Avalanche forecast

Mount Shasta

Mount Shasta Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 6 months ago. You’re viewing past conditions, not the current bulletin.

Highlights

Human-triggered avalanches large enough to bury a person are possible on slopes steeper than 35 degrees in wind-loaded terrain near and above treeline. Carefully evaluate leeward features for signs of unstable snow. In sheltered areas, watch for lingering instabilities in the new storm snow. Precipitation will pick back up late in the day with avalanche danger rising to Considerable overnight into tomorrow. 

Avalanche problems

  • Storm Slabs

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

    Yesterday's pulse of moisture produced about a foot of low-density snow near treeline and small slabs were reactive to skier input on test slopes in both sheltered and wind loaded areas. In the last 24 hours, winds have been mostly out of the NW and WNW over the last three days. Today wind slabs near and above treeline are more widespread on N through E through SW aspects. They will be confined to slopes greater than 35 degrees on the leeward side of ridges, rock outcrops, gullies, and rollovers. Areas directly beneath prominent ridgelines will hold the deepest drifts. Look for clues such as fresh cornices, wind pillows, and blowing snow to alert you to potential locations. Windward slopes and scoured terrain will offer the safest riding. 

    In sheltered areas near and below treeline, watch for signs of instability in the recent snow. Lingering reactivity is more probable on the shadier aspects which did not receive any sun yesterday and have remained cold. While any avalanche is expected to be smaller in size, be aware of terrain features beneath you that could increase the hazard of getting caught, such as cliff bands or terrain traps.

    For both problems, use inconsequential test slopes to gauge the snow’s stability. Shooting cracks underfoot or machine indicate unsafe conditions and should direct you to simpler terrain.

Avalanche Discussion

Yesterday, a natural D2 wind slab was sighted off Green Butte Ridge at around 10,000 feet. The observation can be viewed here. While natural activity is unlikely today, this is a good representation of the type and size of avalanche that could be triggered below ridgelines in the alpine today. For those travelling on exposed ridges, be sure you know where you are in relation to freshly formed cornices. They may be more overhung and brittle than you expect. 

If the sun makes an appearance, snow surfaces on steep (>35 degrees) solar-facing terrain may begin to lose cohesion, especially around rocky areas. If you see or can trigger rollerballs or pinwheels, wet loose avalanche potential is increasing. While an unlikely scenario, it is worth mentioning because the cold, dry snow is more susceptible to subtle changes in solar input.

Forecasters have been tracking several weak layers in the snowpack. Graupel layers have been identified within the Feb. 14 - 16 snow, at the underlying interface and early on in yesterday's storm. Two days ago, a crown was noted from Bunny Flat above the Powder Bowl drainage. The avalanche appears to have failed about one to two feet deep, presumably on the lowermost graupel layer and propagated a hundred or so feet wide. Faceted snow exists in many areas beneath a crust that is thickest on solar aspects and thinnest on shadier aspects. With additional loading, the strength of the crust may be tested, especially on the shadier aspects where it is thinnest. 

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