Lawinenlagebericht

West Slopes North

Northwest Avalanche Center
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Lawinengefahr

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

Kernpunkte

You can find shallow slabs of wind drifted snow above treeline. Evaluate the bond of new slabs to the old snow surface while climbing into exposed alpine terrain. Prepare for challenging travel on a frozen crust below the new snow. 

Lawinenprobleme

  • Persistent Slabs

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

    In addition to small wind slabs, there is still a low likelihood of triggering a larger avalanche in crust-facet layers from late January. Though no human triggered, persistent slab avalanches were reported since February 5th, three natural avalanches were observed in the last week on Shuksan, Table Mountain, and Mt. Baker. 

    • The snowpack structure is weak around and within the crust-facet layers buried on January 30th.
    • The layers are still reactive above 5400’ on aspects that did not receive strong sun during the late January high pressure.
    • Natural avalanches continue to occur during periods of loading or with significant warming on normally shadedaspects [greenhousing, light rain, etc]. 
    • They occurred where there are 2 or more feet of new snow over the crust-facet layering.
    • Snowpack tests produce inconsistent results, sometimes even in the same snowpit.
    • Many steep slopes - some very near avalanches that released in the same layers - have been ridden and skied with no results.

    When assessing shady alpine terrain, consider that persistent slab avalanches can be triggered from low on the slope or remotely. Factor in not only the possibility of triggering a large avalanche but also the consequences in the terrain below if you are caught. 

    (2/12/2022)

    Natural avalanche suspected of failing in January 30th crust-facet layers. The estimated date of occurrence is between Feb 8th-11th. East-northeast aspect at 6200' or Mt. Baker/Schriebers.

    Photo: Graham Clark 

     

Avalanche Discussion

Monday's "storm" put down 2-4" of new snow across West North with potentially a few more inches above treeline. At near treeline elevations, the new snow was observed as bonding with the crust below.  If heading into higher elevation terrain, be on the lookout for fresh winds slabs. Approach wind loaded slopes with caution as even a small avalanche can be consequential in extreme terrain. You may see rollerballs - or even very small loose wet avalanches - on southerly slopes during periods of clear sky.

Below Monday's powder, 30-70cm of settled snow overlays the January 30th crust interface. Above the crust, layer interfaces that produced widespread avalanche activity February 5-6th are gaining strength. Faceted snow between the late January crust layers is rounding but still produces sudden results with compression tests and large column tests still point towards propagation. 

Icy or dust-on-crust conditions will make for challenging travel in many areas. Below the new snow, a very firm crust can be found on solar aspects and all aspects below treeline. 1-2cm of breakable crust with dry snow below was found on upper elevation, shaded slopes last weekend.

 

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