Lawinenlagebericht

South Rockies

Jan 8 – 9, 2021Avalanche Canada
Auf der Karte ansehen
Archiviert · abgelaufen 6 years ago

Lawinengefahr

Sun
Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
Vollständige Karte öffnen

Kernpunkte

Sporadic large natural persistent slab avalanches have recently been reported in this region. This low likelihood, high consequence scenario is best avoided by choosing conservative terrain away from overhead hazard.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Strong southwest wind and a series of moderate snowfalls over the past few days has likely left wind slabs in steep leeward terrain.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely - Possible
    Größe
    1.5–3

    Triggering large avalanches on weaknesses in the lower snowpack remains a possibility. In some areas the concern is weak snow around crusts 50 to 100 cm deep, while in others it's weak snow near the bottom of the snowpack. This problem is best managed by avoiding steep rocky slopes and approaching avalanche terrain with caution.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–1.5

    Small wet loose avalanches or cornice falls may trigger deeper weak layers, resulting in large avalanches.

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

  

THURSDAY NIGHT: Clear / Light, southwest ridgetop wind / alpine low temperature -14 / Freezing level valley bottom.

FRIDAY: Mix of sun and cloud / Light, southwest ridgetop wind / alpine high temperature -6 / Freezing level valley bottom.

SATURDAY: Sunny / Light, southwest ridgetop wind / alpine high temperature -8 / Freezing level valley bottom.

SUNDAY: Sunny / Moderate, northwest ridgetop wind / alpine high temperature -8 / Freezing level valley bottom.

Avalanche Summary

A large (size three) naturally triggered persistent slab avalanche was reported on a large alpine feature near Crowsnest Pass on Thursday. This avalanche was triggered by either a small wind slab in motion or a cornice fall. This ia an example of the "low probability; high consequence" scenario that persistent slab problems often create.

Explosive avalanche control produced a few size 2-3 wind slab avalanches on Tuesday. Last weekend there were numerous natural size 2-3 slab avalanches. Most of these were storm slab avalanches in alpine terrain, although some of the reports from the upper Elk Valley included avalanches at treeline elevations that likely failed on 60-100 cm deep surface hoar layers.

Snowpack Summary

Moderate snowfalls and strong southwest wind over the past few days has left hard surfaces and wind slabs in exposed terrain. The upper snowpack consists of several layers of old wind slabs, while the lower snowpack consists of decomposing crusts and weak faceted snow. In the Elk Valley a decomposing surface hoar layer can be found around one of these crusts 50-100 cm below the surface. Avalanche activity on these layers in the lower snowpack have been sporadic, mostly occurring during natural avalanche cycles. However, this snowpack structure is always a concern for human triggering on steep rocky slopes with variable snowpack depths.

Terrain and Travel

  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Be aware of the potential for large avalanches due to the presence of buried weak layers.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid areas with overhead hazard.

Abgedeckte Regionen