Avalanche forecast

Northwest Coastal

Mar 24 – 25, 2014Avalanche Canada
View on map
Archived · expired 13 years ago

Avalanche danger

Wed
Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
Open full map

Highlights

Forecast new snow and wind are expected to increase the avalanche danger.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–5
    The early March persistent weak layer is buried deep enough to produce large avalanches when triggered. The added load of the recent storm slabs may result in deep slab avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–4
    Forecast new snow may increase the load of recent storm slabs above a mix of old surfaces. Watch for pockets of wind transported snow at and above treeline.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–6
    The early February persistent weak layer is buried deeply in the snowpack and continues to be a concern. Heavy loads like cornice falls or storm slab avalanches in motion may trigger this weak layer resulting in very large avalanches.

Confidence

Fair - Forecast snowfall amounts are uncertain on Tuesday

Weather Forecast

Overnight and Tuesday: Some Pacific moisture (3-5 cm) is expected to push into the Northern coastal areas and then slide inland. Mostly overcast with light precipitation, cold alpine temperatures, and moderate to strong Southwest winds. Freezing levels at about 500 metres.Wednesday: Overcast with light precipitation and light winds. Freezing level about 500 metres and alpine temperatures around -15.Thursday: Overcast with a chance of sunny breaks in the afternoon. Light Easterly winds and temperatures around -15 in the alpine.

Avalanche Summary

We have a report of size 3.5 natural avalanche from a Northwest aspect that released down 100-150 cm on the deeply buried February persistent weak layer. It is suspected that this avalanche was triggered sympathetically to a size 1.5 solar release on an adjacent slope.

Snowpack Summary

The area has received 75 to 150cm of snow over the past 5 to 7 days. The recent storm snow arrived with strong winds and produced wind slabs at tree line and above and increasing the depth on the slab that now overlies the March persistent weak layer. In addition, much of the recent storm snow has fallen on a melt freeze and/or rain crusts that exist in most parts of the region below 1200 metres. The March weak layer is a combination of hard wind-scoured slab surfaces in exposed terrain, facets and/or surface hoar in sheltered and north aspects, and sun crust on steep solar aspects. This layer is widespread throughout the forecast region and is now buried close to 150cm in most parts of the area. A late January/early February crust/facet/surface hoar combo is still showing up in snowpack tests with moderate to hard shear tests. It appears to be dormant for the time being, but a sudden increase in load, a cornice failure, or a large rainfall event could "wake up" this layer and result in a large destructive avalanche.

Regions covered