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Avalanche Forecast

Archived

Mar 25th, 2023–Mar 26th, 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.

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

10-20 cm of recent snow and light to moderate southwesterly wind may have formed small wind slabs on lee features below alpine ridgetops.

Confidence

High

Avalanche Summary

A couple cornice failures triggered loose dry avalanches up to size 2 on large alpine slopes on Friday.

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.

A size 2.5 deep persistent slab avalanche was reported Tuesday in the South Chilcotin range, around 2200 m on a south-facing slope.

Snowpack Summary

10-20 cm of recent snow and light to moderate southwesterly wind may have formed small wind slabs on lee features at upper elevations.

Below the new snow is a melt freeze crust exists on all aspects at treeline and below, and on solar aspects to mountain top. The only exception is high north aspects which had 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, which would result in a very large and destructive avalanche.

However, there remains a significant concern for human triggering in rocky, shallow, or thin-to-thick snowpack areas at treeline and above.

Weather Summary

Saturday Night

Partly cloudy / 5 km/h northwest ridgetop wind / Low temperature at treeline around -7 C / Freezing level valley bottom

Sunday

Mostly cloudy / 10 km/h southwest ridgetop wind / High temperature at treeline around -4 C / Freezing level 1300 m

Monday

Mix of sun and cloud / 15 km/h east ridgetop wind / High temperature at treeline around -1 C / Freezing level 1500 m

Tuesday

Sunny / 40 km/h northeast ridgetop wind / High temperature at treeline around -1 C / Freezing level 1500 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • 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.
  • Carefully evaluate steep lines for wind slabs.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

Problems

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.

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.