Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
4 · Forte
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Very dangerous avalanche conditions are expected to develop and last through Wednesday. Large and very large avalanches may run from higher elevations, and heavy storm slabs may run on smaller steep slopes at lower elevation. Stay off of, and well out from underneath steep slopes.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1.5–3

    We're expecting another couple feet of snow, and it'll come with warming temperatures and strong wind. The new storm slab will build on 1.5 to 3ft of weaker, low density from the past few days. Slabs could break within the new snow, at the old snow interface, or any number of layers down to a stout crust from early February. Slides that do break to these deeper layers could be over 4ft deep, widely propagating, and could run long distances downhill. Even small slopes and gully features near pass level could become dangerous with very reactive and heavy storm slabs. 

    Stay off of and out from underneath steep slopes at all elevations. Avalanches could run through openings in forested terrain, and may become very large. 

     

    Example storm slab from last month.

    Photo: WSDOT SCR

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    At and above 6,000ft, slides could break more deeply buried weak layers including weak snow and a crust from early February. These may be most likely in the eastern portion of the zone, where the underlying structure is weaker. Control work triggered some slides down to this layer on shaded aspects on Tuesday, and skiers have reported whumphing collapses on it in adjacent zones to the east the past couple of days. The heavy snow and wind loading with the storm will constitute an impressive loading event that'll test these deeper layers well. Now is not the time to go onto large steep slopes. 

    Stay off of and out from underneath steep slopes. Avalanches may propagate widely across terrain features, and run full path to lower elevations. 

    (2/26/2024)

    Example large avalanche that ran on the early February Crust from the West South zone.

    Photo: Crystal Mountain Pro Patrol

Avalanche Discussion

An impressive storm is just beginning to get underway as I write. This will add to and perhaps double the already impressive totals of 24-30" since Sunday. On Tuesday, multiple observers reported sudden planar test results with compression tests on small faceted grains above the early February Crust. These came in from Grace Lakes and Lanham Lakes, both profiles were on northerly aspects. Two large (D2+) natural avalanches were observed from the Camp Chutes off the south side of Rock Mountain on Tuesday. The timing of these are unknown, but estimated in the past 12-36hrs. The slides ran down to the bottom of the track (gullies) at least. A wide slab avalanche occurred on a SE aspect at 5,600ft in Highlands Bowl on Monday, this was triggered by a smaller sluff. That same day control work at SPMR triggered a few avalanches that broke down to the early February Crust.

Riding conditions have been excellent, but with the incoming warming storm it'll be time to let the mountains ride out the storm. The very dangerous conditions are expected to last through the evening and natural avalanches may continue well into the overnight period on Wednesday. 

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