Bulletin d’avalanche

Olympics

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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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 can still trigger a large slab avalanche on steep lee slopes below ridgelines.  Large cornices are weak following several days of warm weather; give them plenty of space along ridgelines and don't hang out on open slopes below them. 

Problèmes avalancheux

  • Loose Wet

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

    Several days into our warm-up, you may not see signs of increasing instability associated with wet loose avalanches like pinwheels or rollerballs.  Move to lower angle terrain on any steep slope where you find yourself sinking into wet surface snow more than a few inches deep.  After a mild and potentially sunny start to the day, increasing cloud cover and ridgeline winds will likely decrease the chances of wet loose avalanches later in the afternoon.  

    Small avalanches can be triggered in isolated areas during Low danger.  Avoid extreme terrain features at lower elevations where you find wet surface snow.  Take care near terrain traps, even small wet loose avalanches can pack a punch and knock you off your feet. 

    You'll likely find evidence of warming temps and sunshine over the last few days in the form of large rollerballs on steep southerly slopes.

  • Wind Slabs

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

    A large slab avalanche was triggered by a rider on a lee northerly aspect above Klahhane Bowl at 6000' on Friday, fortunately, no one was caught.  Southerly winds during last week's storm cycle drifted 2'+ of storm snow onto W-N-E aspects.  Loose storm snow previously found on shady aspects has now become denser with warming temperatures.  Avoid steep lee wind-loaded slopes near rocky features such as cliff bands and gullies where you are more likely to trigger a slab avalanche.  Stick to broader more open slopes or windward aspects to steer clear of the problem Saturday.

    Large cornices can be found above the same lee slopes where wind slabs are likely to linger.  Cornices are known to break further back than expected and often fail during extended periods of warmer weather, like the one we are in now.  Give them a wide berth if traveling along ridgelines.  Cornice fall may trigger larger avalanches on the slopes below. 

    (3/12/2021) A snowboarder triggered a large avalanche in Klahhane Bowl on a N aspect around 6000' (run locally know as Holy Roller). The slide was triggered from the ridgeline and the rider was not caught. This large slide ran 1300' vertical feet covering skin tracks from earlier in the day. The crown was estimated at 2-4 feet deep. Photo: Sam Luthy

Avalanche Discussion

2-3 feet of snow accumulated last weekend in the Hurricane Ridge area.  Strong southerly winds generally eased off and temperatures cooled towards the tail end of storm cycle that wrapped up Monday morning.  Northerly shaded aspects held dry snow through Thursday while sunny slopes went through a daily melt-freeze cycle.  Convective showers added an inch or two of snow Wednesday.  Since then, daytime temperatures have steadily climbed (generally highs in the 40s) since mid-week, a trend that is expected to continue through the weekend.  Ample evidence of small wet loose avalanches and rollerballs were found on steep sunny slopes Thursday and Friday. The last crust (3/6) may be found under the most recent storm snow.  A human-triggered large slab avalanche was reported Friday in Klahhane Bowl - see the media reel for more info. 

Throughout February, we have been tracking a layer (mid-January crust/facet combo) deep in the snowpack that was responsible for some very large avalanches throughout the Cascades.  Unlike their Cascadian neighbors, this interface in the Hurricane Ridge area has not been active recently. The last observed avalanches down to the mid-January crust occurred in early February.  Observations on Thursday 3/11 indicated that this layer is between 5 and 6 feet down in the Hurricane Ridge area.  We will continue tracking this layer throughout the spring to see if it becomes a player again.  

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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