Boletín de aludes

North Rockies

Feb 7 – 8, 2022Avalanche Canada
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Archivado · caducó 5 years ago

Peligro de aludes

Wed
Thu
Alta montaña
4 · Fuerte
Límite del bosque
4 · Fuerte
Bajo el límite
4 · Fuerte
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Lo esencial

New snow will form fresh slabs and increase the likelihood for riders to trigger the buried weak layer. Uncertainty with this layer is best managed with conservative choices. The hazard rating is a step less in the south and east of the region where less snow is expected. 

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely - Very Likely
    Tamaño
    1.5–2.5

    The new snow will add to the recent snow that loaded a weak layer of surface hoar crystals, which is at a prime depth for human triggering. The layer is most prominent in areas sheltered from the wind at and below treeline. Example terrain features to particularly treat as suspect include the lee side of ridges, openings in trees, cut blocks, and burns. Large, wide-propagating avalanches could result where this layer is present. 

    The buried weak layer was reported to be present from the Torpy Sande and Pine Pass areas up to treeline and can generally be expected up to treeline in the northern part of the region.

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely - Very Likely
    Tamaño
    1–2

    20 to 40 cm of new snow is forecast for the west and south of the region. Wind slabs will be found in lee terrain features at higher elevations from strong south and west wind. Storm slabs will be found in sheltered terrain. 

Confidence

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

Weather Forecast

SUNDAY NIGHT: Mostly cloudy with snowfall, 10 to 20 cm new snow in the west of the region, less snow in the south and a trace in the east of the region, strong south wind, alpine temperature -1 C, freezing level 1500 m in the very north of the region and around 2000 m dropping slowly to 1500 m in the rest of the region.

MONDAY: Cloudy with snowfall, 10 to 20 cm in the south and west of the region, a trace of new snow in the east of the region, strong west wind, alpine temperature -2 C, freezing level 1400 m.

TUESDAY: Mostly cloudy, 5 to 10 cm new snow, moderate southwest wind, alpine temperature -3 C, freezing level 1500 m.

WEDNESDAY: Cloudy with snowfall, 10 to 15 cm new snow, moderate to strong southwest wind, alpine temperature 0 C, freezing level rising to 2000 m.

Avalanche Summary

On Saturday, several storm and wind slab avalanches up to size 2 were observed at treeline and in the alpine. Most of these avalanches released naturally, and two were likely triggered by riders.

On Friday a natural avalanche cycle was reported with small storm slab avalanches up to size 1.5. Most avalanches were observed at and below treeline. A couple large (size 2) slab avalanches were reported at treeline on a southwest and an east aspect. Observations on Friday were limited due to visibility.

Large avalanches are expected in areas where the buried surface hoar described in the Snowpack Summary exists. 

Looking towards Monday, avoidance of consequential avalanche terrain is your best bet for having a safe day. Storm and wind slabs will be very touchy due to all the recent snow and wind. The snow will need time to stabilize.

Snowpack Summary

20 to 40 cm are forecast in the west and the south of the region with only up to 5 cm accumulation in the east. The new snow will likely form storm slabs in sheltered areas and wind slabs in lee terrain features from strong south and west wind. This new snow adds to the previous storm which brought 40 to 60 cm for much of the region, with the most in the southwest of the region and the least to the east of the divide and in the north. 

The snow will be particularly touchy where it sits on a weak layer of surface hoar crystals. Reports suggest that the surface hoar is likely most prominent in sheltered openings at and below treeline but could extend into wind-sheltered terrain in the alpine. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns.

The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Uncertainty is best managed through conservative terrain choices at this time.

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