Bulletin d’avalanche

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

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

Points saillants

It is possible to trigger a large wet loose avalanche and small natural avalanches are likely. Slopes where the surface snow is soft will be the fastest to weaken today. If you’re trenching up to your boot tops or your sled is struggling to wallow through the wet slop - move to shadier slopes or simply call it a day.

Problèmes avalancheux

  • Loose Wet

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

    Wet loose avalanches are likely on steep solar slopes and slopes holding unconsolidated snow. Direct sunshine, warm temperatures and minimal wind are expected to cause natural avalanche activity, especially in areas that haven't been baked the past couple of days. Slopes where the surface snow is soft will be the fastest to weaken today. These slides often initiate near the base of trees, rocks and cliffs, starting small then gathering snow and growing in size as they move downhill.

    Rollerballs, pinwheels, and trenchy trail-breaking are bullseye observations signalling that the snow is heating up, and wet avalanches may soon follow. Even small slides can be consequential above terrain traps such as gullies, creeks, and thick timber. Plan your day to avoid lingering under big avalanche paths longer than needed.

    Today's warm temperatures and sun may also cause cornices to fail and entrain snow as they tumble downhill. Stay out from underneath large, sagging cornices and give them a wide berth along ridgelines because they can peel back much further than you expect.

  • Wet Slabs

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

    Large wet slab avalanches are most likely at mid and upper elevations, where the snowpack is relatively shallow and has preserved weak layers. As the snow surface breaks-down due to daytime heating, avoid travelling through and under avalanche paths with cliffs or rock outcroppings near the start zones. These rocky features often accelerate snow melt and can pump water deeper into the snowpack quickly.

    As melt water infiltrates further into the snowpack, it can weaken previously buried weak layers until they fail. We have a variety of facet and crust + facet combinations weak layers buried in the snowpack that could result in large slab avalanches if pushed over their tipping point. These lingering weak layers display varying results in stability tests, but seem to be most prominent above 8000' on slopes facing E-NE-N-NW.

Avalanche Discussion

One of the golden rules of avalanches is that the snowpack doesn't like rapid change. Change comes in many forms, but we're focused on rapid heating for the next couple of days. Although the snowpack throughout our forecast region has seen a couple of significant warm-ups already this season (ex: late January and late February), this one is the hottest. We've also had fairly consistent snowfall after each of these warm-ups, resupplying cold snow-ammunition for wet snow avalanches. The inherent challenge of rapid-warming driven changes is that they tend to be quite spatially variable. This means that it doesn't affect all slopes, aspects, or elevations uniformly. Subtle differences in terrain orientation, amounts of wind, and cloud cover can make or break individual pieces of slopes reaching a critical avalanche threshold due to melt water infiltration. Therefore, forecasting for this tipping point across individual slopes, let alone an entire forecast region, require an acceptance of a sizable amount of uncertainty.

So why am I rambling on about uncertainty with wet snow and a changing snowpack? Because incorporating this uncertainty into my recipe for a fun day in the mountains, by giving myself a variety of terrain options, is key to success right now. Where the snowpack is deeper and where the wind built solid surfaces, wet avalanche concerns will be slower to peak. In shallow snowpacks and where unconsolidated snow remains, wet snow problems will escalate more quickly. If you’re trenching up to your boot tops or your sled is struggling to wallow through the wet slop - move to shadier slopes or simply call it a day. If you're still sniffing out cold dry snow on upper elevation shaded slopes, be aware that there is a small chance you could find lingering wind slabs. Triggering one of these avalanches is unlikely, but not out of the question given the rapid change the snowpack is going through right now.

Régions couvertes