Lawinenlagebericht

Central Cascades

Central Oregon Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Veraltet — dieser Lagebericht ist 2 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

New snow over the last few days has fallen on a variety of surfaces from the January dry spell, creating complex avalanche conditions and a weak snow structure in many areas. Triggering avalanches will be possible where the new snow lies over a buried weak layer, as well as where wind has loaded recent snow on slopes. These conditions could exist on any slope facing West to East, at all elevations. The conditions we are seeing deserve a wider safety margin, so if you are unsure about the stability of the snowpack, stick to slopes less than 30 degrees steep to minimize exposure to potential avalanches.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    The dry weather in January resulted in Near Surface Faceting on shaded slopes at and below treeline throughout much of the Central Cascades. In these areas, recent storm snow fell on this weak faceted layer. This has resulted in the current presence of a poor snowpack structure, as this weak layer lacks the strength to support the stronger new snow above it. Observations show that this layer is likely to be anywhere from 16" to to 24" below the snow surface in these areas. It may be easier to initiate a persistent slab avalanche where the new snow (ie slab) is shallower, and it will be more consequential where the slab is deeper. 

    Persistent slab problems act differently than our typical wind slab and storm slab problems, with increased spatial variability, greater likelihood to be triggered remotely, and often wider propagation. This demands a wider safety margin and careful consideration when recreating in the backcountry. Collapses, or audible "whoomfs" are clear warning signs this problem exists, along with shooting cracks on a slope. The most reliable way to manage Persistent Slabs is through conservative decision making with terrain choices. Avoid travel on or below steep terrain where this problem exists.

     

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Winds tapered down on Monday, but there is still plenty of new snow available for transport, and the recent low density snowfall we have received does not require strong winds to drift onto leeward slopes. Additionally, lingering wind slabs formed during the stormy weekend weather may still be reactive, especially when in the presence of an underlying weak, faceted snow layer. It is important to remember that a small avalanche can also trigger a bigger one that releases deeper layers of weak snow.

    Look for snow actively blowing around from the wind to help show you which slopes are loading. If you do not observe active transport, textured or scoured surfaces and cornices will help point you towards the conequent slopes holding wind drifted snow, where the surface will appear smooth and pillowed. Low consequence indicator slopes can be good testing grounds to assess wind slabs.

Avalanche Discussion

On Tuesday I observed the presence of unconcolidated, low density surface snow below treeline and in sheltered areas near treeline. Small Loose Dry "sluffs" may present themselves in these locations, and are worth considering if descending slopes above terrain traps where getting knocked off your feet could have higher consequences. Additionally (and non-avalanche related), deep snow brings the risk of snow immersion. Keep partners in sight or at least be able to communicate at all times when skiing through treed areas where this hazard is present.

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