Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
Voir sur la carte

Danger d’avalanche

Wed
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

Dangerous conditions exist near and above treeline where snow and winds Monday night created fresh, large drifts. Remind yourself about the potential for very large avalanches starting above treeline and reduce your exposure to large avalanche paths and all wind-loaded slopes steeper than 35 degrees. At lower elevations, steer around steep convex rollovers where storm snow or older interfaces may fail.

Problèmes avalancheux

  • Wind Slabs

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

    Westerly winds should be moderate and gusting strong near ridgelines Monday evening and overnight,  which should be plenty strong to transport the fresh snow that falls and load lee slopes. Your primary concern should be navigating around wind-loaded slopes steeper than 35 degrees where these fresh slabs will be primed for trigger and could be large. Secondarily, the slabs could be building atop older slabs that are still reactive, forming very large avalanches above treeline. A very large avalanche (D3 or greater) was reported on the north side of Mt. Hood on Sunday. With this in mind, avoid not only large avalanche paths and start zones, but also steer around avalanche runouts. Wind-loading tends to form under fresh cornices and on the opposite side of ridges from wind-scoured slopes. Cracking of the snow surface or textured snow are warning signs - heed them. If winds pick up Tuesday afternoon and start transporting snow, this active transport can also help you avoid freshly forming slabs.

    (1/4/2021) Cracking snow underfoot on Monday - a classic sign of wind-affected snow and wind slab development.

  • Storm Slabs

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

    You can trigger a storm slab on an unsupported slope steeper than 35 degrees. Fresh storm slabs formed with frontal and post-frontal snow late Monday and Monday night. A crust from Monday that extends to about 5800 ft should provide a bed surface for avalanches to run on depending upon the bond with the new snow. The interface refreezing crust interface may become reactive if 8" or more of snow piles on top of it. Use a pole or probe to check this depth as you travel.  Above 5800 ft, the snow is wind-affected and prone to wind slab rather than storm slab formation. NWAC professionals and a PUBLIC OBSERVATION found a layer that may still be reactive on Tuesday and should be down 15-20 inches, creating the potential for large storm slabs.

    Storm slab example.

Avalanche Discussion

Mt. Hood has received 3.74" of water equivalent in the last 72 hours. This puts us in a major storm cycle. While the weather takes a slight break on Tuesday, don't let that lull you into a false sense of security, particularly at upper elevations.

Fresh cornices are sensitive so give them a wide margin for safety both from above and on the slopes below.

If you plan to travel in the backcountry Tuesday, make a plan that will keep you out of the path of a very large avalanche from higher on the mountain.

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