Bulletin d’avalanche

Bulletin d’avalanche

Payette Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

An approaching storm today will increase Avalanche Danger this afternoon!  20 plus Mile an hour winds out of the South/Southwest will be loading leeward slopes and forming fresh slabs.  Buried weak layers are stronger, but are shallow in a lot of areas, and are not completely bonded.

Use good travel protocols like spreading out in steep terrain, and only expose one person at a time. Early-season obstacles like rocks and logs exist at mid and low elevations and on Southern aspects.

 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Older wind slabs formed under variable winds out of almost every direction, but most notably the South/ Southwest. Over the last couple of days, we have only observed but one shallow wind slab about 6 inches deep that pulled off a steep North facing rock above Shaw Twin Lake on Saturday. 

    Also on Saturday, December 18th, we got a report of a natural wind slab avalanche on West Mtn, South of Tamarack Ski Resort that failed around 2 feet down on a North aspect just below the ridgeline.

    Today, more snow is on tap along with gusty 20 plus mile an hour winds that will increase avalanche hazard likely forming slabs that are 5-20 inches thick and sensitive to the weight of a person.

    Be cautious Just below ridges and below cornices, and at mid-slope as they are the most likely spots to trigger wind slabs. 

     

    (12/18/2021)

    Saturday, December 18th at 7,700 Feet looking North into Shaw Twin Lakes, and the Lick Cr Drainage---Light Southern winds

    Photo: George Halcom

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Our snowpack is consolidating and getting stronger. It is dense at the bottom and graduates softer as you get towards the surface. On December 12th an atmospheric river event began, and ultimately doubled our snowpack...now a slab about 2 feet thick has developed above the snow that was on the ground from October to December 12th and is showing moderate test scores. At that interface when we look at the facets under a hand lens the facets are rounding and clustered. We will continue to monitor the strength of this layer as it is definitely shallow enough to be affected by the weight of Snowmobilers and skiers.

     

Avalanche Discussion

This information is sponsored by Mile High Power Sports in McCall...thank you for supporting the Payette Avalanche Center!

Coverage at elevations above 7,000 feet is good enough to allow some travel, but most of the terrain still has a lot of rocks, logs and bushes showing. Southern aspects are really shallow still.

The snowpack is growing in depth (150-180 cm at 7500ft), and weak layers of crusts and facets are showing (rounding) progress towards stabilization.  Our snowpack that formed from October-early December is gone on lower elevation slopes that got hit by a record warmup and Sun. 

North aspects are still holding that Oct-Dec snow that is between 1-2 feet near the ground. 

If you are going to ski or ride a steep upper elevation slope, only expose one person at a time. Snowmobiling off-trail is super high stakes right now with the shallow snow and all of the obstacles needing to be buried....be extra careful.

Recent cold temperatures have helped to break down crusts and deposit some of the best light-density snow that would make most people smile. While our snowpack is trending deeper and stronger, the snowpack is still shallow below 7500 feet and there are a lot of hazards lurking just beneath the surface. Above 7, 500 feet there is around 5 feet of snow on the ground, and in wind-loaded terrain, some slopes could have around 8-10 feet of snow.   Shallow snow is not only easy to hit obstacles in, but it allows skiers and riders to have more effect on buried weak layers.

 Things are looking good, but allow room for error as there is a lot of variability in our mountains right now.