Regions
Northwest Coastal.
Confidence
Fair - Intensity of incoming weather systems is uncertain on Friday
Weather Forecast
Friday: Continued moderate snowfall / Strong southwest winds / Freezing level at 500mSaturday: Light snowfall becoming moderate to heavy overnight / Strong southwest winds / Freezing level at 800mSunday: Light snowfall / Strong southwest winds / Freezing level at surface
Avalanche Summary
Numerous size 2 natural storm slab avalanches were observed on Wednesday. As well, a few size 2.5 storm slab avalanches were remotely triggered from up to 200m away. This speaks to the highly touchy nature of the current instability. Due to the nature of the buried weak interface and forecast weather, ongoing destructive storm slab activity will continue.
Snowpack Summary
In many areas over 60cm of recent snowfall overlies a medley of old surfaces which include: weak surface facets, surface hoar, a scoured crust, or any combination thereof. Reports from the field indicate a very poor bond between the new snow and these old surfaces with accounts of whumphing and easy, sudden planar snowpack tests. Strong winds and slight warming have added cohesion to the new storm slab, and have shifted the new snow into deeper, destructive wind slabs in exposed terrain. The mid and lower snowpack are generally strong and well-settled. Basal facets and depth hoar are likely to exist in some parts of the region, but triggering has become unlikely.
Problems
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.