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Avalanche Forecast

Archived

Jan 10th, 2021–Jan 11th, 2021

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

Regions

Sea To Sky.

New slabs are likely to be touchy to riders and the snow will load buried weak layers that recently produced destructive avalanches. Now is the time to adopt a conservative mindset and give the snowpack time to stabilize.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

SUNDAY NIGHT: Cloudy with snowfall, accumulation 5 to 15 cm with the most in the west of the region, 40 km/h southwest wind, alpine temperature -4 C.

MONDAY: Cloudy with snowfall then clearing, accumulation 10 to 20 cm, 30 km/h southwest wind, alpine temperature -4 C.

TUESDAY: Cloudy with snowfall, accumulation 30 to 50 cm, 40 km/h southwest wind, alpine temperature -2 C.

WEDNESDAY: Cloudy with snowfall, accumulation 20 to 40 cm, 30 km/h southwest wind, alpine temperature -6 C.

Avalanche Summary

A large (size 3) avalanche was remotely triggered by skiers on Cowboy Ridge near Whistler on Saturday. The avalanche occurred on a north to northwest aspect at around 1900 m. The crown ranged reached up to 200 cm and was approximately 200 m wide. Check out this MIN for photos and more information. A similar avalanche was remotely triggered by skiers on a nearby westerly slope on Thursday; check out this MIN for more info and photos.

These avalanches are clear evidence that the weak layers described in the Snowpack Summary are still triggerable by riders and the consequence of being caught would be high.

Otherwise, small storm and wind slab avalanches were triggered by riders and naturally on Saturday and Sunday, generally 10 to 30 cm deep, on north to northwest aspects, and at treeline and alpine elevations.

Snowpack Summary

New storm and wind slabs will form during Sunday night into Monday's storm. The storm is expected to drop around 15 to 30 cm of snow, with the most in the west of the region. The storm will come with strong southwest wind so wind slabs are expected at higher elevations.

The snowpack is currently quite complex. Numerous layers of surface hoar may be found in sheltered terrain in the top 100 to 150 cm. The area of greatest concern is around 100 to 200 cm deep, where surface hoar or sugary faceted grains may sit above a hard melt-freeze crust from early December. There have been several recent large natural and human-triggered avalanches on this layer, particularly around Whistler and Pemberton.

Near the base of the snowpack there may be faceted grains above a crust from early-November, which was identified as the failure layer in recent sporadic large avalanche releases.

Terrain and Travel

  • Watch for fresh storm slabs building throughout the day.
  • Be careful as you transition into wind affected terrain.
  • Make conservative terrain choices and avoid overhead hazard.
  • Be mindful that deep instabilities are still present and have produced recent large avalanches.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.