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

Points saillants

VERY DANGEROUS AVALANCHE CONDITIONS EXIST.

Drifting and heavy snowfall overloaded widespread buried persistent weak layers on many slopes and created HIGH avalanche danger in the backcountry. People could trigger avalanches at all elevations, and both natural and human triggered avalanches are likely on drifted upper and mid elevation slopes facing northwest through southeast. Avalanches could be very large, destructive, fast moving, far running, and potentially deadly! Continuing heavy snowfall and drifting from strong southwest winds today will cause the danger to increase further and become more widespread.

  • Use extreme caution in the backcountry. Expect unstable snow conditions. Avoid travel in avalanche terrain.
  • Choose safe routes in low angled terrain well out from under and not connected to slopes steeper than about 30 degrees.

Problèmes avalancheux

  • Persistent Slabs

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

    Heavy snowfall and strong winds today will continue to add significant weight to slopes that are already near the tipping point. Buried persistent weak layers consisting of sugary faceted snow are widespread across the Logan Zone, and the threat of large and deadly avalanches failing on weak snow near the ground is quite real. Avalanches are likely where a slab of more cohesive wind drifted snow formed on top of the weak snow.

    • Avalanches failing on a buried persistent weak layer might be triggered remotely, from a distance, or worse from below!
    • Cracking and collapsing of the snow are a red flag, indicating unstable snow conditions.

  • Wind Slabs

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

    Westerly winds last week drifted fresh snow into lee slope avalanche starting zones and built drifts and wind slabs on steep slopes at upper and mid elevations. Expect more drifting of fresh storm snow from resuming moderate west and southwest winds later today. Natural and human triggered avalanches of wind drifted snow are likely, especially where drifts have built on top of a buried persistent weak layer.

    • Wind slabs are often rounded and chalky looking, and they can sound and feel hollow and drum-like when you walk on them.
    • Watch for and avoid stiffer drifted snow near ridge tops and in and around terrain features like gullies, scoops, cliff bands, and sub ridges.
    • Cornices are starting to grow with the recent strong winds. Stay well back from the edge as they can break much further back than you expect.

  • Storm Slabs

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

    Loose dry and soft slab avalanches of new snow are likely in steep terrain today, especially on slopes that pick up significant accumulations of new snow. Rapid loading from heavy new snow or blowing snow could also cause deeper instabilities, and buried persistent weak layers could easily be reactivated by the quick addition of weight. Natural avalanches often occur during periods of particularly heavy snowfall.

Avalanche Warning

VERY DANGEROUS AVALANCHE CONDITIONS EXIST IN THE BACKCOUNTRY. NATURAL AND HUMAN TRIGGERED AVALANCHES ARE LIKELY OVER THE NEXT SEVERAL DAYS. STAY OFF OF AND OUT FROM UNDER SLOPES STEEPER THAN 30 DEGREES.

Special Announcement

We've completed the report on last Saturday's tragic avalanche in the backcountry in Mill Creek Canyon above Salt Lake City that killed four skiers. Final Accident Report

The UAC in Logan is offering a Youth BC 101 avalanche class for youth aged 16-20 on Feb 21. For more info and to register, click HERE

Recent Activity

Yesterday, through a brief break in the clouds I could see some fresh natural avalanches in the large east facing avalanche paths in the Wellsville Mountain Wilderness above the towns of Mendon and Wellsville. Much of the avalanche terrain the rest of the zone was obscurred from view by clouds, but more natural activity likely occured. Saturday (2-13-2021), a party of local backcountry skiers remotely triggered a large avalanche in "the Gut" of White Pine Knob above the yurt in the popular Bunch Grass Canyon. The 4' deep and about 500' wide avalanche occurred on a southeast facing slope at around 8900' in elevation. The slope angle at the crown was in the lower 30° range, but the slope rolls to 40 degrees in the Gut itself, and the hard slab was well connected, pulling out even on the lower angled slope above and on each side of the steep section.

Thursday (2-11-2021), riders remotely triggered a large hard slab avalanche on a pretty low angled slope in the Peter Sinks Area (an area that is not well known for avalanches). The avalanche on an east facing slope at around 8300' in elevation was around 100 feet wide and 2 to 7 feet deep, and it stacked large chunks and piles of debris into the trees below. It was the third such hard slab avalanche to occur this week on a fairly low angled slope (between 30 and 35 degrees) and in a rather unexpected place. All have been in the eastern part of the Bear River Range...

Snow and Weather

A dangerous avalanche situation exists this holiday weekend in the backcountry, with very dangerous avalanche conditions and lots of nice powder to lure people into steep avalanche terrain. Snow is falling in the Logan Zone again this morning, and plenty will fall today, overnight, and tomorrow, with 2 to 3 feet expected to accumulate on upper elevation slopes by Wednesday morning. It's currently 16°F and there is 66 inches of total snow at the 8400' Tony Grove Snotel. Southwest winds are increasing a bit this morning and blowing around 22 mph with 40 mph gusts at the 9700' CSI Logan Peak weather station.

Strong westerly winds last week drifted tremendous quantities of snow into lee slope avalanche starting zones and cross-loaded drifts in exposed terrain lower down. Thick drifts and hard wind slabs exist in wind deposition areas, while the snow is still super shallow and very weak in more sheltered and scoured areas. With widespread layers of preexisting very weak snow, the recent significant increase in load on the fragile snowpack has created very dangerous avalanche conditions on drifted slopes in the backcountry.

It's snowing at a decent rate this morning and more snow is expected today in the mountains, with 8" to a foot of accumulation possible by this evening. High temperatures at 8500' will be around 21°F, with fairly strong southwest winds, and wind chill values will be as low as -8°F. Snow, heavy at times will continue tonight, tomorrow and tomorrow night, with 2 to 3 feet accumulating on upper elevation slopes by Wednesday morning. Expect HIGH avalanche danger in the backcountry, perhaps rising to EXTREME!

Additional Info

Do you have the essential avalanche rescue gear (transceiver, probe, and shovel) and do you know how to use them? Watch this video to see how the three pieces of equipment work together. HERE

Please keep practicing with the Beacon Training Park at the Franklin Basin Trailhead. Test yourself and your riding partners. It is free, fun, and easy to use.

General Announcements

Thanks to the generous support of our local resorts, Ski Utah, and Backcountry, discount lift tickets are now available. Support the UAC while you ski at the resorts this season. Tickets are available here.

Visit this website with information about Responsible Winter Recreation by the Utah Office of Outdoor Recreation.

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

Remember your information can save lives. If you see anything we should know about, please help us out by submitting snow and avalanche observations....HERE. You can also call us at 801-524-5304, email by clickingHERE, or include #utavy in your tweet or Instagram.

I will update this forecast by around 7:30 tomorrow morning.

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

Régions couvertes