Heavy snowfall and extreme winds are forming deep and reactive storm slabs. Large natural avalanches are very likely. Avoid all avalanche terrain.
A problematic layer of surface hoar buried in early March is now 70-120 cm deep. Heavy snow loads and storm slab avalanches are likely to trigger this layer, resulting in very large and destructive avalanches. If we're lucky, a widespread avalanche cycle on this layer will clean out the problem altogether.
Deep and reactive storm slabs are building at elevations where precipitation falls as snow.
Loose wet avalanches are likely at elevations where precipitation falls as rain.
Monday night: Snowfall 15-20 cm. Strong south wind. Alpine low temperature around -3 °C. Freezing level rising to 1500 m.
Tuesday: Snowfall 20-40 cm. Strong to extreme south wind. Alpine high around -1 °C. Freezing level 1500 m.
Wednesday: Snowfall 10-20 cm. Moderate southwest wind. Alpine high around -6 °C. Freezing level 1000 m.
Thursday: Overnight snowfall around 5 cm then clearing. Light to moderate south wind. Alpine high around -4 °C. Freezing level 1200 m.
Reports of persistent slab avalanches have been steadily coming in over the last few days from northwest of Terrace. These avalanches have been large to very large (size 2-3), failing on a weak layer buried 60-100 cm deep mostly on northeast facing slopes. These avalanches are easily triggered by riders and vehicles, some remotely or sympathetically, and propagating long distances.
Looking forward, we are expecting a large, widespread storm slab avalanche cycle Tuesday. There is a good chance of step-downs to the persistent layer, which will result in very large and destructive avalanches that could run full path.
30-60 cm of new snow by the end of the day Tuesday is forecast to fall amid strong to extreme wind. Below 1500 m, wet snow and rain in expected to soak the previously moist snowpack.
A weak layer of surface hoar buried 70-120 cm deep has been reactive recently and will likely produce large avalanches during the current storm. A thick rain crust from mid-February 100-150 cm deep caps a well consolidated lower snowpack.
