Avalanche Forecast

Archived

Jan 2nd, 2014–Jan 3rd, 2014

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Cariboos.

Confidence

Fair

Weather Forecast

Precipitation will continue through the night tapering off before dawn. Storm totals should be in the 20 30 cm range. The freezing level drops after the storm and a ridge of high pressure looks to dominate for the foreseeable future.Thursday Night: Freezing Level: 1000m; Precip 5/10mm - 5/15cmFriday: Freezing Level: 700m Precip: Nil; Wind: Mod NWSaturday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Mod NW Sunday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Light, Var.(Forecasted wind speeds are at 2000m)

Avalanche Summary

Reports of several natural and skier triggered avalanches on Tuesday. Natural avalanches up to size 2 in wind loaded features at treeline on various aspects. Ski cuts and skier accidentals size 1 from small pockets of wind loaded terrain features at treeline. Most of the recent reported activity has been limited to the storm snow and wind loading with depths varying from 20-40cm. However, there have been reports from last weekend of very large avalanches releasing deep within the snowpack (1 to 1.5m) in the Cariboos. Also on Tuesday, several very large, deep released avalanches occurred in the Selkirk Mountains. Continuing with the trend, a size 2.5 natural was observed on a steep NE face Wednesday. The potential in the Cariboos for very large, deep avalanches remains a major concern, especially with the additional loading on Thursday evening.

Snowpack Summary

Around 75 cm of new snow has fallen in the last week. Recent mild temperatures have caused substantial settlement of this new snow. This has created a slab around 20-40cm thick which may overlie softer snow creating an upside-down condition in the upper snowpack. Areas of the region have seen moderate to strong winds from the SW-NW resulting in variable wind slabs. Expect to find touchy wind slabs in exposed lee terrain at and above treeline. A buried rain crust exists below 1600 m and a couple buried weak layers (surface hoar or facets) are now down 80-100 cm deep. Snowpack depths vary, but in general 150 cm of snow can be found at treeline, with 100-200 cm in the alpine. In many places we're still dealing with a relatively thin snowpack (thanks to a windy early season) so there's not a whole lot of snow between riders and the sugary snow (facets) near the ground. The basal facet/crust combo has been recently active in parts of the region and continues to give easy to moderate results in snowpack tests. This basal weakness may be difficult to trigger but if triggered, may result in very large, destructive 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.

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.