Tune in to patterns of wind redistribution to help you navigate around newly formed wind slabs. Surface clues won't help with more dangerous deep weak layers, so seek out simple terrain that is free of overhead hazard.
Weather Forecast
Monday: Mainly cloudy with isolated flurries and a trace of new snow. Light west winds. Alpine high temperatures around -11 in the north of the region and closer to -7 in the south.Tuesday: A mix of sun and cloud. Light northwest winds. Alpine high temperatures around -12 in the north of the region and closer to - 8 in the south.Wednesday: Cloudy with light flurries bringing a trace to 3 cm of new snow over the day. Snowfall increasing overnight. Moderate west winds. Freezing level rising to a possible 1500 metres with alpine temperatures around -4.
Avalanche Summary
Reports from Saturday showed new storm slabs and wind slabs releasing from size 1-2. These occurred naturally as well as with remote (from a distance) triggering and explosives control. Crown depths ranged from 15-60 cm, owing to snow redistribution from recent strong winds.Friday's reports included observations of a size 2 persistent slab that was remotely triggered on a northeast aspect at 1900 metres in the north of the region, failing on the mid-January weak layer down 70 cm. Another report details a size 3.5 persistent slab that released naturally in the past couple of days in the north of the region. This avalanche initiated at 1400 metres and ran to the bottom of its path, producing a 3 metre high deposit of debris.On Thursday, explosive control work produced slab avalanches up to size 3 on a variety of aspects between 1900 m and 2500 m. Reports from Wednesday included observations of explosives control in the Bugaboos and surrounding area producing numerous persistent slab results from size 2-3.5. Many of these avalanches ran on the mid-December layer buried 150-200 cm deep. Northwest through northeast aspects in the alpine were the primary targets.
Snowpack Summary
Recent storms have produced variable new snow accumulations of 20-50 cm. This snow overlies a complex and generally weak snowpack structure with three active weak layers that we are monitoring:70-120 cm of snow overlies a crust and/or surface hoar layer (from mid-January). The crust is reportedly widespread, except for possibly at high elevations on north aspects. The surface hoar is 10-30 mm in size and exists at all elevation bands. Deeper in the snowpack (down about 80-130 cm), a persistent weak layer known as the early-January layer is present at all elevation bands, and composed of surface hoar on sheltered slopes and sun crust on steep solar aspects. Recent snowpack tests have shown sudden fracture characters with moderate loads and high propagation potential. Another persistent weak layer that was buried mid-December is 90 to 200 cm deep and consists of a facet/surface hoar/crust combination. It is most problematic at and below tree line and features prominently in recent avalanche reports.
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.