Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

The avalanche danger will begin to rise today, as northerly winds start drifting snow onto the lee sides of terrain features. The size and sensitivity of the developing wind slabs will depend on the snow available for transport in the area you are traveling. Snow totals since last Friday vary widely accross the northwest mountain forecast area, from a few inches to over a foot. In wind-sheltered areas, loose snow avalanches, or sluffs, continue to require management on sustained steep slopes. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2

    Northerly winds are forecasted to increase and build fresh slabs on the lee sides of ridgelines and cross-loaded terrain features. In many areas, these slabs are forming over a notably weak interface after a prolonged dry spell before the last storm. Keep an eye on wind-loading in the area you are traveling. If you observe active wind-loading and building slabs, consider routes that will avoid those specific terrain features. Winds blowing through open valleys may also build wind slabs in unusual locations. 

    This slab avalanche was human-triggered on Saturday, and though it didn't run far, it propagated widely on the old weak snowpack. 

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    The snow that accumulated last weekend is adding volume to the loose snow avalanche problem that we have been dealing with for the last week. In many areas, these sluffs are small and relatively easy to manage. In some areas, these sluffs can entrain enough volume to become large and difficult to manage. This avalanche problem will be the largest on northerly facing terrain, primarily below 11,500ft where the sluffs can entrain the entire weak snowpack. You can manage the problem by riding off the fall line or pulling out of the way to let your sluffs go past you. You can avoid the problem by riding on lower slope angles less than about 35 degrees. 

    Dry Loose avalanches start from a point, before growing in size. Don't be that tree and move to the side. In sustained steep terrain, this problem may grow large and become difficult to manage. 

    Photo: Zach Guy

Avalanche Discussion

Observers continue to report back about the notably weak snowpack, and weak interface that last weekend's snow accumulated on. We will cross a line into more dangerous conditions once slabs form over those weak layers. So far, the cold temperatures and lower totals have primarily just added volume for loose snow avalanches. Increasing northerly winds will begin building slabs in specific terrain features. Those slabs are expected to become reactive once they form over the weak interface. The most snow available for transport is in the near treeline elevation band, while in the alpine much of the low-density snow has previously been blown around. It will be interesting to see just how this avalanche problem shakes out over the next 24 hours. In areas with active wind loading, natural avalanches will become possible.

The avalanche danger trend will depend on how much wind loading occurs over the next 24 hours. Wind slabs will remain reactive where they have formed over persistent weak layers. The avalanche danger in the SE Mountain forecast area was held at MODERATE given less snow available for transport after only a few inches accumulated this past weekend. 

Storm totals since Friday vary widely, and with widely varying storm totals we can have a widely varying avalanche danger across the forecast area. In the northwest mountains, those storm totals vary from a few inches to over a foot in some areas. Schofield Pass and Irwin Snotels are measuring .5 to .6 SWE gains. In the SE Mountains, the new snow accumulations are meager with totals in the 1 to 4-inch range and SWE gains up to .2. 

Regions covered