Bollettino valanghe

Presidential Range

Mount Washington Avalanche Center
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Pericolo valanghe

Sun
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Both the size and chance of triggering avalanches increase as you move up in elevation from 3000 feet. To reduce your risk, you can avoid steep slopes with stiff, wind-drifted snow at the surface. On slopes sheltered from the wind, triggering a large avalanche is much less likely. Be prepared to manage sluffs at middle elevations.

Problemi valanghivi

  • Wind Slabs

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

    What and where is it: With 5.5 inches of new snow and shifting winds overnight, conditions are favorable for wind slabs in steep terrain on several aspects above 3000 feet.  With light to moderate wind speeds, slabs will be stiffer and more widespread in upper elevation terrain.Small slabs may be found high in the terrain on many aspects, but the largest and most cohesive drifts will be most likely on easterly aspects, where the west/northwest fetch is typically most effective at transporting snow.

    How can you recognize it: Look for smooth, rounded pillows, stiffer snow over softer snow, and drifting or blowing snow. Expect the most reactive slabs where you find cracking, shooting cracks, and strong over weak structure. How can you manage it: Avoid or carefully evaluate fresh wind-loaded features, particularly in upper start zones and along ridgelines. As you move uphill, monitor for deeper drifts that are stiffening with elevation. The transition may be subtle: softer, less wind-affected snow at middle elevations gradually giving way to slightly denser, more cohesive drifted snow higher in the terrain. Even if slabs remain soft, increasing stiffness within thicker slabs signals that the snow may be capable of propagating and sliding.

    Use your pole frequently to feel for changes in structure. Look for rounded pillows, smooth or slightly supportable surfaces, and areas where snow feels more cohesive than adjacent terrain. Cracking or small shooting cracks are direct signs of instability and if winds continue transporting snow, reassess aspect and elevation as you travel - the most reactive drifts may migrate as the wind shifts.

Avalanche Discussion

Sluff Management: Another thing to keep an eye on today is how the 5–6 inches of new snow at middle elevations is behaving. At these elevations, the new snow is less likely to have formed cohesive slabs and more likely to act as loose dry snow, creating a sluff management issue rather than a true avalanche problem. The key question is how well the new snow is bonding to the older, refrozen snowpack beneath it. If adhesion is poor, the new snow may slide or sluff easily on steep terrain and in steep or exposed terrain this carries the potential for a sliding fall with serious consequences.Forecasters have some uncertainty about wind slab size on east aspects. The setup is there with 5–6 inches of new snow and shifting winds, but warmer, denser snow early in the storm and early southeast winds may have limited transport. Slab size will largely depend on how long northwest winds persist—an earlier shift to north/northeast would keep slabs smaller than the upper-end D2 potential, while sustained northwest wind could build thicker, more cohesive slabs in upper start zones.

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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