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Avalanche Forecast

Archived

Dec 24th, 2023–Dec 25th, 2023

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

Regions

North Rockies, Kakwa, McGregor, Pine Pass, Renshaw, Robson.

A persistent weak layer of surface hoar has been reactive to human-triggering in recent days. The safest way to manage this problem is through conservative terrain choices.

Confidence

Moderate

Avalanche Summary

A natural avalanche cycle occurred in the past few days. Several rider triggered slab avalanches have also been reported.

Check out this MIN from Powder King, detailing a skier-triggered persistent slab. This MIN shows several avalanches that occurred in Torpy on Friday. We suspect that these avalanches ran on one of the surface hoar layers in the top meter of the snowpack.

Looking forward to Monday, reactivity is expected to persist with wind and warm temperatures.

Snowpack Summary

Recent storm snow has been redistributed into wind slab near ridge crests by southerly winds. Below treeline a new crust is on or near the surface.

The mid pack contains several layers of note; a layer of surface hoar and a crust down 20 to 30 cm , a significant crust from the early December rain event down around 50 cm and a layer of surface hoar down 60 to 100 cm.

Snowpack depth throughout this region is highly variable and as a result the depths of the above mentioned layers are approximate and could be different than what you find in your riding area.

Weather Summary

Sunday Night

Clear periods with no new snow. South alpine wind, 30 to 60 km/h. Treeline temperature -6°C.

Monday

Cloudy with sunny periods, no new snow. South alpine wind, 30 to 70 km/h. Treeline temperature reach a high of -1 °C.

Tuesday

Cloudy with snowfall, 1 to 10 cm of accumulation. South alpine wind, 40 to 100 km/h. Treeline temperature 0 °C.

Wednesday

Mainly cloudy with isolated flurries. South alpine wind, 30 to 60 km/h. Treeline temperature -1 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Any steep opening in the trees should be treated as suspect right now.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.

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.