Lawinenlagebericht

Banner Summit

Sawtooth Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Triggering a large avalanche is most likely in wind-affected terrain and possible in areas generally protected from the wind. Your odds of triggering a slide increase as you climb in elevation or move to slopes that face away from the afternoon sun. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1.5–2.5

    You're most likely to trigger a large avalanche where dense slabs rest above weak, faceted snow and crusts. Observed avalanche activity during our recent storm focused on N-NE-E-SE facing slopes at middle and upper elevations. These areas received the most snow and harbor the weakest crust + facet combinations.

    While obviously wind-loaded terrain is the most dangerous, triggering an avalanche is also possible in steep, wind-sheltered terrain. Use your boots, hands, or poles to quickly check for "old snow"—crusts and/or weak, sugary facets—beneath the more recent storm or wind-driven snow. 

    Cracks shooting out from you and "whumpfing" sounds as the snowpack collapses are red flags that indicate unstable conditions. Avoid all steep slopes where you experience these obvious signs of instability. You may be able to trigger avalanches remotely—from gentler terrain above, below, or to the sides of steep slopes.

    (12/8/2025) Large avalanches on E facing upper elevation slopes on McDonald Peak in the southern Sawtooth Mtns. 

    Photo: Ben VandenBos

Avalanche Discussion

The Banner Summit Zone picked up 2-2.5" of SWE (snow-water equivalent) during our last storm from December 5th-9th. This precipitation likely fell as both snow and rain well into upper elevation terrain, creating dense slabs in both windy and sheltered areas. Observations from across the forecast area are limited, but similar storm totals and preexisting snowpack structure led to naturally releasing large and very large avalanches in the Sawtooths to the south. 

Stability will gradually improve as the snowpack adjusts to the recent load, but this process can be slow and variable from slope to slope. Yesterday, we observed snowpack collapsing, cracking, and unstable snowpack test scores near Galena Peak. Obvious signs of instability like these made it an easy decision to stick to lower-angle terrain and slopes without obvious facets beneath the storm snow. Today, be on the lookout for these same clues and heed their warning by traveling conservatively. 

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