The persistent slab will be with us for sometime particularly with the buried Jan 28th surface hoar/facet layer down 50-80cm. Its sporadically distributed so difficult to predict.
Weather Forecast
Tuesday will be -12 to -4, flurries with 5cm of snow and Light S winds. Clouds, scattered flurries, freezing level around 1600m, and seasonal temperatures will be the rest of the week.
Snowpack Summary
Weak crust on S through W aspects. Dry, facetted and generally unsupportive facets below this crust. Wind slab on lee aspects from previous SW winds and persistent slab in open areas at tree line. Poor travel conditions below tree line due to weak facetted snowpack. The Jan 28 SH/FC layer down 80cm remains a concern but is sporadically distributed.
Avalanche Summary
On Sunday, a size 3 avalanche was triggered by a skier on a SW facing alpine slope at 2300m about 5km up Portal Creek off Pevril peak. The sliding layer was a 2cm thick layer of facets/decomposed surface hoar buried 80cm. It was 150m wide x 50cm deep (max 1.3m) x 600m long. Likely triggered in shallow spot and stepped down to ground a couple spots.
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.