Avalanche Forecast

Archived

Jan 22nd, 2023–Jan 23rd, 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 and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

McBride, Renshaw, Robson.

This is a good time to take a big step back from avalanche terrain. New snow and wind are adding load to a weak and volatile snowpack. It's uncertain when the tipping point will be reached for large, destructive avalanches to occur and this uncertainty demands a conservative approach and low-consequence terrain selection.

Confidence

Low

Avalanche Summary

On Saturday In the neighbouring region to the south, a serious avalanche, presumed to have resulted in a fatality, occurred in the Oasis riding area south of Valemont. The avalanche was on a north-northeast aspect at 2100 m. It was remotely triggered and likely ran on the November facets near the bottom of the snowpack. This large avalanche (size 2.5) had a depth of 80 to 120 cm. There were several other reports of human-triggered avalanches from nearby areas.

Looking forward to this week, reactive storm slabs are expected to form but concern for large natural and human-triggered avalanches is at the forefront of our minds. A series of incoming storms are adding load to shallow, weak snowpack with multiple layers of concern. It is uncertain when the "tipping point" for large destructive avalanches will be reached, but this uncertainty demands conservative and low-consequence terrain selection.

Snowpack Summary

Overnight snowfall will continue throughout the day bringing 10-25 cm of new snow. The accompanying northwest winds will affect wind-exposed terrain and build fresh wind slabs in lee terrain features. Below the new snow, a sun crust may be found on steep solar aspects.

Snowpack depths are shallower than normal, and several buried weak layers have been a concern over the past few weeks. One is a recently buried surface hoar layer found 30 to 60cm deep in sheltered terrain features at treeline and above. At this same depth, a crust exists on steep south-facing slopes. Another layer of facets, crust, and surface hoar was buried around Christmas and is now 50 to 90cm deep. Finally, a layer of large, weak facets buried in November is found near the bottom of the snowpack. This layer is likely most problematic in alpine terrain, where shallower avalanches could scrub down to these basal facets.

Weather Summary

Sunday night

Cloudy with increasing snowfall, 5-15 cm of accumulation. Alpine temperatures drop to a low of -10 C. Ridge wind northwest 40-60 km/h. Freezing level at valley bottom.

Monday

Mainly cloudy with continued snowfall, 5-15 cm of accumulation. Alpine temperatures rise to -7 C. Ridge wind northwest 45-70 km/h. Freezing level rises to 1100 m.

Tuesday

Cloudy with snowfall, 5-10 cm accumulation. Alpine temperatures reach a high of -6 C. Ridge wind northwest 40-60 km/h. Freezing level rises to 1100 m.

Wednesday

Mainly cloudy with snowfall, 5-15 cm of accumulation. Alpine temperatures reach a high of -1 C. Mostly light westerly ridge wind occasionally gusting to 35 km/h. Fre

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Uncertainty is best managed through conservative terrain choices at this time.
Be mindful that deep instabilities are still present and have produced recent large avalanches.
Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.