Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Natural and human-triggered loose snow avalanches are possible on very steep slopes receiving direct sun. These slides are most likely in wind-sheltered terrain during the heat of the day. Human-triggered avalanches are possible on steep slopes with slabs of wind-drifted snow. These slides could be 1-2 feet thick and large enough to bury you. 

Avalanche problems

  • Loose Wet

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

    Loose snow avalanches are possible during the heat of the day. They often originate near warm cliff bands and rocks on very steep slopes that directly face the sun. They begin at a point and fan out to collect debris as they move downslope. They are commonly small but can really pack a punch in large or confined terrain.

    Watch for obvious signs that the warm sun is wetting the surface of the snow. Thinly covered rocks and cliffs are the first areas to shed. Small roller balls or pinwheels of moist snow can be an early warning that loose snow slides may follow. Pay attention to what's above you. You can largely avoid this problem by sticking to colder, shaded aspects or lower angle terrain.

    (4/6/2022) These wet loose avalanches occurred in the Sawtooth Mountains on Wednesday, 4/6/22. The slides pictured started on S/SE facing slopes around 9,500'. Many other similar slides were observed in the range.

  • Wind Slabs

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

    Expect to find wind slabs at middle and upper elevations. Some of these wind slabs could be over 2 feet thick. Many of them formed above icy melt-freeze crusts, some of which will be sensitive to your weight. At upper elevations on the northern quarter of the compass, slabs overlie a few different weak layers in the upper portion of the snowpack. Any slide that breaks on these weak layers will be larger and more destructive than a simple wind slab (photo).

    Tuesday, Scott came across the debris of a small, but wide slab avalanche near Cape Horn Summit (photo). The avalanche released naturally during the storm on a wind-loaded, middle elevation slope. This was not an "average" storm. Up to a foot of snow fell in this area on Monday. Very strong wind redistributed the snow into drifts and slabs on many slopes (photo at right, below). Expect to find these slabs in both obvious locations (such as near ridgelines) as well as in atypical locations like the side of mid-slope gullies and lower on slopes.

    You can greatly reduce your odds of triggering a slab avalanche by sticking to terrain that is sheltered from the wind. If the snow you're traveling through becomes deeper and denser you've found a fresh slab. Cracks shooting out from in front of your skis or machine are clear indications that the slab you found is unstable. 

    Recent strong winds cross-loaded the sides of gullies, scoured some areas, and created surface dunes and ripples in most exposed middle elevation terrain near Banner Summit.

Avalanche Discussion

HEATING UPThe rollercoaster of hot and cold weather continues. It'll be warm today and we'll see near record-breaking heat tomorrow. The good news is that it's short-lived. Another cold front slams into the forecast area on Saturday and next week is looking cool and stormy. Wet avalanches are quickly supplanting wind slabs as our primary concern.

WET LOOSE AVALANCHES: Yesterday, Ben observed numerous wet loose avalanches in the Central Sawtooths (photo, photo). I observed a handful in the Southern Sawtooths but it seemed like cool air temperatures and a morning breeze kept widespread natural activity at bay. Today will be about 7 degrees warmer and mostly calm. These two factors should allow for more natural wet loose activity. These slides are going to be larger and more numerous in areas that received more than 8" of snow on Monday. These areas include portions of the Smoky Crest, the western Smokys, Sawtooths, and Banner Summit. 

WIND SLABS: Yesterday, I glassed two slab avalanches in the Sawtooths (observation). Both failed below cliff bands that were likely loaded by spindrift from above. Tuesday near Banner Summit, Scott found small slabs, dunes, drifts, and wind-press in most exposed middle elevation terrain (observation). Ben and I found similar conditions in the Smoky Mountains near the headwaters of the Salmon. The slabs we found were sensitive to our weight and were well distributed and large enough to keep us out of quite a bit of terrain (video, observation).

Many of these slabs rest on a melt-freeze crust from our recent warm spell. Where we've looked, the interface at the base of the slab is fairly friendly. We've only seen a handful of slab avalanches despite good views into the Boulders, Smokys, and Sawtooths. It's been 2 days since the storm ended, and your odds of triggering a slab avalanche are decreasing—but we're not out of the woods just yet.

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