Bulletin d’avalanche

Swan Range

Flathead Avalanche Center
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Danger d’avalanche

Wed
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Dangerous avalanche conditions exist. Warm temperatures and rain on snow are creating widespread areas of unstable snow. Avalanches can break wide distances and can run into terrain with minimal snow cover. Give avalanche terrain a wide berth today. 

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Whumpfing collapses, recent avalanches, and shooting cracks are clear signs to stay out of avalanche terrain today. Warming temperatures and rain on snow will increase the chances of triggering a slab avalanche. A triggered avalanche today will entrain wet snow, which will make it difficult to escape. Avalanches can break wider than expected, and be triggered remotely. Staying off of and out from underneath steep terrain today is essential. 

    Remotely triggered a wind-drifted feature.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    It will be easy to trigger a wet avalanche today. Rain on dry snow is a recipe for instant avalanching. Slides may fail as wet loose, or as wet slabs. Regardless, avalanches will entrain wet, heavy snow as they move down the mountain. Being caught in a large wet avalanche today will be difficult to survive. The surefire way of not being caught, is to stay out of steep terrain. 

    (4/13/2023)

    Wet Loose debris on a mid-elevation northwest aspect

    Photo: md

Avalanche Discussion

Despite the lower precip totals, we still expect natural avalanches to occur. Due to the crust at the bottom of the snowpack, natural or human-triggered avalanches could run a relatively far distance for the amount of snow on the ground. Pay close attention to what terrain is above you vs. how much snow you are standing on. A triggered avalanche today will entrain wet snow, causing them to be more destructive. Not only will avalanches be large enough to bury a person, but they will also smash the person into thinly covered stumps, logs, and rocks. 

Over the past few days, the snowpack has had a lot of say with its whumpfing collapses. If those whumpfs were words, I imagine them being "stay out of steep terrain." The other common theme to observations are natural and human-triggered avalanches and abundant shooting cracks. These glaring red flags are a result of recent snow building slabs above a fragile weak layer, which appears to be buried roughly 20-30 cm (one foot) below the surface. 

Generally speaking, above 6000 feet there is roughly .5-1 meter (2.5-3 feet) of snow. This snow rests on a hard and thick melt-freeze crust that formed over the wet and warm spell the first week in November. This facet/crust will likely be the sliding surface for wet avalanches today.

If there is one thing that a snowpack does not like, it is rapid change. Overnight temperatures soared above freezing, and temperatures will continue to climb to above freezing up to 9,000 feet. Precipitation will fall in the form of rain,  though the precipitation totals are not impressive. The northern Whitefish Range will be favored with up to an inch of water, whereas the rest of the region will see closer to .25-.5 inches of water.  

Régions couvertes