Wind slabs will be the main concern on Monday. Be on the lookout for stiff, drifted snow and signs of instability like shooting cracks as you enter wind-affected terrain.
Small inputs of new snow will continue to feed wind slabs. As wind direction shifts southeast on Monday, watch for changes in loading patterns.
50-80 cm of snow sits over a weak layer on a thick crust. While only a handful of avalanches have been reported to have run on this layer, they have been large. Avalanches on this layer may be triggered by humans or vehicles from thin spots or by large loads like wind slab avalanches.
Sunday night: A trace of new snow. Light to moderate southwest wind. Freezing level valley bottom.
Monday: Mostly cloudy with sunny breaks. No significant precipitation. Light southeast wind. Treeline temperatures around -8 C.
Tuesday: 5-10 cm of new snow then clearing in the afternoon. Light southwest wind. Treeline temperatures around -11 C.
Wednesday: Mostly cloudy. Light southerly wind. Treeline temperatures around -10 C.
Many professionals reported a surprising lack of evidence of natural avalanche activity during the storm on Saturday. A few size 2 wind slabs were reported. A noteworthy event from the east slopes of the Selkirks, a size 3 (very large) avalanche was triggered by a skier on a cross-loaded south aspect, resulting in a 300 m ride and partial burial. This avalanche is suspected to have run on the crust described in the snowpack summary.
Reports from Wednesday and Thursday indicate an increase in slab reactivity prior to burial by the current storm. There were several reports of natural size 2 avalanches in alpine terrain as well as several human triggered size 1 wind slabs around treeline. The most reactive slabs were on convex wind-affected slopes. Most avalanches were in the top 20-30 cm of snow.
15-30 cm of recent snow has seen redistribution by strong wind at upper elevations.
The defining feature of the snowpack is a widespread prominent crust that reaches as high as 2200 m in the alpine now sits 50-80 cm below the surface. In many places, overlying snow is well-bonded to the crust but in others, weak faceted grains have been observed growing above it around treeline. Snowpack models show the faceting process progressing quickly at this elevation, likely due to the amount of heat and moisture trapped by the crust. We will be closely monitoring this layer going forward. The snowpack structure is relatively simple beneath the crust. with treeline snowpack depths 150-200 cm.
