Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

Wed
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Don't let the improving snow conditions lure you onto bigger slopes while winds and snow continue to produce natural avalanches at upper elevations. Avoid all travel above treeline. Elsewhere, travel safely on slopes less than 35 degrees that lack exposure to upper elevation avalanche start zones.

Problèmes avalancheux

  • Wind Slabs

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

    Relentless winds continue to efficiently transport lower-density snow onto lee slopes near and above treeline, continuing to stress upper elevation slabs to the breaking point. Winds at 6500 ft have generally been above 20 mph since Saturday morning and won't ease much through Tuesday. Widespread natural avalanches are expected to continue above treeline. Windward slopes may be scoured to a crust while lee slopes will produce avalanches that may be very large above treeline. Some of these avalanches could travel long distances into lower angled terrain, below-treeline elevations, and valley bottoms. Avoid all avalanche terrain linked to upper-elevation start zones. Stick to windward slopes, low-angle leeward slopes, and ridgelines if you travel near treeline, avoiding open areas where avalanches may reach from above.

    (4/10/2019) This very large wind slab avalanche in April 2019 gauged deeply and ran into significantly lower elevation terrain. Note the stunted trees and open terrain in the photo and avoid similar terrain on Sunday.

  • Storm Slabs

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

    Fresh storm instabilities will build above a refreezing rain crust, a slick freezing rain crust, or without a notable interface above around 6000 ft. In areas above the 2/22 crust, these slabs may be large. Instabilities within the recent snow will be slower to heal as temperatures cool significantly through Tuesday.  Instability will be greatest during and just after periods of intense snow showers. Avoid all slopes steeper than 35 degrees where you find 8" of recent snow that you can easily trigger a slab. Use small test slopes and miniature rollovers to assess the potential for slabs to propagate. You are also likely to trigger a dry loose avalanche on slopes approaching 40 degrees given the increasingly low-density snowfall. Any avalanches could run faster and more efficiently where they run on the freezing rain crust.

    (2/13/2021) This widely propagating storm slab occurred Saturday at Bennett Pass.

Avalanche Discussion

Heavy rain at lower elevation transitions quickly transitions to all snow from Monday evening onwards. Snow showers should continue through Tuesday with 6-10" of increasingly lower density snow expected to accumulate. Strong W winds should continue to load snow onto the same mid and upper-elevation slopes that have been experiencing wind/snow loading throughout the storm cycle.

Monday night Mt. Hood transitions to the cooling phase of a 13-day storm and avalanche cycle.  Sunday night and Monday, rain or freezing rain ascended to at least 6000 ft. The freezing rain event at Mt. Hood Meadows was significant and likely represents the "new ground" for avalanche activity and a bed surface for new snow avalanches in areas where it exists. Mt. Hood has picked up over 90" of snow since Thursday the 11th when the storm cycle began! The snowpack has increased by about 50" as it settles with higher settlement rates since the warm-up Sunday night. A widespread avalanche cycle occurred Saturday and another on Monday/Tuesday. On Sunday, the scales likely tipped once again with reactive snow reported by Mt. Hood Meadows Pro patrol below treeline. Natural avalanche activity was likely occurring in the near and above treeline bands on Monday.  The sustained poor visibility over the last several days limits our ability to confirm upper elevation avalanche cycles, which in turn creates uncertainty in our forecasts. If you see something that diverges significantly from the forecast, dial back your terrain selection further and consider avoiding all avalanche terrain.

 

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