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Avalanche Forecast

Archived

Dec 13th, 2022–Dec 14th, 2022

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

Regions

Glacier.

Why are forecasters pounding their palms and pontificating about persistent weak layers?!

There is uncertainty of if/when the tipping point will be reached on the persistent weak layers, which would likely result in the wide propagating avalanches seen adjacent to Rogers Pass.

Have a look at a blog from the Avalanche Canada forecasters on how to manage a persistent slab problem in the backcountry.

Confidence

Moderate

Avalanche Summary

More reports came in about unsupported pockets of soft slab failing on Dec 5 and Nov 17, mainly occurring around treeline and morainal features. Most avalanches were small (sz 1 or less), but still large enough to bury a person in a terrain trap.

Scary persistent slab incident in the RMR backcountry from Monday; see MIN report.

Snowpack Summary

Up to 40cm of settled snow now buries the Dec 5 layer, which consists of surface hoar, preserved stellars, facets, and a thin sun crust on steeper solar aspects.

The Nov 17th Surface Hoar is now buried 60-90cm and continues to produce sudden results in snowpack tests.

Weather Summary

The ridge over interior BC continues to hold, leaving us with a mix of sun/cloud, nil precipitation, temps ranging from -5*C to -9*C, and light ridge-top winds, switching from Westerly to Northerly. No snow is forecasted until possibly the weekend.

Terrain and Travel Advice

  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Uncertainty is best managed through conservative terrain choices at this time.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.