Avalanche forecast

Logan

Utah Avalanche Center
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Avalanche danger

  • Alpine
  • Treeline
  • Below treeline
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Highlights

Dangerous avalanche conditions and CONSIDERABLE danger exist on drifted upper elevation slopes. People are likely to trigger wind slab avalanches failing on a sugary persistent weak layer in steep drifted terrain. Elevated avalanche conditions also exist in sheltered terrain and on mid and lower elevation slopes where it is quite easy to trigger small soft slab avalanches failing on a buried persistent weak layer of feathery surface hoar.

  • Evaluate snow and terrain carefully, make cautious decisions, and avoid steep slopes with recent deposits of wind drifted snow.

The danger will probably rise to HIGH in many areas tonight as a powerful winter storm impacts the zone. Heavy snow and drifting will cause rapidly rising danger and potential for significant natural avalanche activity.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    People are likely to trigger dangerous slab avalanches of stiff wind drifted snow failing on a sugary buried persistent weak layer if they venture onto exposed upper elevation slopes.

    • Wind slabs often form on the lee side of exposed ridges and in and around terrain features. Watch for and avoid drifts on gully walls, under cliff bands, along sub-ridges, in scoops, saddles, and sinks.

    • Drifted snow is stiffer and more compacted than non-drifted snow. Last night's strong winds created harder drifts (called hard slabs if they avalanche). Hard slabs are often stubborn, notorious for allowing people to get out on them before releasing, kind of like a mouse trap!
    • Slab avalanches of wind drifted snow failing on a persistent weak layer might be triggered remotely, from a distance, or even below!
    • Today you should avoid travel on or under steep slopes with deposits of wind drifted snow.

    • Freshly formed wind slabs can be quite sensitive and are often remotely triggered.
    • Shooting cracks in drifted snow are a sure sign of instability.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1

    Small soft slab avalanches failing on a persistent weak layer of surface hoar are still rather likely for people to trigger, even on sheltered and mid and lower elevation slopes steeper than 30 degrees. These shallow avalanches are very soft, and appear to be non-threatening or at least manageable, but don't get dragged into trees or other terrain traps.

    We've found buried weak sugary snow at all elevations and on slopes facing every direction. So, the PWL (persistent weak layer) problem will get much worse as widespread slopes with poor snow structure are overloaded, and the problem is likely to be an issue for a while. Areas plagued by a very sensitive PWL consiting of buried feathers of surface hoar are widespread, mostly in sheltered and mid elevation terrain. Watch for avalanches to occur on lower angled and unexpected slopes as a slab forms with the storm, overloading this shallowly buried layer.

    Red Flags indicating the PWL instability will include audible collapses or wumpfs and shooting cracks. Slab avalanches failing on a buried persistent weak layer are likely to be remotely triggered from a distance, hopefully from above or from an adjacent slope, and not from below. Monday's snow fell on bare ground or very shallow snow on low and many mid elevation sunny slopes, (W, SW, S, SE) so the danger of avalanches is low, but potential might be high for hitting rocks.

Avalanche Warning

Widespread avalanche activity is expected and the avalanche danger will be HIGH. In effect from 3 p.m. MST this afternoon until 6 a.m. MST Saturday. For the mountains of Northern Utah and Southeast Idaho including the Wasatch Range, Bear River Range, and Western Uinta Range. A rapid load of heavy snow combined with very strong winds and preexisting weaknesses in the snowpack will create very dangerous avalanche conditions. Both human triggered and natural avalanches are likely. Stay off of and out from under slopes steeper than 30 degrees.

Special Announcement

Our annual party and fundraiser is coming up on December 6 in Logan at the Cache. 19th Annual Utah Avalanche Center Pray for Snow Party and Fundraiser information and tickets HERE.

Join the Utah Avalanche Center and the Division of Outdoor Recreation to celebrate the Fourth Annual Avalanche Awareness week, from December 4 - December 11. Click HERE to view the full list of events for the week.

Recent Activity

A party of riders report triggering a few small, manageable, soft slab avalanches on north facing slopes at upper elevations in Providence Canyon on Tuesday.

See our updated list of observed avalanches from across Utah HERE

Tuesday, we couldn't see much at upper elevations due to the clouds, but we easily triggered cracking and collapsing, and we remotely triggered a very soft slab at around 7000' in elevation right off the Franklin Basin Road. Nikki found nice feathers of preserved surface hoar under the fresh powder and shallow Thanksgiving snow...

Snow and Weather

Today, you'll still be able to find nice powder in the backcountry, especially in sheltered terrain, but dangerous conditions exist on drifted upper elevation slopes. South winds are increasing another notch this morning so we can expect continued drifting in exposed terrain. Wind slabs built up and are now getting thicker and harder as snow is drifted onto steep upper elevation slopes plagued by widespread sugary weak snow. Early season shallow snow conditions exist across the Logan Zone, and there are numerous shallowly buried land mines out there.

Expect rising avalanche danger in the backcountry, likely rising to HIGH by tomorrow morning. The National Weather Service in Pocatello issued a Winter Storm Warning through 11:00 tomorrow morning for the Bear River Range. A powerful winter storm could bring up to two feet of snow to upper elevation terrain tonight with strong and gusty southwest winds. Another good storm is on the tracks for later in the weekend.

Additional Info

  • Take the all-new online avalanche courses the UAC built for Know Before You Go or take other online courses listed on the KBYG website (Develop skills -> Online Learning).
  • Get your avalanche rescue gear ready for winter. Put fresh batteries in your transceiver and update the firmware. Inspect your shovel and probe. Get your airbag backpack ready by possibly doing a test deployment and update the firmware if it is an electric version.

General Announcements

Please submit your observations from the backcountry HERE.

For a list of avalanche classes from the Utah Avalanche Center go HERE

For information on where you can ride your sled or snowbike, check out this map of the winter travel plan for the Tony Grove and Franklin Basin Areas HERE.

The Tony Grove Road and other forest roads in the Logan Ranger District are not maintained for wheeled vehicles in the winter.

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.

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