Regions
Northwest Coastal.
Snowfall warnings and strong winds mean elevated hazard during and after the storm. Conservative terrain choices and good route finding skills are imperative until the new snow has had a chance settle.
Weather Forecast
More snow is on the way, amounts from 15-25 cm are expected overnight on Monday. Tuesday: Snow, accumulation 10-15 cm, Strong west wind. Alpine temperature near -5. Freezing level 900 m.Wednesday: Snow, accumulation 15-25 cm. Strong southwest wind. Alpine temperature near -5. Freezing level 800 m.Thursday: Flurries, accumulation 5-10 cm. Moderate southwest wind. Alpine temperature near -5. Freezing level 700m.
Avalanche Summary
No recent avalanches have been reported, although observations from the Terrace area report shooting cracks within the recent storm snow, see the Mountain Information Network (MIN) post from Nov 25. Looking forward, high winds and snowfall rates are forecasted to rapidly load the snowpack and establish very dangerous avalanche conditions for the next few days. Any travel in avalanche terrain will require very conservative route-finding and travel practices. Please post your observations to the MIN.
Snowpack Summary
Approximately 30-60 cm of recent new snow forms the upper snowpack. This storm snow lies on a supportive crust that formed as a result of last week's warm, rainy weather. Below the crust are two weak layers that were noted to have formed in the early season (November 11 and October 31). Recent snowpack tests report easy to moderate, sudden, compression test results within the storm snow as well as moderate to hard, sudden results on both of the deep weak layers. Beneath the October 31 layer which is 20-30 cm above the ground, are several more thin crusts and large sugary snow crystals that are reported to be showing signs of improved bonding. Snowpack depths average 100-160 cm between 800 m and 1100m elevation in the south of the region.In the north near Ningunsaw, reports describe a a much shallower snowpack. Here, a possible 20-30 cm of recent storm snow may now overlie a thin lower snowpack composed mainly of weak, sugary snow. Snow depths in this part of the region range from 50-100 cm between 600 and 1100 m elevation.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.