Bollettino valanghe

Salmon River Mountains

Payette Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Natural and human-triggered wet loose avalanches are likely on sun-drenched slopes. Wet, loose avalanches that gouge deeply into the snowpack could trigger a larger slab avalanche. Large, overhanging cornices are unstable; give them a wide berth. If you are seeing fresh avalanches and or sinking in past your boots, find another aspect out of the direct sun or call it a day.

Problemi valanghivi

  • Loose Wet

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

    Wet loose slides are most likely on the southern half of the compass and will follow the sun throughout the day (beginning on east-facing slopes in the morning and ending on west-facing slopes in the late afternoon). Some of these avalanches could be large enough to bury you. Don't rule out wet loose activity across multiple aspects on lower elevation slopes. Rollerballs, or small snowballs peeling off steep terrain, can be a helpful clue that the snow surface is weakening and that wet slides may occur. If you find yourself sinking into wet, mushy snow, it's time to find a different aspect or call it a day. Wet, loose avalanches begin at a point, usually the base of a warm rock or tree, and fan out, picking up snow as they move. Wet-loose avalanches are most problematic in confined terrain or on steep slopes, where they can accumulate large amounts of snow. These avalanches can gouge deeper into the snowpack, triggering a larger avalanche.

    This recent observation highlights the wide variety of snow surfaces you can find throughout the day. Subtle differences in the weather, such as wind chill and cloud cover, can make a big difference in how the snow surface is either freezing or melting. Differences in terrain, like aspect and elevation, can significantly change the flavor of the snow surface.

    This photo highlights small, wet, loose avalanches originating from rocks catching the afternoon heat.

Avalanche Discussion

We are going into day 4 of above-freezing temperatures in the mountains. We've seen the snowpack shrink and settle by 6-8 inches over the past several days. This record-breaking heatwave has delivered a rapid change to the snowpack. Today will likely be the warmest day of the period. We have not observed a large, widespread wet avalanche cycle thus far. Today could be the day. If we could add a large question mark for an avalanche problem, we probably would. Strange, anomalous weather events can lead to a lot of head-scratching with avalanche forecasters. Sometimes the snowpack does not respond to dramatic changes the way you anticipate. Plan for uncertainty if you head into the mountains today. Wet snow avalanches are all about timing. Wet loose avalanches can be more manageable than large, wet slab avalanches. Forecasting wet avalanches is difficult and uncertain as to the exact timing of release. Even small, wet slides can build quickly and become a problem on exposed slopes and in terrain traps like gullies, creeks, cliffs, and rocky, thin terrain. Pay attention to the snow surface with questions like: How solid did it freeze last night? How quickly is the crust breaking down? Am I sinking into wet, mushy snow deeper than my ankles? How is the weather (cloud cover, wind, temperature) impacting the snow? 

ADDITIONAL CONSIDERATIONS: 

  • CORNICES - During prolonged warm periods, large, overhanging cornices become unstable. Some of these monsters can break off naturally or by the weight of a person. Give all cornices a wide margin, and be careful along ridgelines as they can break much farther back than expected. Limit your exposure underneath them. With several days above freezing and more direct March sunshine, a cornice fall could trigger a larger, persistent slab avalanche. 

  • PERSISTENT SLABS - Triggering a deeper, persistent slab avalanche has been unlikely. However, with three days of record heat in the mountains, there is uncertainty as to how these persistent slabs will respond to the dramatic change in the snowpack.  Extremely warm temperatures, the weight of a cornice fall, or large gouging wet, loose avalanches could awaken these deeper weak layers. These could be wet or dry persistent slabs. We haven't observed the meltwater percolation to suspect wet slab activity. Persistent slabs should be a topic of conversation within your group today.

If you're out in the mountains, submit an observation on our website or through the Avy App. Tag us #payetteavy

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