Bollettino valanghe

Olympics

Northwest Avalanche Center
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Pericolo valanghe

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

It's been a week since multiple human-triggered avalanches involved a weak interface at Hurricane Ridge. We suspect the setup for these avalanches lingers on isolated shaded slopes. If you choose to take on the low probability but an elevated consequence of steeper open slopes, select smaller features with clean runouts.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2

    Persistent slab problems have a peak and then a long tail. The peak was last weekend and we're in that long tail. They typically come with a lot of uncertainty and the problem at Hurricane Ridge is no exception. Shaded aspects are where you might still be able to trigger a large or surprising avalanche. While we think the odds are decreasing, this is not a typical setup at Hurricane Ridge and it warrants your attention. The problematic snowpack structure is where you find the recent snow at 4-finger hardness or greater with an underlying weaker layer of sugar-like facets. 

    Whumping collapses remain the most telling sign of unstable snow and the best clue that you should stick to terrain under 35 degrees. If you hear or feel such a collapse within the snowpack, keep a large margin away from steeper slopes. The safest option for this problem is to avoid it altogether by staying on low-angle terrain or moving to other aspects. Any wind loading or surface slab formation on Saturday will increase your chance of triggering such an avalanche.

    If you don't find a slab above the January Drought Layer (JDL) crust complex, then it may be reasonable to move onto steeper terrain features, recognizing that the overlying structure could change across the slope. Try to avoid larger rollovers and slopes above terrain traps where your odds of surviving an avalanche would be reduced.

     

    (2/1/2025)

    Human triggered soft slab avalanche (10" deep) on West facing Avalanche Face adjacent to the Hurricane Ridge Ski Area. 

    Photo: NPS

Avalanche Discussion

If you travel in other parts of the Olympic Mountains, higher storm cycle totals could have formed a more pervasive slab, which would increase your probability of triggering and the consequences of triggering an avalanche. Heed the same advice in the persistent slab problem, but approach the terrain with added skepticism, preparing to dial back your terrain selection even further if what you find isn't right side up and cohesionless.

Since last Sunday, Hurricane Ridge has received 2-3" of new snow. The last round of moisture arrived Wednesday night and delivered 6" of snow at 1000-3000 ft, but far less at higher elevations.  

Olympic NPS Rangers traveled to the west side of Mt Angeles on Thursday. They found around 1.5 ft of right-side-up snow above the older weak snow surface (January Drought Layor or JDL). In those locations, they did not find a slab on the crust. Dry loose avalanches were not running much, but should be on your radar if you engage with very steep terrain. The last significant avalanche activity occurred last weekend. We have 6 reported human-triggered avalanches, 2 or 3 of which were likely persistent-type avalanches that surprised people by how they wrapped around terrain features. See many of these observations here. The style of several of these avalanches has us concerned that where the right combination of wind loading and weak underlying snow exists, a rider could still trigger such an avalanche with similarly significant consequences.

January ended on a wet note, the opposite of what was a remarkably dry month.  The height of snow at Hurricane Ridge increased from 44" on January 31st to 60" as the storm cycle waned at the Ridge by February 3rd.  Lower elevations saw warmer temperatures and rain up to 4000-4500' on 1/31 and are less likely to have surviving weak snow layers or significant new snow avalanche concerns.  Prior to this storm in the Hurricane Ridge area, a stout ski-supportable crust could be found on steep southerlies. On shady aspects, a skiff of weak snow could be found over a breakable crust. Weak, faceted snow could also be found between several crusts in the upper snowpack.  The new snow has vastly improved travel but be aware of travel hazards still lurking beneath the new snow; stumps, rocks, glide cracks, open creeks, etc may be hidden at lower elevations or aspects that were melted prior to 1/31.

Your observations help us build the next forecast.  Share what you see with us and your local backcountry community.

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