Bollettino valanghe

Olympics

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

A shallow shed cycle continues on Friday. These avalanches can occur anywhere you find moist snow at the surface or a crust breaking down due to warming. Small avalanches will be most impactful on steep open slopes above cliffs, gullies, or trees.

Problemi valanghivi

  • Loose Wet

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

    Friday is likely to be the warmest and sunniest day of this high-pressure ridge, with the potential for less wind to cool the snow. A shallow shed cycle will continue on all aspects with more rollerball activity. The risk for wet loose avalanches large enough to take you for a ride is heightened in areas where the surface snow has yet to warm up. This is primarily on shaded aspects at upper elevations. We're not convinced the sun angle and temperatures will be high enough to impact due N, but shedding snow off cliffs exposed to direct sunshine could entrain surface snow on the slopes below as they start to moisten. But with enough warming, avalanches large enough to take you for a ride are possible on most aspects at middle and upper elevations. Use small steep test slopes to see if you can get snow moving and reduce your exposure to open slopes steeper than 35 degrees if rollerballs start to entrain snow. One piece of good news is that the last round of snow came in dense and warm, somewhat limiting the size potential of avalanches on W-S-E aspects and at lower elevations.

    Example: Wet loose avalanches often initiate where snow sheds off rocks and trees onto the slope below. Note that there are both small rollerballs and wet loose avalanches in this image. 

    Photo: Zack McGill - Cascade Mtn Ascents

Avalanche Discussion

ONP Rangers in the Hurricane Ridge area found heavy, warm, and sticky snow best described by the highly technical term "schmoo."  A storm system Monday night into Tuesday deposited an average of 14" of snow at middle elevations. The system arrived with strong winds, so these deposits are deeper in some wind-loaded N and E aspects, while ridges are often scoured to grass, dirt, or rocks. The surface snow moistened on all but upper elevation shaded aspects thanks to above freezing temperatues and partial sunshine Wednesday and Thursday. On N aspects, the post-storm warmup has created 6" of denser (upside down) snow that makes riding quality poor and trailbreaking more difficult. On W-S-E aspects, the upper snowpack is right side up. The snow everywhere is fairly glued in and wasn't responsive to rider trigger. Although there was plenty of rollerball activity, it was all very superficial. The big question for Friday is whether a few more degrees of warming and a bit less wind will increase the depth of the warming within the snowpack or moisten previously dry snow on upper elevation N aspects.

Below the new storm snow, exists a 2/23 rain crust (that is gradually refreezing), a few inches of dense snow below that, and then the 2/22 crust from the atmospheric river event. We're watching the 2/22 crust interface which was still reactive to shovel shear tests on Thursday. This reactivity remains a small possibility until the 2/23 crust freezes fully.

An avalanche on a NW aspect on Steeple Rock (photo in the gallery) may have run on the 2/22 interface. The vertical and sharp nature of the flanks suggests that the slab involved moist snow, potentially from warming after the storm. This slab activity could have run down to the 2/22 interface. Three avalanches in N Bowl (size 1.5) show storm-related and potentially wet slab activity associated with Monday's storm. The crowns are filled in to varying degrees, suggesting that they occurred at different phases of the storm cycle.

It remains wise to take a look at the 2/22 interface before committing to any larger open slopes. While we don't expect any additional activity on this interface as the upper snowpack continues to strengthen, but we can't entirely rule out the possibility.

Share your observations with the community and NWAC. Even if you didn't see an avalanche or a snowpack test, your information is incredibly valuable.  Every afternoon, 4-5 NWAC forecasters from around the region meet to discuss the latest snowpack and avalanche observations, and weather forecast to create the next day's avalanche forecast.  We look at information from the public, other snow professionals, and weather station data to round out our picture.  Share early and often!

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