Boletín de aludes

Whitefish Range

Flathead Avalanche Center
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Peligro de aludes

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

Lo esencial

You may be able to trigger slabs of wind-drifted snow on various slopes. These could be found in unusual locations due to shifting winds. Cracking in the surface snow directs you to lower-angle or sheltered terrain where the snow quality is better.  

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    1.5–2.5

    Recent snowfall and wind-blown snow rests on weak snow formed during the January drought. In many locations, the surface snow remains soft and fluffy. However, other slopes harbor a stiff slab that rests on surface hoar, facets, and facet + crust combination. These weak layers are widespread and found in many aspects at all elevations.

    As the surface consolidates into a slab, this problem will become more widespread and dangerous. Additional snowfall, wind, warming, and sun stiffen the surface into a cohesive slab. Cracking in the snow surface or collapsing (whumpfing) are clues that you have found a sensitive slab. Due to the underlying weak layers, slabs can propagate wider than expected and be triggered from flat terrain above, below, or to the sides of steep slopes. 

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2.5

    This week, shifting winds formed slabs of wind-blown snow on various aspects. Strong winds from the north and east drifted recent snow onto atypical aspects early Friday (Image). Blustery westerly winds on Tuesday and Wednesday transported surface snow, while Monday's winds were strong from the north and east. 

    In many locations, slabs rest on weak snow formed during the January dry spell or recent low-density snowfall. The combination of an underlying weak layer and cold conditions is slowing the strengthening of these features. As you gain elevation, slabs will generally be thicker and more widespread; however, atypical winds may have left slabs in unusual locations at lower elevations. 

    Dunes, pillow-like features, and etched surface snow (Image) indicate the wind has been at work. Cracking or collapsing (whumphing) are signs of a sensitive slab directing you toward lower-angle slopes.

     

    (2/5/2025)

    Intentionally triggered small (D1) soft slab on a wind-loaded NE slope at 6900'

    Photo: Flathead Avalanche Center

Avalanche Discussion

The wind has been responsible for most avalanche activity in the first week of February. Moderate to strong winds from various directions easily transported the low-density snow that fell over the past week. With forecasted light snowfall and continued shifting winds, we anticipate slabs of wind-drifted snow will remain the primary avalanche concern through the middle of the upcoming work week.   

February's below-average temperatures will continue for a few more days as another Arctic intrusion enters our area overnight on Sunday. This cold air limits settlement in the recent snowfall from the 1/31-2/1 storm and this past week's weather. Eventually, increasing temperatures, prolonged intense sun, or warmer precipitation will return, helping to consolidate the surface snow into a slab. When that occurs, the avalanche hazard will become more widespread as buried weak snow from the January dry spell is found on many slopes at all elevations.

Yesterday (Friday), we listed Persistent Slab as an avalanche problem in the Whitefish Range. Due to the generally soft surface conditions, a rider is unlikely to trigger a slide on a buried weak layer; however, as the surface snow consolidates into a slab, the likelihood of triggering increases. Observations suggest that buried surface hoar is more widespread in this range than in the other zones.

The recent low-density snow and cold conditions have kept a cohesionless surface in many sheltered locations. On very steep slopes, riders could trigger loose snow sluffs. These can be problematic above cliff bands, in long-running gullies, or terrain traps where the snow piles up deep. Mostly cloudy conditions are expected today, but natural loose snow slides may develop on steep slopes facing the sun if the intense February sun makes a prolonged appearance.

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