Bollettino valanghe

Presidential Range

Mount Washington Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
1 · Debole
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In sintesi

Yesterday’s storm left us with dangerous avalanche conditions.  Human-triggered avalanches breaking 2-3 feet thick are likely on steep easterly slopes. While becoming less likely as the day progresses, we can't rule out the chance of natural avalanches especially on steep east facing terrain at middle elevations.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2.5

    Strong northwest wind overnight has drifted the 11-15 inches of new snow, creating large wind slabs up to 3 feet thick primarily on east and southeast facing terrain at middle and upper elevations. In east facing ravines, cross loading has built smaller wind slabs on many aspects which are still potentially dangerous when found in steep terrain. 

    High wind speeds increasing the surface density of new slabs and spatial variability  may limit the usefulness of shooting cracks as an indicator of instability today. Hard slabs may be harboring a weak soft layer buried early in the storm under light winds, meaning the first crack in the snow surface you see could be the start of an avalanche, not a red flag. Look for smooth pillows of snow to help identify the new wind slabs and keep terrain choices conservative.   

    Natural avalanches are possible today, especially while wind loading is active. Look for blowing snow at the ridgelines as a red flag.

Avalanche Discussion

Snow totals from yesterday’s storm were affected by temperatures and elevations. The summit of Mount Washington received over 11 inches of nearly all snow while warmer temperatures at low elevations within the forecast area provided a mix of rain and wet snow settling quickly. Sparse or nonexistent bed surfaces and lower storm totals are keeping the hazard rating at LOW at lower elevations. Human triggered avalanches are unlikely but not impossible at low elevations. 

Temperatures yesterday started warm and dropped throughout the storm. While this setup typically provides a “right side up” snow structure, wind will be a more significant factor for buried instabilities within the new snow. Given the warm temperatures at the start of the storm, we can expect the new snow to be bonded well to the existing bed surfaces. However, yesterday’s wind started light for the first few hours of the storm and steadily increased into the evening.  Softer, weaker snow may be lurking underneath denser snow which was transported and loaded at higher wind speeds.  The surface snow may be enough to support the weight of a human in many areas, but could fail on a weak spot or thin spot in the slab. 

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.

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