Regions
Banff Yoho Kootenay.
A natural avalanche cycle occurred today due to the warm temperatures. We expect this to continue until things cool down. Until then avoid all avalanche terrain and minimize your exposure to large slopes when traveling at valley bottom.
Weather Forecast
Continued warm temperatures with freezing levels near ridge tops and strong to extreme W winds continue for Monday. On Tuesday things begin to cool off slightly and we may see some light precipitation. Wednesday the cooling trend continues with winds shifting to the North and generally clear skies.
Snowpack Summary
Strong to extreme SW winds creating wind slabs in open areas above tree line and intense wind transport at ridge tops. Moist snow to ridge top on solar aspects and on all aspects below tree line. Becoming isothermal in shallow low elevation snow pack areas. Dec 18th and basal facets failing naturally and producing avalanches up size 2.5 today.
Avalanche Summary
Numerous natural avalanches were observed and reported today with slabs up to size 2.5 at tree line and above and loose wet slides up to size 2 below tree line in all of the forecast region. Notably Cascade Falls, Rogans Gully, Bourgeau L & R and many of the climbs in Field all saw avalanche activity today. We expect this cycle to continue tomorrow
Confidence
Freezing levels are uncertain on Tuesday
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.
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.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.