Bollettino valanghe

Mount Shasta

Mount Shasta Avalanche Center
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Pericolo valanghe

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

In sintesi

Unstable areas of wet surface snow and wind drifted snow exist in terrain near and above treeline. Wind slabs linger in upper elevation terrain, near ridge tops and exposed slopes, where an avalanche could be large enough to bury you. Wet loose avalanche hazard will build through the day as solar heating destabilizes surface snow on southerly aspects. Evaluate terrain choice and travel decisions cautiously. If in doubt, avoid wind effected slopes and exit avalanche terrain before significant warming occurs.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Over the last 24 hours, the dominant wind direction has shifted from the previous southerly, to northwest. This means there could be a few different aspects where lingering wind slabs from the southern winds exist, and where new slabs have developed from the northwest wind. Yesterday's field observations showed large areas of wind loading across W-NW-N aspects where wind slabs sat on top of soft, unconsolidated snow. These slabs were reactive to skis, breaking a foot deep. Wind loading on E-SE-S aspects could be seen occurring all afternoon from the northwest wind. Look for wind slabs in above treeline terrain, on W-NW-N-E-SE-S aspects, with cross loading possible on northeast and southwest aspects. Slabs could be quite reactive to skis, and breakup to 1 foot deep. If triggered, these avalanches have potential to bury you.  Keep your eye out for shooting cracks, failing test slopes, and hollow sounding snow drifts. If in doubt, avoid avalanche terrain on leeward aspects around ridge tops and exposed slopes.

    (3/24/2024)

    Intentionally triggered wind slab. 11,500 feet, west aspect.

    Photo: Samuel Clairmont

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Yesterday's field observations presented wet loose avalanches on southerly aspects across all elevation bands, with roller balls and pinwheels on most other slopes. These avalanches will likely show greater reactivity today. Though temperatures will only climb slightly from yesterday, the large amount of solar input during these long March days will provide radiative heating to all exposed slopes. This problem will mostly exist on solar aspects, primarily SE-S-SW-W aspects. Low elevation, northerly aspects are beginning to show signs of warming as well. Expect snow to become increasingly unstable as the day progresses, and slopes receive more and more sunlight. Monitor snow surfaces closely. Hand pits, test slopes, and the general feel of surface snow will provide valuable feedback on snow stability. If the surface snow begins to feel sticky, clumpy, or “upside down” (where heavy snow is on top of light snow), it's about time to exit avalanche terrain.

    Small entrainment of wet loose snow. An indicator of rising surface instability. 

Avalanche Discussion

Yesterday, forecasters visited upper Green Butte Ridge / Avalanche Gulch, and the Eddy Mountains. On the south side of Mount Shasta, upper mountain conditions are looking excellent. The recent new snow has smoothed out most slopes, added 14+ inches of snow, and burying the old surface crust. The northwest winds kept exposed slopes and ridgelines cold, and reduced the effects of solar warming. In sheltered areas, wet loose avalanches and icefall began to occur by midday. Wind drifted snow was found along NW-W aspects, showing easy reactivity to ski cuts.In the Eddy Mountains, the recent storm did not provide as much snow. Deadfall basin accumulated 4–6 inches, with variable areas presenting up to 10 inches. The northwest wind picked up quickly, scouring ridgelines of soft snow, and quickly transporting it onto leeward slopes. Small, reactive slabs could be found with ease.

Today, the warming trend will continue to destabilize surface snow in wind sheltered areas. As temperatures heat up, icefall will begin to occur from rock faces such as the Red Banks, Casaval, Trinity Chutes, Shastarama and more. If you're going above 10,000 feet, a helmet would be a good choice. To mitigate your risk, don't spend a lot of time down slope from these features.

Another storm system is already within view. These clear conditions will likely only last till midafternoon on Tuesday, then clouds start to build. Snow is expected for the latter half of the week. More on that later!

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