Regions
Banff Yoho Kootenay.
With a limited freeze and new snow forecast Saturday night, the avalanche hazard will likely be elevated on Sunday. Start early and pull back from steeper objectives if the surface snow is wet or un-supportive early in the day.
Weather Forecast
Some new snow and moderate SW winds are forecasted overnight on Saturday with a limited freeze as a result of the cloud cover. Freezing levels will stay around 2000m for much of the night. A slight clearing trend Sunday afternoon and evening will allow for a better freeze on Monday morning.
Snowpack Summary
The snowpack is totally dependent on aspect and elevation now. At treeline and above, melt freeze crusts exist to ridge top on solar aspects, while on north aspects, dry surface snow still exists above ~2400m. Below treeline the snowpack becomes wet during the day and is becoming isothermal. The weak basal facets remain present in alpine areas.
Avalanche Summary
Pin wheeling on steep south aspects and some small loose wet avalanches observed on Saturday in the late afternoon.
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.
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.
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.