Regions
Banff Yoho Kootenay.
Start and finish very early to travel when the snow is still cold, and be out of all avalanche terrain by the time the day heats up. We are seeing more and more avalanche activity each day with high danger levels at all elevations in the afternoons.
Weather Forecast
We expect a decent overnight freeze on Sunday night followed by rapidly rising freezing levels to near 3000 m on Monday afternoon, and slightly higher daytime temperatures on each of the following two days. Winds will remain light out of the N and W. No new precipitation is expected and the next few days look sunny and clear.
Snowpack Summary
Sun crusts or moist snow on solar aspects and moist snow at lower elevations. 15-50 cm of snow has accumulated since March 7. This sits over a mix of facets, sun crust and wind slabs above treeline, and over 30-50 cm of weak facets elsewhere. While a supportive mid-pack exists in thicker areas, weak facets to the ground are seen in many thin areas.
Avalanche Summary
Numerous natural and human triggered loose wet and slabs up to size 2.5 have been seen over the last two days at all elevations with several close calls and serious incidents. South aspects have been most active due to solar heating, but we are seeing increased activity on North aspects with cornice failures, wind slabs and skier triggered slabs.
Confidence
Freezing levels are uncertain
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.