Avalanche forecast

Avalanche forecast

Payette Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
Out of date — this forecast expired 2 years ago.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 over the last week under gusty WSW winds now sits upon persistent weak layers that formed during our previous dry, sunny high pressure. 

 You could trigger a persistent slab avalanche, 1-3 feet deep, especially on wind and sun shelterd slopes. Wind loaded areas near ridgelines may have developed an even thicker and denser slab above these weak layers.

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

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 began the current storm track that has laid down another 2 feet of snow, binging the total to around 2.5 feet of new snow resting on weak layers.

    The tricky part that should keep you on the conservative side is that 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.

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

    Choose simple terrain with representative inconsequential test slopes to begin your day. Slopes steep enough to slide should be approached with caution and the snowpack evaluated before you travel.

Avalanche Discussion

Over the weekend, just South of our advisory area on West Mountain there was a rider triggered avalanche that claimed the life of a loved one. Our hearts go out to the family and friends of the rider. 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 2 feet down.We  recieved observations of buried surface hoar producing propigating results near Brundage over the weekend. These weak layers will last or persist in areas that are protected. It may take another week of above freezing temps to help stabilize the snowpack.

 In the near future, travel protocols in and around avalanche terrain are going to have to be extra cautious. Keep you eyes on you partners while the 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.

All of this new snow over the weekend may produce Loose snow avalanches and stiff wind slabs in exposed areas. While you ride or slide this loose snow and releasing a wind slab can pose a threat and push you into terrrain you'd rather avoid. 

Start with slopes that if they slid the consequences would be low to none. Avoid 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 […]