Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

Heavy snowfall and wind will continue to stress the snowpack and create dangerous avalanche conditions on Monday. Wind loaded terrain above 6000 ft will be the most dangerous, but still consider any steep slope as suspect, even in lower elevation sheltered areas. Seek out low angle terrain out of the wind until the storm has its course. 

Problèmes avalancheux

  • Wind Slabs

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

    Continued heavy snowfall and strong S-SW winds will continue to build large, 2-3 foot thick wind slabs across leeward slopes at middle and upper elevations. These slabs could be sensitive to the weight of a skier or climber and break widely across terrain features if triggered. 

    You’ll want to give these wind loaded slopes some space on Monday. Look for blowing snow, cornice formation, and pillow-like drifts to help you pinpoint where the wind has deposited snow into stiffer slabs. Changes in snow depth and stiffness or shooting cracks are obvious clues that you found a wind slab. 

    Don’t let a couple of hours of clearing make you think wind-loaded slopes are good to go. Stick to simple, sheltered terrain until this active weather has passed. 

    (12/15/2024)

    The crown of an explosive triggered hard slab in a wind drifted location at Mt. Hood Meadows ski area. Crown depths ranged from 3-3.5 ft. 

    HS-AE-R3-D2-S

    ENE @ 6800 ft

    Photo: Nick Asher, MHM Pro Patrol

  • Storm Slabs

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

    With more significant snowfall (over 1.00 inch of water equivalent), you may be able to easily trigger avalanches in more protected terrain - especially during morning hours or periods of heavy snowfall. This new snow may be a little denser than our last round, so storm slabs may be primed for human-triggering.  

     Before jumping into steeper slopes, check to see how the new snow is bonding to the pre-existing surface. Look for cracking or snow sliding easily with snowpack tests. Consider choosing supported terrain and avoid rollovers until this storm snow has settled out. 

    (12/20/2021)

    An example of a small storm slab. You could trigger small avalanches in protected steep terrain on Monday. 

    Photo: Andrew Kiefer

Avalanche Discussion

The storm train just continues to deliver for Mt.Hood and the southern Washington volcanoes. Another round of precipitation (1-1.5 inches of precipitation) will accompany strong S/SW winds on Sunday evening into Monday morning. We suspect you’ll find the most dangerous conditions during the early morning hours before snowfall begins to taper. Once the storm washes through, it’s possible we could see some sun breaks during the afternoon hours, so keep flexible and keep an eye out for signs of warming along solar slopes. 

On Sunday, the Mt Hood Meadows Pro Patrol reported triggering large avalanches with good propagation in wind drifted terrain during avalanche mitigation work. They found these hard wind slabs (P hard) breaking 3-3.5 ft deep on a softer layer of storm snow.  We also heard two reports of avalanches on Mt Adams, one human-triggered and one natural. Both were around 8000ft on S to E aspects in wind-loaded terrain. These recent avalanches are a good reminder that these incremental storms are now building thick unstable slabs across the terrain, and it’s a good reason to step it back until the storm is wrapped up. 

Leading up to this storm, we had a variety of surfaces across the terrain. Solar aspects ( SW-SE) consisted of scoured surfaces and a stout sun crust. Shaded aspects held old wind-drifted snow, some weakening surfaces, and even some isolated surface hoar. The big question moving forward will be how the new load of snow bonds to these, in some cases, weak surfaces. The best strategy during this loading event is to err on the side of caution by giving larger slopes some time to adjust to the new load and continue to gather more information.

Régions couvertes