Boletín de aludes

Mt Hood

Northwest Avalanche Center
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Peligro de aludes

Fri
Alta montaña
2 · Moderado
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

Overlapping wind slabs are on the menu once again with fresh, small slabs forming on typical aspects and older, potentially larger slabs becoming stubborn on atypical aspects. Steer around steep or unsupported slopes in wind-loaded areas below recently formed cornices. If you find more widespread cracking snow, more significant wind transport, or hear audible whumphs - dial back your terrain selection.

Problemas de aludes

  • Wind Slabs

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

    Around 10-12" of dry snow sits above the 3/27 crust in wind-sheltered areas with 5" of lower-density snow available for transport in wind-exposed terrain. Underlying this lower-density snow, firmer wind deposits that formed through Tuesday night may still be triggered, although they should be stubborn. These slabs could be large in isolated locations. Fresh wind slabs will form on typical aspects, increasing in reactivity and size throughout the day as W winds ramp up. Blowing snow will be your first clue that the danger is rising. Observe which sides of the ridgelines are getting stripped of snow and anticipate wind loading on the other side. Textured snow and fatter pillow-like drifts can also clue you in to the problem. Make use of small test slopes of wind loading aspects to check for reactivity. Shooting cracks or whumphs are your final warning signs to steer around firmer deposits of wind-drifted snow 6" or deeper on slopes steeper than 35 degrees. 

    Cornices developing along Pea Gravel.  You can identify wind loaded slopes on the left side of this picture. 

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Although the winds will be increasing with a fair amount of clouds on parts of the mountain, we think there's a good chance the strong March sun will win the battle in some areas - notably the east slopes and in more wind-protected areas of Mt Hood on Thursday. Expect rollerballs and then small wet loose avalanches as snow sheds off trees and cliffs.  Small wet loose avalanches could gain enough steam atop the 3/27 crust to bury you in a terrain trap such as a creek or gully.

    Example: A D1.5 Wet Loose avalanche. 

    Photo: Ian Nicholson

Avalanche Discussion

East winds switched back to the west on Wednesday afternoon and should gradually ramp up into the moderate range over the next 24 hours. Overlapping wind problems pose challenges because you see a problem developing on a new set of aspects and it's easy to lose sight of the older slabs. If you're not sure you can identify the location of slabs, take a step back and choose wind-sheltered terrain or slopes less than 35 degrees.

NWAC forecasters were in the Gunsight ridge area of Mt Hood on Wednesday. They found deep snow conditions. Tree well safety and snow immersion were on their minds as they made sure to keep good audio and visual communication going to prevent a mishap. Several parties in that area reported audible whumphs as they traveled on shaded open slopes below treeline. The 3/21 crust was 4" thick at 5200 ft on a NW aspect. The layer on top of the crust proved to be reactive: PST 35/100 END. You can see the pit and a video of the 32" slab that propagated. Slightly weaker snow has now been identified on both sides of the crust in multiple locations including Pea Gravel and Vista ridges. In these mid-elevation locations, the reactivity found earlier in the week tended to be below a thinner 0.4" crust. This layer is worth keeping on your mind before considering larger open slopes, particularly if they may be wind loaded. Multiple layers of graupel exist in the snowpack and could remain form reactive interfaces in some areas. 

Mt Hood Meadows reported mostly dry loose avalanches near and above treeline, but triggered some size 1.5 slabs below treeline on Wednesday. With milder temperatures at these elevations, we expect these instabilities to be mostly healed by Thursday. Another observer traveling near Timberline was able to kick off a very isolated and small slab on Wednesday (see photo gallery).

If you're out there enjoying the backcountry take a few minutes and let us know what you see by submitting an observation!

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