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Avalanche Forecast

Archived

Mar 23rd, 2017–Mar 24th, 2017

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Cariboos.

Tricky conditions persist in the alpine with fresh wind slabs and the continuing possibility of avalanches releasing on deep weak layers. Conservative terrain selection remains highly recommended.

Confidence

Moderate -

Weather Forecast

On Friday, 5-10 cm of new snow is expected with moderate to strong alpine wind from the southwest and freezing levels reaching around 1500 m in the afternoon. Another 4-8 cm is expected on Saturday with light to moderate alpine wind from the southwest, freezing levels around 1500 m in the afternoon, and the potential for sunny breaks. Mainly dry and sunny conditions are forecast for Sunday with light alpine wind and afternoon freezing levels around 1500 m.

Avalanche Summary

No new avalanches were observed on Wednesday. On Tuesday, a size 3 cornice released on a northeast aspect at 2800 m scrubbed down to rock and a size 2.5 storm slab released on a north aspect at 1900 m. Explosives released a cornice on a north aspect which triggered a size 3.5 deep persistent slab which stepped down to the November crust and to the ground in places. Explosives also released a size 2 cornice with a small slab and a size 2.5 persistent slab on a south aspect which failed on the mid-February crust layer down 120 cm. On Monday, several natural cornices released on north aspects and many triggered storm slabs. One of these triggered a deep persistent slab which failed on basal facets down 100 cm. Over the weekend, several natural storm slabs up to size 3 were reported and a cornice triggered size 3.5 persistent slab avalanche which failed on the February layer down 100 cm. Click here for photos of some recent avalanches.On Friday, wind slabs and cornices are expected to be reactive at higher elevations. We are in a low probability, high consequence scenario for persistent slab avalanches failing on buried weak layers. Click here for more details.

Snowpack Summary

A new sun crust is being reported on solar aspects. Below treeline, the snowpack is expected to be undergoing daily melt-freeze. At higher elevations, the mid-March crust is down 40-60 cm in the south of the region and shallower in the north. Recent strong winds from a variety of directions formed wind slabs in exposed terrain. The mid-February crust/facet layer is now typically down 100-140 cm and has recently been reactive with many avalanches stepping down to it. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches stepped down to these layers recently resulting in very large avalanches.

Problems

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.

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.