Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

Balmy conditions, light rain, and melting will continue to elevate avalanche danger. Cornice fall and other wet avalanche types will continue until there is a sustained drop in temperature. Avoid traveling under cornices, cliffs holding unstable-looking snow features, and glide cracks to lessen the risk of being overrun by an avalanche.

Problemi valanghivi

  • Glide Cracks

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Multiple glide avalanches and cornice failures were noted around the Baker Backcountry on Sunday. [Glide avalanches occur when the entire snowpack is lubricated by water and slides on a smooth ground surface like a rock slab]. A week of warm weather and rain is taking its toll and the mountains are slowly coming unglued. It’s safe to assume this pattern of avalanche activity will continue across the North and Central Cascades until we see a solid refreeze. No new natural wet loose were observed but they should still be considered a hazard in steep terrain.

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

    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 - which is pretty much everywhere. Cornices could also fail under the weight of a person or snowmobile. 

    (3/27/2022)

    Cornice failure and glide avalanche on Huntoon Point on a northeast aspect at 5100'.

     

  • Deep Persistent Slabs

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

    With improved visibility also came a few more reports of deep slab avalanches from across the North Cascades. They are suspected of releasing in a layer of weak, faceted snow buried on March 8th. Some appeared to be triggered by a falling cornice from above. All were naturally triggered. The likelihood is low that a single person could trigger one of these dangerous avalanches as the layer in question is buried 4-6’ deep or deeper. The greater concern is that one releases in alpine terrain above you triggered by a big load like cornice fall or a smaller wet snow avalanche. 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 likelihood of getting hit from above. Traveling in the morning or other times temperatures are cooler will lessen risk but is no guarantee . . . 

    (3/27/2022)

    D3 avalanche suspected of releasing in the March 8th faceted layer. This avalanche was witnessed on the morning of March 23rd.

     

Avalanche Discussion

Look for freshly wind loaded features and shallow slabs anywhere it is cold enough for dry snow to accumulate. Track the depth of new snow as you gain elevation or change aspects. Evaluate the bond of new snow layers before getting into steep terrain with consequences.

The upper snowpack is weak and wet with rain and melt-water having penetrated the upper 100cm.  Sunday night will be the third in a row without a decent freeze - slightly lower freezing levels on Monday will do little firm things up. Skis or other floatation will keep you near the surface, but you will sink shin to knee deep if you get out of your gear. 

Though the bulk of natural 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. Warm temperatures - along with periods of rain - dominated the weather pattern in the last week

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