Bulletin d’avalanche

Olympics

Northwest Avalanche Center
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Danger d’avalanche

Sat
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You'll find that wind slabs have formed in all elevation bands and on atypical aspects due to strong winds and new snow.  Don't assume usual windward aspects are safe.  Put a wide buffer between you and any open slope steeper than 35 degrees at mid and upper elevations.   

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Observers on Thursday noted much stronger winds and more wind transport than the weather station at Hurricane Ridge would indicate.  Wind slabs were already growing large and sensitive, with shooting cracks in the new snow.   Besides obvious wind-loaded slopes, you may also trigger a wind slab avalanche from below.  Make sure to give yourself a buffer while approaching any open slope that could slide.  Assume that cornices are sensitive and ready to fail if traveling along ridgelines. Seek out lower angle and wind-sheltered terrain on Friday. 

    While wind-affected snow will be the main story, you may trigger a small storm slab avalanche or a loose dry avalanche in sheltered terrain below treeline.  Steer around convex rollovers and open slopes steeper than 40 degrees.  If the sun pops out for an extended period of time, expect loose avalanches to release on very steep W-S-E slopes.  

    Wind slab avalanches like the one in the photo should be easy to trigger on Friday.

Avalanche Discussion

As of 2 pm Thursday, 8" of new snow could be found below treeline, with double that drifted onto lees slopes near treeline.  By Friday morning, we could have doubled our storm totals as winds remain strong to even extreme out of the WNW.  While the shower activity and winds are expected to back down during the day Friday,  assume that you can trigger an avalanche in the new snow.  Below the most recent snow, a melt-freeze crust formed by either the sun or above freezing temperatures formed on many aspects (2/23).  

Below the 2/23 crust found at mid and lower elevations, the upper snowpack is strong.  We know less about the layering of the snowpack above treeline. The mid-January weak layer facet/crust combo is down 4-5 feet and was difficult to discern in snowpits at 5100' on Thursday.  The last time avalanches ran on this deep interface in the Hurricane Ridge area was back in early February.  This is the same weak layer/crust combination that resulted in very large avalanches (several feet deep and big enough to destroy a wood cabin or car) in large swaths of the central Cascades on Monday during an intense and prolonged storm cycle.  While we will continue to track this interface,  avalanche concerns should be limited to new snow moving forward. 

2020-21 Forecast Schedule: Avalanche danger ratings will be issued for the Olympics every Friday through Sunday and during mid-week holidays. During the week when the Hurricane Ridge road is closed, forecast information will be updated daily to include expected conditions and relevant travel advice under the No Rating label.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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