Bulletin d’avalanche

Presidential Range

Mount Washington Avalanche Center
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Danger d’avalanche

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

Points saillants

Expect wind slabs to be sensitive to a human trigger unless you can carefully confirm otherwise. Slopes and gullies have grown significantly in width and length giving room for avalanches to grow larger and run further. Yesterday's danger rating was almost considerable in these areas. Today is similar. A spike in wind speeds last night blew even more of the low density snow into sheltered steep areas. Expect reactive wind slabs with natural avalanches areremaining unlikely but not impossible, especially on the steepest slopes that hold this drifted and accumulated snow. The danger rating is MODERATE due to the potential to trigger these wind slabs. Evaluate snow and terrain carefully. 

The Lion Head Summer Trail remains the best option if climbing to the summit from Pinkham Notch. Be sure to check the slatboards for the trail status.

Problèmes avalancheux

  • Wind Slabs

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

    Wind slab avalanches are possible to trigger in east facing terrain. The low density snow that has fallen over the past two days has been drifting into new wind slabs that are likely to be sensitive to a person climbing or skiing. Look for smooth pillows of snow at the bases of steep pitches of ice or buttresses in addition to the sides of steep gullies. These are not the hard wind slabs we see after high wind events and will be more easily triggered as a result. Step down potential though the 1/16 ice crust remains uncertain.

  • Loose Dry

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

    Loose dry snow will likely release easily. These point release avalanches are not likely to be much of a problem in our limited terrain but could add mass to a slope and may cause a wind slab to fracture and slide.

Avalanche Discussion

Low visibility yesterday limited the number of incoming observations but drifting snow was observed in Left Gully and at the ridgetop near the Lion Head trail traverse. Snow pits confirmed that there is plenty of snow above the 1/16 ice crust to build into wind slabs. Wind speeds, since this period of “sleeper pow” began, have been unusually low and have likely preserved the crystal structure of the fallen snow. The more typical high wind speeds tend to break up and round particles into smaller fragments that pack into dense slabs. While we aren’t seeing any intense loading as during a more typical 45-60 mph west wind event, the 3-6% snow density we’ve seen in the past 48 hours means that the slabs may be teetering on the edge of release with only a small load needed for a trigger. This load could be a bit more snow sluffing down but it could easily be a person booting up the Chute bringing the entire wind slab down on themselves. 

Point release avalanches were observed on Mt Willard on Tuesday with knee deep slabs along the bases of cliffs. Snowfall totals have been lower there but  caution in areas where the new snow has accumulated is warranted.

Régions couvertes