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 avalanches possible, human triggered probable.

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 Saturday several natural wind slabs, persistent slabs and deep persistent slabs up to size 3.5 were observed. These avalanches occurred late Friday through early Saturday morning and were triggered by wind loading or cornice falls in most cases.

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 of recent snowfall over the last week has covered a layer of surface hoar and thin crust on solar aspects at treeline and above, 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 into wind slabs on south and east slopes.

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

Sunday Night

Clear skies with no new snow expected. Strong north to northwest winds and a low of -23 at 1800m.

Monday

Increasing cloud with up to 5cm of new snow expected. Moderate to strong northwest winds and a high of -13 at 1800m, possible temperature inversion with colder temps lower in valleys.

Tuesday

Stormy with 5 to 15cm of new snow expected. Moderate to strong west winds with a high of -12 at 1800m.

Wednesday

Stormy with up to 20cm of new snow expected. Moderate southwest winds and a high of -10 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.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

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.

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.