Bollettino valanghe

Gunnison

Crested Butte Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Soaring temperatures lead to a shorter period of stable conditions on Sunday.  The avalanche danger rises throughout the morning as surface crusts break down and by the afternoon the danger could rise to CONSIDERABLE due to increasing avalanche size.  Start and finish your day early or move to less consequential terrain once the snow surface starts to rollerball, pinwheel, or thaws to more than ankle-deep wet snow.  Concerns for larger and harder-to-predict wet slabs and cornice falls continue on Sunday. Old dry slabs have become increasingly rare but remain an isolated threat on high, northerly aspects, especially on rocky or shallow slopes.  

Problemi valanghivi

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–2.5

    There's a small chance for natural or triggered wet slab activity today.  The above-normal temperatures are causing meltwater to flow deeper into the snowpack towards old weak layers.  Meltwater can cause weak layers to fail, resulting in surprisingly large wet avalanches.  Although predicting the timing and location of wet slabs is difficult, you can reduce your risk by traveling early in the day while snow surfaces are still frozen or just starting to soften.  Move to colder aspects or lower angle slopes if you are sinking more than a few inches into a wet snowpack.   High-elevation, northerly aspects do not have enough meltwater for this problem to develop yet, and low-elevation southerly aspects have already seen water drain through the snowpack, reducing the threat.  

  • Loose Wet

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

    Watch for shallow sluffs in the upper snowpack as it gets wet from solar radiation and warming temperatures.  Instabilities will be easy to recognize: look for rollerballs, pinwheels, or sluffing from very steep slopes.  Use sluff management techniques or move to lower slope angles to manage the problem if it develops.  Even though most wet sluffs today are expected to be relatively small, they can pack enough punch to carry you down a gulley, over a cliff, or into trees. In isolated areas, a wet slide might gather enough volume to be large in size.  You can avoid the issue by moving to colder aspects where the snow surface is still frozen or just starting to thaw.  

    One of the larger wet loose avalanches observed this week.  Note how the longer and steeper the terrain is, the more snow it entrains.  

  • Persistent Slabs

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

    High-consequence persistent slab avalanches have become isolated and difficult to trigger.  The last persistent slab triggered in our forecast area was on April 3rd.  The most problematic terrain is on high elevation, northerly aspects in areas with relatively shallow snowpacks (<175 cm).  Old facet layers are weaker and easier to impact in steep rocky slopes with variable snow depths.   This video highlights this type of terrain. 

    Persistent slab avalanche crowns spanning steep, rocky terrain on a north facing, alpine slope. This avalanche ran sometime during the late March storm cycle and wind-loading event.  

Avalanche Discussion

Temperatures reached 50 degrees below treeline and 40 at 12,000 feet on Saturday, and Sunday's temperatures may exceed that by a few degrees further increasing the threat of wet avalanche activity.  Clear skies overnight may help offset the slight increase in temperature as effective radiative cooling likely formed supportive crusts in open terrain.  The weather conditions will leave a window of safer riding conditions before stability deteriorates but expect that window to close around noon for sunbaked slopes. 

Wet Loose avalanches are the most common avalanche problem you'll encounter today.  In recent days, most loose avalanches have remained small in size but a chance remains for some loose avalanches to grow to a large size and become more dangerous.  Once surface crusts become unsupportive to boots due to warming, the threat of large loose avalanches increases.  The loss of surface crust support is a good metric for the less likely but hard-to-predict and dangerous Wet Slab avalanche activity.  Take a look at Zach's video from two days ago for a visual description of a wet snowpack.  The simple solution is to start early and finish early while keeping a close eye on surface crust deterioration through the first half of the day and exist steep terrain once you encounter a wet, unsupportive snowpack.

Lastly, you can find drier snow on high-elevation northerly slopes but a small chance remains for you to trigger a Persistent Slab.  Stay cautious of those unusually shallow and rocky slopes on high northerlies where early-season facets are weaker and easier to impact, and don't dilly-dally below cornices.

Cooler temperatures and increasing cloud cover on Monday likely reduces the threat of wet avalanche problems as an incoming storm system brings fresh snowfall late Monday through Tuesday.

 

 

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