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Avalanche Forecast

Archived

Feb 5th, 2019–Feb 6th, 2019

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

Regions

North Columbia.

The unusual danger rating is due to a buried weak layer that exists mainly at treeline and below. It is easily triggered by humans and there is the potential for large avalanches at lower elevations. Choose low angled terrain, especially in the trees

Confidence

High -

Weather Forecast

TUESDAY NIGHT - Clear with cloudy periods / northwest winds 10-15 km/h / alpine low temperature near -19WEDNESDAY - Mainly sunny / northwest winds 10-15 km/h / alpine high temperature near -16THURSDAY - Mainly cloudy with light flurries, 3-5 cm / southwest winds 10-20 km/h / alpine high temperature near -14FRIDAY - A mix of sun and cloud with scattered flurries / northeast winds, 15-25 km/h / alpine high temperature near -16

Avalanche Summary

Natural avalanche activity began to slow down on Sunday, but a persistent weak layer that was buried in mid January continues to be reactive to human triggers. This layer is sensitive enough for humans to trigger avalanches remotely (from a distance). Human triggered avalanches up to size 2.5 were reported on both Sunday and Monday. This layer is the most reactive at treeline and below treeline.This MIN report from Monday does a great job of illustrating the sensitivity of this weak layer.Widespread avalanche activity was reported on Friday and Saturday. Numerous natural and explosives triggered avalanches to size 3.5, and human triggered avalanches to size 2 were reported. Many of these avalanches were triggered remotely (from a distance) and failed on the mid January layer.Human triggered avalanches failing on the mid January persistent weak layer have been reported almost daily for the past two weeks in the North Columbia region.

Snowpack Summary

30-80 cm of recent new snow sits on surface hoar (feathery crystals), facets (sugary snow), wind slabs and a crust on sun-exposed slopes. In many areas, recent winds have redistributed the new snow, forming wind slabs on all aspects due to shifting wind directions.The most notable feature in the snowpack at this time is a persistent weak layer that was buried in mid January, which is now buried 50-100 cm. This layer consists primarily of surface hoar, however there is also a crust associated with it on sun-exposed slopes. This layer is the most prominent at treeline and below, and continues to be produce avalanches.

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.