There's a ton of snow available for forecast winds to build new slabs with on Wednesday. Be ready to back off from features that have signs of previous or especially active wind loading. The potential for dry loose avalanches on steep slopes will also need to be managed as you duck into sheltered terrain.
Wind slabs that formed over weak, faceted surfaces during the weekend storm could remain reactive to human triggering for longer than we usually expect.
Distribution of new slabs has so far been limited, but flurries and especially increasing southwest winds should worsen this problem over the day on Wednesday.
In higher snowfall parts of the region, deep accumulations of new snow that haven't formed into a slab are likely to create large sluffs with rider traffic in steep areas.
A weak layer of facets exists near the base of the snowpack. The likelihood of human triggering is low given the layer's deep burial depth, but storm slab avalanches in motion have the potential to step down. Suspect terrain for human triggering includes steep, thin, shallow, and rocky terrain, which is often found near ridgelines.
Limited observations from operators in the region observing 5-15% of their tenures after the weekend storm detail numerous small dry loose avalanches and several storm slabs releasing with skier traffic and ski cutting, generally below treeline and limited to size 1 or smaller.
We expect some degree of a natural avalanche cycle also took place at higher, wind affected elevations, especially in areas that were on the higher end of our new snow totals. This MIN report from Westridge gives a good indication of conditions that were likely fairly widespread in the region.
A few very large (size 3.5 to 4) deep persistent slab avalanches were also observed over last week, which likely occurred during the very windy arctic outflow event.
Looking forward, the next storm hits the region late Wednesday, but with elevated winds leading the charge and expected to be the initial driver of avalanche hazard during the day.
Steep south aspects may now have a thin sun crust from clearing skies on Monday and Tuesday. The upper snowpack is otherwise composed of up to about 50 cm of new snow from stormy conditions over the weekend. The new snow buried an interface which includes faceted (sugary) surface snow, small surface hoar in lower elevation sheltered areas, and more widespread heavy wind effect and wind slabs at higher elevations from previous northeast winds.
Prior to the storm, a small layer of surface hoar crystals could be found about 50 to 100 cm deep, particularly in areas sheltered from the wind around treeline. This layer appears to be gaining strength and is currently considered dormant, but we're still light on observations showing whether it did or didn't wake up in isolated areas from the weight of the new snow.
Large and weak facets that formed in November are found near the base of the snowpack. Although the likelihood of triggering this layer is low at this time, the consequence of doing so remains very high. This layer is most likely to be human-triggered in thin, rocky slopes at alpine and upper treeline elevations.
Tuesday night
Partly cloudy. Light west winds becoming moderate southwest.
Wednesday
Cloudy with isolated flurries, increasing in late afternoon and overnight. Winds approaching strong southwest by end of day. Treeline high temperatures around -10.
Thursday
Cloudy with continuing snowfall bringing 10-15 cm of new snow, including overnight amounts. Strong southwest winds easing over the day. Treeline high temperatures around -8.
Friday
Cloudy with continuing snowfall bringing 5-15 cm of new snow, including overnight amounts. Moderate southwest winds. Treeline high temperatures around -9.
More details can be found in the Mountain Weather Forecast.
