Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Keep your terrain selection dialed back as a cool, snowy pattern continues. Expect dangerous conditions at higher elevations, where the new snow is deepest and you're more likely to trigger a slab. Loose dry avalanches may entrain a surprising amount of snow on steep slopes at all elevations. Look for signs of instabilty like recent avalanches, shooting cracks, and whumphing collapses as you travel.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Avalanches could be larger and more easily triggered at upper elevation where wind has sifted the deep new snow into slightly more cohesive slabs. Easterly winds blew on the 27th, and may have created slabs on open exposed terrain. With some new snow, these slabs may get buried and obscured so they could be difficult to identify. On Tuesday morning, the winds shift back to westerly, and could create fresh reactive soft slabs near higher ridgelines. Watch for drifts forming near exposed areas, below large rock outrops, and near cornices. Steer clear of large and obviously wind-loaded terrain right near ridgelines and cliffs, especially if you find shooting cracks, whumphing collapses, or a strong over weak structure. 

    In very isolated areas, slabs could break wider and deeper than expected due to layers of buried facets, and a crust facet sandwich from 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.

    (2/27/2023)

    Shooting crack in wind affected snow near Fortune Pass.

    Photo: Katie Warren

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    As cohesionless snowfall accumulates, you might find that dry loose avalanches become frequent on steep slopes. These could entrain a fair amount of low density new snow, and pile up to be deep in some areas. At lower elevations they could run on older weak snow surfaces and firm crusts. Larger and steeper pieces of terrain could produce slides that pack more of a punch. Especially be careful of rock lined couloirs, gullies and similar places where debris ends up.

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

    Photo: Katie Warren

Avalanche Discussion

Another round of easterly flow is in store Monday night into early Tuesday, before the winds switch back to west. This pattern should continue to favor the east slopes with upslope flow leading to favorable snow totals. Forecaster Katie Warren was in the upper N Fork of the Teanaway on Monday and reported about a foot of new snow since the 25th. Snow was generally well bonded to this interface, but would fail in tilt tests. A front  came through on Sunday, bringing 4-8" of new snow for the western half of the zone. Over the weekend, observers reported some whumphing collapses and propagating test results on a crust from mid February (Valentines Day Crust) in the Icicle drainage. 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 find this layer 1-3ft down in the snowpack.

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

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