Bollettino valanghe

Swan Range

Flathead 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

Recent snowfall has improved the riding but increased the avalanche danger. Fresh slabs will increase in thickness and size as you gain elevation. You could trigger slides from gentler terrain below, above, and to the sides of steep slopes. 

Problemi valanghivi

  • Storm Slabs

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

    Since Thursday morning, the Swan Range recorded an inch of water which may have deposited 8-10 inches of new snow. This fresh snow rests on weak faceted snow or surface hoar in many locations, adding to its instability. On slopes sheltered from the wind, soft slabs may have developed. Slabs will be thicker and larger in windier locations below ridgelines, saddles, or cross-loaded gullies. Due to the underlying weak layer, slabs may be triggered remotely or from a distance. 

    You have found a slab if you suddenly notice your skis, boards, or machine not sinking as deeply into the new snow. Utilize hand pits to see how well the fresh snow is bonding to the old surface. Cracking in the snow surface indicates an unstable slab and directs you to seek out lower-angle terrain.

      

    (2/24/2023)

    A soft slab avalanche in a sheltered location on a convexity. This is also known as a storm slab.

    Photo: md

  • Loose Dry

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

    You can trigger sluffs on steep slopes with recent, dry snow. These may be large enough to bury you in areas with more than 8 inches of new snow. Confined chutes and sustained steep slopes above terrain traps present the greatest danger.

    (1/13/2023)

    A thin, Dry Loose slide triggered by a skier in the top few inches of snow on an east aspect at 6400'.

    Photo: Mark Dundas

Avalanche Discussion

Snowfall and precipitation totals for the system, which impacted our area Thursday into Friday, were disappointing. Noisy Basin, in the Swan Range, took home the lion's share with a respectable 1 inch of water; however, most other locations recorded just several inches of snow and around 1/3 inch of water. These totals should increase slightly before this system moves out of the area sometime mid-morning. Fortunately, unsettled weather continues through the weekend with widespread light snow and seasonably cool temperatures.

The new snow fell on weak faceted snow or surface hoar in many locations. If slabs develop on the underlying weak layer,  they might be more reactive to the weight of a rider than anticipated. There is the possibility of triggering slides from above, below, or to the sides of a steep slope. Slides may break wider and higher above you than expected. Today's triggered slabs may act more like a persistent slab than a storm or wind slab.

Today, we are listing storm slab, wind slab, and loose dry across the three zones, which are all new snow avalanche problems. As snow piles up through the weekend, the avalanche danger may increase as a thicker and stronger slab develops on top of weak snow. We expect to transition to a persistent slab problem in the next day or two. 

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