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Avalanche Forecast

Archived

Jan 6th, 2023–Jan 7th, 2023

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

West Island.

Heavy snowfall and extreme wind are creating very dangerous avalanche conditions at treeline and alpine elevations.

A persistent slab problem lurks at a prime depth for human triggering as well as large, consequential avalanches. Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.

Confidence

Moderate

Avalanche Summary

No significant avalanche activity has been reported this week.

On Friday and looking forward to Saturday, we expect natural avalanches to occur during periods of intense precipitation and wind-loading.

Snowpack Summary

Heavy snowfall accumulation has occurred above 1000 m in the past few days. Rain will soak the snowpack at lower elevations. Avalanches during this period could run on a crust layer that is now buried 60 to 100 cm deep. Snowpack depths at treeline are roughly 100 cm, while most below treeline terrain is below the threshold depth for avalanches, except for isolated smooth features.

Weather Summary

Friday night

Cloudy with precipitation, 30-50 mm. Snowline 600 to 900 m. Southerly winds 60-120 km/h at ridgetop, treeline temperatures around 0 C.

Saturday

Precipitation easing, 10-20 mm mainly in the morning. Snowline around 700m. Southerly winds 40-60 km/h at ridgetop easing into the afternoon, treeline temperatures rise to 1 C.

Sunday

Cloudy with precipitation, 10-20 mm. , snowline around 700 m. Southerly winds increase 60-100 km/h at ridgetop. Treeline temperatures around 0 C.

Monday

Cloudy with precipitation, up to 4mm. Snowline around 600 m. 60-90 km/h southeasterly winds at ridgetop. Treeline temperatures are around -1 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Keep in mind the crust offers an excellent bed surface for avalanches.

Problems

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.

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.