Bollettino valanghe

Central Cascades

Central Oregon Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

We have received 2-3 ft. of new snow over the weekend and avalanches will continue to be possible throughout the terrain.  Wind Slab avalanches will be likely and could be large on East Slopes near treeline, and in the alpine.  Storm Slabs and Dry Loose avalanches will continue to be possible below treeline as the new snow needs time to settle.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2.5

    Shallow wind slabs were observed near treeline on Sunday.  I don't expect that this was the full extent of the problem; Moderate West winds have the potential to move a lot of snow and create large Wind Slabs on East slopes.  This transport of snow will continue overnight and on Monday.  If traveling on wind loaded slopes it is wise to make conservative terrain choices and avoid steep, unsupported slopes.  Moderate wind speeds are the best at building wind slabs directly below ridgetops and crossloaded features.

    Clues to recent and previous wind blown snow include:  blowing snow, recent cornice and wind lip growth, and variable snow textures or depths on adjacent slopes.

  • Storm Slabs

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

    On Sunday, there were observations of slab avalanches below treeline.  Storm Slabs will begin to settle overnight, but with continuing snow and cold temperatures, they will remain possible on Monday.  Be particualrly wary of steep, unsupported terrain.

    Your best clue for assessing Storm Slabs is looking for cohesion in the surface snow, and an underlying weak layer.  Because this problem exists in the upper snow pack, tests along your skin track can be a great tool.  Look for short steep test slopes that you can ride across, and use hand shears (maybe some pretty deep ones) to see if the surface snow is "slabby".

  • Loose Dry

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    We have received a lot of new snow recently!  As time passes since the last period of heavy snowfall (maybe Sunday evening) this snow will begin to settle.  Until that process is complete, expect to see some snow moving on steep pitches throughout the terrain.  Where this surface snow lacks cohesion we will see Dry Loose avalanches.  Dry Loose avalanches tend to involve less snow and be more predictable than slab avalanches.  Nonetheless they can be consequential, particularly when terrain traps are present.

     

Avalanche Discussion

As of Sunday evening, some areas have received approximately 75 cm. of new snow.  Our primary concerns have been those avalanche problems that we associate with new snow and wind.  There have been a few observations of burried surface hoar during the last week.  None of these layers have proved particularly reactive in tests or produced recent avalanches.  These layers would exist between 75 cm. and 1.5 m beneath the surface and on North facing sheltered terrain.

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