Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

A human-triggered partial burial on Sunday highlights the risks associated with a well-documented weak interface 2 ft below the snow surface.  We're entering a period of decreasing risk, but sustained high consequences in below and near-treeline terrain. Adjust your mindset for this difficult-to-manage problem and continue to steer around open slopes steeper than 30 degrees.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    The persistent slab avalanche problem on Mt. Hood is unusual for this area and will remain a difficult problem to manage on Tuesday. A 12/8 weak layer of buried surface hoar and near surface facets was well documented since a significant storm cycle began toward the end of last week. NWAC public observations reached a fever pitch of highlighting this problem on Sunday with observers noting it down 18-24" in virtually all locations, finding recent widely propagating slabs, and reactivity in some test pits. Most significantly, a skier was caught, carried, partially buried and strained into trees that day and fortunately was uninjured and self-extracted. Given a terrain trap or a larger slope, the outcome may not be as favorable. The weak layer structure appears to exist in most below and near treeline locations. Even though the reactivity may not be as widespread as Sunday, we expect that you can still trigger these slabs where the slab over weak layer properties are primed for human triggering. Until we have a better handle on this difficult to manage problem, you're best bet is to continue to avoid open slopes steeper than 30 degrees and convex rollovers.

     

    (12/11/2022)

    Skier triggered avalanche failing on the weak interface 2 ft down. ASu-SS-D2-O.

    Photo: Colin Franger

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Some folks made it into the alpine to on Monday and witnessed a lot of snow transport. 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

In addition to the D2 human-triggered avalanche on Sunday, it's worth highlighting other signs of our persistent weak layer. 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 maintain an extra degree of caution.

Cool temperatures will continue in the Mt Hood area. Sunshine likely formed crusts and rollerballs in some areas on Monday but could continue to touch off a random loose avalanche. Stay out from under steep slopes receiving direct sunshine.

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.

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