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
Senza grado
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Non aggiornato — questo bollettino è scaduto 5 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You could trigger an avalanche on north, east, and south-facing slopes above 3000 feet. While you may see blowing snow and shooting cracks, look for smooth pillow drifts to identify areas of potentially unstable snow. Travel on firm surfaces to reduce your chances of triggering an avalanche today. 

Problemi valanghivi

  • Wind Slabs

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

    What and where is it: You may encounter various wind slabs built over the past few days from the 10.2 inches of snow recorded at the summit since Sunday. You are most likely to encounter these in north, east, and south-facing terrain. Today’s initial increasing west and southwest winds may stiffen snow surfaces and continue to load buried weak layers. 

    Slabs may be small if it is just new snow on a thin rimed crust (D1), but if you are finding deeper drifts all the way down to the stout melt-freeze crust, you are finding the larger problems (D2). While you will be less likely to encounter it, do not rule out that northeast and east-facing terrain could harbour isolated buried drifts that are larger in size (potentially up to D2.5). 

    How can you recognize it: Snow surfaces were generally evenly blanketed with yesterday’s new snow. Look out for areas that appear smooth and pillowy, as this could be a larger drift. If there is still snow available for transport, you may see snow blowing at ridgelines, which is a sign of forming wind slabs and more sensitive slabs. Use a pole, probe, or your foot penetration to help you understand the thickness of a slab and the size of a potential avalanche today.How can you manage it: With some changes over the past few days and increasing winds this morning, you will need to gather more information before committing to traveling across steep terrain. Look to see if increasing winds are blowing snow and stiffening snow surfaces. Use hand shears and column tests to understand slab sensitivity. Remember that slab depth and sensitivity could vary based on your elevation and aspect. 

Avalanche Discussion

Recent forecaster observations (Obs 1, Obs 2) have found poor snowpack structure within the new snow found on top of the stout melt-freeze crust. If slabs are only sensitive on top of a thin rimed crust, the size will be small, whereas if it encompasses all of the snow down to the melt-freeze crust, avalanches could be large. 

The big questions for today are how much snow is available for transport, and what will increasing winds do. 

For snow available for transport, solar gain and riming may limit and cap snow surfaces, preventing it from being redistributed. Overnight, the Mount Washington Observatory recorded that the height of snow went from 8 inches at 6:55 PM 3/24 to 5 inches 6 hours later at 1:55 AM 3/25. The other component is that with significant snowpack loss in the alpine, new snow falls onto rocks and is more difficult to redistribute than it falling on smooth, planar snow surfaces. While the snowpack is improving in the alpine, in many areas it is still disconnected, which may limit loading potential. 

The increase in winds has been driving an increase in avalanche hazard; however, the wind speeds recorded have been on the lower side of what has been forecast. Today, winds are forecast to increase to 50-70 mph early, before decreasing throughout the afternoon. This could transport snow, stiffen snow surfaces, and build slabs that are on top of poor structure deeper in the snowpack.

Enter avalanche terrain prepared to gather more information and track changes driven by the wind throughout the day. 

OBSERVATIONS: Please consider submitting an observation on our website or in the new Avy phone app 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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