Lawinenlagebericht

West Slopes North

Northwest Avalanche Center
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Lawinengefahr

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

 

The Cascades are exiting a period of heavy snowfall and widespread natural avalanche activity. Dangerous avalanche conditions still exist in many areas. Consider all steep slopes near and above treeline as places where you can trigger an avalanche and minimize time spent exposed to large avalanche paths above you. 

Lawinenprobleme

  • Storm Slabs

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

    Heavy snowfall at near freezing temperatures created dense new slabs on all aspects. They add an impressive load above an upper snowpack of cold, light density snow which fell since Christmas. Though the likelihood of triggering an avalanche is decreasing, the snowpack needs time to adjust. On Saturday consider all steep slopes to be suspect if you are planning travel in avalanche terrain, especially if you observe signs of active wind loading or  experience periods of intense snowfall. Defualt to lower angle, sheltered terrain to reduce risk. Very large human or naturally triggered avalanches which could run long distances are still possible. Err on the side of caution when travelling near or below avalanche terrain. 

    Example of large slab avalanche in alpine terrain on Mt. Shuksan

    Photo: Adam Ü

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    3

    In the West North we are still suspicious of a layer of surface hoar buried on December 21st. It produced and a handful of very large avalanches centered around Shuksan Arm in late December. Some released naturally while others were triggered with avalanche mitigation work. We’ve had several storms since then and the layer is probably between 5 and 9 feet deep. These avalanches are very difficult for a single person to trigger. On the other hand they could react to a large load like a falling cornice or a smaller avalanche stepping down and triggering a much larger avalanche at this layer. Be aware that large deep slab avalanches from higher terrain could run into lower elevations where avalanches are not normally seen.

    (12/29/2021)

    Side profile photo of a very large slab avalanche on Shuksan Arm. It failed at the layer of surface hoar buried on 12/21. 

    Photo: Lee Lazzara

Avalanche Discussion

We are at the tail end of large storm that impacted the entirety of the Cascades with natural avalanche cycles, road closures, and other impacts in areas that rarely experience avalanches. Though danger is decreasing, observations are very limited. Most recent observations are from terrain adjacent to roadways or ski areas. Uncertainty is high in regards to the specifics of avalanche activity that would help in determining danger coming out of this impressive event.

A second large natural avalanche was reported having run down to Highway 20 east of Newhalem, this time a loose wet avalanche related to rising snow levels Thursday night. Avalanche mitigation work Friday at Mt. Baker produced numerous large avalanches in new snow layers plus one very large natrual avalanche just outside the ski area.

In the past 24 hours, Heather Meadows picked up 2.6” of precipitation falling as 2’ of new snow along with some rain early in the storm.  A noticeable rain crust from Thursday sits at the base of the most recent snowfall. The new snow layers were observed to be bonding to this crust by the afternoon. Light snowfall will continue through Saturday with snow levels lowering to less than 1000’. 

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