Confidence
Fair - Intensity of incoming weather is uncertain for the entire period
Weather Forecast
Wednesday: Another 5-10cm of snow is expected with freezing levels rising as high as 1700m and extreme southwest winds. Thursday: 10-15cm of new snow, with freezing levels around 1800m and light to moderate southeasterly winds. Friday: Continued snowfall with another 5-10cm of accumulation, freezing levels remaining around 1800m and moderate southerly winds.
Avalanche Summary
Initial reports from Tuesday include numerous natural wet avalanches in the Coquihalla area involving saturated recent storm snow running on a crust. There was a report of a size 2 skier triggered slab avalanche on a steep southwest aspect in the Steep Creek area (Duffey Lake). This incident happened a few days ago, but highlights the lingering potential for triggering large slab avalanches.
Snowpack Summary
Approximately 10-20cm of new snow had already fallen by Tuesday morning and another 10-15cm is expected by the end of the day. This new snow is bonding poorly to the previous snow surface, which includes faceted snow, surface hoar, and/or a crust, but is most concerning where surface hoar is sitting on a crust on previously sun-exposed sheltered treeline slopes. Around a metre below the snow surface is a layer surface hoar buried on February 20th. Although this layer has a history of producing large avalanches, triggering this layer has now become difficult, and would most likely require a very large trigger on a steep, unsupported slope. Below this interface, the snowpack is strong and well settled.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.