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Avalanche Forecast

Archived

Feb 10th, 2023–Feb 11th, 2023

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

Regions

Tumbler.

Strong to extreme southwest winds will be on a wind slab building mission on Friday. Winds this powerful can build slabs surprisingly low in the terrain. Make observations on the extent of blowing snow and keep avoiding shallow, rocky areas where deep snowpack layers are more easily triggered.

Confidence

Low

Avalanche Summary

No new avalanches have been reported, but field information is very limited in this region.

We suspect users who head to the backcountry will see evidence of a natural wind slab avalanche cycle from recent storm snow and strong southwest winds.

Snowpack Summary

20-25 cm of snow from early this week is being redistributed by increasingly strong southwest winds into lee terrain in wind-exposed areas and at upper elevations. This overlies previous wind slabs and, a melt-freeze crust found on sun-exposed slopes and everywhere below 1600 m.

Several crust/facet/surface hoar layers exist in the upper and middle portions of the snowpack. The most concerning persistent weak layer is at the base of the snowpack from large and weak facets formed in November. This layer is widespread and most likely problematic in steep, rocky alpine terrain.

In general, the snowpack is weak and shallow in this area with an average snowpack depth of 100 cm at treeline.

Weather Summary

Friday night

Cloudy with isolated furries in the early morning. Strong to extreme southwest winds.

Saturday

Mainly cloudy with isolated flurries and trace accumulations. Strong to extreme southwest winds. Treeline high temperatures around -5.

Sunday

Cloudy with isolated flurries and trace accumulations. Strong to extreme southwest winds. Treeline high temperatures around 0 to +1 with freezing levels rising to 1800 metres.

Monday

Mainly cloudy with isolated flurries. Strong southwest winds easing to light west over the day. Treeline high temperatures around -5.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.