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Avalanche Forecast

Archived

Feb 28th, 2019–Mar 1st, 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.

Recently formed wind slabs are sitting on top of buried wind slabs that are sitting on facets (weak, sugary snow). The fresh wind slabs may still be touchy and the buried wind slabs are remaining reactive to human triggers longer than is typical.

Confidence

High - The weather pattern is stable

Weather Forecast

THURSDAY NIGHT: Cloudy with isolated flurries; 0-3 cm. / Light, northwesterly winds / Alpine low -13.FRIDAY: Cloudy with isolated flurries; 0-3 cm. / Light, northwesterly winds / Alpine high -11.SATURDAY: Sunny / Light, northeasterly winds / Alpine high -17.SUNDAY: Sunny / Light, northeasterly winds / Alpine high -14.

Avalanche Summary

On Wednesday, a few rider triggered wind slab avalanches up to size 2, on primarily northerly aspects at treeline and above were reported.Persistent slab avalanche activity on the mid-January weak layer has slowed down, but not stopped. This layer has created a low likelihood, high consequence scenario in the snowpack primary at lower elevations. 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.There are two prominent weak layers in the upper snowpack. One was buried at the end of January, and the other mid-January. They are approximately 40- 60 cm and 60-90 cm below the surface. Both layers consist of surface hoar (weak, feathery crystals) and may be associated with a crust on steep, south facing slopes. These weak layers have been most recently reactive at lower elevations below treeline.The lower snowpack is generally considered to be strong, except for shallow, rocky areas where the cold temperatures continue to facet (weaken) the 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.