Bulletin d’avalanche

Kootenay Boundary

Dec 27 – 28, 2021Avalanche Canada
Voir sur la carte
Archivé · expiré 5 years ago

Danger d’avalanche

Wed
Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
Ouvrir la carte complète

Points saillants

The recent snow may become more reactive to human triggers as it settles into a more cohesive slab. Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches. Use small low consequence slopes to test the bond of the new snow. 

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2–3

    A crust from early December is now 50-120 cm below the surface, and found up to 2300 m. A layer of weak facets (sugary snow) has been reported above and below this crust. Explosives have triggered large (size 2.5) avalanches failing on this layer as recently as Friday, Dec 24. New snow and wind loading, or a heavy trigger such as a skier or snowmobile, may add enough stress to trigger a persistent slab.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2.5

    The recent snow may become more reactive to human triggers as it settles into a more cohesive slab. Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches. 

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

MONDAY NIGHT: Mostly cloudy / Light northwest wind / Low of -21

TUESDAY: Mix of sun and cloud / Moderate northwest wind / High of -17

WEDNESDAY: Sunny / Light northwest wind / High of -18

THURSDAY: Mostly cloudy / Moderate northwest wind / High of -17

Avalanche Summary

Numerous explosive triggered storm slab avalanches up to size 2.5 were reported near Nelson on Sunday.

Numerous skier triggered dry loose avalanches up to size 2 were reported on Sunday. Expect dry loose avalanches (sluffing) running far and fast in steep terrain.

Additionally, an explosive triggered size 2.5 persistent slab at treeline was reported near Rossland on Sunday.

Snowpack Summary

Recent storm totals reached over 100 cm. Expect dry loose avalanches (sluffing) running far and fast in steep terrain. There is a lot of snow available for transport which will form fresh wind slabs when wind speeds increase to moderate.

The recent snow reportedly covered a thin freezing rain crust and a surface hoar interface, which has been responsible for recent storm slab avalanches. For now, we don't expect the new snow to bond well to the old interface. 

A crust from early December is now 50-120 cm below the surface, and is found up to 2300 m. A layer of weak facets (sugary snow) has been reported above and below this crust, and is the layer of concern in our persistent avalanche problem.

The lower snowpack is composed of several early-season crusts. Snow depths at treeline average 150-300 cm.

Terrain and Travel

  • Use small low consequence slopes to test the bond of the new snow.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • If triggered, loose dry avalanches may step down to deeper layers resulting in large avalanches.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.

Régions couvertes