Avalanche Forecast

Heavy snowfall and extreme wind on Saturday

Friday night: Overcast, 10-30 cm of snow above 600 m, strong southwest winds, treeline temperatures rising from -5 C to -2 C, freezing level rising from 300 m to 600 m.

Saturday: Overcast, 30-50 cm of snow above 1000 m, strong southwest winds with extreme gusts, treeline temperatures rising to near +2 C in the afternoon, freezing level rising to 1000 m, with freezing levels near 1300 m closer to the coast.

Sunday: Mainly sunny, 5-15 cm of snow overnight above 600 m, light east winds, high treeline temperatures near -3 C, freezing level around 600 m.

Monday: Increasing cloudiness, no snow expected, light south winds, high treeline temperatures near -2 C, freezing level around 100 m. 

Natural avalanches releasing in the new snow are likely on Saturday. These storm slab avalanches are expected to be large, widespread, and very sensitive to human-triggers.

In the neighbouring Sea-to-Sky region on Thursday, we received reports of two large (size 2-3) human-triggered avalanches that released on a persistent weak layer between 1700-1900 m on west and southwest aspects. Notably, these avalanches were remote-triggered while party members were traveling uphill. Several small sympathetic avalanches were also thought to have released during these events. We have concern that this problem may extend into the south coast region at upper elevations in the north of region, such as near Sky Pilot. It may be possible to trigger very large avalanches in isolated areas on Saturday.

Pinwheeling and isolated small (size 1) wet loose avalanches were reported during the strong afternoon sun on Thursday.

An intense storm is taking aim at the region, bringing extreme southwest winds and 40-80 cm of new snow by Saturday afternoon. During the heaviest snowfall midday on Saturday, freezing levels are forecast to rise to 1000 m, creating denser snow over lighter snow and potentially forming a mid-storm crust layer. Freezing levels may reach 1300 m in areas closer to the coast. Extreme southwest wind will likely be a major contributor to the size, likelihood, and distribution of Saturday's storm slab problem. Even open steep slopes below treeline should be treated as suspect on Saturday.

The new snow is falling on a mix of previous snow surfaces, including harder, wind-packed surfaces, a melt-freeze crust that may have formed on steep south-facing slopes during Thursday's sunny skies, or cold soft snow in sheltered areas. 

Small facets (sugary snow) can be found down 120-200 cm near two crust layers that formed in early December. On Tuesday, observers near Ski Pilot reported whumphing that is likely associated with this interface (see this MIN report). It may be possible to human trigger this persistent slab in thinner snowpack areas near ridge tops, where the facets are more developed and where the crust layers are more accessible to the weight of a person or machine.

Below these crust layers, the snowpack is generally well-settled. Early season hazards such as rocks, stumps, and open creeks remain at lower elevations. 

• Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
• Use increased caution at all elevations. Storm snow is forming touchy slabs.
• Avoid the runout zones of avalanche paths. Avalanches could run full path.
• Be aware of the potential for large avalanches due to the presence of a persistent slab.
• Remote triggering is a concern, avoid terrain where triggering slopes from below is possible