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Avalanche Forecast

Archived

Feb 13th, 2021–Feb 14th, 2021

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

Regions

Banff Yoho Kootenay.

New wind slabs have been observed over the last 24 hours as well as cornice failures. We have added a persistent layer mainly for the Kootenay region as we keep getting isolated reports including Saturday.

Weather Forecast

After another -25 to -30C morning, temperatures will rise again on Sunday with highs at treeline of between -12 to -16 C. Skies will remain mainly clear. Alpine winds will decrease to light and will switch to a more Westerly flow. We will see a gradual increase in temperature over the next week.

Snowpack Summary

Winds have created small slabs in lee areas of the alpine, and wind effect in open alpine and treeline areas. The surface snow is facetting quickly and beginning to sluff more easily in steep terrain. A facet layer from Jan 27th is present at treeline and in the alpine down 30-40cm. On steep south this layer may consist of a thin sun crust as well.

Avalanche Summary

Increased winds saw some loose dry activity in steep alpine terrain. Cornice failures have been observed over the past few days including one on Fatigue Mountain today that triggered a size 3 on the ground reminding us that there is still a deep layer. Forecasters ski cut a size 2 in the Simpson area at 2100 m on the persistent layer that ran 450m.

Confidence

Due to the number and quality of field observations

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.