Boletín de aludes

Presidential Range

Mount Washington Avalanche Center
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Peligro de aludes

Fri
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Human triggered avalanches are likely in areas where wind drifted snow has collected on steep slopes. New snow and strong winds will increase the chance for natural avalanches as the snowpack becomes loaded and more sensitive this afternoon. Careful evaluation or avoidance of the avalanche problems will increase your longevity as a winter backcountry traveler. 

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2.5

    Shifting winds and low density snow from the latest storm has cast soft slabs onto various aspects of the middle and upper elevations. As you ascend these slabs become more firm and sensitive to the weight of a person. Upon visual inspection, the upper snowfields look to be flush with wind deposited snow while ridgeline convexities are scoured. Many wind sculpted pillows and drifted features linger in the steepest of locations, exhibiting cracking and hollow characteristics.

    Light winds with little transport of the new snow yesterday, means there is ample loose dry snow on the fetch of alpine areas. Tonight’s incoming snow and extreme winds will scour and redeposit this collected snow into dense drifts lower on the slopes of the middle elevations. Even though the middle elevations had an active flushing of collected snow from numerous avalanches, the evidence has been mostly hidden from the refilling of wind driven snow. Expect reloaded areas to still have sensitive slabs capable of failing above you.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Observations from the floor of Tuckerman Ravine revealed we have an active persistent weak layer below the new snow at middle elevations. The degraded crust layer that we have been tracking showed its level of sensitivity through audible whumphing and sudden collapses as you stepped onto undisturbed snow. This layer of faceted snow is less than 1cm thick and quite fragile, buried 36cm deep in the location we dug. Failures with only light forces applied, occurred during the first 4 taps in compression tests.

    Some of the large avalanches that happened during the previous storm cycle may have been in response to this poor and weakened snowpack structure. This suspicious layer may continue to be a problem until it is flushed out by avalanche activity, or bridged by firm wind-packed snow. Look for it and test its stability before entering consequential terrain. This avalanche problem can be long-lasting, hard to predict, and have poor outcomes if humanly triggered.

Avalanche Discussion

Good visibility and calm winds yesterday allowed observers to record the aftermath of a large avalanche cycle that happened during the March 1st storm. Many large avalanches slid in prominent ski terrain leaving behind ample debris but no crown lines. The fracture lines usually visible after an avalanche were covered by wind drifted snow, refilling the steep slopes with tender dry slabs. Continued risk of large avalanches today is the reality, especially since we are expecting 2 to 4 inches overnight with extreme winds. 

Sensitive slabs of wind-driven snow coupled with the persistent weak layer we are tracking, is not a safe duo to contend with. Expect the snow to grow more fragile with the additional new loading and gusting winds over 100 mph. If you step off-trail and are finding deep boot-penetration or you hear a rush of air sneak out under your skis suddenly with a whooshing sound, you are treading in dangerous territory. Whumphing and sudden collapses as you walk over snow slabs are RED FLAGS for instability. Look, listen, and feel the layer scheme in the snowpack of the intended terrain you choose to venture in today and proceed hesitantly.

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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