Bollettino valanghe

Northwest Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Wed
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3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Storm totals exceed a foot in some areas and drifting from westerly winds will keep the pressure on weak layers.  Dangerous natural avalanches are possible today on leeward terrain and human-triggered avalanches are a menacing threat in sheltered areas where you find old, weak snow near the ground.  You can reduce your risk of avalanche involvement by choosing low-angled terrain free of overhead hazards anywhere you find old, weak snow at the ground or by choosing south/southwesterly slopes that lack early season weak layers.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Storms this month built large persistent slabs that are sensitive to human triggers and could release naturally today.  There's a widespread weak layer of facets and faceted crusts buried by 2 to 3-foot slabs on west to north to southeast aspects. Concerns also exist on some alpine south and southwest-facing terrain features.  Slabs are largest in leeward terrain at higher elevations.   Persistent slabs are notorious for erratic feedback and unusual behavior, such as remote triggering and wide failures.   To avoid the problem, choose routes that keep you off and out from under terrain steeper than about 30 degrees that hold old, weak snow near the ground.    

    A recent persistent slab that wrapped from shady to sunny aspects and broke on weak layers near the ground. This a good example of the potential size and widely propagating behavior of our current persistent slab problem. 

  • Wind Slabs

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

    New snow and westerly winds yesterday and today will form fresh drifts on leeward terrain features.  Watch for blowing snow to clue you into developing instabilities as well as cracking in the storm snow.  Small wind slabs have the potential to step down and trigger a larger persistent slab avalanche where the problems overlap.  Areas in the Northwest Mountains, near Irwin and the crest of the Ruby Range, accumulated a foot of new snow as of 6 am so these geographic areas could produce larger Wind Slabs.     

    Look for blowing snow like this to warn you of fresh wind slab formation.

Avalanche Discussion

Weak layers near the ground have produced scary avalanche activity for nearly 2 weeks (this past weekend's natural and remotely-triggered avalanches are pictured in the gallery below).  Each time mother nature drops snow and blows hard enough to transport snow, avalanches come crashing down.  The current storm may produce similar results today but over a smaller geographic area and here is why.  Weather stations are reporting widely disparate storm totals.  CBMR, Elkton, Schofield Pass, and Upper Taylor show only 1-4 inches BUT Irwin Guides Study Plot hit 12 inches at 6 am.  Snowfall will continue through the day as will the westerly winds strong enough to blow snow to leeward features.

So let's start with the most dangerous geographic areas; Irwin and the southern Ruby Range certainly have enough new snow to cause real concern for natural avalanche activity on leeward terrain features.  Areas in the Anthracite Range and the Beckwith's often follow a similar snowfall pattern as Irwin and likely received similar storm totals.  Finding more than 8 inches of storm snow indicates the increased risk of natural avalanches and a bump in sensitivity for human-triggered avalanches.  In these areas, you need to make conservative terrain choices on slopes facing west through north through southeast as this is where you are most likely to encounter a deeply failing avalanche.

The rest of the CBAC forecast area received far smaller storm totals and is less likely to produce dangerous natural avalanche activity.  Unfortunately, the snowpack structure remains poor for terrain highlighted in the distribution rose for the Persistent Slab problem.  The chance of human-triggered avalanches continues to hover near 'Likely'.  Conservative terrain selection remains paramount regardless of where you travel geographically.

Regioni coperte