Boletín de aludes

Mt Hood

Northwest Avalanche Center
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Peligro de aludes

Sun
Alta montaña
1 · Débil
Límite del bosque
1 · Débil
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 5 months ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The risk of shallow wet avalanches is mostly limited to the highest NWAC forecast elevations where 2-4" of fresh snowfall will destabilize if the sun comes out. Rollerballs and sticky snow surface are your clues to stay out from under long, steep slopes. A corn cycle is unlikely to materialize at upper elevations, so expect slick crusts near or on the snow surface.

Problemas de aludes

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    1

    Snow levels lower from 8000 to 6000 ft Friday night through Saturday. We're expecting 2-4" of snow above 7500 ft and 1-2" arond 6500 ft. This new snow arrives without a lot of wind, so it should be susceptible if the strong April sunshine makes a significant appearance. The more snow falls above the surface crust and the longer the steep slope, the larger the size of the avalanche. Most avalanches will be too small to worry about, but on those 2-4" of dry snow could push you into any variety of exposed obstacles that litter Mt Hood in our low snow year. In a terrain trap such as a creek or gulley, even a shallow wet loose avalanche can bury you. If you notice the sun coming out after more than 2" of snow falls in your terrain, expect a volley of rollerballs followed by snow shedding off rocks or cliffs and ensuing small wet avalanches. Adjust your aspect to cooler slopes in the shade and reduce your overhead exposure.

    Wet loose avalanches within old snow lower on the mountain aren't out of the question, but are quite unlikely following days of mild temperatures. If you see something out of the ordinary, take a step back and reduce your terrain selection.

    Example: Traversing or descending steep slopes covered in wet snow will usually get some of it to slide

    Photo: Lee Lazzara

Avalanche Discussion

Since April 3rd, freezing levels have been flirting with the summit of Mt. Hood at nearly 10-11,000 ft and the snowpack has consolidated 1 ft due to consolidation and melting. The first warm days came as a shock to the dry, upper snowpack, with easily triggered wet loose and even a couple of naturals reported. As high freezing levels persisted, natural wet loose mainly ran their course, while human-triggered wet loose could still be pushed in very steep terrain. On Monday, the Mt. Hood Climbing Rangers reported deeper water percolation and more stubborn wet loose than on previous days. They also found a supportable crust capping dry snow at higher elevations that broke down with daytime warming (observation here). Clear skies and strong winds mid-week allowed for solid overnight freezes, bringing the mountain into a corn cycle extending through Thursday. Mt Hood Meadows reported isolated wet loose avalanches on S and SE aspects on Thursday while higher on the mountain, excellent corn was reported around 11 AM. On Friday, webcams on Mt Hood showed wet snow surfaces around the lower and middle elevations of Mt Hood where temperatures rose into the 40s to low 50s under cloudy skies after a probable poor overnight refreeze. The loss of snow coverage in recent weeks is dramatic in the images and should be on your mind as you ride terrain that typically might have better coverage this time of year.

Precipitation starts to fall Friday evening and continues through Saturday morning. Snow levels gradually lower from 8000 to 6000 ft, with an expected 0.35" of water equivalent. The new snow likely accumulates above and should be relatively well bonded to an underlying crust given the mild temperatures. Isolated very shallow wind slabs could form at the highest elevations with light W winds. If these slabs grow to 6" or more, they could be an isolated hazard to steer around on steep slopes. In less wind affected snow, your focus should be when the sun destabilizes the snow surfaces to instigate shallow natural or human triggered wet avalanches. On wind scoured aspects, firm crusts are likely to persist much of the day. Pack the appropriate traction and self-arrest tools for your objective. Most of these avalanche and travel challenges are focused on upper elevations, but mountain hazards including rock or icefall could exist at any elevation. If you head up high, the Mt. Hood Climbing Ranger page is a great resource for upper mountain planning. 

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

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