Bollettino valanghe

Purcells

Jan 29 – 30, 2022Avalanche Canada
Vedi sulla mappa
Archiviato · scaduto 5 years ago

Pericolo valanghe

Mon
Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
Apri la mappa completa

In sintesi

It may still be possible to trigger large avalanches on deeply buried weak layers. Be careful with your terrain selection, especially around steep, rocky terrain.

Problemi valanghivi

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely - Possible
    Dimensione
    2.5–3.5

    A concerning weak layer of faceted grains above a melt-freeze crust is around 70 to 150 cm deep. We have been receiving reports of large, destructive avalanches on this layer every few days. We've been reminded multiple times over the last month that this layer could remain a concern all winter. Thin rocky start zones are the most likely place to trigger this layer. Snow loading from new snow and/or wind, daytime warming, cornice falls, and step-downs from smaller avalanches could increase the chance of an avalanche on this layer.

Confidence

High - We have a good understanding of the snowpack structure and confidence in the weather forecast

Weather Forecast

FRIDAY NIGHT: Clear skies with no precipitation, 20 km/h southwest wind, alpine temperature -5 C.

SATURDAY: Clear skies with no precipitation, 20 km/h southwest wind, alpine temperature -7 C.

SUNDAY: Cloudy with snowfall, accumulation 2 to 5 cm, 30 km/h southwest wind, alpine temperature -7 C.

MONDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 40 km/h west wind, alpine temperature -10 C.

Avalanche Summary

No new avalanches were observed on Thursday.

Avalanche activity on the early-December weak layer described in the snowpack summary has been sporadic over the past few weeks. We tend to see reports of avalanches on this layer every few days, being triggered naturally from the weather or occasionally by riders. Most of the avalanches occurred at elevations around 2000 m. Possible natural triggers include daytime warming, warming from the sun, cornice falls, or smaller avalanches stepping down. Human triggering is most likely in steep, rocky slopes with a shallow or thin-to-thick snowpack.

Snowpack Summary

Surface hoar crystals are found in sheltered areas and a melt-freeze crust on solar aspects. These will be important layers to track once buried by new snow. Alpine terrain has variable wind effect. 

Some older thin surface hoar layers are 20-40 cm deep, but have not been producing concerning results in recent snowpack tests. 

The most notable layer of concern in the snowpack is a facet/crust layer that formed in early December and ranges in depth between 70 cm along the shallower eastern Purcells and up to 150 cm in the western Purcells.

Terrain and Travel

  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
  • Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.

Regioni coperte