Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Another cold storm brought 1.5-2 ft of snow to Mt Hood since early Thursday. The weather may relent but dangerous avalanche conditions will linger, so ease into simple terrain and lower consequence features. Slabs or wet loose avalanches could be large on steep, open slopes and in the lee of upper elevation ridgelines.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    Moderate WSW Friday night into Saturday morning will continue to move large amounts of low-density snow. Slabs will be reactive in wind-loaded areas, particularly during and just after periods of stronger wind transport. While we're focused on recent slab formation on typical aspects, SE winds earlier in the storm created very large slabs that released naturally on Mt. St. Helens. Similar slab formation conditions on Mt Hood suggest that isolated very large avalanches may lurk, but would be stubborn to trigger. Wind slabs tend to be longer lived than other slab avalanche problems, so don't let your guard down after the winds calm down. As the visibility improves, start to note visual clues such as textured snow, lens-shaped pillows, and fresh, sharp, and very sensitive cornices that point toward reactive slabs on the slopes below. Challenging uphill travel often means that you have a denser slab atop lower-density layers. Propagating cracks and significant settlement serve as reminders to avoid wind-loaded slopes above treeline. Avalanches will increase in size with more widespread potential for large avalanches and isolated very large avalanches above treeline.

    (3/10/2023)

    Crowns spotted by scientists for the USGS in the neighboring WS zone at Mount St. Helens. These avalanches likely occurred overnight on 3/9 during the height of the storm. 

    Photo: Wes Thelen

  • Storm Slabs

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

    18" of snow has fallen since the storm began early Thursday and we're expecting storm totals in the 20-24" range by Friday. Slabs may be large, entraining significant volumes of snow. With cold temperatures, most slabs will not propagate widely or may just run as a dry loose avalanche, but the shear volume of snow will make them large enough to bury or kill you. Steer around open slopes steeper than 35 degrees and choose slopes that don't roll out of sight below you.  See the discussion for more information about the potential for an isolated avalanche failing around 3 ft down on the 3/20 interface.

    Lastly, the sun may make an appearance and if it does, W-S-E aspects will start shedding snow. Wet loose avalanches could entrain significant snow and become large on slopes steeper than 35 degrees. Reduce your exposure to steep slopes receiving strong march sunshine

     

    (3/8/2023)

    This natural avalanche occured Wednesday on a North aspect @ 5400 ft in the Bennet Pass area. Crown depths ranged from 1-2' deep. 

    Photo: Trevor Wright

Avalanche Discussion

It's worth a dig in the snow to evaluate mid-storm instabilities, but while you're at it you might as well dig to the 3/2 interface.  On Wednesday observers reported a widely propagating natural avalanche that broke 1-2 feet deep (N aspect, 5400 ft) and we suspect it failed on weak snow grains or surface hoar.  With 40" of snow accumulating atop this interface, it may be down around 2.5-3 ft on Friday and you're most likely to find it in sheltered, open slopes below treeline. Persistent grains don't heal quickly and may remain sensitive to human trigger long after the storm. While it may help you identify a thin gray line (surface hoar) 1-3 ft down in the upper snowpack you would be wise to keep your terrain selection simple and slope angle moderate given the uncertainty surrounding this layer.

Several observations point toward continued Snow Immersion Suffocation and Treewell Safety hazards as the snow continues to pile up. It's deep out there. 

Sensitive cornices should also be on your mind as low-density snow continues to form cantilevers that will break upon approach. If wind slabs become more reactive than on Thursday, cornice fall may be a concern both on the slopes above you and as you travel along the ridgelines.

Information has been limited at Mt. Hood for the past several days during the storm. If you get out into the mountains, let us know what you see by submitting a public observation.

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