Bulletin d’avalanche

Stevens Pass

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You may be able to trigger avalanches on steep slopes near and above treeline where westerly winds may have formed drifts on Saturday. Both poor visibility and light snow could make it difficult to assess slopes at upper elevations. Stick to wind-sheltered terrain and areas where you can more easily assess the snowpack.

Problèmes avalancheux

  • Wind Slabs

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

    You may be able to trigger avalanches on leeward slopes 35 degrees and steeper. Use caution or consider avoiding wind-loaded slopes. Steer around convex rolls, thicker pillows of snow, and slopes with drifted wind features. Consider the consequences of avalanches breaking widely across a slope. Aside from distant avalanche observations that include wide crowns, we have little information about the near and above treeline elevations. Approach the upper elevations with an assessment mindset.  

    Winds (SW-NW) formed slabs over the course of an intense storm on the 18th. While avalanches occurred at all elevations and on leeward as well as wind-sheltered slopes, the concern remains where wind slabs may have formed. Both poor visibility and recent snow (covering the drifts) could make it more difficult to assess the wind-loading patterns and identify slopes of concern.

    (12/19/2021)

    A crown from an avalanche (size D2) that ran on 12/18 in storm snow. Above treeline, SE, Mt Mastiff

    Photo: Matt Primomo

Avalanche Discussion

On Sunday, observers reported that the 15" of recent storm snow was becoming difficult to trigger in wind-sheltered terrain and at low elevations. Observers reported a widespread cycle of avalanches, up to size D2.5, that occurred on Saturday, the 18th. Fluctuating temperatures created up to two crusts at the beginning and towards the 2nd half of the storm.

The best that we know from limited information, the two crusts deeper in the snowpack (December 8th and early December) were not involved with the recent avalanche cycle. While they are quickly becoming less of a concern in this zone, it's worth checking them out if you're going to upper elevations or further east in the zone. Observations are still limited. In Canada, the early December crust has been responsible for numerous large and surprising avalanches. 

Régions couvertes