Watch the temperature and solar warming this weekend, heat and/or direct sun could quickly initiate cornice fall and natural slab avalanche activity.
Weather Forecast
Synopsis: A ridge builds into the interior this weekend making for a fairly unexciting weather weekend. Look for high cloud, moderate freezing levels and no significant precipitation.Saturday: Freezing Level: 700m - 1100m; Precipitation: Nil; Treeline Wind: Light, SE | Ridgetop Wind: Light, W/SWSunday: Freezing Level: 600m - 900m; Precipitation: Trace; Treeline Wind: Light, SW | Ridgetop Wind: Light, W/NWMonday: Freezing Level: 1200m; Precipitation: Nil; Treeline Wind: Calm | Ridgetop Wind: Light, W
Avalanche Summary
We've received reports of size 2.5 and size 3 natural slab avalanches which occurred recently in the Quartz Creek area. The slides occurred on southwest facing alpine terrain with solar warming as a trigger. Sunny breaks over the next few days will likely reactivate weaknesses in the snowpack with the potential for very large avalanches.
Snowpack Summary
Light snow accumulations overlie a well-settled storm slab which formed last weekend. Under the storm slab you'll likely find small surface hoar in shaded terrain and crusts on previously sun-exposed slopes. Recent winds have redistributed surface snow into wind slabs in exposed lee terrain. Rain from the weekend saturated the snowpack at lower elevations and the more recent accumulations may overlie a refrozen crust. Up 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. The deeper facet/crust persistent weakness buried at the beginning of February, now down 60 to 160cm, has been highly variable in terms of reactivity and is still very difficult to trust. Needless to say, any avalanche at these deeper, persistent interfaces would be large and destructive.Weak basal facets exist in many areas, but without a large load, triggering now is unlikely.
Problems
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.
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.
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.