Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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In sintesi

Slabs will be larger and most reactive at upper elevations, particularly in areas of active wind loading. Use small, representative test slopes to monitor for a firm slab that bonds poorly to a stout crust. Steer around steep slopes with textured snow or lens-shaped pillows. 

Problemi valanghivi

  • Wind Slabs

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

    Typically wind slabs lose reactivity fairly rapidly after a storm, but facets identified at the crust interface may prolong the reactivity. We're gaining confidence that the distribution of slabs large enough to harm you is isolated at middle elevations. Slabs are smaller, pockety in nature, and easier to steer around. However, at upper elevations, they could be large and more connected on the slopes beneath ridgelines and in broad swaths where you encounter wind-stippled snow. Most middle elevation slopes above 6000 ft have around 4-6" of snow on the south side of Mt Hood, with 7-8" on the north side of the mountain. Any slope with wind deposition (more than 6" of snow) should be treated as a potential slab that you can trigger on a slope steeper than 35 degrees. When in doubt, stick to scoured or wind-protected terrain and reduce your slope angle if you encounter whumphs or propagating cracks.

    (2/7/2024)

    Shallow slab fracture on a wind-loaded test slope. N side of Mt Hood.

    Photo: Joe Dellaporta

Avalanche Discussion

Observers in the Cooper Spur and Barrett Spur zones enjoyed fair weather with partly cloudy skies on Wednesday. Photos in the gallery. They found weakening snow surfaces (surface hoar and near surface facets), wind-textured snow in exposed terrain, and the potential for slabs to propagate when faceted snow has been preserved atop the Early February Crust. That crust is very difficult to penetrate and serves as a "new ground" throughout the region. The key finding is that most slabs don't have enough stiffness to create a size 1 avalanche without the impact of the wind. Thus, use your best power of detection to find wind-textured snow and wind loading before you trigger an avalanche that could surprise you in terms of propagation. 

Also, keep in mind the depth of new snow above the crust. In areas where more snow has fallen since the start of February, any avalanche has more snow to entrain. Middle elevations might have 6" snow depths above the stout crust on the south side of Mt Hood with closer to 8" on the N side of the mountain. Snow lines rose to around 5000 ft by late Monday, so only 1-2" of snow exists above the February crust at lower elevations. You're likely to also find a potentially breakable crust at these elevations. This surface crust along with increased wind speeds should limit the potential for wet loose activity, but some potential still exists if the sun comes out for a longer period on Thursday.

The snowpack has transformed over the past week with several inches of rain and warm temperatures. Temperatures returned closer to seasonal norms, but we're left with a more variable snowpack. We lost significant snow at lower elevations, leaving us with many open creeks and shallowly buried obstacles to avoid. Fortunately, middle and upper elevations have held more snow. If you head into the mountains, travel cautiously, as you may encounter new hazards (rocks, open creeks, etc) that weren't present last week. 

Your avalanche, snowpack, or weather observations are extremely valuable to the forecasters at NWAC. Help create a more accurate avalanche forecast by submitting your observations here. 

 

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