Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

A dangerous persistent weak layer may still be reactive in some areas, but in a lot of locations, it appears to be gaining strength. For those without professional-level field skills, you may want to hold off on open slopes steeper than 30 degrees another day.  Shovel shear and tilt tests on the interface 18-24" down may help give others the confidence to ease onto smaller, well-supported terrain features.

Problemi valanghivi

  • Persistent Slabs

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

    Our persistent surface hoar and near-surface facet interface remains a concern, although the interface may be less reactive than a few days prior. Approximately 27" of snow has fallen since the weak layer was buried on 12/8. The most recent signs of instability were shooting cracks, a red flag signs of instability, in White River Canyon on Monday.  NWAC public observations reached a fever pitch on Sunday with observers noting the settled slab to be 15-24" 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. Recent reports indicate the weak interface may be gaining strength, becoming harder to identify or get reactive tests on. It's most likely to remain reactive on colder northerly aspects and steep, convex rollovers where the slope drops away from you out of sight. Prudent backcountry travelers will continuously assess this layer as they travel through the terrain, performing multiple hand shears, shovel shears, or better yet shovel tilt tests (see the video). If and only if you are confident that the slab over weak layer structure is NOT present in your terrain, should you consider easing into simple avalanche terrain such as well-supported smaller slopes away from terrain traps such as creeks and gullies.

     

  • Wind Slabs

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

    Mt. Hood meadows patrol found reactive 5" wind slabs in exposed locations on Tuesday. We think you will still be able to trigger them on steep, unsupported slopes. Expect to find the largest and most reactive slabs above the treeline where drifts are deeper such as slopes below recently formed cornices or where you find lens-shaped pillows. 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, there was plenty of snow transport toward the end of last week.  

    Example: An intentionally triggered Wind Slab by a skier on a convex rollover. The snow in this area looked "fat" and was stiffer. Watch for areas with similar characteristics on Wednesday.

    Photo: Andy Harrington

Avalanche Discussion

On Monday, Mt. Hood Meadows Pro patrol failed to identify a convincing weak layer in test pits on NE aspects both above and below treeline, and on a SE aspect below treeline. However, we're not ready to count the problem out and we don't suggest you do either. Shooting cracks on Monday and the D2 human-triggered avalanche on Sunday keep this problem at the top of the list. 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.  Prior to the storm, avalanche forecasters found the surface hoar and near surface facets at lower and mid elevations ( full observation here). As you look to address a complex snowpack in the below and near treeline areas, the best answer for most people will be to keep things simple and stick to low angle slopes (less than 30 degrees) or densely treed terrain.

Cool temperatures will continue in the Mt Hood area, but the sun started to produce more rollerballs and small wet loose avalanches. Expect more of the same on Wednesday.

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