Regions
Northwest Coastal.
Give recently wind-loaded slopes a wide berth.
Confidence
Fair - Intensity of incoming weather systems is uncertain on Sunday
Weather Forecast
Expect 10-15 cm snow on Saturday with strong S to SW winds and the freezing level near 900 m. A second system is forecast to affect the area on Sunday, petering out slowly on Monday. Anywhere from 10-40cm snow is expected, with strong S-SW winds and freezing level around 800 m.
Avalanche Summary
A skier triggered a size 1 wind slab on Thursday. Size 2 glide slabs were also reported to have failed naturally in the Skeena highway corridor. On Wednesday, naturally triggered wind slabs were reported at around 1800 m on N to NW aspects. Observations have been limited during the storm.
Snowpack Summary
Strong winds have redistributed the recent storm snow into wind slabs, and rain is saturating the surface of the snowpack to at least treeline elevations. Above treeline, a rain crust and a buried surface hoar layer 10-20cm below the surface have been reported. The mid-December crust/facet layer exists throughout the area where it hasn't been wiped out by recent avalanche activity. The November crust near the bottom of the snowpack is generally well bonded but may still be reactive in areas with a shallow snowpack.
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.