Avalanche forecast

Northwest Coastal

Apr 22 – 23, 2014Avalanche Canada
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Avalanche danger

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

Avalanche danger can rise quickly with afternoon warming and solar radiation. Deeply buried persistent weak layers may re-awaken during these periods.For more insight into spring danger ratings, check out this blog post.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    Wind slabs from the weekend storm may still be sensitive to human-triggering. These formed in leeward alpine features from strong S-SW winds.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    1–2
    Loose wet activity can be expected from steep features during periods of solar warming or rain. Isolated wet slabs may be possible under the same conditions where the recent storm snow is poorly bonded to the underlying crust.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–7
    A deeply buried persistent weak layer still has the potential to produce very large avalanches and could be triggered by heavy triggers such as cornice falls or smaller avalanches stepping-down.

Confidence

Poor - Due to the number of field observations

Weather Forecast

On Wednesday, the south of the region is expected to be mostly dry and sunny, and the north of the region is expected to be cloudy with scattered precipitation. Thursday should be mostly dry and sunny across the region with convective flurries. Warm temperatures with no overnight recovery are expected Wednesday and Thursday nights. There is the possibility of a weak storm system for parts of the region on Friday but it is uncertain.Wednesday: Clear in the south, cloudy in the north, scattered precipitation 0-4mm, freezing level am: 600m pm: 1200m, ridgetop wind: light variableThursday: Mostly sunny, freezing level am: 1200m pm: 1700m, ridgetop wind: moderate SEFriday: Unsettled conditions, freezing level am: 1300m pm: 1400m, ridgetop wind: moderate SE

Avalanche Summary

We received a report of a very large natural deep-slab avalanche east of Terrace on Monday. This avalanche occurred on a NW aspect at 1800m. The crown appears to be 1-2m deep meaning it likely released on the early-Feb weak layer. We are no longer receiving professional daily reports for the region so public observations are really appreciated right now. If you are out in the mountains, send your observations to [email protected]

Snowpack Summary

Highly variable spring conditions are being reported in the region. At lower below-treeline elevations the snowpack is typically wet and isothermal. It has not been refreezing overnight and is melting quickly. Between roughly 1000 and 1500m, the snowpack has been undergoing daily melt-freeze cycles. The same conditions can be expected on sun-exposed slopes all the way to mountain-top. On higher elevation north-facing slopes, dry snow likely still exists. Recent strong S through W winds have scoured windward slopes and created wind slabs in leeward slopes. The early February crust/facet layer is typically down 1.5 to 2.5m. A smaller avalanche or a cornice fall may still have the potential to step down to this layer causing very large, destructive avalanches, especially during warm sunny periods.

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