Lawinenlagebericht

North Rockies

Feb 9 – 10, 2022Avalanche Canada
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Lawinengefahr

Fri
Sat
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Warm temperatures, rain below treeline and snow up high with strong to extreme wind will increase the likelihood of triggering the buried weak layer where it is present, destabilize the snowpack below treeline and build fresh wind slabs at higher elevations.

Lawinenprobleme

  • Persistent Slabs

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

    The recent snow loaded a weak layer of surface hoar crystals in some areas, which is at a prime depth for human triggering. The layer is most prominent in areas sheltered from the wind at and below treeline. Example terrain features to particularly treat as suspect include the lee side of ridges, openings in trees, cut blocks, and burns. Large, wide-propagating avalanches could result where this layer is present. 

    The buried weak layer was reported to be present up to treeline in the Torpy Sande and Pine Pass areas and in isolated areas in the Renshaw. Avalanche activity on this layer was reported in the south of the region.

  • Storm Slabs

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

    By the end of Wednesday, up to 20 cm of new snow is forecast, primarily in the southwest of the region. Expect to find wind slabs in lee terrain features at higher elevations from strong to extreme southwest wind. Storm slabs may be found in sheltered terrain. Slabs will be especially touchy where they sit on a buried weak layer of surface hoar.

  • Loose Wet

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

    Warm temperatures and rain up to treeline will destabilize the snowpack. Wet loose avalanches can be expected.

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

TUESDAY NIGHT: Cloudy with snowfall, 5 to 15 cm new snow and rain at lower elevations, strong southwest wind, alpine temperature -1 C, freezing level 1700 m.

WEDNESDAY: Cloudy with snowfall, 5 to 10 cm new snow with the higher amounts in the southwest of the region, rain at lower elevations, strong to extreme southwest wind, alpine temperature +2 C, freezing level rising to 2200 m.

THURSDAY: Mix of sun and cloud, 5 to 10 cm new snow with the higher amounts in the west of the region, strong to extreme west wind, alpine temperature -4 C, freezing level dropping to 1400 m.  

FRIDAY: Mostly sunny, moderate westerly wind, alpine temperature -4 C, freezing level 1300 m.

Avalanche Summary

On Monday, a small skier triggered wind slab avalanche was reported and several smaller slab avalanches released naturally on the buried weak layer. Wet loose avalanches were observed below 1000 m. 

On Sunday, a deep persistent slab avalanche was likely triggered naturally by intense warming and sun and released on depth hoar or the November crust. It occurred just south of the region (see this MIN report). Explosives triggered several large wind slab avalanches up to size 3.

On Saturday, several storm and wind slab avalanches up to size 2 were observed at treeline and in the alpine. Most of these avalanches released naturally, and two were likely triggered by riders.

Snowpack Summary

The recent storm brought 10 to 20 cm new snow and rain below 1000 m. The new snow formed storm slabs in sheltered areas and wind slabs in lee terrain features from strong south and west wind. This new snow added to the previous storm which brought 40 to 60 cm for much of the region, with the most in the southwest of the region and the least to the east of the divide and in the north. 

The snow will be particularly touchy where it sits on a weak layer of surface hoar crystals. Reports suggest that the surface hoar is likely most prominent in sheltered openings at and below treeline but could extend into wind-sheltered terrain in the alpine. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns.

The lower snowpack is generally strong and well-bonded. The base of the snowpack is expected to be weak and faceted in shallow, rocky slopes east of the divide.

Terrain and Travel

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Rain or periods of intense solar radiation can rapidly enhance the effects of warming.

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