Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
View on map

Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
Open full map
Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

An AVALANCHE WATCH is in effect.  Expect conditions to change quickly later today. The avalanche danger will rise to MODERATE this afternoon and CONSIDERABLE after sunset.  Today's new snow will foster shallow instabilities breaking in the new and recent snow, especially where winds are drifting it.   Be careful around terrain traps where small avalanches could have outsized consequences, such as in gullies, above cliffs, or in terrain where you can get pushed into a tree.  Dangerous conditions will develop overnight: slabs will grow in size and extent as storm totals stack up over the next 36 hours. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Small avalanches breaking in the new and recent snow will become more common as snow totals increase later today.  Slabs will be most sensitive to human triggers in windloaded terrain or on shaded aspects.  Watch for cracking in the snow and use small test slopes to help identify the problem.  Be cautious above terrain traps where a small avalanche can push you into trees, rocks, or gullies.   Expect this problem to increase in size and likelihood overnight.  

    Shooting cracks, like this, are signs of unstable storm slabs.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    Hard slabs that break 2 to 6 feet deep on weak layers near the ground remain a low likelihood concern.  The problem has become increasingly stubborn and isolated, and it has been several weeks since we have observed a persistent slab avalanche.  There is lingering uncertainty that skiers or riders can trigger a large avalanche from the margins of the slab where it thins out,  especially at higher elevations on northerly and easterly aspects.   Cornice falls can also trigger large avalanches.  You can reduce your risk by traveling where the snowpack is deeper and more uniform.  Regroup in safe zones that are clear of unusually wide and long-running avalanches.  

    An example of a thick, hard persistent slab that released naturally in mid-February.

Avalanche Discussion

The well-advertised storm kicks off this afternoon and intensifies overnight. Don't worry, if you missed the memo and forgot to load up on toilet paper, there should be plenty of soft snow by tomorrow that gets the job done.  Storm totals before sunset are expected to be on the modest end: 2" to 5".  For daylight hours today, that means the danger will bump up to MODERATE as the new snow adds a bit more volume and stress to the soft slabs that have been developing on the snow surface this week (Example A, Example B).  On northerly and easterly aspects, there are a number of concerning facet layers or thin crusts in the upper snowpack, generally a few inches below this morning's snow surface.  On these aspects, developing slabs will be more reactive.  On slopes where winds are drifting the new snow, fresh slabs will be thicker and will also be easier to trigger.  In both cases, avalanches will remain relatively small in size through daylight hours if the timing of snowfall stays on track.  Pay attention to new snowfall amounts and expect changing conditions later today as snowfall rates intensify around sunset.  By tomorrow, slabs will be larger, more dangerous, and more widespread.   The danger will be flirting between CONSIDERABLE or HIGH tomorrow, depending on how the storm evolves.  Read our weather forecast tab for more details.  

Today's anticipated snowfall amounts do not look alarming for our persistent slab structure. That could change by tomorrow.  Persistent slabs breaking on weak layers near the ground have been dormant for several weeks, and triggering one of these avalanches remains unlikely today.  Poor structures still exist, particularly on higher elevation terrain that faces north or east, where the snowpack has remained dry and winter-like following last week's warmup.   As this loading event continues into Sunday and early next week, our concerns for depth hoar and faceted layers near the ground to become more active will start to increase. This is particularly true for the Southeast Mountains, which have larger, weaker basal layers that continue to show propagating test results.    

Regions covered