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Avalanche Forecast

Archived

Dec 14th, 2021–Dec 15th, 2021

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

South Coast Inland.

The current persistent slab problem is best managed through conservative terrain choices and disciplined backcountry travel techniques.

Avoid likely trigger spots such as steep, rocky terrain, with a shallow or thin to thick snowpack.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to the limited number of field observations.

Weather Forecast

TUESDAY NIGHT: Partly cloudy / Moderate, southwesterly winds / Low of -12 C / Freezing level surface.

WEDNESDAY: Cloudy / Light, southwesterly winds / High of -5 C / Freezing level 500 m.

THURSDAY: Mix of sun and cloud / Light, northwesterly winds / High of -7 C / Freezing level 200 m.

FRIDAY: Mix of sun and cloud / Moderate, northwesterly winds / High of -9 C / Freezing level surface m.

Avalanche Summary

Check out this recent MIN report of a naturally triggered size 3.5 storm slab avalanche reported on Sunday near Mt. Pierce.

In the neighboring Sea to Sky region, we received recent reports of four large (size 2-2.5) explosive-triggered persistent slab avalanches failing on the early December crust/facet layer. These occurred on northwest and northeast aspects in the alpine.

Snowpack Summary

70-90 cm of recent snow and strong winds have formed wind slabs on lee features at treeline and above.

In the north of the region, weak faceted snow can be found 50-70 cm deep on a crust that formed in early December. This layer has shown reactivity in the neighboring Sea to Sky region. This persistent slab problem warrants careful evaluation and conservative route-finding as the recent snow consolidates into a more cohesive slab over the weak layer.

The south of the region has seen substantially higher snow totals over the past week, with areas near the Coquilhalla seeing over a meter of accumulation since Monday. Expect to find deeper snow accumulations above the December crust and anticipate larger slab avalanches. 

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Uncertainty is best managed through conservative terrain choices at this time.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Problems

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.

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.