Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

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

Cold snow avalanche problems build with elevation and throughout the day. Steer clear of lee slopes steeper than 35 degrees if you find cracking snow surfaces or actively blowing and drifting snow.  Water continues to drain the snowpack so limit your exposure to steep or rocky terrain features until a supportable crust forms.

Avalanche problems

  • Wind Slabs

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

    Snow levels will drop quickly Monday night with moderate to strong winds blowing fresh snow into slabs through the day on Tuesday. Slabs will start small and shallow, but will grow throughout the day. Near treeline, the danger will grow rapidly as you move into increasingly exposed terrain. Slabs will be mostly small and we expect you can steer around pockets of instability on lee slopes below ridgelines. However, this may become more difficult as you enter above treeline terrain and as the day wears on. Slabs may grow more widespread at these elevations with occasional larger slabs that would harm you if triggered. Recent rains will have cut back fresh cornices and saturated the upper snowpack up to 9000 ft. Therefore, any dry snow above the refreezing snowpack will be fodder for slab formation. Assess how much snow transport has occurred or is occurring. If you experience high variability of snow depths, rapidly growing cornices, or highly variable depths of dry snow deposits, anticipate reactive slabs on lee slopes nearby and avoid such slopes steeper than 35 degrees.

    (12/21/2022)

    Example: Wind-affected snow near ridgelines can help you anticipate slabs below corniced slopes.

    Photo: Ryan Matz

  • Wet Slabs

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

    A warm system brought 1.25-1.5" of liquid water to the Mt Hood snowpack before the anticipated transition to colder temperatures and snow on Mt Hood. Winds will help form crusts at mid and upper elevations, helping stabilize the snowpack more rapidly. However, at lower elevations, expect the possibility that the snowpack will be slower to refreeze. Wet avalanches could take any of a number of forms from wet slabs lubricated from water running along a crust interface to glide avalanches below steep, rocky cliffs, or wet loose avalanches that you can trigger in wet, sloppy snow. Given the uncertainty associated with the first major warm-up of the season, keep it simple and make sure a firm crust has capped the wet snow in the snowpack before exposing yourself to steep slopes (35 degrees or steeper) of any kind. These avalanches could be natural or human-triggered, so the unstable slopes could be above you.

    (1/14/2023)

    Example: A D2 (large) wet snow avalanche from earlier this winter.

    Photo: Irene Henninger

Avalanche Discussion

The transition from wet snow to dry snow problems can be a challenging one. Wet avalanche instabilities can linger long after the temperature drops below freezing. It's tempting to ignore them, but until a firm crust forms, that would be ill-advised. Meanwhile, wind slabs can form rapidly given the sustained 20-35 mph winds expected through Tuesday. Expect these WSW to load typical start zones and form rapidly increasing danger at upper elevations. We don't know whether these slabs will bond well to the underlying crest, so use small hand pits or test slopes to evaluate the interface. You're likely to find that the optimal combination of good riding conditions and mitigated hazard exists in wind-sheltered areas near treeline. 

On Monday, Mt Hood Meadows patrol found natural avalanche activity up to size 1.5 below treeline, where steep and cliffy terrain was shedding significantly. Observations have been more limited at higher elevations, but snow levels reached 9000 ft for an extended period of time, creating saturated snow at all NWAC forecast elevations.

On Sunday, Joe Dellaporta explored the Lookout Mountain area on a snow machine. At lower elevations, he found a wet and consolidating snowpack. Unsurprisingly, near the ridgetop at 6000 ft, he found a deeper and more layered snowpack. At this elevation, the crust started breaking down by mid-day. It was still supportable on skis, but it wasn’t supportable for their boots and sled.

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