Boletín de aludes

Purcells

Jan 9 – 10, 2022Avalanche Canada
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Archivado · caducó 5 years ago

Peligro de aludes

Tue
Wed
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Lo esencial

Steady winds will impact loose snow. Be especially mindful around steep, convex openings in the trees and ridge features in the alpine. 

Problemas de aludes

  • Wind Slabs

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

    Southeasterly wind during the most recent storm produced deeper and more reactive deposits in lee features. Steady southwesterly winds will continue to impact snow. Be especially mindful around steep and convex openings in the trees and ridge features in the alpine. The new and recent snow may overlie a weak interface which could result in deeper and touchier than expected slabs.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely - Possible
    Tamaño
    2–3.5

    A persistent slab problem formed by a crust down 70-150 cm has created a low likelihood, high consequence scenario that is difficult to forecast. Avoid likely trigger spots such as steep, rocky slopes with a shallow or thin-to-thick snowpack. Smaller storm slabs or wind slabs have the potential to step down to a deeper weak layer. 

Confidence

Moderate -

Weather Forecast

Saturday night: Mostly cloudy with isolated flurries, up to 5 cm. Moderate to strong SW wind. Treeline low around -8 °C. 

Sunday: A mix of sun and cloud. Moderate SW wind. Treeline high around -5 °C.

Monday: Sunny. Moderate SW wind switching NW. Treeline high around -3 °C.

Tuesday: Sunny. Moderate WSW wind gusting to extreme. Treeline high around -4 °C

Avalanche Summary

On Friday, explosives triggered storm stab avalanches to size 2, on average 20 cm deep. Skiers triggered numerous small (size 1) avalanches. A natural avalanche cycle to size 1.5 occurred Thurs-Fri night with rapid loading of new snow.

On Wednesday, evidence of a natural storm slab avalanche cycle size 1-2 was observed, likely having run during the storm earlier in the week. Wind slabs continued to be reactive near Invermere into Tuesday, up to size 2. By Wednesday, avalanche activity was predominantly loose dry entraining mass to size 1.5-2.

On Tuesday just east of the region in the Rockies near Invermere, a size 3.5 (very large) persistent slab avalanche was triggered remotely by a skier on an alpine ridgetop. The resulting crown was 2-3 m deep and the avalanche ran about 1 km to the valley bottom. More details in this MIN report. This and other notable persistent slab avalanches in neighboring regions feature in our latest blog, Photos of recent persistent slab avalanches in the southern interior.

Snowpack Summary

25-50 cm of new snow accumulated by the end of Friday, accompanied by southwesterly wind and warming temperatures. In open terrain and upper elevations, wind developed more reactive deposits around lee and convex features. An accumulated total of 30-70 cm of new and recent snow now sits over variable and potentially weak snow surfaces including widespread facets, wind affected snow, and/or surface hoar up to 3 mm in sheltered areas.

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 70-150 cm. Activity on this layer has been sporadic. It has generally been triggered on steep, rocky slopes, with a shallow or thin-to-thick snowpack. This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.

Terrain and Travel

  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • Avoid freshly wind loaded terrain features.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.

Regiones cubiertas