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Avalanche Forecast

Archived

Dec 4th, 2021–Dec 5th, 2021

Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Kootenay Boundary.

A dusting of fresh snow may hide the solid crust which dominates the landscape. Where winds moved loose snow, thin windslabs may lurk in isolated terrain.

Confidence

Moderate - We have a good understanding of the snowpack structure and confidence in the weather forecast

Weather Forecast

SATURDAY NIGHT: Patchy clouds, clearing into the morning. Northwest wind, 25-35 km/hr. Alpine low temperature -12 C. Freezing level below 1000 m. 

SUNDAY: Mostly clear and sunny. Northwest wind, 25-40 km/hr. Alpine high temperature -9 C. Freezing level valley bottom. 

MONDAY: Isolated flurries overnight clearing and mostly sunny though the day. Southwest wind 10-20 km/hr. Alpine high temperature -9 C. Freezing level valley bottom. 

TUESDAY: Mostly sunny. West-northwest wind 10-20 with gusts to 40 km/hr. Alpine high temperature -10 C. Freezing level valley bottom.

Avalanche Summary

On Wednesday, Dec 1, large (size 2) natural wet avalanches failed in steep treeline features around the Highway 3 corridor near Stagleap Provincial Park. The Okanagan edge of the Kootenay-Boundary also reported evidence of a natural storm cycle up to size 2. 

Explosive control work on Tuesday, Nov 30 produced several size 2 wind slabs on eastern aspects in alpine features, these failed on a melt freeze crust. 

Over the previous week several size 1.5 - 2 storm slabs have been triggered near Nelson, and a natural avalanche cycle size 1-2 was observed from north facing alpine start zones.

Snowpack Summary

Up to 15 cm low density snow covers a widespread and supportive crust from last weeks deluge of rain. The snowpack is generally well consolidated, at upper elevations a few crusts may be found in the lower snowpack. At mid and lower elevations the entire snowpack was saturated and is now frozen and uniform.

Snowpack depths at treeline range from 50-110 cm, with alpine depths exceeding 120 cm in areas. Below 1800m, snowpack depths decrease rapidly with poor coverage in many below treeline areas.

This MIN from Dec 3 captures the K-B snowpack well. Note that there are very few field observations from the Kootenay Boundary Forecast Region. If you venture out in the mountains, please share your observations and photos on the Mountain Information Network

Terrain and Travel

  • Be alert to conditions that change with elevation and wind exposure.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

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.