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Avalanche Forecast

Archived

Dec 13th, 2023–Dec 14th, 2023

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

Regions

Purcells, Dogtooth, East Purcell.

Choose conservative terrain, weak layers in the mid and lower snowpack remain primed for human triggering.

Confidence

Moderate

Avalanche Summary

On Tuesday, numerous wet loose avalanches were reported on steep, south-facing slopes up to size 1. Explosive control was able to trigger a size 2 deep persistent slab that ran on the buried weak layer of surface hoar and facets.

Human-triggered avalanches are likely at treeline and in the alpine.

Snowpack Summary

Variable snow surfaces exist including new surface hoar development and wind affected snow. Down 30-45 cm exists a rain crust. This has been observed up to 1900 m near Golden and 2200 m near Invermere.

A concerning layer of surface hoar is now buried 40-70 cm deep.

The middle and base of the snowpack holds large, weak snow crystals. A hard crust may be found near the ground.

Treeline snowpack depths are variable and generally range between 60 and 110 cm. Snowpack tapers rapidly as you move lower in elevation.

Weather Summary

Wednesday Night

Cloudy with new snow 5-10 cm. Ridgetop wind 20-30 km/h and temperatures near -5 C. Freezing level valley bottom.

Thursday

Cloudy with a trace of new snow. Ridgetop wind 20-30 km/h and temperatures near -3 C. Freezing level near 1600 m.

Friday

A mix of sun and cloud. Ridgetop wind 20 km/h and temperatures near -2 C. Freezing levels 1500 m.

Saturday

Mix of sun and cloud. Ridgetop wind light and temperatures near -4 C. Freezing level valley bottom but an alpine temperature inversion may exist.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Stay off recently wind loaded slopes until they have had a chance to stabilize.
  • Make conservative terrain choices and avoid overhead hazard.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.