Boletín de aludes

Banner Summit

Sawtooth Avalanche Center
Ver en el mapa

Peligro de aludes

Mon
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
Open full map
Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You're most likely to trigger avalanches on slopes where the wind has formed drifts or stiffened the snow surface. Large avalanches are also possible in steep, wind-sheltered terrain and at lower elevations. Avalanches may be triggered from long distances away from steeper slopes. Smaller loose snow avalanches may release this afternoon on steep slopes that face the sun. 

Problemas de aludes

  • Deep Persistent Slabs

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

    Triggering a 2-4' thick slab avalanche is possible on steep slopes. Persistent weak layers (sugary facets, surface hoar, or crusts) exist on most aspects and elevations. Weak snow is common in our region, but the widespread nature of this weak layer is unusual. Extreme wind over the Solstice reshaped the upper snowpack, thinning (scouring) some areas and building thick hard slabs in others. You're most likely to trigger one of these slides in recently wind-affected terrain. 

    The stiff slab of snow overlying the weak snow near the ground means you are not likely to experience obvious signs of instability like snowpack cracking or collapsing. However, if you do find the "sweet spot" remember that you could trigger slides remotely—from gentler terrain above, below, and to the sides of steep slopes. These avalanches may break wider than expected or higher on the slope above you. 

    Unfortunately, avoiding slopes steep enough to slide is the only way to effectively manage this problem. While your odds of triggering a large avalanche are decreasing, the consequences of triggering one are not. Sticking to lower-angled, wind-sheltered slopes is a tactic to effectively reduce your risk.

    ADDITIONAL DISCUSSION: Today's warm weather combined with possible afternoon sunshine may release loose snow avalanches on slopes that face the sun. These should be fairly small but may pile debris deep enough to be of concern below large slopes or channeled terrain. 

    Significant complexity exists in our snowpack. Read the Forecast Discussion below for more details.

    (12/12/2022) In the Banner Summit zone, the weak November snow is buried beneath a 3' thick dense slab. 

Avalanche Discussion

UNCERTAINTY, UNPREDICTABILITY, COMPLEXITY, and YOU

I'd love to be able to give you the gift of a simple, stable snowpack for Christmas. Instead, you'll have to settle for this Christmas poem and some well-above-average temperatures... I guess we rarely get exactly what we want. We roll into Christmas with a significant amount of "weirdness" in our snowpack. I'm not sure there is a better way to put it. The past week delivered frigid temperatures, wind gusts in the 100s MPH, and now rising temperatures hovering near and above freezing. This whiplash-inducing weather is keeping the snowpack on edge and is creating significant uncertainty and unpredictability for us as forecasters and backcountry travelers. 

Let's take a broad look at our snowpack, from top to bottom:

  • UPPER: strong to extreme winds and new snow built stiff, hard drifts in many locations and produced a widespread avalanche cycle just 4 days ago. Additional snowfall and lighter winds built another round of softer slabs on top of these drifts and masked some of the older drifts. Warm temperatures and direct sun today will bring on the chance for small wet snow avalanches and will be changing the properties of the snow in the upper snowpack. Sound complex? Read on.
  • MIDDLE: several layers of surface hoar, facets, sun crusts, and even a rain crust sit 6-24" below the snow surface. In my travels the past two days, I experienced collapsing involving these layers and repeated unstable snowpack test scores (observations here and here, photo here). Some of the wind slabs that were deposited earlier this week broke wider than you might expect, indicating the involvement of one of these weak layers.
  • LOWER: everything I've described above is taking place on top of a widespread layer of weak snow. This layer is impressive, both in the number of avalanches it has produced already (hundreds and hundreds) and in its widespread nature (it exists just about everywhere). Snowpack collapsing is decreasing in frequency, but we have yet to go a day without a report of large, booming, rumbling collapses. On steeper slopes these collapses would result in avalanches. 

How do we deal with this messy picture? I will echo the great advice that Ethan gave you yesterday: your best bet is to remain conservative in your terrain selection. We aren't trying to scare you and we aren't trying to prevent you from having fun. Our goal is to help you get home safely at the end of the day.  Help us to help you by letting us know what you are seeing out there. Thank you, and Merry Christmas. 

Regiones cubiertas