Use caution in areas that have not seen recent riding activity. The new snow will take time to stabilize.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
A low pressure system moving into the area from the South West will pass through Saturday afternoon and Sunday morning bringing 10 to 20cm of moist snow to the region. Freezing levels will fluctuate between 500m overnight to 1000m in the afternoon on Sunday. Monday the freezing level will again rise to 1000 m with cloudy skies and the possibility of flurries.
Avalanche Summary
Reports from yesterday include several large ( 2-3) natural avalanches as well as a size 1, loose-wet avalanche below tree line. Operators are also reporting impressive results with explosives, up to size 2.5. Precipitation tonight and tomorrow will likely produce a new round of wind slab activity. In places where buried persistent weak layers exist, the likelihood of triggering wind-deposited snow will also increase the chance of affecting the storm slab.
Snowpack Summary
Recent storms with strong southwest winds have redistributed the snow at tree line and above. Wind slabs have formed lee on slopes. Operators have reported moist-wet snow below 1800 metres. East of Crowsnest Pass, new snow overlies scoured surfaces or hard stubborn wind slabs from last week. In general, the mid and lower snowpack are strong and well-settled in these areas.In areas to the west of the divide there's a mix of weak crystals around 30 to 50cm below the surface. These crystals, that formed at the beginning of January, seem most reactive in open areas below treeline and consist of surface hoar, facets and a hard crust that formed on steep solar aspects. Additional snow load will add to the size and reactivity of this developing persistent slab. About 60cm below the surface you may also find a surface hoar layer which formed in December. Although no avalanches have been reported on this layer, it continues to produce sudden planar results in snowpack tests and could come into play with a large trigger such as a cornice, or simply additional storm loading.All areas have received extensive wind activity.
Problems
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.
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.