Lawinenlagebericht

West Slopes North

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
2 · Mässig
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

Triggering avalanches is still possible in wind drifted snow near and above treeline. Identify and avoid steep terrain features when you find denser slabs sitting on softer snow below. 

Lawinenprobleme

  • Wind Slabs

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

    You can still trigger a wind slab in upper elevation terrain on Tuesday. Strong winds overnight into Monday morning likely created new slabs. Their size and depth are dependent on the amount of snow available for transport. Dense snow surfaces and sun crusts may have locked the surface snow in place but observations are lacking to prove this either way. New wind slabs should be identifiable as dense looking pillow or lens shaped drifts or may sound hollow when you travel across them. Track the distribution of wind loading and scouring as you gain elevation to help identify slopes where you may find wind slab. You are more likely to trigger them on steep convex rolls or other trigger points.  Use simple tests to see how well they are bonded to layers below - or simply bypass steep wind loaded features by using lower angle, planar terrain.

    Example of shallow wind slab avalanche. Note wind affected snow surfaces around slab.

    Photo: Kurt Heine

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    There is an increasingly low chance you could trigger an avalanche in crust-facet layering from late January, but the weak snowpack structure and recent avalanche activity show this problem is still worth factoring into your plan. These avalanches have mostly occurred where there is 2 or more feet of new snow over the crust. You can track the depth of new snow over the crust by pushing the handle of a ski pole into the new snow until it stops at the upper crust layer.

    Don't ignore obvious signs of instability like whumphing, shooting cracks, or previous avalanche activity where you identify old crusts in the bed surface. Minimize travel on steep slopes at upper elevations and remember persistent slab avalanches can be triggered from low on the slope or remotely. When assessing terrain, factor in not only the possibility of triggering a large avalanche but also the consequences in the terrain below if you are caught. 

    (2/5/2022)

    Large snowmobile triggered avalanche that released on late January crust-facet layers. NE aspect at 5400' Excelsior Peak area in Canyon Creek, West North

    Photo: Graham Clark

Avalanche Discussion

No new avalanche activity was reported on Monday. Moderate wind speeds, light precipitation, and limited sun should make for little change in danger in the next 24 hours.  High pressure, sunny skies, and much higher freezing levels are expected in the second half of the week. A corresponding increase in danger from wet avalanches is anticipated as well. 

Avalanches and other signs of instability related to deeper crust-facet layering continued Saturday and Sunday. On the other hand, snowpack test results vary widely and plenty of slopes where the problem could exist have been skied and ridden. Despite the uneven distribution of this problem a bit of a pattern is emerging. All avalanches and most whumphs have been on more northerly terrain, likely because the strong sun of late January melted the layers in question into a single stout crust. Also, the problem seems to be restricted to higher elevations. Crust-facet layers and other weak snow surfaces were found at all elevations during the January dry spell. Rain and very wet new snow that fell on January 30th may have wetted and ultimately strengthened these layers. Observations above 5000’ in West North and West Central have found faceted layers drier and weaker.

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