Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Heavy rain, snow, and wind will create very dangerous slabs dry and wet slabs, particularly at upper elevations on Mt Hood. Be aware of the terrain above you and avoid, steering clear of slopes connected to large avalanche paths at any elevation. You can also trigger a wet avalanche within saturated snow.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1.5–2.5

    Sunday will be very dangerous at upper elevation as an atmospheric river unloads heavy, dense snow above 7000-7500 ft. We expect the rates of snowfall to tip the upper snowpack to the breaking point. Add strong WSW winds to the assault from the skies and expect some of these avalanches to push into the size 2.5 range.  Avoid all upper-elevation avalanche terrain. Additionally, these avalanches can run several thousand feet, so avoid avalanche paths and runouts where an avalanche can originate from these upper-elevation start zones. 

    Example: Multiple large (up to D2.5) slab releases with 1-4 ft crowns in Mt Hood Meadows A-zone. 

    Photo: Mt Hood Meadows Pro Patrol

  • Wet Slabs

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

    You don't want to be in the wrong place when a wet slab releases. We have the setup on Sunday: 3" of rainfall running through the snowpack combined with a 12/6 crust that will pool that water on a sliding surface. It is impossible to predict when a wet slab will release, but during these periods of uncertainty, it's best to avoid exposure to slopes 35 degrees and steeper with enough snow to avalanche. Expect these slabs to carry 8" of settled snow on the ground before the current storm, plus whatever falls before the snow changes to rain.  Saturated snow, runnels, rollerballs, or smaller wet loose avalanches all confirm the potential for a large and dangerous wet slab.

    Example: A D2 (large) wet snow avalanche.

    Photo: Irene Henninger

Avalanche Discussion

The avalanche danger likely peaks Saturday night with strong warming and very heavy rain and snow, but that peak danger may extend into the morning hours at upper elevation. As a result, it's a good day to stay out of avalanche terrain and let the mountain adjust to a heavy rain and snow event.

A foot of new snow that fell Thursday and Friday consolidated into a firm and breakable 8" layer that was losing reactivity on Saturday.  Another inch of snow fell on Saturday and mixed with rain in the mid-day hours briefly at Mt Hood Meadows. The recent snow sits above a  stout 1/6 crust.

On Friday, forecaster Joe Dellaporta found increasing avalanche hazard with elevation. Small but sensitive wind slabs were easy to trigger on lee slopes (ENE) near treeline/6500'.  Strong winds in the morning moved snow easily on the upper mountain but had subsided around mid-day. At this elevation, 30-35cm (12-14") of storm snow was well bonded to the underlying crust and refreezing lower snowpack. Travel was challenging at all lower elevations and wind-stripped terrain due to low and variable snow cover. Photos in the gallery.

A significant multi-day storm cycle ended on 12/6, dumping an amazing 10-12" of precipitation on the mountain.  Unfortunately, most of this precipitation fell as rain outside the upper reaches of the mountain and knocked down the early-season snowpack.  The weak atmospheric river won't help these meager lower-elevation snowpacks, so keep early-season hazards at the forefront of your mind if there's even enough snow to recreate at lower elevations by Sunday.

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