Local avalanche conditions differ greatly across the region. In areas where until recently the snow pack has been unusually it is possible to trigger large and destructive avalanches. Now is a good time to make conservative terrain choices.
Weather Forecast
Synopsis: A clearing trend as a warm ridge builds over the region causing rising freezing levels. There is the possibility for some light precipitation Tuesday night as a cold front slides down the coast although this front will not displace the warm air.Tonight and Tuesday: Cloudy / Winds moderate to strong westerly / Freezing continue to rise as high as 2500m.Wednesday: Clearing with sunny periods / Winds moderate to strong westerly / Freezing level 2500m.Thursday: Sunny / Winds light wester / Freezing levels 3000m
Avalanche Summary
We've receive reports confirming a widespread natural avalanche cycle that ran through the weekends storm. Several large avalanches were observed in the north of the region that released at or close to the ground, confirming our suspicions of a deep persistent slab problem. There have also been several recent close calls with human triggered soft slab avalanches in Coquihalla region: a good reminder that although the avalanche problems in the south may be easier to manage storm and wind slabs are lingering.
Snowpack Summary
The weekends storm clobbered the region with between 80-100cm of new snow. Sustained moderate to strong south to southwest winds have created thick and reactive winds slabs extending far into lee features. In the north of the region, the storm snow fell onto a week layer of surface hoar from earlier in the month. In areas with a shallow or rocky snowpack facets exist immediately above the ground.Although on the surface things are starting to look more normal, it is important to remember that the new snow is sitting on a thin and weak midpack. This makes for a low probability high consequence avalanche scenario that is more commonly associated in the interior of the province. The "wait 48 hours and you're good" Coastal mantra does not apply as these conditions are likely to persist for some time.In the south of the region where the early season snowpack was deeper these persistent weak layers do not seem to be as prevalent.Snowpack depths at treeline range from 150-250 cm in the south, and from 90- 150 cm in the north. In glaciated terrain open and poorly bridged crevasses are everywhere although they are now hiding under a meter of unsupportive storm snow.
Problems
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.
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.