Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Additional snow and increasing temperatures will prolong dangerous avalanche conditions. You could trigger avalanches in the new snow, particularly where the winds formed stiff slabs at upper elevations. The recent snow fell on weak or slick surfaces, and avalanches could break wider than expected. Your best option is conservative low-angle terrain choices and avoiding steep slopes with deep drifts.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2

    Stormy conditions will begin to taper, but the winds have already formed dangerous wind slabs. Where they formed over slick or weak surfaces, they could take longer to heal than usual and break widely across terrain. To avoid triggering one of these large wind slabs, stick to slopes less than 30 degrees or travel on scoured ridgelines or slopes at mid and upper elevations. If you see cracks shooting away from you, the snowpack feels hollow or collapses beneath you, steer clear of steep terrain.Wednesday night and Thursday brought 10-14" of low-density snow and moderate winds. The light snow and shifting wind directions formed sensitive slabs 2-3ft deep on various aspects. Use visual clues like textured surfaces, cornices, and drifts around rocks and trees to point you to likely wind slab locations.

    Example: Cornices suggest wind loading on the slopes below. Check your slope angle. If it's over 35 degrees, you could trigger a large avalanche on a similar slope on Thursday.

    Photo: Joe Dellaporta

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Various weak surfaces, including surface hoars, may be buried beneath the new snow in sheltered terrain, and snow fell on slick sun crusts at lower elevations on southerly aspects. So, even if you're seeking out wind-sheltered terrain, you could trigger a storm slab. It will be best to keep your slope angles low to prevent getting caught in a surprising avalanche. You can use quick hand pits or small test slopes to check how well the new snow bonds with the old surface. However, these tests can't account for the natural variability of these weak layers. It is better not to attempt to assess your way into steeper terrain and choose simple low-angle terrain until the storm clears and we have more information on the distribution of these layers. On Thursday, Mt. Hood Meadows Patrol reported sensitive small storm slabs with wide propagation. This is potentially a sign that these instabilities will take longer than normal to heal. In addition to buried weak layers, another 2-3 inches of snow with warming temperatures could add to the storm slab problem. 

    Example: Storm slabs like this may be easily triggered on Thursday at lower elevations. 

    Photo: Andrew Kiefer

Avalanche Discussion

Expect tapering but still stormy conditions on Friday. Winds will be lighter in the morning before increasing again in the afternoon, and morning snow showers will give way to primarily overcast skies. We don't expect to see much rain, but snow levels will jump to 4000ft by the afternoon, and you could start to see some rollerballs or trees and rocks shedding moist snow. 

On Wednesday, 4" of snow with very light winds fell, potentially preserving pockets of surface hoar on northerly aspects. We have uncertainty about the distribution, but now that this layer is buried 1-2ft deep, you should consider the consequences of a larger avalanche that breaks widely across terrain. There is weak snow near the 2/11 interface and above the early February crust. We suspect the reactivity on these interfaces to be variable, isolated, and primarily at upper elevations. 

Below 7000ft on southerly aspects, you may find a slick sun crust buried below the recent snow. Strong WSW winds last weekend created old, large slabs earlier in the week. A collapse reported Tuesday at 10,000 ft on the E side of the Hogsback was a sign that some older weaker snow layers had not healed. There was also a small skier-triggered avalanche on Tuesday at 6200 ft on an E aspect (see photo in the gallery).

The lower elevation snowpack has endured a beating after last week's warm-up, but expect rapidly increasing danger on steeper open slopes. Below 5000 ft, shallowly buried obstacles remain hazards, and open creeks are difficult to cross in some areas.

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