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Avalanche Forecast

Archived

Dec 8th, 2022–Dec 9th, 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, Esplanade, Dogtooth, East Purcell.

Wind slabs are showing reactivity to rider-triggered avalanches.

Weaker layers buried further down may be triggered where the snowpack is shallower.

Terrain choice will be key in seeking out the best and safest riding.

Confidence

Low

Avalanche Summary

Skier-triggered avalanche from a wind slab was reported south of the Golden area on Wednesday. Signs of whumpfs and cracking were also reported.

Rider-triggered avalanches are to be suspected throughout our region in wind-affected terrain.

On Sunday there were reports of avalanches failing on the Mid-November surface hoar layer. Triggering this layer is still possible.

Thank you to those reporting your observations. If you head out into the backcountry please continue to support your community by sharing in the MIN.

Snowpack Summary

Around 10 cm of new low-density snow has fallen in recent days. Consistent and strong westerly winds likely transported what snow was available. Fresh wind slabs in the alpine and treeline. In exposed terrain, some slopes have been scoured back to rock.

A buried layer of surface hoar sits 15 - 30 cm deep and remains a layer of concern, especially once a stiffer slab sits above it.

The prolonged cold temperatures have weakened the generally thin snowpack, promoting faceting as a whole.

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

Weather Summary

Thursday Night

Mostly cloudy, trace accumulation, wind south 20 km/h, temperature -6 C at 1500 m.

Friday

A mix of sun and cloud, trace accumulation, winds south 15 to 25 km/h, temperature -8 C at 1500 m.

Saturday

Cloudy with sunny periods, 2 cm accumulation, winds southeast 20 km/h, temperature -10 C at 1500 m.

Sunday

A mix of sun and cloud, trace accumulation, winds northeast 10 km/h, temperature -9 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.
  • In times of uncertainty conservative terrain choices are our best defense.

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.