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Avalanche Forecast

Archived

Jan 27th, 2023–Jan 28th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
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.

There is a lot of uncertainty with the reactivity of deeply buried weak layers. Conditions like this are best managed by sticking to lower-angle terrain away from any overhead hazard.

Confidence

Moderate

Avalanche Summary

On Thursday, wind slab avalanches up to size 2, occurring on all aspects above 2000 m were reported. Explosives triggered a size 3 avalanche on the Deep Persistent facets, and a couple of natural Deep Persistent slab avalanches were reported between 2000-2500 m.

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

Numerous natural and human-triggered wind slabs were also observed on Sunday through Tuesday throughout the region, ranging in size from 1.5-2.5. One of these avalanches in the south of the region resulted in a partial burial. These avalanches mainly occurred on east and northeast aspects in the alpine and treeline.

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

Surface snow varies by elevation with recent warm temperatures turning snow moist up to 1800 m and now heading into a cooling trend. 10-35 cm of recent snow covers a layer of surface hoar and thin crust on steep solar aspects around treeline and higher, and a thick crust up to 1700 m around Revelstoke and increasing to 2000 m travelling south through the region.

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. 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

Friday night

Scattered flurries as cold arctic air moves south. Most areas trace to 5 cm, and isolated areas of the southern Selkirks could see up to 15 cm. Ridge wind north 10-20 km/hr. Alpine temperature -14 C.

Saturday

Layered cloud with sunny breaks. Ridge wind northeast 15-30 km/hr. Alpine temperature -16 C.

Sunday

Sunny. Ridge wind northwest 10-20 km/hr. Alpine temperature -20 C.

Monday

Sunny. Ridge wind northeast 5-15 km/hr. Alpine temperature -20 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.