Lawinenlagebericht

Banner Summit

Sawtooth Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Sat
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
Open full map
Veraltet — dieser Lagebericht ist 6 months ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Over a hundred avalanches released naturally on Tuesday night and Wednesday. You can still trigger a large avalanche on many slopes where the wind formed drifts or stiffened the snow surface. Triggering avalanches is also possible on steep slopes that are mostly sheltered from the wind. You may be able to trigger slides remotely—from flat terrain below, above, and to the sides of steep slopes. Beware of small wet avalanches releasing on their own on very steep, sun drenched slopes.  

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    2–2.5

    Yesterday, snowmobilers remotely triggered a Persistent Slab avalanche near Bull Trout Lake (photo to right/below), and riders remotely triggered cornices and slabs beneath them on Osberg Ridge south of this zone (details).

    You're most likely to trigger a wide, 1.5-4 foot thick slab avalanche on steep slopes that tilt away from the afternoon sun (NW-N-NE-E-SE) where you find wind drifts, slabs, or wind-stiffened snow at the surface. Avalanches could fail on multiple weak layers (facets, surface hoar, crusts + facets or surface hoar) buried by the series of February storms. While wind-loaded terrain is most widespread at upper elevations, Wednesday's strong W-NW winds formed slabs or stiff snow surfaces on more middle and lower elevation slopes than usual.

    Persistent Slab avalanches can release in surprising ways:

    •  They can be much wider than expected (view many recent examples here).
    • They can break above you and pull into relatively gentle terrain.
    • You can trigger them remotely—from flat terrain below, above, and to the sides of steep slopes.  

    Watch for dunes, waves, and textured surfaces created by wind. Wind-driven snow and slabs feel stiff. Snowpack cracking and collapsing are clear signs of unstable conditions.

    Unfortunately, the best way to avoid trouble is to give avalanche terrain a wide berth. This includes gentler terrain below and above steep slopes. 

    (2/26/2026) Snowmobilers remotely triggered this slab avalanche on Thursday, Feb 26th near Bull Trout Lakes in the Banner Summit zone. Note how the crown pulled into very gentle terrain that would not seem dangerous if you were at the top of the slope. NW aspect near 7600'. 

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2

    Over a foot of recent snowfall and strong wind built 1-3 foot thick drifts and slabs, predominantly at upper elevations. You could trigger avalanches where obvious weak layers do not exist beneath the slabs. Expect these drifts to be the largest and most sensitive on slopes facing N-NE-E-SE. 

    Look for them near or below ridgelines, along mid-slope ribs, and on aprons beneath chutes. Fresh cornice growth, dunes, and drifts are all signs that the wind has been at work. If you suddenly feel the snow surface getting stiffer, you've found a wind slab. 

    These slides are formidable on its own and may also serve to trigger the larger and more dangerous Persistent Slab avalanches described above.

    (2/25/2026) A pair of large natural avalanches on a NE aspect at 8800' along the ridgeline between the two Copper Mountain summits. Clear evidence of wind loading and cornice growth is obvious in this photo as well.

    Photo: Sawtooth Avalanche Center

Avalanche Discussion

Persistent Slab problem: The last storm produced extensive natural avalanche activity (view chart and Avalanche occurences). Yesterday's remotely triggered slides near Banner Summit and Osberg ridge are bullseye evidence that the well-developed facets, surface hoar, and crusts + facet/surface hoar combinations buried by the February storms will take time to adjust to the load. 

These avalanches are most likely on NW-N-NE-E-SE middle and upper elevation aspects, but sunnier aspects and lower elevation terrain is tricky, too—be careful out there:

Wet Loose problem: Yesterday, we saw 10-15 fresh, small, natural wet loose avalanches. They released in the afternoon on steep, upper elevation slopes facing W, W-NW, and W-SW. Today, expect another round of relatively small, natural wet loose avalanches. With warmer temperatures and less wind, activity could spread to SE, S, and SW aspects in addition to W and W-NW facing terrain. Very steep, wind-sheltered slopes where the snow surface is not wind-hammered or hardened are most likely to produce wet avalanches. Don't linger below large, sun-drenched avalanche paths. 

Abgedeckte Regionen