Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

You could trigger a wind slab avalanche in upper elevation terrain—identify and avoid slopes with evidence of wind drifting. As the day warms up, small loose snow avalanches could occur on very steep slopes that face the sun. Generally stable conditions exist on slopes that are protected from the wind and sun.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Since Thursday's 8-10" of new snow, N-NW winds have been blowing fairly consistently—including yesterday and overnight. These winds have been transporting snow and building slabs atop weak snow surfaces (facets, crusts, surface hoar) that formed during our ongoing dry spell. 

    Yesterday, a group triggered two wind slabs south of Copper Mountain on steep, upper elevation, northerly aspects. Both of these broke wider than your "run of the mill" wind slab due to the weak underlying snow. These slides were 6-18" thick and broke 40-100' wide.

    While these wind slabs probably won't bury you, they're too big to tangle with. They could easily take you for a ride, pile you into trees, or wash you into a terrain trap. The possibility of wind slabs breaking wider than expected makes them less "manageable" than they normally might be. The best approach is "identify and avoid." Northerly winds often blow upslope, creating unusual loading patterns. So you may find wind loading along south-facing ridges, but you may also find slabs mid-slope in wind-exposed terrain.  Keep your eyes peeled for evidence of wind drifting, changes in snow texture, and denser/stiffer snow at the surface.

    (1/22/2022) North winds following Thursday's 8-10" of new snow created sensitive wind slabs. These are failing on weak snow surfaces that formed during the ongoing dry spell. This natural wind slab avalanche released Friday or Saturday south of Copper Mountain.

Avalanche Discussion

The wind slab problem described above is front and center today, but there are a few other problems to keep in mind:

  • Wet loose avalanches. Thursday's new snow fell on top of slick crusts on slopes that face the sun. Small wet loose slides have been reported in three out of four zones, including Banner Summit (photo). Today's warm temps and sunshine will produce the possibility of more wet sluffs. These could occur naturally as the day warms up—pay attention to the terrain above you.
  • Cornices. Use extra caution around cornices, which—thanks to a very snowy/windy December—have grown exceptionally large this early season. Many observers have noticed cracks near larger cornices where these beasts are peeling away from steep ridgelines. Stepping through the surface snow into one of these cracks can lead to an awkward moment indeed.

Catch up on what happened (or didn't happen) this past week in Scott's latest Weekend Update.

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