Avalanche Forecast

Archived

Dec 8th, 2022–Dec 9th, 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.

Conditions are more complicated than what meets the eye. Fresh wind slabs formed at upper elevations. Riders may be drawn to more sheltered areas around treeline to avoid these wind slabs, but should consider that this is where the persistent slab problem has been most problematic to date. Keep your terrain choices conservative and don't let good riding lure you into more hazardous terrain.

Confidence

Moderate

Avalanche Summary

No significant avalanches were reported in the past couple days. Over the weekend Small skier and remotely triggered avalanches were reported. These avalanches were generally at treeline and failed on the mid November surface hoar layer.

Snowpack Summary

New snow and Southwest winds will likely have formed wind slab throughout the day on Thursday. Recent snow has buried a layer of surface Hoar in sheltered terrain and a sun crust on south facing slopes.

A concerning layer of surface hoar from mid November is buried down 40 to 60cm. This layer could become more reactive as slab properties above it increase with new snow and wind.

Snowpack depths average 80-160 cm in the alpine. Below treeline elevations are now above the threshold for avalanches in many areas.

Weather Summary

Thursday Night

5 to 10cm of new snow expected. Moderate southwest winds with a low of -7 at 1500m.

Friday

Mostly cloudy with a trace of new snow expected. moderate southwest winds with a high of -5 at 1500m.

Saturday

Cloudy with up to 10cm of new snow. Moderate southerly winds in the morning becoming light in the afternoon. High of -5 at 1500m.

Sunday

Flurries in the morning bringing 5cm of new snow and then clearing in the afternoon. High of -2 at 1500m. Light winds.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Remote triggering is a concern, watch out for adjacent and overhead slopes.
Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

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.