Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Soaring freezing levels and the strong April sun will rapidly thaw the recent storm snow on Wednesday. You will encounter a variety of dry and wet snow avalanche problems, any of which could grow large enough to bury, injure, or kill a person. These are dangerous and unusual conditions; build in a wide margin for error and consider avoiding avalanche terrain altogether.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Wednesday could be a very tricky day with rapidly changing conditions and increasing potential for wet avalanches. The most dangerous conditions will develop on E-S-W aspects in direct sun, but you may encounter wet snow on any slope below treeline by afternoon. Avalanches will run naturally and will be easy to trigger on slopes 35 degrees and steeper. These avalanches may start small and shallow but could grow large and gouge deeper as it continues to heat up. Wet loose slides in motion could even trigger slabs resulting in surprising avalanches. The snowpack will need time to adjust to these dynamic conditions. Choose simple terrain away from large avalanche paths by the time you see rollerballs, pinwheels, and snow shedding from trees, rocks, and cliffs.

    Example photo of wet loose avalanches similar to what we expect on Wednesday.

  • Wind Slabs

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

    Ongoing snowfall and wind-loading since Sunday built fresh slabs 1-3ft thick with higher amounts close to the Cascade Crest. Thickest and most reactive slabs linger at upper elevations on easterly aspects. Avalanches could break on the new/old snow interface (Early April Crust) or within new and wind drifted snow. The warm-up Wednesday adds uncertainty, and cornices could also fall acting as huge triggers on slopes below. Pay attention as you transition into wind-affected terrain, and continue to avoid steep, unsupported slopes with evidence of fresh wind loading. 

    (3/18/2022)

    Example of a wind slab near Darland Mountain. 

    Photo: Andrew Kiefer

Avalanche Discussion

Wednesday will be a jarring transition from winter back to spring. The primary avalanche concern will shift from dry snow to wet snow as it heats up throughout the day. This will not be the average wet loose cycle you usually see on the first sunny days following a storm. These conditions are out of the ordinary, and a very good recipe for avalanches due to:

  • The depth (1-3ft) and cold, low-density quality of new snow
  • 5500ft jump in freezing levels (1500ft rising to 7000ft)
  • Intensity and duration of the sun this time of year

We have a significant amount of uncertainty about how this day will play out. Don’t box yourself in by choosing routes that require you to travel through avalanche terrain to exit. As the warm temperatures increase Thursday, our uncertainty grows and so does the potential for larger and more deadly avalanches. 

 A shallow, patchy snowpack exists in the southern and eastern areas of the zone, even on shady northern aspects. Some southern slopes are snow-free up to 5700ft. Use extra caution in these lower elevations where hidden obstacles may be lurking just under the new snow, and creek holes may become drifted over or hidden.

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