Avalanche forecast

Avalanche forecast

Payette Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Upwards of 2 feet of snow that fell since Friday the 13th under gusty WSW winds still sits upon persistent weak layers that formed during our previous dry, sunny high pressure. These weak layers and others mid storm are showing signs of propigating: you could still trigger a persistent slab avalanche, 1-3 feet deep, especially on wind and sun shelterd slopes. Wind loaded areas near ridgelines may be more sensitive.

Use extra cautous routefinding and travel protocols on sheltered and leeward slopes steeper than 30 degrees, and evaluate the snowpack before traveling on a steep slope.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Weak layers of surface hoar and near surface facets were buried around December 8th under about 5", and then Friday the 13th-Wednesday the 18th: our last storm, laid down another 2 -3 feet of snow (2-3" of SWE) resting on weak layers. Mid-storm, there was a break that developed near surface facets, surface hoar, and graupel on the snow surface and was buried by the remaining 1.25+ or so feet. We were able to get moderate propagating results Wednesday on this mid storm weak layer and hard propagating results on the 12/8 layer.

    Be cautious and don’t expose more than one person at a time to avalanche terrain...These persistent weak layers are not everywhere and were likely destroyed in many places where the wind, sun, and warm inverted temps helped beat them down. Likely areas that will hold these lurking weak layers are going to be in sun and wind sheltered areas. Forecasted warming temps may help to bond these weak layers sooner than colder weather but only time will tell. 

     Unlike storm instabilities, Persistent Slabs are commonly triggered remotely, from flat areas, and failures can propagate across terrain features like ridges, ribs, and gullies. 

    This problem poses one of the hardest for riders and sliders to dance around. Use good travel protocols on not only upper elevation, but also mid elevation protected slopes... Choose simple terrain to begin your day with representative inconsequential test slopes where if your sled or ski cut sends you on a ride it won’t be a big deal.

     Slopes steep enough to slide should be approached with caution and the snowpack evaluated before you travel.

    (12/18/2024)

    Fresh, R1-D2 Natural Avalanche, East aspect of 8302 in the Lick Cr Drainage tough to see but likely failed on a combination of facets after recieving wind loading. We got Hard yet propigating results (ECTP 24) at this aproximate depth nearby in our test pit.

    Photo: George Halcom

Avalanche Discussion

Our hearts go out to the loved ones effected by  the unfortunate avalnche over the weekend, just South of our advisory area on West Mountain where a rider triggered avalanche and was caught and buried in a terrain trap. This avalanche failed 2-3 feet deep on buried surface hoar and near surface facets that formed during clear nights. Test scores are still producing propigating results around  1 and 2 feet down.

Always keep you eyes on you partners while they are traveling on slopes steep enough to slide, and avoid areas that are terrrain traps like gullies, creeks, and steep to flat transitions where the snow could bury you deeper and easier, and these weak layers may hide.

Aside from triggering a persistent slab avalanche all of this new 2-3 feet of snow we got over the weekend is going to be getting heated by warming, above average temps and may produceD-1 Loose snow avalanches under direct sunlight as daytime temps climb and Stiff wind slabs in exposed areas at upper elevations are possible but likely healing fast and can be noticable with snow surface etching clues.

Start with slopes that if they slid the consequences would be low to none. Avoid Terrain Trap areas like gullies, creeks, depressions, and cliffs. Only allow one person on a steep slope of any aspect while someone watches from a true safe spot.

 

Dont Miss This Friday, December 20 @ 6:15 pm - 8:15 pm State of the Snowpack at Gravity Sports in McCall Gravity Sports 290 Jacob Street, McCall, ID, United States

Gravity Sports State of the Snowpack #1 and "What's In Your Pack?" December 20, 2024 - 6:15pm- 8:15pm Come find out what is going on in the snowpack with the PAC forecasters.  We will also tackle the perennial questions, "What's in your pack"?  "Am I carrying too much gear?"  And "How come your pack is […]

Today's forecast is brought to you by Brundage Mountain Resort who is a continued sponsor of the PAC. Thanks for your support Brundage!