Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Fri
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

High alpine terrain could hold fresh wind slabs Thursday. Be on the lookout for and bypass steep terrain with recently wind drifted snow. Lower elevations should be generally safe.  Continue to practice good travel habits and reassess your plan if you find conditions different than expected.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Strengthening winds in the afternoon should transport snow onto leeward terrain features. Slabs that do form should be easy to identify - observe the direction of blowing snow and take note of where it lands. 

    Widespread wind transport and slab formation are not expected at treeline - if you see otherwise consider avalanche danger a notch higher and take appropriate measures.

    If you end up in wind loaded terrain just navigate around convex or other steep features where you are more likely to find a slab. Wind slabs are easier to trigger during or immediately after active transport and loading periods.

    Actively blowing snow, freshly building sharp cornices, and textured surfaces. All easy-to-identify signs of wind-loading. Look for slabs to develop on the slopes on the left side of the picture.

    Photo: Dallas Glass

Avalanche Discussion

A shot of sun and warm morning temperatures could keep signs of instability in play until clouds thicken. The likelihood is low, but don't completely discount the idea of seeing a small avalanche or cornice failure (photo). Give a wide berth to steep slopes where you observe rollerballs, pinwheels, or small avalanches.

The west slopes and passes saw a bit less warming than expected with clouds hanging out in Stevens and Snoqualmie until midday. Observers in neighboring zones reported little in the way of wet loose avalanche activity. Plenty of rollers and other signs of instability were noted, but solar aspects only produced a few small avalanches. The current batch of wind slabs was thought to be dead in the water - but a single cornice triggered slab avalanche (observation) in very steep above treeline terrain was reported late Wednesday. No other slab avalanches were reported despite plenty of travel in steep wind loaded terrain.

Below the surface, 1-3’ of recent snow rests on the stout rain crust buried in mid-January. Interfaces between these newer layers have not produced avalanches or positive test results in a few days. Under the rain crust, there are layers of rounded grains interspersed with crusts from rain events this winter. Deeper weak layers are considered dormant but may wake up in the spring with extensive warming or very, very heavy loads,.

Régions couvertes