Avalanche Forecast

Archived

Jan 30th, 2023–Jan 31st, 2023

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

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

6:15 AM Update: A natural avalanche cycle is expected. Travel in avalanche terrain is not recommended.

Confidence

Moderate

Avalanche Summary

On Sunday, several large to very large (size 3 to 4) avalanches were triggered naturally on the basal facets. The avalanches were on all aspects and generally in alpine terrain between 2400 and 2900 m. See here for a video of a rider-triggered avalanche near Renshaw and another example here near Clearwater. Numerous shallower wind slabs were also triggered in alpine terrain.

These avalanches are similar to what we've seen over the past week, with persistent and deep persistent avalanches releasing on all the weak layers described in the Snowpack Summary. Most avalanches over the past week were large to very large (size 2 to 4), occurring between 1700 and 2400 m and on all aspects. See this MIN for a recent example and see here for information on a fatal skier-triggered avalanche incident from last week near Revelstoke.

See more on the potential of triggering deeper weak layers Forecasters' Blog.

Snowpack Summary

New snow and strong westerly wind will form new wind slabs in lee terrain features. They will overly previously wind-affected snow from recent northeast wind. Storm slabs may begin to form in wind-sheltered terrain.

Two layers of surface hoar crystals and/or a melt-freeze crust may be found around 30 to 80 cm deep. Surface hoar is most likely found in wind-sheltered terrain around treeline and lower alpine elevations. The melt-freeze crust is found up to 1800 m on all aspects and into the alpine on sun-exposed slopes.

Large and weak facets from November are near the base of the snowpack, which continue to produce very large avalanches in the region.

Weather Summary

Monday Night

Cloudy with snowfall, accumulation 5 to 15 cm with local enhancements possible, 20 to 30 km/h west wind, treeline temperature -12 °C.

Tuesday

Cloudy with snowfall, accumulation 5 to 15 cm with local enhancements possible, 20 to 40 km/h west wind, treeline temperature -12 °C.

Wednesday

Cloudy with snowfall, accumulation 10 to 20 cm with local enhancements possible, 20 to 40 km/h southwest wind, treeline temperature -10 °C.

Thursday

Cloudy with snowfall, accumulation 5 to 10 cm, 30 to 40 km/h southwest wind, treeline temperature -6 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Travel in alpine terrain is not recommended.
Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
Wind slabs are most reactive during their formation.
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.

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.

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.