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Avalanche Forecast

Archived

Dec 10th, 2022–Dec 11th, 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.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Purcells, Dogtooth, East Purcell.

Be on the lookout for changes in the snow as you transition into wind-affected terrain.

Use the terrain to your advantage in accessing the best and safest riding.

Confidence

Moderate

Avalanche Summary

An avalanche, size two, produced naturally from a wind slab was reported in our area. Suspect the possibility of more of these as you travel through the backcountry. Regional neighbours are also reporting evidence of avalanches produced from the weaker layer further down in the snowpack.

Snowpack Summary

In the last 36 to 48 hours southwest winds have been transporting the up to 15 cm of new snow that fell during this time period as well. New snow and new wind slabs are sitting on older wind slabs that were created from strong westerly winds that occurred earlier in the week.

A buried layer of surface hoar sits 20 to 30 cm deep and remains a layer of concern, especially once a stiffer slab becomes established above it.

Generally speaking, we have a thin snowpack that has experienced a period of prolonged cold temperatures. The combination of the two has created a weakened snowpack by promoting faceting as a whole.

The overall height of snow is highly variable throughout the region with around 40 to 140 cm in the alpine.

Weather Summary

Saturday Night

Cloudy with clear periods, 2 to 4 cm accumulation, wind southeast 20 km/h, -7 C at 1500 m.

Sunday

A mix of sun and cloud, trace accumulation, winds southeast 15 km/h, -5 C at 1500 m.

Monday

Cloudy with sunny periods, trace accumulation, winds northeast 10 km/h, -6 C at 1500 m.

Tuesday

A mix of sun and cloud, no accumulation, winds northeast 10 km/h, -10 C at 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Be especially cautious as you transition into wind affected terrain.

Problems

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.

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.