihalla region on Saturday (incident reports here: https://avalanche.ca/cac/library/incident-report-database/view). In other parts of the region, storm snow was failing naturally and reacting easily to ski cuts. These results involved the storm snow and did not dig down to any deeper weaknesses.
Snowpack Summary
20-60cm dry recent snow has accumulated over the last few days (highest amounts around the Coquihalla). Increased wind and further snowfall is expected over the next few days, making new wind slab development very likely. Older wind slabs seem to have gained strength. A hard crust sits below recent storm snow layers. Recent snowpack tests showed stubborn or no results on this layer, which supports the weight of a person.Deeper in the snowpack, two persistent weak layers remain a concern only in thin snowpack areas (perhaps wind-scoured zones or relatively dry eastern ranges) and particularly in steep rocky terrain or sheltered terrain which has a thin snowpack. The two layers are surface hoar and/or facets associated with a crust from mid-December and sugary facets at the base of the snowpack.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.