Avalanche Forecast

Archived

Feb 24th, 2019–Feb 25th, 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.

A persistent weak layer that has been most pronounced at lower elevations has created a low likelihood, high consequence scenario that requires discipline and careful terrain selection to manage effectively.

Confidence

High - The weather pattern is stable

Weather Forecast

SUNDAY NIGHT: Clear / Light, northeasterly winds / Alpine low -15.MONDAY: Sunny / Light, northeasterly winds / Alpine high -12.TUESDAY: Sunny / Light, northeasterly winds / Alpine high -14.WEDNESDAY: Sunny / Light, northeasterly winds / Alpine high -6.

Avalanche Summary

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. This brings total recent snowfall amounts to 20-60 cm which overlies a weak layer of surface hoar (feathery crystals) and crust that was buried in early February.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.