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Avalanche Forecast

Archived

Dec 31st, 2021–Jan 1st, 2022

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

Regions

North Columbia.

 Keep an eye on the wind. Avalanche hazard will likely increase throughout the day as the strong winds build small but reactive slabs. 

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Friday night: light northwest winds in the alpine with no new snow expected. low of -30 at 1500m.

SATURDAY: strong southwest winds with around 10cm of new snow expected. High of -18 at 1500m.

SUNDAY: strong southwest winds in the alpine with up to 10cm of new snow expected. High of -12 at 1500m.

Monday: light snow all day with light to moderate southwest winds in the alpine. High of -9 at 1500m.

Avalanche Summary

A few wind slabs up to size 2 were observed on northerly and southerly aspects at the treeline elevation. Several natural cornice failures were also observed on all aspects.

The latest avalanche activity on the early-December weak layer described in the snowpack summary was from Monday. This included two natural avalanches and one triggered by a rider. They were large (size 2 to 3), observed on all aspects, and found between 1700 m and up to 2600 m.

Snowpack Summary

New wind slabs will form on Saturday on east and north aspects. These new slabs will likely be limited in size but reactive to rider traffic as a result of the faceted and wind effected surfaces they will form above.

A weak layer of feathery surface hoar may be found around 30 to 50 cm deep. It is most likely found in sheltered terrain features in the lower alpine and treeline, or open features below treeline (e.g., cut blocks). Although avalanche activity hasn't been prominent on this layer, it has been reactive in snowpack tests.

Sugary faceted grains may be found around the early-December melt-freeze crust 80 to 150 cm deep. The layer is most prevalent around 1700 m to 2200 m but could exist at lower and higher elevations for sections of the region. This layer is spatially variable, with many areas showing good bonding to the crust whereas other areas showing concern. This layer has recently been most reactive where it remains shallower than about 100 cm.

Terrain and Travel

  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.

Problems

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.

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.