Lawinenlagebericht

Northwest Inland

Feb 15, 2017Avalanche Canada
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Lawinengefahr

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

Sustained warming is set to undermine stability over the coming days. The scale of the impact is uncertain, but the strength of the snowpack is being tested

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2
    Last week's outflow winds have shifted to a strong southwest flow, coupled with light accumulations of new snow. The changed pattern leaves us with a mix of touchy new wind slabs along with older, more stubborn hard slabs on a wide range of aspects.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely - Very Likely
    Größe
    1–2
    Rain and moist snow accumulating at lower elevations will promote loose wet avalanches on Monday, especially in steep terrain. This problem will present at higher elevations as the freezing level rises.

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–4
    A weakness at the bottom of the snowpack is lingering and may be triggered in shallow snowpack areas or by the weight of smaller avalanches. The potential for a deep release on this layer will remain elevated while warm temperatures persist.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Wednesday: 3-5 cm of new snow / Strong southwest winds / Freezing level at about 1100mThursday: 2-4 cm / Light and variable winds / Freezing level at about 1100mFriday: Light flurries / Light and variable winds / Freezing level at about 800m

Avalanche Summary

A MIN report from Sunday includes observations of recent Size 2 wind slab in the Hudson Bay area that is suspected to have run naturally on an east aspect. Perhaps more striking is the fact that the party also experienced several whumphs, suspected to be failures at one of our more shallow persistent weak layers. For Wednesday, expect recently formed wind slabs to be reactive to human triggering. Older hard slabs may be more stubborn, but also capable of much wider propagation. A storm focused on the north coast has brought modest new snow accumulations inland along with strong to extreme southwest winds that have promoted the formation of touchy new wind slabs in lee areas. Also keep in mind that a basal weakness continues to drive a low probability/high consequence deep persistent avalanche problem for the region. Very large avalanches remain possible, especially in shallow snowpack areas and as warm temperatures begin to penetrate deeper into the snowpack.

Snowpack Summary

A light snowfall over most of the region has given a thin cover to the widespread wind affected surfaces recently reported in exposed terrain. This includes scoured surfaces, sastrugi, and hard wind slabs as well as a rain crust below about 1400 m. The new snow will contribute to wind slab formation in wind exposed areas while covering faceted surface snow as well as surface hoar in more sheltered areas. Deeper in the snowpack, several buried surface hoar layers can be found between 30-70 cm deep. Recent reports suggest these layers have generally stabilized but isolated weaknesses may still exist, especially where buried surface hoar is still intact. A generally stiff mid pack sits above weak sugary snow near the ground. This basal weakness woke up during the last storm and produced numerous large avalanches which released on the ground. The layer has recently been considered dormant but it may become active once again with sustained warming over the coming days. It may also be possible for a smaller avalanche to 'step down' to this layer.

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