Bollettino valanghe

Northwest Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

Wed
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

It's time to step back and change your mindset towards conservative terrain selection.  The danger will rise from CONSIDERABLE today to HIGH sometime around sunset.  You can easily trigger slab avalanches at all elevations today, and many will fail naturally.  Avalanches will be largest and most sensitive where winds are loading snow AND in sheltered northerly facing terrain where there is a sandbox full of facets below the new snow.    Travel on or below avalanche terrain is not recommended, especially below wind-loaded or north-facing terrain.      

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1.5–2.5

    In the Northwest Mountains, up to 18 inches of new snow with strong winds has fallen on widespread facet layers and crusts. Soft slab avalanches breaking in the new and wind drifted snow will be easy to trigger and will be failing naturally today.  Slabs will break thicker and wider on high elevation, leeward terrain.  In sheltered northerly terrain, even thin slabs can grow to surprisingly large sizes because they will entrain the weak, faceted snow below.  Ride on slope angles less than 35 degrees to avoid the problem. Use extra caution on the northern half of the compass where slabs could exhibit more unusual behavior, such as remote triggering.  

    This is a photo from the archives, but it's a good example of the conditions we expect to see out there today.  

Avalanche Discussion

Let the avalanche party begin! So far, the storm has delivered 4" to 8" in the Southeast Mountains and 8" to 18" in the Northwest Mountains.  Winds were cranking all night out of the southwest, easily transporting the new snow into thicker slabs on leeward terrain.  We'll see snowfall continuing today and then really ramping up tonight and tomorrow.  Details in our weather discussion.

The new snow is falling on an exceptionally weak facet layer that has developed over the past 6 weeks of dry weather.  On the northern half of the compass, this layer will be failing naturally through the day, especially in windloaded terrain.  The danger will be rising towards HIGH as destructive sizes increase over the next 36 hours.  The Northwest Mountains, particularly the Ruby Range and Paradise Divide areas, will have larger slabs and are tracking faster towards reaching HIGH danger than the rest of the forecast area.  The favored areas should reach HIGH sometime around sunset if forecasts verify, so we've bumped the danger accordingly to account for some uncertainty with the timing.  The Southeast Mountains are tracking behind; they will have smaller and more manageable storm instabilities through the day, especially if you can work the southerly aspects that are out of the wind.  Avalanches will entrain quite a bit more snow on northerly aspects because of how much loose faceted snow is sitting in the tracks.  Slabs on wind-loaded slopes will also be growing in size quickly through the day.   

The danger will continue to increase tomorrow as slabs continue to grow larger in size. Expect HIGH danger at all elevations across the entire forecast area by Wednesday morning.   

 

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