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Avalanche Forecast

Archived

Feb 27th, 2019–Feb 28th, 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.

Fresh wind slabs are sitting on top of buried wind slabs that are sitting on facets (weak, sugary snow). The fresh wind slabs are touchy and the buried wind slabs may remain reactive to human triggers longer than is typical for this region.

Confidence

High - The weather pattern is stable

Weather Forecast

WEDNESDAY NIGHT: Increasing cloudiness / Light, easterly winds / Alpine low -6.THURSDAY: Mostly cloudy with isolated flurries / Light, southwesterly winds / Alpine high -7.FRIDAY: Mostly cloudy with sunny periods / Light, northwesterly winds / Alpine high -12.SATURDAY: Sunny / Light, northeasterly winds / Alpine high -15.

Avalanche Summary

On Tuesday, numerous natural and human triggered wind slab avalanches up to size 1.5 were reported on a variety of aspects at treeline and above. These new wind slabs and/or the older buried wind slabs that are sitting on facets will likely remain reactive to human triggers for several days.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

Strong northeasterly ridge-top winds have created fresh wind slabs on lee features at treeline and above. Additionally, there are buried wind slabs on a variety of aspects that are sitting on facets (sugary snow) which may cause them to remain reactive to human triggers longer than what is typical for a wind slab problem in 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 treeline elevations. 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

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.