Bollettino valanghe

Olympics

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

After a week of quiet weather, the snowpack will be tested by rain Friday night into Saturday and the best remedy is avoidance. Anticipate mostly small wet snow avalanches on steep or unsupported slopes with saturated snow. In thicker snow areas, these avalanches could be large and in these cases consider a wider buffer.

Problemi valanghivi

  • Wind Slabs

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

    Snow levels should lower below ridgelines by the afternoon with generally W winds transporting snow into the lee of ridgelines as it falls. We generally expect a good bond with the refreezing upper snowpack, but pay particular attention under fresh, sharp cornices and in areas where the snow is actively depositing. These areas could become reactive with 6" of drifting on slopes steeper than 35 degrees.

    (2/9/2023)

    Example: Fresh cornices and scoured slopes are great clues to help you anticipate possible wind-loaded slopes. 

    Photo: Sam Siemens-Luthy

  • Loose Wet

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

    Shaded aspects generally had around 8" of cold, dry snow beneath a moist snow surface. This dry snow may destabilize as water enters the snowpack. Identify the problem where you find saturated snow that you sink into past your ankle (this will likely be widespread on Saturday). Natural or human-triggered point releases will entrain snow as they descend slopes steeper than 35 degrees. A second avalanche concern will be glide avalanches as water runs under smooth bedrock slopes.  Pay particular attention to "brown frowns" in the terrain or any unsupported slopes that could shed and entrain saturated snow on the slopes below, making the two problems related. The thicker the snowpack and the more rainfall your location receives, the greater the problem.

    While we generally expect the snow to absorb the rainwater readily, we're not sure. So, give large open slopes and slopes below complex rocky features a margin for safety. Wet loose avalanche danger will quickly diminish as temperatures drop below freezing, but glide avalanche danger will linger throughout the day.

    Example: Wet loose debris entraining dirt and rocks on a steep road cut.

    Photo: Kaitlin Harrigan

Avalanche Discussion

Friday was the third warmest day of a warm and dry week, but riders reported that moderate winds generally kept previously moist surfaces firm. High pressure has dominated the last 7 days with initially cool and dry weather shifting to warm and dry. The snowpack has consolidated about 0.5" per day consistently. This gradual consolidation resulted in settlement rather than abrupt changes . The Hurricane Ridge snowpack is generally around 2 ft deep, with 35" or so on N-facing aspects. 

As of 12/5, ONP Rangers found that even on N aspects at middle elevations, 0.8" of moist snow exists on the surface. Below that, you'll find around 8" of drier snow sitting above a friable trap crust. Below that the snowpack increases in density to the ground. 

Since Sunday, there has been a small glide avalanche on a grassy road cut (image in the gallery). Note the telltale crack beside it that might have indicated the potential for a glide avalanche even before it released without warning. 

Early season hazards remain in the terrain and shallow snowpacks generally limit real avalanche hazard below around 4400 ft. South-facing exposures have lost significant coverage during the warm-up.

2024-2025 Forecast Schedule

NWAC will issue an avalanche forecast every Friday, Saturday, and Sunday and every holiday mid-week day the Hurricane Ridge Road is open from December until the end of March.  We will issue Avalanche Watches or Warnings when conditions warrant.  We will not update the non-holiday midweek discussion.  Our mountain weather forecasts will continue to cover the Olympics and are issued twice a day through the end of April.  If you have questions or feedback, please contact us at [email protected] and [email protected]. 

If you're out in the snow, share your observations with us and your local backcountry community.

 

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