Bulletin d’avalanche

North Columbia

Jan 17 – 18, 2023Avalanche Canada
Voir sur la carte
Archivé · expiré 4 years ago

Danger d’avalanche

Thu
Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
Ouvrir la carte complète

Points saillants

Continue to make conservative terrain choices and consider the consequences of an avalanche on a chosen slope. There is variability in the snowpack throughout the region, but what is consistent is that the snowpack is shallower and weaker than average.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1.5–2.5

    As many as five concerning weak layers can be found in the top 150 cm of the snowpack. Recently, the most reactive layers have been a layer of surface hoar buried on Jan 12 and another layer of surface hoar and a crust buried at the start of the month.

    This is a complicated and weak snowpack. Several of these layers are at a prime depth for human triggering. Keep this in mind when deciding what slopes to ride, and always consider the consequences if the slope does avalanche.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2.5–3.5

    A layer of large and weak facets sits near the base of the snowpack. This layer has most recently been problematic in lower alpine elevations.

    Avoid thin and rocky start zones where weak layers sit closer to the surface, riders are most likely to trigger an avalanche on this layer in terrain with shallow or variable snow depths or by first triggering a layer further up in the snowpack.

Confidence

High

Avalanche Summary

A widespread avalanche cycle occurred during the storm on Friday and Saturday, producing large avalanches at all elevations and aspects on multiple persistent weak layers. Most of the activity was on the two surface hoar layers from January, but there was also activity on the November facets near the bottom of the snowpack. Avalanches ranged in size from 1.5 to 3.5.

Human triggered avalanche activity continued on Sunday, with numerous reports of remote, accidental, and controlled avalanches. These avalanches were generally up to size 2 and were triggered on one of the two surface hoar layers buried in January.

Looking forward, there may be a slight decline in the reactivity of these weak layers, but the snowpack is inherently weak and large human triggered avalanches remain likely.

Snowpack Summary

A recent layer of surface hoar and a crust on south facing slopes can be found under 20 to 60 cm of new dense storm snow at treeline and above. Wind slabs exist on north, west, and east facing terrain at treeline and above. A surface crust will form below 1800 m as the freezing level drops.

There are four additional weak layers in the snowpack. The most reactive in recent days have been the layer mentioned above and another surface hoar layer from early January. The bottom of the snowpack is made up of large facets buried in late November. This layer remains a concern.

In general, this year's snowpack is complicated, weak, and shallow. Keep this in mind as you move through the mountains.

Weather Summary

Monday night

Cloudy with flurries bringing trace amounts of snow, 20 km/h southwest wind, freezing level drops to valley bottom with treeline temperatures cooling to -7 °C.

Tuesday

Mostly cloudy with the possibility of light flurries bringing trace amounts of snow, 20 km/h southwest wind, freezing level around 1000 m with treeline temperatures around -5 °C.

Wednesday

Mostly cloudy with light flurries bringing trace amounts of snow, 20 to 40 km/h southwest wind, treeline temperatures around -6 °C.

Thursday

Cloudy with scattered flurries bringing 5 to 10 cm of snow, 40 km/h southwest wind, treeline temperatures around -6 °C.

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.
  • Uncertainty is best managed through conservative terrain choices at this time.

Régions couvertes