Bollettino valanghe

Lizard-Flathead

Jan 1, 2017Avalanche Canada
Vedi sulla mappa
Archiviato · scaduto 10 years ago

Pericolo valanghe

Sun
Mon
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
Apri la mappa completa

In sintesi

On Saturday a large avalanche was skier-triggered on Mt Fernie. Nobody was hurt, but it demonstrates the potentially touchy conditions in wind-affected terrain.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely - Very Likely
    Dimensione
    1–3
    Strong southwest winds are reported to have formed new wind slabs on Friday night and Saturday. New snow and extreme northeasterly winds forecast for Sunday will reverse load many slopes adding to the complexity of the wind slab problem.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely - Possible
    Dimensione
    1–3
    A few large persistent slab avalanches were recently noted in the Corbin area, although I'm unsure of how far-reaching this problem is in the region. I'd carefully test for weak layers before committing to any steep slopes.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

Saturday night: 5-15cm of new snow / Variable winds / Alpine temperature of -13Sunday: Overcast skies with light flurries / Extreme northeast winds / Alpine temperatures of -20Monday: Mix of sun and cloud / Extreme northeast winds / Alpine temperatures of -22Tuesday: Mix of sun and cloud / Light north winds / Alpine temperatures of -20

Avalanche Summary

On Saturday, a size 2.5 slab avalanche was skier-triggered on an east facing slope on Mt Fernie. The slab failed on a cross-loaded treeline feature and ran full path. Although the exact failure plane is unknown, it points to the potentially touchy conditions on wind-affected features. A few days ago, a large (size 2) human-triggered avalanche was reported near Corbin in the Flathead Range in an area where wind had firmed up the surface snow and where sugary facets were present lower down in the snowpack. Evidence of a natural size 2.5 persistent slab avalanche was also noted on a treeline feature in the same area. When the wind picks up again on Sunday, new accumulations from Saturday night will get shifted into lee and cross-loaded features and we can expect an increase in wind slab avalanche activity.

Snowpack Summary

On Saturday night 5 to 15cm of new snow is expected to fall. On Sunday, northerly winds are expected to howl and the new snow is expected to get shifted into new wind slabs. The new snow will overlie about 50cm of storm snow from last week which sits above old hard wind slabs and spotty surface hoar. The cold weather in early December left several layers of weak surface hoar and facets which are now buried 60-80 cm deep. These layers may be more in reactive in areas where the overlying slab has gained cohesion with wind or settlement. A thick crust rain crust from mid-November is near the bottom of the snowpack and remains well bonded to the surrounding snow.

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