Our deep persistent slab problem may grow less likely to trigger in the coming days, but it isn't going away. Maintain diligent, cautious terrain selection that keeps you clear of thin spot trigger points and big overhead hazards.
Weather Forecast
Saturday night: Mainly cloudy. Strong west winds, increasing to extreme in the alpine.Sunday: A mix of sun and cloud. Strong northwest winds easing over the day. Alpine temperatures around -5 and cooling over the day. Freezing level to 1400 metres.Monday: A mix of sun and cloud. Light southwest winds. Alpine high temperatures around -9 with freezing level back to valley bottom.Tuesday: Mainly sunny. Light west winds. Alpine high temperatures around -7.
Avalanche Summary
Recent avalanche observations have been limited to small (size 1), thin slabs released with ski cutting.
Snowpack Summary
Strong winds are stripping the last loose snow available and packing it into thin winds slab in alpine lees and scoured windward areas. Northwest winds have had some of the most recent impact on snow redistribution, creating 'reverse loaded' pockets of wind slab.In sheltered alpine terrain and between 1600-2000 m, 5-15 cm of recent snow overlies a layer of weak surface hoar and crusts (on solar aspects). Wind slabs that have formed over this interface are likely to be more susceptible to human triggers.Large variability in snow depths still exists in the region, ranging from almost no snow to nearly 200 cm in some areas. For average snowpack areas, expect to find weak and sugary faceted snow around 50 to 100 cm deep, which extend to the ground. This weak bottom half of the snowpack was the culprit in several large avalanches in the region in the past few weeks.
Problems
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.
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.