Bollettino valanghe

Mount Shasta

Mount Shasta Avalanche Center
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Pericolo valanghe

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

In sintesi

Heightened avalanche danger continues above treeline, where large wind slab avalanches are possible. Assess steep slopes for signs of unstable wind loaded snow before committing. Due to the warming daytime temperatures, wetting surface snow and wet loose avalanche activity is possible on solar slopes.

Problemi valanghivi

  • Wind Slabs

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

    Wind slab avalanches will remain possible today near and above treeline, with large avalanches possible above 8,500 feet. This problem exists on NW-N-NE-E aspects, with cross loading on NW and SE aspects. Yesterday's warm temperatures and direct sunlight helped immensely in stabilizing wind slab around the forecast area. That being said, the problem is not gone. Yesterday's wind blew out of the west/northwest at light (1-16 MPH) to moderate (17-25 MPH) speeds. Today, wind direction will start out northerly, shifting east/southeast in the afternoon.  Look for cracking, hollow sounding surface snow, and failing test slopes as indicators of wind slab. Watch weather trends through the day, where active wind blowing snow could indicate fresh slabs. Assess for wind loading before committing to steep slopes greater than 30 degrees.

    Wind slab below a ridge on the west side of the forecast area.

    Photo: Nick Meyers

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    This late into the season, it doesn't take much for the snowpack to heat up. Given the impending direct sunlight and warmer temperatures, wet loose activity is possible today. These avalanches should be relatively small, D1.5 or less, though danger still lies in their ability to knock someone off their feet. Even a small wet loose avalanche could carry someone into trees, cliffs, or other hazardous terrain. This problem is possible on W-SW-S-SE-E aspects during peak daytime temperatures. Avoiding this issue is simple, exit steep solar slopes before peak daytime temperatures. Sticky wet surface snow, roller balls, pinwheels, and punchy snow surfaces are all signs of rising wet loose instability.

    Roller balls on the west face of Gray Butte

    Photo: Eric Falconer

Avalanche Discussion

 A weak ridge of high pressure will position itself over the forecast area today, providing a break in precipitation and rising temperatures. The recent snowfall is classically dense and supportable. Though 15+ inches of snow has accumulated in the last 48 hours, ski penetration is only a few inches. On the bright side, this dense snow will likely slow today's onset of warming instability, and also provide less snow available for wind transport. Snow returns to the forecast area tomorrow.

Yesterday's observations:

Gray Butte. Forecasters found new snow depths ranging from 35 to 55 cm, comprised of dense, 4 finger to 1 finger hard snow. No layers of concern were identified. Upon pit tests, small failures occurred within the new snow with moderate force, but did not propagate in an extended column. Ski turns initiated abundant roller balls on westerly aspects.

McBride to Horse Camp. A skier traveled from McBride to Horse Camp, finding heavy, dense new snow, that was consistent in depth and quality from bottom to top. The start of McBride is dry, and remains dry below 5,500 feet. Snow depth improves quickly above 5,800 feet. Very little wind effect was identified below and near treeline. Light wind effect could be seen above treeline. In the late afternoon, snow changed from heavy powder to mashed potatoes. 

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