Continued stormy weather is keeping danger elevated as more snow adds load to a buried weak layer. Stick to simple terrain with no overhead hazard.
New snow is stressing a widespread weak layer consisting of a crust, with facets and/or surface hoar on top of it. This layer is roughly 75-115 cm deep and is expected to produce large avalanches for longer than what is typical after a storm on the South Coast.
By Monday afternoon there will likely be 50-75 cm of recent fresh snow, resulting in thick and reactive storm slabs. Expect natural avalanches in steep terrain during periods of heavy loading, while human triggered avalanches will be likely throughout the day.
SUNDAY NIGHT - Snow mixed with rain, 5 cm/mm / moderate to strong southwest wind / alpine low temperature near 0 / freezing level 1200 m
MONDAY - Snow mixed with rain, 15-25 cm/mm, with another 25 cm/mm overnight / moderate to strong southwest wind / alpine high temperature near 0 / freezing level 1500 m
TUESDAY - Snow, 10-15 cm, with another 10-20 cm overnight / moderate to strong southwest wind / alpine high temperature near -1 / freezing level 800 m and dropping to 500 m overnight
WEDNESDAY - A mix of sun and cloud / light northwest wind, picking up to moderate west wind in the afternoon / alpine high temperature near -2 / freezing level 500 m
Natural avalanches are expected on Monday, and due to the presence of a persistent weak layer, they could be very large.
It has been a busy week for avalanche activity in the North Shore mountains, with human triggered avalanches reported everyday since Monday. These avalanches have failed on a prominent weak layer that was 30-60 cm deep at the time, and will be 60-100 cm deep by Sunday. Recent MIN reports show good examples of these avalanches (e.g. here, here, and here).
North Shore Rescue responded to a serious, but non-fatal avalanche incident on Tuesday evening on Cypress Mountain. One person was involved and was partially buried. The avalanche was a size 2 storm slab on a west aspect at approximately 1100 m and failed on the recently buried weak layer.
Weekend snowfall totals reached about 40-50 cm by Sunday afternoon, and there is another 15-25 cm in the forecast for Monday. At lower elevations, much of this precipitation fell as rain.
With all of this new snow, there will be about 75-115 cm of snow sitting on a widespread crust by Monday afternoon. This crust also has weak facets and surface hoar on top of it in many areas. This widespread weak layer will probably take more time to gain strength than what is considered typical for the South Coast region.
Click here to watch North Shore Rescue's January 29 snowpack discussion, which illustrates this concerning snowpack structure.
