Lawinenlagebericht

Purcells

Apr 12 – 13, 2012Avalanche Canada
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Lawinengefahr

Sat
Sun
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible - Likely
    Größe
    1–4
    New snow above 1500m, and moderate Southerly winds are the perfect recipe for building wind slabs. They are likely found on lee slopes, and behind terrain features at treeline elevations and higher. Cornices are large and may trigger slopes below.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–5
    Light-moderate amounts of precipitation is continued through to Saturday. Watch for loose wet avalanches BTL. They may entrain more mass and run farther than expected.

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely - Possible
    Größe
    3–7
    The odd deep slab could still be out there, I'm still suspect of steeper unsupported slopes & places where the snowpack goes from thick to thin, especially near ridge crest and around rock outcroppings.

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

A low pressure center is moving into Southern Alberta where it looks to remain stationary through to Friday. This low will continue to spread light-moderate amounts of precipitation to the region through Saturday. Sunday looks to be sunny, solar radiation will be intense when the sun pokes through. Freezing levels will hover near 1600 m until Saturday night, and then fall to valley bottom. Ridgetop winds will be moderate from the West, switching Easterly on Sunday.

Avalanche Summary

On Wednesday many natural loose wet avalanches were reported up to size 2.5 on South aspects. A significant size 3 wet slab was also seen on a south aspect before lunch time.

Snowpack Summary

Mild temperatures have settled out much of the upper snowpack. Spring-like conditions prevail; with surface crusts on solar aspects and melt conditions (no overnight re-freeze) on all aspects below 1700 m. New wind slabs may build with forecast snow and wind at upper elevations. Cornices are large and exist on most ridgelines. I don't expect this to be an immediate problem until it heats back up again, possibly Sunday. Up to 100 cm sits on the March 27th interface. This interface consists of a buried sun crust on southerly aspects and a temperature crust on more northerly slopes. A thin layer of facets and or surface hoar can be found on this crust on all aspects. The bond on this interface seems to be improving. The mid-pack is well settled and strong. At the base of the snowpack sits a weak layer of facets and depth hoar. I'd be suspect of steeper unsupported slopes where the snowpack goes from thin to thick.

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