Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

Light rain and rising freezing levels will continue the pattern of sporadic wet avalanche activity. Reduce your exposure to cornices and very 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

    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 a week of mild weather. Glide avalanches where the entire snowpack slides on a smooth ground surface (i.e. rock slab) are also possible. Though most avalanches in the last week were “naturals” it’s still possible for a person to trigger a wet loose in very steep terrain holding saturated, unconsolidated snow. Cornices could also fail under the weight of a person or snowmobile. 

    The easiest way to reduce risk is to simply avoid traveling on or directly under very steep slopes, especially during rainfall or periods of sun. The same advice holds true when the snow surface is wet and unsupportable. Give cornices, glide cracks, and steep, rocky areas still holding snow a wide berth as well. Avalanche activity is less likely when a thick, melt-freeze crust is present at the snow surface.

    (3/22/2022) Wet loose avalanche at the toe of the East Gully of Herman. 

  • 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. This large slab avalanche might also have run on the layer in question. 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

Look for freshly wind loaded features and shallow slabs anywhere it was cold enough for dry snow to accumulate. This is most likely on the highest peaks and heading east towards the Cascade Crest.

On Saturday few inches of new snow near treeline reportedly did little to influence avalanche danger. The biggest upshot was a period of cold temperatures that reduced the likelihood of a larger avalanche or cornice fall. Dry new snow was noted above treeline but will quickly fall victim to 6000-7000’ freezing levels Sunday.

Despite a lack of reported avalanche activity in the last 48 hours, the current snowpack is still wet, weak, and generally unstable and manky. Periods of colder temperatures have limited avalanche danger the last few days. A boot supportable crust with quasi corn conditions at mid and upper elevations was reported on Friday. Though the bulk of wet loose avalanche activity has run its course, overhead hazard with the “spring shed” continues. Plenty of avalanche terrain presents low risk, but it can be difficult to predict which slopes will or won’t produce avalanches or other hazards until the mountains get a good freeze and stop slowly falling apart.

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.

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