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

Up to a foot of recent snowfall and efficient winds will make for sensitive avalanche conditions on drifted terrain.  Soft slab avalanches may be possible in sheltered areas as well.  Cracking is a clear sign of a problem in wind-sheltered places.  Avoid terrain that you suspect could be drifted as loading patterns have shifted around during the storm and carefully assess the storm snow in sheltered areas for instabilities.

Avalanche problems

  • Storm Slabs

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

    Another round of snowfall yesterday evening bumped storm totals near a foot coupled with shifting wind directions.  The most concerning slopes will be drifted terrain features at upper elevations.  The new snow accumulated above crusts on the south half of the compass and small-grained facets on the north half of the compass.  Avoid terrain where you expect to find drifting; you may have trouble reading loading patterns as the wind shifted directions.  Carefully assess the recent storm snow in sheltered areas.  You can use small test slopes on wind-protected terrain to investigate for instabilities in the storm snow and how well it bonded to the old snow surface.  Cracking in the new snow is a sure sign of a slab avalanche problem.

    (3/24/2024)

    A triggered avalanche in storm snow on a drifted slope.  Additional snowfall Sunday night will create a bigger avalanche size today.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–2.5

    In the Northwest Mountains, high-consequence slabs breaking on older weak layers have become isolated and difficult to trigger. The last observed persistent slab avalanche occurred on March 8th in this forecast area. Any lingering persistent slabs would most likely be triggered from an unusually shallow or previously wind-eroded slope where the total snowpack height is below average.  Large cornice falls could act as triggers as well. Persistent slab avalanches can be remotely triggered from low-angle terrain and break deeper and wider than you might expect.  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

Snowfall continued yesterday evening and overnight increasing storm totals.  Storm totals are Schofield Pass 12", Irwin 10", Elkton 8", CBMR 7",  and Upper Taylor 12".  Snow water equivalents around 1" have been recorded in the deeper areas.  Wind directions have shifted since the beginning of the storm on Saturday night.  Winds began from the south then shifted to the west and finally to the northwest.

In the Northwest Mountains, the primary problem will be to manage the recent storm snow.  Expect to find sensitive avalanche conditions where you encounter wind-deposited snow on leeward terrain features.  Observations from Sunday pointed to a developing problem with a triggered avalanche on Mount Emmons, cracking in drifted snow on Anthracite Mesa, and multiple triggered avalanches from the Marble area (1,2,3,4).  The recent snow fell on a layer of near-surface facets on the north half of the compass, expect conditions to remain sensitive today with more snow and a persistent weak layer responsible for failure below the new snow.  Avalanche size will grow from those documented in the observations above.  There is some uncertainty of the sensitivity in sheltered terrain, but use caution if you ride in steep northerly terrain.  The storm snow appears to have bonded better where it landed on crusts on sheltered sunny slopes.

In the Southeast Mountains, there are two problems to manage.  The first is avalanches in the storm snow as mentioned above.  Secondly, the Persistent Slab problem could become more sensitive with the recent loading.  Your best bet is to simply avoid drifted terrain features highlighted by the Persistent Slab rose as triggering an avalanche that breaks deeply in the snowpack remains possible and would be very dangerous.  There is generally less snow in the Southeast Mountains, however, Upper Taylor recorded a foot of storm snow with 1 inch of water which suggests some areas along the Elk Mountain Crest may have as much snow as the Northwest Mountains.

Take a cautious approach to the mountains on drifted terrain and sheltered areas where you encounter a foot or more of new snow.  Conditions may be more sensitive than you expect on the north half of the compass.  Pay attention to warming snow if the sun makes an appearance today.  Steep sunny slopes may quickly sluff from strong solar radiation.

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