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Avalanche Forecast

Archived

Dec 3rd, 2022–Dec 4th, 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, human triggered possible.
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.

A reactive layer of surface hoar continues to be a concern. Choose conservative terrain and consider that hazard may be most tricky at treeline elevations.

Watch for signs of instability like recent avalanches, whumpfing or shooting cracks.

Confidence

Moderate

Avalanche Summary

A layer of surface hoar from mid November buried 60-80 cm deep continues to be reactive. Widespread whumpfing and cracking were reported on Wednesday and Thursday. On Friday a remotely triggered natural avalanche was reported on a steep east facing feature near Kootenay Pass, likely failing on this layer. Read the MIN report here. On Thursday, evidence of a natural cycle was observed to size 2 on north facing terrain features around 2000 m.

Several other MIN reports from across the forecast region indicate the sensitivity of these layers, showcasing touchy cut banks (MIN1), whumpfing and shooting cracks (MIN2), and reactive snowpack tests (MIN3).

Snowpack Summary

Upwards of 40 cm accumulated around the region over the last few days. This covers a layer of small surface hoar now buried 30-50 cm. Another weak interface is buried 60-90 cm deep from mid November - consisting of sugary faceted grains, large surface hoar crystals in sheltered terrain features, and a crust on steep sun-exposed slopes. Reports of whumpfing, cracking, and recent avalanches suggest this interface is not bonding well.

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 below treeline elevations are now above threshold in many areas.

Weather Summary

Saturday Night

Mostly clear skies with light westerly winds. No snowfall expected.

Sunday

Mostly clear skies with light and variable winds. Alpine high of -10. Isolated flurries possible late afternoon.

Monday

A mix of sun and cloud, increasing westerly winds over the day to strong or extreme northwesterlies. Alpine high of -9. Flurries bring trace amounts of snow.

Tuesday

Mostly cloudy with strong to extreme northwest winds around ridgelines. Alpine high of -12. Flurries bring trace amounts of snow.

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.