Boletín de aludes

North Columbia

Apr 12 – 13, 2021Avalanche Canada
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Archivado · caducó 5 years ago

Peligro de aludes

Wed
Thu
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Lo esencial

It's going to be a sunny and warm day with freezing levels rising to 1900 m. Cornices are big and fragile and a hazard on their own if they fail. Be alert to changing conditions on sun exposed slopes during the heat of the day, especially if the snow becomes moist or wet.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely - Possible
    Tamaño
    1–1.5

    Lingering pockets of wind slab may be triggerable in unsupported terrain features.

  • Cornices

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible - Likely
    Tamaño
    2–3

    Cornices will become fragile with rising temperatures, especially when the sun is out. Cornice falls are dangerous on their own and they can also trigger slabs on slopes below.

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–1.5

    Surface snow can quickly lose cohesion and become unstable with solar warming during the day. Avoid exposing yourself to terrain where a small wet loose release could have big consequences. 

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

A ridge of high pressure over the province brings sunny, dry weather. Freezing levels are forecast to steadily rise through the week.

Monday night: Clear, moderate easterly wind, alpine low -16 C, freezing level at valley bottom. 

Tuesday: Sunny, light to moderate northeast wind, alpine high +3 C, freezing level 1900 m.

Wednesday: Mostly sunny, moderate to strong northeast wind, alpine high +6 C, freezing level 2600 m.

Thursday: Sunny, moderate east wind, alpine high +8 C, freezing level 2700 m.

Avalanche Summary

Wind slabs have shown quite limited reactivity over the weekend, a few natural and ski cut size 1-1.5 were observed on Saturday. On Friday, most activity in the recent snow has been limited to size 1 loose snow avalanches. One size 2 was reported.

A couple of natural cornice failures size 2.5 observed on Sunday did not trigger slabs on slopes below. 

Neighboring Glacier National Park reported a few very large (size 3-4) glide slab releases on Thursday. Glide slabs are hard to predict and can release at any time so it is important to avoid slopes with glide cracks.

Snowpack Summary

The 20-30 cm of recent snow sits on a series of melt-freeze crusts on all aspects below 1900 m and southerly aspects to mountain top. The recent snow is going through a diurnal cycle becoming moist during the daytime and refreezing overnight. Reports indicate that this snow might not be bonding well to the underlying crust. On North aspects in the alpine, the recent snow sits on dry wintery snow surfaces and possibly surface hoar on wind-sheltered slopes.

The recent warm weather is expected to have helped old persistent weak layers heal, including a few crusts buried over the last month as well as a facet layer 150 cm deep from the mid-February cold snap.

Terrain and Travel

  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Rocks will heat up with daytime warming and may become trigger points for loose wet avalanches
  • Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.

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