Lawinenlagebericht

South Coast

Feb 14 – 15, 2016Avalanche Canada
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Archiviert · abgelaufen 11 years ago

Lawinengefahr

Tue
Wed
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

The hazard rating reflects conditions in the south of the region where enhanced snowfall is possible on Monday.  Wind slabs are expected throughout the region but if any areas see more than 25cm, a more widespread storm slab problem could develop.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–3
    Recently formed wind slabs are expected to be reactive throughout most of the region but a more widespread storm slab problem has the potential to form in the south of the region if we see enhanced snowfall Sunday overnight and/or Monday.

  • Cornices

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–4
    Looming cornices could collapse, especially during storms or during warm weather.  The weight of a person may be enough to cause a cornice failure.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely - Possible
    Größe
    3–6
    While the probability of triggering deeper layers are low, the consequences of such a slide would be large. Most likely trigger points are steep, rocky start zones in lower snow parts in the north of the forecast region (Duffey Lake or Chilcotins).

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain on Monday

Weather Forecast

Light snowfall is expected to continue Sunday overnight before a weak ridge of high pressure dries things out briefly on Monday morning. However, the southern part of the region may see enhanced snowfall Sunday overnight and Monday due to a storm tracking through Washington.  The next substantial storm system is then expected to reach the south coast on Monday afternoon or evening. 5-10cm is possible Monday afternoon with freezing progressively climbing to around 1800m by Monday night. Another 20-30cm is forecast for Monday overnight with strong southwest winds in the alpine. Tuesday is forecast to be mainly dry with light alpine winds and afternoon freezing levels around 1500m. A weak storm system is forecast to arrive on Wednesday with freezing levels around 1800m.

Avalanche Summary

On Saturday, a ski cut produced a size 1 slab avalanche in a leeward feature on a northeast aspect at 2200m. The slab was 10-20cm thick. On Friday, ski cuts produced size 1 loose wet avalanches at treeline in the recent storm snow. Rain-soaked lower elevations are unlikely to see much in the way of avalanche activity, but wind slab avalanches will continue to be reactive to human-triggering at higher elevations with ongoing snowfall and wind continuing overnight Sunday. Cornices are reported to large and fragile, and may fail under the weight of a person. Deeply buried persistent weak layers may still be reactive in the region but would probably take a heavy trigger like a cornice fall or smaller avalanche stepping down to cause a deep failure.

Snowpack Summary

Recent snowfall and mostly southwestern winds have formed wind slabs in the leeward features in the alpine and at treeline. High freezing levels (around 1800 metres) has settled the upper snowpack and developed variable crusts due to overnight cooling. New surface hoar has been reported from the Coquihalla area, that may be buried down 20-30 cm. Conditions across the region are variable. Most areas have not had a freeze below treeline since the last wet storm. A crust that formed after a warm storm at the end of January is now down 50-80 cm. and it does not appear to "bridge" the early January weak layer in the Duffey lake area. This deeply buried persistent weak layer from early January appears to be isolated to the north of the region, and is now buried down about 50-80 cm. This layer continues to produce sudden results in snowpack tests and has been responsible for recent destructive avalanches.

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