Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
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In sintesi

The fifth day of an extended 4 ft storm cycle should give us pause and respect for the potential size of the avalanche problems we have to manage. Regardless of the avalanche flavor, you can trigger an avalanche large enough to bury or kill you in any elevation band. Give slabs extra time to heal amidst the cold temperatures and avoid all unsupported or wind-loaded slopes steeper than 35 degrees.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    An additional 12in of new snow over the next 24 hours will bring storm totals since 12/21 to over 4ft. Gusty westerly winds should easily drift new and recent low-density snow into fresh slabs or enlarge and continue to destabilize existing slabs. Large or very large avalanches are possible in all steep, wind-loaded terrain near and above treeline.  We are in the midst of a very active pattern with the lingering potential for very large natural avalanches in isolated alpine areas. These avalanches could break deeply and run far distances. Shallower avalanches in wind drifted snow will be easy to trigger in many areas. Continue to avoid steep wind-loaded slopes and approach upper elevation terrain with caution. 

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2.5

    A significant storm cycle continues to unload on Mt. Hood and storm slabs will continue to be reactive on Sunday as another foot of snow piles up Saturday night through Sunday. While most of these slabs will release within a variety of the mid-storm layers, a report of an avalanche breaking 3 ft down on the 12/21 crust gives us pause. Such an avalanche would be large (up to size 2.5) and difficult to survive.  of  Continued snowfall will not help the situation, so give the snowpack time to adjust.  Avalanches will be most likely during periods of intense precipitation. With all the new snow, you may even find loose snow avalanches running far and fast. Some wind stiffening in a more exposed area may be the requisite ingredient to form a slab on a slope nearby. Storm slabs have and may continue to release in moderately spaced trees. Until the storm abates, avoid large open slopes or unsupported terrain 35 degrees and steeper.

    (12/25/2021)

    Storm slab propagation in wind-stiffened snow below treeline at Mt. Hood.

    Photo: Ron Martin

Avalanche Discussion

Mt Hood Meadows has picked up 138+ inches of snow in the last 2 weeks with the most recent cycle starting on 12/22. Ski area bses reported 9" of fresh snow in the last 24 hours. The cold, low-density snow keeps piling up through Sunday and maintaining dangerous avalanche conditions.  

Mt Hood Meadows Patrol and public observations report widespread human and explosive-triggered avalanches including storm slabs and loose dry avalanches on Christmas Day. Many of the slabs were small, but one isolated avalanche released 3 ft down to the 12/21 crust. Wind-stiffened the snow below treeline appeared to be a contributing factor in slab formation.

Several triggered avalanches 6-18in thick were also reported Thursday and Friday. In wind-sheltered areas, avalanches have had both storm slab and dry loose characteristics. Additionally, a very large natural avalanche (D3-4) occurred high on the east side of Mt Hood with debris running well below treeline into Heather/Clark Canyon. The timing of this avalanche is unknown, but it is suspected it ran during the last storm ending 12/20.

Some of the coldest temperatures of the year continue to spill into the region. Wind chills will be below zero in exposed terrain. Make sure you are prepared for the conditions and think through the consequences of any accident leading to extended exposure in backcountry terrain.

Deep snow will also be a hazard through the weekend. Watch out for tree wells and keep eyes on your partners. Learn more about deep snow safety HERE.

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