Weather Forecast
A low pressure system is tracking just south of the international border Wednesday, and the Purcells will see 5 to 10 cm of snow from the system Wednesday. Alpine winds will be strong out of the SW, but will quickly diminish as you drop in elevation. Wed. 1500m Temp: H: -3, L: -11. On Thursday a weak ridge builds back into the region and no significant precip is expected for most of the region. The exception will be in the Panorama area where 5 cm are expected to fall from convective flurries. Thur. 1500m Temp: H: - 4, L: -10. The ridge flattens back out on Friday, opening the door to zonal flow for most of the province. A few cm are expected each day: Fri, Sat & Sun.
Avalanche Summary
Numerous Natural, Explosive Controlled, Skier Controlled and Skier Remote avalanches to size 2.5 were reported on all aspects and elevations Monday, the majority of which failed on the Feb. 08 Surface Hoar.
Snowpack Summary
20-25 cm of dry light snow rests above the recent stiff windslabs. The upper snowpack structure is very complex. There are buried layers of surface hoar, buried melt-freeze crusts, and some buried crusts with facets. These weak sliding layers are buried anywhere from 40 - 80 cm by several different storm layers. There are some shears in the storm layers on decomposed and fragmented snow crystals. As the snow above the surface hoar layers settles into a cohesive slab, we are seeing easier and more sudden shears that are a bit deeper. The surface hoar is more likely to produce wider propagations, and lower angle fractures in areas where it is associated with a crust. The crust has been reported to be 2-3 cm thick in some areas. The mid-pack is generally well settled. Basal facets have not been reactive, but operators continue to monitor this layer in tests. Triggering this deep persistent weak layer is unlikely, but shallow snowpack areas or shallow weak areas adjacent to deeper wind loaded slopes are the most suspect locations.
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
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.