Bollettino valanghe

Bollettino valanghe

Payette Avalanche Center
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Pericolo valanghe

Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The snowpack throughout the West Central Mountains is pretty sensitive right now,  a combination of buried weak layers and wind slabs will be waiting for a trigger today.  Avoid steeper terrain and pay attention to obvious warning signs like cracking and whumphing.  A thin snowpack will make access to  larger avalanche terrain challenging but be aware that where the snowpack is the deepest on windloaded slopes is where you are most likely to trigger an avalanche today.  Avoid steep rollovers or gullies in wind protected areas where surface hoar and faceted snow formed over the last few weeks.   Buried treasure will continue to be a significant hazard today, pay attention to changing conditions later in the day as the next storm enters the area.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1

    A variety of weak layers exist within our snowpack.  You are very likely to hear these layers talking to you today as you travel through the mountains.  Whumphing or collapsing of the weak layers was occurring yesterday on almost all aspects and at a variety of elevations.   If you take the time to dig a quick hasty or hand pit as you travel, you will see a combination of buried surface hoar and near surface facets present in the upper snowpack 6-12 inches down from the surface.  In some areas there are multiple layers of surface hoar.   An obvious thick layer of  loose,  faceted, very weak snow is the weak layer collapsing and whumphing in most areas and is a result of the early November snow that litterally rotted out during the extended high pressure over the last few weeks.

    This week's new snow was not quite enough of a load in most places to overload these layers so they are still waiting  for a trigger.  Additional snowfall over the next 48 hours could be that trigger but a great take home point is that if we don't see natural avalanches associated with this next storm,  that does not mean the snowpack is safe or stabilizing.  These weak layers will not be going away until we have a significant loading event or they are triggered by a skier or snowmobilier.  Incremental or small storm total loading is a bad scenario, it allows the slab  weak layers to  slowly grow in size, increasing the size of a potential avalanche until it is triggered.

    12/18/20 Pit above Lick Creek Summit ECTP12 whumphing/collapsing occurring near the top of the weak, loose layer.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1

    Wind slabs formed in some areas earlier this week.  Cracking snow under or shooting away from your skis or sled is  an obvious warning sign of this.  Visual clues like drifted or sculpted snow will also let you know what the wind has been doing and where.  Sudden changes in consitency of the snowpack from soft to firm or hard  across a slope is also another great clue. You are most like to find sensitive wind slabs near ridgetops or in other wind exposed areas.

    Cracking in the snow surface yesterday near the ridgetops.

Avalanche Discussion

The next round of storms will begin this afternoon with  increasing South and Southwest winds.  Significant snowfall is possible in the upper elevations.  Conditions will change and the avalanche hazard will likely increase overnight and through the rest of the weekend.