Avalanche forecast

South Coast

Apr 15 – 16, 2015Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Tricky winter conditions exist at higher elevations. Solar radiation and rising temperatures are forecast and avalanche hazard can rise quickly. Use a conservative approach and watch for signs of instabilities.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Strong winds have built wind slabs in lee terrain in the alpine and at treeline. They are especially touchy where they sit on buried facets, surface hoar and/ or crusts. Weak, looming cornices may fail with solar radiation and trigger slopes below.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–5
    No recent activity has been reported on this layer, but it's still there, it could produce a large avalanche if triggered. Large loads like cornice fall, intense warming, or hitting the sweet spot in thin-thick snowpack areas could act as a trigger.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–3
    Solar radiation and rising freezing levels will deteriorate the snowpack. Travel on sunny slopes early, and watch for obvious signs of instabilities like avalanches, moist surface snow and snowballing.

Confidence

Poor - Due to the number of field observations

Weather Forecast

The current wintery weather pattern begins to change as a dominant upper ridge sets up over the province. The next frontal system seems to just skirt north of the South Coast region bringing little to no precipitation. Thursday and Friday will see a mix of sun and cloud. Ridgetop winds will be moderate  from the west and freezing levels will rise to 2700 m. Saturday will be mostly sunny with alpine temperatures rising to +6.0 degrees with light ridgetop winds. Freezing levels will remain at 2600 m. The ridge  will remain stationary until Wednesday bringing warm air and sunny skies.

Avalanche Summary

No reports of avalanche activity from yesterday. This is most likely as a result of few field observations. I suspect wind slab activity with new loading and strong winds. Strong solar radiation and warming expected on Thursday will likely initiate a natural avalanche cycle. Watch overhead hazards like cornices.

Snowpack Summary

Anywhere from 20 to 50 cm of recent storm snow sits on a variety of old surfaces including crusts, surface hoar and facets that were buried April 10th. Moderate to strong south west winds are redistributing the storm snow into wind slabs on leeward slopes and terrain features. The mid-March persistent weak layer of facets on a crust is now approximately 50-100 cm down. This remains a concern in the region due to its potential to produce very large avalanches. There may be a low probability of triggering this layer, however; if it is triggered the consequence would be high. Large looming cornices may become weak with solar radiation and daytime warming. If a cornice fails it could trigger a large avalanche from the slope below.

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