The persistent slab problem is shifting into a low-probability/ high-consequence situation. Be confident in your local snowpack before committing to any big terrain.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Sunday
Weather Forecast
Light snow fall (5-15 cm) is expected on Saturday and Sunday, petering to flurries on Monday, with a chance of sun. The freezing level is around 1500 m by day, falling towards valley floor by night. Winds are generally light.
Avalanche Summary
A handful of recent large avalanches have been reported over the last few days. Many of these have been on north aspects, with the odd event on other aspects. There has also been a number of cornice falls.
Snowpack Summary
Recent squally snow showers have brought 10-25 cm of snow, which has been shifted into wind slabs. This new snow sits above a crust which varies in thickness with elevation. Cornices are large and should be given a respectful berth.Two crust/facet interfaces, formed in March and February, sit about 80-120 cm deep in the snowpack. These weaknesses are becoming more stubborn to trigger, but still react in snowpack tests and have potential for wide propagations and very large avalanches if triggered. Most likely trigger spots would be thin snowpack areas, or with a large load like a cornice fall.Basal facets are on operators' list of concerns. Deep snowpack issues sometimes wake up in the spring, so should not be forgotten.
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.