Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

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

You can easily trigger a large and sensitive slab on any wind-loaded slope steeper than 35 degrees. The danger will be coming down from HIGH in the early morning hours, so Monday will be a good day to ease slowly into lower-angle terrain and smaller-scale features.  The potential for very large natural avalanches originating on the upper mountain should keep you out from under terrain connected to large avalanche slopes until winds relent.

Avalanche problems

  • Wind Slabs

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

    Wind slabs were very reactive on Sunday with extreme WSW winds accompanying 14" of snow that fell by the end of the day. By 1 PM on Sunday, Mt Hood Meadows Patrol reported very sensitive slabs breaking 6-18" on skier trigger and in some cases sympathetically. Observers on Pea Gravel Ridge also reported growing sensitive wind slabs becoming large by the afternoon. Slabs will be larger (up to size 2.5) and more dangerous, but not quite as sensitive on Monday with heavy snow continuing into Sunday evening and strong winds transporting additional snow. Expect to find firm, hard slabs above treeline with softer slabs forming slabs over less consolidated storm snow near and below treeline.  Use visual clues such as active wind transport and fresh, sharp cornices or mound-shaped pillows of snow on a slope to identify wind loading. Monday will not be a good day to move onto any steep (greater than 35 degree) wind-loaded terrain or terrain connected to larger wind-loaded features. The size of the slabs has us concerned as does the potential for continued wind loading above treeline and particularly above NWAC forecast elevations. Pay particular attention as you approach the steep slopes of the volcano proper: With plenty of snow to transport and continued strong winds, expect a chance for very large avalanches to descend the upper mountain. However, we don't expect these to run very far if they make it to valley flats.

    Example: Large wind slabs that you could trigger on steep, wind-loaded terrain on Monday.

    Photo: Mt Hood Meadows Pro Patrol

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1.5

    By Monday morning, storm slabs will be up to 18" deep in sheltered near and below treeline terrain above the 4000 ft rain/snow line. These slabs will be most reactive at the beginning of the day when you can expect widespread storm slab activity. These slabs will likely run on mid-storm instabilities created by high snowfall rates. They could also run on the 2/4 interface (old/new snow or melt-freeze crust on steep S aspects). In either case, take advantage of small-scall steep features to test the slope, noting the storm slab potential for propagation. Simple column tests within the top 2 ft of the snowpack could also be useful to gauge how quickly the storm layers are healing. Avoid all slopes steeper than 35 degrees, particularly unsupported rollovers in the terrain where you are most likely to trigger an avalanche. These slabs will be large enough to harm you. Below treeline, dangerous conditions may linger into the morning hours, but we think that milder temperatures will help slabs heal more quickly. Ease into the terrain, only moving onto well-supported or smaller-scale steeper slopes if you gain confidence the storm slabs are stabilizing.

    (1/8/2023)

    Example storm slab in terrain below treeline.

Avalanche Discussion

Monday will be an excellent day to practice conservative decisionmaking. Stick to lower angle wind-sheltered slopes or safer terrain along ridgelines and windward aspects if you travel higher. The weather (high winds) will make conditions less pleasant as you ascend, giving you all the more reason to seek better snow on sheltered lower-elevation slopes.

Expect around 18" of storm snow by Monday morning with slabs sitting above a 2/3 melt-freeze crust on sun-affected aspects or a new/old snow interface on shaded or higher elevation slopes. Other prominent crusts in the snowpack include a thin 1/27 crust, the MLK crust, and a 1/4 crust. There is a slight chance that heavily wind-loaded slopes could see avalanches step down to somewhat weaker snow surrounding the MLK crust buried 3 ft or more below the snow surface. 

On Saturday observers reported fairly quiet conditions, warm temperatures, and 1 inch of new snow. The Timberline Ski Patrol reported finding reactive cornices and the Meadows Patrol triggered isolated wind slabs that broke 4-6” deep. 

 

 

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