Bulletin d’avalanche

Olympics

Northwest Avalanche Center
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Danger d’avalanche

Mon
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré last year. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

In most of the terrain, wet avalanches remain your biggest concern on Sunday. Several notable glide cracks opening or failing in recent days serve as a reminder not to travel or linger beneath steep grassy or bedrock slopes. Large cornices may continue to fail without warning and you could intiate a shallow wet loose slide.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1

    Wind slabs linger on shaded aspects while a fresh round of winds from the ESE may form some shallow slabs onto atypical aspects. Note when you move into colder drier surface snow and whether the winds are transporting snow near ridgelines. If they are, slabs may be forming on more W-facing atypical aspects. Some older slabs may remain reactive near ridgelines, so check representative test slopes for cracking and propagation before engaging with more committing slopes at upper elevations. 

    Example: Signs of wind-transport on a ridgeline.  The scalloped features (sastrugi) point to where the wind came from. The cornice is also a red flag. Below sharp ridges like this are where lingering wind slabs may be found to start to day. 

    Photo: Andy Harrington

  • Glide Cracks

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    2

    The focus of the wet activity will be at middle elevations, which still had not received a solid overnight refreeze as of Saturday. This problem encompasses every wet problem in the book on Sunday. Glide avalanches may fail without warning underneath brown frown cracks to the base of the snowpack. Don't spend time under or near these features. Large sagging cornices may continue to fail onto slopes they overhang, potentially entraining moist surface snow on the slopes below. Wet loose avalanches may be initiated within that 2-4" layer of moist surface snow. If they entrain deeper, that would be more concerning. And lastly, wet slabs are probably the least likely, but highest consequence of these problems. So long as meltwater percolates through the snowpack, we can't entirely rule them out.

    So, how do you deal with this smorgasbord of warmth and moisture driven problems? A good overnight refreeze would solve most, but not all problems. Note the presence or absence of one when you enter the field. If you lack an overnight refreeze, continue to limit your time on or under large open slopes. If you have a firm crust in the morning, pay attention to whether this crust breaks down, renewing the problems. In all cases, known glide slopes and slopes with glide cracks should be given a margin for safety.

    (3/29/2025) Large glide cracks ("brown frowns") below the “steep and icy” traverse on the route to Hurricane Hill.   Photo: ONP Rangers

Avalanche Discussion

While temperatures continue to fluctuate about the freezing mark, we just can't seem to get a hard enough refreeze to put the wet problems away. Until we do, large and concerning glide or wet slab avalanches remain a possibility...and glides could linger for multiple days even after the surface refreezes . Ultimately, we need a bit more time with some cold temperatures for the water deeper in the snowpack to freeze up or complete its journey. If you still encounter wet, punchy snow, you can sink into past your ankle on Sunday, choose simple terrain with low consequences. The challenge with these wet snow problems is that they can interact with one another. Any cornice fall or wet avalanche could initiate a wet loose or wet slab on the slope below. We also don't have a complete picture of the water as it percolates through the snowpack, so we don't know exactly when this will run its course.

If you find yourself on a supportable crust in your terrain, refocus your attention to the newer shallow drifts, particularly at upper elevations. Note that these wet and dry snow problems could overlap, in which case a wind slab might entrain older snow.

On Friday, ONP rangers found 2" of new snow that became moist by mid-morning. A similar 2" of snow arrived Saturday and became moist as the day progressed. Cold snow appeared to cling to south-facing ridgelines at 6000 ft, which gives one hope that upper elevations retain 4" of cold snow on shaded aspects. It is possible that this recent snow could slide easily if pushed on a steep slope. The recent snow sits above a profile that resembles the depicted in the gallery, but with the 4" of moist recent snow on top of 22" of denser moist snow above the 3/18 crust . Recent wet slabs in the Crystal Backcountry have run down to the January Drought layer, which is thinner at Hurricane Ridge, and we can't entirely rule it out as a possible failure plane. There are now many bare spots on south-facing slopes, and north-facing aspects 4000-4500 ft have less than 4 ft of snowpack.

If you are out, please share what you see with us and your local backcountry community throughout the spring season

Sunday marks the last day of the Olympic forecast season. From Robert, Dennis, Dallas, and the rest of the NWAC forecast team, we hope it has been a wonderful season. From now on, only special bulletins and avalanche warnings will be issued.

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