Avalanche forecast

Mount Shasta

Mount Shasta Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Dangerous avalanche conditions continue across all aspects and elevations. With more snow, stronger winds, and a weak layer in the snow, the avalanche hazard is more complex than usual. Avalanches could be large, propagate wide, and run into lower angle terrain. Mitigate the hazard with safe travel technique and diligent assessment of snowpack and weather trends.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3

    Wind slab will be the primary problem today. For the last three days, southerly wind has accompanied the new snow, developing large wind slabs on leeward aspects. Today, moderate-strong (7-38 MPH) southwest wind will continue to transport large amounts of soft snow onto leeward aspects, maintaining the likelihood of large and dangerous avalanches. Look for this problem on NW-N-NE-E aspects, with cross loading possible on W and SE aspects. If triggered, these slabs could fail multiple feet deep, enough to bury and kill. Tonight, wind above treeline will become extreme (>38 MPH), likely scouring exposed southerly aspects, and depositing snow in unusual patterns. With such strong wind, loading could occur lower on slopes than usual, and in unusual locations. If headed into the backcountry, diligently assess slopes for instability. Look for shooting cracks, lens shaped surface snow, and unusually deep snow conditions as indicators of wind loading. Avoiding this issue is simple, don't travel in wind loaded avalanche terrain.

    (3/14/2025)

    Wind slab avalanche crown and flank initiated by cornice failure on an east aspect of Gray Butte

    Photo: Mount Shasta Avalanche Center

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    In the next 24 hours, 10–12 inches of new snow is expected. Storm slab will continue to be a concern on all aspects below and near treeline. With temperatures warming through the day, new snow accumulations could be denser than yesterday's snow, or the snow that falls this morning. This could give us a slightly upside-down snow structure, increasing the possibility of storm slab activity. These slabs tend to be quite reactive to the weight of a skier or snowmobiler, and if triggered, could fail large enough to bury a person. If headed into the backcountry, keep your eye out for signs of instability such as significant new snowfall, small failing test slopes, and cracking/collapsing under foot. To avoid this issue, assess steep slopes (greater than 30 degrees) carefully. If in doubt, stick to lower angle terrain, and let the snowpack adjust to the new snow. 

    Forecasters have identified a buried weak layer in the snowpack in the form of graupel. With more snowfall today and tonight, this layer will continue to be tested. If failure occurs, an avalanche could be very large, multiple feet deep, and over a hundred feet wide. As of now, no activity has been observed on this layer. That being said, it's possible. Keep it on your radar as you analyze steep slopes. Extra caution must be taken around avalanche terrain. If in doubt, stick to lower angle terrain. 

    (1/20/2024)

    Soft Slab Avalanche

    Photo: Samuel Clairmont

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Over the last three days, 32+ inches of snow has accumulated at treeline. Most of this snow has remained soft, light, and unconsolidated. Yesterday, forecasters could easily trigger small (D1-D1.5) dry loose avalanches below and near treeline. Today will be more of the same. Though mostly small, these avalanches do have the potential to knock a person over and drag them into consequential terrain. Avoid this issue by waiting a few hours after new snowfall before entering steep slopes.

    (1/13/2024)

    Fresh wind slab that broke onto a leeward aspect entraining dry loose snow

    Photo: Cory Beattie

Avalanche Discussion

Multiple avalanche problems exist across the forecast area. This means increased attention to detail by anyone entering the backcountry. A Winter Storm Warning has been issued starting at 11 am today. Snowfall will continue through the day, increasing into the evening. Strong (25-38 MPH) to extreme (>38 MPH) southwest wind will accompany the snowfall.

Forecasters have been tracking a weak layer in the snowpack: a 1-3 cm thick graupel layer, buried 2-2.5 feet deep. This layer has been confirmed across all aspects in the Gray Butte area, and likely exists elsewhere. As of now, no avalanches have been observed on this layer. That being said, yesterday's pit tests on Gray Butte (ECTP22, PST 25/100) indicated this layer to be moderately sensitive and capable of propagating across slopes. As more snow is added to the snowpack today and tomorrow, this layer will be strained. Failure is possible, which would result in a large-very large avalanche, multiple feet deep. If you're headed into the backcountry today, keep this layer on your radar. Before entering steep slopes, consider the ramifications if this layer were to be triggered.

As forecasters, it's challenging to see multiple zones across the forecast area in a single day. Public observations really help us to hone in the forecast. You can submit a public observation HERE. 

The Everitt Memorial Highway is CLOSED. For further road information: https://www.co.siskiyou.ca.us/publicworks/page/closures-and-delays

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