The persistent slab problem is still on the radar, but shifting into a low-probability/ high-consequence situation. Be confident in your local snowpack before committing to any big terrain.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Light snow starts on Friday night and continues through the weekend. (Estimates: 5-15 cm on Saturday; 5 cm on Sunday). Only light flurries are expected on Monday. The freezing level is around 1500 m by day, falling towards valley floor by night. Winds are generally light.
Avalanche Summary
On Wednesday, several size 2-3 slabs failed naturally. While the likelihood of triggering a large persistent slab avalanche is decreasing slowly, the consequences remain high.
Snowpack Summary
10-20 cm dry convective snow has been shifted by NW winds into wind slabs on lee slopes in the alpine. These overlie a recently formed crust which varies in thickness with elevation. Several persistent weak layers exist in the upper 1m of the snowpack and remain a concern. The mid-March crust/facet layer is down around 60 cm and has been reactive to light triggers recently. Down around 80-100 cm is the mid-February crust/facet/surface hoar layer which has also been reactive to heavy loads like avalanches in motion stepping down, cornice failures, or explosives. Both layers have the potential for wide propagations and very large avalanches are still possible.
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.