Bollettino valanghe

Banner Summit

Sawtooth Avalanche Center
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Pericolo valanghe

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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You could trigger wet or dry avalanches today. Yesterday's wind blew the new snow into sensitive wind drifts at upper elevations. Watch for the new snow becoming moist and sliding on slick crusts. Near valley bottoms, expect to find rotten, rain-soaked snow.

Problemi valanghivi

  • Wind Slabs

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

    Yesterday's spring storm brought 4-8" of new snow accompanied by moderate to strong S to SW winds. On Gladiator Peak in the Galena Summit & Eastern Mtns zone, my partner and I found winter-like conditions up high. The wind was actively transporting the new snow into sensitive drifts along exposed ridgelines (photo above/right, video). With greater snow accumulations in the Banner Summit area, I would expect these wind slabs could be large enough to bury a person. 

    It's been a while since we've been concerned with dry snow avalanche problems. Even if your winter avalanche eyeballs are a bit rusty, these fresh wind slabs should be easy to identify today. If you find hard crusts blown free of snow, ask yourself where that snow went. Look for pillowed or drifted areas on the lee sides of ridges, gullies, and other terrain features. Especially on northerly-facing slopes, these wind slabs will have formed on weak snow surfaces and are likely to be reactive to your weight.

    (3/19/2021) On Friday, moderate to strong winds were transporting the new snow and forming wind slabs at upper elevations. While generally small, these wind slabs could be more dangerous in the Sawtooths and Banner Summit area where more new snow fell.

  • Loose Wet

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

    Funky spring storms lead to funky wet problems. Today you'll find winter conditions at upper elevations, a soggy, rain-soaked snowpack down low, and something in between at middle elevations. Be on the lookout for two different types of wet snow problems today:

    • Below about 7000', expect to find a wet, soggy snowpack. Low elevations received mostly rain during yesterday's storm, and near or above freezing temperatures overnight will have done little to help the problem. It'll be a good idea to avoid being on or beneath steep, lower elevation terrain today. Treat any slope without a hard, frozen surface crust as suspect.
    • As temperatures warm at middle elevations, the new snow may become moist and tend to slide off the old crusts below. I found this starting to happen yesterday as temps increased. Wet slides involving the new snow will become even more likely if the sun pokes out today. You can test small, steep slopes by pushing on the surface snow to see if it wants to peel off the crust and run downhill.

Avalanche Discussion

More than a week of predictable spring-time avalanche problems led many of us to take a more relaxed approach in the backcountry. I'm not necessarily saying we were getting sloppy, just enjoying the stable conditions after a winter of dangerous weak layers. Well, yesterday's wet spring storm has changed the equation and it's time to get our heads back in the game!

While triggering a large avalanche isn't particularly likely today, there are a lot of different places you could trigger smaller slides—and these will could come in any number of forms. Traveling in the backcountry today will necessitate keeping your head on a swivel from the valley floor to the mountain tops. Here's what you might find today:

  • Upper Elevations/Alpine: Winter conditions have returned! You're likely to find 4-8" of dry new snow from yesterday's storm. Fresh wind slabs formed in exposed terrain—expect these to be reactive to your weight. Cold temperatures today should prevent wet issues unless the sun comes out.
  • Middle Elevations: Expect to find conditions transitioning from winter-like up high to a wet, soggy mess down low. The new snow will have fallen on mostly frozen crusts. With warming temperatures today, and especially if the sun pokes out, expect this newer snow to become moist and slide on the "greasy" crusts below.
  • Lower Elevations/Valley Floor: Below about 7000', yesterday's storm produced mostly rain or slushy snow—which fell on an already wet snowpack. Given last night's near or above freezing temperatures, expect to find a soggy, saturated, and rotten snowpack at lower elevations. Plan to avoid being on or under steep terrain near the valley bottom.

One thing is for sure—conditions will be different than the last week, necessitating an assessment mindset. 

Speaking of last week, be sure to catch up on what happened in our latest weekend update!

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