Touchy persistent slab + new snow + rising temps + strong winds = a good recipe for avalanches
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
A Pacific front embedded in a southerly flow brings snow (10-40 cm total), strong S to SW winds and freezing levels rising to around 1600 m on Thursday and Friday. Precipitation and winds ease and temperatures drop on Saturday.For more details check out https://avalanche.ca/weather.
Avalanche Summary
Numerous large (size 2-3) persistent slabs failed naturally or with human triggers on Tuesday. Many of these were remotely triggered, highlighting the extreme sensitivity of the buried weak layer. This activity has been creeping up in size and frequency over the last few days and now seems fairly widespread, apart from in isolated parts of the region where there is insufficient snow or cohesion for a slab.
Snowpack Summary
20-50 cm of recent storm snow has formed a reactive slab over a volatile layer of buried surface hoar in many places. The buried surface hoar may be most prevalent at and below treeline. At higher elevations, this interface may exist as a crust/facet combo, which is also highly reactive. Incoming snow, with warming and strong winds, will increase the size and likelihood of the persistent slab problem, as well as adding new storm slab problems. The mid and lower snowpack are generally strong with any weak layers considered dormant for now. Snowpack depths are variable and shallow snowpack areas may have weak facetted crystals near the ground.
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.