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 8 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

CONSIDERABLE: Expect rising avalanche danger in the backcountry as snow accumulates and is drifted onto steep slopes today. Heightened conditions already exist this morning due to wind drifted snow, and dangerous conditions will continue to develop in the mountains. Soft slab and loose avalanches will become more likely as fresh snow accumulates, even in sheltered terrain. Avalanches may fail on feathery surface hoar or a shallowly buried sugary persistent weak layer, and some could be remote triggered from a distance. The danger will continue to rise overnight, with natural avalanches becoming increasingly possible. Expect HIGH danger on many backcountry slopes tomorrow.

  • Use extra caution in the backcountry today.
  • Evaluate snow and terrain carefully, make conservative choices, and avoid steep slopes with wind drifted snow.

Problèmes avalancheux

  • Wind Slabs

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

    Heightened avalanche conditions exist on drifted upper elevation slopes this morning after sustained strong south winds raked exposed slopes overnight. Accumulating snow and continued strong southwest wind today will cause the danger to continue to rise and the problem to become more widespread. Drifts are building on widespread weak surface snow and buried sugary or faceted weak layers, and dangerous avalanche conditions are likely to develop. The wind drifted snow problem will be most apparent at upper elevations, but by later today you might find fresh and sensitive wind slabs on drifted slopes at all elevations.

    • Watch for and avoid drifted snow on the lee sides of major ridges and in and around terrain features like cliff bands, scoops, gullies, stringers, and sub-ridges.
    • Avoid steep slopes that have a smooth, rounded appearance, or that sound hollow like a drum.
    • Softer, fresh wind slabs may be triggered remotely or from a distance today, while harder wind slabs have a nasty tendency to let you get well out on them before releasing.
    • Cracking or collapsing in the snow are red flags indicating instability.

  • Storm Slabs

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

    Soft storm slabs and loose sluffs involving fresh snow will become increasingly likely on slopes with significant accumulations.

  • Persistent Slabs

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

    The shallow snow on the ground in many areas has become loose, sugary, and faceted in the past couple weeks, and this week's very cold temperatures didn't help. We've found particularly weak snow at mid and lower elevations in the backcountry, and anywhere where the total snow is fairly shallow. At upper elevations and in deeper areas, weak sugary snow exists just under the surface. Feathery surface hoar was widespread across the zone.

    Wind drifts formed and slabs are building up on top of sugary or faceted snow, and if you trigger an avalanche today it may fail on a buried persistent weak layer. You could trigger avalanches remotely, from a distance, or below. Instability is likely to last for a while.

    Feathery surface hoar is widespread across the zone and has been observed at all elevations including ridge lines and in avalanche starting zones. If this stuff stays intact when it's buried, it could become another problematic persistent weak layer.

Recent Activity

Friday afternoon, 3 lucky riders triggered a large hard slab avalanche on a south facing slope at about 9000' in elevation near Providence Peak. Luckily nobody got caught in the 4' to 6' deep and 300' wide avalanche consisting of wind drifted snow and failing on a sugary or faceted persistent weak layer. See Report HERE

Snow and Weather

The National Weather Service has issued a Winter Storm Warning for the mountains of eastern Idaho including the Bear River Range in Franklin and Bear Lake counties. A Winter Weather Advisory is in place for much of northern Utah, including the mountains around Cache Valley. Accumulating snow and sustained southwesterly winds will create dangerous avalanche conditions on drifted slopes in the backcountry today.

Looks like 6" of new snow fell overnight at Beaver Mountain. The Tony Grove Snotel at 8400' reports 3 or 4 inches of new snow with .3" SWE. It's 26º F this morning and there's 39"of total snow containing 83% of average SWE. It's 20º F at the 9700' CSI Logan Peak weather station, and southwest winds are currently averaging about 30 mph and gusting to 57 mph early this morning.

An upper level trough will continue to bring widespread precipitation to the area through the day. A trailing weather disturbances will impact mainly the northern half of the forecast area tonight through Monday. We'll see snow in the mountains today, with 4" to 8" of accumulation forecast. High temperatures at 8500' will be around 25º F, but will drop into the teens this afternoon. Expect 16 to 23 mph southwest wind. Tonight it will snow, with 5" to 9" possible, a low temperature around 14º F and 17 to 26 mph west wind, gusting around 40 mph. Tomorrow, we'll see continued snowfall, with 3" to 7" possible. High temperatures around 23º F are expected, but the big story is the strong southwest wind. Wind speeds averaging 30 to 40 mph with gusts close to 60 mph will cause significant drifting and likely HIGH avalanche danger in the backcountry.

Additional Info

I will update this forecast tomorrow morning.

General Announcements

The Beaver Mountain Backside is the backcountry, and it is avalanche terrain. If you cross the ski area boundary, you and your partners should carry and practice with avalanche rescue equipment. As always in the backcountry, practice safe backcountry travel protocols.

The new UAC IOS mobile app is now available on the app store. Check out the new "My Weather" feature. HERE

Check out the new free online avalanche course series developed by the Utah Avalanche Center. This is a great way to refresh your skills or prepare you for a Backcountry 101 or Level 1 class. HERE

Now is a great time to practice companion rescue techniques with your backcountry partners. Here is our practice video.

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This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. The forecast describes general avalanche conditions and local variations always occur.

Régions couvertes