Avalanche forecast

Mount Shasta

Mount Shasta Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A low-pressure system will deliver strong southwest winds and 6–12 inches of new snow to the forecast region over the next 24 hours. Avalanche danger will rise rapidly near and above treeline as winds craft fresh drifts on leeward west, north and east aspects. Avoid traveling on steep slopes that have been receiving active wind loading for extended periods of time, and assess wind-textured slopes for signs and symptoms of wind slab. Adopting a conservative mindset and using safe travel techniques will serve you well today. 

Avalanche problems

  • Wind Slabs

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

    A strong storm system has arrived and will persist throughout the daylight hours. As snowfall rates intensify and strong south and west winds begin to blow, dangerous avalanche conditions will develop near and above treeline on slopes steeper than 35 degrees. Wind slabs will be possible at all elevations, with the strongest presence near and above treeline. Expect wind loading to occur on leeward W-NW-N-NE-E aspects, with SW and SE aspects subject to cross-loading. Drifts will form fast and thick on the leeward sides of ridgelines, cliff bands, and convex rollovers. In the right areas, slab depth will be deep enough to bury you. Observe for growing signs of instabilities, like large shooting cracks, recent avalanches, and active wind loading, as these signs indicate avalanche danger is present. Consider the rate of surface slab growth, and its cohesive properties. Using representative and inconsequential test slopes is a great way to assess the trend of stability and how the new snow is bonding to old bed surface. Areas worth avoiding are wind effected slopes that sit directly below ridgelines, on steep mid-slope breakovers, or nestled among rocky pockets of terrain.   Firm surfaces will receive the new storm snow, and bonding capability may not be adequate in areas that have been previously scoured or formed crusts. Slabs and sluffs of storm snow are possible in steep, protected areas of terrain that host more than five inches of fresh, unconsolidated snow.     Today is a scenario where the higher you travel in elevation, and the more you expose yourself to the weather and steep terrain, the more you're going to be at risk. Wind-textured surfaces are evidence of wind loading. Wind slabs will display as stiffened snow surfaces with dune, or pillow-like appearances. Conservative travel and decision-making will help decrease your risk and exposure to this problem. 

    (3/10/2024)

    Cracking. A red flag of avalanche danger, which signifies present surface instability. 

    Photo: Samuel Clairmont

Avalanche Discussion

As we enter back into a period of stormy weather, it's prudent to adjust your mindset to fit the environment. There is a moderate amount of uncertainty about how the new snow will bond to the old, and if pre-existing surface crusts will support it. Yesterday, on a tour up Giddy, Giddy, Gulch, a surface crust was observed on south and west aspects near and below treeline. These crusts ranged in thickness from centimeters to inches. West aspects held the thinnest and most breakable crusts, compared to south aspects, which were thicker and more supportable. 10 inches of dry snow was discovered beneath, sitting atop a firm bed surface. This poor snowpack structure is a recipe for an avalanche, and the existing crusts may be the weak layer.    Dialing back your exposure and engagement with avalanche terrain today is a worthwhile practice. 

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