Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

We're locked into a snowy pattern for the time being. Dangerous conditions should be expected at higher elevations, where more new snow and wind has drifted thicker slabs. Loose dry avalanches may run fast and far on steep slopes. Look for signs of instabilty like recent avalanches or whumphing collapses, and choose terrain with a conservative mindset. 

Problemi valanghivi

  • Wind Slabs

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

    Avalanches could be more cohesive at upper elevation where wind has created thicker slabs. Westerly winds blew on the 25th and 26th and created slabs near ridgelines and on exposed features. With some new snow on Monday, these slabs may get buried and obscured so they could be difficult to identify. On Monday the easterly winds will begin to blow through passes and cols, creating fresh, reactive soft slabs. Watch for drifts forming on cross-loaded features and gullies. Steer around large and obviously wind-loaded terrain near ridgelines and cliffs, especially if you find shooting cracks, whumphing collapses, or strong over weak structure. 

    In isolated areas, slabs could break surprisngly wider and deeper than expected due to layers of buried facets and/or a crust facet sandwich that was buried in mid February. Carefully assess the bond at recent interfaces, and how it changes as you travel. Use small test slopes and quick, informal tests to see how the snow reacts.

    (1/9/2023)

    Small test slopes like this can indicate unstable conditions and the presence of reactive wind slabs. 

    Photo: Irene Henninger

  • Loose Dry

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

    As cohesionless snowfall accumulates, you might find that dry loose avalanches become frequent on steep slopes. These could run far and fast on older weak snow surfaces and firm crusts at lower elevation. Larger and steeper pieces of terrain could produce slides that pack more of a punch. Especially be careful of gullies and similar places where debris could pile up deeply. 

    Example small dry loose avalanches during moderate snowfall from last week.

    Photo: Katie Warren

Avalanche Discussion

We're transitioning from westerly flow to southeasterly for the next couple of days. This pattern should bring accumulating snowfall to the east slopes with the upslope flow. The front that came through on Sunday brought 4-8" of new snow for the western half of the zone, and little accumulation in the eastern half. Observers reported some whumphing collapses and propagating test results on a crust from mid February (Valentines Day Crust) in the Icicle drainage on Saturday. Earlier last week an arctic front brought 8-12" of very low density snow to favored areas of the zone, including Mission Ridge and the Icicle drainage. All the snow from the past week sits over this Valentine's crust, which often presents as a crust/facet sandwich, with weaker snow beneath the upper crust. You can quickly dig into the top 2 feet of the snowpack to assess this older weak layer. 

If you get out into the mountains, let us know what you see by submitting a public observation. 

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