Bulletin d’avalanche

West Slopes South

Northwest Avalanche Center
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Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

A warm, sunny day in the forecast. Look for signs of instability in the terrain above and skip travel on steep slopes holding wet, manky snow.  You can still trigger a slab avalanche in wind-drifted snow in some areas. Deeper new snow at upper elevations on St. Helens and other southern locations equals higher danger from both wet and wind slab avalanches. Use extra caution in these areas

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Widespread sunny skies and mild temperatures are in the forecast for Friday, so wet loose avalanches are again on the list of problems. Wet snow surfaces and clear skies overnight should make for a frozen crust in the morning and low danger. But lots of sun and warming should break down the crust on solar aspects and open the door for wet avalanches

    Sun-exposed, upper-elevation slopes still holding cold snow might become active earlier in the day. Limit travel on or directly under steep slopes seeing direct sun or where the snow is mushy and wet. Avoid this terrain if you see signs of instability like rollerballs and recent avalanches.

    (2/22/2024)

    Fresh wet loose avalanche on the south side of Panorama Point at 6400'.

    Photo: Ryan Cupp

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Some locations in West South saw enough recent snow and wind that slab avalanches are still possible at upper and mid-elevations. A skier-triggered slab avalanche was reported from the Crystal Backcountry on a very steep, wind-loaded slope (photo in gallery). More are probably out there in similar terrain but should also be stubborn to trigger on Friday after another day to bond. 

    Track the depth and stiffness of new snow layers as you gain elevation. Visual clues can also help you identify areas with thicker slabs. Hand shears and test slopes can help you gauge slab reactivity.  When in doubt just use lower-angled terrain to get around steep, wind-loaded start zones.

    (12/23/2023)

    Textured snow surfaces can help identify areas where wind slabs could be hiding.

    Photo: Matt Primomo

Avalanche Discussion

An NWAC Forecast team in White Pass found limited avalanche danger on Thursday. Small wind-loaded pockets would produce some cracking but didn’t have the size or reactivity to produce slab avalanches. Solar aspects warmed to the point of producing rollerballs but not enough for wet avalanches. Good riding conditions were found on most aspects. The sun had more of an impact around Paradise where a handful of wet avalanches were observed on solar aspects. 

Other than avalanche observations, the big take home point from Thursday is that a weak snow structure still exists in some areas of West South. Whether it’s facets over the early February Crust, buried surface hoar or any other layer interface where weak snow grains come into play, the fact is weak structure is still out there and could produce bigger avalanches with bigger storms. Sometimes this sort of layering setup goes away, and sometimes, it doesn’t. Either way, savvy backcountry users know it pays to anticipate factors that could create real hazards rather than be surprised by them.

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