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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Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Dangerous avalanche conditions continue. One to two feet of new snow, moderate-strong wind, and weak old snow underneath has spiked instability in the snowpack. Natural avalanches are possible, and human-triggered avalanches are likely. Careful snowpack evaluation and safe backcountry travel technique will be crucial today.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    Wind slabs are likely on N-NE-E-SE aspects, with cross loading possible on S and NW aspects. In the last 24 hours, wind speeds hovered around the moderate range (17-25 MPH), which is historically the best speeds for wind slab development. Yesterday's observations from Gray Butte also showed intense wind loading onto leeward slopes. If initiated, slabs could fail up to 3 feet deep and over a hundred feet wide. Expect easy reactivity to a trigger such as a skier, snowmobile, or climber. In some cases, these slabs could release naturally. Areas of wind-loaded snow will present under cornices, ridges, cliff bands, and on convexities with a lens shape over the surrounding snow. If headed into the backcountry today, caution must be taken around these wind-loaded slopes. Some examples of areas to be cautious of are Sun Bowl, Powder Bowl, Middle Peak of Castle Lake, and the east aspect of Gray Butte. The best option is to avoid steep leeward terrain altogether.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    Storm slab development is likely on all aspects below and near treeline. One to two feet of new snow has fallen in the last 24 hours, with four to eight inches expected in the next 24 hours. These slabs will be reactive to ski cut, and potentially release naturally.  If triggered, failure could be as deep as the new snow-old snow interface (1-2.5 feet deep). This new snow sits on top of extremely firm and weakened old snow, contributing to the instability of the new snow. Vigilant snowpack assessment will be key today. Watch for shooting cracks, collapsing, and failing test slopes as indicators of storm slab instability.

Avalanche Discussion

Storm conditions will continue today, with elevated wind speeds and new snowfall. The snowpack is experiencing a significant shift back into winter, giving us all a good reason to step back and reevaluate terrain selection. Storm slab and wind slab instability are likely across the forecast area, with both problems having potential to bury and kill. To complicate the issue, weakened old snow in the form of Near-surface Facets (NSF's) exist in shaded, wind protected areas. These grains are notorious for deep and dangerous avalanches, thus they must be considered in travel and descent decisions. With continued snowfall, the strength of these grains will be put to the test. At the moment, it's uncertain how much new snow will be needed for avalanches to occur on them. NSF's have most recently been located in gullies, meadows, mid-slope, and at the base of large slopes throughout the forecast area.

If you're in the backcountry today, please consider submitting an observation. This is an excellent way to inform others of what you saw, as well as improve your local avalanche forecast with precise data.

Storm totals thus far:Old Ski Bowl (7,600 feet): 13 inCastle Lake (5,800 feet): 22 inMt Eddy (6,600 feet): 11 in

This Weekend's MSAC Events:Know Before You Go — Avalanche Awareness. February 1st, 7 pm at Deadwood Supply Co. No cost!Companion Rescue Clinic -- February 2nd, 9 am at Bunny Flat. No cost!

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