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. Treat wind affected areas below treeline with caution.
40-70 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 snow. Moderate southerly wind. Treeline temperatures around -8 C. Freezing level valley bottom.
Monday: Mostly cloudy with flurries up to 5 cm. Moderate southeast wind. Treeline temperatures around - C. Freezing level 600 m.
Tuesday: 5-10 cm of new snow. Light southwest wind. Treeline temperatures around -8 C. Freezing level valley bottom.
Wednesday: Mostly cloudy. Light southeast wind. Treeline temperatures around -10 C. Freezing level valley bottom.
Wind slabs up to size 2 were reactive to ski cuts and explosives on Sunday. A limited natural avalanche cycle up to size 2.5 was reported to have run during the storm on Saturday. Noteworthy naturals include a size 3 on a northwest aspect in the Selkirks and a size 2 on an east aspect in the Monashees.
Reports from Wednesday and Thursday indicate an increase in persistent 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 prominent and widespread crust that reaches as high as 2400 m in the alpine now sits 40-70 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 snow depths around 100-200 cm.
