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Avalanche Forecast

Archived

Jan 9th, 2021–Jan 10th, 2021

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

Regions

Cariboos.

Watch for wind slabs that may remain sensitive to human triggers and keep in mind the lingering potential for large and destructive persistent slab avalanches. 

Confidence

Moderate - Uncertainty is due to the extreme variability of wind effect on the snowpack. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

Saturday night: Partly cloudy, strong south wind, freezing level valley bottom.

Sunday: Flurries, up to 5 cm, strong southwest wind, alpine high -7, freezing level 1100 m.

Monday: Flurries, up to 5 cm, strong southwest wind, alpine high -6, freezing level 1200 m.

Tuesday: Snow, 5-10 cm, strong southwest wind, alpine high -5, freezing level 1200 m.

Avalanche Summary

We have had a few recent reports of natural wind slab avalanches size 1-2 out of steep alpine terrain on north to east aspects. Wind slabs likely remain triggerable under human loads.

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

Severely wind affected surfaces can be found at upper elevation and in northern parts of the region, all the way down to treeline. 20-50 cm of snow sits on a spotty weak layer of surface hoar in many areas treeline and below. Rising freezing levels may promote slab development in the overlying snow, activating this weak layer on Sunday.

A persistent weak layer is now buried 70-100 cm below the surface. The distribution of this layer is variable and it can present as surface hoar and/or a crust. It has been reported as most 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 careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.