Bollettino valanghe

Mount Shasta

Mount Shasta Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Low-density snow, westerly winds, and continued cold temperatures have produced a variety of avalanche problems across the forecast area. Wind slabs will pose the largest risk, with large avalanches likely on leeward slopes. Natural avalanches are possible above treeline, and human-triggered avalanches are possible in all avalanche terrain. Conservative decision-making and methodical slope assessment will be necessary to mitigate hazard. 

Problemi valanghivi

  • Loose Dry

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    The low-density, dry, condition of the recent 2+ feet of snow will present the opportunity for dry-loose avalanches. This type of avalanche tends to start at a single point and entrain more snow as it fans out and moves downhill. Though they are often not very hazardous, these avalanches can entrain a fair amount of snow, taking you off of your feet. Expect to find these avalanches in steep to very steep terrain. Manage your exposure by performing ski cuts, using safe zones, and skiing in less consequential terrain.

    Credit: Univ of British Columbia

    Example of dry loose avalanches

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–3

    Yesterday, observed wind was calm below treeline, but visible and audible above tree tops. Gusts reached up to 36 MPH out of the west. Near treeline, 3-4 foot tall drifts could be found on flat terrain, signaling the intensity of transport that has occurred. West-southwest wind will continue to transport snow today. The recent cold temperatures have preserved the dry, low-density snow, allowing for easier wind transport and accumulation. With 25–30 inches of new snow since Thursday, there is potential for large to very large wind slabs to be lingering on leeward (SE-E-NE-N) slopes. Cross loading is possible on northwest aspects. Blowing snow and cracking or collapsing in drifted snow are clear warning signs of the problem.  Wind Slabs can be avoided by sticking to sheltered or wind-scoured areas. To limit your exposure to wind slab problems, cautious route-finding, and careful slope evaluation will be necessary.

    (1/7/2024)

    Wind Slab

    Photo: Cory Beattie

  • Storm Slabs

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

    Storm slab avalanches are generally associated with the new snowfall developing a slab on top of older snow, and failing in between or at the interface. Peak instability mostly exists within hours of new snowfall, but can be prolonged by continued loading and cold, cloudy conditions. This instability still exists throughout the forecast area today. Expect to find this problem anywhere the new snow has fallen in below and near treeline terrain. These avalanches will likely be resistant to trigger, but possible given the right conditions. If triggered, these avalanches could fail on a density change within the new snow or as deep as the 30 inches to the old snow. Assess avalanche terrain carefully, performing ski cuts, and watching for shooting cracks. Reduce your risk from this problem by waiting a day or two after a storm before venturing into steep terrain.

    Example of Storm Slab Avalanche

    Photo: Samuel Clairmont

Avalanche Discussion

A NWS Winter Storm Warning is in effect until 10pm this evening, and a Winter Storm Watch will be in effect starting at 10am tomorrow. Yesterday's observations found 25–30 inches of new snow at treeline since Thursday (2/29). Snow totals drop at lower elevations, ~20 inches at 6,000 feet, and ~8 inches at 5,000 feet. Today and tonight, snow accumulations will slow to a trickle, before picking back up tomorrow with the arrival of a new system. 

Throughout this storm, we have yet to see any natural or human-triggered avalanche activity. That being said, we have all the necessary ingredients, and the numbers never lie. Multiple different avalanche problems currently exist across the forecast area that could hurt or bury you. Due to the weather conditions, observations have been limited in terrain above treeline, where the highest avalanche danger currently exists. If stepping into the backcountry today, approach steep slopes with caution. Have a good back up plan and escape route. Use safe zones to limit party exposure.

The Everitt Memorial Highway and Castle Lake roads remain closed. The timeframe for opening it still unknown.  Alternative access points include McBride Springs, the Nordic Center, Mount Shasta Ski Park, and Pilgrim and Deer Mountain OSV parks. You can ride a snow machine from FSR 31 road (Old McCloud) up to Old Ski Bowl. Please stay in boundaries. Here's a map of the riding boundaries for the Southside of Mount Shasta.

Thank you to everyone who attended the Know Before You Go / Avalanche Awareness talk last night. Today, 9am at Sisson Ball Park (in town), we will be providing a free transceiver clinic for anyone who wants to learn more or just needs a refresher. Come join us!

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