Bulletin d’avalanche

Presidential Range

Mount Washington Avalanche Center
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Danger d’avalanche

Fri
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Points saillants

Large avalanches will be easy to trigger today, and will likely slide naturally. With over 9 inches of new snow, strong shifting winds, and mixed precipitation; expect unstable snow on all aspects and elevations. Avoiding the avalanche problems today means sticking to low angle slopes and constant reevaluation of the terrain in your vicinity, especially what’s above you.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Certain
    Taille
    1–2.5

    With strong and shifting winds overnight and into today expect slabs of drifted snow to be over 2 feet thick in sheltered locations. Large avalanches will almost certainly run naturally and could very easily be triggered by humans. Shifting winds have cross-loaded steep slopes adding density changes and creating touchy surface slabs. Mixed precipitation may reach the higher summits this morning, adding crusts and weight to already sensitive slabs.

    With the presence of lingering pockets of unstable snow yesterday, we could see avalanche activity peak this afternoon and into this evening as more load is added. An upside-down surface snowpack was observed in the recently drifted snow allowing firm slabs to develop over soft and unconsolidated snow. Steep slopes on many different aspects will be trying to shed themselves today, and it will be difficult to stay out of harm's way if you are traveling in avalanche terrain.

  • Storm Slabs

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

    With over 9 inches of new snow blanketing our slopes, expect to find thick slabs on steep slopes ready to avalanche. Natural avalanches are likely and human triggered avalanches are almost certain on slopes over 35 degrees. As snow moves around today and settlement occurs expect slabs to stiffen and grow more sensitive this afternoon. Storm slabs will be found in areas devoid of wind where boot penetration is calf deep or more. 

    Look for cracking in the surface snow and anticipate avalanches sliding at or just above the old firm snow surface, or at an old icy crust layer. Mixed precipitation will exacerbate this issue, by adding weight to already unstable slabs trying to cling to steep slopes. 

Avalanche Discussion

Ample new snow overnight and into this morning, amounting to 9.1 inches by 5:30AM, will increase the risk for slab avalanches in our steep terrain. Coupled with the new snow is shifting winds and the threat of mixed precipitation this morning. Natural and human triggered avalanches could be large and unsurvivable in the wrong locations. 

The question we are asking ourselves today is, what will the mixed precipitation do to our growing slabs. Early observations show moist snow and thin ice crusts forming in the lower elevations with heavy wet snow. The problem is the unconsolidated dry snow that lingers underneath these slabs giving them little to no support. This snowpack recipe is ripe for avalanches occurring naturally due to added weight and stress exerted on already weak snowpack layers.

Régions couvertes