Avalanche Forecast

Issued: Jan 30th, 2018 5:22PM

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

Avalanche Canada mgrist, Avalanche Canada

Conditions remain primed for human-triggered avalanches. Give the snowpack time to settle before pushing into more aggressive terrain.

Summary

Confidence

Low - Due to the number and quality of field observations

Weather Forecast

Wednesday: Cloudy with isolated flurries. Light westerly winds. Alpine temperature near -10.Thursday: Occasional flurries (2-5 cm possible). Moderate south-westerly winds. Alpine temperature near -8.Friday: 5-10 cm snow. Light to moderate south-westerly winds. Alpine temperature near -6. More information can be found in the Mountain Weather Forecast.

Avalanche Summary

A widespread natural avalanche cycle to Size 3.5 was reported on Tuesday, with larger and more frequent avalanches in the north of the region where storm snow totals were higher. On Saturday near Kimberley, skiers remote-triggered two Size 2 avalanches, by a convex roll near 2000m elevation. Crown height was 60-70cm, suggesting the snow ran on the mid January layer. See the MIN report for more details. Conditions remain primed for human triggered avalanches, with the potential for some surprisingly large avalanches due to the structure of the snowpack.

Snowpack Summary

Large differences in storm snow totals were observed in the region on Monday into Tuesday: values ranged from 2 to 32cm!!! Overnight winds were strong to extreme from the south west and temperatures spiked to -3 at tree line. The current snowpack is complex, with three active weak layers that we are monitoring:1) 60-100 cm of recent storm snow overlies a crust and/or surface hoar layer (from mid-January). The crust is reportedly widespread, except for possibly at high elevations on north aspects. The surface hoar is 10 to 30 mm in size, at all elevation bands. The recent snow fell with strong south winds, producing wind slabs and cornices in lee features. 2) Deeper in the snowpack (down 70-100 cm), a persistent weak layer known as the early-January layer is present at all elevation bands, and composed of surface hoar on sheltered slopes and sun crust on steep solar aspects. Recent snowpack tests have shown sudden fracture characters with moderate loads and high propagation potential. 3) Another persistent weak layer that was buried mid-December is 80 to 120 cm deep and consists of a facet/surface hoar/crust combination. It is most problematic at and below tree line.

Problems

Storm Slabs

An icon showing Storm Slabs
Warming temperatures put heavier snow on top of lighter dry snow - a recipe for an unstable snowpack. A storm slab could step down to a deeper weak layer, creating a surprisingly large avalanche.
The new snow will take time to settle and stabilize.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Several weak layers are buried in the snowpack, creating very large avalanches when triggered.
Avoid open slopes and convex rolls where buried surface hoar may be preserved.Avoid thin, rocky or sparsely-treed slopes.Use conservative route selection, bearing in mind that avalanches may be surprisingly large.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Jan 31st, 2018 2:00PM