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Avalanche Forecast

Archived

Jan 6th, 2024–Jan 7th, 2024

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

Regions

Sea To Sky, Brandywine, Garibaldi, Homathko, Spearhead, Tantalus, Sky Pilot, Birkenhead.

The heavy dumping of fresh snow may need more time to stabilize. And also just barely cover lower elevation hazards.

Confidence

Moderate

Avalanche Summary

High winds and heavy snowfall limited observations late Friday. In the morning, explosives triggered storm slabs to size 1.5.

On Thursday, riders triggered avalanches to size 1.5 (10-30 cm thick) in the Whistler Backcountry. (see this MIN)

A crust deep in the snowpack (60-100 cm down) last produced avalanches Dec 31, and we suspect this layer is trending dormant.

Snowpack Summary

Over 50 cm in 24 hrs of snow accumulated by Saturday morning! Strong winds quickly impacted falling and loose snow, building reactive slabs and filling lees up to 100 cm deep.

Fresh and recent snow covers a crust buried Jan 1. This crust may exist up to mountain tops, and seems to be thick and supportive to the weight of a human south of Whistler, and more variable in thickness and strength to the north, where it thins out above 1900 m.

Around 30-60 cm off the ground, facets or isolated surface hoar cover an early Dec crust. This layer is trending dormant with the last avalanches occurring on Dec 31st. Snowpack depths 80-150 cm around treeline and decrease rapidly below.

Weather Summary

Saturday Night

Mostly clear skies with no precipitation. Northwest ridgetop wind to 20 km/h. Treeline temperature -15 °C.

Sunday

Mostly sunny with no precipitation. Northwest ridgetop wind 5-15 km/h. Treeline temperature -10 °C.

Monday

Increasing clouds with light flurries. Southwest ridgetop wind increasing to moderate. Treeline temperature -8 °C.

Tuesday

Snowing, 25-50 cm starting late Monday. Strong southwest ridgetop wind. Treeline temperature -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • The new snow may require another day to settle and stabilize.
  • Closely monitor how the new snow is bonding to the old surface.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Be carefull with sluffing in steep terrain, especially above cliffs and terrain traps.

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.