Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Wind slabs are expected to maintain reactivity above treeline while near and below treeline less dense layers continue to adjust to denser snowfall from Sunday onwards. Continue to monitor the snow for signs of instability such as cracking, settlement, or layers of weakness. As you ascend in the terrain, make note of where fresh snow transport is forming slabs and where firm, punchy snow lingers then avoid steeper slopes nearby.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Fresh winds in the moderate range combined with light snowfall will add to slab formation, particularly late Sunday night into Monday morning. You can trigger a wind slab above the treeline and it may be large on Monday. As winds change from SSW to W, pay attention to new wind loading patterns, but recognize that older wind-loaded slopes may still be reactive. When in doubt, avoid poorly supported slopes in all areas where you find wind-affected snow steeper than 35 degrees.  Natural wind slab avalanche activity was observed above 7500 ft on Mt. Hood when the skies cleared on Sunday. Widely propagating cracks were reported at these elevation bands on Saturday. We think that some of these slabs extend into elevations we forecast for. Remember that wind slabs can linger for up to 5 days and recent wind slabs are 4 days old or less.

    (12/12/2020) Example: wind slab on a steep wind-loaded slope. If you find styrofoam-like or punchy snow, head for lower-angle terrain.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Temperatures warmed significantly on Sunday, which combined with 5" of dense snow to create an unstable formation of denser over less dense layering. There just wasn't enough new snow or a sufficient weak layer to create much avalanche activity on Sunday. We expect a similar setup on Monday with a few more inches of snow on top and the low-density snow above the crust still adjusting to the load. We still think the slab structure has the potential to be dangerous with a critical load or rapid load of snowfall (which we do not expect with the current weather forecast). The challenge is that although we think the slabs are beginning to heal, if they do break, they could be large and dangerous.  Consider jumping on representative steep, unsupported test slopes nearby that are not large enough to harm you. Use the information you glean to make an informed decision before committing to larger terrain features if they are steeper than 35 degrees. Remember that supported (concave) slopes are less likely to slide.

     

     

Avalanche Discussion

On Sunday, Mt Hood saw milder temperatures with 5" of denser snow falling on top of  9" of 8.6% density fluff falling late Thursday into Thursday evening.  Warming mid-day on Sunday created roller-ball activity and moistened the upper snowpack slightly. Observers on Sunday reported limited signs of instability in spite of a poor density structure. 

Thursday and Friday saw the first snowfall since a rain crust created a "new ground" and limits avalanche concerns to the more recent snow.

Maintain awareness of objective hazards below you such as rocks, trees, or cliffs.

Regions covered