Bollettino valanghe

Mount Shasta

Mount Shasta Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The forecast area received over two feet of new snow and strong wind in the past 48 hours. You could trigger an avalanche on leeward aspects, near and above treeline, where wind has caused excessive amounts of snow to accumulate. Evaluate the snowpack carefully, looking for signs of instability before committing to avalanche terrain.

Problemi valanghivi

  • Wind Slabs

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

    That 2 to 3 feet of new snow we picked up on January 31 is still available for transport. Southerly wind has and will continue to build drifts on leeward, SW-W-NW-N-NE-E, aspects. 

    Staying off and out from under avalanche terrain will keep you from being caught by an avalanche . You can travel in windward or low angle terrain to assess slopes for wind slabs and watch for signs of instability: shooting cracks, collapsing and whumpfing snow. 

    (12/2/2023)

    Example photo of a wind slab cracking.

    Photo: Samuel Clairmont

  • Cornices

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

    Recent heavy snow accompanied by strong southerly wind built new cornices and grew existing ones larger. Yesterday we documented a natural soft slab avalanche triggered by cornice fall. It is a typical occurrence that when one cornice is weak enough to fail, that others are too. They are typically at their weakest following a period of intense wind loading or warming temperatures. The likelihood of this problem is on the decline as wind dies down and temperatures continue to dip. With that being said, when a cornice falls onto the slope it is a sudden, heavy load on the snowpack. The snowpack does not like this rapid change and it may trigger a large wind slab avalanche. You can avoid cornices by giving them a wide berth on ridge lines and limiting your exposure on slopes beneath cornices. Learn more about cornices here.

    (2/1/2024)

    A ridge running from east to west with apparent wind loading and cornice growth to the north (pictured left)

    Photo: Cory Beattie

Avalanche Discussion

Siskiyou County has reopened the Everitt Memorial Highway to Bunny Flat following yesterday's storm induced closure. Those hardworking folks are crucial to providing us with safe and open routes for winter backcountry access. Mount Shasta wouldn't be the same place without them. 

As we lower the avalanche danger scale from high to moderate, it is important to evaluate the snow carefully before committing to travel in avalanche terrain. Yesterday, the road closure limited our observations on Mount Shasta so there is uncertainty as to what the snowpack is like up there. Instead, Nick and I went to the Eddy Mountains to conduct one of our monthly snow surveys near Deadfall Lake to assess the amount of snow and its water content. The data collected is crucial to forecasting how much water will be available for downstream users in the Trinity and Sacramento watersheds. The average snow depth is 51 inches and there is 13.5 inches of snow water equivalent (SWE). At this location, new snow totalled 15 inches of damp, supportable new snow. Similar conditions are likely present below treeline on Mount Shasta; near and above treeline will host deeper and drier snow. 

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