Boletín de aludes

Mt Hood

Northwest Avalanche Center
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Peligro de aludes

Wed
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

Slabs forming on atypical aspects will be most challenging to navigate at upper elevations. Ascend into exposed terrain cautiously, avoiding steep slopes where you find areas of actively drifting snow or fresh, sharp cornices. Dial back your exposure to consequential terrain if you initiate shooting cracks or audible whumphs.

Problemas de aludes

  • Wind Slabs

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

    E winds ramped up during the day and light snow started late Monday afternoon on Mt Hood. We're expecting 5-7" of snow by the end of the day on Tuesday with moderate ridgeline winds generally out of the SE. The snow will actively redistribute from E aspects and tend to load more atypical W aspects. Variable snow surfaces predated the storm, so expect to find crusts or old wind-affected snow surfaces in areas stripped of snow, with reactive slabs forming atop this interface where you find deposits more than 6" deep. Avalanches may propagate more widely if they initiate on the crust (W-S-E aspects). If winds move snow onto previously protected areas on the north side of the compass, slabs could overly isolated deposits of surface hoar. Any sign of whumphs, abrupt settlement, or shooting cracks initiating along the new/old interface should be taken seriously. Several graupel layers down 2-4 ft were reactive in tests as recently as Sunday. These layers could be reactive to skier trigger in a sufficiently wind-loaded location and remain an additional reason to stay cautious on Tuesday. Avoid wind-loaded slopes 35 degrees and steeper, using ridges and wind-stripped areas to navigate safely away from thicker deposits of wind-textured or drifting snow.

    Example: Shooting crack in wind-textured snow. If that crack keeps going, a slab releases.

    Photo: Joe Dellaporta

Avalanche Discussion

East winds started early Monday and ramped up throughout the day. Snow was blowing and drifting, forming more reactive slabs above treeline. The mountain was already heavily wind affected and despite cool temperatures, a sun crust up to 1 cm thick formed over the weekend below treeline (W-S-E). This limited the snow available for transport on Monday. However, 5-7" of fresh snow with moderate winds and strong to extreme gusts will provide plenty of ammunition for slabs focusing on the western half of the compass.

Multiple graupel layers now exist within the snowpack and can provide a plane of failure in the snowpack. Give these layers a test before committing to larger or steeper slopes. An isolated pocket of surface hoar could be buried at the 3/27 interface and a snowpack test may not be sufficient for evaluating a nearby slope. Consider mitigating risk by choosing smaller open slopes without exposure to terrain traps if you think surface hoar might have been preserved in your area.

The current east wind comes on the back of a powerful early Spring snow storm Thursday through Saturday that brought several feet of snow.  Strong west winds built firmer and deeper wind slabs over this period. On Saturday, Mt Hood Meadows pro-patrol triggered large avalanches with explosives  (up to D2.5) in wind-drifted snow.  These deeper and more dangerous wind slabs were becoming difficult to trigger on Sunday and recent storm instabilities were generally stabilizing.  On the eastern half of the mountain, abundant sunshine on Sunday followed by cooling overnight will form new surface crusts on many aspects. Even with the colder-than-normal late March temperatures, the snow surface below treeline was becoming moist or wet on sunny slopes on Sunday.  

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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