Weather patterns are divided across the the region: a clearing trend is forecast the north and continued precipitation is expected in the south. Forecast avalanche danger ratings most accurately reflect conditions in areas where snowfall continues.
Confidence
Poor - Forecast snowfall amounts are uncertain
Weather Forecast
The north of the region will see a clearing trend over the next couple of days while moderate snowfall will continue until Monday in the Coquihalla.Tonight and Sunday: Snow tapering off tonight, periods of snow sunday with locally higher amounts in the south of the region / Winds strong to extreme westerly / Freezing level 1100mMonday: Moderate snowfall in the south, dry in the north / Winds moderate to strong westerly / Freezing rising through the day up to 2000mTuesday: Cloudy / Winds moderate to strong southwesterly / Freezing continue to rise as high as 2500m.
Avalanche Summary
Natural and human triggered avalanche activity up to size 2.5 was report to have intensified Friday although these avalanche were a result of developing to storm slabs. Earlier in the week a deep slab avalanche was triggered by a snow cat at Whistler Blackcomb. This avalanche highlights the potential for large and deep avalanches in many areas on the South Coast. As heavy loading continues through the day expect more large deep avalanches.
Snowpack Summary
Saturday's storm clobbered the region with another 60-80 cm of snow. Around 80 -100cm of new snow now overlies a variety of old surfaces which may include surface hoar in sheltered terrain, wind-pressed snow in exposed areas, or a crust on previously sun-exposed slopes. Sustained moderate S-SW winds have loaded in exposed lee terrain and cross-loaded features. In the north of the region, the recent storm snow is sitting on a weak layer of buried surface hoar which formed in early December. Facets from early December's cold snap are a fairly common feature of the snowpack in this part of the region. In some areas, these facets may have formed around a buried crust. In shallow snowpack areas, the facets may exist at ground level. This storms heavy loading will provide the first test of these deep weakness.These deep persistent weak layers do not seem to be as prevalent in the south where the early season snowpack was deeper and was not as affected by early December's cold temperatures.Snowpack depths at treeline range from 170-250 cm in the south of the region, and from 90- 150 cm in the north of the region.
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.