Lawinenlagebericht

West Slopes North

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 5 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Steep terrain holding wind drifted new snow is where you are most likely to trigger an avalanche. Track the change of new snow depth as you travel and default to lower angle slopes where you identify areas of wind loading. 

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2.5

    Wind slab avalanches were triggered in near and above treeline terrain on Monday. They occurred on steep, unsupported terrain features. Small avalanches were observed to have released in a layer of colder, lighter snow about 10” down created by a quick drop in temperatures and a period of less wind on Sunday evening. A larger, remotely triggered avalanche on Shuksan Arm failed at or near the old surface crust buried by new snow on Sunday (photo).

    The wind slab distribution pattern is highly variable with big changes in slab depth over short distances. You can visually identify areas of wind loading by looking for pillowy drifts, cornices, and scoured snow surfaces. Dig down or use the handle of a ski pole to track the depth of new wind slabs over the old surface crust. Use simple tests like test slopes and hand shears to gather information as you gain elevation. Choose lower angle, planar slopes over unsupported, convex features to reduce the risk of triggering an avalanche in wind loaded terrain.

    (1/31/2022)

    Large, remotely triggered wind slab avalanche on Shuksan Arm - N aspect @ ~5400'. Rain-affected crust/old snow surface is visible at the bed surface.

    Photo: Liza Kimberly

Avalanche Discussion

Precipitation totals from the last storm ranged from 2.25" at Heather Meadows to 1" in less favored locations. Though precipitation turned to snow at all elevations on Sunday evening, it fell as rain or warm, wet snow in near treeline areas for most of the day.  New snow depths of 1' were observed with up to 2' in wind loaded locations. Winds were strong during most of the storm with a lull when snow levels dropped.  Another period of strong winds formed additional wind slabs Monday morning.

Warm conditions at the outset of the storm seemed to have a positive effect on the bond of new snow and wind slab layers. Snowpack observations near treeline found wet snow made for a good bond to the wide variety of old snow surfaces. Wind slab avalanches at this elevation were shallow and released within the layers of new snow. It is a different story moving into alpine terrain as colder snow may have preserved weak snow surfaces and provided the setup for surprising avalanches like the one that occurred on Shuksan Arm on Monday. 

Use extra caution and go with a conservative terrain mindset moving into higher terrain. Though no natural avalanches were observed above treeline, a large, remotely triggered avalanche is a telling sign there could be a major difference in snow stability with a small gain in elevation.

 

 

 

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