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Avalanche Forecast

Archived

Feb 8th, 2023–Feb 9th, 2023

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

Regions

Tumbler.

Evaluate snow conditions as you transition into open terrain features, and be on the lookout for signs of instability like shooting cracks. Stiff, wind deposited snow can be expected to avalanche under the weight of a rider.

Avoid shallow, rocky snowpack areas where triggering the deep persistent weak layer is still possible

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 cm of storm snow in the alpine is being redistributed by southwesterly winds into wind slabs in lees. The recent storm snow sits on previously wind-affected surfaces. Below this, a melt-freeze crust is 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

Wednesday Night

Partly cloudy. Ridge wind southwest 40-50 km/h. Alpine temperatures -10 C. Freezing level valley bottom.

Thursday

Mix of sun and clouds. Moderate ridge wind from the southwest picks up to 50-70 km/h in the evening. Alpine temperatures rise to -2 C. Freezing level rise to 1400m.

Friday

Mainly cloudy with sunny periods and isolated flurries, trace accumulation. Moderate ridge wind from the southwest picks up to 50-70 km/h in the evening. Alpine temperatures rise to -3 C. Freezing level 1300m.

Saturday

Mainly sunny with cloudy periods and isolated flurries, trace accumulation. Moderate ridge wind from the southwest picks up to 50-70 km/h in the evening. Alpine temperatures rise to -4 C. Freezing level 1000m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for areas of hard wind slab on alpine features.
  • Use ridges or ribs to avoid areas of wind loaded snow.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • 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.