Bollettino valanghe

Presidential Range

Mount Washington Avalanche Center
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Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

New snow overnight and daytime warming will affect the stability of surface snow and increase the potential for large avalanches. Dry wind-drifted slabs early in the morning will transition to afternoon moist slabs, changing the dynamics of the snow throughout today's Moderate hazard rating. Timing and aspect is critical for avoiding the changing avalanche problem.

Problemi valanghivi

  • Wet Slabs

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

    As temperatures rise close to 40F degrees at mid elevation this afternoon, expect surface slabs to become moist and less stable. Slopes that are oriented south will experience the most warming, with southeast aspects gaining a bit longer sun exposure. This avalanche problem will be directly correlated to timing, and how quickly warming is likely to occur. Ski/boot penetration and the surface characteristics of the melting snow can indicate the severity of this problem. Small loose wet avalanches and roller-balls are an early sign that the warming trend is underway.

  • Wind Slabs

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

    Overnight snow showers have accumulated 2.7 inches of new snow, with around 10% snow-water equivalent, near the summit of Mount Washington. Moderate northwest winds will move snow to eastern aspects creating new slabs of wind-drifted snow. Some new wind drifts will grow to depths of 8-10 inches and may sit atop older slabs from the past few days. Although relatively unlikely, it is possible that human triggering of a surface slab may allow a step-down avalanche into the older and thicker wind-drifted slabs, creating a larger avalanche.

Avalanche Discussion

As we transition to a spring snowpack, pay attention to the afternoon high temperatures and how quickly daytime warming occurs. Faster rates of warming will decrease the stability of the snowpack exponentially. Timing becomes critical for avoiding your exposure to wet loose and wet slab avalanches. Earlier departures and traveling on firm and frozen surfaces in the morning allows you to gauge your descent before the snow is saturated. Planning your ski adventures after an overnight refreeze and before the midday heat is advised.

Overnight snow showers with low elevation rain have affected the surface snowpack. Melting snow and rain below 3500 feet has decreased the integrity of the snowpack at the lowest elevation zone, exposing creeks and bare ground in some locations. The middle and upper elevations gained 2.7 inches of new snow on the summit of Mount Washington, and +3 inches at the Harvard snowplot. The recent snow has been blown into drifted slabs on a broad range of aspects facing east. New slabs have formed on top of older slabs with some minor density changes occurring mid-storm.

Observations suggest good bonding of the older slabs to the firm bed-surface that previously existed. Winds have cast the snow from the March 11th storm more widespread than initially anticipated, making popular ski descents look more full and attractive visually. Wind-drifted slabs can range from 4Finger to 1Finger in hardness and seem stubborn to human triggering. Soft snow can still be found in the upper elevations in isolated areas, especially around areas that are wind protected.

Thanks to everyone for taking the time to submit observations of snow and avalanche conditions, both inside and outside our avalanche forecast area. Please keep them coming.

The Lion Head Summer Trail is closed for the season due to avalanche risk. The Lion Head Winter Route is open.

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