Lawinenlagebericht

Mt Hood

Northwest Avalanche Center
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Lawinengefahr

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

Kernpunkte

Expect to find variable snow surfaces with pockets of wind slabs that you can trigger on steep, unsupported slopes. With more sunshine in the forecast for Friday, wet loose activity may be more energetic, especially near treeline. Avoid large open slopes warming in direct sunshine and navigate to cooler, shaded aspects.

Lawinenprobleme

  • Wind Slabs

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

    If you're going to trigger a stubborn slab on Friday, it's probably on slopes approaching 40 degrees or on a poorly supported rollover in the terrain. Mt Hood Meadows Patrol reported slabs gaining strength on Thursday with the variability of the surface snow conditions limiting the size of the slabs. You might find areas that are stripped to the 4/11 crust, other areas of sastrugi (wind-scoured snow), and firm or soft wind deposits. Anywhere these wind deposits are 6" or deeper above a crust, you can trigger an avalanche and these deposits are more likely to be found on the E half of the compass. Slabs are likely to break about an inch above the 4/11 crusts on a density interface. It's April and there's less information flowing from the Mt Hood Backcountry. With the added uncertainty in mind, use simple hand shears and small wind-loaded test slopes to evaluate wind slab reactivity before committing to terrain of higher consequence. 

    Example: If you find shallow wind drifted pockets failing on test slopes, consider steering around. 

    Photo: Joe Dellaporta

  • Loose Wet

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

    Wet loose activity is primarily a concern on aspects receiving direct sunshine and within less consolidated dry snow. The amount of entrainment will depend on the depth of the snow above the crust in your terrain. On a larger open slope near treeline, 4-8" of consolidating snow may be available for avalanches in the D1.5 range. Below treeline, most avalanches should be quite shallow. Navigate to colder aspects or lower angle terrain if steep slopes facing the sun are issuing rollerballs or getting sticky and wet. You could trigger a wet avalanche or snow shedding of trees, rocks or cliffs could initiate a wet loose avalanche that may put you in jeopardy from above.

     

    Example: Human triggered wet avalanche near Crystal on Wednesday.

    Photo: NWAC Public Obs

Avalanche Discussion

Friday is a pretty manageable spring day in the mountains, but it won't be without its challenges. Conditions change quickly with the time of day. Expect surface crusts early in the morning on sun-affected aspects that break down as the day progresses.  Although it's mid-April, there's plenty of cold, dry surface snow on many aspects and Friday could be the day we see some more shedding.

Wind loading patterns have been highly variable. Mt Hood Meadows reported 24-hour snow totals of 8" up high and 3" at the base. It was the reverse on Thursday morning with 0.5" up high and 2.5" at the base. This variability may mean that parts of the mountain have significantly more wind loading (and hence higher danger) than others. Pay attention to the amount of snow above the crust and be prepared to dial it back if there's more widespread wind loading in your area. Wind slabs should all be trending in the stabilization direction, but specific pockets of terrain remain reactive and could get you into trouble above terrain traps or other higher consequence areas.

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. One large avalanche on Lords (in the gallery) ran 1000 ft and filled a creek drainage. 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 4/11 crust is now firm and mostly a rough interface at all NWAC forecast elevations.

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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