The winds were howling today in our forecast region from alpine to valley bottom. Wind slabs will be the priority concern over the next 24hrs. The Jan 6th facets remain a concern are widespread and are showing no results to moderate sudden collapses.
Confidence
Moderate - Wind effect is extremely variable on Tuesday
Weather Forecast
Mainly cloudy with isolated flurries. Alpine temperature: High -6 °C. Ridge wind west: 35 km/h gusting to 85 km/h. Freezing level: 1400 meters.
Avalanche Summary
In Banff National Park on friday, a skier triggered avalanche resulted in a full burial and a second near full burial. This avalanche was a size 2.0 and it failed on the January 6th layer.
Snowpack Summary
Relatively warm temperatures and strong winds from the northwest are building wind slabs and having a 'reverse loading' effect. These wind slabs are building over top of the February 11th sun crust and melt-freeze crusts on solar aspects. The January 6th facet layer is widespread and is buried 40-70 cm from the surface. Results on the January 6th layer in test pits range from no results to sudden collapses in the moderate range.
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.