Boletín de aludes

Salt Lake

Utah Avalanche Center
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Peligro de aludes

  • Alta montaña
  • Límite del bosque
  • Bajo el límite del bosque
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The avalanche danger is CONSIDERABLE on all mid and upper-elevation steep slopes for slab avalanches. Here, avalanches can fail within the new snow or at the old/new snow interface. On northerly facing terrain, these avalanches could step down into buried weak layers of faceted snow, making them more dangerous. Human-triggered avalanches 1 to 3 feet deep are likely today. Careful snowpack evaluation, cautious route-finding, and conservative decision-making will be essential. Days like this make me nervous. Elevated danger, lots of new snow, buried facets (weak layer), partly cloudy skies, and stoke—it sounds like an avalanche accident waiting to happen.

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2

    With 9 to 19 inches of new snow, it's hard to know precisely how touchy the new snow will be this morning. Today we could see avalanches fail within the new snow or at the new/old snow interface. We could also see avalanches step down into our January buried facets making these deeper and more dangerous. In any case, these avalanches will be large enough to bury a person today. Use test slopes, slope cuts, and shovel tilt tests to see how this new snow is behaving.

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2

    Northern Utah has seen strong wind for over a week now, and yesterday's pre-frontal southwest wind was no exception. The new snow will have buried old hard drifts and formed new soft slabs of wind-blown snow across the mid and upper elevations. Any fresh wind drift may fail at the existing snow surface or on slopes facing northwest through the southeast; they could step down 1-3 feet deep into buried weak layers of faceted snow.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    3

    There are two buried persistent weak layers (PWL) in the snowpack:

    1. The upper layer buried down 12-36 inches formed during cold, clear weather in late January and has been buried by recent storms and wind-drifted snow. Today, this layer could become active with the additional water weight we have added in the past 24 hours. Avalanches 1 to 3 feet deep are possible.

    2. The lower layer, near the ground, formed in December and has caused large avalanches, including two fatalities during the Holiday Avalanche Cycle. This layer is most problematic in steep rocky terrain or on repeater slopes that previously avalanched this winter. Avalanches up to 2 to 4+ feet deep are possible.

    Today is not the day to be testing steep avalanche terrain. I would avoid being on, adjacent to, or below slopes steeper than 30 degrees. Avalanches can be triggered remotely (from a distance).

Recent Activity

Yesterday, backcountry observers noted dry-loose avalanches consisting of graupel snow during the high precipitation intensity. One avalanche was reported from the Mary Chutes in Upper Big Cottonwood. This avalanche was new snow graupel pooling that failed at the new/old snow interface. The avalanche was 8 inches deep, 40 feet wide, and ran about 100 vertically (photo below).

Snow and Weather

Wow! What a storm! Yesterday's storm started out of the south with strong winds and plenty of graupel snow (round pellets). Around 2:00 PM, the cold front pushed through, the winds diminished, and temperatures dropped. 24-hour storm totals range from 6 to 19 inches of new snow containing 0.65 to 2.84 inches of water. Upper Little and Big Cottonwood Canyons received the lion's share, followed by PC Ridge with 9 inches of snow and 1.50 inches of water. Lower elevations rang in with 6 inches of snow.

This morning will look like a scene from a Warren Miller Film: light winds, partly sunny skies, cold temperatures, and plenty of new snow. This afternoon, clouds will increase, and we will see the winds switch back to the west-southwest and blow 10-15 mph with gusts into the 20s as a small storm moves in late this afternoon. This storm could bring a couple more inches of snow, and temperatures will climb into the mid-20s.

Riding conditions: 5 star

Additional Info

This is a video discussion of the current snowpack. It was taken yesterday afternoon, and I did not know the upper canyons would receive 2.84 inches of water. This is a huge load on our snowpack. I wouldn't be surprised to see avalanches break deeper in the snowpack over the next few days. Especially in areas that received the most snow.

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This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.

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