Bollettino valanghe

Banner Summit

Sawtooth Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

The combination of recent snow and wind are creating dangerous avalanche conditions at all elevations. You could trigger avalanches involving just the recent storm snow or very large avalanches that fail on weak layers deep in the snowpack. Human-triggered avalanches are most likely in recently wind-loaded terrain but are also possible in areas that are more sheltered from the wind. 

Tragically, a snowmobiler was killed in an avalanche yesterday in the Baker Creek drainage of the Smoky Mountains. We extend our heartfelt condolences to the victim’s friends and family.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Yesterday on Galena Peak, I observed freshly forming wind slabs in the Boulder Mountains. Looking across to the Smokys and over into the southern Sawtooths, it was apparent that the wind was having the same effect. Weather stations across the forecast area reported a noteworthy bump in wind speed overnight, even at lower elevations.

    Today, expect to find multiple generations of wind slab. While some drifts may be obvious, older wind slabs may be obscured by shifting wind directions. Because of this, it’ll be harder than normal to pick out loading patterns. You’re most likely to find sensitive slabs at upper elevation, but moderate to strong wind has also built fresh slabs right down to the valley floor. 

    Be alert to obvious signs of instability such as nearby recent avalanche activity or cracks shooting from your boards or sled. Wind-drifted areas are also where you’re most likely to trigger the larger, more destructive persistent slab avalanches that are described below.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    As skies cleared yesterday we were afforded the opportunity to witness the aftermath of multiple days of heavy snow and strong wind. Dozens of very large avalanches were observed near Copper Mountain and the Sawtooths. Large avalanches were also seen near Galena Summit and in the Soldier Mountains. It’s likely that the majority of these very large avalanches broke on persistent weak layers near the middle and bottom of the snowpack. 

    Although the snowfall has slowed continued active wind-loading will keep the snowpack on edge. Although you’re most likely to trigger a persistent slab in recently wind-loaded terrain, don’t let your guard down on apparently sheltered slopes. Recent strong wind and settling within the heavy load of storm snow has stiffened recent snow into a cohesive slab in many locations, including low elevation terrain. 

    Avalanches failing on persistent weak layers can break wider than you expect, spanning terrain features and changes in aspect. These slides may be triggered remotely — from gentle terrain above, beneath, or to the sides of steeper slopes.

Avalanche Discussion

A snowmobiler was killed in an avalanche yesterday, January 15th, in the Baker Creek drainage approximately 0.5 miles northeast of Baker Lake. Two snowmobilers were caught in the avalanche on a S-SW aspect near 9000 feet in elevation. One of the riders escaped the avalanche, located his fully buried partner, and removed snow to clear the buried person’s face. The partner and professional rescue personnel were unable to revive the victim. We extend our heartfelt condolences to the victim’s friends and family. USFS Sawtooth Avalanche Center staff plan to visit the site as conditions allow and post a report in the following days. 

Very large avalanches in the Soldiers, Smokys, Sawtooths and near Banner Summit in the last 5 days are plain evidence that we pushed the snowpack to its limit. While these monsters are much less likely today, the lack of any real break from wind-loading will keep the snowpack on edge. 

Multiple rounds of snowfall and shifting wind direction have painted slabs on many aspects. In most locations, these slabs sit atop widespread weak layers of snow near the middle and bottom of the snowpack. Last night’s moderate to strong SE wind will continue to build fresh wind slabs throughout the day. This evening another round of snowfall and gusty wind may spike the danger after dark.

No matter how you look at it, all of this adds up to dangerous avalanche conditions in many areas. Expect this to be the case until this prolonged stormy weather lets up giving the fresh wind slabs time to heal and the underlying persistent weak layers a chance to adjust to the new load.

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