Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 8 months ago. You’re viewing past conditions, not the current bulletin.

Highlights

Slabs could be large, easy to trigger, and propagate more widely than you expect, particularly where they form above a slick crust at upper elevations. Monitor the new snow depth as you ascend and avoid steep wind-loaded terrain once the average snow depth exceeds 3". 

Avalanche problems

  • Wind Slabs

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

    Moderate SW and WSW winds will form slabs above the rain/snow line. The problem at the highest elevations initially, but as snow levels lower from 8000 ft Thursday evening to 6500 ft by Friday afternoon, slabs will grow larger, more widespread, and easier to trigger.  If you find that it's a rain/snow mix at 6500 ft, there could be significantly higher hazard above 7500 or 8000 ft. Therefore, your first order of business as you ascend is to pay attention to any avalanche paths that may be wind loading above. As you move into accumulating snow, check how the new snow is bonding to the crust...the slicker the crust, the more likely you are to find reactive and propagating slabs with enough loading. Once you find 3" of average snow depth, or wind loaded test slopes 6" or deeper, simply avoid steep wind-loaded terrain. Shooting cracks, significant snow transport, or punchy layering all confirm that the problem is likely to be widespread in your terrain.

    Example: Reactive wind loaded slabs.

    Photo: Joe Dellaporta

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Elevations up to 7500 ft on Mt Hood experienced up to 0.75" of liquid rainfall on Thursday, with similar amounts expected Thursday night through Friday. While we think the snow has been beaten down by wind, rain, etc., you could still find wet snow you can sink into up to your ankle, where you could trigger a wet avalanche on a steep slope 35 degrees or steeper. These mostly small wet avalanches could occur naturally as well.

    If you might be exposed to larger terrain features, it would be a good idea to dig down to the 12/24 crust first and make sure that water is not pooling on that interface. This setup for wet slab is not our base case, but dial back your terrain selection if you see it would result in a more widely propagating and more dangerous wet slab.

    (3/13/2022)

    Example: A small loose wet avalanche in previously dry snow.

    Photo: Ron Martin

Avalanche Discussion

The conditions on Mt Hood will diverge drastically depending on your elevation on Friday. It's full on winter at upper elevations and above NWAC forecast zones, while the snowpack is taking on water at lower and middle elevations. 

Temperatures have been unseasonably mild on Mt Hood with temperatures reaching the 40s multiple days running. Thursday brought 0.75" of rain up to 7500 ft. The rain or freezing rain that fell above 6600 ft formed a new crust. Below this crust you may find a layer of wet or dry snow, sitting above the 12/24 crust.

Mt Hood pro patrol triggered large slabs following a snow and extreme winds from 12/26-12/27 which formed firm slab overlying faceted snow above the 12/24 crust. The faceted snow has been healing and is unlikely to be a concern moving forward.

Despite recent accumulations, the snowpack remains thin by late December standards and snow depths increase markedly above 6,000 ft. Keep an eye out for shallow coverage down low, scoured west-facing aspects, or thinly bridged crevasses in alpine terrain. 

 

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