Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

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

Dangerous avalanche conditions may develop during the day with overlapping dry and wet snow problems. Shallow avalanches may step down to deeper weaker layers, creating much larger and more powerful avalanches.  Continue to travel conservatively and be mindful of overhead hazard. 

Avalanche problems

  • Persistent Slabs

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

    We are exiting a multi-day storm cycle and entering a multi-day warm-up.  From one test of the snowpack to the next. 

    Put a larger buffer of terrain between your group and large start zones or complex avalanche paths above 6,500ft. Use extra caution in areas where you find less than 5 feet of snow on the ground above 6,000ft. Choose smaller, supported slopes and stay well out from under larger features. Signs of instability can be inconsistent, creating a tricky problem that is essentially 'unmanageable.' You might not receive signs of instability before the whole slope fails.  Facets buried throughout February exist over a crust in the top 2-4 feet of the snowpack. There's copious evidence of these layers being the culprits of numerous very large natural avalanches and close calls in the zone. 

    (3/5/2024)

    A very large avalanche was remotely triggered by skiers on 3/2 on Kangaroo Ridge. The crown was ~70-100cm deep, and it ran on a layer of facets (1.0mm) buried in mid-February, just above the 1/31 crust.

    Kangaroo Ridge, Pk 8183, WNW, 7,600ft

    Photo: John Stimberis

  • Wind Slabs

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

    Brisk northerly winds will likely redistribute recent snowfall near and below ridgelines and may cross-load slopes or build wind slabs in atypical locations.  While most wind slabs will be small, every avalanche problem needs to be wrapped back to the potential for triggering a larger and more deadly persistent slab avalanche on older weaker layers.  Cracking in firm, or wind-textured snow are red-flags to avoid steep lee slopes.  Cornices from the prevailing wind direction may start to erode depending on the strength and duration of alpine winds. 

     

    (3/13/2024)

    Small pockets of reactive wind slab on test slopes. 

    Photo: Joe Dellaporta

  • Loose Wet

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

    As the day warms up, look for the tell-tale signs on increasing wet loose instability like wet surface snow, pinwheels/rollerballs and natural wet loose avalanches.  It's the first big warm-up under a strong mid-March sun and we received roughly 1 to 2' of snow above 5000' since 3/9.  Wet loose avalanches can become large at mid and higher elevations where they entrain the recent storm snow, especially in tight features like chutes and gullies.  Move to shadier aspects and lower angle terrain without exposure to overhead hazard like cornices and avoid traveling on or below cliffy slopes in the sun.  Wet loose avalanches are likely to be smaller at lower elevations, but can still cause trouble near terrain traps.  Breezy conditions are likely to limit the likelihood and size of wet loose avalanches at higher elevations.   Again, be mindful of smaller avalanches stepping down to deeper weak layers. 

    (2/22/2024)

    A large natural wet avalanche releasing from steep rocky terrain occurred on February 22nd on Big Kangaroo Peak. SW, 7,800ft

    Photo: Will Govus

Avalanche Discussion

Multiple parties noted a large natural avalanche in the Cutthroat drainage on 3/12 that ran approximately 1500'.  This may have been a smaller avalanche that released below cliffs and triggered a larger persistent slab on the slopes below.  Since our storm cycle began on 3/9, the Harts Pass Snotel has picked up about 1.8" of water, with all of that falling as snow at mid and upper elevations.  Professionals reported several small natural and human triggered wind slabs on Tuesday and Wednesday. 

On March 5th, forecasters visited the site of a remotely triggered (D3) avalanche on Kangaroo Ridge. They found that the avalanche was ~2.5-3 feet deep and ran on a layer of facets buried in mid-February, just above the Jan 31st crust. Tests still produced sudden or propagating results indicating that backcountry travelers could trigger similar avalanches, especially in areas of relatively shallow snowpack. There have been multiple reports of close calls, natural avalanches, and snowpack observations in the Highway 20 corridor that point to the deep, persistent slab problem. Widespread, very large natural avalanches occurred between February 28th and March 3rd. Natural avalanche tailed off in early March and snowpack tests have become more variable, some showing relatively stable results. In the East Central and Stevens Pass zones, there have been multiple triggered avalanches and involvements this week on a similar snowpack structure.

Snowpack information is limited outside of the Highway 20 corridor and Harts Pass. Let us know what you find if you get out into the backcountry!

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