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Avalanche Forecast

Archived

Feb 2nd, 2020–Feb 3rd, 2020

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

Regions

Kootenay Boundary.

Where loose snow or wind slabs overly a crust, it can provide an easy sliding surface for avalanches. Where a thick, supportive crust sits on the surface, avalanches are unlikely.

Confidence

High - The snowpack structure is generally well understood.

Weather Forecast

Sunday night: Mostly clear with isolated flurries in the early morning. Light to moderate northwest wind. Freezing level valley bottom.

Monday: Sunny. Light to moderate north wind. Alpine high -9 C. Freezing level valley bottom.

Tuesday: Mix of sun and cloud. Light northwest wind becoming strong at ridgetop. Alpine high -8 C. Freezing level valley bottom.

Wednesday: Mostly cloudy with isolated flurries. Moderate to strong northwest wind. Alpine high -5 C. Freezing level 600 m.

Avalanche Summary

Small loose dry sluffs running on the rain crust were been observed in wind sheltered areas on Sunday. On Friday and Saturday, a widespread storm slab avalanche cycle was observed size 2-2.5 on all aspects above 1600 m. 

Reports of deep persistent avalanches have been periodically coming in over the past few weeks, primarily from the western Boundary area but most recently on Saturday near Nelson. These large, deep avalanches are generally triggered by very large loads (cornice falls or vehicles) or from shallow, rocky snowpack areas.

Snowpack Summary

Strong southwest wind during the storm has scoured windward aspects and formed loaded pockets in alpine lees. As high as 2000 m, the upper snowpack contains a series of crusts from recent warming and rain events.

A layer of surface hoar is buried 100-150 cm below the surface in sheltered areas around treeline but has not been associated with avalanche activity recently. Weak basal facet/crust layers are particularly noteworthy in the western Boundary area.

Terrain and Travel

  • Be alert to conditions that change with elevation.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Keep in mind the crust offers an excellent bed surface for avalanches.
  • 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.