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Avalanche Forecast

Archived

Mar 27th, 2023–Mar 28th, 2023

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

Regions

South Coast Inland, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

Carefully evaluate steep lines for wind slabs before committing to them.

In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Confidence

High

Avalanche Summary

On Saturday there were reports of several small to large wet loose avalanches that started near the alpine on south-facing terrain. There was also a report of a skier-triggered size 1.5 wind slab avalanche that occurred in the alpine.

On Friday, a couple of cornice failures triggered loose dry avalanches up to size 2 on large alpine slopes.

A couple of deep persistent slab avalanches were reported this week. On Wednesday, a cornice fall entrained a mass of snow which then triggered a size 3 deep persistent slab avalanche. It occurred at 2350 m on a north east facing slope. On Tuesday, a size 2.5 deep persistent slab avalanche was reported in the South Chilcotin range, around 2200 m on a south-facing slope.

Snowpack Summary

At higher elevations, moderate southwesterly winds may have transported the 10 to 20 cm of recent snow and formed small wind slabs. Incoming moderate to strong easterly winds may develop new wind slabs where they typically do not occur.

Below the new snow is a melt-freeze crust that exists on all aspects at treeline and below, and on solar aspects to the mountain top. On high north aspects is a mixture of decomposing dry snow and small surface hoar in isolated locations.

The mid-snowpack is generally strong but the lower snowpack is a different story.

A weak layer of sugary facets is still prominent at the base of the snowpack. Small surface avalanches and cornice falls are the most likely things to trigger this layer. However, there remains a significant concern for human triggering in rocky, shallow, or thin-to-thick snowpack areas at treeline and above.

Weather Summary

Monday Night

Cloudy with clear periods, trace accumulation, winds northeast 10 to 20 km/h, freezing levels 1500 m.

Tuesday

Sunny, no accumulation, winds northeast 10 to 20 km/h gusting to 35, freezing levels 1600 m.

Wednesday

A mix of sun and cloud, no accumulation, winds variable and light, freezing levels reaching 1700 m. Thursday

A mix of sun and cloud, no accumulation, winds southerly and light, freezing level to 1800 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Carefully evaluate steep lines for wind slabs.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Avoid exposure to slopes that have cornices overhead.
  • 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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.