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Avalanche Forecast

Archived

Dec 29th, 2023–Dec 30th, 2023

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

Regions

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

Persistent slab avalanches remain a concern anywhere the snowpack is thin and/or variable.

Keep up good travel habits and cautious route-finding.

Confidence

Moderate

Avalanche Summary

On Friday, very large persistent slabs were naturally triggered (up to size 3) near Blackcomb Glacier and Whistler, with wide propagation from shallow rocky alpine northern slope. On Thursday, explosive control triggered numerous large storm slabs and cornice falls (size 2) and very large persistent slabs (size 2.5), some being remote-triggered. These avalanches involved up to 100-120 cm deep persistent weak layers that resulted in wide propagations.

Snowpack Summary

The snow surface is moist up to 2000 m where the recent 15-30 cm storm snow is rapidly settling due to warm temperatures on Friday. Between 50 and 100 cm of soft snow and heavily wind-affected snow overlies a layer of poorly bonded crusts and surface hoar. These have shown sensitivity to human triggers and snowpack tests recently, as well as recent natural and remote triggering avalanche activity. The lower snowpack is strong and bonded, and total snow depths remain below average.

Weather Summary

Friday Night

Cloudy with up to 5-10 cm of snow, alpine wind south 30 to 50 km/h, treeline temperature around 0 °C, freezing level lowering to 1600 m.

Saturday

Cloudy with 10-15 cm of snow, alpine wind south 50 to 70 km/h, treeline temperature around 0 °C, freezing level around 1600 m.

Sunday

Cloudy with isolated flurries, 1-3 cm of snow, alpine wind south 20 km/h, treeline temperature around -1 °C, freezing level around 1200 m.

Monday

Mostly sunny, no precipitation, alpine wind southwest 20 to 40 km/h, treeline temperature around -3 °C, freezing level at valley botom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.

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.