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Avalanche Forecast

Archived

Jan 29th, 2023–Jan 30th, 2023

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

Regions

Cariboos, North Rockies, Blue River, Clearwater, McBride, Premier, Quesnel, Sugarbowl, Clemina, North Monashee, McGregor, Renshaw, Robson.

This challenging snowpack continues to produce avalanches. Stick to low-angle terrain away from any overhead hazard.

Read more in the latest Forecaster Blog.

Confidence

Moderate

Avalanche Summary

Both natural and human-triggered persistent and deep persistent slab avalanches continue to be reported daily.

On Saturday skiers remotely triggered a size 2 wind slab sitting over surface hoar from early January. This avalanche occurred on a northeast aspect at treeline. A size 3 natural deep persistent slab avalanche also occurred earlier in the day on a southerly aspect in the alpine. This min discusses more human triggered avalanches in the region.

On Friday east of Prince George, skiers triggered a size 2 deep persistent avalanche on a northeast slope at 1700m, the avalanche was triggered from the shallowest portion of the feature and the crown depth varied from 30 cm to 1 m. Additionally, two very large (size 2.5-3) natural wind slabs were reported on northeast-east and southeast aspects around 1900 m.

On Thursday a few very large (size 2.5-3) natural wind slab avalanches were reported around 1800-2000 m. Additional ongoing evidence of weak basal facets continued with a size 3 deep persistent avalanche reported on a steep southeast slope at 2400 m.

On Monday, a fatal skier-triggered avalanche incident occurred in the Selkirk range near Revelstoke. The avalanche occurred on an east aspect at 1900 m, on a steep, open and unsupported slope. The size 2 avalanche had a crown depth of 50 cm and failed on surface hoar buried in early January.

Snowpack Summary

20-40 cm recent snowfall covered a layer of surface hoar and thin crust on solar aspects at treeline and higher, and a supportive crust up to 1800 m. North and westerly winds have redistributed loose snow to lee terrain.

A prominent layer of buried surface hoar can be found roughly 40-70 cm deep. It is found in some places but not in others, and has been recently reactive to human triggering.

The bottom of the snowpack is made up of large weak facets buried in late November, causing the Deep Persistent Slab problem for this region.

Weather Summary

Sunday Night

Increasing cloud with no new snow expected. Strong north to northwest winds and a low of -25 at 1800m.

Monday

Mostly cloudy with around 5cm of new snow expected. Strong northwest winds and a high of -15 at 1800m, possible temperature inversion with colder temps lower in valleys.

Tuesday

Stormy with 5 to 15cm of new snow expected. Light to moderate west winds with a high of -9 at 1800m.

Wednesday

Stormy with up to 20cm of new snow expected. Moderate west winds and a high of -6 at 1800m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be mindful that deep instabilities are still present and have produced recent large avalanches.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Approach lee and cross-loaded slopes with caution.

Problems

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.

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.