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Avalanche Forecast

Archived

Jan 23rd, 2023–Jan 24th, 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 avalanches possible, human triggered probable.
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.

Regions

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

Avoid avalanche terrain, dangerous avalanche conditions exist in this region.

A fatal avalanche incident occurred south of Valemont on Saturday.

Confidence

Moderate

Avalanche Summary

On Saturday a serious avalanche Incident occurred, which resulted in a fatality, occurred in the Oasis riding area south of Valemont. The avalanche was on a north-northwest aspect at 2100 m. It was remotely triggered and 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.

Rider triggered avalanches continue to Occur in this region. This MIN describes a close call on Saturday.

Over the past week, there have been numerous reports of large human-triggered avalanches on both a 50 cm deep surface hoar layer in the middle of the snowpack and weak facets at the bottom of the snowpack. See photos of some of these avalanches here and here. A very large deep persistent slab avalanche (size 3) occurred naturally in alpine terrain in the western Cariboos on Jan 18.

All of these very large avalanches occurred at upper treeline/lower alpine. Avalanches like these are most likely to be triggered on steep, shallow and previously undisturbed slopes.

Snowpack Summary

New snow continues to gradually accumulate. Westerly winds will continue to affect exposed terrain and form wind slabs near ridgetops. 20 to 60cm of recent snowfall sits above a layer of surface hoar as well as a sun crust on steep solar aspects. Below 1600 m, recent snow is accumulating above a rain crust.

A prominent layer of buried surface hoar can be found roughly 40 to 80cm deep. It has shown ongoing signs of instability in the Valemount area, and could potentially be problematic throughout the Cariboos and Northern Monashees. The bottom of the snowpack is made up of large weak facets buried in late November, which has caused a deep persistent slab problem across much of interior BC.

Weather Summary

Monday Night

Cloudy with up to 15cm of new snow expected. Strong northwest wind and a low of -7 at 1800m.

Tuesday

Mostly cloudy with up to 10cm of new snow expected. Moderate to strong northwest winds and freezing levels rising to 1200m, high of -3 at 1800m.

Wednesday

A mix of sun and cloud  with flurries bringing a few centimeters of new snow. Strong northwest winds and a high of -4 at 1800m.

Thursday

Cloudy with up to 5cm of new snow expected. Strong northwest winds and freezing levels rising to 1500m.

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.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • 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.