Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

Don’t let your guard down as you change aspects above 6000 ft on Friday. Strong winds from multiple directions have built firm slabs of wind-drifted snow all over the compass. Time your travel to avoid steep, sunny slopes during the heat of the day.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2.5

    Unusual loading leads to unusual avalanches. East winds have been cranking for over 24 hours now and will continue to drift snow through the day Friday. Most of this snow is deposited along west aspects, but slabs may also exist in different spots than you may anticipate. Give yourself wider margins as you travel from aspect to aspect.

    Look for blowing snow and rippled, textured drifts as you move through the terrain. Keep in mind that a small wind slab could have significant consequences in steeper, upper mountain terrain. High winds have pressed these slabs into firmer (1F/P hard) deposits. These hard slabs are often more stubborn and may sound hollow but could break surprisingly wide across terrain features if triggered. Solar radiation and warming could contribute to increased reactivity during the later day hours.

    Your best bet will be to avoid terrain actively loading up and steer around smooth, hollow pockets of snow. 

    (3/13/2024)

    Looking up at a widely propagating explosive triggered avalanche in a heavily wind loaded area at Mt Hood Meadows.

    Crown depths ranged 3-5 ft deep. 

    HS-AE-R3-D2.5-U on NE at 6200ft

    Photo: MHM Pro Patrol

  • Loose Wet

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

    We’re entering the first warm-up of the season, so look for wet avalanches on any slope that receives direct sun. As temperatures climb, we may start seeing increased activity on more shaded aspects (N-E). The most common type of wet avalanches will be the fan-shaped wet loose avalanches, but we can't totally eliminate the idea of larger, wet slabs as temperatures rise. Wet slabs are notoriously hard to forecast and manage, but it is worth keeping in mind in areas that hold soft, sloppy, wet snow. Pinwheels and rollerballs shedding on a slope indicate the snow surface is softening, and loose snow avalanches may soon follow. If you're finding wet, mushy snow on the snow surface, it is a good time to think about heading for home or moving to more shaded aspects. 

    An example of a small wet loose avalanche that was triggered by a tree bomb. 

    Photo: Kaitlin Harrigan

Avalanche Discussion

If you were out on Thursday, you probably expected a balmy, warm day but instead observed strong east winds that kept snow surfaces cold and textured at upper elevations. This trend will likely continue on Friday, with strong wind battling the warm temperatures. 

On Wednesday, the Mt Hood Meadows Pro Patrol reported triggering a few large avalanches with explosives. These firm wind slabs released in loaded terrain on E-NE aspects. One avalanche on a NE aspect at 6200ft, broke 3-6 ft deep and propagated over 200 ft wide. We’re unsure what this avalanche failed on, but the wide propagation is notable. 

The Cascades are heading into a stretch of very warm sunny weather. It will be the first big, spring-like warming event of the year, with high temperatures in the 50's and freezing levels over 10,000'. Very warm conditions through the weekend could produce significant slab and loose snow avalanches. 

As with any warming event, there is a high level of uncertainty as to where, when, or even if this scale of avalanche activity will occur. On the other hand, big natural avalanches aren't really the kinds of things that should be taken lightly. It's worth noting that smaller wet loose or wind slab avalanches, cornice falls, or snow shedding from cliffs can provide the trigger needed to pull out a very large avalanche. When planning for the weekend, consider that this is one of the times when an 'improbable' avalanche might actually occur.

If you head out, let us know what you find by submitting a public observation here! 

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