Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

You can trigger a large wind slab that may be well below typical start zones. Use a probe to check for firm or punchy layers and be suspicious of softer snow that has been transported by the wind. Minimize your exposure to avalanches by navigating around terrain features and start zones over 35 degrees. 

Problèmes avalancheux

  • Wind Slabs

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

    Strong winds will continue to build large slabs that you can trigger, particularly near and above treeline. Around 4-5" of fresh snow with cooling temperatures will add ammunition for the winds to load lee slopes.  Typical start zones may be wind-swept, but other areas will have wind deposits, potentially far down the slope.  Wind slabs are likely to be large and firm, making them difficult to escape because they break widely across a terrain feature, while soft snow may have an upside-down layering structure making it easier to trigger. Seek wind-sheltered terrain where possible. Pay attention to cracking snow surfaces and firm, punchy layering. Treat active snow transport and wind-loading as warning signs. Avoid wind-loaded slopes steeper than 35 degrees, especially midslope convexities,  and shallow ridges.

    Below treeline, slabs may be smaller, softer, and easier to steer around. Steer around lens-shaped pockets where you can trigger an avalanche on slopes steeper than 35 degrees.

     

    Example: Wind slab and active wind transport onto the slope.

Avalanche Discussion

On Saturday, NWAC forecast Peter Moore was near Timberline. Slabs 4-6" deep became reactive with warming temperatures. Strong wind transport was also reported from Bennett pass and Newton Canyon.  Mt. Hood meadows reported a ground blizzard above treeline with very isolated pockets of softer snow (1-2" ski penetration) near treeline. 

Eastern slopes and higher elevations warmed significantly Friday. Recent strong winds have stripped snow off many aspects by Saturday exposing "mist" or temperature crusts formed Friday on S aspects up to 7000 ft. An observation from Newton Canyon found this surface crust even on NE aspects below 6000 ft.

The stout mid-January crust is considered the new "ground" with a strong snowpack structure in place below this layer. Weak and faceted snow just above the stout rain crust was responsible for a number of avalanches last week, but no new evidence of avalanches on this interface suggests these facets are gaining strength. 

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.

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