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Avalanche Forecast

Archived

Feb 2nd, 2021–Feb 3rd, 2021

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

Regions

Kootenay Boundary.

Avalanches are expected to be easy to trigger, especially in wind loaded areas.

Keep in mind that a persistent weak layer is now buried up to 80 cm. Avalanches on this layer will become harder to predict, so a conservative approach is important.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

TUESDAY NIGHT - Flurries, 5-15 cm / moderate southwest wind / alpine low temperature near -9

WEDNESDAY - A mix of sun and cloud / light northwest wind / alpine high temperature near -9 

THURSDAY - Mainly cloudy with a few flurries / moderate to strong west wind / alpine high temperature near -7 

FRIDAY - Mainly cloudy with sunny periods / moderate northwest wind / alpine high temperature near -6 

Avalanche Summary

Triggering avalanches remains likely on Wednesday, especially in wind loaded areas.

There were numerous reports of size 1.5-2 natural, human and explosives triggered avalanches in the region on Monday. Many of these failed on the recently buried persistent weak layer.

There were numerous size 1-2.5 natural, human and explosives triggered avalanches reported on Sunday. Several of these were reported to have failed on the recently buried persistent weak layer.

On Thursday and Friday, there were numerous reports of size 1-2 human triggered avalanches. These avalanches failed on the recently buried persistent weak layer.

Snowpack Summary

There is now about 50-80 cm of recent storm snow sitting above a persistent weak layer that consists of facets in some areas, a melt-freeze crust in many areas, on a sun crust on steep south-facing slopes, and large surface hoar in sheltered areas.

There are potentially several more layers of surface hoar in the upper snowpack, with the most notable one down about 80-120 cm. This layer was buried in early January. 

A couple of crusts surrounded by weak faceted grains are buried deep within the snowpack and appear to be unreactive.

Terrain and Travel

  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Avoid freshly wind loaded terrain features.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.