Avalanche forecast

Northwest Coastal

Jan 30 – 31, 2015Avalanche Canada
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Avalanche danger

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

Sun and solar radiation may have a significant destabilizing effect on the snowpack. As freezing levels rise throughout Saturday, so will the Avalanche Danger.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–6
    Although less likely to trigger, persistent weak layers are still capable of producing large and destructive avalanches in isolated terrain. Possible triggers include a cornice fall or intense solar radiation.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Storm accumulations from Friday will likely remain sensitive to human triggering. Expect increased reactivity in wind-exposed terrain. A smaller surface avalanche in motion may also trigger a larger avalanche on deeper layers.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    Watch for pushy loose wet avalanches in steep, sun-exposed terrain on Saturday. Loose wet avalanches have the potential to "step-down" to deeper, more destructive layers.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Friday's storm system will dissipate on Saturday as a weak ridge develops. On Sunday and Monday, the ridge will flatten-out allowing for a series of pacific system to impact the region. Saturday: Generally clear skies with valley fog / Light northwest winds / Freezing level at 1600m Sunday: Up to 15cm of new snow / Moderate southwest winds / Freezing level at 400m Overnight Sunday and Monday: Up to 25cm of new snow / Moderate southwest winds / Freezing level at valley bottom

Avalanche Summary

At the time of publishing this bulletin, there was no new avalanche activity reported from the field. That said, I'm sure there was a healthy round of storm slab activity in response to heavy snow accumulations on Friday. Looking forward, I'd remain cautious of recently formed storm slabs, as they may remain sensitive to human triggering, especially in wind-exposed terrain. Additionally, persistent weak layers should remain on your radar as they may become reactive with the loading of the new snow, or with warming and solar radiation forecast for Saturday. Any avalanche on these deeper persistent weaknesses would be destructive in nature.

Snowpack Summary

Moderate to heavy snowfall (with rain at lower elevations) and strong southwest winds have likely built deep and dense storm slabs. These storm slabs are expected to be most reactive in wind-exposed, upper elevation terrain. A rain crust and/or surface hoar layer buried mid-January can be found about 100cm below the surface, the depth varying greatly depending on whether the slope is wind-loaded or wind-scoured. The structure of this layer may have strengthened somewhat. Still, I would recommend giving this layer a little more time to bond before discounting it from the avalanche equation. The November crust/ facet combo near the bottom of the snowpack is thought to be generally well bonded. However, this deep and destructive layer is still reported to be reactive in the far north of the region.

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