Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Very dangerous avalanche conditions may develop at upper elevations and linger into the early morning hours on Friday. Avoid all avalanche terrain at upper elevations and terrain connected to wind-loaded upper elevation start zones. At lower elevations, steer around open slopes steeper than 35 degrees and unsupported rollovers.

Avalanche problems

  • Wind Slabs

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

    Heavy snow and shifting winds will peak Thursday night with the potential for natural avalanche activity, particularly at upper elevations and early in the day. The snow keeps coming at Mt. Hood and the recent snow hasn't had time to consolidate, so we're expecting drifted snow to be highly reactive. Friday is a day to avoid all upper-elevation slopes and terrain connected to those slopes even if it below treeline. These slabs could be pushing the very large size range in particularly wind-loaded locations.

    Near treeline, reactive slabs will continue to form with moderate to strong SE winds shifting to the WSW early Friday. This wind shift may make it challenging to identify wind slabs. Keep it simple on Friday and avoid any potentially wind-loaded slopes steeper than 35 degrees. Signs of wind loading could include active transport, firmer over weaker snow, cracking snow surfaces, or sensitive cornices that break as you walk past. We've had reports of multiple such cornices on Thursday and although propagation on the slopes below was limited, that could change by Friday.

    Example: A large avalanche with 3-4 ft crown near a wind-loaded ridgeline. A-zone. Mt Hood Meadows.

    Photo: Mt Hood Meadows Patrol

  • Storm Slabs

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

    13" inches of snow has fallen in the last 15 hours and we're expecting another foot or more by the end of the day on Friday. High snowfall rates such as these will form widespread soft slabs. They may or may not maintain cohesion and propagate widely, but given the amount of snow, make no mistake they could ruin your day or worse. Storm slabs will be most reactive during and shortly after periods of heavy snowfall. We expect this reactivity to peak early Friday and gradually decrease as the day progresses. Therefore, gradually ease into the terrain, choosing supported features, less consequential features all the while avoiding larger open slopes 35 degrees and steeper.

    On Wednesday observers reported a widely propagating natural avalanche that broke 1-2 feet deep and reactive storm snow. We have limited information on the distribution of this weak layer responsible for this naturally occurring avalanche. What we do know is we had isolated pockets of surface hoar form around 3/1. As the next storm arrived, winds destroyed this surface hoar in most exposed terrain, but it may remain buried intact in isolated locations.The distribution of this layer remains uncertain.

     A snowpack test can help you evaluate the instabilities within the top 2-3 ft of the snowpack. 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 on Friday.

     

    (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

Uncertainty about the 3/2 interface, heavy snowfall, and efficient wind transport will make Friday a challenging day to stay safe in the mountains. A deep snow rescue on the slopes of Mt Hood Wednesday night confirms the need to maintain visual contact with your partner and keep Snow Immersion Suffocation in mind. 

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.

On Wednesday we received a report of a surprising natural avalanche that propagated widely (N aspect, 5400 ft) in the Bennet Pass area. The observer reported crown depths ranging from 1-2’ ft deep and characterized it as a D2. By Friday, this layer might be 2-3 ft down or more, increasing the potential scale of any avalanche triggered on this layer. The grains involved with the failure layer are unknown, but appear persistent-like and likely involving the 3/2 interface.  Earlier on Wednesday, an avalanche class in the Vista Ridge area also reported finding a couple of notable layers of concern, including buried surface hoar that sits 12-15 inches below the snow surface and produced planar results with shovel tilt tests. We're operating on the assumption that we may have a weak layer (possibly buried surface hoar) and we suspect it has an isolated distribution in wind-sheltered areas.

Continue to let the storm play out and make conservative terrain choices on Friday.

If you get out into the mountains, let us know what you see by submitting a public observation. 

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