Regions
Northwest Coastal.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
A warm front will bring precipitation to the north coast on Wednesday night and Thursday. Unsettled conditions are expected for Friday before the next system reaches the coast on Saturday.Wednesday Night: Precipitation: 5-10mm, freezing level: 1300m, ridgetop wind: moderate S-SWThursday: Precipitation 5-10mm, freezing level: 1100m, ridgetop wind: moderate S-SWThursday Night: Precipitation 10-15mm, freezing level: 700m, ridgetop wind: moderate-strong SWFriday: A mix of sun and cloud, light scattered flurries possible, freezing level: 900m, ridgetop wind: light SWSaturday: Precipitation 5-10mm, freezing level: 1100m, ridgetop wind: strong S-SW
Avalanche Summary
On Monday, a slab avalanche size 2.5 was remotely triggered on a North facing alpine slope in the North Eastern part of the region. This slab released on the deep persistent weak layer buried in mid-February. Widespread activity occurred over the weekend caused by warm temperatures and strong solar radiation. Things have typically stabilized over the last few days due to cooler temperatures and lack of sun. Avalanche activity is expected to increase with warmer temperatures, new snowfall, and moderate-strong winds.
Snowpack Summary
New snow may sit on a crust which exists up to around 1400m on solar aspects or on last week's storm snow (90cm+ in areas of the region). Winds slabs are expected to form in lee features from moderate-strong S-SW winds.Recent warmer temperatures have helped to settle the underlying snowpack. In shallower snowpack areas or on steep, unsupported features, the old storm slab may still be reactive to human-triggering. This older storm slab is sitting on a surface hoar, a crust, and/or facets buried at the beginning of April. Large cornices may still be a concern, especially during periods of warming or heavy loading. The early February crust/facet layer is typically down 1.5 to 2.5m. A smaller avalanche or a cornice fall may still have the potential to step down to layer causing very large, destructive avalanches.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.