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Avalanche Forecast

Archived

Feb 28th, 2021–Mar 1st, 2021

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

Regions

Kootenay Boundary.

Watch for signs of instability in wind affected areas and steep openings in the trees where surface hoar may exist under the recent snow. 

Confidence

High - The snowpack structure is mostly striaghtforward and not unusually variable.

Weather Forecast

Sunday night: Flurries bringing a trace of snow. Freezing level 800 m. Wind moderate below 2000 m, strong southwest ridgetop wind.

Monday: Flurries bringing a trace of snow. Freezing level 1600 m. Wind moderate below 2000 m, strong southwest ridgetop wind.

Tuesday: Flurries bringing a trace of snow. Freezing level 1500 m. Moderate southwest wind.

Wednesday: Sunny. Freezing level 1700 m. Light to moderate southwest wind.

Avalanche Summary

On Saturday, wind/storm slabs were mainly stubborn to human triggers, with one report of a size 1.5 ski cut. Large explosive loads produced size 2-3 results at Kootenay Pass. A few of these large avalanches are suspected to have stepped down to the January layer described in the snowpack summary.

Snowpack Summary

At upper elevations, 20-40 cm of recent snow is likely undergoing continued transport by strong southwest wind. Recent wind direction has been predominantly westerly with some southerly or northerly components, depending on elevation. This recent snow may sit over a layer of small surface hoar crystals in isolated areas around treeline.

A couple of persistent layers exist 60-80 cm and 80-150 cm below the surface, having formed in mid-February and late January, respectively. These are composed of combinations of surface hoar, crusts and facets. The depth of these layers mean that they require very large loads to trigger, but when triggered they produce large, destructive avalanches. This has been demonstrated this weekend in Kootenay Pass. So while they are currently difficult to trigger in a recreational context under the current conditions, these layers remain on our radar.

Shallow snowpack areas in the east of the region may harbor a facetted basal snowpack as described in this MIN report. This structure is often a constant for thin snowpacks and can be managed with good travel habits of avoiding shallow rocky areas where the snowpack transitions from thick to thin.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Start on smaller terrain features and gather information before committing to bigger terrain.

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.