Avalanche forecast

Northwest Inland

Mar 17 – 19, 2020Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Assess for wind slabs in steep terrain. The sun will weaken the snow and cornices as the day progresses, which could trigger large avalanches.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Strong winds have drifted recent snow into wind slabs that are possible to trigger, especially in areas where surface hoar sits at the interface. 

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Loose wet avalanche activity is most likely during the heat of the day when clear skies prevail. Avoid overhead exposure on sun-exposed slopes as the snowpack heats up. Note that cornices are also large and could release during daytime heating.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–3.5

    As spring-like weather takes over, the likelihood of avalanches releasing on buried weak layers increases. A few layers of surface hoar may be found around 40 to 90 cm deep and faceted grains may exist near the base of the snowpack. Sporadic destructive avalanches have occurred on the basal faceted grains, predominantly on north through east aspects in alpine terrain. Cornice falls are a possible trigger for deep persistent slab avalanches.

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

TUESDAY NIGHT: Clear skies, light northeast wind, alpine temperature -7 C.

WEDNESDAY: Mix of sun and cloud, light northwest wind, alpine temperature -5 C, freezing level 1000 m.

THURSDAY: Mix of sun and cloud, light southeast wind, apine temperature -6 C, freezing level 1000 m.

FRIDAY: Mix of sun and cloud, light northwest wind, alpine temperature -4 C, freezing level 1200 m.

Avalanche Summary

Loose wet avalanche activity was observed on sun-exposed slopes on Monday. Otherwise, no new avalanches were observed.

Snowpack Summary

Wind has varied in direction, meaning that wind slabs may be found on all aspects, particularly in steep terrain adjacent to ridges.

Two layers of surface hoar layer buried on March 1st and February 19 may be found around 40 to 90 cm deep. These layers have been most sensitive to human triggering at treeline elevations.

Near the base of the snowpack, an early-season layer of faceted grains and melt-freeze crust may linger. The most suspect locations to trigger this layer would be where the snowpack is thin near rocky outcrops. A large load, such as a cornice fall, also has the potential of triggering it.

Terrain and Travel

  • Carefully evaluate steep lines for wind slabs.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.

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