Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

The snowpack soaked up significant rainfall and continues to gain strength as rainfall diminishes and temperatures cool. However, you can still trigger a wet avalanche on a steep slope. Snowfall at upper elevations will build drifts that you are most likely to trigger in the lee of ridgelines.

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    The size and distribution of the wet loose avalanche problem has changed significantly over the last 24 hours as cooling temperatures shift our attention to lower elevation. Near treeline, temperatures may hover near or slightly above freezing with a rain/snow mix not contributing further to the problem. A saturated snowpack should gradually gain strength as it drains water and rainfall rates decrease.  The best way to assess your risk is to check your boot penetration. If you sink in past the ankle, reduce your exposure to slopes steeper than 35 degrees, particularly during periods of heavier rain showers.

    Example: Wet loose avalanches entraining saturated snow.

    Photo: Public Observation

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

     Cooling has been slow to arrive at Mt. Hood, but the snow line should gradually descend from Tuesday night and Wednesday. Moderate winds Tuesday night may build thicker drifts above treeline while shallower drifts may form near treeline as snow levels drop on Wednesday. Pay attention for drifts deeper than 6" and assess the slab character above the refreezing crust as you ascend into winterlike conditions. You are most likely to trigger a slab on a wind-loaded unsupported slope steeper than 35 degrees.

    (12/14/2021)

    Example: A small (D1) in Salmon River on a wind-loaded lee slope.

    Photo: Andrew Kiefer

Avalanche Discussion

Since Sunday morning, a significant atmospheric river event brought 3-4" of wet snow followed by rain - 3" of water equivalent. Snow levels fluctuated in the 6500-8000 feet range Monday through Tuesday.  We haven't seen reports of the widespread avalanche cycle at lower elevations. However, a very large (D3) natural avalanche released during the storm on the upper slopes of Mt. Hood into Clark Canyon, with the toe of the avalanche approaching the confluence with Heather Canyon. With cooling temperatures and decreasing winds, we don't expect further natural avalanche from the upper mountain, but you might consider not lingering in valley bottoms for another day out of an abundance of caution. Prior to the storm, NWAC professionals observed 6-18" of snow above a strong (2/19) crust. This snow has settled 10" since Sunday morning and we think it soon be reaching a steady (mostly stabilized) state. A lot of water in the snowpack means rapid change which always adds an element of uncertainty. Approach the terrain with an assessment mindset.

Regardless of whether you're dealing with wet or dry snow problems, avalanches will be most impactful where they push you into a terrain trap or over a cliff. Creeks may have high volumes of water and snow bridges may be few and far between and may impact your route. Low snow remains an issue in some areas: S and W aspects that melted out in early February may have melted out once again.

Régions couvertes