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
3 · Marcato
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In sintesi

7a Update: High Danger. Overnight strong wind and heavy snow will make it easy to trigger large avalanches near and above treeline. Avoid being on or under slopes over 35 degrees where the wind has drifted recent snow into deeper slabs. If the new snow slides easily in snowpack tests or recent avalanches at any elevation, stick to lower-angle slopes.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1.5–2.5

    Avoid being in or under avalanche terrain on leeward, wind-loaded slopes near and above treeline. Theses will be the most dangerous areas and avalanches in these could be deep and very large. Use your probe to feel for stiffer, deeper drifts to indicate wind-loaded slopes. The easiest way to stay safe is to stick to slopes under 35 degrees. If you see recent avalanches or cracks shooting through the snow stay on well-protected, low-angle slopes.

    Look for stiffer snow over softer snow as an indicator that you can trigger storm slab avalanches. Use smaller, low-consequence test slopes to check how easily the snow slides. You can make many quick, informal tests as you move through the terrain.  Look at the interface that was buried at the beginning of this storm, about 1.5 feet below the surface. If you find sudden or propagating test results on the older, weak snow, stick to lower-angled slopes. If the sun warms the surface snow, you may see small loose wet avalanches on steep southerly aspects. 

    (2/7/2023)

    Easy, planar tilt test results at the Feb 3rd interface. You may still be able to trigger avalanches at this interface 1-1.5ft deep. 4,400ft, NW, Lanham creek. 

    Photo: Matt Primomo

Avalanche Discussion

By Wednesday morning, Stevens Pass picked up another 2" of water equivilent in just over 24hrs. Westerly winds are strong and gusty this morning. Both winds and precip should taper off quickly.

On Tuesday, Stevens Pass ski patrol triggered numerous slab avalanches in steep terrain, both wind-loaded and sheltered. The largest avalanches (size D2) were on leeward, wind-loaded slopes. NWAC forecaster, Matt Primomo, went to Lanham creek where he found that it was also easiest to initiate cracks and snowpack tests on leeward slopes near treeline. 

Weak snow (near-surface facets) was buried at the beginning of this storm on February 3rd. The recent cold and dry weather formed weaker snow around crusts in the upper snowpack. One, from January 27th, found at mid-elevations, is thinner and more brittle and buried just over 2 feet below the surface. A more stout, clear ice lens that formed around the MLK holiday weekend, is buried about 3 ft below the surface. We haven't seen avalanches occur on these layers. 

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