Bulletin d’avalanche

Logan

Utah Avalanche Center
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Danger d’avalanche

  • Alpin
  • Limite forestière
  • Sous la limite forestière
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

People should continue to avoid travel in avalanche terrain today. Stay off and well out from under slopes steeper than 30° and adjacent slopes, especially northerly facing slopes at upper elevations. Rapid accumulation of around three feet of very heavy snow, drifting snow from strong winds, and rain at lower elevations created dangerous avalanche conditions and CONSIDERABLE danger at all elevations in the backcountry. Natural avalanches are possible and people are likely to trigger dangerous avalanches. Soft slab avalanches of heavy storm snow are likely in steep drifted terrain, and loose wet avalanches entraining rain-soaked storm snow are likely in steep terrain at lower and mid elevations. Areas with HIGH danger remain on on northerly facing upper elevation slopes. Drifting and heavy snow overloaded slopes plagued by a deeply buried persistent weak layer, and dangerous avalanches breaking 4 to 6 feet deep on sugary faceted snow near the ground are likely in some areas.

Problèmes avalancheux

  • Storm Slabs

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

    Around three feet of very heavy snow accumulated at upper elevations with 8" SWE recorded at the 8400' Tony Grove Snotel since Tuesday morning, and periods with heavy snow are expected in the mountains again today. The heavy storm snow is inverted, or heavier on top, and when it is this way, it is prone to producing soft slab avalanches. During periods of intense snowfall and drifting today natural slab avalanches of storm snow are possible.

    People could trigger slab avalanches of wind drifted snow in steep terrain at all elevations today. South winds ramped up again this morning, gusting in 60 mph range mph on Logan Peak, whistling up Logan Canyon, raking the fresh snow off windward slopes and depositing it in stiff drifts on the lee side of major ridges and in and around terrain features. Avoid corniced slopes and deposits of wind drifted snow in and around terrain features like sub-ridges, gullies, scoops, and cliff bands.

  • Loose Wet

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

    As rain soaks the snow at lower elevations today it will continue cause potential for loose wet avalanches entraining big piles of storm snow in steep terrain.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    3

    Although they have become less likely and harder to trigger, very dangerous deep hard slab avalanches failing at ground level on weak faceted snow remain possible. The rapid load from this week's new snow, and especially from continued drifting, could be enough increase in load to cause dangerous natural hard slab avalanches failing on a deeply buried persistent weak layer on upper elevation northerly facing slopes. These slopes have a layer of weak, sugary facets near the ground that could fracture and produce slab avalanches 4-6 feet deep and hundreds of feet across. The danger of deep slab avalanches failing on a persistent weak layer is diminishing as the snow pack continues to deepen and get heavier and the sugary faceted snow is compressed into the ground features. However is some areas, avalanches on northerly facing slopes still might be triggered remotely, from a distance, or from flatter terrain under steep slopes.

    • Recent strong winds drifted snow right onto suspect northerly facing slopes that are plagued by a persistent weak layer, increasing the load and the danger.
    • An avalanche of wind drifted snow overrunning a with a deeply buried persistent weak layer could step down, include older snow, and become much larger and more destructive.

Recent Activity

  • Numerous natural loose wet avalanches, entraining big piles of storm snow were observed in Logan Canyon yesterday afternoon.
  • Dangerous roof avalanches were also fairly widespread in the zone, due to the warm-up
  • With this much heavy snow and wind drifting, I'm confident that unseen large natural avalanches occurred during the storm, and more are possible today.

Check HERE for all the latest observations and avalanche activity.

Snow and Weather

The northern part of the Logan Zone, including the Northern Bear River Range near the state line and in Idaho picked up and continue to pick up more snow than the mountains surrounding Logan. About three feet of very heavy snow accumulated at upper elevations in the past couple days. The 8400' Tony Grove Snotel reports 30°F this morning and around 35 inches of new snow with 8"of SWE (snow water equivalent) from the storm so far, since Tuesday morning. Increasing south winds are blowing well over 30 mph this morning at the CSI Logan Peak weather station, with gusts in the 60 mph range. It'll be another stormy day in the mountains, with periods of heavy snow, another 3 to 5 inches of accumulation, above freezing temperatures in the mountains, and continuing strong southwest winds forecast. Unsettled weather will continue through tomorrow, with periods of snow and 3 to 5 inches of accumulation expected tonight. Clearing and fair weather is expected Sunday, continuing well into next week.

We found pretty good coverage on lower elevation slopes in Logan Canyon on Tuesday, which means we'll now have to watch for avalanche problems at all elevations and on all slopes.

Additional Info

  • Always follow safe backcountry travel protocols. Go one person at a time in avalanche terrain, while the rest of your party watches from a safe area.
  • Check your avalanche rescue equipment, change your batteries, and practice often with your backcountry partners. Check slope angles and stay off of and out from under slopes steeper than 30° and adjacent slopes.

General Announcements

Who's up for some free avalanche training? Get a refresher, become better prepared for an upcoming avalanche class, or just boost your skills. Go to https://learn.kbyg.org/ and scroll down to Step 2 for a series of interactive online avalanche courses produced by the UAC.

  • Check out all the upcoming education classes and clinics HERE.
  • Please submit your observations from the backcountry HERE.

This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.

Régions couvertes