Lawinenlagebericht

Central Cascades

Central Oregon Avalanche Center
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Lawinengefahr

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

Triggering avalanches will be likely in wind drifted snow. It will be best to avoid slopes where wind blown snow has accumulated especially in areas with large pillow drifts in steep terrain. It will be possible to trigger large avalanches on slopes where the recent storm snow has settled on a layer of weak sugary faceted snow; primarily on west, north, and east facing slopes near treeline and below treeline. Recognize where terrain traps such as rocks, trees, cliffs, and constricted features are in relation to where you are travelling; this type of terrain can greatly increase the consequence of getting caught in an avalanche. If you are unsure about the stability of the snowpack, stick to slopes less than 30 degrees steep to minimize your exposure to avalanches.  

Lawinenprobleme

  • Wind Slabs

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

    New incoming snow falling out of the sky will be minimal, however there is still soft snow on the surface  that can be moved by the wind. On west, north, and east facing slopes wind slabs can fail on the old snow interface of weak/sugary faceted snow and will have the chance to propagate wider and run farther than usual. Observe where blowing snow is moving and where that snow is landing. Look for visual clues to such as ripples in the snow or pillowy drifts to identify loaded slopes. Below ridges and highpoints are common places where wind slabs can be triggered. As wind moves snow across open slopes, gully features in particular can become 'cross loaded' and filled in with new wind slabs.  Cracking in the wind deposited snow and recent avalanches are good indicators that you can trigger an avalanche. Wind slabs can be avoided by sticking to sheltered areas or slopes that have been scoured by the wind. 

    Use carefull evaluation in areas of sparse trees, clearings, and sections of dead forests. Open areas 'below treeline' can get enough blowing snow to create wind slabs.

  • Persistent Slabs

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

    Observers have been finding weak faceted snow under the recent storm snow. Prior to the latest storm, during the period of high pressure, surface snow on cold shaded slopes underwent the faceting process. That faceted snow subsequently got buried under 12 - 16" of new snow. The structure for this problem is there: strong snow over old weak snow. 

    "Persistent Slabs are characterized by difficult to manage and often surprising behavior.  They can be triggered long after a storm has passed or release under modest loading events. They may be triggered remotely—from flatter terrain below, above, and to the sides of steep slopes. The slabs often propagate widely and in unpredictable ways. Shooting cracks and collapses are clear warning signs of the problem. However, feedback is often irregular because of spatial differences in weak layer and slab thickness. Thus, tracks on a slope are not an indicator of stability.  For these reasons, Persistent Slabs require a wide margin for error. The most reliable way to manage Persistent Slabs is to make conservative terrain choices. This often means avoiding travel on or below steep terrain where the problem exists." - National Avalanche Center

    In recent days observers have encountered collapses (the slope drops as the weak layer compresses) along with the "whumph" sound. Several remote triggers have been reported on north and east aspects at mid elevations

    Give yourself some margin with this one, the weak layer may also be present on select SW and SE slopes. With the cold temperatures in the forecast, this weak layer will stick around for a while.

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