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Avalanche Forecast

Archived

Feb 26th, 2023–Feb 27th, 2023

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

Regions

Sea To Sky, Brandywine, Garibaldi, Homathko, Powell River, Spearhead, Tantalus, Sasquatch.

Don't let good visibility and the desire to ride deep powder lure you into consequential terrain. Natural activity may taper but human-triggered storm slabs remain LIKELY! Sheltered and shaded terrain will offer the best and safest riding.

Treat the avalanche danger as HIGH and avoid avalanche terrain and overhead exposure during periods of strong solar radiation.

Confidence

Moderate

Avalanche Summary

Earlier in the week, numerous natural and human-triggered wind slabs (size 1-2) were reported throughout the region as strong northerly outflow winds redistributed surface snow and create stiff pockets of wind slab. These slabs occurred on a variety of aspects in the alpine all the way down to below treeline terrain.

On Sunday, numerous human-triggered storm slabs up to size 2 were reported from all aspects and elevations. Observations were limited due to visibility, but we suspect a natural cycle will have occurred in alpine terrain.

Looking forward to Monday, dangerous avalanche conditions will persist. Expect human-triggered storm slabs to be likely, especially in wind-loaded areas and on sun-exposed slopes.

For a deeper dive into conditions leading up to Saturday's storm, check out this awesome South Coast Conditions Report posted by Zenith Guides.

Snowpack Summary

Saturday night's storm brought 20-50 cm of new snow down to valley bottom. This new snow has bonded poorly to the underlying surface consisting of stiff wind slabs and near-surface facetting formed by recent wind and cold temperatures.

There are two crusts with facets sitting above, which are buried in the snowpack down 60-180cm in the alpine and treeline elevation bands. These crust/facet layers have been responsible for a few large avalanches in the past 2 weeks in the Brandywine and Pemberton Icefield areas.

The remainder of the mid and lower snowpack is well-settled, strong, and consolidated.

Weather Summary

Sunday night

Clear periods with isolated flurries. Alpine temperatures drop to a low of -12 °C. Ridge wind southwest 15-35 km/h. Freezing level at valley bottom.

Monday

A mix of sun and cloud. Alpine temperatures reach a high of -10 °C. Ridge wind light from the southwest. Freezing level 700 metres.

Tuesday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -9 °C. Ridge wind light variable. Freezing level at valley bottom.

Wednesday

A mix of sun and cloud. Alpine temperatures reach a high of -11 °C. Ridge wind southwest 10-20 km/h. Freezing level at valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Give the new snow several days to settle and stabilize before pushing into bigger terrain.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Brief periods of sun could quickly initiate natural avalanche activity.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.