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Avalanche Forecast

Archived

Mar 20th, 2022–Mar 21st, 2022

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

Regions

Little Yoho.

We have a lot of uncertainty about the sensitivity and distribution of the current windslab problem. Observations from the high alpine are limited, but given our observations of drifting snow at ridge crests, we're concerned about windslab formation.

Weather Forecast

A weak ridge over the area gives clearing skies overnight Sunday, but on Monday we switch to a SW flow (storm track) and clouds move into the area. No precipitation is expected and light winds; a similar day as was Sunday. Tuesday expect a RAPID warm-up and strong SW winds with FL's exceeding 2000m for Wednesday and snow/rain on the way.

Snowpack Summary

20-50 cm of storm snow is forming fresh wind slabs in alpine and some open treeline terrain with mod-strong SW winds. On solar aspects three different buried sun-crusts down 30-70 cm are producing moderate results in tests and remain a significant concern.

Avalanche Summary

No new activity reported Sunday. Explosive control in Kootenay Park on Thursday produced unexpectedly large avalanches at low elevations. On Sunday, Bourgeau-Left waterfall (next to Sunshine gondola) released a large natural avalanche that ran over the waterfall and hit Healy Creek. This may have been triggered by a cornice or strong solar effect.

Confidence

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.