Boletín de aludes

Mt Hood

Northwest Avalanche Center
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Peligro de aludes

Tue
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Extreme winds will form firm wind slabs on lee slopes at upper elevations and scour exposed ridgelines and windward slopes down to the previous crust or rocks.  Avoid large wind-loaded slopes above treeline Monday.  At lower elevations, you could trigger a shallower wind slab avalanche on steep slopes where you find wind-textured snow.  

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    This storm will deliver more wind than snow, likely wreaking havoc on the snow surface above treeline.  Firmer wind slabs may form further downslope or in unusual places as extreme winds continue overnight and into Monday morning.  Winds slabs will likely be deeper at upper elevations but are unlikely to be uniform in depth or distribution.  Shooting cracks or whumphing collapses are signs of instability that should not be ignored.  Slab that break on shady aspectes (N-E aspects), have the potential to break wider than anticipated if they fail on weak snow or a slick crust 1-2 ft below the surface. 

    This is a good day to avoid serious avalanche terrain at higher elevations.  At lower and mid-elevations, less snowfall and a milder start to this storm should limit the potential size of wind slab avalanches.  You'll want to steer around any slope steeper than 35 degrees where you find evidence of firmer wind-textured snow. 

    From earlier this winter:

    This is the type of upper elevation terrain likely harboring large, hard wind slabs. It's a good day to stay out of this terrain.  

    Photo: Joe Dellaporta

Avalanche Discussion

Strong winds ramped up to extreme Sunday afternoon with higher elevation weather stations reporting gusts in the 60s and 70s.  This storm was light on snow and began mild, the snow level hovered around 5000' for much of the day.  While the snowfall forecast Sunday night and Monday isn't impressive by Mt Hood standards, a cooling trend along with sustained strong to extreme winds should keep everyone on their toes until conditions ease. 

What a change from the first half of the weekend that featured bluebird conditions and good snow quality above 6000 ft on Saturday. Forecaster Joe Dellaporta took advantage of the nice weather to travel on the south side and was surprised to find a widely propagating avalanche in the lower Salmon River Canyon (SE aspect, 6300 ft). This avalanche was pretty shallow (6-12 inches) but propagated surprisingly wide. The crown was partially filled in, so the avalanche may have occurred Friday. In a snow profile on an adjacent slope, the culprit layer was identified as buried surface hoar 4-6 inches below the snow surface. It was easy to identify with snowpack tests. The forecast team is unsure how widely distributed this weak layer is across the zone, but we suspect the most likely places you may find it will be on shaded slopes above 5000 ft moving forward. 

Other observers traveling on the North side of Mt Hood found cold preserved snow and a fresh crop of surface hoar from our cold, clear night on Friday. This wasn't a problem on Saturday, but if could be an issue in locations that survived the wind and warm start to the storm. 

The lower elevation snowpack has endured a beating after last week's warm-up. Below 5000 ft you'll encounter plenty of shallowly buried objects, open creeks, and rough surfaces. 

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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