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Avalanche Forecast

Archived

Dec 14th, 2022–Dec 15th, 2022

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

Regions

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

We now have two concerning persistent weak layers within our snowpack.

Be aware that if triggered, avalanches may step down to deeper layers resulting in large, destructive avalanches. Keep your terrain choices conservative and be prepared to back off quickly if you find signs of instability like whumpfing and shooting cracks.

Confidence

Moderate

Avalanche Summary

On Tuesday, explosives control in the Monashees produced a few avalanches below treeline up to size 2.

On Monday, several, size 2.5 natural persistent slab avalanches were observed in the Kaslo region. Explosives control throughout the Selkirks triggered size 2.5 avalanches on the mid-November weak layer.

On Sunday, numerous surprise human-triggered avalanches were reported on the persistent weak layer between 2200 and 1700 m. The spookiest reports on this layer are of a skier remote avalanche, size 3, at Kokanee Glacier and a skier sympathetic avalanche, size 2.5 in the Kaslo region. These avalanches either failed on the November weak layers or 'stepped down' from a smaller avalanches onto these deeper instabilities.

Snowpack Summary

Snowpack depths average 80-160 cm in the alpine.

Surface: 5 - 10mm surface hoar has formed on the surface of the snowpack. A sun crust is found on steep solar slopes. Previous southerly winds have created wind slabs in exposed lees and cross-loaded features at higher elevations.

Upper-pack: A 30 - 40 cm soft slab overlies a small layer of surface hoar in sheltered and shaded terrain and a sun crust on sunny south-facing slopes.

Mid-pack: A weak layer of large surface hoar crystals, facets and a melt-freeze crust sits 50-80 cm deep, buried in mid-November. This layer has been very reactive at treeline between 1700-2200 m, on all aspects producing large remotely triggered avalanches. This layer will likely continue to be reactive through the week as northerly winds build wind slabs adding additional load to the weak layer.

Lower-pack: Below the mid-November layer is a generally weak, faceted snowpack.

Weather Summary

Wednesday Night

Partly cloudy skies. Northerly ridge wind 20 - 30 km/hr. Alpine temperatures, high of -10. Freezing levels valley bottom.

Thursday

Scattered clouds. Northerly ridge winds 20 km/h gusting to 40 km/hr. Alpine temperatures, high of -7. Freezing levels 600 m.

Friday

Partly cloudy skies. Northwesterly ridge winds 30 km/h gusting to 50 km/h. Alpine temperatures, high of -9. Freezing levels valley bottom.

Saturday

Cloudy skies. Light flurries, 2 cm accumulation. Northeasterly ridge winds 20 km/h.  Alpine temperatures, high of -9. Freezing levels valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
  • Don't let the desire for deep powder pull you into high consequence terrain.
  • Minimize exposure during periods of heavy loading from new snow and wind.

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.