Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Slabs are most likely to remain reactive on colder shaded aspects and where they are thicker at upper elevations.  Smooth or rounded pillows, harder over softer snow, and slopes with sharp cornices all highlight potential instability nearby.  Steer around these problem areas on steep or unsupported slopes where avalanches may still be easy to trigger early in the day.

Avalanche problems

  • Wind Slabs

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

    Slabs were easy to trigger on Wednesday. By Thursday morning they should remain reactive but will be trending toward stubborn by the afternoon. Expect enough solar radiation to get through the clouds to help accelerate the healing process on the southern half of the compass while colder slopes remain hazardous much of the day.  Winds Tuesday-Wednesday arrived from the S and W, loading these same slower-to-heal aspects. Since a crust formed early Tuesday, significantly more snow has fallen around 6500 ft (10-12") than at 5300 ft (7").  You will find a drastic change in conditions as you move upward within the near treeline band, with a significant increase in both average snow depth above the crust and variability of that depth. As you probe and these numbers go up, expect more dangerous conditions in the surrounding terrain. Most slabs will be nearly 24 hours old by the time you head out on Thursday. Don't expect active transport to help you identify problem areas and a few inches of less wind-affected snow near the surface may mask underlying slabs. Use clues such as fresh, sharp wind drifts or fat pillow-like drifts to steer around steep and potentially wind-loaded slopes. Also, check for firm over weak snow layering or poorly bonded interfaces and choose less consequential terrain if you find anything of concern. If you're not sure whether a slope is wind-loaded, then supported slopes less than 35 degrees are your best option.

    (4/11/2023) Example from Snoqualmie Pass: Cracking of the snow surface and small blocks of snow failing on a slightly wind-loaded convexity.

    Photo: Andy Harrington

Avalanche Discussion

The wind slab hazard on Mt Hood ramped up unexpectedly rapidly Wednesday night with cooling temperatures and sustained moderate to strong winds. Mt Hood Meadows reported easy-to-trigger wind slabs near and above treeline with minimal hazard due to less snowfall below treeline. Slabs tend to heal more rapidly in April, but cold temperatures will not help the healing process on shaded aspects. Expect reactive wind slabs to linger longer than you expect. Ease into the terrain on Thursday, started with well-supported terrain features of lower consequence. Although it's mid-April, the surface snow is cold and winter-like and wind slabs deserve to be taken seriously as they may be large.

Thursday should feature mostly cloudy weather. Expect enough solar radiation to filter through the clouds to destabilize recent snow at lower elevations. Rollerballs and snow shedding off trees, rocks, or cliffs all remind you to move to limit your overhead exposure.

An atmospheric river early in the week brought a natural avalanche cycle to below treeline slopes on Mt Hood with widespread D1.5 avalanche activity. 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 during the atmospheric river. The shallow dry fresh snow didn't insulate the saturated snowpack very well once temperatures dropped Monday night, enabling the 4/11 interface to refreeze quickly in exposed terrain with a firm 4/11 crust expected below the mid-week dry snowfall in most terrain by Thursday.

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. Photos in the gallery. After the snowpack absorbed about 1.5" of water early this week, this layered snowpack may be starting to transition and if you head out we'd be interested to hear what you find. 

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