Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Continued above freezing temperatures, periods of rain and saturated snow maintain danger from wet avalanches. Though the frequency of wet loose and slab avalanches is decreasing, they continue to occur. Reduce your exposure to steep terrain overhead, especially on northerly aspects near and above treeline.   

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    An upper snowpack of deep, dry snow plus rising temperatures and periods of rain produced numerous avalanches in the last week. Though past the peak of activity, we will continue to see occasional wet loose and slab avalanches until there is a sustained drop in temperature. A few cornices have fallen so far and many are sagging and looking unstable after days of mild temperatures. Glide avalanches where the entire snowpack slides on a smooth ground surface (i.e. rock slab) are also possible. A few inches of snow through Saturday morning might make for another round of rollerballs and small wet loose avalanches as the day warms.

    Human triggered avalanches have been far and few between but that probably has more to do with poor ski and riding conditions than stability. It’s still possible to trigger a wet loose avalanche in very steep terrain holding saturated, unconsolidated snow. Cornices could also fail under the weight of a person as well.

    The best policy might be to just avoid being on or directly under steep terrain, especially during rainfall or periods of sun. The same advice holds true when the snow surface is wet and unsupportable. Though plenty of avalanche terrain presents low risk, it’s difficult to predict which slopes will fire-off avalanches or other hazards onto anyone below. Expect more of the same until the mountains get a good freeze.

    Multiple large wet loose avalanches initiated from alpine terrain on Tuesday, March 22nd. Northwest aspect of Mt. Shuksan. 

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    3

    A layer of weak, faceted snow buried on March 8th was the root cause of a very, very large natural avalanche that occurred on Wednesday morning - in addition to three others the previous week. There is a slim chance you could trigger one of these monsters as the layer in question is buried around 4-6’ deep. The greater concern is that one releases in alpine terrain above you triggered by cornice fall, a smaller wet snow avalanche, or for some other reason. Though all known avalanches of this type initiated near or above 5500', some traveled far down into treeline. 

    As with the wet avalanche concerns listed above, there isn’t really much you can do to outmaneuver this problem. You are either in the terrain where one of these avalanches might occur, or you are not. If you choose to travel in these areas your a simply accepting a slightly higher risk of triggering or being exposed to this problem. 

    (3/23/2022) A very large natural avalanche which occurred early Wednesday morning on the Shuksan Arm. Possibly up to a 5' crown. Photo: Kris Stemmler

Avalanche Discussion

Observers on Friday found a boot supportable, nearly frozen snow surface at mid-elevations with “corn-like” skiing late-morning. Unfortunately, warm conditions ate away at the surface crust and gloppy conditions returned by midday. No new avalanches were reported except for a few skier triggered D1 wet loose in steep terrain. Thursday brought a report of another large slab avalanche near Ptarmigan Ridge in the Baker Backcountry. It was likely triggered by cornice fall from the ridgeline above. It is not known for certain if it failed in the layer of facets or at a higher interface, or if the slab was wet and saturated. 

From March 13th to 21st Heather Meadows received steady precipitation at near freezing temperatures. Though some fell as rain most came as snow with over 5' of new snow recorded. In addition to storm and wind slab avalanches, three very large slab avalanches were reported on March 16th- two natural and one from avalanche control work. All three were suspected of releasing in the layer of facets buried on March 8th. On the 21st a rapid rise in freezing levels and periods of rainfall laid waste to the powder bounty with wet, gloppy snow conditions and wet loose avalanche activity reaching well into the alpine.

Regioni coperte