Bollettino valanghe

Presidential Range

Mount Washington Avalanche Center
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Pericolo valanghe

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

In sintesi

Conditions are dangerous, and large natural avalanches may occur without warning. Steep terrain in the middle and upper elevations is loaded with wind-transported snow that may be sensitive to the weight of a human. Stay on low angled slopes out of the way of avalanche run-out zones.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–3

    With 9 to 12 inches of new snow and wind from many directions, slabs will be thick and primed for human triggering. Expect to find blowing snow and reactive slabs over 3 feet deep in the middle and upper elevations. It is possible for natural avalanches to occur without warning with severe consequences, especially in confining terrain.

    The winds have made a giant sweep across the compass overnight. Yesterday sustained winds over 55 mph were out of the southeast and was moving snow to the northwest aspects. Overnight the winds shifted south then west and eventually northwest as the low passed through the Presidential Range. Gusts of 82 mph were recorded on the summit, blowing snow from ridgelines to the steep terrain below. It could be possible to find firm slabs of wind drifted snow on all aspects of the compass today, but the largest slabs are likely to be found on south and east facing terrain.

  • Persistent Slabs

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

    Poorly bonded grains in the mid snowpack layers are being found in specific areas of our terrain. These faceted snow particles have undergone a physical change from being once a breakable crust, to now a weakened structure that will promote avalanches. Melt/freeze crusts are breaking down after several nights of cold clear weather, and are now a suspicious persistent weak layer that may fail with the weight of new snow or human interference. These facets lie below a few layers of wind blown snow and it will take some investigative work to locate and test their stability.

Avalanche Discussion

A lot has happened to our snowpack in the last 24 hours. Wind from many different directions has moved snow to leeward aspects forming large slabs capable of creating destructive avalanches. 9 to 12 inches of new snow fell on a southeast wind only to be picked up and moved again from extreme northwest winds. Gusts up to 82 mph in the alpine have eroded the newly fallen snow and put it on the steep terrain of our gullies and ravines.

Today is a day for being conservative with your terrain selection. Expect that some slopes had natural avalanches overnight and this morning and that could continue throughout the day. Areas that did not avalanche should be given a wide berth in that they still hold the potential for human triggered failure. Poor visibility and highly variable conditions means that we lack some confidence in just how large and sensitive the new dry slabs are. Areas with weakened snowpack structure add to this overall dilemma. Avoiding steep terrain that looks enticingly filled in will increase your safety.   

The Lion Head Summer Trail is CLOSED due to increased avalanche hazard. The Lion Head Winter Route is OPEN and the most direct route to the Mount Washington Summit from Pinkham Notch. 

OBSERVATIONS: Please consider submitting an observation of what you are seeing in your travels. Submitting an observation hones your skills, informs other users, and improves our forecasts. 

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