Bollettino valanghe

Mount Shasta

Mount Shasta Avalanche Center
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Pericolo valanghe

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

In sintesi

Dangerous avalanche conditions exist across all aspects and elevations in the forecast area. With 15+ inches of new snow and elevated wind speeds, human-triggered avalanches are likely, and natural avalanches are possible. If triggered, a slide could be large enough to bury and/or kill. Conservative decision-making and methodical slope assessment will be necessary to mitigate hazard. 

Problemi valanghivi

  • Storm Slabs

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

    Storm slab avalanches involve new snowfall bonding into a form of slab on top of the old snow. Failure can happen within that slab or at the interface. Peak instability is mostly within a few hours of new snowfall. In the last ~26 hours, this storm has provided ~15 inches of snow. Storm slab instability will still exist across the forecast area on all aspects, at elevations below and near treeline. To complicate the issue, surface hoar has been buried beneath the new snow. The surface hoar will likely increase the sensitivity and destructive size of these storm slab avalanches. Expect these slopes to be reactive to a trigger, such as a ski cut or snowmobile. As the sun comes out later this afternoon, storm slab instability could decrease quickly, but uncertainty lies with the buried surface hoar. Assess avalanche terrain carefully, using small test slopes as an indicator of broader instability. Reduce your risk from this problem by waiting a day or two after a storm before venturing into steep terrain.

    (2/13/2025)

    Small intentional triggered pocket on test slope. This pocket broke above my skis, suggesting a weak grain instability versus the common storm slab instability

    Photo: Samuel Clairmont

  • Wind Slabs

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

    Yesterday, wind blew out of the south at light (1-16 MPH), to moderate (17-25 MPH) speeds. Gray Butte weather station recorded a max gust of 55 MPH. As observed yesterday, elevated wind speeds with large amounts of soft snow is the perfect recipe for wind slab development. Expect to find these slabs on NW-N-NE-E-SE aspects, with cross loading on W and S aspects. Additionally, wind direction will shift to the northwest today, broadening the area of possible wind slab growth. As the wind begins to shift, southerly aspects could load quickly. Look for these slabs on leeward aspects below ridges, on open slopes, and cross-loaded in gullies. If triggered, these slabs could fail up to two feet deep. If failure occurs on the buried surface hoar, there is potential for much wider propagation and unusual destructive size. Use small test slopes of similar aspect to look for this issue. Cracking, collapsing, and unusually deep snow are all signs of wind loading. Avoid this problem by staying clear of steep slopes (greater than 30 degrees) on leeward aspects. 

    (2/13/2025)

    Wind transport on the summit ridge of Gray Butte

    Photo: Samuel Clairmont

Avalanche Discussion

The NWS Winter Storm Warning has expired as the current storm system begins exiting the forecast area. As of now, ~15 inches of new snow has fallen since yesterday, with a couple more inches expected throughout the day today. By end of day, skies will mostly clear, and the early stages of high pressure will begin to show.

New snow and wind loaded snow are the primary concerns for avalanche activity. As the sun begins to show its face, the new snow will become less reactive, with one caveat. Forecasters have identified surface hoar development prior to the new snow, sparking concerns of increased sensitivity and instability across the forecast area. Failures on this layer have already been observed. Approach steep slopes with caution. If an avalanche fails on surface hoar, wide propagation and greater destruction could result. It is unclear, as of now, whether the buried surface hoar will persist over the coming days. 

If you're out in the field today, send us an observation (HERE)! This helps forecasters have a broader picture of the current snow conditions on the ground.

Access: The Everitt Memorial Highway is closed. Estimated opening is next week sometime.  Castle Lake road is also closed. Unknown opening. On Tuesday, a community stakeholder meeting was held in Mt Shasta City with regard to plowing operations for Everitt and Castle road access. We want to share that a passionate, caring and committed group of people are actively moving toward viable solutions for reliable snow removal. Stakeholders recognize the importance of winter access to these areas, and we're excited that momentum is building for near, mid and long-term solutions.  It's a mountain to climb, but this community has some grit!

OPEN - Pilgrim Creek and Deer Mountain Sno-Parks / Mt Shasta Ski Park and Nordic Center / FS31 road motorized/xc-ski access / McBride Springs ski access 

THIS WEEKEND:

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