Sustained warm temperatures will keep avalanche danger elevated on Friday, particularly on slopes getting direct sun. Be prepared to back off steep slopes when the snow becomes wet or slushy.
Warming temperatures could temporarily increase the likelihood of large persistent slab avalanches. There are several potential layers of concern across the region that have produced some sporadic activity over the past weeks.
Wet loose avalanches may release naturally on steep sun-exposed slopes. A wet snow surface, pinwheeling or loose wet point releases out of the rocks are good indicators that it is time to back off. Keep in mind that loose wet avalanches and weakened cornices can serve as triggers for persistent slabs.
Thursday night: Mostly clear, moderate southwest wind, freezing level remaining above 2100 m.
Friday: Clear with clouds moving in for the afternoon, moderate south wind, freezing level remaining above 2100 m.
Saturday: Mostly cloudy, 5-10 cm of snow, moderate southwest wind, freezing level near 1500 m.
Sunday: Mostly cloudy, 5-10 cm of snow, moderate southwest wind, freezing level near 1300 m.
Numerous large (size 2) wet loose avalanches released naturally on south-facing aspects between 1700-2000 m over the past few days of sunny, warm weather.
Over the weekend, there were a few natural and skier triggered wind slabs size 1.5. On Saturday, large explosives produced very large (size 2-3) results at Kootenay Pass. In thin snowpack areas on solar aspects, a few of these large avalanches are suspected to have stepped down to the January layer described in the snowpack summary.
Elevated freezing levels and sun will continue melting, and potentially destabilizing, snow surfaces on Friday. Watch for pinwheels and roller balls, as they are a clear indication of wet loose avalanche activity. You can avoid them by staying off steep slopes when the snow becomes wet or slushy.
At upper elevations, snow is wind-pressed in most exposed areas, and a melt freeze crust is forming on sunny slopes. In shaded, sheltered areas, 15-30 cm of well-settled snow may sit over a layer of small surface hoar crystals buried Feb 25th. A more prominent persistent weak layer from late January is buried 80-150 cm deep and is composed of a combination of surface hoar, crusts, and facets. The problem seems to be most pronounced in thin snowpack areas on solar aspects. The current impulse of warming will likely be the final test on these layers, as there is some uncertainty about whether they will become reactive again under these conditions.
As described in this MIN report, shallow snowpack areas in the east of the region may harbor a faceted basal snowpack. This structure can typically be managed by avoiding shallow rocky areas where the snowpack transitions from thick to thin. This is another layer that could be susceptible to shock from the warm temperatures this week. Extra caution should be exercised in these shallow snowpack areas.
