Lawinenlagebericht

South Rockies

Feb 8 – 9, 2022Avalanche Canada
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Lawinengefahr

Thu
Fri
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Wind slabs are expected to remain reactive in exposed high elevation terrain on Tuesday. It may still be possible to trigger a buried weak layer in isolated areas but the likelihood is decreasing with the cooler weather. 

Lawinenprobleme

  • Wind Slabs

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

    Recent strong winds from the SW through NW have formed reactive wind slabs in exposed terrain at higher elevations. 

  • Cornices

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    Large cornices are expected with ongoing strong to extreme wind over the past week. A cornice failure has the potential to trigger a slab avalanche on the slope below. 

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely - Possible
    Größe
    1–2.5

    The late-January crust/surface hoar/facets down 20-40 cm remains a concern mainly where surface hoar may be preserved. 

    In the neighbouring Lizard-Flathead region, the mid-January crust/facet layer down 40-70 cm woke up over the weekend and may also be a concern for the South Rockies. 

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

Dry and mainly sunny conditions are expected for the week. A major warming event is current forecast to arrive late Wednesday which may persist for several days. 

Monday Night: Mainly clear, light to moderate W wind, freezing level dropping to valley bottom.

Tuesday: A mix of sun and cloud, light to moderate SW wind, freezing levels reaching around 1500 m.

Wednesday: Mainly sunny, light to moderate NW wind, freezing levels climbing to around 2000 m.

Thursday: Mainly sunny, moderate W wind, freezing levels reaching near 2500 m with an inversion.

Avalanche Summary

No new avalanches were reported on Sunday but observations were limited. 

This MIN report from Saturday describes a natural size 1.5 slab avalanche on a south aspect as well as shooting cracks and whumpfing while travelling. It also suggests the surface snow was getting warm and consolidating into a slab. 

Snowpack Summary

A new melt-freeze crust is expected on solar aspects into the alpine and on all aspects at lower elevations. Ongoing periods of strong to extreme wind from the southwest through northwest have formed reactive wind slabs and large cornices in exposed terrain at higher elevations. 

The January 30 interface is now typically down 20-40 cm and consists of a melt-freeze crust at lower elevations and on solar aspects extending into the alpine, spotty surface hoar in sheltered areas at and below treeline, and small facets in some areas. The January 18 rain crust is probably now around 40-70 cm deep and may have weak faceted snow above. 

The early December crust/facet persistent weak layer is now 100-200 cm deep. This layer produced numerous very large avalanches in January but is now considered dormant. See this forecaster blog on how to manage this layer as it may come into play again later this season. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of buried weak layers.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Cornices become weak with daytime heating or solar exposure.

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