Bollettino valanghe

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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Wind and new snow will build fresh wind slabs today. You will most likely find these slabs of wind-deposited snow on west through east-facing slopes at mid and upper elevations. Look for dune-like formations, textured snow, and smooth hollow sounding drifts. If you see snow like this, choose slopes less than 30 degrees to avoid triggering an avalanche.

 

 

Problemi valanghivi

  • Wind Slabs

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

    Stormy weather today will create dangerous avalanche conditions. New snow will quickly build dense slabs on slopes lee to the south through west wind. Blowing snow accumulates much faster than snow falling from the sky.  This can create avalanches that will break much deeper than the amount of snow that has fallen in wind-protected areas. Fluctuating temperatures, rain, and new snow have created a varied upper snowpack. There are many layers that could become the sliding surface for a new wind slab avalanche. If you see dune-like formations, textured snow or shooting cracks pick slopes < 30 degrees.

    (3/31/2023)

    Traveling in the N. Wallowas yesterday afternoon at the onset of this round of wind and snow, I observed shooting cracks on East facing terrain.

  • Storm Slabs

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

    Significant snowfall today will build storm slabs at lower elevations. Consistent snowfall and fluctuating temperatures over the last week have created dense slabs of snow. These slabs will quickly grow in size today These dense slabs sit upon crusts and varying densities of snow. As more snow is added the likelihood of triggering a storm slab avalanche increases. If you find dense snow sitting on a crust or lower-density snow, move to lower-angle terrain (< 30 degrees).

    Traveling in the Northern Wallowas yesterday the snow below 7000' was warm and moist. As the temperature dropped, clouds came in and the wind started to blow, this warm snow became crusty. This newly formed crust will be an excellent sliding surface for today's new snow.

Avalanche Discussion

After a brief break yesterday, the ongoing storm will increase in intensity today. Lots of new snow and moderate to strong winds will create dangerous avalanche conditions. The avalanche hazard will increase throughout the day as more snow and wind build deep deposits of new snow. Travel near and above treeline will be unpleasant today. Those upper elevations will also have the greatest avalanche hazard. Sticking to lower-elevation terrain is advised. 

Consistent snowfall and temperature variations have created a varied upper snowpack. Most slopes besides north-facing terrain have layers of new snow with melt-freeze crusts sandwiching them,  In between these crusts, the density of snow varies. In some places, the snow between the crusts is still soft and low-density. These "crust sandwiches" can create avalanches. Reports of whumpfing and propagation in Extended Column Tests continue to come in from the Western Wallowas. The layer responsible for these collapses is a crust sandwich. This reactive combination has been found between 7100' and 8300' on Northwest, East, and South aspects. If you experience whumpfing, dig down to investigate what caused the collapse in the snowpack. Whumpfing is a red flag of instability, if you experience whumpfing it is advised to avoid slopes steeper than 30 degrees on similar aspects and elevations to where the whumpf occurred. You can watch a video from forecaster Victor McNeil showing this problem here.

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