Bollettino valanghe

Central Cascades

Central Oregon Avalanche Center
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Pericolo valanghe

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

On Monday Wet Loose avalanches will be likely as the day heats up on the warmest slopes (steep, sunny slopes).  Small Wind Slabs will also be possible at higher elevations below ridgetops and particularly on south slopes.  Since Friday, several avalanches have been observed that likely failed on weak snow above a melt-freeze crust deeper in our snowpack.  While avalanches on this layer are unlikely, resulting avalanches would be surprisingly large and thus dangerous.  Careful snowpack evaluation is advised before comitting to large, steep slopes that face north or east.

Problemi valanghivi

  • Loose Wet

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

    The weather forecast for Monday calls for high temperatures reaching into the 40's at treeline, clear skies, and light winds.  This heat will melt the surface snow.  As the snow melts it looses cohesion.  Earlier in the day this can be a good thing as softer snow is preferable to ride; but as the heat and melting continue Wet Loose avalanches will become likely.  Initially you may see small avalanches below rocks and from the steepest terrain.  As slopes get too slushy it is time to move to cooler slopes.  Often folks use these high pressure windows to ride steeper slopes at alpine elevations.  Be mindful of the other avalanche problems in this list, and remember that even a small Wet Loose avalanche can have bigger consequences if it knocks you off your feet in steep terrain.

  • Persistent Slabs

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

    I had a hard time deciding whether or not to include Persistent Slab in our problem list.  The layer in question is a thin layer of facets above the melt-freeze crust in our upper snowpack.  I dug a lot of profiles at Tam rim today and I wasn't able to find any facets or get any test results that I would associate with avalanche activity.  That being said we have seen several surprisingly large avalanches over the last three days that can be attributed to this layer.  "Surprising" and "large" are important qualifiers when it comes to avalanches, so this avalanche character is defintely one worth considering in your travels even if it is unlikely.  If you are digging to evaluate this layer look for the melt-freeze crust (the weak layer is a thin layer of facets directly above the crust); observers have been finding it 35-60 cm. down and as deep as 120 cm. in wind loaded areas.

    Hopefully we've seen all the avalanches we are going to on this layer, and it'll disappear from the forecast in a few days.

    (3/29/2024)

    This avalanche failed on a layer of 1mm facets above an old melt freeze crust down 45 cm (18"). The slab propagated about 45' across. This was on a NNE slope near treeline on Friday. Size D2 (large). 

    Photo: Jonas Tarlen

  • Wind Slabs

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

    Today I observed Moderate winds moving snow off of previously loaded north slopes and reverse loading it onto south slopes.  Due to variations in wind direction and speed throughout the terrain I'm keeping Wind Slabs on all aspects.  Look for obvious clues of recent blowing snow like textures associated with wind scoured or deposited snow, variable snow depth, and recent cornice growth or erosion.

    (3/31/2024)

    Moderate blowing snow from the north

    Photo: Gabriel Coler

Avalanche Discussion

This avalanche forecast has a lot going on!  If it helps, break it down into each problem. 

Time your tour to find good riding and avoid any danger from Wet Loose avalanches. 

The Persistent Slab problem has the potential to be the most dangerous one and each of us will have our own risk tolerances.  Identify slopes you might want to avoid because they are too big, steep or complex.  Then consider doing some evaluation before riding the terrain you have chosen.  Ride one at a time and avoid trigger points.

Most of us are used to dealing with Wind Slabs although they may show up in places that we aren't used to seeing them.  I expect Wind Slabs on Monday to be small.  If you see evidence of recent wind loading, avoid steep convex slopes below ridgelines.

Regioni coperte