Bollettino valanghe

Mt Hood

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
Open full map
Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You can trigger a large and surprising avalanche on a dangerous weak layer found below and near treeline about 2 ft down. Whumphs, shooting cracks, and reactive test slopes serve as reminders to treat all open slopes steeper than 30 degrees as suspect until we find the slab structure loses reactivity. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2

    Public observations continue to highlight a widespread buried surface hoar layer down 20-24".  The weak layer structure appears to exist in most below and near treeline locations.

    These slabs remain unstable long after a storm and thus, you can still trigger them on a slope as shallow as 30 degrees. Recent avalanches have been triggered remotely or sympathetically. Although you're more likely to trigger a 4-8" storm slab, the potential for a step-down avalanche remains with any slide you trigger. Until we have a better handle on this problem, stick to low-consequence terrain and avoid moderately steep open slopes and convex rollovers.   Persistent weak layers deserve a healthy dose of respect and a more conservative mindset even when avalanche activity may not be widespread, because stepping on the wrong slope may be lethal. See the discussion for more details on recent avalanche activity.

     

    (12/11/2022)

    Public Field Report: Widely propagating persistent slab avalanche released in the last 24 hours. D1.5. White River Canyon.

  • Wind Slabs

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

    Although recent snow has fallen with lighter winds, 2-4 ft deep slabs linger below the calm veneer.  You’ll likely find these wind slabs in different elevation bands, but you’ll find the largest slabs on the lee sides of ridges, below cornices, and above treeline. These slabs of wind-drifted snow may be especially reactive if they sit on top of a buried layer of surface hoar or near-surface facets near treeline.

    (12/9/2022)

    Wind loaded slopes will often exist directly under freshly formed cornices like this. 

    Pea Gravel Ridge, ~5900ft

    Photo: Mitchell Barton

Avalanche Discussion

A D1.5 avalanche in White River canyon broke widely across a terrain feature Saturday night or Sunday morning, reminding us that this layer remains reactive and potentially quite dangerous. The slab/weak layer structure was most reactive on Saturday near the tail end of the most intense portion of the storm cycle. On Saturday, Mt. Hood Meadows Patrol triggered large avalanches with explosives and observed some sympathetic releases 1-3 ft deep. Another observer in the Bennett Pass area remotely triggered a D1.5 soft slab with their snowbike.  They reported crown depths ranging 12-18 inches deep and failing on the new/old snow interface.  Check out the forecast photos for more details.  Another observer in the Bennett Pass area remotely triggered a D1.5 soft slab with their snowbike.  They reported crown depths ranging 12-18 inches deep and failing on the new/old snow interface.  Prior to the storm, avalanche forecasters found the surface hoar and near surface facets at lower and mid elevations ( full observation here). 

All of this recent information illustrates that we have a complex snowpack and this is a good time to take a step back and travel with extra caution.

If you get out into the backcountry,  please submit an observation on our public observation platform!  These observations play an integral role in producing a quality avalanche forecast, but also help the greater backcountry community.

Regioni coperte