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Avalanche Forecast

Archived

Jan 8th, 2021–Jan 9th, 2021

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

Regions

Cariboos.

Keep buried weak layers and potential for persistent slab avalanches in your mind. The likelihood of triggering them may be diminishing but if you're unlucky enough to do so, consequences are high. A complex snowpack like this is best managed with conservative terrain choices.

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Friday night: Mostly cloudy, light southwest wind, freezing level valley bottom.

Saturday: A mix of sun and cloud, moderate south wind, alpine high -8, freezing level valley bottom.

Sunday: A mix of sun and cloud, strong south wind, alpine high -7, freezing level 900 m.

Monday: Flurries, trace, strong south wind, alpine high -6, freezing level 1200 m.

Avalanche Summary

We have had a few recent reports of natural wind slab avalanches, size 2 out of steep alpine terrain on north to east aspects. Wind slabs likely remain triggerable, especially by humans.

Although the persistent slab problem is trending towards being less reactive, the possibility of triggering it remains, and these avalanches would likely be large.

Field observations in this region are limited. If you get out, please consider submitting your observations to the Mountain Information Network. 

Snowpack Summary

20-50 cm of recent fresh snow reportedly sits on a weak layer of surface hoar in many areas. It is suspected that this layer is most prevalent at treeline and below treeline. Recent strong winds have redistributed the storm snow and created wind slabs in lee terrain, especially at higher elevations.

A persistent weak layer is now down about 70-100 cm. The distribution of this layer is variable. In some areas, it's surface hoar and/or a crust. In other areas, this layer may be difficult to find, if it exists at all. This layer has been reported as very prevalent in areas near Valemount.

There is a prominent crust near the base of the snowpack. This crust likely has weak facets above and/or below it. There have been no recent avalanches reported on this layer, but would be most likely to trigger in steep, shallow, rocky terrain, where the snowpack transitions from thin to thick over a short distance.

Terrain and Travel

  • Be especially cautious as you transition into wind affected terrain.
  • Keep your guard up at lower elevations. Wind slab formation has been extensive.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.

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.