Boletín de aludes

Boletín de aludes

Payette Avalanche Center
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Peligro de aludes

Sat
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
Desactualizado: este boletín caducó 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The Avalanche Danger is Moderate today above 7000 ft.  Human triggered avalanches are possible especially where the dense slab of snow overlying weaker layers below is thinner and more easily influenced by the weight of a skier or snowmobiler. We are trending towards hard slab conditions, the denser the slab,  the more damage it will do to you if you are caught in it.   Pay attention to red flags like cracking and whumphing and changing snow surface conditions.   Additional snowfall tonight and tomorrow will increase avalanche conditions through the weekend.  Be cautious of early season conditions and buried treasure lurking in the snowpack.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    In the middle of the snowpack , about 2 feet down, exists our layer of greatest concern,  a very weak, loose layer of faceted snow made up of  buried surface hoar and near surface facets that formed during the 3 weak early December high pressure.   The snowfall from the last 10 days and resulting slab now comprise the upper half of the snowpack and is resting on the very weak layer below.  We trended from a softer slab to a dense hard slab after the 12/20-12/21 warming and rain event.  Hard slabs are much more tricky to predict and generally have much higher consequences if you do trigger them.  The potential to trigger this type of slab increases where the slab is thinner especially in uneven rocky terrain. 

    On solar aspects and at lower elevation, this layer is preserved under melt/freeze crusts and rain crusts making it even more tricky to predict how it will react to loading.  In the lower elevations, the snowpack warmed more and the rain helped to strengthen this weak layer once it cooled back down making it less of a concern.  

    Many of the natural avalanches earlier this week started in steep rocky terrain and scoured the snowpack down to the rocks below meaning that you would get the added bonus of bouncing down a cheesegrater like slope in addition to the very dense blocks of snow pummeling you.  This is an easy layer to pick out if you are digging in the snow and also easy to notice if you step out of your skis or off your sled.  The slab may support your weight, but chances are you will punch through to the deep bottomless snow below.  This is a layer we will likely be watching and discussing for quite a while.

     

                           

     

    Pit from ESE aspect on Jughandle Mountain. Compare this to the pit from Granite Mt. 2 days ago. A widespread weak layer exists within our snowpack,

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1

    Wind slabs formed in some areas over the last week, and may just be waiting for a skier or sled to trigger them.   It is likely that new wind slabs began forming last night.  Winds gusting into the 20+ range began overnight and will continue on the ridges and upper elevations today ahead of our next storm.  Cracking snow under your skis or sled  or shooting away from your skis or sled are obvious warning signs of this.  Strong northerly winds earlier this week changed the distribution of these slabs and removed the soft snow from exposed north facing terrain.  Wind deposited slabs may be found in unusual places right now but will be relatively small based on the limited  amount of soft snow available for transport.  Visual clues like drifted or sculpted snow will also let you know what the wind has been doing and where.  A sudden change in the consistency of the snowpack from soft to firm or hard  across a slope is also another great clue. You are most likely to find sensitive wind slabs near ridgetops or in other wind exposed areas right now.

     

     

Avalanche Discussion

The rain event that occurred Sunday and Monday of this week did a lot to change our snowpack. A widespread natural avalanche cycle occurred and the crowns are still visible on many steep slopes at all aspects and elevations.  In the lower elevations, this event created a stout crust and a thinner one in the upper elevations.  We will want to watch these new layers as we get additional snowfall.  Crusts can cause major changes in the snowpack during periods of high pressure as well as providing a slick bed surface when new snow is added.   Additionaly,  3 days of cold, clear weather has resulted in a new layer of surface hoar and near surface facets at the snow surface.  With additional snowfall coming tonight and tomorrow, expect to see avalanche conditions increase.  Make sure you and all of your partners are riding or sliding with ALL of the essential avalanche equipment. 

Thank you to everyone that has been sending in observations this year.  These help the forecast team form a clearer picture across the forecast area.  Also, backcountry skiers and inbound skiers need to be aware of closed areas in or leaving the boundaries at our local ski resorts. The ski patrol closes areas that they deem unsafe and will open them as the conditions change.  Violating closures can result in loss of skiing privileges and can create safety or challenging conditions for patrollers working to open these areas or if they have to rescue you if you get injured while skiing in them.