Bulletin d’avalanche

Bulletin d’avalanche

Payette Avalanche Center
Voir sur la carte

Danger d’avalanche

Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
Périmé — ce bulletin a expiré 6 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Wednesday night's storm deposited about 6 inches of fresh snow across our forecast area.  Grauple, warming temps and a thin freezing mist crust accompanied the storm throughout the day yesterday in some areas.    Our snowpack is definitely  sensitive right now,  a combination of buried weak layers and wind slabs will be waiting for a trigger today.  Avoid steeper terrain today and pay attention to 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, choose your terrain wisely and keep doing those snow dances!

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1

    Wind slabs formed in some areas over the last 2 days as South, and West winds gusted into the mid 20 mph range.  Cracking snow under or shooting away from your skis or sled is 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.

    Cracking in the snow surface yesterday near the ridgetops.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    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.  Widespread whumphing or collapsing of the weak layers was occurring yesterday on almost all aspects and at a variety of elevations.  These layers were formed during the high pressure with warming during the day and very cold night time temperatures.  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 just below the new snow. In some areas there are more than one of these extremely weak layers.  Further down in the snowpack is a thick layer of  loose, weak, faceted snow that has grown above the early November snow and has litterally rotted out into a 6-10 inch weak layer.  The new snow has not been 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 overlying these weak layers to grow in size, increasing the size of a potential avalanche until it is triggered.

    Buried surface hoar layers observed 12/16/20.

Avalanche Discussion

Click on the video link and photos below for a quick overview of the snow structure.