Avalanche forecast

Swan Range

Flathead Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

New snow and wind-drifted snow will keep dangerous avalanche conditions around for another day. Recently-formed slabs will be larger, thicker, and more dangerous as you gain elevation. Enjoy the soft snow by choosing lower-angle slopes (35 degrees or less) not connected to steeper slopes above.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    An observation Wednesday from the northern Swan noted up to 16 inches of new and recent snow, which cracked underfoot. The Noisy Basin SNOTEL received an astonishing 2 inches of water (SWE) in 12 hours ending Wednesday afternoon. Slabs will be thicker and more dangerous as you gain elevation. Cracking in the snow surface is a sign of instability. Where you find more than about 8 inches of new and recent snow, stick to slopes less than about 35 degrees. 

    (12/26/2022) 12/28 1400h 6400' NE. Vehicle-triggered soft slab with dry storm slab visible in top 20cm, moist slab 20 cm underneath.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Weak layers of faceted snow lurk near the base of the snowpack. Loud collapses and shooting cracks Wednesday are clear signs that the weight of a person or snowmachine can collapse these layers and release large, dangerous avalanches. You’re most likely to trigger a slide on slopes steeper than about 35 degrees where the snowpack is shallow. Convex rollovers – where a slope steepens abruptly – are likely trigger points. The potential for remotely-triggered avalanches continues, so choose uptracks and climbs that keep you out from under steep slopes.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3

    Strong winds earlier this week formed slabs of drifted snow on steep, upper-elevation slopes. These hard slabs are camouflaged by Wednesday’s snow, which wasn’t accompanied by strong winds. Look for this hazard on the lee sides of ridges and gullies, and downwind of saddles and passes that funnel southerly and westerly winds. Avoid being on or under terrain like this that’s steeper than about 35 degrees. Spontaneous cornice failures can trigger these slabs, so stay well back from slopes overhung by cornices.

Avalanche Discussion

This has been an eventful weather week so far. After an atmospheric river led to three days of conditions that warranted avalanche warnings, the temperatures are on a cooling trend, and continued precipitation is abating. 

Wednesday’s surge of precipitation in the Swan Range was striking, as Noisy Basin picked up around 2 inches of SWE in 12 hours! Stahl picked up half of that, with all other stations reporting much less. With a mostly dry day today, we are letting the AVALANCHE WARNING expire and are dropping the hazard at all elevation bands across the forecast area. 

Wet conditions and obscured skies have limited observations of recent avalanche activity. With improving travel conditions, we look forward to observing the natural avalanche cycle that occurred over the past few days. 

I toured with Rob and Blase in the southern Whitefish Range Wednesday, and we found wind-loaded features as our primary concern along ridgelines. With a few stomps, Blase could trigger car-sized chunks of cornices. Cam and his partner were in the northern Swan Range. They felt seven audible collapses at upper elevations with shooting cracks up to 100 feet away. They found this was a stubborn soft slab problem from the recent storm snow, and it was in all aspects.

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