Avalanche Forecast

Archived

Jan 31st, 2018–Feb 1st, 2018

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 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.

Regions

Kootenay Boundary.

Deeply buried weak layers exist throughout the region and a cautious approach remains critical. Don't let the lure of powder pull you into bigger terrain.

Confidence

High -

Weather Forecast

Thursday: 5-15cm of new snow / Moderate southwest winds / Freezing level at 1000mFriday: 2-4cm of new snow / Light southwest winds / Freezing level at 500mSaturday: Light flurries / Light and variable winds / Freezing level at 1500m

Avalanche Summary

Reports from Tuesday reflect increased visibility over terrain that was obscured during Monday's storm. Evidence of a natural avalanche cycle involving each of our persistent weak layers was observed, with numerous avalanches reaching Size 3.5 and several crown fractures up to 3 metres deep. These are believed to be some of the deepest crowns in the region's historical record. Here's a great MIN post from Kootenay Pass that details some of the recent activity.Looking forward, expect newly formed wind slabs and the persistent slabs beneath them to remain reactive to human triggers with the potential for very large and destructive avalanches.

Snowpack Summary

Recent storms have brought around 100 cm of snow to the region over the last couple of weeks. On Monday the recent precipitation fell as rain below about 1300 metres. Where it fell as snow, strong southwest winds have again redistributed it into touchy wind slabs.Aside from wind slab instabilities at the surface, the primary layer of concern from mid-January is buried beneath all the storm snow at 80-110cm deep. It is composed of a mixture of weak surface hoar and/or a crust. Numerous recent natural avalanches to size 2.5 have been reported on this sensitive layer and human triggering large, destructive avalanches on this layer remains likely.Below this layer lies a second crust/surface hoar interface buried early-January that is now 110-130 cm deep. Several recent avalanches have stepped down to this layer.The mid-December surface hoar layer is buried 120-150 cm below the surface. This layer has continued to produce step down releases and "sudden" test results. It is most pronounced at treeline, but is also present below treeline . Two laminated crusts created by rain events in late November lay just below the mid-December interface.

Problems

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.

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.