Don't be too quick to rule out the storm slab problem on Monday. That heap of new snow sits on a questionable interface in many areas. Use low consequence slopes to assess the new snow's bond and raise your guard as you approach exposed terrain where new wind slabs pose a more certain hazard.
With 20-40 cm of new snow from Saturday overlying weak grains like faceted snow and small surface hoar, we may see storm slab reactivity persist a bit longer than usual. What's more certain is that large wind slabs perched on leeward (north-facing) terrain will remain primed for human triggering.
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.
Observations of new avalanche activity from Saturday and Sunday aren't in yet but we anticipate some degree of a natural avalanche cycle took place throughout the region but especially where 30 cm or more new snow accumulated on Saturday.
Many small to large (size 1 to 2.5) wind slabs were triggered naturally and by riders over the past few days. They mostly occurred on south to west aspects at alpine elevations resulting from northeasterly outflow winds. A few very large (size 3.5 to 4) deep persistent slab avalanches were also observed over the week, which likely occurred during very windy conditions.
Looking forward, we expect widespread surface instabilities to become more focused toward wind loaded areas.
Stormy conditions brought up to about 30 cm of new snow to the region along with strong southwest wind on Saturday. The Mica Mountain area may have as much as 50 cm! The new snow buried an interface which includes reports of faceted (sugary) surface snow, small surface hoar in sheltered areas, and more widespread heavy wind effect and wind slabs at higher elevations from recent 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 may have woken 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.
Sunday night
Easing flurries bringing less than 5 cm of new snow. Light southwest winds.
Monday
Mainly cloudy with isolated flurries. Light south winds. Treeline high temperatures around -10 °C.
Tuesday
Mainly cloudy with isolated flurries. Light variable winds. Treeline high temperatures around -9 °C.
Wednesday
Cloudy with isolated flurries, increasing overnight. Winds increasing to Moderate southwest by end of day. Treeline high temperatures around -10.
More details can be found in the Mountain Weather Forecast.
