Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Heavy snowfall and extreme winds will create large natural avalanches in upper elevation terrain. Expect dynamic weather and very dangerous avalanche conditions to develop by Sunday afternoon. Avoid travel in or below avalanche terrain during periods of heavy loading from new snow and wind. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3

    A few inches of wet snow will accumulate overnight before temperatures cool and heavy snowfall begins Sunday morning. Expect 12-18+ inches of new snow above 4000ft by Sunday night. Strong to extreme southwesterly winds will blow through the forecast period. Conditions will be very dynamic with the potential for a natural avalanche cycle by Sunday afternoon. You may encounter lower avalanche hazard in the morning hours but be prepared for rapid change as precipitation rates look to increase to 1 inch of snow per hour through the evening. Watch for obvious signs of unstable snow like recent avalanches, shooting cracks, and collapses. Cornices are already overbuilt and will continue to grow in the next 24 hours. They could easily fail in conditions like these acting as huge triggers on slopes below. Avoid travel on or below open slopes greater than 35 degrees. Choose low-angled, sheltered terrain away from overhead hazard while the storm runs its course.

    (12/31/2020) Example photo of a large natural avalanche in wind drifted snow below a corniced ridgeline.

  • Loose Wet

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

    Snow levels will hover near 4000-4500ft overnight before dropping to 1000ft Sunday evening. The potential for loose wet avalanches will exist in the morning hours and will likely diminish by afternoon. Before temperatures cool, anticipate loose wet avalanches within new snow or anywhere you encounter heavy rain. Steer around slopes 35 degrees and steeper with evidence of wet snow like rollerballs, pinwheels, or sticky surface snow.

    (3/26/2021) Rollerballs and small wet loose avalanches at 6400ft on the east aspect of Bearpaw Mountain. These ran during warming and sunshine on the afternoon of 3/25.

Avalanche Discussion

Expect rising avalanche danger as a potent storm builds fresh slabs and cornices over the next 24 hours. Blustery whiteout conditions will make travel difficult. New snow will fall on a variety of old snow surfaces including moist snow, breakable crusts, and dry settled powder. Extreme winds from the south and west will transport snow onto leeward slopes. Natural avalanches could run in many alpine start zones by Sunday night and grow large. Avalanche activity may only involve new and wind-loaded snow, but it is not out of the question to see avalanches break several feet thick within recent storm snow received March 18-24. 

Observers on Saturday reported loose wet avalanches to size D1.5 on many sun-exposed slopes during the heat of the day. A cornice also broke off Table Mountain triggering a D2 wind slab that sent debris down to Iceberg Lake. The crown ranged from 1-4ft thick and occurred on a NW aspect at 5200ft. This avalanche likely ran Friday. Several other natural and triggered avalanches occurred during the recent storms with crowns ranging 1-3ft thick. 

In addition to fresh slabs and loose wet avalanches, keep glide avalanches in mind. We could see more of these avalanches with heavy rain at low elevations on Sunday, and/or with warming and sunshine during the upcoming week as high pressure arrives. Watch out for these crevasse-like cracks in the snowpack, and avoid travel on or below steep slopes where they exist.  

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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