Boletín de aludes

East Slopes Central

Northwest Avalanche Center
Ver en el mapa

Peligro de aludes

Wed
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
Open full map
Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

With warming temperatures that lead to moistening snow surfaces, loose avalanches may run on steep slopes in the sun. You could still trigger a dangerously wide persistent slab 2-3ft deep at mid and upper elevations.  Consider using simpler, less steep, and more supported terrain while these dragons linger.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2–3

    Faceted snow over the Early February Crust (EFC) is the weak layer responsible for numerous close calls throughout the eastern Cascades and a fatal avalanche accident near Darland Mountain on Friday.  These avalanches are failing 2-4ft deep, propagating widely, and being remotely triggered from low-angle terrain below or adjacent to steep slopes. A smaller avalanche could also step down to this layer. Signs of instability can be inconsistent, creating a tricky problem that is essentially 'unmanageable'. You might not receive signs of instability before the whole slope fails. It could be the 2nd, 3rd, or 8th person on the slope that triggers it. 

    Strong sun has the potential to increase the reactivity of these slabs on steep slopes that face SE-SW on Tuesday.

    Consider avoiding slopes steeper than 30 degrees, and stay well out from underneath slopes of that angle. Give larger terrain features wider safety margins than you normally would. At lower elevations, we don't have enough slab over the weak layer for this to be a consistent problem. 

    (3/2/2024)

    You can trigger large avalanches like this on Sunday. This avalanche would easily be large enough to bury or kill you. 

    6600 ft, NE aspect in the East- South zone.

    Photo: Katie Warren

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Direct sun and slightly warmer temperatures may create wet loose instability on steep slopes. You can anticipate this problem by considering your aspect vs. timing of when you might be on any given slope. Look for signs of instability, like small rollers falling out of trees or small fan shaped slides. Feel for moistening snow surfaces on slopes in the sun. You can use test slopes to check and see how any given area might react. These slides should remain small, but may be able to entrain more than you'd think, especially in larger terrain features. 

Avalanche Discussion

Tuesday should be another beautiful day in the mountains with mostly sunny skies that could cloud up later. We're expecting slightly warmer temperatures than Monday, and that strengthening March sun will start to have more of an affect by the day on the slopes. Surface conditions are still excellent powder, steeper SE-SW aspects may hold a thin crust that'll melt down early in the day and might become moist and heavy by afternoon.

Over the past week, forecasters and observers throughout the Wenatchee Mountains, the Teanaway, Salmon La Sac, and near Leavenworth have all found a weak snowpack structure. Snowpack tests consistently produce results that indicate triggering a persistent slab avalanche is likely. Observers in the Icicle on Sunday saw a crown that we suspect ran on the EFC. In the Teanaway drainage on Friday, group of snowmobilers remotely triggered a large avalanche. This avalanche occurred on a ENE aspect at 6400 ft and broke 1-2’ deep ( observation here). Another large, natural avalanche near Van Epps Pass occurred earlier this week. 

Our snowpack is complicated due to the intermittent dry spells in February. There are also potential layers of surface hoar and faceted grains from the 14th, 18th, and 24th. Widely propagating avalanches could fail on any of these layers. Approach the mountains cautiously and enjoy some low-angle powder until these weak layers gain strength. But be patient, as it could be a while before we see improved snow stability. 

This pattern of persistent slab problems can be incredibly challenging for backcountry decision-making. It takes extremely conservative terrain management and patience. This winter's lower-than-average snowfall and warmer-than-average temperatures contribute to a shallow snowpack prone to developing these tricky weak layers. The issue is especially apparent in the eastern Cascades, which, on a typical year, is already a bit shallower and weaker than areas west of the crest. So, if you're venturing into these eastern zones, be prepared to take a step back in your typical terrain selection and understanding of the snowpack.

Thanks to everyone who submitted observations over the weekend. It really helps us track the snowpack and avalanches during these active periods. 

Regiones cubiertas