Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

New snow and increasing wind speeds will build reactive slabs of wind-drifted snow. Steer around steep slopes that are being actively loaded or show signs of recent loading. Keep an eye out for fast moving dry loose avalanches on steep terrain features.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Winds will change more easterly which will start drifting new low density snow into reactive slabs. You may find these slabs forming in usual spots such as west facing slopes or cross-loading terrain features.

    Recent new snow and heavy drifting have created slabs 1-3 ft thick at mid and upper elevations. Cold temperatures and continued drifting  will help keep these slabs fresh and sensitive to your weight on Thursday. You’ll find these slabs forming on the leeward side of ridges, under cornices, in gullies/couloirs, and cross-loading alpine features. As you travel use visual clues to help you identify slopes of concern. Look for blowing snow, cornice growth, ripples, or rounded pillows at the snow surface to identify where the wind has been at work. If you see shooting cracks under your skis/sled or feel wind-stiffened snow, be ready to take a big step back and avoid nearby steep slopes. 

    (12/3/2022)

    Actively blowing snow, freshly building sharp cornices, and textured surfaces. All easy-to-identify signs of wind-loading. Look for slabs to develop on the slopes on the left side of the picture.

    Photo: Dallas Glass

  • Loose Dry

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Cold temperatures will help keep the new snow low density, so keep an eye out for fast moving dry loose avalanches (also known as sluffs) on steep terrain features at mid and lower elevations. Expect these loose avalanches to be easily triggered on any steep slopes. 

    Pay attention to steep terrain features and consider the run out or parties below you. These slides will be on the smaller side, however they can be consequential if paired with a terrain trap or people moving under you. So have a plan before skiing into steeper features and make sure the run-out is clean. 

    (2/21/2023)

    You may encounter dry loose avalanches like this in steep terrain. 

    Photo: Lee Lazzara

Avalanche Discussion

Avalanche Fatality: Colchuck Pk, East Central Zone: Read the preliminary report here.

Well, Mt Hood overproduced and picked up over 26 inches of new low density snow (6% density) at the Meadows plot. Observers reported deep and blower riding conditions with fairly calm wind speeds. Small dry loose avalanches were widespread and easily triggered across the terrain. Small storm slabs  (6-12 " deep ) were also found in specific terrain features near treeline.  As the snowfall tapers, you may still find some lingering storm instabilities. Use small test slopes or hand pits to see how easily the new storm snow fails.  Adjust your travel plans to more conservative terrain if you notice cracking or see the new snow layer releasing easily.  

These calm wind speeds will be a thing of the past as east winds are forecasted to pick up,  which will start drifting new snow onto some not so common aspects. These unusual loading events will often surprise people and professionals.  So, Thursday will be a good day to make slope specific observations and look for these slabs in weird spots. 

These next few days are going to be down-right cold as a cold upper trough parks over the western US.  Be prepared with extra warm layers and consider the consequence of something going wrong during frigid temperatures like this. 

On Friday,  I traveled into the Gunsight Ridge area to track possible weak surfaces on shaded aspects before heading into this active weather patter. Due to high wind speeds, I didn't find much in the form of surface hoar or near-surface facets. That being said,  it doesn't mean it does not exist in other areas, so keep an eye out as new snow starts trickling in. What caught my eye was a sneaky layer of buried surface hoar about 17 inches below the snow surface. I haven't seen this layer in other areas on the mountain, but it's something worth highlighting if you travel along these ridges in the Bennett Pass or Pocket Creek areas. 

If you get out, let us know what you see by submitting a public observation.

 

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