Regions
Northwest Coastal.
Conditions are highly variable from north to south within the Northwest Coastal region. In the southern portion of the region, near Terrace and Kitimat, the hazard in the alpine is likely moderate.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
MONDAY NIGHT - Clear periods / light southerly winds / alpine low temperature near 0 / alpine temperature inversion TUESDAY - Mainly cloudy with flurries beginning in the afternoon / light southwest winds / alpine high temperature near +2 / alpine temperature inversionWEDNESDAY - Periods of snow, 10-15 cm / southwest winds 20-50 km/h / alpine high temperature near -2 THURSDAY - Periods of snow, 15-20 cm / south winds, 10-20 km/h / alpine high temperature near -1
Avalanche Summary
A widespread natural avalanche cycle to size 3.5 was reported on all aspects north of Stewart on Sunday. There were also two human triggered avalanches reported in this area on Sunday, one size 2 and one 2.5. These occurred on southerly aspects between 1500-1800 m.In the south of the region, closer to Terrace, there were reports of a natural avalanche cycle to size 3 in high alpine terrain on Sunday.On Saturday, observations were limited due to the ongoing storm. Several explosives triggered avalanches to size 2.5 were reported, and it is likely that a widespread natural avalanche cycle was occurring as well.
Snowpack Summary
Up to 40 cm of recent storm snow sits on a weak layer of surface hoar (feathery crystals), and a crust on sun-exposed slopes. The highest amounts of this new snow are north of Stewart and taper significantly as you head south.The recent precipitation fell mainly as rain below about 1200 m in the north and below about 1600 m in the south.In some areas, there is another layer of surface hoar that is now buried 50-70 cm. A weak layer of facets (sugary snow) buried in early December exists down 180-250 cm.Avalanches triggered within the new snow have the potential to step down to these deeper layers, resulting in very large avalanches.
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.
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.