If you see less than 15 cm of new snow, hazard may only be considerable.
Avoid avalanche terrain and overhead hazard during periods of heavy loading from new snow and wind.
This weak layer has demonstrated extensive propagation across terrain features following the last big storm. With the incoming weather, it has the potential to trigger both natural and human-initiated avalanches again.
New snow and extreme winds are expected to build reactive new storm slabs. The highest danger will be on steep, leeward north-facing slopes below ridgetops.
On Monday, north of Stewart, a vehicle triggered a size 1.5 slab on the persistent weak layer. It failed on a northwest slope in the alpine.
Thursday and Friday, natural, human, and explosive-triggered wind slab avalanches, (size 1 to 2) were reported.
Looking forward, we expect the likelihood of both natural and human-triggered avalanches to significantly increase during this stormy period.
5 to 15 cm of recent snow is covering surface hoar and facets or a thin crust in some areas. An additional 10 to 25 cm accompanied by extreme southerly ridgetop winds is forecast overnight and throughout Tuesday. This combo is expected to build fresh storm slabs and deep wind-deposits on leeward slopes.Soft snow still exists in sheltered terrain and in the trees.
An additional concern is a persistent weak layer of surface hoar and facets overlying a crust. It is buried 60 to 120 cm deep in the southern parts of the region, and up to 200 cm deep in areas north of Stewart. Several large avalanches failed on this layer in the last big storm, producing wide propagation.
Treeline snow depths are around 160 cm.
Monday night
Mostly cloudy with 0 to 5 cm of snow. 80 to 100 km/h south ridgetop wind. Treeline temperature -4 °C.
Tuesday
Cloudy with 10 to 30 cm of snow, or possible rain below 1500 m. 80 to 100 km/h south ridgetop wind. Treeline temperature 0 °C. Freezing level rising to 1500 m near Terrace.
Wednesday
Overnight snow 10 to 20 cm by morning. Cloudy, 25 to 35 km/h west ridgetop wind. Treeline temperature -1°C.
Thursday
Cloudy with 15 to 30 cm of snow. 80 to 100 km/h west ridgetop wind. Treeline temperature 0 °C. Freezing level rising to 1600 m near Terrace.
More details can be found in the Mountain Weather Forecast.
