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Avalanche Forecast

Archived

Dec 2nd, 2022–Dec 3rd, 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 possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Kootenay Boundary, Bonnington, Grohman, Kootenay Pass, Norns, Rossland, Ymir, Moyie, St. Mary.

Spooky-Moderate Avalanche Hazard: A reactive layer of surface hoar below the fresh snow is primed for human triggering. Choose conservative terrain and consider that hazard may be most tricky at treeline elevations.

Confidence

Low

Avalanche Summary

A layer of surface hoar below the fresh snow continues to demonstrate reactivity. Widespread whumpfing and cracking were reported on both Wednesday and Thursday. And on Thursday, evidence of a natural size 2 avalanche was observed on a north aspect at 2000 m.

A collection of MINs across the forecast region capture the snowpack well: touchy cut banks (MIN1), whumpfing and shooting cracks (MIN2), and reactive snowpack tests (MIN3). The interface of note in these reports is a layer of surface hoar down 20-40 cm, however, MIN3 also found another reactive layer of surface hoar down 75 cm. For now, we lack field observations to determine the distribution of this lower layer, but it is something we will be tracking.

Snowpack Summary

Upwards of 40 cm accumulated around the region over the last few days. This covers a reactive layer of surface hoar now down 30-50 cm. Reports of whumpfing, cracking, and recent avalanches suggest this new snow is not bonding well.

At treeline and above around 50-70 cm of snow overlies a weak layer from mid-November consisting of sugary faceted grains, weak surface hoar crystals in sheltered terrain features, and a hard crust on steep sun-exposed slopes. We have limited information at this point in the season, we're hoping to gain more information on the distribution and sensitivity of these deeper layers as we collect more field observations.

Snowpack depths exceed 160 cm at upper elevations and the latest flurries have covered surface roughness and extended rideable snow into lower elevations.

Weather Summary

Friday night

Cloudy with light flurries, trace to 5 cm overnight. Increasing southwest wind 10-20 km/hr. Treeline temperature low -15 °C.

Saturday

Partly cloudy with sunny breaks in the afternoon. Southwest wind 10-20 km/hr decreasing through the day. Treeline high temperature -8 °C.

Sunday

Clear, cold, and calm. Light northeast wind, treeline high temperatures -8 °C.

Monday

Cold with incoming cloud and wind. Southwest wind increasing to strong. Treeline temperatures -12 °C, wind chill temperatures lower.

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.
  • Remote triggering is a concern, watch out for adjacent and overhead slopes.
  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.

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.