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Avalanche Forecast

Archived

Feb 25th, 2019–Feb 26th, 2019

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

Regions

South Columbia.

Buried wind slabs that are sitting on facets (weak, sugary snow) may remain reactive to human triggers for longer than what is typical in this region, especially in steep and rocky alpine terrain.

Confidence

High - The weather pattern is stable

Weather Forecast

MONDAY NIGHT: Clear / Light, northeasterly winds / Alpine low -18.TUESDAY: Sunny / Light, northeasterly winds / Alpine high -13.WEDNESDAY: Sunny / Light, northeasterly winds / Alpine high -6.THURSDAY: Mix of sun and cloud / Light, northeasterly winds / Alpine high -9.

Avalanche Summary

On Sunday, there were numerous human triggered wind slab and persistent slab avalanches up to size 1.5 reported. The wind slabs were  primarily on east aspects in the alpine and the persistent slabs were below treeline with the most notable one being in an open glade directly above a logging road at 1400 m.On Saturday, numerous natural and human triggered size 1.5 avalanches were reported on south aspects in the alpine and at treeline elevations. They failed on facets sitting on a recently buried sun crust.Several size 2, explosive triggered, persistent slab avalanches were reported in low elevation cut blocks south of Revelstoke on Saturday. Persistent slab avalanche activity on the mid-January weak layer has slowed down but not stopped, with human triggered avalanches on this layer being reported on a regular basis. Check out the great photos from a recent MIN. Take note of the low angle terrain and the light load of a single ski track that triggered this avalanche.

Snowpack Summary

5-15 cm of recent snow has been redistributed by moderate southwest winds, which is sitting on older wind slabs on a variety aspects. These buried wind slabs are sitting on facets (sugary snow) which may cause them to remain reactive to human triggers longer than what is typical for this region. Two additional weak layers of surface hoar have produced large avalanches in the region over the past month. A layer buried at the end of January is around 40 cm deep and a layer buried mid-January is between 60 and 90 cm deep. The mid-January layer may also be associated with a crust on southerly aspects. These layers are most prominent at treeline and below. The remainder of the snowpack is generally considered to be strong in most areas. However, isolated failures have occurred near the base of the snowpack in this region, or in neighboring regions, resulting in large, destructive avalanches. These avalanches have primarily been in steep, rocky, high alpine areas with a shallow snowpack.

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.