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Avalanche Forecast

Archived

Mar 12th, 2024–Mar 13th, 2024

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.

Regions

Sea To Sky, Brandywine, Homathko, Spearhead.

It's not a trustworthy snowpack. Fresh surface instabilities and deeply buried weak layers have combined to create dangerous avalanche conditions.

Confidence

Moderate

Avalanche Summary

Mondays reports included several size 2 to 2.5 wind slabs controlled with explosives in the Whistler area. These were 60 - 90 cm deep and propagated widely. More sheltered terrain produced 20 cm storm slabs with ski cutting.

Numerous size 2 slab avalanches were triggered by riders in the Whistler area on Sunday with crown depths of 40 to 80 cm. Explosive control also produced a few very large (size 3 to 4) avalanches that failed on the early February persistent weak layer.

Snowpack Summary

20-40 cm of new snow in the early week overlies previous wind slabs, low density snow in sheltered areas, and, in the Whistler area, a thin crust at treeline. It also brought 4-day storm totals in the region to 80 - 160 cm. Strong to extreme winds have continued to redistribute loose surface snow into thick slabs.

A weak layer composed of facets on a crust is buried beneath the recent snow, in wind-loaded areas now 150 to 250 cm deep. This layer remains sensitive to both human and natural triggers and is capable of producing very large, very destructive avalanches.

The snowpack below this interface is generally well settled and strong.

Weather Summary

Tuesday night

Cloudy with isolated flurries and a trace of new snow. 10 - 15 km/h west ridgetop wind. Freezing level remaining near 1000 m.

Wednesday

Mainly cloudy. 10 - 15 km/hr west or northwest ridgetop wind. Treeline temperature -4 °C with freezing level rising to 1300 m.

Thursday

Mainly sunny. 20 - 30 km/hr northwest ridgetop wind. Treeline temperature +5 °C with freezing level shooting to 3300 m.

Friday

Sunny. 15 - 25 km/h northwest ridgetop wind. Treeline temperature +10 °C with freezing level to 3500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid traveling in runout zones. Avalanches have the potential to run to the valley floor.
  • Remote triggering is a concern, watch out for adjacent and overhead slopes.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.