Lawinenlagebericht

Mt Hood

Northwest Avalanche Center
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Lawinengefahr

Sat
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

You can trigger a stubborn slab in exposed terrain, and it may propagate more widely than you expect to become large. Steer around steep or poorly supported  heavily wind loaded features, even lower down on a slope. Sunshine will destabilize surface snow on less wind-affected steep, open slopes.

Lawinenprobleme

  • Wind Slabs

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

    Reactive wind slabs with active snow transport on Thursday will become stubborn to trigger by Friday. Given the potential large size of the slabs and recent extent of the wind transport, the distribution of more deeply drifted snow should govern your travel in exposed terrain. Start by sampling small, inconsequential test slopes, making sure to check the interface 2-3" above the 3/31 crust.  Ease into the terrain, steering around slopes 35 degrees or steeper, and giving a margin for safety around unsupported features. If you experience cracking or encounter hollow-feeling snow, you're likely to trigger an avalanche on a similar, but steeper slope. The weather will be inviting, but the impacts of strong to extreme winds don't resolve overnight. Remind yourself that these slabs may need another day to gain strength before engaging with higher consequence features. Slabs are likely to be small, isoated, and softer slabs at lower elevation, transitioning to large hard slabs at upper elevations. Note this change as you ascend and dial back your terrain selection accordingly.

    The wind slab risk will focus on the eastern half of the compass with reactivity retreating from lower elevations and the southern half of the compass as warmth and sunshine go to work on these slopes first.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    Up to a foot of less wind affected snow can be found in sheltered terrain between 5000-6500 ft. This cold, dry snow will be susceptible to rapid warming and sunshine on Friday. Expect heightened reactivity to shift from E to S to W aspects as the day progresses. A volley of rollerballs is your first warning sign, followed by snow shedding of rocks and cliffs, and entraining moistening loose snow on the slopes below. Reduce your exposure to steep slopes which may be above you during this time of transition. Avalanches are likely to slide efficiently atop the 3/31 crust.

    Example: Wet loose avalanches sliding on a crust.

    Photo: Joe Dellaporta

Avalanche Discussion

Friday is the rapid transition from cold an stormy to warm and dry. Cold snow doesn't like rapid warming, while wind slabs remain quite recent. Focus on the wind slab problems in areas where the snow is wind-stippled, punchy, or firm. Focus on wet snow concerns where you encounter lower density dry snow. In these areas you could also trigger a dry loose avalanch before temperatures warm. In all cases, focus on the snow above the widespread and thick 3/31 crust, which represents a "new ground" in the terrain and was particularly slick at upper elevations prior to the recent storm cycle.

Tuesday through Thursday brought 1.6" of water equivalent to the mountain and increased the base depth from 51" to 60" at Mt Hood Meadows. Moderate snow shower activity continued at times through Thursday morning, decreasing during the afternoon hours. The winds had other ideas, ramping up into the sustained 40-50 mph range during the afternoon. These winds transported intense plumes of snow during the day, but the snow that remains by Thursday night is likely to be much less available for transport as winds ramp down. By Friday, we expect light winds and mostly sunny skies.

Conditions were most reactive early in the day on Thursday following 7-10" of fresh snowfall Wednesday night. Avalanche activity initiated on a subtle density change 2-3" above the 3/31 crust, resting beneath 8-12" firmer slab. Mt Hood Meadows Pro Patrol triggered a handful of D1.5 avalanches on Thursday with wide propagation observed in middle and upper elevation terrain. On Wednesday morning, the upper elevations of Mt Hood Meadows produced two explosive-triggered avalanches: D2 in Silver Bowl that ran full path with a 6-18" crown depth in addition to a D1.5 in A-zone. 

Although the snow conditions should be significantly improved after the recent snowfall, windward aspects and ridgelines remain stripped to the 3/31 crust or ground. Make sure you have the tools and the skills to arrest a fall on steep, crusty slopes. Travel hazards abound at lower and middle elevations due to historically low snow.  Fresh snow is likely to obscure hazards, but not materially change the underlying poor coverage.

Are you heading out?  Let us know what you see by submitting an observation here or on the AvyApp.

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