Bollettino valanghe

Logan

Utah Avalanche Center
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  • Limite del bosco
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In sintesi

MODERATE: The snow in most areas is stable and the avalanche danger is generally LOW, but heightened avalanche conditions exist on some drifted upper elevation slopes. You could trigger avalanches involving fresh wind-drifted snow. Dangerous hard slab avalanches failing on a sugary buried persistent weak layer are unlikely yet remain possible on isolated very steep upper elevation slopes with poor snow structure. Evaluate snow and terrain carefully.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2

    Heightened avalanche conditions exist on upper elevation slopes, and you could trigger avalanches consisting of wind drifted snow. Drifting occurred in exposed terrain much of last week, and there are some deeper hard wind slabs lurking under the fresh snow in places. Moderate east and southeast winds are expected on Christmas Day, which could create sensitive drifts at upper elevations in unexpected or unusual places.

    • Watch for and avoid fresh or older drifts 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.
    • Hard wind slabs have a nasty tendency to let you get well out on them before releasing.
    • Cracking in the snow is a red flag indicating potential instability.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    3

    Although quite unlikely, dangerous human triggered hard slab avalanches failing on a persistent weak layer near the ground called depth hoar remain possible on upper elevation slopes. Avoid very steep previously drifted slopes with poor snow structure, including shady or rocky terrain at upper elevations.

    The shallow snow on the ground in many areas has become loose, sugary, and faceted in the past couple weeks. I found particularly weak snow in the backcountry near Beaver Mountain, where the total snow is only about 2-feet-deep or less. In these areas the snow is currently stable despite it's weakness, but it'll get interesting when we get significant accumulation in the future.

    Sugary, faceted snow from the Thanksgiving storm creates a persistent weak layer near the ground on slopes with shallow snow cover. This from 12/20/18, on a west facing slope at 8500' on Beaver Mountain's backside.

Snow and Weather

A few more inches of light snow fell in the Logan Zone overnight, and you'll find nice shallow powder, stable snow, and Low avalanche danger in most areas. Exceptions will be on drifted upper elevation slopes where human triggered avalanches involving fresh or older wind drifted snow are possible.

The Tony Grove Snotel at 8400' reports 4 inches of new snow with .4" SWE in the last 24 hours. It's 23º F and there's 38" of total snow containing 88% of average SWE for Christmas Day.

It's 17º F at the 9700' CSI Logan Peak weather station, with 25 mph wind from the southeast.

A series of weather disturbances will bring periodic precipitation to much of the area through the week. We'll see snow in the mountains today, with around 1 inch of accumulation possible. Expect a high temperature at 8500' near 29º F and 6 to 10 mph east-southeast wind. Snow is likely tonight, with another inch possible, low temperatures around 11º F, and 5 to 10 mph east wind, veering from the northwest in the evening. Looks like we'll see partly sunny skies in the mountains on on Boxing Day. High temperatures around 23º F and 10 mph northwest winds are expected.

Additional Info

Have a safe and happy Christmas. I will update this advisory Wednesday morning.

Recent Activity

No avalanches were reported over the weekend, but on Sunday I found evidence of a small natural involving freshly wind drifted snow in the Peterson Hollow fire scar.

General Announcements

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.

If you would like to get the daily advisory by email you subscribe HERE.

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

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