Avalanche forecast

South Coast Inland

Mar 5 – 6, 2020Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Snow and strong wind are forecast for Thursday, with the most snow in the north of the region. Slabs will rapidly grow and become touchy. Treat the danger as HIGH if you find more than 30 cm of snow or during periods of rapid loading.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    1.5–2.5

    A weak layer of feathery surface hoar may be found around 40 to 80 cm deep on northerly aspects around treeline and lower alpine elevations. This layer may be spotty and only found in sheltered terrain features. Assess the layer in the snowpack prior to committing to avalanche terrain or adopt a conservative mindset to avoid the problem.

    In the north of the region (e.g. Duffey, Hurley, Goldbridge), a deeper weak layer of faceted grains near the ground presents a lingering concern on steep, shallow slopes in the alpine. 

  • Storm Slabs

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

    Another storm impacts the region on Thursday, with snowfall amounts of 15 to 25 cm expected in the north and around 10 cm in the south. Slabs will build throughout the day with periods of rapid snowfall and strong southwest wind. Use added caution if you find more than 20 cm of snow accumulate from the storm or during periods of rapid loading from snow and/or wind.

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

WEDNESDAY NIGHT: Cloudy with snowfall, accumulation 5 to 10 cm, moderate to strong southwest wind, alpine temperature -8 C, freezing level 600 m.

THURSDAY: Cloudy with snowfall, accumulation 10 to 20 cm in the north of the region and trace to 10 cm in the south, strong southwest wind, alpine temperature -6 C, freezing level 1300 m.

FRIDAY: Morning snowfall then mix of sun and cloud with isolated flurries, accumulation 5 to 10 cm, light southwest wind, alpine temperature -10 C, freezing level 1000 m.

SATURDAY: Morning snowfall then a mix of sun and cloud, accumulation 5 cm, light southwest wind, alpine temperature -10 C, freezing level 800 m.

Avalanche Summary

A few small wind slab avalanches were triggered naturally on Tuesday in alpine terrain. Otherwise, no new avalanches were observed.

Snowpack Summary

The next storm on Wednesday night into Thursday will drop around 15 to 25 cm of snow for the north of the region and around 10 cm to the south. The snow will likely consolidate into a storm slab as the day unfolds, with particularly touchy conditions during periods of rapid snow loading. The wind will be strong from the southwest during the storm, so expect wind slab development in lee terrain features, particularly near ridges.

A weak layer of surface hoar crystals and/or faceted grains may be found around 40 to 80 cm deep on northerly aspects at treeline and lower alpine elevations. The layer may have been destroyed by strong wind immediately before burial on February 22nd, but it may still exist in sheltered terrain features. Where it is found, it has been reactive in snowpack tests. This persistent weak layer warrants investigation and a conservative terrain use strategy. Check out the latest forecaster blog that offers a deeper dive into these conditions.

In the northern part of the region (i.e., Duffey/Hurley/Goldbridge), a deep instability exists at the base of the snowpack. It has not produced an avalanche since February 17th. Rapid warming or heavy loading by new snow/wind/rain events have the potential to re-awaken this layer.

Terrain and Travel

  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.

Regions covered