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Avalanche Forecast

Archived

Jan 21st, 2023–Jan 22nd, 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 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

North Columbia, South Columbia, Blue River, Clearwater, Premier, Grohman, Clemina, Jordan, North Monashee, North Selkirk, Shuswap, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, North Okanagan, Retallack, Valhalla, Whatshan.

Continue to make conservative terrain choices and consider the consequences of an avalanche on a chosen slope. You may not see signs of instability but the layers are still there. Avoid shallow, steep, rocky slopes.

The likelihood of avalanches will increase on sun exposed slopes.

Confidence

Moderate

Avalanche Summary

On Saturday afternoon we received a report of a serious avalanche accident involving people in the Oasis riding area south of Valemont. This avalanche occurred on a north-northeast aspect at 2100m. It was remotely triggered from 20m away and likely ran on the November facets near the bottom of the snowpack. This very large(size 2.5) avalanche had a depth of 80 to 120cm

A few concerning avalanches occurred on Thursday. The first took place in the far north of the region on a southwest facing alpine slope. It was a natural size 3 running on the November facets.

The second was a size 3.5 vehicle remote in the Central Monashees. This avalanche was remotely triggered by a snow cat traveling across a rocky west facing ridgeline. This avalanche also failed on the November facets. The crown was up to 3.5m deep.

The third was another vehicle remote also running on the November facets. This one was in the Selkirks on a south through west facing piece of terrain.

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

Snowpack Summary

New snow continues to gradually accumulate. Winds have pressed exposed terrain and formed wind slabs near ridge tops. At lower elevations, a rain crust exists down 10 to 40cm , with reported elevations extending up to 2000 m around Nelson, 1700 m around Revelstoke, and 1600 m around Valemount. The snow surface will likely become moist on sun exposed slopes.

Two persistent weak layers in the middle of the snowpack remain reactive to human triggering. They are both surface hoar layers that formed in early January and are typically found 40 to 90 cm deep throughout the region. There are also some deeper facet and surface hoar layers that formed in December, but recent snowpack observations suggest they are strengthening.

The bottom of the snowpack is made up of large weak facets buried in late November, which has caused an atypical deep persistent slab problem for this region.

Weather Summary

Saturday Night

Cloudy with up to 5cm of new snow expected. Moderate westerly winds and a low of -8 at 1800m.

Sunday

A mix of sun and cloud with the possibility of light flurries bringing trace amounts of new snow. Light to moderate northwest winds and a high of -6 at 1800m.

Monday

Cloudy with flurries bringing up to 10cm of new snow. Strong west winds and a high of -8 at 1800m.

Tuesday

Cloudy with up to 10cm of new snow expected. Moderate to strong northwest winds and a high of -5 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.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Avoid being on or under sun exposed slopes.

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.

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.

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.