Regions
Banff Yoho Kootenay.
High winds in the alpine have generated windslabs in the immediate lee as well as cornices. Rain saturated snow to treeline has weakened the strength of the upper snowpack so avoid any steep terrain where the snowpack is isothermal.
Weather Forecast
Rising freezing levels and saturated air will generate heavy snow across the mountains of western BC. After dipping below 1500 meters Saturday morning in the south, the freezing level rise to, and then hover near 2000 meters tonight through Monday afternoon. For the rest of the week, the freezing level will remain near 1500 to 2000 meters.
Snowpack Summary
Rain saturated upper snowpack to 2000 meters on all aspects. Moderate to strong winds in the alpine forming wind slabs up to 30cm in the immediately lee on east through north aspects. The mid pack above tree line is well settled which overlies basal facets and depth hoar.
Avalanche Summary
Lake Louise and Sunshine reported significant cornice growth and several wind slabs up to size 1.5 being easily triggered on the March 28th crust interface. Wind slabs were far more stubborn to trigger on north aspects due warm temps and rapid settlement.
Confidence
Intensity of incoming weather systems is uncertain on Monday
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.
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.
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.