Regions
Northwest Inland.
Confidence
Fair - Due to limited field observations
Weather Forecast
Overnight Monday & Tuesday: Moderate Northerly wind backing to strong Westerly or Southwest. Around 10 cm of additional snow with continued cold temperatures (below freezing all elevations). Wednesday: Continued wind: moderate to strong from the west or northwest, with another 5cm of snow and just slightly warmer to around -7 C in the alpine (freezing level climbing to 400m or so).Thursday: Winds finally easing off and backing to the South, continued unsettled with continued light precipitation and just slightly warmer than Wednesday.
Avalanche Summary
Recent reports are of sluffing from steep terrain and small slabs (up to size 2 which isn't that small) forming in pockets behind ridges and ribs. I expect the number and size of windslab avalanches will increase with forecast wind, even if there isn't very much additional new snow.
Snowpack Summary
HST 20 cm building slabs lee SW. Wind should veer to W or NW.Prev Entry (Shannon Jan 27): Variable accumulations of new snow but somewhere around 20 cm is a good estimate for the region. This storm snow continues to build over a variety of old surfaces including old hard and soft wind slabs, scoured slopes, blue ice, thin melt-freeze crusts on southerly slopes and surface hoar. Many windward slopes are scoured and thin. Recent snowpack tests recently gave generally hard to no results near Smithers. An otherwise strong mid-pack overlies a weak base layer of facets/depth hoar. Triggering of this basal weakness may still be possible from thin spots and/or rocky outcrops. I suggest digging down, or probing the snowpack to get a handle of average snowpack depths, variability and test results. The average snowpack depth is around 100 cm at treeline, but remains quite inconsistent across the region.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.