Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Regions
Banff Yoho Kootenay.
Simplify your terrain choices this weekend. Sunny skies will increase the danger on solar aspects Saturday, and produce large cornice failures on lee aspects. Numerous weak layers in the snowpack are making for complex decision making. SH
Weather Forecast
A good valley bottom freeze into Sat. but expect freezing levels to quickly reach 2000m with strong solar input as skies will be clear. There will be a temperature inversion to start Sat. (warmer air aloft in the high alpine). Sunday may be even warmer with cloud moving in in the afternoon. Light Westerly winds throughout the weekend.
Snowpack Summary
The snowpack is complex right now. 40-100 cm of new snow sits on crusts on W through E aspects right up to alpine elevations. This has been reactive with explosives in many areas recently. Thinner snowpack areas have prominent facets at or near the base, and large cornices are sitting above many lee slopes.
Avalanche Summary
Avalanche control on Mts. Stephen ad Dennis Friday produced avalanches to size 3. On the same flight numerous large natural avalanches to size 3 were observed. These were 24-48 hours old on NE through N aspects in the alpine, some stepping right to ground or near ground.
Confidence
Freezing levels are uncertain on Saturday
Problems
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
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.