Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

 

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 to be places where you can trigger an avalanche and minimize time spent exposed to large avalanche paths above you. 

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Heavy snowfall at near freezing temperatures created dense slabs on all aspects. They added an impressive load over the 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 to travel in avalanche terrain. In addition to avalanches in deeper layers, small easy to trigger or even natural storm slabs are likely if you experience periods of intense snowfall with 1" or more of snow is accumulating per hour. Default to lower angle, simpler terrain to reduce risk. Very large human or naturally triggered avalanches that could run long distances are still possible. Err on the side of caution when traveling near or below avalanche terrain. 

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

    Photo: Adam Ü

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–3

    In the southern portion of West Central, intense wind drifting likely occurred Friday afternoon and may continue into early Saturday. This drifted abundant new snow into thick, dense wind slabs near and above treeline. These large slabs could have a hard surface or be obscured by new snow that fell during periods of less wind. Either way, they will be dangerous and destructive if you trigger one, especially if it releases above you. You can identify wind loaded slopes by signs of active wind loading or visual cues like scoured snow surfaces, cornices, and other wind affected features. Avoid all wind loaded areas and stick to ridgelines and low angle terrain if you make it into the alpine on Saturday.

     

    (1/7/2022)

    Intense wind drifting of snow observed on Friday afternoon.

    Photo: Matt Primomo

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 other than in terrain adjacent to roadways or ski areas. Uncertainty is high in regards to the specifics of avalanche activity that would help determine 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 along Highway 2 produced numerous large avalanches to D3.5 that ripped out trees, gouged down through the snowpack, etc.

In the north end of West Central light snowfall will continue through Saturday with snow levels lowering to less than 1000’. Farther south could see more snowfall with a Puget Sound Convergence Zone setting up between Highway 2 and I-90, possibly affecting the Mountian Loop area.

Régions couvertes