Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
1 · Debole
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Expect a thin overnight crust to break down with direct sunshine, opening the door to small loose wet avalanche activity during the middle of the day. If you feel the impact of the solar radiation, the snow probably feels it too. Pay attention for rollerballs and wet snow deeper than the top of your ankle and move to shaded aspects to limit your hazard. 

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1

    Much of the snow on Mt. Hood has been affected by warmth (although there have been cold periods) and sunshine. Tuesday and Wednesday had erratic temperatures with more synchonous warm temperatures from Thursday morning onwards. Some of the canyons on Mt. Hood can amplify solar input and it is in these locations that you are most likely to find enough wet snow at the surface to trigger an loose wet avalanche.  Due to the impacts of winds at upper elevations, you are most likely to trigger a wind slab below treeline or in wind-sheltered parts of the near treeline zones. It is in these locations where the sun may initiate rollerballs, a sign that you could trigger a loose wet avalanche.  As snow surfaces warm under direct sun adjust your aspect to avoid the problem.

    Example: A small loose wet avalanche on a slope receiving direct sunshine.

Avalanche Discussion

Mt. Hood saw strong winds which built shallow but reactive wind slabs with the 10-16" of snow that fell during Monday's storm. Reports from Tuesday suggest that winds were strong enough to redistribute the snow into a patchwork of small wind slabs rather than thicken existing wind slabs. Wednesday, the east wind continued to keep the snow surface cool and wind transport active despite above freezing air temperatures, so shallow recently formed wind slabs may exist at upper elevations. The Mt. Hood zone has transitioned from cool E flow on Wednesday to mild W flow on Thursday and Friday under a rebounding high pressure that should keep the mild weather and sunshine in the forecast through much of Saturday before clouds start increase Saturday afternoon.

Last weekend's beautiful weather left snow surfaces at most elevations and aspects firm either by wind scouring or the sun's melt/freezing action. Monday's powerful winds and heavy snow deposited an erratic arrangement of snow depths and textures. Areas in the alpine are scoured bare or packed with dense wind affected snow. At lower elevations, sun-exposed slopes are becoming slushy during the day and becoming firmer by 2 PM, while shaded slopes still hold cold, poorly bonded snow. 

It's important to remember that while the snowpack is generally stabilizing, vastly different conditions will be found at different elevations and on different sides of the mountain. The depth of the snowpack is also significantly different: While the southern sides of the mountain hold 40-50" snowpacks, the NE side remains shallow with 2-30" common near treeline. Rocks and other obstaccles remain shallowly burried.

With a beautiful day in store for Saturday, please remember that NWAC does not have enough consistent and reliable information to accurately forecast for the uppermost slopes of Mt Hood. If you choose to travel in the highest alpine terrain, carry avalanche rescue equipment and be prepared to make your own assessments.

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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