Lawinenlagebericht

Mt Hood

Northwest Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 6 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

You could trigger a large and surprising avalanche within wind-drifted snow at upper elevations where weak snow lies above a crust. Take note of any signs of instability including whumps, shooting cracks, or firm punchy layers in the snow. Avoid wind-loaded slopes steeper 35 degrees.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    SE winds rapidly transported new snow Tuesday night and formed sensitive wind slabs that will be larger as you ascend in the terrain. It's safe to say these are not your garden variety Mt. Hood wind slabs, forming atop weak snow (facets) above a crust. The remaining ingredients for an avalanche? Wind-affects snow (slab) and a steep slope. SE winds created slabs on unusual aspects that may be widespread above treeline. Avalanches will run easily on the icy mid-January crust and may be easier to trigger than you expect.  A significant whumphing collapse reported to NWAC from a N aspect at 7000 ft on the Cooper Spur on Thursday reminds us not to treat this setup lightly. Shooting cracks in the surface snow are also a clear sign of instability. Don’t assume you can visually identify slabs as recent snow came in with lighter winds. Reduce your slope angle as you head into wind-affected terrain.

    Firmer wind slab avalanches like the one in this photo will be easier to trigger as the day wears on and winds continue to move snow.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    There's plenty of soft dry snow that hasn't experienced much warming or sunshine and will respond quickly to rapid warming. With plenty of sunshine in the forecast through early afternoon on Friday, expect the dry snow to initially start to moisten and move downslope on SE, then S, and finally SW aspects. Use rollerballs or snow falling of cliffs or trees to anticipate wet loose avalanche activity on slopes 35 degrees and steeper. Adjust your aspect to colder, shaded slopes as the snow starts to heat up. While we generally expect these avalanches to remain small, they could become large given sufficient warming.

Avalanche Discussion

Mid-elevation upper snowpack is expected to average 10-15", above the stout mid-January crust. The stout mid-January crust should be considered the new "ground" moving forward with a strong snowpack structure in place below this layer.  A pattern of recurring avalanches on this layer will likely be with us until a warmer storm brings snow to bond to this old icy surface.  The most recent 2-4" of snow fell Wednesday night with light winds. A slightly more significant event (4-9") arrived Tuesday night, but an uncommon SE wind pattern means the distribution of that snow is variable. The eastern side of the mountain received more snow than the western slopes and the north side of the mountain received some of the stronger winds Tuesday night. Wednesday night's lower density snow may make it more challenging to identify wind slabs formed Tuesday night.

In addition to Wind Slabs and Wet Loose avalanches, cold temperatures resulted in higher snow totals than we might typically expect from the modest precipitation we received. Soft, deep snow will slide easily on the firm surfaces from mid-January that are still near the surface. Uphill travel has been challenging despite the recent coat of snow. Pockets of deeper snow will slide easily on the same crust that makes travel challenging in wind-stripped areas. Steer around steep start zones (slopes greater than 35 degrees) where you find more than 8-10" of snow above the old rain crust.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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