Bulletin d’avalanche

Lizard-Flathead

Dec 11 – 12, 2019Avalanche Canada
Voir sur la carte
Archivé · expiré 7 years ago

Danger d’avalanche

Fri
Sat
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
Ouvrir la carte complète

Points saillants

Resist the temptation to travel into steep or complex terrain, triggering large avalanches on buried weak layers is a concern right now.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Steady wind from the west is likely forming fresh wind slabs in the alpine and near ridgetops.

  • Persistent Slabs

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

    There is uncertainty about how easy (or difficult) it could be to trigger a large avalanche on one of the crusts and weak layers in the lower snowpack. Choosing conservative terrain is the best way to manage this uncertainty.

Confidence

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

Weather Forecast

TUESDAY NIGHT: Cloudy with some isolated flurries, 40 km/h wind from the southwest, alpine temperatures drop to -8 C.

WEDNESDAY: Cloudy with isolated flurries and up to 5 cm of new snow, 40 km/h wind from the west, alpine high temperatures around -5 C.

THURSDAY: 5-10 cm of new snow, 50 km/h wind from the west, alpine high temperatures around -2 C.

FRIDAY: Mostly cloudy, 30 km/h wind from the west, alpine high temperatures around -2 C.

Avalanche Summary

Numerous recent storm slab and persistent slab avalanches have been reported. Explosive control in the Lizard Range over the weekend produced large slab avalanches (size 2-3) at treeline and alpine elevations. The avalanches ran on the both the November and October crust layers 40-100 cm deep. Evidence of natural avalanches with wide propagation have also been reported from the Flathead area.

Fewer avalanches have been reported since the weekend, but the potential for triggering large persistent slab avalanches remains a concern.

Snowpack Summary

30-40 cm of snow from the weekend has been redistributed by the wind to form wind slabs in the alpine and near ridgetops at treeline. Crust layers from November and October can be found 40-100 cm below the surface and have recently produced large avalanches with explosive triggers. While these layers are likely widespread across the terrain, we are uncertain about whether they could also be triggered by humans. Snowpack depths range between 50-100 cm at higher elevations and taper rapidly below treeline.

Régions couvertes