Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
Voir sur la carte

Danger d’avalanche

Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
Open full map
Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Recent very large natural avalanches confirm that dangerous avalanche conditions exist. You can trigger a large avalanche Friday on slopes steeper than 35 degrees where you find wind drifted snow.  Avoid cornices and the slopes directly below them as well as slopes steeper than 35 degrees where windblown snow is accumulating. 

Problèmes avalancheux

  • Wind Slabs

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

    Yet another dose of strong west wind and snow begins Friday night. You will be able to trigger wind slab avalanches large enough to bury or kill you on lee slopes where wind deposited snow is accumulating. Two very large natural wind slab avalanches were observed Friday (details in the discussion below). This kind of bullseye evidence shows that we are primed for dangerous avalanche conditions.

    Travel cautiously sticking to ridges and windward slopes. Look for evidence of wind transport such as firm and textured snow, pillow-like drifts, cornice development, and active blowing snow.  Shooting cracks as you travel are another good indication of unstable snow. Where you see these signs, avoid slopes steeper than 35 degrees with wind drifted snow.

    Clues like this small cornice can indicate that similar aspects are likely to harbor wind slabs which you could trigger.

  • Loose Wet

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

    The snowpack below 5500' has been through quite a few melt and freeze cycles and is generally stable and shallow. Another round of mixed snow and rain at lower elevations arrives Friday night into Saturday.  Small wet loose avalanches will be possible in steep terrain. Pay attention to rising temperatures. Increasing roller balls and pinwheels are an indication the snow surface is weakening. Stick to terrain below 35 degrees if you experience rain or see rollerballs beginning to accumulate snow as they roll. With a firm crust below the surface, even a small wet avalanche may easily entrain more snow and have the power to knock you down. Use extra caution around terrain traps like cliffs and gullies.

    An example of a wet loose avalanche.

Avalanche Discussion

Observers on Friday reported shallow wind slabs had formed, but generally good stability below ~6000'. However, several very large natural avalanches released overnight Thursday at Mt Hood Meadows Ski area in closed NE facing terrain between 6300' and 7500'. These avalanches occurred in wind loaded terrain and had crown heights of several feet up to 6+ feet deep. These very large avalanches slid on the firm rain crust formed on 12/9/20. It is likely that they occurred during a period of intense wind transport on Thursday night.

A very powerful, wet, and warm storm is forecast to impact Mt Hood beginning Saturday night creating very dangerous avalanche conditions. Backcountry travel is not recommended on Sunday.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

Régions couvertes