Boletín de aludes

Mt Hood

Northwest Avalanche Center
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Peligro de aludes

Sat
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Significant cold, light snowfall will be easily transported by modest winds to create sensitive wind slabs on lee slopes at middle and upper elevations. Choose slopes under 35 degrees wherever you find more than 6 inches of new snow whether from fresh accumulation or wind-blown snow. Use extra caution near cornices, convex rolls, and above cliffs and creeks.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Very soft, dry snow will be easily transported by even modest winds forming fresh and sensitive wind slabs. These slabs will likely not be firm or textured and it may be hard to identify them visually. Use current wind direction and active blowing snow as your biggest clue to locate them. Soft wind slabs may run easily on the existing firm surfaces. Upper elevation winds are light under southerly flow Thursday but should pick up as winds gain a westerly component Friday. Freshly wind-blown snow will accumulate rapidly on lee slopes and build fresh, easy to trigger wind slabs on lee slopes. Look for actively blowing snow, cracking in the snow, and stiff or textured snow as a sign that you can trigger a wind slab avalanche. Keep your slopes angle below 35 degree where you travel and use extra caution near cornices and ridgelines where snow will accumulate even more rapidly.

    (2/3/2021) Steep, small, wind loaded test slopes show there is some slab character to the recent snow despite it generally feeling more like a loose snow day

  • Loose Dry

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

    Cold temperatures should intensify the amount of new snow arriving Friday.  Expect significant new snow accumulations as the day wears on. Avalanche likelihood will steadily increase throughout the day. This snow is falling on a variety of weak snow surfaces including ice, surface hoar, and faceted snow. Where you find more than 6 inches of new snow you could easily trigger loose avalanches. Watch for signs of natural small avalanches on steep features suggesting that you could trigger a loose snow nearby. Avoid slopes over 35 degrees and steer around steep midslope terrain features and convex rolls. Use extra caution above terrain traps like cliffs and creeks that may amplify the consequence of even a small avalanche.

    (11/20/2020) Example of small loose dry avalanches. Don't let your guard down just because the snow is light. Even a small avalanche can knock you into a creek, a tree well, or over a cliff.

Avalanche Discussion

Strong to extreme west winds have been the main story over the last week at Mt Hood.  Strong winds were felt well below treeline over the weekend and scoured many slopes.  Despite a multi-day wind event, no new avalanches were reported since last week. Textured and firmer wind-affected snow or wind stripped ridgelines are common at all elevations.  In areas where winds have stripped recent snow, a thin freezing rain crust may glaze the surface.   An observation from Newton Canyon found this surface crust even on NE aspects below 6000 ft. In wind-sheltered areas surface snow is becoming faceted and sugary, but that is less common than firm and textured wind-affected snow or areas of scouring.

The stout mid-January crust is considered the new "ground" with a strong snowpack structure in place below this layer. Weak and faceted snow just above the stout rain crust was responsible for a number of avalanches last week, but no new evidence of avalanches on this interface suggests these facets are gaining strength. This weak layer (which is similar in structure to the fatal avalanche in WA)  still exists around Mt Hood and could produce a very large avalanche, but no evidence of recent avalanches on this layer have been reported.

Headed north to recreate?  We have a tricky snowpack with persistent slab problems in all forecast zones across the state line.  Take the time to read about the different snowpacks that have developed further north and adjust your terrain selection accordingly. 

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Preliminary avalanche incident information Monday February 8th, 2021: Two snow bike riders were caught and buried by a very large avalanche in the mountains west of Salmon la Sac Sno-Park along Cle Elum Lake. One snow biker was partially buried and was able to dig himself out. The other rider was fully buried and killed by the avalanche. The avalanche occurred on a north aspect at 4400 ft in the Knox Creek drainage. This terrain lies in NWAC’s East Central forecast zone. Avalanche classification: HS-AV-R3-D3-O. See the short video in the media gallery below.

All of us at NWAC want to extend our condolences to family, friends and the local community following this tragic event.  

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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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