Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

On Monday, stormy weather will maintain dangerous avalanche conditions within the West South zone. You’ll need to manage new snow problems near the surface and be diligent about terrain selection due to old snow problems deep in the snowpack. The most straightforward plan will be to avoid all terrain over 35 degrees until this storm cycle ends.

Avalanche problems

  • Storm Slabs

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

    Continued snowfall and moderate to strong winds will result in slab development throughout the West South zone. Slabs will be larger as you ascend in elevation or in wind-loaded terrain. They could overlay weak grains or a firm crust, making them fail easily. Use small test slopes, uptrack tests, and quick hand-pits to gauge the new snow’s reactivity and bonding at the new/old interface. When in doubt, avoid slopes over 35 degrees where triggering an avalanche is more likely.

    (3/10/2024)

    A skier-triggered slab mid-slope on a northerly aspect in the Bullion Basin area.

    Photo: Andy Harrington

  • Deep Persistent Slabs

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

    We’re slowly incrementing the load over our persistent weak layers this week. The question becomes whether or not it will be enough to tip the scales and start producing avalanches. The poor snowpack structure remains in place. NWAC forecasters have performed numerous tests on these layers this week at White Pass and Crystal Mountain, and they have all failed. In areas such as Crystal, these layers are buried less than a meter deep, meaning they are within the commonly accepted depth of human-triggering. This avalanche problem won’t show you any warning signs, and tracks on a slope are not an indication of stability. Your best mitigation tool continues to be the avoidance of large open slopes where these unpredictable and deadly slides are possible. 

    (3/7/2024)

    A very large (D3) avalanche on the Conrad Glacier below Gilbert Peak as seen from White Pass [N 7500']

    Photo: Andy Harrington

Avalanche Discussion

NWAC will be closed on Tuesday, March 12th, as we gather and grieve following the death of one of our forecasters, Matt Primomo. We will not issue regular avalanche or mountain weather forecasts on Tuesday. We will return to normal operations on Wednesday, March 13th. We appreciate the community's understanding and support during this time.

Discussion:

On Sunday morning, NWAC forecasters in the Crystal Mountain area found touchy 4-inch soft slabs. The new snow was poorly bonded to the 3/9 interface on most aspects and elevations. Prior to this storm, weak surfaces such as near-surface facets and surface hoar were reported. Where they persist, avalanches could break in surprising ways. On slopes that typically receive direct sunshine, a sun-crust exists at the 3/9 interface. The new snow failed easily on this crust on Sunday.

The Early February Crust (EFC) continues to produce concerning test results. Sudden collapses, propagation, and confirmed weak grains all point toward a scary layer roughly 2-5 feet below the surface. That depth will continue to grow throughout the next few days as we incrementally load the EFC and other weak layers in the snowpack. Last time we had a significant loading event, numerous very large (D3) avalanches were reported throughout the zone.

Avalanche hazard is slowly increasing as this storm pattern intensifies. Expect it to climb throughout the day and into the early evening hours on Monday. Be sure to have a solid plan for exiting the mountains if you’re trying to take advantage of the time change and longer days. 

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