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Avalanche Forecast

Archived

Feb 6th, 2022–Feb 7th, 2022

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

Regions

Banff Yoho Kootenay.

We added a new persistent  problem to the bulletin due to a gradual increase in slab development over the Jan 30 interface. Though we have seen very few avalanches on this layer thus far. We expect this to change with more snow and settlement.

Weather Forecast

A small system is moving into the forecast region for the beginning of the week. The westerly flow is forecasted to deposit up to 15cm of snow over the next three days. Freezing levels for Monday and Tuesday will reach 1100m with daytime warming. Strong westerly winds are expected at upper elevations till Wednesday.

Snowpack Summary

Moderate winds continue to redistribute the 20-30 cm of recent snow at upper elevations creating wind slab on lee slopes. At tree line and below the recent storm snow is beginning to develop into a slab, which overlays the Jan 30 surface hoar and sun crust. This interface is found 20 to 30cm down. Shallow snowpack areas remain weak and faceted.

Avalanche Summary

A few natural avalanche obs today have show some activity on the Jan 30 persistent layer. A natural cornice release that pulled size 2 slab below was observed in the sunshine back country. Another observation of a natural size 1 in the Simpson burn, released on a steep role below tree line.  We suspect both these avalanches failed on the Jan 30.

Confidence

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.