Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
Voir sur la carte

Danger d’avalanche

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

Points saillants

Forecast Update: A foot of heavy, denser snowfall combined with moderate winds has created dangerous slabs at all elevations of Mt Hood. Drifting will create larger slabs on wind loaded slopes that will be reactive to human trigger. Avoid all open slopes steeper than 35 degrees, giving extra buffer to wind loaded aspects.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2

    Update: Heavy snowfall Thursday night added plenty of snow for moderate W and WNW winds to blow around. This will create the potential for large and reactive slabs at middle and upper elevations with smaller pockets below treeline. You can trigger wind slab on any open slope steeper than 35 degrees. Avoid slopes with active drifting, under freshly formed and growing cornices, or where you find wind-stiffened snow.

    Keep in mind that Friday brings a twist as we flip from a prevailing E-SE wind to W or WNW winds, so there could be a variety of loading patterns in the terrain. Be wary of triggering shallow wind slabs at lower elevations or in terrain you'd usually consider "sheltered".  Don't get caught off-guard by a shallow wind slab on open slopes at lower elevations or even in steep treed terrain.  Getting raked through trees, rocks or other hazards will amplify the consequences of even a small avalanche.    

    Shooting cracks in freshly drifted snow on Pea Gravel Ridge Thursday.  Shallow wind slabs (3-6") were easy to trigger on lee slopes.  Wind slabs will grow significantly larger on Friday.

    Photo: Joe Dellaporta

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–1.5

    Storm slabs will be reactive in wind-sheltered terrain. Storm totals will be in the 12-15" range, but the new denser snow overlies lower-density old snow in sheltered terrain. Reactivity at the new/old interface or within the storm snow can be identified on quick pits or test slopes. Shooting cracks also confirm the problem. Avoid all steep, open slopes greater than 35 degrees.

    Example: Shooting cracks are an obvious sign of instability and warn you to avoid steep slopes. 

    Photo: Josh Lipkowitz

Avalanche Discussion

Thursday night brought heavy snowfall and moderate ridgeline winds by Friday morning, bringing storm totals up to 1 ft, following a few inches of snow that fell on Thursday with variable winds across the mountain.  At the Mt Hood Meadows ski area on Thursday, E-SE winds weren't as strong as other areas early in the day and eventually shifted to the SW in the afternoon.  An NWAC forecaster on Pea Gravel Ridge found shallow but easy-to-trigger wind slabs below the treeline on E-NE aspects.  On other parts of the mountain, strong Easterlies were reported at theTimberline (gusts into the 40s) and Ski Bowl (gusts into the mid 50s) weather stations.  

The January Drought Layer (JDL)  has been a prominent upper snowpack marker and a popular topic of conservation in our backcountry community these past weeks. You can dig down 2-3 ft and find this weak, sugary snow in most locations around Mt Hood. However, we have typically found it to be weakest on N-E aspects at lower and middle elevations. While we haven't seen any confirmed avalanches on it, it is worth tracking, especially if you head into more data-sparse areas like the north side of Mt Hood or further east near Lookout Mountain. Across the Columbia River and in the West and East South zones, we have seen propagating test scores, whumpfs, and a few avalanches.

Régions couvertes