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Avalanche Forecast

Archived

Feb 28th, 2023–Mar 1st, 2023

Alpine
Natural avalanches possible, human triggered probable.
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, 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.

Overnight winds from the northeast may form fresh wind slabs on unexpected slopes. Be particularly cautious in wind-loaded areas and continue to make conservative terrain choices while the storm snow settles and stabilizes.

Confidence

Moderate

Avalanche Summary

On Monday, several natural storm slab and cornice failures were reported up to size 2. The cornice fall triggered a slab up to 50 cm deep from the slope below to size 2. Additionally, numerous explosive-controlled wind slab avalanches and cornices were reported up to size 2.

Last weekend, numerous natural and 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 occurred in alpine terrain.

Looking forward to Wednesday, human-triggered storm slabs remain possible, especially in wind-loaded areas. Storm slab reactivity is expected to persist for longer than is typical due to the weak surface they are sitting on.

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

Snowpack Summary

An additional 5-10 cm of new snow adds to last weekend's storm snow that brought 20-50 cm down to valley bottom. In some areas, this new snow has bonded poorly to the underlying surface consisting of stiff wind slabs and near-surface faceting formed by recent wind and cold temperatures.

There are two crusts with facets sitting above, which are buried in the snowpack down 60-180 cm 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

Tuesday Night

Clear periods. Alpine temperatures -10 °C. Ridge wind northeast 10-20 km/h. Freezing level valley bottom.

Wednesday

Cloudy with flurries up to 5 cm. of accumulation Alpine temperatures reach a high of -10 °C. Southwest wind 35 km/h and freezing level valley bottom.

Thursday

Snow amounts 10-20 cm. Ridgetop wind 40-55 km/h from the west. Alpine temperatures reach a high of -9 °C. Freezing level valley bottom.

Friday

Cloudy with sunny periods and isolated flurries. Alpine temperatures near -11°C. Ridge wind southwest 25 gusting to 50 km/h. Freezing level 900 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Carefully monitor the bond between the new snow and old surface.
  • Don't let the desire for deep powder pull you into high consequence terrain.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.