Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
View on map

Avalanche danger

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Out of date — this forecast expired 2 years ago.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

Highlights

In the Northwest Mountains, you can find generally safe riding in wind-sheltered terrain.   At higher elevations, watch for small drifts forming in the new snow and remain cautious of wind affected slopes with thin or variable snow depths.  That's where there are lingering concerns for triggering a dangerously large avalanche like this persistent slab on Baldy last Friday.  

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Up to 6" of new snow overnight and westerly winds at high elevations formed shallow soft slabs in a few leeward terrain features.  Fresh wind slabs will be sensitive to triggers: stay alert and ride defensively anywhere that you can't afford to get knocked off your feet such as above cliffs or in gullies.  You can avoid the problem by traveling in sheltered areas where the snow is fluffy and unaffected by winds.  Fresh drifts will look and feel thicker than wind sheltered snow.  

  • Persistent Slabs

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

    In the Northwest Mountains, high consequence slabs breaking on older weak layers have become isolated and difficult to trigger.  Persistent slabs are most likely to be triggered from a shallow, wind-affected slope or from random cornice falls. Persistent slab avalanches can be remotely triggered from low-angle terrain and break deeper and wider than you might expect.  The most problematic structures are on shallower slopes on the north half of the compass and a few high, southerly aspects.  Mid to low-elevation, southerly aspects have the most trustworthy snowpack.  Slope angles consistently less than 30 degrees are a reliable way to avoid the problem when in doubt.  

    The crown of a very large persistent slab remotely triggered by snowmobiles on March 8.  This slope is west facing and eroded by seasonal winds, making for a shallower and more problematic snowpack than other slopes. 

Avalanche Discussion

3" to 6" of low-density snow overnight provides a nice surface refresh that won't significantly change conditions:  Watch for minor sluffing in favored areas and thin wind slabs in alpine terrain where the new snow is getting blown around.  

We've lowered the likelihood of triggering a persistent slab to "unlikely" in the Northwest Mountains and "possible" in the Southeast Mountains.  The chances of triggering a persistent slab are decreasing after nearly a week of mild, dry weather.  This has given weak layers a chance to adjust to the last significant loading event. Furthermore, surface crusts formed on sunnier aspects, which adds some strength to the snowpack.  The thicker the crust, the more of a stabilizing effect it has.  We've trimmed back the distribution of the persistent slab rose to reflect the aspects and elevations that saw the most significant upper snowpack strengthening.  

The pattern of triggered and natural persistent slab avalanches over the past 2 weeks clearly points to areas with shallower snowpacks being the most problematic.  Most of the avalanche activity has been in the shallower part of our forecast area (the Southeast Mountains), and the few persistent slabs in the deeper zone occurred on windward slopes or on slopes that have repeatedly avalanched this season keeping the snowdepth unusually shallow.  It's an appropriate time to step out if you are choosing slopes with consistently deep snowpacks (>200cm), or choosing southerly aspects with strong crusts near the snow surface.  

CBAC Event:  Don't forget the 50th Al Johnson Race is this Saturday, March 17th.  Registration and information can be found at cbavalanchecenter.org.  All proceeds to benefit the CBAC.

Regions covered