Ongoing storm loading and a buried weak layer are creating tricky conditions. Watch for fresh wind slabs on Wednesday and use extra caution on south facing slopes when the sun is out. Conservative terrain selection remains critical.
Summary
Confidence
Moderate -
Weather Forecast
Another 5-10 cm of snow is expected Tuesday overnight with strong alpine wind from the southwest. A mix of sun and cloud is expected on Wednesday with the potential for isolated snow flurries. Alpine wind is forecast to be moderate from the west and treeline temperatures are expected to be around -8C. Similar conditions are expected for Thursday with sunny breaks, snow flurries, moderate alpine wind from the southwest, and treeline temperatures around -8C. A storm system is currently forecast to arrive Thursday overnight and bring 20-30 cm of new snow by midday Friday. Alpine wind should be strong from the southwest during the storm and freezing levels may climb as high as 1800 m on Friday.
Avalanche Summary
On Monday, four human triggered storm slab avalanches size 1-2 were reported. These were typically 25-35 cm thick slabs and all occurred above 2000 m elevation. Explosives produced numerous storm slab avalanches up to size 2. Skier triggered loose sluffing was also reported from steep terrain features. On Sunday, a skier triggered a size 2 persistent slab avalanche on a south aspect at 1750 m elevation which failed on the late February sun crust/surface hoar interface down 30-60 cm. A skier also triggered a size 1 wind slab on a north aspect at 2100 m which had an average slab thickness of 35 cm. On Wednesday, large persistent slab avalanches remain a serious concern with the snow from the past week releasing on the late-February weak layer. It may still be possible for a person to directly trigger a persistent slab or a smaller avalanche could step down. Strong southwest wind and new snow Tuesday overnight is expected to develop new wind slabs in immediately leeward terrain features which may be touchy. Old lingering wind slabs may also still be reactive.
Snowpack Summary
Another 10-15 cm on Monday brings the typical storm accumulation in the past week to 50-80 cm. This snow has settled into a slab that sits over the late-February interface which includes sun crust, surface hoar, and weak faceted snow. Strong southwest wind over the weekend redistributed some of this storm snow forming thicker deposits in leeward terrain at higher elevations. The thick mid-February crust layer is now down 80-120 cm and exists on solar aspects and at lower elevations. This layer appears to have gone dormant but is still a concern which could wake up in the future with heavy loading or a major warming event. In most deeper snowpack areas, the snowpack is well settled and stable below this crust layer. However, areas with a shallow snowpack (less than around 1.5 m) have a lingering basal weakness at the bottom of the snowpack.
rbuhler,
Avalanche Canada
