Boletín de aludes

Selkirk Mountains

Idaho Panhandle Avalanche Center
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Peligro de aludes

Fri
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 5 months ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Dense new snow and steady winds are building fresh, wind-drifted slabs above a mixed bag of older snow surfaces. These slabs will be the most reactive and dangerous where drifting is around a foot deep and the ensuing avalanche could grow large enough to take you for a ride or bury you. A pillowy looking snow surface and cracking in the snow are clues you are approaching a wind-drifted area and suggest retreating to lower-angled, more sheltered slopes.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Moderate to heavy snowfall and erratic but steady winds will continue to deepen and thicken fresh slabs at middle and upper elevations. 24-hour snow totals range 4 to 8 inches and now rest above either a firm crust or drier snow from earlier in the week. You may encounter places on sheltered slopes or those facing the direction of the wind with reactive storm snow, but the new snow will be deeper and more problematic on northerly and easterly-facing slopes. There, fresh slabs up to a foot thick could produce a larger and potentially more consequential avalanche.

    Fortunately, there are helpful clues and warning signs to help guide you around the most worrisome places. Pay attention to how much snow you are walking or riding through - if you find more than about 6 inches of new snow, stop and reassess because you are likely in an area with enough new snow to harbor drifting hazards. If the snow surface becomes stiffer, you barely make an impression on the surface, or the surface looks smooth and pillowy, you are likely in a wind-drifted area. If you hear audible collapsing or see fresh avalanches, pull back to lower-angled slopes away from ridges and limit travel below steep sidewalls of gullies.

Avalanche Discussion

Another fast-moving spring storm started delivering snow around 5,000 feet and above on Wednesday with mostly rain below that. Now that the low has moved inland, cooler air will be able to filter into the region and enhance snowfall rates. Depending on where bands of convective snowfall park themselves, snow totals have the potential to exceed forecast numbers. On the flip side, adjacent areas could see much less snowfall over the same period. It’ll be important to frequently monitor how much new snow has fallen and adjust your travels or how steep of terrain you’re  comfortable traveling in accordingly.

Fresh slabs forming on the surface are stacking up above a variety of old snow surfaces. Some places there is yet another crust below the new snow - either a sun or rain crust - while slopes higher in elevation and those more shaded likely harbor soft, dry snow below the most recent snowfall. Since this round of moisture arrived with warmer air and higher freezing levels than the last storm, this likely created inverted snow layering near the surface. Meaning, wetter or denser snow over softer or less dense snow and this setup is more prone to human or machine triggering than a right-side-up slab. 

While we don’t expect an avalanche to break very deep into older snow layers, places where there’s a foot of new snow or more could produce a slide large enough to cause trouble. Wind-drifted slabs can break wider than you expect and sometimes above you, and have the potential to span adjacent terrain features - especially where a broad, uniform crust lurks below. With winds in the perfect saltation range to drift snow onto leeward terrain features, expect thicker slabs in all the common spots - underneath ridges, on gully sidewalls, and around cross-loaded or convex rolls.

If the easterly surface winds overcome the predominant westerly winds aloft, there could be more significant drifting on atypical slopes that are westerly facing. Look for fresh cornice formation and pay attention to surface texturing along ridges to help provide clues to which slopes are more likely to harbor deeper, more dangerous slabs.

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IPAC is now on the Avy app! View, submit, and share observations on the go using the AvyApp. Your backcountry observations are critical for building our avalanche forecasts. Avy provides a centralized location for core trip planning, and you can view streamlined, up-to-date avalanche and weather forecasts for your selected zone, using offline caching. Download Avy today - App Store and Google Play.

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