Avalanche Forecast

Issued: Mar 23rd, 2017 4:24PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

rbuhler, Avalanche Canada

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.

Summary

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

Recent wind has been from a variety of directions and wind slabs should be expected in exposed terrain on all aspects at higher elevations. Cornices on northerly aspects are expected to be large and may become weak with daytime warming.

Use ridges or ribs to avoid pockets of wind loaded snow.Be alert to conditions that change with elevation.Use caution in lee areas. Recent wind loading has created wind slabs.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

Various persistent weaknesses throughout the snowpack create the potential for large step down avalanches. Sustained sun exposure or heavy triggers like a cornice fall could trigger a deep and destructive avalanche.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.If triggered, wind slabs or cornices may step down to deeper layers resulting in large avalanches.Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Mar 24th, 2017 2:00PM