Lawinenlagebericht

Purcells

Apr 11 – 12, 2012Avalanche Canada
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Lawinengefahr

Fri
Sat
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Confidence in the track and timing of incoming precipitation is fair. The region may receive heavier amounts of precipitation than forecast. If this occurs, expect the danger ratings to be elevated.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible - Likely
    Größe
    1–4
    Forecast new snow above 1500 m, and moderate Southerly winds may create the perfect a recipe for building wind slabs on lee slopes, and behind terrain features at treeline elevations and higher.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Very Likely - Certain
    Größe
    1–5
    Moderate-possibly heavy amounts of precipitation up to 1500 m is expected for Thursday. 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

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

Weather Forecast

A low pressure center sitting SW of Montana will continue to move SE, this should be arriving in Southern Alberta by Thursday afternoon. Depending on timing and track, this low may spread moderate-heavy amounts of precipitation to the BC interior Wednesday night into Thursday and Friday. Ridgetop winds will start light-moderate from the South, switching moderate SW through Thursday. Freezing levels will fall to 1800 m. Light-moderate precipitation expected for Friday. Freezing levels near 1500 m. The weekend will see a fairly inactive ridge of high pressure dominating the interior, bringing sunny skies and freezing levels up to 2000 m. Confidence is poor for Thursday/Friday due to the uncertainty of the lows location in Alberta. This could potentially bring more than anticipated precipitation amounts to the regions.

Avalanche Summary

On Wednesday many loose wet avalanches were reported up to size 2. 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. 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 Saturday. 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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