It's still possible to trigger large persistent slab avalanches throughout most of the region. This type of problem requires discipline and conservative decision making, even if you do not observe signs of instability.
Confidence
Fair - Freezing levels are uncertain
Weather Forecast
Tuesday: Mainly cloudy with showers or flurries – 5-10 cm. The freezing level should climb to around 1800 m. Ridge winds are light to moderate from the S-SW. Wednesday: Cloudy with flurries – 5-10 cm. The freezing level is around 1500 m and ridge winds are light to moderate from the W-SW. Thursday: Cloudy with flurries. The freezing level is around 1400 m and ridge winds are light.
Avalanche Summary
Recent avalanche activity has been limited with many areas reporting no new avalanches in the past several days. However, when we do hear reports they are often of large avalanches stepping down to deeply buried persistent weak layers, or even the ground. A size 3 accidentally skier triggered avalanche was reported on Sunday. This avalanche occurred on a steep west-facing alpine slope and stepped down to the ground (up to 2.5 m deep). One person was buried but was recovered without serious injury. On Saturday an anomalous sized 3.5 avalanche released naturally out of a SE facing feature at 2700m in the central portion of the region.
Snowpack Summary
15 - 25 cm of light density snow has fallen over the last few days. This snow is settling nicely and likely being formed into soft wind slabs immediately lee of ridge crest.Numerous crust can be found in the upper 30 cm of the snowpack on south facing slopes. These crusts produce sudden collapse failures in snowpack tests. A moderate shear persists down 30 - 50cm on the March 15 crust/surface hoar interface. Down 70 to 95cm below the surface you may find surface hoar and crusts buried at the beginning of March. This interface is still touchy in some areas, particularly in the north of the region. It also continues to produce sudden planar failures in compression tests.The deeper facet/crust persistent weakness buried at the beginning of February, now down 100 - 180cm, seams to be more active in this region than any other in the province and is still very difficult to trust. Needless to say, any avalanche at these deeper, persistent interfaces would be large and destructive. It continues to produce large destructive natural avalanches every few days. Weak basal facets exist in many areas, but without a large load, triggering is unlikely.
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.
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.