Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

Heavy snow combined with strong to extreme winds will create very dangerous conditions. Avoid all avalanche terrain at middle and upper elevations or where very large avalanches could descend to lower elevations and valley bottoms. Stick to densely forested slopes and non-avalanche terrain.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2–3

    Mt Hood is in the cross-hairs of an intense mid-winter atmospheric river.  Very strong winds will drift 12-18" of new (along with 3-6" of recent) snow into slabs that could be 3-5 ft thick, creating very large slabs on wind-loaded middle and upper elevations slopes. These slabs will fail under their own weight as they load up, creating natural avalanches that could be large enough to destroy a house. Such an avalanche would be unsurvable.  A rider would also easily trigger them. Slabs could be in the typical start zones or wind-loading patterns may distribute them well down into the avalanche path. At lower elevations, you can also easily trigger a large avalanche on a steep, open slope, but very large avalanches would only be a risk from start zones at higher elevations. 

    (3/16/2022)

    Very large avalanches like this one may fail without waring on wind-loaded lee slopes as 

    Photo: MHM Pro Patrol

  • Storm Slabs

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

    Storm snow will be falling faster than it consolidates. This will create the potential for widespread easily triggered avalanches on slopes steeper than 35 degrees and the potential for natural failures as well. While these avalanches won't be as large as the wind slabs, they should keep you off of any slopes steer than 35 degrees where slabs will initiate easily and will run efficiently on the 12/22 crust. 

    Example: Storm slab on a steep slope.

    Photo: Adam Butterfield

Avalanche Discussion

You may be tempted to try your new Christmas gear on Thursday, it's not the day to engage with avalanche terrain. Heavy snowfall along with strong to extreme winds will peak overnight into the morning hours before gradually easing during the afternoon. Slabs will continue to build throughout the day, so expect the potential for very large avalanches off the upper elevation slopes to continue until the day's end. We're not sure when avalanche activity will peak, but most likely during or shortly after the heaviest snow and wind loading in the morning hours.

3-6" of mildly redistributed 10% density snow sits on the 12/24 crust as of 4 PM on Christmas Day. Most of this new snow arrived Wednesday afternoon, but a small amount glued into the 12/24 crust as it fell on Wednesday. Above 7000 ft, the 12/24 crust fades away and the first crust you'll find is the stout solstice crust. This crust was created following a rain event up to high-elevations on December 17th that resulted in a widespread avalanche cycle up to D3.  Photos in the gallery show conditions prior to the recent storm cycle, but avalanches of a similar magnitude will be on the menu once again on Thursday.

 Mt Hood Meadows reported loose dry avalanches on Wednesday. But don't let talk of lower-density snow fool you. This snow will serve as an effective weakness above a bed surface (crust) as denser snow falls with rising temperatures and denser slabs over-ride the lower-density snow in the form of wind drifts.

Régions couvertes