Triggering large avalanches remains possible. Keep it conservative until things cool off and the snowpack settles.
Weather Forecast
THURSDAY: Clearing throughout the day with freezing levels around 1800m and light variable winds. FRIDAY: Mainly cloudy with light snow bringing as much as 5cm. Freezing levels reaching 1700m and light southwesterly winds. SATURDAY: Mainly cloudy with continued light snowfall totalling 5cm of accumulation. Freezing levels should drop to 1600m and winds are expected to be moderate from the southwest.
Avalanche Summary
Reports from Tuesday include several natural storm and wind slab avalanches up to Size 3 at various elevations. Fresh natural persistent slab avalanche activity was also observed, with a report of two Size 2.5s in the Kicking Horse backcountry, which released on a surface hoar, facet and crust weakness as deep as a metre down. A continued cycle of natural loose wet sluffs reaching Size 2 on sun-exposed slopes was also reported.
Snowpack Summary
Wet surface snow has refrozen into a supportive crust in most places; however, dry soft snow with new surface hoar growth may be found at treeline elevations and below on shaded aspects. Strong to extreme winds on Saturday created wind slabs and cornices in many areas, and scoured north and west-facing alpine slopes. The early January surface hoar/ facet layer is typically down 70-90 cm. Recent very large avalanches have been failing on this interface in the north of the region (see avalanche discussion). In general, the lower snowpack below this layer is well settled and strong, apart from some thin snowpack areas where basal facets exist.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.