Regions
Banff Yoho Kootenay.
We are entering early spring conditions. Steep solar slopes will see the hazard rise to Considerable or High in the afternoons. Start early. SH
Weather Forecast
Light W to NW winds, no snow, mainly clear skies, and freezing levels to 2000m+ on Thursday, higher on Friday. This will increase activity on solar aspects.
Snowpack Summary
Kootenay Park today, S through W slopes developing variable melt freeze crusts, thickest on steep W aspects. 20cm powder snow on N aspects over temperature crust up to 1800m. Well settled snowpack at 2300m. Moist snow on solar aspects by 11AM. E of divide settled wind slabs over basal facets. Supportive travel with variable sun crust up to 2700m.
Avalanche Summary
Afternoon loose wet avalanches on solar slopes in Kootenay within last 24hrs up to size 2. Most started in steep terrain at treeline and below, with adjacent lower angled slopes not running. A report of a cornice failure on the N couloir of Bow peak yesterday at 10AM sending one skier tumbling down the gully 200ft in the debris with no injuries.
Confidence
The weather pattern is stable on Thursday
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.