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Avalanche Forecast

Archived

Jan 28th, 2023–Jan 29th, 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 unlikely, human triggered possible.
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, human triggered possible.

Regions

North Columbia, South Columbia, Grohman, Esplanade, Jordan, North Selkirk, Shuswap, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, North Okanagan, Retallack, Valhalla, Whatshan.

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

On Friday, size 1-2 wind slab avalanches were triggered by riders and failed naturally, these were reported on northeast-east aspects above 2000 m. Riders also triggered a few persistent slab avalanches size 1-2, with crowns 50 cm deep and failing on surface hoar.

On Thursday, wind slab avalanches up to size 2 were reported occurring on all aspects above 2000 m. Basal facets continued to demonstrate reactivity with two large (size 2) natural deep persistent avalanches reported and explosives triggering a size 3 deep persistent avalanche, all occurring between 2000-2500 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.

High-consequence avalanche activity has been ongoing for several weeks. Your best defence is to stay diligent in choosing low-consequence terrain. Stick to slopes that have been heavily trafficked throughout the winter and avoid venturing into untouched zones. Stay disciplined and adjust your expectation for this winter.

Snowpack Summary

15-40 cm recent snowfall over the last week and covered a layer of surface hoar and thin crust on solar aspects at treeline and higher, and a supportive crust up to 1700 m around Revelstoke and increasing to 2000 m travelling south through the region. North and westerly winds have redistributed loose snow to lee terrain.

Two layers of surface hoar which formed in early January are found 40-90 cm deep. These persistent weak layers have recently been reactive to human triggering, but snowpack tests are starting to indicate less propagation propensity. Deeper in the snowpack are two surface hoar/facet layers that were active earlier in the season, but recent snowpack observations suggest they are strengthening. 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

Saturday night

Clear and with gusty ridgetop winds. Ridge wind northwest 20-40 km/hr. Alpine temperature -24 C.

Sunday

Sunny in the morning with increasing clouds throughout the day. Ridge wind northwest 10-20 km/hr. Alpine temperature -22 C.

Monday

Sun and increasing cloud. Ridge wind southwest 15-30 km/hr. Alpine temperature rising to -16 C.

Tuesday

Flurries, 5-10 cm. Increasing southwest ridge wind 30-40 km/hr. Alpine temperatures rising to -12 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be mindful that deep instabilities are still present and have produced recent large avalanches.
  • Approach lee and cross-loaded slopes with caution.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.

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.