Bollettino valanghe

Bollettino valanghe

Payette Avalanche Center
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Pericolo valanghe

Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

2-4 feet of snowfall this week along with strong winds have created dangerous avalanche conditions. Triggering an avalanche several feet thick on persistent weak layers in the middle snowpack is likely across multiple aspects and elevations. Triggering a larger avalanche on older weak snow near the ground is trending down but still remains possible.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    2-4 feet of snow has fallen in the past week. All of this snow fell on a variety of weak layers. Several feet down there are crust/facet combinations on solar aspects and buried surface hoar and facets on shaded slopes. These weak layers have been the primary layers of failure during this week's event. We've found this slab of new snow overlying weak layers to be reactive across all aspects and elevations since the storm began. These persistent slabs will be thickest and most reactive above 7000' on east-facing slopes, where the wind was at work this past week. Look for shooting cracks from your skis or sled. Listen to the snowpack "talking" to you with sounds like whumpfing or collapsing of weak layers. Continue to seek out lower angle terrain while the snowpack continues to adjust to this new load of snow from this past week.

    ADDITIONAL DISCUSSION

    Very cold temperatures have decreased the strength of some of the slab overlying weak layers. You may begin to find dry loose snow becoming increasingly more sensitive as the upper snowpack continues to weaken even more.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Triggering a persistent slab on weak facets from November has been unlikely up until this recent storm. New snow this week added weight and stress to this older, weak snow near the ground. The likelihood of triggering a deeper avalanche on weak snow near the ground increased during the peak of last week's storms. In areas where the snowpack is shallow, an avalanche on persistent weak layers in the upper snowpack could potentially step down to the November facets. Avalanches this size would be large and destructive. You are most likely to trigger a persistent slab avalanche on steep, north-facing terrain above 7000', especially where wind has recently loaded slopes.

Avalanche Discussion

Two Persistent Slab Problems? What the...

A series of significant winter storms brought 2-4 feet of snow, strong winds, and very cold temperatures to our region this past week. We have doubled our entire season's snowpack in less than 7 days. Adding this amount of snow (weight) to a weak snowpack in a short period of time created unstable conditions. This weak snowpack has undergone severe stress this week. This new snow fell on persistent weak layers that were formed in late December and early January. These weak layers have been the culprit for most recent avalanche activity and instability test results (Persistent Slab Problem #1). If you've been reading the forecast or watching our videos (fingers crossed!), then you should be well aware of the poor snowpack structure we've been talking about for weeks now. The old November snow near the ground is Persistent Slab Problem #2. Although this deeper instability is becoming unlikely, the poor structure and new load of snow has kept us on our toes. Two different persistent weak layers, buried at different times and different depths, found on different aspects and different elevations. Two different problems. All the same alarming snowpack. Continue with cautious and conservative travel through the mountains this holiday weekend. Patience is the name of the game with persistent weak layers.

Very cold temperatures make life slow way down. As you're out in the backcountry this weekend, keep in mind that very cold temperatures will add insult to any injury of you, your gear, or your machine. Although several feet of very light snow can make you think you're invincible, myself and several snowmobilers can attest that you and your sled are not invincible. Lots of obstacles are still lurking underneath all of this very light snow. 

The best way for us to know what's happening as more people are out in the mountains is to submit an observation. Submitting an observation improves your skills, informs other users, and benefits avalanche forecasts. Simple photos highlighting conditions are very helpful.

Did you know there several avalanche classes this month specifically for motorized users? Check out our classes and events page to learn more.